Schiffer Michele, Gilchrist A Stuart, Hoffmann Ary A
Centre for Environmental Stress and Adaptation Research, La Trobe University, Victoria, Australia.
Evolution. 2006 Jan;60(1):106-14.
Divergence among populations can occur via additive genetic effects and/or because of epistatic interactions among genes. Here we use line-cross analysis to compare the importance of epistasis in divergence among two sympatric Drosophila species from eastern Australia, one (D. serrata) distributed continuously and the other (D. birchii) confined to rainforest habitats that are often disjunct. For D. serrata, crosses indicated that development time and wing size differences were due to additive genetic effects, while for viability there were digenic epistatic effects. Crosses comparing geographically close populations as well as those involving the most geographically distant populations (including the southern species border) revealed epistatic interactions, whereas crosses at an intermediate distance showed no epistasis. In D. birchii, there was no evidence of epistasis for viability, although for development time and wing size there was epistasis in the cross between the most geographically diverged populations. Strong epistasis has not developed among the D. birchii populations, and this habitat specialist does not show stronger epistasis than D. serrata. Given that epistasis has been detected in crosses with other species from eastern Australia, including the recently introduced D. melanogaster, the results point to epistasis not being directly linked to divergence times among populations.
种群间的差异可通过加性遗传效应和/或基因间的上位性相互作用产生。在这里，我们使用品系杂交分析来比较上位性在来自澳大利亚东部的两个同域果蝇物种分化中的重要性，其中一个物种（锯果蝇）连续分布，另一个物种（伯氏果蝇）局限于通常间断分布的雨林栖息地。对于锯果蝇，杂交表明发育时间和翅大小差异是由加性遗传效应引起的，而对于存活力则存在双基因上位性效应。比较地理距离相近的种群以及涉及地理距离最远的种群（包括南部物种边界）的杂交显示出上位性相互作用，而中等距离的杂交则未显示上位性。在伯氏果蝇中，没有证据表明存活力存在上位性，尽管对于发育时间和翅大小，在地理分化最大的种群之间的杂交中存在上位性。伯氏果蝇种群之间尚未形成强烈的上位性，并且这种栖息地特化物种并未表现出比锯果蝇更强的上位性。鉴于在与来自澳大利亚东部的其他物种（包括最近引入的黑腹果蝇）的杂交中检测到了上位性，结果表明上位性与种群间的分化时间没有直接联系。
