BIOL 1470 Conservation Biology Final Study Guide

Those marked with asterisks are very important

Midterm Answers from 2024: Keep in mind that these are not Dov approved, these are just the answers that I got!

Explain the differences between the terms alien, introduced and invasive:

• Alien suggests that a species is present in a range where it is non-native.

• Introduced suggests that a species has directly or indirectly been introduced to an environment by humans.

• Invasive suggests that a species has been introduced to a non-native range and is leading to damaging consequences.

An “Individualist Perspective” is the basis for:

• c) Protecting individual organism

According to the lecture readings, biodiversity includes which of the following: 

• d) species, genetic and ecological diversity, 

Provide an argument that explains why climate alone is unlikely to have been the cause of the megafauna extinction event in Australia:

• Climate change alone is unlikely to have been the cause of the megafauna extinction event in Australia as Australia already experienced the forces of climate change during the Pleistocene and did not experience megafaunal extinction then. However, it was only upon the immigration and introduction of humans to Australia that megafauna went extinct. This pattern has been observed generally, with megafaunal extinction occurring as a result of human migration through Beringia into the Americas, with megafaunal bird extinction occurring upon human migration to Madagascar, and with the extinction of the megafaunal Moa upon the migration of humans to New Zealand. Likewise, in lecture 4 states that upon human arrival 50,000 years ago, this was period of time was relatively stable climatically.

If species survived repeated climate change during the Pleistocene, then why might they be at risk from climate change over the next century – provide two reasons:

1. The presence of humans and urbanization has created historically absent physical barriers to dispersal, putting limitations on a species ability to adjust and respond to climate change.

2. Although a species may have survived climate change, its population may now be too small and effectively bottlenecked by climate change. This can prevent a species from having a large enough population to replenish itself, with the consequences of allee effects possibly leading to extinction.

Martin, in his 1973 Overkill Hypothesis article, explains which of the following regarding human  population expansion in the Americas: 

• d) None of the above

Describe the approximate number of native species that have been documented to go extinct  as a consequence of climate change over the past century:

• There have roughly been 5 native species that have been documented to go extinct as a consequence of climate change over the past century. This is due to the fact that species extinction is typically resultant of various compounding factors, making it difficult to attribute climate change as a sole contributor to a species extinction.

Which state is likely to have the highest total number of plant species? 

• A) Texas

According to the lecture readings, what threat or threats are most common for endangered species: 

• a) Habitat destruction,

Provide a definition for “extinction debt”:

• Extinction debt is the process by which changes in environmental conditions make it so that, despite a species currently having extant populations, conditions have been altered so dramatically to the point that it is not possible for the species to perpetuate its population. This implies that despite efforts to conserve species, extinction debt will eventually go extinct. 

Why did NY City decide against building a water filtration plant, what actions did they take  instead?:

• NY City decided against building a water filtration plant because they found that the costs to not only build the plant, which would be around $6 billion, as well as annual maintenance of $500 million, would be much too costly. Instead, they chose to address the environmental causes that necessitated the water filtration plant, investing a smaller sum of $600 million into restoring the Catskills Watershed, effectively solving their water filtration plant in an ecological-minded and cheaper manner.

What is the “roadless area rule” and what is its relevance to conservation?:

• The Roadless Area Rule is a rule implemented under the Clinton Administration by the U.S. Forest Services that requires that 1/3 of all federally protected land cannot have roads constructed on them. This is relevant to conservation as this means that the ecological damage of road building, as well as the capacity to deforest further through increased means of transportation for timber work in forests, is effectively reduced, allowing for larger, more in-tact land reserves that are not damaged by habitat fragmentation.

Identify the species likely to have the largest minimum dynamic area: 

• b) golden eagle

Describe how the number of species has changed on average by filling in “increased”,  “decreased” or “no net change”:

• Plants on islands over the past 200 years: increased

• Plants in local patches of habitat on continents in the past 50 years: decreased

• Birds on islands in the last 500 years: no net change

• Freshwater mollusks in North America in the past 500 years: decreased

What treatment for scurvy would you prefer (assuming you wanted to live) if you were on a long  ocean-going vessel in the 1700s?  

• Lemons

Label each axis. In the context of this figure, describe two reasons why fragmentation of a  mainland area will lead to species loss?:

• X-axis = Log Area Size

• Y-axis = Log Species richness

• Fragmentation of mainland area will lead to species loss because:

  • 1.) There is a negative relationship between species richness and area, with a decrease in land area resulting in a smaller capacity for species richness.

  • 2.) It is almost always the case that fragmented habitats, such as islands, do not have comparable species richness compared to mainland of the same area. This means that the act of fragmenting a habitat in and of itself leads to net species loss compared to if the land was still part of the mainland.

Circle the species likely to have the smallest minimum viable population:

• e) house mouse

Provide one example of a taxonomic group that does not show the typical latitudinal gradient in diversity?:

• Pine trees do not follow the typical latitudinal gradient: there tends to be more trees on the East coast than the West coast.

Place the Miocene, Pliocene and Pleistocene in correct chronological order: 

• Oldest: Miocene

• Middle: Pliocene

• Youngest: Pleistocene

Describe the factors that led to the extinction of the Chinese River Dolphin. (2pts) 

• The Chinese River Dolphin was: over-exploited by humans for food, got caught as bycatch and entangled in fishing gear, presence of boats and ships led to damaging/fatal collisions, water pollution, habitat loss, noise pollution, all lead to the death of the Chinese River Dolphin. Effectively, the unintended consequences of human behavior led to the extinction of the Chinese River Dolphin.

Circle the places (for each comparison) that have higher absolute numbers of non-native species: 

• 1) Birds in Hawaii or North America, 

• 2) plants in New Zealand or California, 

• 3) mammals in Michigan or Alabama

List two classes/types of evidence that Shaffer believes could be used to determine minimum viable population sizes:

• Biogeographic Patterns

• Genetic Considerations

Is organic farming good for biodiversity? Defend your answer:

• I believe that organic farming is good for biodiversity as it limits the introduction of pesticides and foreign chemical agents, prevents the homogenization of species that comes as a result of intensive monocultural crop planting, and preserves a more natural landscape that is conducive to native species thriving.

What’s the difference between “population size” and “effective population size” and what sort  of factors lead to these differences?

• Population size is the number of individuals in a population, while effective population size is the number of individuals that are contributing to the gene pool of the next generation. The factors that lead to these differences are imbalanced sex mating ratios as is the case in sea lions, the susceptibility of small populations to skewed sex ratios, as well as variation in reproductive success.

How much colder (in degrees Celsius) was the global mean average temperature during  the last glacial maximum (ca. 20,000 years ago) relative to temperatures 100 years ago:  

• D, 5 degrees cooler.

