Tarvin Rebecca D, Powell Emily A, Santos Juan C, Ron Santiago R, Cannatella David C
Department of Integrative Biology and Biodiversity Collections, University of Texas, Austin, TX, United States.
Department of Integrative Biology and Biodiversity Collections, University of Texas, Austin, TX, United States; Department of Biology, University of Miami, Miami, FL, United States.
Mol Phylogenet Evol. 2017 Apr;109:283-295. doi: 10.1016/j.ympev.2016.12.035. Epub 2017 Jan 13.
Rapid radiation coupled with low genetic divergence often hinders species delimitation and phylogeny estimation even if putative species are phenotypically distinct. Some aposematic species, such as poison frogs (Dendrobatidae), have high levels of intraspecific color polymorphism, which can lead to overestimation of species when phenotypic divergence primarily guides species delimitation. We explored this possibility in the youngest origin of aposematism (3-7 MYA) in poison frogs, Epipedobates, by comparing genetic divergence with color and acoustic divergence. We found low genetic divergence (2.6% in the 16S gene) despite substantial differences in color and acoustic signals. While chemical defense is inferred to have evolved in the ancestor of Epipedobates, aposematic coloration evolved at least twice or was lost once in Epipedobates, suggesting that it is evolutionarily labile. We inferred at least one event of introgression between two cryptically colored species with adjacent ranges (E. boulengeri and E. machalilla). We also find evidence for peripheral isolation resulting in phenotypic divergence and potential speciation of the aposematic E. tricolor from the non-aposematic E. machalilla. However, we were unable to estimate a well-supported species tree or delimit species using multispecies coalescent models. We attribute this failure to factors associated with recent speciation including mitochondrial introgression, incomplete lineage sorting, and too few informative molecular characters. We suggest that species delimitation within young aposematic lineages such as Epipedobates will require genome-level molecular studies. We caution against relying solely on DNA barcoding for species delimitation or identification and highlight the value of phenotypic divergence and natural history in delimiting species.
即使假定的物种在表型上存在差异，快速辐射与低遗传分化通常也会阻碍物种界定和系统发育估计。一些具有警戒色的物种，如箭毒蛙（树棘蛙科），具有高水平的种内颜色多态性，当表型差异主要用于指导物种界定时，这可能导致对物种的高估。我们通过比较遗传分化与颜色和声学分化，在箭毒蛙属（Epipedobates）中最年轻的警戒色起源（300 - 700万年前）中探讨了这种可能性。尽管颜色和声学信号存在显著差异，但我们发现遗传分化程度较低（16S基因中为2.6%）。虽然推断化学防御在箭毒蛙属的祖先中已经进化，但警戒色在箭毒蛙属中至少进化了两次或消失过一次，这表明它在进化上是不稳定的。我们推断在两个相邻分布的隐性色物种（E. boulengeri和E. machalilla）之间至少发生了一次基因渗入事件。我们还发现了周边隔离导致表型分化以及来自非警戒色的E. machalilla的警戒色E. tricolor潜在物种形成的证据。然而，我们无法使用多物种溯祖模型估计得到一个有充分支持的物种树或界定物种。我们将这种失败归因于与近期物种形成相关的因素，包括线粒体基因渗入、不完全谱系分选以及信息性分子特征过少。我们建议，在像箭毒蛙属这样年轻的警戒色谱系中进行物种界定将需要基因组水平的分子研究。我们提醒不要仅依赖DNA条形码进行物种界定或识别，并强调表型差异和自然史在界定物种中的价值。
