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Global Biodiversity

Global Biodiversity. Global Biodiversity Patterns and Processes

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Page 1: Global Biodiversity. Global Biodiversity Patterns and Processes

Global Biodiversity

Page 2: Global Biodiversity. Global Biodiversity Patterns and Processes

Global BiodiversityPatterns and Processes

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Global BiodiversityPatterns and Processes

• What is Biodiversity?• Biological diversity is the sum of all

living things• It can be considered at many levels

(e.g. genetic, regional, evolutionary lineage, number of ecosystems)

• Hierarchical perspective: genes, pop(s), species, communities, ecosystems, landscapes

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Global BiodiversityPatterns and Processes

• Genetic Diversity• Genetic diversity is the ultimate source

of biodiversity at all levels• Recent advancements now allow us to

measure (and quantify) genetic diversity• Important in establishing breeding

programs• May allow species to broaden tolerances

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Global BiodiversityPatterns and Processes

• Genetic Diversity• Consider the use of genes in crops and

livestock…can be either incorporating genes or just preserving existing breadth

• Consider Bt cotton: Bacillus thuringiensis (Bt) is a spore forming bacterium that produces crystals proteins, which are toxic to many species of insects.

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• There are trade-offs

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• Population-level Diversity• The variation within members of a species

or population is extremely important (represents evolutionary history and is the source of potential future adaptations)

• Also provides a great deal of information about the amount and rate of gene flow between and among populations (more later)

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• It is the local populations where environmental challenges occur and genetic diversity is maintained

• Consider a species/population of corn that evolved in soil with high mineral (e.g. metals or salt) levels

• That population maybe become an invaluable crop species in some locations

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Global BiodiversityPatterns and Processes

• Guppies in Trinidad streams have evolved without fish predators

• Consequently, they have very different life-history characteristics than species/populations exposed to predators

• If a reintroduction or population supplementation is needed, knowledge of genetics and plasticity important

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• Populations may also serve a functional role, which may be independent of other populations

• E.g. pollinators

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• Human Cultural Diversity• Consider human cultural diversity

and the reservoir of knowledge, skills, and traditions throughout the world

• E.g. 6,526 distinct languages

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• Non-random distribution of habitats

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• Diversity of Species• Despite many references to

‘biodiversity’ and others at the species level (e.g. ESA, CITES) it is the populations that are as or more important (but not as easily comprehended by the public or politicians)

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• What is the difference between a species and population?

• Can be somewhat difficult to determine if they are one species or two…

• Why? • Problems: fossils, asexual organisms,

lack of knowledge

It is really a gradient

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Global BiodiversityPatterns and Processes

• For many ‘bioinventories” or rapid assements, may use concept of ‘morphospecies’

• As species (and populations) evolve, they continue to accumulate genetic differences

• To determine relatedness among these species (or pop(s)), biologists attempt to reconstruct phylogenies (more later)

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Global BiodiversityPatterns and Processes

• Biological classification system based upon the idea of hierarchical organization and relatedness

• King Phillip Came Over For Golf Saturday

• Should always be a bifurcating tree

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• How many species are there?• Approximately 1.75M named with

another 300K fossil sp• On average, 300 sp named each day• Two new phyla have been named in

past 25 yrs• Range is 10M-50M

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• For starters, the immense richness of viruses, bacteria, archaea (singled-cell organisms in extreme environs), protists and other unicellular organisms

• Only 80,000 fungi described• In Britain, 6x fungi vs. vascular plants• Extrapolate worldwide, 1.6M fungi• Nematodes >200 sp in a few cm3

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Global BiodiversityPatterns and Processes

• Mites: 30,000 sp described (but probably >1M)

• Insects: almost 1M described, but consider canopy fogging

• 4 sites <70km proximity, 1% common

55%

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Global BiodiversityPatterns and Processes

• Diversity of higher taxa• Until recently, 5 kingdoms

recognized

Plantae

Fungi

Monera (bacteria)

Protista

Animalia

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Global BiodiversityPatterns and Processes

• Today, there is a recognized division among the prokaryotes and we have the Archaea and Bacteria

• Genetic diversity is as great as that across Eukaryotes

• Many new kingdoms ascribed to Archaea, Bacteria, and Protists

• Why care?

