CONSERVATON BIOLOGY Lecture07 – Spring 2015 Althoff - reference Chapters ISLAND BIOGEOGRAPHY

Equilibrium Theories of Diversity Attempt to explain diversity patterns observed in natural ecosystem Some patterns noted: 1) species richness increases dramatically from high latitudes toward the equator 2) within latitudinal belts, diversity appears to be correlated with temperature, ecosystem productivity, topographic heterogeneity within a region, and structural complexity of local habitats 3) ___________________ exhibit species impoverishment

Equilibrium Theories of Diversity…con’t Everywhere, higher diversity is associated with greater ecological variety How do we explain these patterns of diversity? 1) the ultimate source of diversity is __________ (the production of new species by the splitting of evolving lineages) 2) Species _________ (i.e., go extinct)—most species that have ever existed have disappeared 3) If Speciation Extinction….Species increase If Speciation Extinction….Species decrease 4) Diversity might achieve a ________________

Consider “steady-state” of species richness…. Can examine this on a more localized level/scale (so do not think global scale for now) Best illustrated by examining patterns of diversity on oceanic islands Robert MacArthur and E.O. Wilson: EQUILIBRIUM THEORY OF ISLAND BIOGEOGRAPHY 1963 Evolution 17: (technical paper) 1967 Theory of Island Biogeography (book) ETIB

= the number of species on an island balances regional processes governing ____________ against local processes governing ______________. Equilibrium Theory of Island Biogeography

Number of species Rate

Number of species Rate Immigration

IMMIGRATION “Curve” As species fill an island, the ____________ of new species ______ Why? As new species arrive, fewer are left on the _________________ Those “left” on the mainland that haven’t colonized have ___________________ Once all species from mainland have colonized, immigration rate ____________

Number of species Rate Immigration Extinction

EXTINCTION “Curve” As species fill UP the island, the ______ at which they become _______________ Why? Main reason: ______________________ ______________ increases as species accumulate

Other FACTORS to consider... ____________________________ ____________________________ ___________ ____________________________

Who is most likely to colonize?

vs.

Small vs. Large Islands Small islands support fewer species than larger islands….. if _______________ from the mainland Vs.

vs.

Near vs. Far Islands Islands near the mainland have more species than those farther away…. for ____________ islands Vs. mainland

___________________________ – in general…but same result over time

ETIB Describes a ____________ and __________________________. Example, if a disaster exterminated part of an island’s biota, new colonists would—over time—restore diversity to pre-disturbance equilibrium

Test of ETIB Simberloff and Wilson (1970) They first counted all arthropod species present on each of 4 small mangrove islands in Florida Bay Then they removed entire arthropod fauna by fumigating the islands with methyl bromide Islands were resampled at regular intervals for a year

Note A Note B Note C months No. of species present

Simberloff and Wilson study Note A: islands closer to sources of colonists recovered more species faster than more distant islands Note B: at the end of the year, species richness had leveled off, suggesting that an equilibrium had been reached Note C: the new equilibrium numbers of species were similar to the numbers of species before defaunation

The Real World... True Islands “Habitat” Islands a) altitude barriers b) vegetation/habitat barriers c) disturbance RESULT: __________________

Relevance to Conservation Biology? Should guide our thinking about understanding how areas might be recolonized—or efforts that need to be made to “_________” recolonization (i.e., human transport, corridors, etc.) Should guide our thinking about ________ ________: big vs. small, one vs. many, near vs. far, etc.