Endangered species

What is a species

There are 3 concepts for species as this is a hard subject to broach; the morphological species concept, the biological species concept, and the phylogenetic species concept. 

The morphological species concept states that a species is a set of organisms that are phenotypically similar and look different from other sets of organisms. The issue with this theory is that individuals can look very similar or different morphologically and do not interbreed while those that look different do interbreed (sexual dimorphism). 

The biological species concept states that a species are groups of actual or potential interbreeding reproductive groups isolated from other groups. The issue with this concept is that individuals can be allopatric (do not occur in the same place) but you cannot determine whether they are reproductively isolated or not. This theory is also not applicable to extinct species, fossils, or asexual species because you cannot determine reproductive isolation. And lastly natural hybridization and gene flow do exist between species. 

The phylogenetic species concept states a species is the smallest diagnosable cluster of individuals with a parental pattern of ancestry and descent. These shared derived traits can be morphological, behavioral, physiological, or genetic, and are the basis for grouping populations into distinct species. This theory can be applied to allopatric populations and asexual or extinct organisms. 

Phylogeny tree

Represents the evolutionary relationships among a set of organisms or taxa groups

The tips of the tree represent groups of descendent taxa (often species)

The nodes on the tree represent the common ancestors of those descendents

The Linnaeus System of Classification

Kingdom, phylum, class, order, family, genus, species

Organisms that are apart of the same phylogenetic clade evolved from a shared ancestor

Population

A population is a biological unit at the level of ecological integration where it is meaningful to speak of birth rate, death rate, sex ratios, and age structure in describing properties or parameters of the unit. A population can also be described as a group of organisms of the same species occupying a particular space at a particular time, with the potential to breed with each other.

Basic population size

Births are the input

population size grows from immigration and sinks from emigration

Deaths are the output

Species according to the ESA

Any subspecies and any distinct population segment (DPS) of any species of vertebrate, fish, or wildlife which interbreeds when mature

A population is a DPS if it represents an evolutionary significant unit (ESU)

ESU (evolutionary significant unit)

A population must meet 2 criteria 

• Distinctness: It must be substantially reproductively isolated from other conspecific units

• Isolation does not need to be absolute but strong enough for important differences

• Significance: It must represent an important component in the evolutionary legacy of the species. The population must contribute to the ecological or evolutionary diversity of the species as a whole

Species interactions include

• Competition

• Predation

• Herbivory 

• Parasitism

• Mutualism

Ecosystem engineer

Can strongly modify their habitats effecting other species

ex: beavers, woodpeckers, mussels 

• Ecosystem engineers can also be keystone species

• However, keystone species can be much harder to recognize in a community

Keystone species

Play a pivotal role in maintaining the structure and function of their ecosystem, with their removal causing significant changes

ex: wolves, sea stars, prairie dogs

Trophic structures

Primary producer → primary consumer → secondary consumer → tertiary (apex) consumer

Trophic cascade effects occur if there are strong interactions among species

Top down control

Predator control over lower trophic levels population

Bottom up control

Resources in lower trophic levels control upper trophic levels

Quadrat

Tells an ecologist about both the size and density of a population

Biodiversity

Refers to the variety of life forms and habitats found in a defined area (genus, species, ecosystems)

Genetic diversity

The genetic variation existing within a species (alleles, total genes, or chromosome structures)

Species diversity

At the species level it depends upon the number of the species of a region

Ecological diversity

At the ecosystem level (deserts, rainforests, etc)

Species richness

Number of “species” present in a community

• First and oldest metric of diversity, very simple to calculate

Limitations:

• Only resident species are counted

• Treats common and rare species equally

Shannon Wiener diversity index/entropy

Considers both species richness and evenness

Increased values indicate increased diversity

Limitations:

• Range of values for real communities are typically between 1.5 and 3.5 

• Has no units

• Ecological value only as comparison between at least two communities

What increases the species diversity here?

• The number of species in the community

• The equitability of the abundances of each species in the community

Evenness

Measurement of the equitability among species in the community

Values range from 0 - 1

Marine biodiversity

Total species richness is mostly driven by fish

Regional peaks in SE Asia (pacific), SE Africa (Indian), and the Caribbean (atlantic)

Species groups from coastal or oceanic habitats

Most coastal taxa diversity peaks in the W pacific with a latitudinal gradient along the coasts

Oceanic taxa pan-tropical or circumglobal distributions (peak between 20 and 40 latitude)

Terrestrial diversity

High proportions of terrestrial and freshwater species occur in the tropics

Warmer areas hold more species than colder areas

Wetter areas hold more species than drier ones

Areas with varied topography and climate hold more species then uniform ones

Less seasonal areas hold more species than highly seasonal areas

Areas at lower elevation hold more species than areas of higher elevation

Why these latitudinal patterns?

