Department of Biology, University of Central Florida, Orlando, FL 32816, USA.
Department of Biology, University of Tampa, Tampa, FL 33606, USA.
Integr Comp Biol. 2022 Aug 25;62(2):262-274. doi: 10.1093/icb/icac044.
Maintenance of genetic diversity at adaptive loci may facilitate invasions by non-native species by allowing populations to adapt to novel environments, despite the loss of diversity at neutral loci that typically occurs during founder events. To evaluate this prediction, we compared genetic diversity at major histocompatibility complex (MHC) and cytochrome b (cytb) loci from 20 populations of the American bullfrog (Rana catesbeiana) across theinvasive and native ranges in North America and quantified the presence of the pathogen Batrachochytrium dendrobatidis (Bd). Compared to native populations, invasive populations had significantly higher Bd prevalence and intensity, significantly higher pairwise MHC and cytb FST, and significantly lower cytb diversity, but maintained similar levels of MHC diversity. The two most common MHC alleles (LiCA_B and Rapi_33) were associated with a significant decreased risk of Bd infection, and we detected positive selection acting on four peptide binding residues. Phylogenetic analysis suggested invasive populations likely arose from a single founding population in the American Midwest with a possible subsequent invasion in the northwest. Overall, our study suggests that the maintenance of diversity at adaptive loci may contribute to invasion success and highlights the importance of quantifying diversity at functional loci to assess the evolutionary potential of invasive populations.
维持适应位点的遗传多样性可以使种群适应新环境，从而促进非本地物种的入侵，尽管在创始事件中通常会在中性位点丧失多样性。为了评估这一预测，我们比较了北美洲入侵和本地范围内 20 个美洲牛蛙（Rana catesbeiana）种群在主要组织相容性复合体（MHC）和细胞色素 b（cytb）位点的遗传多样性，并量化了病原体蛙壶菌（Batrachochytrium dendrobatidis）（Bd）的存在情况。与本地种群相比，入侵种群的 Bd 患病率和强度显著更高，MHC 和 cytb 的成对 FST 显著更高，cytb 多样性显著更低，但 MHC 多样性保持相似水平。两种最常见的 MHC 等位基因（LiCA_B 和 Rapi_33）与 Bd 感染的风险显著降低有关，我们检测到四个肽结合残基上存在正选择。系统发育分析表明，入侵种群可能起源于美国中西部的单一创始种群，随后可能在西北部发生了入侵。总的来说，我们的研究表明，适应位点多样性的维持可能有助于入侵成功，并强调了量化功能位点多样性以评估入侵种群进化潜力的重要性。
