在季节性干燥的热带森林(SDTF)中,对南美生物多样性的进化史研究甚少。这个生态系统中的物种多样化可能有双重解释。首先,更新世中晚期的间歇性连接促进了物种的扩散和/或在森林分离斑块中分离的谱系之间的遗传连接。第二,SDTF在新近纪中形成和定殖后,立即进行了同种异体物种形成。在这里,我们研究了Psammolestes的多样化,SDTF属,自然感染克氏锥虫(恰加斯病的病原体),使用系统发育的组合,种群遗传学和生态位模型方法,并评估了目前公认的三种形态物种的可靠性。
我们的多位点分析恢复了P.arthuri的单系进化枝姐妹中的P.coreodes和P.tertius。尽管在五个基因中观察到P.coreodes和P.tertius之间存在共同的遗传变异,但物种定界测试将这些谱系恢复为不同的物种。此外,该属的遗传变异集中在与三个形态种一致的三个群体中。我们的人口统计学模型预测了没有基因流动的情况下的分歧,这表明混合单倍型可能是由于亚热带温带物种P.coreodes和P.tertius的分歧而导致的共同祖先变异的结果。相比之下,在所有遗传结构测试中,热带物种arthuri与其他两个物种高度不同,并且始终如一,Monmonier的算法确定了一个清晰的地理屏障,将该物种与P.corodes和P.tertius分开。
我们在Psammolestes中发现了三个遗传结构的谱系,这些谱系在上世纪晚期没有基因流的情况下发生了分歧。该结果支持了由地理隔离而不是面对与更新世气候振荡相关的基因流动的分歧所驱动的物种形成的情景。此外,我们认为亚马逊盆地是将热带和亚热带温带物种分开的气候屏障,从而促进远距离分散后的异方形态形成。最后,Psammolestes的每个物种占据不同的气候生态位,这表明生态位保守主义对于物种分化并不重要。这些发现影响了该地区当前的查加斯病媒介监测计划。
The evolutionary history of biodiversity in South America has been poorly studied in the seasonal dry tropical forest (SDTF). Species diversification in this ecosystem may have a twofold explanation. First, intermittent connections in the middle and late Pleistocene promoted species dispersal and/or genetic connectivity between lineages isolated in disjunct patches of forest. Second, allopatric speciation proceeded immediately after the formation and colonization of the SDTF in the Neogene. Here we studied the diversification of Psammolestes, a genus endemic of the SDTF and naturally infected with Trypanosoma cruzi (agent of Chagas disease), using a combination of phylogenetic, population genetics and niche model methods, and evaluated the reliability of the three morphospecies currently recognized.
Our multilocus analyses recovered P. coreodes and P. tertius in a monophyletic clade sister to P. arthuri. Species delimitation tests recovered these lineages as different species despite the shared genetic variation observed between P. coreodes and P. tertius in five genes. Also, genetic variation of the genus clustered in three groups that were consistent with the three morphospecies. Our demographic model predicted a scenario of divergence in absence of gene flow, suggesting that mixed haplotypes may be the result of shared ancestral variation since the divergence of the subtropical-temperate species P. coreodes and P. tertius. In contrast, the tropical species P. arthuri was highly differentiated from the other two in all tests of genetic structure, and consistently, the Monmonier\'s algorithm identified a clear geographical barrier that separates this species from P. coreodes and P. tertius.
We found three genetically structured lineages within Psammolestes that diverged in absence of gene flow in the late Miocene. This result supports a scenario of species formation driven by geographical isolation rather than by divergence in the face of gene flow associated with climatic oscillations in the Pleistocene. Also, we identified the Amazon basin as a climatic barrier that separates tropical from subtropical-temperate species, thus promoting allopatric speciation after long range dispersion. Finally, each species of Psammolestes occupies different climatic niches suggesting that niche conservatism is not crucial for species differentiation. These findings influence the current vector surveillance programs of Chagas disease in the region.