Draw a figure below that indicates the relative size and placement of the realized, fundamental  and tolerance niche of a species, relative to mean annual precipitation and mean annual  temperature. Be sure to assign specific quantitative values to the axes. Assume that the species  cannot shift its range or evolve quickly. Assume further that it lives on land in a relatively flat area of broad geographic extent. Describe the severity and timing of extinction risk for this species by  2100 if by that time it warms by 4 degrees, but precipitation levels remain unchanged. (3pts) 

• The realized niche is smaller than the fundamental niche and fits within it. The fundamental niche is much larger than the realized niche but is still smaller than the tolerance niche. The realized and fundamental niche both fit within the tolerance niche.

• If by 2100, the Earth warms by 4 degrees but precipitation levels remain unchanged, it is likely that there will be a high severity of risk. Given that the species cannot shift its range, it will not be able to move to an environment that is within its fundamental niche. Likewise, given that the terrain is flat, there will be no elevation stratification such that the species can just increase in elevation to get to cooler climates. The species may be able to tolerate some change in mean temperature, but if this change in temperature falls outside of its tolerance niche, it will not be able to sustain the population and will likely succumb to extinction.

Final Answers from 2024: Keep in mind that these are not Dov approved, these are just the answers that I got!

Under what circumstances would a species be classified as being “neonative”? 1pt 

• A species would be classified as being neonative if it has expanded geographically beyond its native range and now has established populations due to human-induced changes of the biophysical environment, but not as a result of direct movement by human agency, intentional or unintentional, or to the creation of dispersal corridors such as canals, roads, pipelines, or tunnels.

Which taxonomic group is currently at the greatest extinction threat from infectious diseases? (1pt) – a) plants, b) invertebrates, c) birds, d) mammals, e) amphibians, f) reptiles, g) all these groups have roughly equal risks from infectious diseases 

• e) Amphibians

Ancient China had native populations of which of the following animals: (1pt) a) Zebra, b) Rhinoceros, c) Giraffe, d) Hippopotamus, e) All of the above, f) none of the above 

• b) Rhinoceros

Based on the film “The Wild Parrots of Telegraph Hill”, how many species of parrots (excluding any consideration of hybrid species) live on Telegraph Hill? (1pt) - a) four, b) six, c) seven, d) ten, e) none of the above 

• e) none of the above

What group of organisms are being represented in this figure? (1pt)

• Epiphytes
  

An “accidental” species is one that: (1pt) a) Arrives under its own power to a geographic locality outside its typical, native distribution b) Is created unexpectedly by a hybridization event between two closely related species c) Is one that is unintentionally threatened by indirect human actions (such as bycatch from fisheries production) d) All of the above e) None of the above 

• a) Arrives under its own power to a geographic locality outside its typical, native distribution

Briefly describe the dispersal experiment conducted with birds in the Panama canal and describe its relevance for understanding species distributions in the region (1.5pts): 

• Following the draining of the Panama Canal, habitat fragmentation disrupted the natural range/distribution of bird species in Panama. Studies were conducted to see how dispersal limitations, i.e. a bird’s ability to fly, impacted distribution patterns. Birds were collected, released over water, and were tracked to see how far they were able to fly and whether or not they could reach land. This was relevant as this dispersal experiment revealed that dispersal ability strongly influences patterns of distribution, and that intermediate fliers are often responsible for expanding species distributions.

List three distinct dispersal syndromes: (1.5pts) 

1. Water Dispersal Syndrome

2. Wind Dispersal Syndrome

3. Megafauna Dispersal Syndrome

Give 1 example of ex situ conservation (1pt) 

• Collecting species from the wild and housing them in Zoos to promote breeding and protect at risk populations.

What is autopolyploid speciation? (1pt) 

• Autopolyploid speciation is the process by which a new species forms when an individual organism ends up with extra sets of chromosomes from the same species. The new species is reproductively isolated from the original population, resulting in the new species.

  • This often occurs in plants.

Hybridization: (1.5pts) a) Reduces the total number of species b) Increases the total number of species c) Can increase or decrease the number of species d) Is an important process for many reasons, but has no impact on the number of species

• c) Can increase or decrease the number of species

  • Think of the Grey Duck and Mallard hybridization. In this case, a new hybrid species was formed, resulting in three species total, however, hybridization eventually resulted in the near extirpation of Grey Duck populations.

In attempting to maximize conservation impacts, while minimizing the total amount of area placed into reserves, what are the principal factors used in deciding how big individual marine reserves should be and how far apart they should be spaced from each other? (2pts) 

• The principal factors used in deciding how big individual marine reserves should be and how far apart they should be spaced from each other is:

  • The marine reserve should be large enough to protect and maintain viable populations.

  • The marine reserves should be close enough together that larval organisms can disperse and adults can move between protected areas, promoting connectivity.

Why are there “win-win” opportunities for meeting conservation and fisheries goals? (1pt) 

• It is possible to protect species without conserving entire coastlines and areas used for fisheries. For example, it is possible to conserve 40% of coastlines while protecting nearly 100% of marine species, allowing for fishing and commercial activity while meeting the goals of conservation. Overall, this protects biodiversity, biomass, and allows for sustained populations for fisheries.

To maximize the number of species protected, a single large reserve will be most effective (in comparison to several small reserves) under which of the following circumstances: (1pt) a) Species’ distributions are randomly distributed across a region b) Species have small body sizes c) Species are threatened by invasive pathogens d) All of the above e) None of the above 

• a) Species’ distributions are randomly distributed across a region 

Why might a local hotspot approach to allocating areas as reserves not be a good strategy for maximizing species preservation at landscape scales? (1pt) 

• A local hotspot approach to allocating areas as reserves may not be a good strategy for maximizing species preservation at landscape scales because it can obscure the need to protect rare or endangered species that are not present within a local hotspot. Likewise, this approach may not take into account areas with high turnover (beta diversity) which are also important for preserving biodiversity at local and landscape scales.

Indicate the scenario or scenarios below for which the demographic and contagion hypotheses produce identical patterns of range collapse: (1pt) – A contagion is introduced along one edge of a range and that edge is also the one with largest population sizes– A contagion is introduced along one edge of a range and that edge is also the one with the smallest population sizes– A contagion is introduced to the center of a range and the species shows an abundant center distribution– A contagion is introduced to the center of a range and the species has populations across its range that all have similar sizes

• A contagion is introduced along one edge of a range and that edge is also the one with the smallest population sizes

Pinsky et al. 2020, in the context of climate change, argues that marine species: (1pt) a) have less of a thermal safety margin/buffer than terrestrial species, b) have better dispersal ability than terrestrial species c) have a better capacity to evolve in place than terrestrial species d) all of the above e) “a” and “b” f) none of the above 

• e) “a” and “b”

The “dilution effect” describes: (1pt) a) The loss of vitality that occurs in small populations as genetic diversity is lost, b) The loss of ecological cohesion that occurs as an increasing number of non-native species are added to historic ecosystems, c) The economic losses that occur as ecosystems are degraded and ecosystem services are impaired, d) None of the above 

• d) None of the above
  

What is demographic stochasticity and how is it relevant to conservation? (1pt). 

