2. Species - the Cornerstones of Biodiversity v2-1

2 Species the - DEFINING BIODIVERSITY If conserva8on biologists intend to preserve it and use it sustainably they must

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Unformatted text preview: DEFINING BIODIVERSITY If conserva8on biologists intend to preserve it and use it sustainably, they must have a good idea of what it actually is and how to measure it. Biodiversity encompasses all the variety that exists within living components of the biosphere… Gene8c Diversity Species Diversity Ecosystem Diversity Why is Gene8c Diversity Important? •  Short- term: –  Loss of gene8c diversity increases the risk of ex8nc8on Florida Panther •  Long- term: –  Gene8c diversity increases the ability of species to adapt in response to future environmental change Ecosystems Ecosystem is a biological community with its associated physical and chemical environment Ecosystem Processes include water cycles, nutrient cycles, and energy capture. Ecosystem Services are the range of benefits provided to people from ecosystems Loss of Species from Ecosystems Sea OPer Example • European and Russian trappers hunt sea otters to near extinction in the 18th and 19th centuries. • The decline of the sea otters, which feed on sea urchins, allows urchin populations to explode. • The burgeoning sea urchins decimate the kelp beds, which are critical habitat for spawning fish. • Fish begin to decline for lack of spawning habitat; this affects fishermen's catches. • International treaty enacted to protect sea otters. • In areas where the otters recovered, urchin populations are once again kept down, the kelp beds recover, fish nurseries recover, and fish catches rise again. Why is This Course Called “Ex8nc8on of Species”? • Species reflect the evolu8onary history of life on earth • Specia8on contributes to adapta8on and evolu8on • Species are recognizable and iden8fiable • Individual species provide resources for humans • Species play different roles in ecosystem func8on and services Biological Species Concept (BSC) •  A group of individuals that actually interbreed or can nature, not necessarily poten*ally interbreed in grouped according to similarity of appearance. •  The BSC is generally the most useful and common defini8on for scien8sts working with living examples of mammals, birds, and fish. Black Bear = European Brown Bear Grizzly Bear • Western and Eastern Meadowlarks appear to be iden8cal, and their ranges overlap, but their dis8nct songs prevent interbreeding. Western Meadowlark Eastern Meadowlark Problems with BSC: Asexual Reproduc8on • The bacterium shown at right is reproducing asexually, by binary fission. • The definition of a species as a group of interbreeding individuals cannot be easily applied to organisms that reproduce only or mainly asexually. Problems with BSC: Hybridiza8on •  Interbreeding occurs prePy commonly, especially among different bird “species”. Barred Owl SpoPed Owl Problems with BSC: What is meant by “poten8ally” interbreeding? Morphological species concept • A group of individuals that is morphologically, anatomically, or physiologically distinct from other species. Problems with Morphological Species Concept •  Individuals of a single species can look very different yet interbreed Occurs in wild species as well, for example, Happy-face Spiders (Theridion grallator) • These two ants are sisters of the species Pheidole barbata, fulfilling different roles in the same colony. The opposite is also true • DNA analysis o]en shows that morphologically similar species are very different gene8cally (i.e., don’t interbreed) and should be considered separate species (sibling species). Grey Flycatcher Dusky Flycatcher Phylogene8c Species Concept •  A group of organisms that share a common ancestor and is evolving together and separately from other groups Species 1 Species 2 Phylogene8c Species Concept •  Usually results in many more species the BSC •  Strictly phylogene8c (evolu8onary) classifica8ons can be counterintui8ve and imprac8cal. –  Some Brown Bears more closely related to Polar Bears than other Brown Bears –  Crocodiles and alligators more closely related to birds than to other rep8les Species Concepts in Practice •  The most widely accepted definition is: “A group of interbreeding natural populations that are reproductively isolated from other such groups” (BSC) •  But a species is often what a competent taxonomist says it is •  Genetic data can inform all three definitions by helping to (1) determine how “different” species really are, (2) determining if species interbreed, and (3) determining how closely species are related Species Concepts in Prac8ce •  Defining species is complicated, but not just an academic exercise •  Conserving species (i.e., biodiversity) depends on being able to iden8fy them •  There are 1- 30 species of Drymis trees in New Guinea, depending on the defini8on used. •  Uncertainty should not produce paralysis. ...
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This note was uploaded on 12/17/2011 for the course ZOO 360 taught by Professor Staff during the Fall '08 term at Wisconsin.

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