CONSERVATON BIOLOGY Lecture05 – Spring 2015 Althoff - reference Chapters 6-10 THREATS TO BIODIVERSITY Part II

Extinction Process Why are some species more vulnerable to extinction than others? SIMPLE ANSWER– ________________ Examples from Hunter and Gibbs: a) bighorn sheep occupying semi-isolated ranges b) bird species on islands off the coast of Great Britain

Extinction Process BIGHORN SHEEP POP N ON SEMI-ISOLATED MOUNTAIN RANGES

Persists Extinction Process BIRD SPECIES (62 SPECIES) ON ISLAND OFF THE COAST OF BRITIAN Fail:

Why are some species rarer than others? Restriction to an _____________ type of habitat Limitation to a ________ geographic range Occurrence only at ______ population densities 1 2 3

Restriction to an uncommon type of habitat May have resulted because they evolved ___________ characteristics that allow them to live there and nowhere else. Ex. Naked mole rats; black-footed ferretsCave-dwelling invertebrates, fishes,and amphibians Some may been successful there simply because they ________ successful any place else (i.e., cannot out compete other species). Ex. Steamboat buckwheat 1

Limitation to a small geographic range May have resulted from geographic _______ Ex. Populations on Islands, in a lake (cichlid fishes in Lake Malawi Africa) ______ range of “tolerable” conditions can result in small geographic range Ex. Many Amazonian plant species evolved in special soil conditions. Ex. Plant species in bogs where very acidic conditions 2

Occurrence only at low population densities Body size: large animals take lots of space Ex. Elephants, moose, elk (in certain settings) Small density populations persist because they do well when they __________ with one another. Ex. Wolverines, Hawaiian hawk 3

Usually, a species exhibits just ____ of the 3 basic “rare” charactistics, but… A few species may have 2 or even 3 of the “rare” characterisitics Rare habitat Small geographic range Low pop n density 1 2 3

Why are Rare Species Usually More Vulnerable to Extinction than Common Species? #1 likely reason: rare species have a greater chance of being pushed into extinction because of _____________________—especially if they have a small geographic range….about ¾ of all known extinctions since 1600 have been island species Other reasons could include: _______________ ______ (especially if biased against females), ______________ problems (genetic drift, inbreeding, and bottlenecks)

Why are Some Species Particularly Sensitive to Human-induced (anthropogenic) Threats? __________________________________ : low reproductive rate (small number of progeny, long generation time, etc.), limited dispersal capabilities, inflexible habitat requirements, etc. ______________: singled out by people. Examples include wolves and African wild dogs (to eliminate threat of livestock loss), passenger pigeons (edible), diamond-backed turtles (edible) 1 2

Why are Some Species Particularly Sensitive to Human-induced (anthropogenic) Threats? …con’t ____________________: those tied to ecosystems preferred by humans are more at risk—think areas with fertile soils (prairies vs. agriculture) or abundant water resources (for hydroelectric power, etc.) ________________________: Fragmentation can reduce extensive tracts of one habitat-type or another (think many large terrestrial carnivores/ predators). 3 4

Patchy Distributions and Metapopulations ______________ = model of population structures whereby each patch of habitat contains a different subpopulation of a species. A group of “patch” populations is collectively a metapopulation. Metapopulation __

Examples of Metapopulations Prairie chickens Sage grouse Black-footed ferrets Piping plovers Green salamanders

Keep in mind…. ______ species that are distributed in habitat patches are composed of metapopulations. Often bird species—being highly mobile— are not as likely to exhibit metapopulation structure Metapopulations is a concept associated with _________________________ ____________________ Metapopulation dynamics can be viewed as two types of subpopulations & two types of processes……

Subpopulations & Processes Associated with Metapopulation Dynamics Two subpopulation types: 1) ________ pop n 2) ________ pop n Two processes: 1) local ______________ 2) ______________ (recolonization)

Source vs. Sink (sub)populations Source: produce substantial number of _________ that ___________________ Sink: do ____ produce enough individuals to maintain their local numbers and typically only continue to exist through _______ __________ from other subpopulations (aka source subpopulations.

Sink (sub) populations…. Are inherently _____ to go ______ (aka local extinctions) because the habitat they occupy is either too small or of too poor quality to regularly (for years and years and years) produce enough offspring to remain sustainable And, often can be colonized (or recolonized) by dispersing individuals from source populations because they appear to be suitable habitat for breeding/reproducing

Cache River prothonotary warbler subpopulation (Wing & Prayer video) Dickcissel population in Central Prairie Sink (sub) populations….examples Sutton Center Oklahoma

Cowbird brood parasitism of Dickcissels

In summary… The metapopulation concept offers a framework for understanding the dynamics of populations in _________ landscapes (i.e., think fragmentation) Subpopulations are subject to (local) extinction and colonizations (recolonizations)….as influenced by ____________ subpopulations within the metapopulation Patchy landscapes (aka fragmentation) is becoming more and more common because of _________ activity. However, do not assume ALL at-risk species conform to the metapopulation concept

In summary…con’t Some species are rare than others because they are 1) restricted to an uncommon habitat type, 2) are limited in their geographic range, and/or 3) occur only a low population densities. In rare instances, a species might have all 3 of the above characteristics. Many species are at-risk due to anthropogenic influences: 1) limited adaptability & resilence 2) human attention 3) ecological overlap 4) large home-range requirements