• Demographic stochasticity are the random fluctuations that a population’s demographic can be susceptible to, whether it be random fluctuations in the gender ratio of a population, in fertility rates, etc. This is relevant to conservation because, especially in small populations, demographic stochasticity can make populations vulnerable to extinction, despite environmental and biotic stability.

Over the past 200 years (on average) diversity has increased: (1.5pts) a) For plants on islands b) For fishes on islands c) For mammals on islands d) All of the above e) None of the above 

• a) For plants on islands

How much colder (in degrees Celsius) was the global mean average temperature during the last glacial maximum (ca. 20,000 years ago) than preindustrial temperatures: (1pt) a) 20 degrees cooler, b) 15 degrees cooler, c) 10 degrees cooler, or d) 5 degrees cooler. 

• d) 5 degrees cooler

Why might regional increases in biodiversity be beneficial for human well-being, and reciprocally why might they be detrimental to conservation goals? (2pts) 

• Regional increases in biodiversity can be beneficial for human well-being by introducing species that provide some relational or instrumental benefit to human beings. For example, introducing a species of tree to a novel environment can help prevent soil erosion and promote nutrient cycling. However, this can be detrimental to conservation goals if these species are non-native and eventually become problematic. Likewise, increasing biodiversity by introducing species that have not been historically present undermines many conservation goals of conserving historical conditions of environments, putting native species relationships at risk and disrupting native biodiversity.
  

Why are ‘option values’ so difficult to calculate? (1pt) 

• Option values are so difficult to calculate because they represent the value of preserving the possibility of using a resource or species in the future without being completely certain of the benefits, making it inherently difficult to quantify costs or benefits.

What two strategies do you think are most important for conservation over the next 100 years? Defend your answer (2pts) 

• The two strategies that are most important for conservation over the next 100 years are:

  • Minimizing and preventing the impacts of climate change: Climate change introduces environmental stochasticity and unpredictability, making it difficult for species to maintain populations, track suitable habitats, or adapt in place. By mitigating climate change, we can reduce extreme events, temperature shifts, and habitat loss, giving species a better chance to survive and maintain ecosystem functions.

  • Reducing habitat fragmentation and promoting larger, connected reserves: Large, connected habitats allow species to move, disperse, and maintain viable populations according to the Species-Area Relationship, which is essential in the face of environmental change. Connectivity also supports genetic diversity and ecosystem resilience, helping species adapt to new stressors over time.

Which species should have the smallest ‘minimum dynamic area’? (1pt) a) an oak tree, b) a sunflower species, c) a rabbit, or d) a mountain lion 

• a) Sunflower species

Which of the following statements are most likely true (note that none of these may be true, all of them may be true, or some proportion may be true): (2pts) a) Passenger pigeons went extinct primarily due to avian pox and malaria b) Unlike North America, in Australia most megafauna went extinct because of climate change c) House cats have contributed to bird extinctions on islands d) ‘neonatives’ is a term for species newly created by hybridization e) There is general agreement that cattle egrets are non-native in South America f) None of the above

• c) House cats have contributed to bird extinctions on islands

Three classes of ethical values for protecting species (L.2)

• Relational: nature has value with respect to culture, identity, recreation, hunting/fishing, etc. 

• Instrumental: 

  • Provisioning: materials, materials, materials!

  • Regulatory: clean water and erosion control, etc.

• Intrinsic: animal welfare/rights, ecological and evolutionary process, species diversity, etc.

  • Ethical Perspectives also include:

    • Individualist

    • Holistic

Preservationism vs. Conservationism (L.2)

• Preservationist: habitat should be left untouched for human needs/gains.

• Conservationist: habitat should be managed for human needs and gains.

• Example:

  • The Hetch Hetchy Dam (1897): Generates electricity for residents of San Fran. but obstructs natural environment processes.

***Latitudinal Gradient of Biodiversity (L.3)

• As you move towards the tropics, biodiversity increases across latitudinal bands.

• Many have argued that this pattern is universally true for all large taxonomic groups. However, there are exceptions.

***Species-Area Relationship (Curvilinear) (L.3)

The bigger the area, the more species there are.

• The more local species, the more regional species.

• ***A big island has as many species as the same area of land on mainland. A small island is species poor compared to the same size of land on mainland.***

  • S = CA^Z

    • Mainland > Island > Isolated Islands

Limitations: only works well at predicting extinctions in small areas.

***Alpha, Beta, and Gamma Diversity (L.3)

• Alpha: some small local sample of diversity.

• Beta: turnover diversity between two different habitats.

• Gamma: regional diversity.

***Types of Environmental Niches (L.3)

• Realized niche – the conditions/place where a species ACTUALLY occurs.

• Fundamental niche – the conditions in which a species could occur in the absence of limiting factors (competition, dispersal limitation, etc.). Encompasses the realized niche.

  • Realized and fundamental niches are places where the species can persist INDEFINITELY.

• Tolerance Niche – places where species can survive but cannot persist indefinitely.

Constraints on Niches (L.3)

• Abiotic variables: rain, temp., salinity, nutrient availability, etc.

• Biotic variables: competition, predation, mutualism, etc.

  • Dispersal limitation: species can’t reasonably disperse to some areas due to physical limitations or lack of coevolved dispersers.

Ecological Zonation and Range Boundaries (L.3)

Ecological Zonation: different a/biotic factors lead to distinct community gradients, or zonal patterns.

• Range boundaries can occur at local, regional, and global scales, limiting a species from extending its range.

Case Study - Trans(plant) Experiments Show that for Range Boundaries in swamp brush:

• Typha latifolia - superior competitor; lower boundary is set by lack of light availability.

• Typha angustifolia - upper boundary is set by competition with T. latifolia.

  • Tradeoff between competitive ability and stress tolerance.

***A Calendar for the Earth (L.4)

The Earth is ca. 4.6 billion years old

Epochs and Periods:

• Quaternary Period (2.6 million years ago to now): The most recent geological period; repeated ice ages and the global spread of humans.

• Pleistocene Epoch (2.6 million - 11,000 years ago): Megafauna went extinct when humans crossed BERINGIA around 12,000 years ago. The end of the Pleistocene was the LAST ICE AGE.

