5 - Population Persistance

M525 bio 3115 universit dottawa university of ottawa

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Unformatted text preview: Population bottleneck 50 25 0 1960 1970 1980 1990 Year M5.26 Bio 3115 Université d’Ottawa / University of Ottawa M5 2009-2010.13 BIO 3115 Conservation Biology Current status Currently, males exhibit a high frequency of nonfunctional sperm. Over the last 8 years, this has resulted in reduced reproductive success. Current levels of genetic variability very low. Population reduced to several dozen animals in mid 2000s. Ngorongoro lions are at high extinction risk. M5.27 Bio 3115 Université d’Ottawa / University of Ottawa Area 1 optimum Populations of the same species from different geographic areas (area 1, 2) are locally adapted … Outbreeding depression results from hybridization between individuals from geographically separate and genetically distinct populations Hybrid offspring are not welladapted to local conditions, resulting in increased offspring and juvenile mortality Area 2 optimum Frequency Outbreeding depression Hybrid poorly adapted to both areas Character value M5.28 Bio 3115 Université d’Ottawa / University of Ottawa M5 2009-2010.14 BIO 3115 Conservation Biology Outbreeding depression: the sad case of the Tatra ibex As a result of overhunting, Ibex (Capra ibex) became extinct locally in the Tatra Mountains in Czechoslovakia Animals successfully transplanted from Austria, but importing animals from Turkey and the Sinai resulted in hybrids rutting in the early fall (instead of winter) and offspring born in mid-winter … …resulting in massive reproductive failure and local extinction M5.29 Bio 3115 Université d’Ottawa / University of Ottawa Immigration and genetic variability Movement of individuals between populations (and incorporation into breeding population) tends to reduce genetic variability among populations (D) but increase variability within populations. D12 H1 H2 D23 D13 H3 HT D H M5.30 Bio 3115 Université d’Ottawa / University of Ottawa M5 2009-2010.15 BIO 3115 Conservation Biology The role of immigration in maintaining genetic variability in U.S. Grizzly bear populations In 1975, grizzly bear was declared to be a threatened species in USA (population declined in 48 states from c. 100,000 in 1800 to <1,000 in 1975); Current range is now 1% of historical range; The range reduction resulted in isolation of 6 1922 subpopulations 1992 M5.31 Bio 3115 Université d’Ottawa / University of Ottawa Grizzly Bear (Ursus arctos) in the continental U.S. Question: are the 6 subpopulations genetically viable? Answer: determine the minimum population size required to maintain current levels of genetic diversity Ne of grizzly bears is about 25% of censused population Simulation modeling established that even 200 individuals may be vulnerable to loss of genetic variation, but that exchange of bears among subpopulations may alleviate much of the problem! M5.32 Bio 3115 Université d’Ottawa / University of Ottawa M5 2009-2010.16 BIO 3115 Conservation Biology % original variation remaining The role of immigration in maintaining genetic variability in g...
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