Lindholm Anna K, Breden Felix, Alexander Heather J, Chan Woon-Khiong, Thakurta Sumita G, Brooks Robert
School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney 2052, Australia.
Mol Ecol. 2005 Oct;14(12):3671-82. doi: 10.1111/j.1365-294X.2005.02697.x.
High genetic diversity is thought to characterize successful invasive species, as the potential to adapt to new environments is enhanced and inbreeding is reduced. In the last century, guppies, Poecilia reticulata, repeatedly invaded streams in Australia and elsewhere. Quantitative genetic studies of one Australian guppy population have demonstrated high additive genetic variation for autosomal and Y-linked morphological traits. The combination of colonization success, high heritability of morphological traits, and the possibility of multiple introductions to Australia raised the prediction that neutral genetic diversity is high in introduced populations of guppies. In this study we examine genetic diversity at nine microsatellite and one mitochondrial locus for seven Australian populations. We used mtDNA haplotypes from the natural range of guppies and from domesticated varieties to identify source populations. There were a minimum of two introductions, but there was no haplotype diversity within Australian populations, suggesting a founder effect. This was supported by microsatellite markers, as allelic diversity and heterozygosity were severely reduced compared to one wild source population, and evidence of recent bottlenecks was found. Between Australian populations little differentiation of microsatellite allele frequencies was detected, suggesting that population admixture has occurred historically, perhaps due to male-biased gene flow followed by bottlenecks. Thus success of invasion of Australia and high additive genetic variance in Australian guppies are not associated with high levels of diversity at molecular loci. This finding is consistent with the release of additive genetic variation by dominance and epistasis following inbreeding, and with disruptive and negative frequency-dependent selection on fitness traits.
人们认为，高遗传多样性是成功入侵物种的特征，因为这增强了其适应新环境的潜力并减少了近亲繁殖。在上个世纪，孔雀鱼（Poecilia reticulata）多次入侵澳大利亚及其他地区的溪流。对澳大利亚一个孔雀鱼种群的数量遗传学研究表明，常染色体和Y连锁形态性状具有高加性遗传变异。孔雀鱼在澳大利亚的定殖成功、形态性状的高遗传性以及多次引入的可能性，共同引发了这样的预测：引入的孔雀鱼种群中性遗传多样性较高。在本研究中，我们检测了澳大利亚七个种群在九个微卫星位点和一个线粒体位点的遗传多样性。我们利用来自孔雀鱼自然分布区和驯化品种的线粒体DNA单倍型来确定来源种群。至少有两次引入事件，但澳大利亚种群内不存在单倍型多样性，这表明存在奠基者效应。微卫星标记也支持这一点，因为与一个野生来源种群相比，等位基因多样性和杂合性严重降低，并且发现了近期瓶颈效应的证据。在澳大利亚不同种群之间，微卫星等位基因频率几乎没有差异，这表明历史上曾发生过种群混合，可能是由于雄性偏向的基因流随后伴随着瓶颈效应。因此，孔雀鱼在澳大利亚的入侵成功以及澳大利亚孔雀鱼的高加性遗传变异，与分子位点的高多样性水平并无关联。这一发现与近亲繁殖后显性和上位性作用导致的加性遗传变异释放，以及对适合度性状的干扰性和负频率依赖选择是一致的。
