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Last modified
7/14/2009 5:01:48 PM
Creation date
5/20/2009 11:07:33 AM
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UCREFRP
UCREFRP Catalog Number
9684
Author
Soule, M. E.
Title
Chapter 9 - Thresholds For Survival
USFW Year
n.d.
USFW - Doc Type
Maintaining Fitness and Evolutionary Potential.
Copyright Material
YES
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<br /> <br />SOULE/CHAPTER 9 <br />THRESHOLDS FOR SURVIVAL <br /> <br />events such as drought, disease and other catastrophes from driving frag- <br />mented populations to extinction. <br />Thus, it would appear that with or without management, evolution of <br />large, terrestrial organisms in the fragmenting tropics is all but over. <br />Ironically, the very means at our disposal to protect the large life fonus <br />in the tropics (artificial migration) is the same means that will impose <br />evolutionary stasis. It is sad that the necessary condition for survival it- <br />self contributes to the end of speciation for large organisms. We are wit- <br />nessing (and causing) a biological crisis without precedent. <br /> <br />CONCLUSIONS <br /> <br />The criteria for population size and area proposed in this and accom-. <br />panying chapters (Chapters 8 and 12) should force C some painful reap- <br />praisals of existing and contemplated conservation programs. For <br />example, only a handful of captive breeding programs for birds and mam- <br />mals meet the minimum criteria for short-term fitness, and only a frac- <br />tion of national parks and reserves are of sufficient size to sustain <br />evolutionary viable populations of large animals. Thus, planners are <br />faced with three choices: (1) They can ignore the genetic and evolution- <br />ary criteria (business as usual); (2) They can accept and attempt to im- <br />plement the criteria; and (3) They can decide that it is hopeless and <br />change professions. The latter choice is understandable, especially when <br />one considers the economic and political barriers confronting conserva- <br />tion planners. <br />Perhaps it is some solace that a less than ideal program is b.etter than <br />none at all, assuming it makes the best use of available resources. Unfor- <br />tunately, many existing captive breeding and wildlife conservation pro- <br />grams are failing to achieve even the latter goal. For example, national <br />and individual ambition and pride often prevent the establishment of <br />breeding and management consortia, the implementation of which would <br />significantly increase the effective population sizes of many captive and <br />endangered species. Realistically, in some cases the only solution will be a <br />legislative one-the penalty for uncooperativeness being removal of pre- <br />ferred tax or .licensing status, and the incentive being grants and official <br />recognition. <br />Finally, an apology and a caveat. Some biologists will be appalled by <br />the blanket prescriptions for survival suggested here, especially in view of <br />the heterogeneity in population structure, genetic variability and, proba- <br />bly, in genetic load that exists among species-even closely related ones. <br />Indeed, criteria such as those recommended here lack precision. The ca- <br /> <br />167 <br />
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