Serial population bottlenecks and genetic variation: Translocated populations of the New Zealand Saddleback (Philesturnus carunculatus rufusater)
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The genetic effects of population bottlenecks have been well studied theoretically, in laboratory studies, and to some extent, in natural situations. The effects of serial population bottlenecks (SPBs), however, are less well understood. This is significant because recurrent population bottlenecks are likely to be a common feature of the life history of many species. The lack of understanding of SPBs in natural populations has certainly been hampered by a lack of good examples where it can be studied. We report the results of a study into island populations of North Island Saddleback (Philesturnus carunculatus rufusater) that have undergone 13 translocations since 1964, all but one of these has been deliberate and for which detailed records are available. We have examined nine island populations of this passerine bird, from the source population, three first-order bottlenecked and five second-order bottlenecked populations. We examine variation in these nine populations using multilocus minisatellite DNA markers, together with Mendelian loci comprising six microsatellite DNA loci and a variable isozyme locus. Despite the generally low level of genetic variation in the Saddleback source population, we were able to detect a pattern of significant changes in both the mean number of minisatellite DNA bands per individual and the frequency of alleles at the Mendelian loci, with increasing population bottlenecks. This study generally shows that in a natural population, SPBs result in more pronounced genetic changes than do single population bottlenecks by themselves, thereby highlighting their importance for the conservation of rare and endangered species.