Genetic analysis of a documented population bottleneck: introduced Bennett’s wallabies (Macropus rufogriseus rufogriseus) in New Zealand

Abstract

Few bottlenecks of wild populations are sufficiently well-documented to constitute models for testing theories about the impact of bottlenecks on genetic variation, and subsequent population persistence. Relevant details of the Bennett's wallaby (Macropus rufogriseus rufogriseus) introduction into New Zealand were recorded (founder number, source and approximate bottleneck duration) and suggest this may provide a rare opportunity to examine the efficacy of tests designed to detect recent bottlenecks in wild populations. We first assessed the accuracy of historic accounts of the introduction using genetic diversity detected in mitochondrial DNA (mtDNA) and at five microsatellite loci. Phylogenetic analyses of mtDNA D-loop sequence haplotypes were consistent with the reported origin of the founders as Tasmania, rather than one of the Bass Strait islands in which Bennett's wallabies are also found. Microsatellite allele frequencies from the Tasmanian source population were then used to seed bottleneck simulations encompassing varying sizes and numbers of generations, in order to assess the severity of bottleneck consistent with diversity observed in the New Zealand population. The results suggested that the founder number was unlikely to have been as small as the three animals suggested by the account of the introduction. Nonetheless, the bottleneck was probably severe; in the range of three to five pairs of wallabies for one to three generations. It resulted in significantly reduced levels of allelic diversity and heterozygosity relative to the source population. This bottleneck is only detectable under the infinite allele model (IAM) and not under the stepwise mutation model (SMM) or the two-phase model (TPM), and possible explanations for this are discussed.

Genetic divergence between island and continental populations of the parasitic nematode Labiosimplex australis in Australia

“…Thus, there has been more time for genetic divergence between Tasmanian and mainland populations of L. australis, in addition to the separation of M. rufogriseus into two subspecies based on morphological, reproductive and genetic differences (Johnston and Sharman 1979;Le Page et al 2000). No sequence differences in the ITS-1 were fixed between the two groups of nematodes, which is consistent with the hypothesis that these parasites represent a single species.…”

First Analysis of Genetic Variability in Carinthian Populations of the White-Clawed Crayfish Austropotamobius Pallipes

“…This assumption would be supported by the low genetic variation found in the present study. Translocation usually involves a limited number of individuals and leads to severe bottlenecks: the consequences in founder populations are decrease of genetic variability and effective population size (LE PAGE et al, 2000;NEI et al, 1975). Hence, such populations are more strongly affected by the action of random processes, like genetic drift, which can promote morphological differentiation.…”

Unregulated hunting and genetic recovery from a severe population decline: the cautionary case of Bulgarian wolves

“…Genetic bottleneck was not confirmed by all tests, but the method used here is known to fail detecting recent bottlenecks in populations that have recovered since the size reduction (Le Page et al 2000;Whitehouse and Harley 2001). Although the 1970s bottleneck can be considered recent (about 13 wolf generations ago, given a mean generation time of 3 years; Mech and Seal 1987), it did not last long, as earlier estimates in 1900 suggests a larger census size of 1,000-1 600 individuals (Spiridonov and Spassov 1985).…”