Wagner Catherine E, McCune Amy R
Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York 14853, USA.
Evolution. 2009 May;63(5):1312-26. doi: 10.1111/j.1558-5646.2009.00612.x. Epub 2009 Jan 14.
The cichlid fish of Lake Tanganyika in Eastern Africa are a celebrated example of both ecological and species diversification. Because population subdivision is likely to play an important role in the speciation process, understanding how habitat features interact with species' demographic, behavioral and ecological attributes to influence gene flow and population divergence may help explain the causes of high species richness in this and other systems. Here, we test the roles of isolation-by-habitat and isolation-by-distance in generating fine-scale population genetic structure in three sympatric species of habitat-restricted cichlids in Lake Tanganyika. Using multilocus microsatellite genotypes, we contrast patterns of population differentiation in these habitat specialists along a mosaic coastline of both favorable and unfavorable habitat. Despite their close phylogenetic relationship and shared habitat affinity, these species show striking differences in their pattern of genetic subdivision within the same geographical region, suggesting substantially different patterns of gene flow. In particular, two trophically specialized species exhibit much more restricted gene flow over sandy habitat than a trophically opportunistic species. This result suggests that ecological and behavioral traits have a strong influence on the scale and degree of population subdivision, a finding that has potentially important implications for understanding differential propensities for diversification among lineages and phylogenetic patterns of diversity.
东非坦噶尼喀湖的丽鱼科鱼类是生态和物种多样化的著名典范。由于种群细分可能在物种形成过程中发挥重要作用，了解栖息地特征如何与物种的种群统计学、行为和生态属性相互作用以影响基因流动和种群分化，可能有助于解释该系统以及其他系统中物种丰富度高的原因。在此，我们测试了栖息地隔离和距离隔离在坦噶尼喀湖三种栖息地受限的同域丽鱼科物种形成精细尺度种群遗传结构中的作用。利用多位点微卫星基因型，我们对比了这些栖息地特化物种在有利和不利栖息地镶嵌的海岸线上的种群分化模式。尽管它们有着密切的系统发育关系和共同的栖息地亲和力，但这些物种在同一地理区域内的遗传细分模式却存在显著差异，这表明基因流动模式有很大不同。特别是，两个营养特化物种在沙质栖息地的基因流动比一个营养机会主义物种受到的限制要大得多。这一结果表明，生态和行为特征对种群细分的规模和程度有很强的影响，这一发现对于理解不同谱系间多样化的差异倾向以及多样性的系统发育模式具有潜在的重要意义。
