Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York, USA.
Kellogg Biological Station, Michigan State University, Hickory Corners, Michigan, USA.
Mol Ecol. 2022 Dec;31(24):6440-6456. doi: 10.1111/mec.16713. Epub 2022 Oct 17.
Widespread introduced species can be leveraged to investigate the genetic, ecological and adaptive processes underlying rapid evolution and range expansion, particularly the contributions of genetic diversity to adaptation. Rhinella marina, the cane toad, has been a focus of invasion biology for decades in Australia. However, their introduction history in North America is less clear. Here, we investigated the roles of introduction history and genetic diversity in establishment success of cane toads across their introduced range. We used reduced representation sequencing (ddRAD) to obtain 34,000 SNPs from 247 toads in native (French Guiana, Guyana, Ecuador, Panama, Texas) and introduced (Bermuda, southern Florida, northern Florida, Hawai'i, Puerto Rico) populations. Unlike all other cane toad introductions, we found that Florida populations were more closely related to native Central American lineages (R. horribilis), than to native Southern American lineages (R. marina). Furthermore, we found high levels of diversity and population structure in the native range, corroborating suggestions that R. marina is a species complex. We also found that introduced populations exhibit only slightly lower genetic diversity than native populations. Together with demographic analyses, this indicates founding populations of toads in Florida were larger than previously reported. Lastly, within R. marina, only one of 245 putatively adaptive SNPs showed fixed differences between native and introduced ranges, suggesting that putative selection in these introduced populations is based upon existing genetic variation. Our findings highlight the importance of genetic sequencing in understanding biological introductions and hint at the role of standing genetic variation in range expansion.
广泛引入的物种可以被利用来研究遗传、生态和适应性进化和分布范围扩张的过程，特别是遗传多样性对适应性的贡献。甘蔗蟾蜍，作为入侵生物学的研究焦点，已经在澳大利亚存在了几十年。然而，它们在北美的引入历史并不清楚。在这里，我们调查了引入历史和遗传多样性在甘蔗蟾蜍引入分布区建立成功中的作用。我们使用简化基因组测序（ddRAD）从原产于（法属圭亚那、圭亚那、厄瓜多尔、巴拿马、德克萨斯州）和引入（百慕大、佛罗里达州南部、佛罗里达州北部、夏威夷州、波多黎各）种群的 247 只蟾蜍中获得了 34000 个 SNP。与所有其他甘蔗蟾蜍引入不同的是，我们发现佛罗里达州的种群与原产于中美洲的亲缘关系（R. horribilis）比原产于南美洲的亲缘关系（R. marina）更近。此外，我们在原产地区发现了高水平的多样性和种群结构，这证实了 R. marina 是一个物种复合体的观点。我们还发现，引入种群的遗传多样性仅略低于原产种群。结合人口分析，这表明佛罗里达州蟾蜍的引入种群比以前报道的要大。最后，在 R. marina 中，只有 245 个假定适应性 SNP 中的一个在原产和引入范围之间表现出固定差异，这表明这些引入种群中的假定选择是基于现有的遗传变异。我们的研究结果强调了遗传测序在理解生物引入中的重要性，并暗示了遗传变异在分布范围扩张中的作用。
