Endemism, invasion, and overseas dispersal: The phylogeographic history of the Lesser Antillean frog, Eleutherodactylus johnstonei

Cryptogenic species, those whose native and introduced ranges are unknown, pose a challenge not only to conservation but also to studies of ecology, biogeography, and evolution. One such species is the Lesser Antillean frog, Eleutherodactylus johnstonei, which is broadly distributed through the Caribbean and mainland South America. The Lesser Antilles pose a particular challenge with regard to cryptogenic species because these islands have been anthropogenically connected since before recorded history. We combined genetic (available on Genbank) and morphological data to infer the native and introduced ranges of this species. We inferred the insland of Montserrat as the native range of E. johnstonei. Furthermore, we identified two major clades of E. johnstonei, only one of which is responsible for the widespread introduced range. Based on previous suggestions that body size differed across the range of E. johnstonei, we collected snout-urostyle length from 98 females and 582 males throughout the range. We found that female body size did not differ between clades. Although maximum male body size did not differ, on avergae males were larger in the eastern clade comrpising the bulk of introduced localities. Our results demonstrate the utility of population and phylogeographic tools in resolving the cryptogenic species problem.

隐存起源物种（cryptogenic species）指其原生分布区与入侵分布区均尚未明确的类群，此类物种不仅对生物保护工作构成挑战，也为生态学、生物地理学及进化生物学研究带来了难题。其中一例便是小安的列斯蛙（Eleutherodactylus johnstonei），该物种广泛分布于加勒比海区域与南美大陆。小安的列斯群岛在隐存起源物种研究方面面临特殊困境，原因在于该群岛早在有文字记载的历史之前，便已通过人类活动实现了相互连通。本研究结合了可从GenBank数据库获取的基因数据与形态学数据，以此推断该物种的原生分布区与入侵分布区。最终我们确定蒙特塞拉特岛为该物种的原生分布区。此外，我们鉴定出该物种存在两个主要演化支，其中仅有一个演化支造就了其广泛分布的入侵范围。基于此前关于该物种分布范围内体型存在差异的相关研究推测，我们在其整个分布区内采集了98只雌性与582只雄性个体的吻肛长（snout-urostyle length）数据。分析结果显示，不同演化支间雌性个体的体型并无显著差异；尽管雄性个体的最大体型在不同演化支间未表现出差异，但平均而言，构成绝大多数入侵分布点位的东部演化支内的雄性个体体型更大。本研究结果证实了种群遗传学与系统地理学工具在解决隐存起源物种相关难题方面的应用价值。