Intro to Biodiversity
Lecture 2 of Unit 2
Biodiversity: The variety of life in the world or other given areas
Levels of biodiversity include genetic diversity, species diversity, and habitat diversity
Genetic diversity: Variety of genes or heritable traits in species or population. High genetic diversity has lots of different genes.
Importance of genetic diversity: Ability to respond to changes if some big event or disaster happens. Adapt and keep population. Resilience to environmental changes.
Low genetic diversity can cause inbreeding depression: a reduction in capability to survive or reproduce successfully due to inbreeding.
Recessive traits occur more because not enough good genes to buffer.
Characteristics of genetically diverse species: Large, interconnected populations.
Species biodiversity:
Species richness: Total number of different species in an area
Species evenness: The relative abundance of the different species in an area
Shannon-Wiener Index: Information of proportion of individuals for each individual in a population and multiplied by natural log of proportion, which gives a number that puts scale on how rich and even the species is, numbers range from 1-4.
1: Cornfield, birds.
4: Tropical rainforest with relatively even distributions.
Alpha, beta, gamma diversity
Alpha diversity: Diversity of organisms that share a habitat/are in the same community/site. Can use Shannon-Wiener Index.
Beta diversity: Change in species composition and/or evenness between two sites.
Gamma diversity: Diversity of organisms in a large area.
Importance of Biodiversity: Adaptability, filtered water and air, ecosystem services functionality, resilience to changes
Ecosystem resilience: Ability of an ecosystem to regain essential functions after disturbance
Ecosystem resistance: Ability of ecosystem to maintain essential functions despite a disturbance
Habitat Diversity: A measure of the variety of habitats in a specific area, including the number, types, and spatial arrangement of those habitats
Trickle-down effects on habitat and genetic diversity, important for supporting services.
Worldwide Threats:
Climate Change
Pollution
Habitat loss
Invasive species
Passenger pigeons (overexploitation)
Climate change is the biggest worldwide threat, but on a more local scale, it’s any of the other 4 factors mainly influencing ecosystems
Habitat Loss: Loss of habitat leads to losses in species diversity, habitat diversity, and population sizes, thus affecting genetic diversity as well
Forests and wetland, huge amounts of deforestation
Habitat fragmentation: One large habitat is split up by an impassable barrier, e.g. highway, city, farming field. Leads to ecosystem homogenization, where ecosystems become more similar to each other, since you’re removing the interior high-quality habitats and creating more edge, pretty similar around the world, responsible for homogenization. Types of species that thrive in edge habitats are generalist species, like brown-headed cowbird parasitizing golden-cheeked warbler. Can tolerate high sun, more exposure. Reduces population sizes and ability to get to each other. Not great for genetic diversity.
Florida panthers previously occupied the American Southeast, but panthers are killed and Florida’s turned into farms and cities. Now, panthers are down to 5% of original habitat size. They reached a population in 70s and 80s, which brought down from thousands to 20. Leads to low genetic diversity, which results in in-breeding.
Genetic bottleneck: Large biodiversity, all die, now all diversity is coming from a tiny sample size, and as population starts to grow again, will run into in-breeding depression, which comes in the ability not to resist diseases and weird physical traits (kinked tail, messed up coloration that decreases camouflage abilities). Helped reduce impact by breeding with Texas panthers, back up to 200 Florida Panthers.
Wildlife corridor: Designated areas that connect places where animals roam for free.
Cars are the largest threat to Florida Panthers.
Not large enough wildlife corridors, way up high on trophic level, need lots of food, roams large land. To have breeding populations, must have enough space. Habitat fragmentation affects large species that require lots of space.
Invasive species: Results in ecosystem homogenization.
New Pangaea, where species are getting everywhere and killing localized species, resulting in general species around the world.
Extinction of local species via out competition, predation, food web disruption, or disease/pest transmission
Alteration of habitat.
Kudzu brought over in 1800s, grows fast and nothing eats it, erosion control & ornamental. Completely encroaches upon other ecosystems, so no light is getting to the trees, reduction of species diversity, able to create monocultures.
Emerald Ashbore on ash trees, wiped out.