  • ***Beginning of Pleistocene, glacial cycles have a 41,000-year cycle and shift to 100,000-year cycles around 1 million years ago.***

Ascension Island as a Case Study (L.4)

Ascension Island formed relatively recently (<20 mya, with active volcanoes) on a mid-oceanic ridge. Ascension is species poor, given that it is:

1. Young: less time for species to colonize.

2. Isolated: hard for species to reach it.

3. Small: limited habitat and resources.

****Conservation Theory builds from patterns on islands and using islands as models.

Glacial Periods and Species Distribution (L.4)

Effects of Ice Sheets and Glaciers:

1. Few to no species have realized niches on ice sheets.

2. Sea level and subsequent impact on land bridge creation/destruction.

***At the last glacial maximum, the sea-level was 440 feet lower than now.***

• Beringia, the land bridge connecting Russia and Alaska, was MASSIVE. Warmer conditions due to ocean circulation patterns contributed to Beringia being relatively productive.

Non-Analogs and Graham et al.: (L.4)

Graham (1996): Non-analog communities

• Many late Pleistocene communities do not have modern analogs, given the various climate changes of the Quaternary Period.

***Paul Martin and the Overkill Hypothesis (1973) (L.4)

Megafauna were preferentially hunted and driven to extinction by humans.

• Megafauna did not go extinct before human impacts, whether it was at the start of new climatic regimes (beginning of Pleistocene, shift to 100k year cycle), nor when there were barriers to species dispersal.

• This extinction pattern has been recreated whenever humans arrive to a region not previously occupied where megafauna are not adapted to human behavior.

  • i.e. Mauri extinction of the Moa chicken in New Zealand.

***How much will the Earth warm up by 2100? (L.5)

Up to 5-6 degrees Celcius by 2100.

Species Range Shifts (L.5)

Range shifts typically occur as range contractions: Quiver Tree – Contracting Range:

• Range shifts of observed mobile species average 6.1km poleward

• Most species probably aren’t moving poleward at all, or only very slightly:

  • True with trees and species in the tropics

Rapid Range Shifts of Species Associated with High Levels of Climate Warning:

• Best estimates 16.9 km/decade.

***How Many Species Have Gone Extinct from Climate Change in the Past Century? (L.6)

Like 5

• Various local populations extirpations (local extinctions) are attributed to climate change.

• Extinction is often driven by multiple factors, not JUST climate change difficult.

How many extinctions from climate change are forecast to occur over the next century? (L.6)

Over A MILLION - in reality:

• Mid-range climate-warming scenarios for 2050 project that 15–37% of species are ‘committed to extinction’ (on the path to extinction).

Sax et al. Transplant estimates:

• By 2100 we expect extinctions among 5-36% of study species and extirpations (local extinctions) among 10-50% of populations.

Why might species go extinct if they’ve previously survived climate change? (L.6)

1. Reduced population sizes

2. Barriers to dispersal

3. Abiotic conditions will be different (climate and ocean acidity)

Problems with Climate Niche Models (L.7)

Climate-Niche Model: predict where species could live in the future based on their current climate tolerances.

1. We don’t know how in/accurate they are.

2. They make no predictions for no-analog climates of novel ecosystem interactions.

3. Many species are dispersal-limited (and can’t reach suitable places/conditions)

   1. Nevertheless, this imperfect approach is the best available with limited data – it needs improvement

Solutions to Climate Niche Model (L.7)

One potential solution is comparing climate-niche models in native and naturalized ranges.

• Early and Sax (2014): revealed two types of error discovered for plants native to Europe:

  • 1.) areas of predicted occupation that are NOT occupied.

  • 2.) areas that are occupied but NOT predicted to be.

Perret et al. 2019 — Niche Expansion (L.7)

“Niche expansion” is largest in species with small native niche/range size.

• Smaller niche = harder to estimate the environments that a species COULD occur in.

Anatomy of a Niche Syndrome (L.7)

Syndromes of the size/position of the realized niche with respect to the fundamental and tolerance niches.

• Syndrome 1: Narrow breadth and is tightly nested between realized, fundamental, and tolerance niches.

  • As climate warms, the realized distribution shifts beyond all niche components (unless it can rapidly evolve or shift its geographic distribution).

• Syndrome 2: Cold-skewed realized niche vs. Warm-skewed realized niche vs. Cold-skewed fundamental & warm-skewed tolerance niche

• Cold-Skewed Risk of Warming if realized limit set by:

  • 1. Dispersal - no/low risk

  • 2. Weak biotic interactions - delayed risk

  • 3. Strong biotic interactions - immediate risk

• Warm-Skewed Risk: immediate

• Cold-Skewed Fundamental + Warm-Skewed Risk if realized limit set by:

  • 1. Short-lived - immediate

  • 2. Long-lived - delayed

Summary of Hollenback and Sax (2024)

Main Findings:

• Low levels of temp. rise (1-2^o) will not lead to many epiphyte extinctions. High levels of temp. rise (3+) will lead to extinction.

• Low emissions protect epiphytes, while moderately high emissions lead to loss of 5-36% of species and of 10-55% of populations.

Tropical Mountains:

• Most biodiverse regions on Earth. High risk of extinction from climate change.

• Shift of species uphill is a common response to climate change.

Epiphytes: vascular plants that grow on trees, not the ground.

• Narrow elevation ranges and sensitivity to drought are risk factors for epiphytes.

******Principal Threats of Species Extinction (L.8)

I. Over-exploitation: i.e. Passenger Pigeon

II. Habitat destruction: Single most important factor

III. Extinction from exotic species:

• A.) Hybridization/interspecies breeding - Grey Ducks & Mallards

• B.) Predation - competition does not directly lead to extinction, predation does.

IV. Infectious disease: Fungal infectious diseases are incredibly dangerous.

V. Incidental human Effects: Byproduct of human activity

• Freshwater mussel biodiversity in American South has reduced due to sediment in water.

• Chinese River Dolphin:

  • Hunted by humans for food, entanglement in fishing gear, collisions with boats and ships, water pollution, habitat loss, noise pollution, all lead to DEATH.

VI. Climate change: hard to definitively say.

***How Many Documented Extinctions Have There Been in the Last 500 Years? (L.8)

IUCN (2022 list):

• 124 plant extinctions

• 778 animal extinctions

  • There are probably 3000 well-documented species extinctions over the last 500 years:

• Minimum estimate of extinction – lower “bookend.”

***Species Vulnerability to Extinction (L.8)

Species on islands (or isolated habitats) with small ranges:

• e.g., ground nesting birds, ‘naïve’ species: megafauna

Insular environments:

• An environment that is rare relative to the surrounding landscape.

• Species in RIVERS are particularly vulnerable in insular habitats (i.e. freshwater mussels, crayfish, amphibians, fish, plants).

Species with 1 or a few populations:

• e.g. Devil’s Hole Pup Fish

Species-Area Relationships, Habitat Loss, and Extinction (L.8)

In the context of species-area relationships, species extinction is caused by:

• 1.) Isolation

• 2.) Loss of Area

  • 3.) Habitat Fragmentation = isolation AND loss of area.

