Department of Biology and Whitney R. Harris World Ecology Center, University of Missouri-St. Louis, One University Boulevard, 223 Research Building, Saint Louis, MO 63121, USA.
Mol Phylogenet Evol. 2012 May;63(2):244-54. doi: 10.1016/j.ympev.2011.10.023. Epub 2012 Feb 12.
The Galápagos archipelago has never been connected to any continental land masses, so it is of interest to know the colonization and diversification history of its endemic species. We analyzed the phylogenetic placement of the endemic Galápagos flycatcher, M. magnirostris, within Myiarchus by using the genes ND2 and cytb (1970 bp) to compare 16 of the 22 species that comprise this genus. We also analyzed variability in cytb sequences from 154 M. magnirostris individuals captured on seven Galápagos islands. Our phylogenetic analyses recovered the two main Myiarchus clades that had been described by previous genetic, morphological, and vocal analyses. M. magnirostris is monophyletic and its closest living relative is M. tyrannulus from Mexico and Central America. The average age for the split node between these two groups was approximately 850,000 years (95% C.I. 630,735-1,087,557). M. tyrannulus, M. nugator, M. nuttingi, M. sagrae, and M. stolidus are not monophyletic species. Within M. magnirostris itself, we found low nucleotide and haplotype diversities (π=0.0009 and h=0.4913, respectively) and a high genetic structure among populations. We also detected a star-shaped haplotype network and significantly negative values for Tajima's D and Fu's Fs for this species. Our results suggest that M. magnirostris originated from a single colonization event and had a recent population expansion in the Galápagos archipelago.
加拉帕戈斯群岛从未与任何大陆地块相连，因此了解其特有物种的殖民和多样化历史很有意义。我们分析了特有加拉帕戈斯雀、M. magnirostris 在 Myiarchus 中的系统发育位置，使用了 ND2 和 cytb 基因（1970bp）来比较组成该属的 22 种中的 16 种。我们还分析了从七个加拉帕戈斯群岛捕获的 154 只 M. magnirostris 个体的 cytb 序列的变异性。我们的系统发育分析恢复了以前遗传、形态和声音分析描述的两个主要 Myiarchus 分支。M. magnirostris 是单系的，其最接近的现存亲缘关系是来自墨西哥和中美洲的 M. tyrannulus。这两个群体之间的分裂节点的平均年龄约为 850,000 年（95%置信区间为 630,735-1,087,557）。M. tyrannulus、M. nugator、M. nuttingi、M. sagrae 和 M. stolidus 不是单系物种。在 M. magnirostris 本身内部，我们发现核苷酸和单倍型多样性较低（π=0.0009 和 h=0.4913），并且种群之间存在高度的遗传结构。我们还检测到该物种的星状单倍型网络和 Tajima 的 D 和 Fu 的 Fs 的显著负值。我们的结果表明，M. magnirostris 起源于一次单一的殖民事件，并在加拉帕戈斯群岛经历了近期的种群扩张。
