Martin Christopher H, Feinstein Laura C
Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA, 94720, USA; Department of Evolution & Ecology, University of California, Davis, CA, 94616, USA.
Mol Ecol. 2014 Apr;23(7):1846-62. doi: 10.1111/mec.12658. Epub 2014 Feb 17.
Adaptive radiation is recognized by a rapid burst of phenotypic, ecological and species diversification. However, it is unknown whether different species within an adaptive radiation evolve reproductive isolation at different rates. We compared patterns of genetic differentiation between nascent species within an adaptive radiation of Cyprinodon pupfishes using genotyping by sequencing. Similar to classic adaptive radiations, this clade exhibits rapid morphological diversification rates and two species are novel trophic specialists, a scale-eater and hard-shelled prey specialist (durophage), yet the radiation is <10 000 years old. Both specialists and an abundant generalist species all coexist in the benthic zone of lakes on San Salvador Island, Bahamas. Based on 13 912 single-nucleotide polymorphisms (SNPs), we found consistent differences in genetic differentiation between each specialist species and the generalist across seven lakes. The scale-eater showed the greatest genetic differentiation and clustered by species across lakes, whereas durophage populations often clustered with sympatric generalist populations, consistent with parallel speciation across lakes. However, we found strong evidence of admixture between durophage populations in different lakes, supporting a single origin of this species and genome-wide introgression with sympatric generalist populations. We conclude that the scale-eater is further along the speciation-with-gene-flow continuum than the durophage and suggest that different adaptive landscapes underlying these two niche environments drive variable progress towards speciation within the same habitat. Our previous measurements of fitness surfaces in these lakes support this conclusion: the scale-eating fitness peak may be more distant than the durophage peak on the complex adaptive landscape driving adaptive radiation.
适应辐射以表型、生态和物种多样化的快速爆发为特征。然而，尚不清楚适应辐射中的不同物种是否以不同速率进化出生殖隔离。我们使用测序基因分型法比较了鲤齿鳉属食蚊鱼适应辐射中新生物种之间的遗传分化模式。与经典的适应辐射相似，这个进化枝表现出快速的形态多样化速率，有两个物种是新的营养特化物种，一个是食鳞者和硬壳猎物特化物种（食硬壳动物），然而这种辐射的历史还不到10000年。这两个特化物种和一个数量丰富的泛化物种都共存于巴哈马圣萨尔瓦多岛湖泊的底栖区域。基于13912个单核苷酸多态性（SNP），我们发现在七个湖泊中，每个特化物种与泛化物种之间在遗传分化上存在一致差异。食鳞者表现出最大的遗传分化，并且在不同湖泊中按物种聚类，而食硬壳动物种群通常与同域泛化种群聚类，这与不同湖泊间的平行物种形成一致。然而，我们发现了不同湖泊中食硬壳动物种群之间存在混合的有力证据，支持该物种的单一起源以及与同域泛化种群的全基因组渗入。我们得出结论，食鳞者在物种形成与基因流连续统上比食硬壳动物更进了一步，并表明这两种生态位环境下不同的适应景观驱动了同一栖息地内物种形成的不同进展。我们之前对这些湖泊适应度表面的测量支持了这一结论：在驱动适应辐射的复杂适应景观上，食鳞者的适应度峰值可能比食硬壳动物的峰值距离更远。