    • Insular habitats lead to extinction***

***Potential Flaws in the Species-Area Relationship (L.8)

• 1.) Small land reserves may protect “hot spots of diversity” so small area doesn’t always = lower richness.

• 2.) Species with broad geographic ranges may have lower vulnerability to extinction.

• 3.) All species may not actually be removed by the development of areas.

  • What if 1/3 of an island is lost but no species occupy that area? What if they do?

***Red Queen Hypothesis (Van Valen) (L.8.)

Many view evolution as an arms race. Species continuously evolve all the while, predators/prey evolve too. The ‘goal’ is to just maintain species presence, not necessarily to evolve so as to massively expand presence.

Islands/Isolated Areas are Hotspots of Endemic Biodiversity - True or False? (L.8)

TRUE TRUE TRUE TRUE: this occurs because unique species evolve there and persist despite extinctions elsewhere.

Examples include:

• (Evolve there): Dodo Bird, Honeycreepers

• (Only exist there): Marsupials, Tuatara

Defining “Exotic Species” (L.9)

Exotic Species: species which as a consequence of human actions, occur in regions where they were absent historically.

• Non-native = alien = exotic = non-indigenous

  • Introduced: a population transported by humans.

  • Naturalized: a self-sustaining population(s).

  • Invasive: a population that harms native ecosystems.

****Reverse Pyramid of Probability, 10% Rule (L.9)

For every 10,000 species introduced, 1,000 species become naturalized, 100 species become invasive, and 10 of those become “Ecological VILLAINS.”

Ecological Villains:

• Chestnut Blight

• South African Ice plant

• Kudzu

• European Rabbit

  • ***It often takes multiple instances of introduction for a species to naturalize.

  • This was the case for Starlings and House Sparrows.

***Exotic Species Range Expansion (L.9)

• Spread over time follows a sigmoidal (S-shaped) growth pattern relative to range expansion.

• Exotics can spread rapidly across continents:

  • Starling: introduced in 1896 to Central Park, spread more or less everywhere in North America.

    • 12 failed introduction attempts prior to 1896.

  • House Sparrow: 1852, introduced to Central Park.

Problems with Native vs. Exotic Distinctions (L.9)

Native-Range Expansion vs. Exotic Invader?:

• Cattle Egrets in N. and S. America:

  • Humans altered landscape for agricultural.

  • Cattle egrets were blown over from Africa and found the altered environment to be suitable, naturalizing themselves.

• Reintroduced Species vs. Exotic Invader:

  • Horses are not native in North America; megafaunal horse went extinct in North America during the Pleistocene. Are they invasive?

***Generalities on Extinctions (L.9)

Generality #1:

• Most extinctions are on ISLANDS:

Generality #2:

• Most extinctions are caused by ‘Predation.’

Generality #3:

• Higher Proportions of Exotics on Islands; it is harder for Exotics to establish themselves where there is already lots of preexisting diversity, like mainland:

  • 22 naturalized birds in North America vs. 55 in Hawaii.

  • 1500 naturalized plants in California vs 2000 in New Zealand.

    • There are FEW exotics in the tropics or the poles. There are less birds and mammals towards the equator.

***Evolutionary Imbalance Hypothesis (EIH) (L.9)

History of intense competition and environmental change evolves more competitive and adaptable species, giving them an advantage when introduced to new regions. 

• This theory incorporates Darwin’s framework of evolution.

Implications:

• If invaders are more finely tuned by natural selection, they may displace and cause the extinction of native species.

• The enhanced efficiency of invaders may increase rates of productivity and nutrient cycling in invaded ecosystems.

***Native vs. Exotic Species Relationship at Local Scales (L.10)

Sax 2002 found that Native and Exotic richness are positively correlated, even at local scales. Why?:

• Site quality! If a local plot is suitable for a native species, it will be suitable for an exotic species. If a local plot is NOT suitable for a native species, it will NOT be suitable for an exotic species.

****Sax study using Islands as models of the impacts of exotics (L.10)

Species Richness on Islands:

• Plants: increased consistently on Oceanic Islands: most have twice as many plants as they used to have.

  • Few natives have gone extinct and so many non-natives have been established.

• Freshwater Fishes: increased consistently on oceanic islands.

  • Brackish water fish evolved to be able to occupy freshwater landscapes. There are 5 native fish in Hawaii and over 40 fish that have been introduced.

• Birds: UNCHANGED, overall, the number of species has not changed very much.

  • There is a matching between the number of native birds that have gone extinct and the non-native birds that have been introduced.

Mean change in species richness:

• 307% > 104% > ~ 0%

• Fishes > Plants > Birds

***Change in Diversity at Regional Scales (L.10)

• Mammals: massively increased on islands, decreased on continental Mainlands.

• Freshwater Mollusks: fewer than there used to be

• Subtidal invertebrates (cryptogenic): we do NOT know

• Tropical Trees: fewer than there used to be

• Bacteria: we do NOT know

***Island Biogeography Theory (MacArthur & Wilson, 1963) (L.11)

The number of species is set by an equilibrium between rates of immigration and extinction.

***Relaxation (L.11)

“Relaxation,” or the process of species extinction following isolation:

• It takes time for species to go extinct and “Relax”:

  • Lizard species on islands in the Gulf of California

• The Process of Relaxation is not Random; some species are more likely to go extinct than others due to extinction debt.

***Viable Population and Minimum Viable Population (L.11)

Viable Population:

• A population that can perpetuate itself.

Minimum Viable Population:

• An estimate of the number of individuals needed to perpetuate a population.

  • ***Plants tend to have higher MVPs when they’re long-lived, slow-reproducing, but much lower when not, i.e. dandelions

***Schaffer - Minimum Viable Population (1981) (L.11)

Formal Definition:

• For any given species in any given habitat the MVP is the smallest isolated population having a 99% chance of remaining extant for 1000 years despite the foreseeable effects of demographic, environmental, and genetic stochasticity, and natural catastrophes.

  • Vertebrate MVPs may be ~7000 individuals.

  • Perennial plant MVPs may be ~2000 individuals.

  • Species with extremely variable population sizes may have much higher MVPs, e.g. 10,000 individuals.

***Minimum Dynamic Area (L.11)

Minimum Dynamic Area:

• Area of suitable habitat necessary for maintaining the minimum viable population

• Large animals will need larger area then small animals.

  • This explains why large mammals go extinct on small islands or reserves.

***Four Threats to Small Populations - LEND (L.11)

• 1. Loss of genetic variability

• 2. Environmental variation

• 3. Natural catastrophes

• 4. Demographic variation

Threat 1 - Loss of Genetic Variability (L.11)

Ne = Number of Breeding individuals in a population. Factors affecting Ne:

• 1. Unequal sex ratio

• 2. Variation in reproductive output

• 3. Population fluctuations and bottlenecks

• Founder Effects are bottlenecks on Ne.

