Large variations in the ratio of effective breeding and census population sizes between two species of pond-breeding anurans |
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Authors: | EDWARD G BREDE TREVOR J C BEEBEE |
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Institution: | School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QG, UK |
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Abstract: | The viability of wild populations is frequently assessed by monitoring adult census sizes ( N c). This approach is particularly useful for pond-breeding amphibians, because assemblages during the breeding season are relatively easy to detect and count. However, it is the genetic effective population size ( N e) or surrogates such as effective breeding population size ( N b) that are of primary importance for long-term viability. Although N c estimates of one anuran amphibian ( Bufo bufo ) in Britain were much larger than those of another ( Rana temporaria ) at the same sites, the ratios of N b to N c were much smaller in B. bufo than in R. temporaria. These differences were sufficiently great as to reverse the effective size order at one site, such that N b for R. temporaria was larger than that for B. bufo. Differences in adult sex ratios at breeding sites probably contributed to lower N b values in B. bufo populations compared with those of R. temporaria . The relationship of N b to N c can therefore vary dramatically even between similar species, to the extent that just monitoring N c can give misleading impressions of relative effective breeding sizes and thus of population viability. It will be increasingly important to estimate N e or N b in wildlife populations for assessment of conservation priorities. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 365–372. |
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Keywords: | amphibian census size effective size microsatellites sex ratio |
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