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• They evolutionary lineage of each species is important for several reasons

• 1) evolutionary potential relies on the diversity of life (many differences, albeit small)

• 2) lineages are storehouses of info on the history of life

• 3)functioning ecosystems depend upon the variety of life

• 4) aesthetic benefits correlated with diversity

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• Diversity of biological communities• The composition of communities changes

over time and space• Membership within a community is

probabilistic• 3 common metrics

– Sp richness, evenness, abundance

• Frequently compare metrics across habitats or sites (or genes)

• Could also use weighted measures…

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• Are there limitations to using a metric like diversity?– Species identity…lose valuable

information on functional role, exotic vs. native, life-history characteristics

• Biological communities are of conservation interest because the relative abundances, combinations, +/- can all provide valuable information

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• Ecosystem and Biome Diversity• Typically terrestrial systems typically

classified by shape and life-forms of the plants that dominate them

• Holdridge’s widely used life zone system is entirely based upon climatic variables

• Although communities grade into one another, major divisions are useful for analyses and descriptions

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• Things also change at relatively large scales based upon: latitude, altitude, and precipitation gradients

• At a finer scale, things change with soil type, slope, and species composition

• Recently the WWF reclassified the Earth’s biomes into 867 terrestrial biomes (thought to represent distinct assemblages)

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• Ecosystem approach• Managing at the ecosystem allows

for common goals across multiple owners and allows for ‘large scale’ planning that is likely appropriate for even relatively large organisms

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• Species Richness over Geologic Time• The number of species at any given

moment represents the balance between extinction and speciation rates

• That number will vary according to the frequency and intensity of extinction and/or speciation events

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• The fossil record shows a rough estimate of trends in species richness during the history of life on Earth

• Cellular life began about 3.8 bya (bacteria) and eukaryotics probably about 2 bya

• Things were relatively quiet until the ‘Cambrian explosion’

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Global BiodiversityPatterns and Processes

• Fig 2.5 Diversity of marine families from Cambrian to present

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• Terrestrial plant appeared early in the Silurian and their richness increased rapidly during the Devonian

• Then during the Cretaceous, another important event occurred, the appearance of ‘angiosperms’

• Had ‘cascading effects’

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• Fig 2.6• Each group,

ferns, gymnosperms and angiosperms, have all dominated at one time

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• Rates of species formation• Speciation rates are not consistent• When do you think it accelerates?

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• Rates of species formation• The first was the Cambrian (500mya) • Second Paleozoic (440mya)• The third set diversity way back in

Permian (250mya), followed by Triassic explosion

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Global BiodiversityPatterns and Processes

• Cambrian: all major groups of living organisms appeared during this time (and some that did not make it)

• Paleozoic and Triassic greatly increased families, genera and species, but no new phyla emerged

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• Factors impacting rates of speciation• Any guesses?

– Mass extinctions– Increasing separation of landmasses– New species and species interactions

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• Diversity explosions throughout the ages

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• Break-up of Pangea in Laurasia ad Gondwanaland followed by more isolation

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• Rates of Extinction

• Similarly, rates vary throughout time

• 6 major events

60% 75% 95% 65% 75% **

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• Although species generally recovered, there is a lag of about 10my

• The major impact of mass extinctions events has been to eliminate some lineages while opening ecological niches for others

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• Current patterns of species richness• Diversity is not spread evenly

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• To properly preserve species, it is important to know where species occur

• One such tool is a GIS• Another useful approach is to divide

species richness into major components– Alpha-richness (small homogeneous area)– Beta (rate of change across communities)– Gamma (changes across larger landscapes)

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• High α generally means many rare sp• High β means the cumulative number of

species recorded rapidly increases as additional areas are censused along some environmental gradient

• High γ may result from having many different types of habitats within a larger landscape and each of those habitats having some unique members

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• Species turnover for birds in Mediterranean

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• Differentials of turnover curves

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• Patterns of Endemism• Everything is endemic at some scale• There are areas of high endemism,

usually resulting from isolation (e.g. islands, large dispersal barriers)

• Areas of endemism are usually not associated with areas of high diversity

• Why?

