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• W31421004 abstract "The present distribution of extant species has been influenced by historical eventsof habitat change that can have an effect on cause population sizes and distribution.These types of fluctuations often have had an effect on the genetic makeup ofpopulations. Although the effects of past climatic changes are well documented fortemperate environments, these are relatively less clear for the tropics. In this study Ianalyse mitochondrial DNA control region variation in the Gouldian Finch (Erythruragouldiae), a species endemic to the Australian tropical savannas that has experienceddrastic population declines in recent times. Results show a lack of lineagedifferentiation between individuals across the present distribution of this species, and atotal lack of genetic diversity for a population that is part of a captive breeding andreintroduction program. Analyses of mismatch distributions fit predictions of populationgrowth consistent with range expansions, dating during the Holocene period fromapproximately 7000 to 3600 years before present. Differences in mismatch distributionsbetween separate geographical regions suggest population expansion events happenedat different times in different regions. This gradual colonisation of northern Australiacan be explained in terms of important climatic and socio-cultural changes during theHolocene that were favourable for the growth of E. gouldiae populations. The apparentlack of genetic differentiation between populations from different geographical regions,and the relatively low sequence divergence suggest a recent colonisation of the tropicalSavannas by E. gouldiae. Implications of these results for current management practicesaimed to recover E. gouldiae populations are discussed.Species that have experienced population reductions are expected to be at higherextinction risk because of loss of genetic diversity. This can have deleteriousconsequences for population survival and reduce the potential of such populations torespond to environmental change. Such deleterious effects can be reduced by highlevels of migration that contribute to the maintenance of genetic diversity. The GouldianFinch (Erythrura gouldiae) has experienced recent population reductions that haveresulted in its endangerment. In order to provide effective management aimed toachieve the recovery of an endangered species, it is necessary to investigate the geneticvariation in this species.In this study I investigate genetic variation, population structure and gene flow inGouldian Finch populations, and contrast such patterns with those of the sympatric andabundant Long-tailed finch (Poephila acuticauda). Heterozygosity is slightly higher inP. acuticauda than in E. gouldiae. There was no evidence of recent severe geneticbottlenecks and the indicators of intra-population inbreeding (f) were relatively low inboth species. Inter-population differentiation (θII) was moderate for both species.Significantly lower heterozygosity and evidence of a recent population bottleneckwas found for a captive population of E. gouldiae that is part of a reintroductionprogram in north-east Australia.There was evidence of population structuring between P. acuticauda populations,while E. gouldiae shows no sign of population structure. The lack of geneticdifferentiation in E. gouldiae can be partly explained by relatively higher migrationrates compared to P. acuticauda.Genes of the Major Histocompatibility Complex (MHC) have an important role inpathogen recognition and the initiation of the immune response. MHC genes are amongthe most variable genes in vertebrates. Their high diversity is thought to be maintainedby gene duplication, balancing selection and gene conversion. I investigated thevariability of MHC class IIβ genes of the endangered Gouldian Finch (Erythruragouldiae) and the sympatric and relatively abundant Long-tailed Finch (Poephilaacuticauda). I looked for evidence for the presence of gene conversion events betweenhaplotypes, in order to determine its relative importance on the maintenance of geneticvariability in these two species, and calculated dN/dS (the ratio of non-synonymous tosynonymous substitution rates) as an indication of the relative strength of selection atthis gene.Erythrura gouldiae had an apparently lower variability at MHC class II genesthan P. acuticauda. Gene conversion events between haplotypes were detected in bothspecies, being more prevalent in E. gouldiae than in P. acuticauda. This indicates thatgene conversion has been relatively more important in the maintenance of geneticvariability of MHC genes in E. gouldiae. Evidence of positive selection at MHC class IIgenes was found for both species. The patterns of positive selection at the amino-acidlevel appear roughly similar between both species, although in some cases I foundpositions that are under purging selection in E. gouldiae, while in P. acuticauda areunder strong positive selection.Differences found between both species in variability of MHC genes, theprevalence of gene conversion events and the rates of positive selection may reflectpossible differences in evolutionary pressures caused by pathogens in each species." @default.
• W31421004 created "2016-06-24" @default.
• W31421004 creator A5030039823 @default.
• W31421004 date "2008-07-01" @default.
• W31421004 modified "2023-09-27" @default.
• W31421004 title "Molecular ecology of the endangered Gouldian Finch Erythrura gouldiae" @default.
• W31421004 hasPublicationYear "2008" @default.
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