Transcript PPT
Readings • Readings on web page. – BSCI: Chapter 2. – CONS: Chapter 3. • Anyone need a book? Biological Species Concept • “Groups of actually or potentially interbreeding populations which are reproductively isolated from other such groups.” – Ernst Mayr, 1963 Conservation Implications? • Complete reproductive isolation . . . would not be satisfied even by some recognized species that are known to sustain a low frequency of interbreeding with related species. – Statement by the FWS and NMFS regarding interpretation of DPS’s in response to public comment. http://endangered.fws.gov/policy/pol005.html Mechanisms Promoting Species Identity • Biological – Reproductive Isolation • Cohesion – Reproductive Isolation – Natural Selection Morphological Species Concept Hedgehog Cactus Phylogenetic Species Concept mammary glands live bearing placenta Non Mammalian Vertebrates Egg Laying Mammals Marsupials Placental Mammals Review: Species Concept • Why is a species a species? – Biological: Reproductive Isolation – Cohesion: Reproductive Isolation + Natural Selection • Is a species a species? – Morphological: Practical Species Identification – Phylogenetic: Evolutionary History Species Concepts Applied A. R. Templeton, in Speciation and Its Consequences D. Otte, J. A. Endler, Eds. (Sinauer Associates, Sunderland, MA, 1989) pp. 3-27. Phylogenetic Methods: The Role of Molecular Data • Hybrid Species • Genetic Management • Evolutionary Significant Units Evolutionary Significant Units • A set of populations that is morphologically and genetically distinct from other similar populations. • A set of populations with a distinct evolutionary history. DPS’s • “Species” includes . . . any distinct population segment of any species of vertebrate . . .” • Discreteness – “It is markedly separated from other populations . . . Quantitative measures of genetic or morphological discontinuity may provide evidence of this separation.” • Significance – “The discrete population segment differs markedly from other populations of the species in its genetic characteristics.” http://endangered.fws.gov/policy/pol005.html Extinction Causes of Extinction • Deterministic factors (stacked deck) – Realized growth rate is negative – Deaths > Births • Stochastic factors (bad luck) – Intrinsic • genetic stochasticity • demographic stochasticity – Extrinsic • environmental variation (EV) • catastrophe change in environment K Deterministic decline to extinction ln(N) time Population fluctuates due to demographic and genetic stochasticity K ln(N) time K ln(N) catastrophes time Population fluctuation due to environmental variation Catastrophe Severe and rare environmental variation (Remember for Vortex) Environmental Change and Natural Selection • Environmental change can result in negative growth rates. • Species will go extinct when unable to adapt to such environmental change. • Genetic diversity may buffer populations to environmental change. Deterministic Threats • Change in physical environment – climate change – habitat destruction – pollution • Change in biotic environment – Competition – Predation (including disease and human hunting) – Mutualism Causes of Extinction (Genetic Swamping) Species / Population A Extinction by genetic swamping Hybridization Species B’ Species / Population B Time Environmental Variation 4000 Number of flower heads 3500 3000 2500 2000 1500 1000 500 0 1974 1977 1980 1983 1986 1989 1992 1995 1998 2001 How might climate change affect this sunflower?