  • Effective Population Size can be restored by mutations and immigration.

Consequences of Reduced Genetic Variability — Inbreeding Depression (L.11)

1. Inbreeding depression: higher mortality and lower fertility rates caused by inbreeding.

• An important caveat: Breeding with individuals that are too different can also be a problem:

  • Outbreeding depression – condition that results in extinction via hybridization.

2. Loss of evolutionary flexibility: not enough genetic variation for natural selection to handle changing environmental conditions.

Threat II – Demographic Stochasticity (L.11)

• 1. Variation in the number of offspring produced by small populations is risky.

• 2. Small populations have an increased chance of ending up with skewed sex ratios.

• 3. Allee Effects – added difficulties associated with small populations (e.g., hunting in packs, finding a mate)

Threat III — Environmental Stochasticity (L.11)

Random variation in biological or physical factors. Examples:

• Variation in the number of your predators or temp./rain.

Threat IV – Natural Catastrophes: Storms, floods, fires, (L.11)

Sudden, large-scale events can drastically reduce populations or alter habitats such that it is hard to maintain presence.

***Extinction Debt and Immigration Credit (L.11)

Extinction takes time (sometimes):

• Changes in environment create uninhabitable environments; the species remains in “extinction debt” until it goes extinct.

  • Some species may be doomed for loss, despite efforts to save them, due to Extinction Debt.

***Immigration Credit (L.11)

The number of species committed to immigration following a forcing event (i.e., a change in conditions).

Managing Invasive Species (L.12)

***Early detection and drastic measures are required to fully extirpate invasives.

Options for removal are local manual removal or regional biocontrol agents.

• Black Striped Mussel removal:

  • Copper sulphate and chlorine were added to the harbor, killing ALL marine life.

  • Natives were able to recolonize while the Black Striped Mussels were removed: no harm no foul.

• Snail Parasites: 

  • Volunteers in Cayucos, CA removed 1.6 million snails, lowering the density of hosts to such a low level that the parasite couldn’t persist.

• Feral Pig Removal: introduced mammals fundamentally alter island ecosystems

  • Successfully removed from Channel Islands by multi-million-dollar hunting efforts using helicopters and sniper rifles.

• Saint John’s Wart: 

  • Presence reduced by 97% following the introduction of leaf-feeding flea beetles.

***Reserve Locations and Roadless Area Rule (L.12)

Most protected land is controlled by the National Forest Service.

***Roadless Area Rule: placed 1/3 of Forest Service land off-limits to roads.

• Roads are necessary for deforestation and altering the wilderness; preventing road construction protects large, undisturbed habitats.

Biogeographic Ecotone (L.12)

Ecotone: the border between two ecosystem/habitat types. You experience an overlap of habitats and species presence at these local landscapes.

Critical Habitat and the Endangered Species Act (L.12)

• Critical habitat is a term in the ESA: geographic areas with features essential for the conservation of a threatened or endangered species; may require special management considerations or protection.

***Ecological Restoration (L.12)

Ecological restoration: assisting the recovery of an ecosystem that has been degraded by artificially emulating structure, function, diversity, & historic dynamics.

Often Part of Mitigation Efforts:

• To replace destroyed wetlands

• To replant areas that have been mined

• To cover landfills with native vegetation

This has come in the form of Rewilding, such as in the reintroduction of Wolves to Yellowstone, which:

• Reduced abundance of elk/large herbivores.

• Helped vegetation and beaver populations recover.

• Improved stream quality and reduced flood peaks.

Biofuels (L.13)

Biofuel: fuel made from plants (corn ethanol and vegetable/animal oils) and other organic matter.

• There is a curvilinear relationship between the percent of species protected and the percent of original area left unaltered by biofuel production.

Pros:

• Sustainable energy source, giving us energy independence from FFs.

Cons:

• Competes with food production, leading to an increase in food prices and to increased demand for agricultural land use.

  • When looking at a global economy, the consequences of biofuels all lead to DEFORESTATION.

• Converting land (deforesting/burning trees) to biofuel agriculture releases carbon into the atmosphere (which can be paid off).

Agricultural Intensification (L.13)

Agricultural Intensification: if you can intensify the efficiency of land use for agriculture, does that mean we conserve more land?

Rudel Paper:

• Theoretical Expectation: as yield of a crop increases, the price of that food should go down, and lead to a reduction in cultivated area.

  • Despite yields going up, more land was still being used for agriculture.

• The lack of land sparing was explained by geopolitical economics.

Case Study: New England Forest Rebound:

• Very little forest (close to 0%), mostly farmland in the 1700s

• As it became easier to farm in the Midwest, economics drove the rebound of natural forests in New England (close to 50%).

Are less intensively managed farms better at protecting biodiversity? (L.13)

YES, THEY ARE:

• There is evidence of more species on organic farms that are less intensively managed and more biofriendly than conventional farms.

Organic vs. Intensively Managed:

• Organic farms can nearly match conventional yields; however, this requires intense management and carefully cultured conditions for this to occur.

  • You’re getting at least 20-30% lower yields on organic farms vs conventional farms. This is a sacrifice necessary to protect biodiversity.

Land Sparing vs Land Sharing (L.13)

Land Sparing:

• Incredibly intensive agriculture on isolated plots of land. Higher yields mean less land needed, more spared.

Land Sharing:

• Less intensive, more biofriendly agriculture allows land to be shared between agricultural and natural practices.

  • Intensive agriculture that preserved more intact land while massively altering smaller plots of lands may be a better conversation strategy. However, there is no general consensus on this.

Winner and Loser Species:

• Some ‘winners’ do better as agriculture intensifies, while some only need a little bit of agriculture to do better.

• Some species do alright with some agriculture but then crash, while some crash with even the smallest amount of agriculture.

Freezing the Footprint of Food and Solutions for a Cultivated Planet (L.13)

Eight Food Wedges:

• 1. Genetics and plant breeding

• 2. Better practices

• 3. Efficiency through technology

• 4. Rehabilitating degraded land

• 5. Property rights

• 6. Waste reduction

• 7. Consuming more plant parts

• 8. Carbon

Solutions:

• 1. Close the yield gaps, use better technology.

• 2. Use resources more efficiently.

• 3. Shift diets and reduce waste.

Dispersal (L.14)

Dispersal: the arrival and survival of individuals relative to a disparate point-of-origin.

• 99.99% of individuals fall within modal dispersal distances. Characterized by curves:

  • Shorter tails: more individuals (propagules) remain close to point of origin.

  • Longer tails: more individuals reach greater distances from point of origin.

