ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD 4811, Australia.
Mol Ecol. 2011 Sep;20(17):3584-98. doi: 10.1111/j.1365-294X.2011.05207.x. Epub 2011 Aug 2.
The vulnerability of ecologically specialised species to environmental fluctuations has been well documented. However, population genetic structure can influence vulnerability to environmental change and recent studies have indicated that specialised species may have lower genetic diversity and greater population structuring compared to their generalist counterparts. To examine whether there were differences in population genetic structure between a dietary specialist (Chaetodon trifascialis) and a dietary generalist (Chaetodon lunulatus) we compared the demographic history and levels of gene flow of two related coral-feeding butterflyfishes. Using allele frequencies of ≥11 microsatellite loci and >350 bases of mitochondrial control region sequence our analyses of C. trifascialis and C. lunulatus from five locations across the Pacific Ocean revealed contrasting demographic histories and levels of genetic structure. Heterozygosity excess tests, neutrality tests and mismatch distributions were all highly significant in the dietary specialist C. trifascialis (all P < 0.01), suggesting genetic bottlenecks have occurred in all locations. In contrast, we found little evidence of genetic bottlenecks for the dietary generalist C. lunulatus. High gene flow and low genetic structuring was detected among locations for C. trifascialis (amova: R(ST) = 0.0027, P = 0.371; Φ(ST) = 0.068, P < 0.0001). Contrary to our expectations, a greater level of genetic structuring between locations was detected for C. lunulatus (amova: R(ST) = 0.0277, Φ(ST) = 0.166, both P < 0.0001). These results suggest that dietary specialisation may affect demographic history through reductions in population size following resource declines, without affecting population structure through reductions in gene flow in the same way that habitat specialisation appears to. Although C. trifascialis is highly vulnerable to coral loss, the high gene flow detected here suggests populations will be able to recover from local declines through the migration of individuals.
生态特化物种对环境波动的脆弱性已有充分记录。然而，种群遗传结构会影响对环境变化的脆弱性，最近的研究表明，与广食性物种相比，特化物种的遗传多样性可能较低，种群结构可能更大。为了研究食性专化的 Chaetodon trifascialis 和食性广化的 Chaetodon lunulatus 之间的种群遗传结构是否存在差异，我们比较了两种相关的珊瑚食性蝴蝶鱼的种群历史和基因流动水平。使用≥11 个微卫星基因座的等位基因频率和>350 个线粒体控制区序列碱基对，我们对来自太平洋五个地点的 C. trifascialis 和 C. lunulatus 的分析揭示了截然不同的种群历史和遗传结构水平。在食性专化的 C. trifascialis 中，杂合过量检验、中性检验和不匹配分布均高度显著（所有 P<0.01），表明所有地点都发生了遗传瓶颈。相比之下，我们发现食性广化的 C. lunulatus 几乎没有遗传瓶颈的证据。在 C. trifascialis 中，各地点之间检测到高基因流动和低遗传结构（amova：R(ST)=0.0027，P=0.371；Φ(ST)=0.068，P<0.0001）。与我们的预期相反，在 C. lunulatus 中，各地点之间的遗传结构水平更高（amova：R(ST)=0.0277，Φ(ST)=0.166，两者 P<0.0001）。这些结果表明，食性特化可能会通过资源减少导致的种群数量减少来影响种群历史，而不会像栖息地特化那样通过减少基因流动来影响种群结构。尽管 C. trifascialis 对珊瑚礁丧失高度敏感，但这里检测到的高基因流动表明，通过个体的迁移，种群将能够从局部减少中恢复。