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• Patterns of Endemism• Not surprisingly, patterns of

endemism differ greatly across taxa• For example, SAf and sw Aust have

very high levels of plant endemism, but not animals

• However, there are correlates for endemism among vertebrates

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• Marine diversity (damselfish)

• Indo- Pacific a hotspot

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• Latitudinal Gradient in Species Richness

• In both terrestrial and marine environments, tropical regions have more species than temperate ones for many (or most) all taxonomic groups

• Exceptions: marine birds and mammals, seaweeds, salamanders

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• Bivalve mollusks

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• Although the pattern is widespread, the mechanism (process) generating it remains in question

• Additionally, it is likely that different groups have different combinations of factors determining their distribution

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• Species-area Curve• One of the first ecological

relationships established empirically was the relationship between area and number of species

• S is species number, A is area, z represents how quickly species are accumulated and c is a constant

S=cAz

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• z varies across taxonomic groups and habitats– E.g. relatively low values ≈0.15 on

oceanic islands to 0.25 to 045 for continents

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• Reptiles and amphibians

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• Landbirds and freshwater birds in SE Asia

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• One confounding factor is the relatively large area of the tropics

• Consequently, is the higher diversity in the tropics a result of simply larger areas?

• What other factors may contribute to higher diversity in the tropics?

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• Species Richness-energy Relationships• Simply the more energy that is available

the more biomass enables more individuals (hence species) to coexist

• In tropics, even less energy used to maintain oneself

• Higher productivity can also allow for dietary specialization

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• Evidence for these patterns are not consistent– E.g. strong correlation between annual

evapotranspiration and tree sp richness in NAm

– E.g. some of the most productive ecosystems (estuaries, hotsprings, seagrass beds) are species-poor

• Look at relationship between soil fertility, plant richness & seed dispersers

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• Marine systems: richness and depth• ‘the paradox of enrichment’• Sp do well in

either fresh or saltwater

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• Energy may also influence richness indirectly through increases habitat complexity (structure)

• Habitat complexity and richness is generally positive for a wide-ranging group of organisms (think birds in grasslands vs. forests)

• Conversely, think about lizard richness in the desert…

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• Disturbance and Species Richness• Easy to understand how large climatic

variation could reduce sp richness• More poleward populations are

impacted by remaining individuals having characteristics that favor lower speciation rates (less specialization, larger ranges and greater vagility)

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• Disturbance and Species Richness

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• Disturbance and Richness• Physical disturbances can influence

local richness by destroying habitat, selectively (or not) killing individuals, and sterilizing soils

• Consider a constant environment, what should this lead to? Why?

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• Intermediate Disturbance Hypothesis

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• Consider the rocky intertidal communities of the Pacific Coast

• Pisaster ochranceus feeds on the competitively dominant mussel Mytilus californianus

• When it is removed, allows ‘less’ competitive individuals to become established on the rocks

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• Intermediate Disturbance Hypothesis

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• Interactions between local and regional species richness…

• Local species richness can strongly be influenced by local interactions and process operating at larger spatial and temporal scales (e.g. dispersal, speciation, historical biogeography)

• Ultimately, are there limits to community numbers?

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• Is it limited by niche overlap?• Does the chemical warfare between plants

and herbivores set limits to sp richness or does it promote speciation?

• Are there limits to the size of mimicry systems and do mimicry systems allow for more or less species to coexist?

• Has the richness generated by plant-pollinators been reached? Seed dispersers?

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• Importance of Biodiversity• Merit vs. money?• Many examples of ecosystem

services

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• Importance of Biodiversity• Merit vs. money?• Many examples of ecosystem services• However, it is not clear what the

relationship between ecosystem function and species richness

• Importance of rare species, which are most common, is poorly understood

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• Increasingly there are opportunities for researchers to test some ecosystem theory at very large spatial scales

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• Biological dynamics of forest fragment project (Manaus, Brazil)

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• Calling Lake fragmentation exp (Canada)

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• Savannah River Corridor Project

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• Future of Biodiversity Studies• Need to generate many more

taxonomists; especially in tropical countries and in groups poorly studied

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• E.O. Wilson: 50yr inventory• Rapid Assessment Program: focus on

areas of high endemism and diversity– Groups of experts on the better known

groups (e.g. butterflies, birds, flowers)

• Establish research stations in same area

• Combine RAP and intensive studies from research stations

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• Continue phylogenetic studies• Further examinations on anthropogenic

stresses on the environment• Millennium Ecosystem Assessment: a

multi-agency, governmental coalition of international development and conservation organizations, and scientists to assess the status the Earth’s ecosystems

• Hope is to help focus research on the connections between the status of biodiversity and ecosystem services

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• MEA

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• The end of chap 2