• Different climates

• Changes in productivity

• Topography heterogeneity

• Differential habitat size

Hypotheses that explain the latitudinal biodiversity gradient

• Immigration rate

• Extinction rate 

• Speciation rate

2 key environment parameters underlying drivers: Area + “energy”

• Strongest patterns of variation can be found across latitudinal gradients

• Species richness increases from the poles to the equator 

• The distribution of organisms is not uniform

What are endangered species?

Species at risk of extinction that require protective management (IUCN)

Critically endangered

Species >/ 50% probability of extinction within 10 years or 3 generations, whichever is longer

Endangered

Species >/ 20% probability of extinction within 20 years or 5 generations

Vulnerable

Species >/ 10% probability of extinction within 100 years

Endangered species according to the US ESA

Any species which is in danger of extinction throughout all or a significant portion of its range 

Threatened species according to the US ESA

Any species which is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range 

Mass extinctions

There have been 5 mass extinctions due to:

• Climate change 

• Ocean atmospheric chemistry

• Volcanic activity

• Meteor asteroid impacts

Ordovician Silurian Extinction (450 - 440 mya)

Due to massive glaciation and sea level drop

Late Devonian Extinction (375 - 360 mya)

Due to global anoxia triggered by global cooling or oceanic volcanism

Permian Triassic Extinction (252 mya)

Due to severe volcanic activity, environmental change, and long term methane release

Triassic Jurassic Extinction (201.3 mya)

Due to volcanic activity and giant flood basalts (sudden release of CO2, climate change amplified the greenhouse effect)

Cretaceous Paleogene Extinction (66 mya)

Due to an asteroid impact (chixulub crater in Central America)

Is the 6th period of mass extinction occurring now?

Thousands or even tens of thousands of species are predicted to go extinct in the coming decades

The present rate of extinction is 100 - 1000x faster than the present rate of speciation

Most known extinctions have occurred on islands, including 68% of mammal extinctions and 82% of bird extinctions

Species area relationship

The number of species found in an area is proportional to the size of this area (within a region)

Steeper species area relationships imply greater species losses per unit of area

Indicators of the sixth mass extinction

Population size of terrestrial vertebrate species on the brink, less than 1000 individuals

Most of there species are close to extinction, less than 250 individuals

In most cases, those few individuals are scattered through several small populations

More losers than winners

Anthropocene extinction crisis is undergoing a rapid biodiversity imbalance

Levels of declines greatly exceed levels of increases for all groups

Communities with smaller habitats will be most affected by changes in habitat size

There are NOT uniform patterns in global diversity

Mass extinction

A loss of 50% of species

Why do species become endangered

1. Habitat degradation/loss 

• Human activity (industry, ag, forestry, aquaculture, commercial fishing, mining, sediment and groundwater extraction, infrastructure development)

• Human activities can cause changes in native species abundance or changes in disturbance regimes (dams, fires)

2. Invasive species

• Direct effects (predation, parasitism, disease, competition for resources or hybridization)

• Indirect effects by disruption of mutualisms, changing the abundance of population dynamics of native species or modifying habitats to reduce quality

3. Over exploitation

• Second most important threat to biodiversity, particularly outside the US

• Direct exploitation (hunting, fishing, etc)

• Indirect effects (habitat destruction associated with harvest techniques, changes in ecosystem dynamics by removal of species)

4. Global environmental change

• Climate change worsens the survival challenges of species by altering their habitats, disrupting food sources, and increasing extreme weather events

• Global warming, shifting ecosystems, and ocean acidification threatens species like polar bears, coral, and amphibians

• Many species struggle to adapt or migrate, leading to population declines and higher extinction risks

Why save endangered species?

1. Loss of biodiversity

• Intrinsic values of species and maintaining functioning ecosystems and health and wellness of our planet

2. Medicinal benefits

• 56% of most popular prescription drugs contain natural compounds, only 1% of all plant species have been screened for potential uses

3. Commercial / economic benefits

• Water, timber, food, hunting, fishing, and non consumptive uses like bird watching, biking, hiking, camping

4. Ecological benefits

• Raw materials, water quality, nutrient cycling, soil creation and maintenance, pollination of ag plants, climate regulation

5. Aesthetic benefits

6. Metaphysical, epistemological, and or ethical beliefs

7. Other environmental worldviews

• Natural law theory

• Rights of nature

• Virtue theory

• Divine command theory