Speciation in the genus Stevia of Mexico and Brazil

现代植物系统学的一个有趣的挑战是建立一个综合的案例研究，为一个特定的植物群体，显示出显着的适应性分歧，通过重建的系统发育关系之间的几乎所有物种的组。甜菊属（菊科;墨西哥泽兰族（Eupatorieae）在生活史性状和生殖系统上存在着极高的分化，为此类研究提供了很好的机会。该项目的目的是通过在墨西哥和巴西进行一系列实地考察来收集回答这些问题的材料。（1）极多态性的甜菊种究竟是单一的生物种还是多个隐蔽种的复合体？(2)Is巴西有无花受精多倍体吗？（3）墨西哥和巴西的物种是如何相互联系的？为了回答问题（1），我们进行了实地调查， ...更多信息 杜兰戈州、哈利斯科州、米霍坎州、格雷罗州和瓦哈卡州。结果表明，在五个不同的地区，同时出现了两个以上的隐性二倍体物种。AFLP分析结果表明，两对隐种中有1对是由于适应不同生境环境条件而发生分化的，而两对不同生境中的隐种则是在有性生殖基础上发生分化的。为了回答问题（2），我们在巴西的圣保罗、圣卡塔里纳和南里奥格兰德州进行了实地调查。对收集的材料进行细胞学检查，发现巴西所有甜菊属物种都是有性二倍体。为了回答问题（3），我们利用ITS序列构建了墨西哥和巴西甜菊属物种的系统发育树。结果表明，巴西种是墨西哥甜菊的一个分支。少

An interesting challenge in modem plant systematics is to establish a synthetic case study for a particular group of plants that shows conspicuous adaptive divergence by reconstructing a phylogenetic relationship among almost all species of the group. The genus Stevia (Asteraceae; Eupatorieae) provides a good opportunity for such study because it contains extremely high divergence in life histry traits and reproductive systems.We already studied phylogenetic relationship among Mexican species, but the following questions remain unanswered. The purpose of this project was to collect materials for answering these questions by carrying out a series of field expecitions in Mexico and Brazil.(1)Whether an extremely polymorphic species Stevia origanoides is a single biological species or a complex of some cryptic species?(2)Is there any agamospermous polyploidy in Brazil?(3)How Mexican and Brazilian species are related to each other?To answer the question (1), we carried out field surveys in … More Durango, Jalisco, Michoacan, Guerrero and Oaxaca states of Mexico. As a results, co-occurrence of more than two cryptic diploid species was observed in five different areas. AFLP analysis showed that of two pairs of cryptic species were recently diverged as a result of adaptation to different environmental conditions of rocky habitats while two cryptic species in distinct ecological habitats were diverged at the base of phylogeny. These findings suggest that Stevia origanoides sensu lato continued to diverge to different environmental conditions since its origin.To answer the question (2), we carried out field surveys in Sao Paulo, Santa Catarina, and Rio Grande do Sul states of Brazil. Cytological examinations of the materials collected revealed that all species of Stevia in Brazil were sexual diploidsTo answer the question (3), we constructed a phylogenetic tree of Mexican and Brazilian species of Stevia by using ITS sequences. The results showed that Brazilian species is a branch of Mexican Stevia. Less