Dispersal Syndromes (L.14)

• Wind Dispersal:

  • Dandelion | Ferns | Tumbleweed

• Water Dispersal:

  • Coconuts and cranberries

• Megafauna Dispersal:

  • Osage Orange

• Bird and Mammal Dispersal:

  • Seeds have hooks to catch onto hair/fur/feathers

  • Squirrels and Birds move acorns

    • DUCKS: Ducks are important dispersers for seeds as they are larger, and seeds stay in their guts longer.

• Ant Dispersal:

  • Ants eat foods and move their seeds.

***Species can use more than one type of dispersal at once***

Dispersal Limitations and Climate Change (L.14)

Timing mismatches between dispersal methods and disperser responses to climate change:

• Most species moved by birds are not tracking migratory responses to climate change.

• Species reliant on dispersal cannot naturally expand their range in response to climate change.

Janzen-Connell Hypothesis: Seedling Dispersal Survival (L.14)***

• Seed mortality: highest closest to parent plant because of specialized predators (including soil pathogens).

  • Predators are near tree, bacteria/fungi specialized to eat seeds.

• Establishment: less likely further from parent plant because suitable abiotic conditions are less likely to occur.

• Recruitment of new individuals: peaks at some “intermediate” distance from the plant:

  • Goldilocks zone for sapling establishment that balances abiotic and biotic pressures.

Short-Scale vs. Long-Scale Dispersal (L.14)

Short: common

• Habitat corridors within networks of reserves allow for dispersal to higher elevations and latitudes

Long: rare

• Every terrestrial species in Hawaii has an ancestor that arrived via dispersal

Vagrants and Accidentals (L.14)

• Vagrants: species that occasionally appear outside their normal range due to unusual dispersal.

  • I.e. flamingos in Ohio and Rhode Island.

• Accidentals: species that rarely occur in a region outside their normal range, often due to storms, navigation errors, etc.

  • I.e. Stellar’s Sea Eagle: native to Japan, yet in 2020, one eagle flew to Alaska, Texas, New England and coastal Maine.

Range Dynamics and Shifting Ranges: Push and Pull - Inhabitable vs. Habitable (L.14)

Shifting Ranges are a product of two processes:

• 1) Population extirpations (deaths) because habitats are no longer suitable

  • I.e shifting North because warming kills Southern pops.

• 2) Dispersal to new places where new populations can be established

  • Push and pull between inhabitability and habitability

The Basics of Bird Range Maps (L.14)

Birds are very dynamic; many move/shift ranges throughout the year:

• Arctic Tern: seasonal migratory patterns allow these birds to enjoy two Summers every year.

• American Robin: some individuals are year-long residents, some migrate between Summer/Winter ranges.

How would you set up an experiment to test dispersal limitation in tropical birds? (L.14)

1. Catch them

2. See how far they can fly over open water (this is unethical asf)

3. Ask if distribution patterns are related to dispersal ability

The Panama Canal and Habitat Fragmentation (L.14)

The Panama Canal was drained, fragmenting habitats and disrupting natural bird distributions.

• Why didn’t some birds just fly the short distance to repopulate their island?

• 3 Study Species of bad flyers: birds were captured, let go above water, and were unable to fly past 300 meters.

• Showed that dispersal limitations strongly influence species distribution.

  • Example of habitat fragmentation as a dispersal limitation.

Marine Dispersal and Response to Climate Change (L.14)

Most marine species have a larval dispersal stage; larvae are blown far by ocean currents.

• Depending on how strong currents are, it can become impossible for marine organisms to maintain a population in one place.

West-Wind Drift:

• An organism from the tip of Africa or from the Southern parts of Australia and New Zealand can move in ocean currents between continents, even to the Americas.

Marine Species Response to Climate Change:

• Some marine species will respond to even a single warm year by moving hundreds of miles past their typical range.

  • Manatee range is typically in the vicinity of FL.

  • In 2023 one was seen in RI.

  • It died - this is the role of the accidental.

Limits to Marine Dispersal (L.14)

Some marine species have limited dispersal, like seaweed; rare long-distance dispersal events still occur.

Marine species run into limitations in shifting to higher latitudes:

• 1. Corals limited by sunlight

• 2. Species running out of continental habitat (e.g., in Australia)

• 3. Because of other factors, e.g. ocean acidification, overfishing, etc.

Marine Organism Fundamental Niches (L.14)

Most marine species have a realized niche that almost entirely fills in their entire fundamental niche. This is in stark contrast to terrestrial species' niche relationships.

• In the ocean, shifts at both range boundaries have been equally responsive, whereas on land, equatorial range boundaries have lagged in response to climate warming.

Novak et al 2021. Summary

Well-planned conservation translocations routinely yielded their intended benefits without producing unintended harm

Recommendations for improving conservation translocation success:

A. Better monitoring and ecological research

B. Use genetic data proactively:

• Identify suitable source populations.

C. Strengthen interdisciplinary collaboration

D. Improve regulatory frameworks:

• Create unified, adaptive national guidelines (e.g., modeled after IUCN, New Zealand, Scotland)

When negative outcomes occur, they are tied to non-conservation motives:

• The harmful cases (e.g., mongoose, rosy wolf snail, mosquitofish) were released for:

  • Agriculture | Pest control | Aesthetics | Sport hunting/fishing

• Only 1.4% (42 of 3,014) global biological control agents have caused ecosystem-level damage.

• All damaging releases occurred before the 1980s, before modern risk assessment and host-specificity protocols.

Traditional Conservation Strategies: RCEx (L.15)

• Reserves

• Corridors

• Ex Situ Conservation: sometimes it’s the only option left for saving a species:

  • Zoos

  • Aquariums: Birds > Mammals > Reptiles > Amphibians

  • Botanical Gardens - global Totals: 4 million individual plants | 80,000 species | 30% of the world’s total

California Condor and Ex-Situ Conservation (L.15)

Once spread across most of western and southern U.S., eventually all surviving wild individuals were caught and reared in captivity.

• From 22 to 289 individuals now breeding in wild again

• Massive minimum dynamic area, small minimum viable population.

  • Subject to changes in environmental conditions and human alterations.

Limitations/Difficulties of Ex-Situ Conservation (L.15)

• 1. Expensive

• 2. Population size (to prevent genetic drift)

• 3. Adaptation (to the captive conditions)

• 4. Learned skills (lose ‘culturally’ learned behavior)

• 5. Genetic variability (only represent limited portion of gene pool)

• 6. Continuity (continuous supply of funds)

• 7. Concentration (all your eggs in one basket)

• 8. Surplus animals (ethical issue of extra animals)

Reintroduction and Release Programs: RAI (L.15)

3 types of release programs:

• 1. Reintroduction:

  • Used to be somewhere, now it’s back

• 2. Augmentation:

  • Population dwindling, add new members to population

• 3. Introduction:

  • A. For conservation purposes (rare species) i.e. Translocations

  • B. For other purposes (exotic species) i.e. exotic introduction

Griffith 1989 - Probabilities of Success in:

• Highest in excellent quality habitat, core of historic range, wild-caught herbivores.

