Presentation on theme: "Biodiversity & Biogeography N. Adam Smith Postdoctoral Fellow National Evolutionary Synthesis Center."— Presentation transcript:
Biodiversity & Biogeography N. Adam Smith Postdoctoral Fellow National Evolutionary Synthesis Center
Part I: Biodiversity “Biodiversity or biological diversity is the variety of life in all its forms, levels and combinations, including – ecosystem diversity, – species diversity, and – genetic diversity” (IUCN, UNEP, and WWF Rio Summit on Biodiversity, 1991) Copyright (c) 2012 Richard Ling What is biodiversity?
Genetic Diversity The range of genetic material present in a gene pool or population of a species High genetic diversity is thought to make populations more resilient to climate change, environmental perturbation, and disease Low genetic diversity can cause many problems…
Low Genetic Diversity in Cheetahs Cheetahs went through a population bottleneck at the end of the last ice age which reduced genetic diversity. Coupled with intense hunting and slow population growth, genetic diversity has not recovered.
Problems facing cheetahs Habitat loss and human encroachment Competition with other predators and predation by lions and hyenas in protected areas Continued trapping and killing of cheetahs on farmland (sometimes legally!) Low genetic variation leads to: – Abnormal reproductive traits – Increased disease susceptibility – Poor reproductive performance in captivity
Species diversity the variety of species per unit area – i.e., the number of species in your study site
Ecosystem diversity The range of different habitats in an ecosystem, community or biome associated with the variety of niches that may be exploited by different species.
What factors lead to biodiversity loss? Natural hazards (flooding, volcanic activity, fires) Global catastrophe (meteors, climate change) Habitat degradation, fragmentation and loss Introduction of non-native species, genetically modified organisms, and monocultures pollution Hunting, collecting, harvesting LOSS OF BIODIVERSITY AT A SPECIES LEVEL LEADS TO EXTINCTION
What makes some species more prone to extinction? Small population Specialized habitat Restricted food source Low reproductive potential (large mammals) Accumulation of toxins (whales) A prominent predator so killed by humans (e.g., cheetahs) Migrates long distances
example: Polar Bears Large and conspicuous Population size is shrinking Food source and warm fur Huge home range – Less likely to find mates Low reproductive potential Top predator
What else makes a species prone to extinction: Living on an island – High degree of endemism – Small populations – Lower genetic diversity – Vulnerable to introduced predators – EXAMPLE: GALAPAGOS
What else makes a species prone to extinction: Food for thought – does something have to be surrounded by water to be an island? – Habitat fragmentation – Micro-niche partitioning EXAMPLES: AFRICAN CICHLIDS
Measuring extinction Measuring extinction is very difficult How can you know when an organism is gone? First you had to know it was there, then somebody needs to count it! – Charismatic megafauna are more likely to be missed than cryptic microfauna.
Charismatic Megafauna Mammals, birds, reptiles are well described Fish, amphibians, invertebrates, and even plants are relatively poorly described Extinctions can go unnoticed – 120 years ago, the Gilbert Islands (central Pacific) were home to 3 shark species no longer found there – Evidence from fishing weapons fashioned from shark’s teeth!
Where is biodiversity the highest? Mammal Diversity – highest in the tropics Bat diversity accounts for a large proportion of this! Latitudinal gradients in species richness is a general trend for most terrestrial plants and animals Buckley et al 2010
Biodiversity Hotspots Species Rich, High Endemism, Threatened
Benefits of Biodiversity All of our food comes from other organisms – Many wild plant species could make important contributions to human food supplies. Rare species provide important medicines – More than half of all prescription drugs contain some natural product. Biodiversity can support ecosystem stability Biodiversity has aesthetic and cultural benefits Can generate income through to ecotourism
IUCN Red List Attempts to survey and quantify the state of the planets “at risk” species and governs their international trade Has weaknesses – probably underestimates the problems – Some taxa much better surveyed than others (mammals vs arthropods)
Subjects Used in Biogeography Anatomy Physiology Taxonomy Developmental Biology Evolution Geology Geography Ecology Climatology Paleontology Part II: Biogeography
Persistent Questions in Biogeography What enables a species to live where it does, and what prevents it from colonizing other areas? What are a species closest relatives and where can they be found? Where did its ancestors live? How have historical events shaped a species ’ distribution?
Persistent Themes in Biogeography Classifying geographic regions based on their biota Reconstructing historical development or lineages and biota, including their origin, spread, and diversification Explaining differences in numbers and types of species among geographic areas, and along geographic gradients
Alfred Russel Wallace “The Man Who Knew Islands” Malay Archipelago
In 1857 Wallace wrote: “A consideration of the birds had led us at some length into this subject,…how the existing distribution of species has arisen, or strictly connect it with those changes of surface which all countries have undergone.” Cassowaries on Aru Islands
What Wallace was trying to say 1.Variation occurs in nature 2.Variation may result in different reproductive success. 3.Species (populations) with higher fitness will persist 4.This leads to divergence from ancestral species.
Islands can serve as a laboratory for the study of biogeography. The biota of an island is simpler than that of a continental area, and the interactions are easier to understand.
Some flying animals, such as birds and bats, are capable of reaching even very distant islands.
Some plants have developed seeds or fruits that can be carried in the sea without being harmed.
Island life is probably more hazardous than that on the mainland. For one thing, catastrophic events have more severe effects. There is typically no place to hide.
Also, when a species is lost by extinction, it is more difficult to replace it through immigration than in a mainland situation. For this reason, islands tend to support fewer species than mainland areas of similar size (i.e., lower species diversity).
Rules of Island Biogeography Islands closer to a land mass have a higher probability of colonization Older islands are more likely to be colonized Larger islands should have more species Geographic isolation reduces gene flow between populations Over time, colonial populations diverge due to selection, mutation, and/or drift
Island Biogeography: Madagascar 4 th largest island in the world separated from India ~80-90mya High endemism due to isolation A biodiversity hotspot
Island Biogeography: Madagascar 4 th largest island in the world separated from India ~80-90mya High endemism due to isolation A biodiversity hotspot Lemurs – ~100 extant species – Colonized Madagascar from Africa 62-65mya
Lemur Distributions – a function of hydrology or microclimate? Pearson & Raxworthy 2009 Do species boundaries in lemurs correspond better with watershed boundaries or with climatic differences?
Lemur Distributions – a function of hydrology or microclimate? Pearson & Raxworthy 2009 Do species boundaries in lemurs correspond better with watershed boundaries or with climatic differences? Found BOTH were important