Examples of Reintroduction (L.15)

Guam rail (bird) – extinct in the wild:

• Brown tree snake decimated populations.

• Captive-breeding facilities in Guam and in 14 zoos in the US.

• From 1989-2007, 853 captive reared rails were released to mixed success.

Père David’s deer – extinct in the wild:

• The last wild animal was shot near the Yellow Sea in 1939

• Individuals in private deer collections in Europe in the 1800s were reintroduced to China in the 1980s.

Grey Wolf Recovery (L.15)

What is the native range of the grey wolf, Canis lupus? Is it endangered? Who knows:

• Extirpated range in North America vs. present range in Asia and Canada.

2013 - FWS proposed removing ESA protection from all US grey wolves. Delisted in some states and using the category of “non-essential experimental populations” in Wyoming:

• Non-essential experimental: individuals can be moved under certain circumstances.

• Essential experimental: species would be protected from translocation and movement.

  • By delisting all/parts of the US wolf population, it could concentrate its resources on the Mexican wolf subspecies.

The Mexican Grey Wolf (L.15)

The Mexican Grey Wolf – Canis lupus baileyi:

• The sub-species of mammals can be listed under the Endangered Species Act: in this case, the subspecies baileyi is protected under the Endangered Species Act.

Mexican Grey Wolf Reintroductions:

• Listed as endangered in 1976 | Reintroduction began in 1998

• Designated as a “nonessential experimental population” that includes provisions for removal of wolves that depredate livestock:

  • Wolves escaped the boundaries established by the F&WS and were killed by humans.

  • Wolves were removed and relocated.

Translocations (L.15)

Key Conservation Issues:

• 1. Effectiveness

• 2. Ethical Issues (i.e. exotic introductions)

• 3. Laws, rules, policies don’t exist

New Zealand:

• Many introduced mammals

• Many bird extinctions and many other taxa endangered

  • The translocation/movement of fauna and flora to small offshore islets allowed for the easy management/removal of endemic species and the rewilding of endangered species.

Rewilding in Mauritius and Tortoises (L.15)

Mauritius Coat of Arms for the Country: the native Dodo and the introduced deer.

• Mauritius had 2 endemic tortoise species: extinct 200 years ago

• In 2000, 18 adult and sub adult Giant Tortoises were released on an island to simulate the impact of browsers on the island’s vegetation.

Tortoise Rewilding: ongoing

• Minimum of 36 large tortoises extinct since Pleistocene

• 32 remaining extant worldwide

Managed Relocation (L.15)

= Assisted Migration = Assisted Colonization

• Reduce negative effects of climate change by moving to locations where likely to persist in the future.

Two Principal Motivations for Managed Relocation:

• 1. Prevent species extinctions:

  • Conducted by interest groups & scientists

    • ‘Torreya Guardians’ - Translocation north of native range due to climate envelope warming.

• 2. Preserve ecosystem functions & services (Maintain economic livelihoods):

  • Forestry - British Columbia

  • Fisheries - Australia

Managed Relocation Evaluation Framework: FFAC (L.15)

1. Focal Impact: impact on focal unit from climate change

2. Feasibility: constraints on opportunities for MR

3. Acceptability: societal willingness to pursue MR

4. Collateral Impact: effect of focal unit in recipient region

Importance of Speciation (L.16)

• Speciation generates biodiversity

• Speciation is an evolutionary process: we may want to preserve the processes that promote and allow future speciation to occur.

Species Concepts Classifications (B.M.E.) (L.16)

Biological Species Concept:

• Ability to produce fertile offspring

Morphological Species Concept:

• Distinct morphology

Evolutionary Species Concept:

• Independent evolutionary lineage

***The BSC is almost never used when defining speciation boundaries in plants.

Ring Species (L.16)

A series of populations arranged geographically in a ring, where neighboring populations can interbreed, but the populations at the ends of the ring cannot, despite gene flow through intermediate populations.

• Example: Ensatina salamanders in California.

Should we conserve subspecies? (L.16)

• There’s often a lot of them

  • Peromyscus maniculatus – deer mouse

    • There are like 40 subspecies of these mice, with founder populations on offshore islands.

***Forces driving speciation SDFH (L.16)

• Selection: natural, sexual, artificial

• Genetic drift: random changes, strong in small populations (non-selective change in gene frequencies)

• Founder effects: new populations start with limited genetic diversity

• Hybridization/reticulation: diverged species merge, sometimes forming new species

Types of Selection (L.16)

Artificial Selection: selecting for traits via breeding:

• Cabbage → Cauliflower | Kale | Brussels Sprout | Broccoli

Sexual Selection: selection for traits that promote reproductive success:

• Cichlid fishes in African rift lakes

  • If breeding advantage outweighs the disadvantage, sexual selection can take place.

Selection as a Force for Speciation (L.16)

• Stabilizing Selection:

  • House Sparrows: small sparrows and large sparrows were dying, while the medium sized sparrows lived.

• Directional Selection:

  • Directional selection within Polynesians for larger, more muscular bodies.

• Disruptive Selection:

  • The mean is selected against, i.e. the large and small House Sparrows survive while the mean die.

Adaptive radiation & rapid speciation (L.16)

• Rapid diversification in new/low-competition environments (Darwin’s finches, young islands)

• Can be very fast under strong selection (cichlids in Lake Victoria)

• Chromosome changes (ploidy) can cause almost instantaneous speciation (e.g., Spartina grass, sunflowers)

***Isolation and Speciation (L.16)

• Vicariance: barrier splits population → speciation

• Dispersal: population moves to new area → speciation

  • Sympatry: speciation in the same area

  • Allopatry: speciation in different areas

• Speciation is gradual; reproductive isolation increases over time

Does Natural Selection Provide Optimal Solutions? - NO (L.16)

• 1. Only need to be better than your competitors

  • Analogy – Tree line in the southern hemisphere. Flowering plants do not have the same adaptive traits as Conifers to be able to live at higher elevations.

• 2. Historical contingency

  • Francois Jacob 1977 - Natural selection acts as a tinkerer, not an engineer.

• 3. Adaptive landscape and peaks

  • Wright’s Adaptive Landscapes:

  • Evolved traits can be “trapped” on a sub-optimal peak within the adaptive landscape.

Reticulation/Hybridization (L.16)

• Reticulation: species diverge, form two separate branches, but might come back together and reform a single population or two new ones.

• Hybridization: ducks often interbreed across species lines, i.e. Grey Ducks and Mallards.

• Phylogenetic Tree Branching: snapshot of how species lineages are, not how we got to this point.