Long-Term Habitat Fragmentation Is Associated With Reduced MHC IIB Diversity and Increased Infections in Amphibian Hosts
Long-Term Habitat Fragmentation Is Associated With Reduced MHC IIB Diversity and Increased Infections in Amphibian Hosts
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DOI：
10.3389/fevo.2018.00236
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发表时间：
2019-01-10
影响因子：
3
通讯作者：
James, Timothy Y.
中科院分区：
文献类型：
--
作者：
Belasen, Anat M.;Bletz, Molly C.;James, Timothy Y.
栖息地破碎化和野生动物疾病是生物多样性丧失的两个普遍驱动因素，但很少有实证研究探讨它们之间的相互作用。在这项研究中，我们利用一个自然破碎的岛屿系统来研究碎片化对遗传多样性和两栖动物感染动态的影响。我们确定了碎片化对免疫位点MHC IIB遗传多样性的影响，MHC IIB是疾病易感性的假设预测因子。与预期的MHC多样性将由于平衡选择而保持高水平相反，岛屿种群在MHC IIB正选择的同时失去了该位点的遗传多样性。然后，我们使用下一代测序从两栖动物皮肤拭子中鉴定出多种潜在的真核寄生虫。与大陆种群相比，岛屿种群表现出更高的潜在寄生虫丰富度（寄生类群中真核微生物操作分类单位或OTUs的比例）。MHC纯合子宿主潜在寄生虫的多样性较低，种群水平MHC多样性与寄生虫丰富度呈负相关。我们的研究结果表明，基因侵蚀可能发生在MHC IIB位点破碎后，这可能有助于增加对寄生虫的易感性。
Habitat fragmentation and wildlife disease are two widespread drivers of biodiversity loss, yet few empirical studies have explored their interactions. In this study, we utilized a naturally fragmented island system to examine the impacts of fragmentation on genetic diversity and amphibian infection dynamics. We determined the impacts of fragmentation on genetic diversity at the immunity locus MHC IIB, a hypothesized predictor of disease susceptibility. Contrary to the expectation that MHC diversity would remain high due to balancing selection, island populations lost genetic diversity at this locus while simultaneously experiencing positive selection at MHC IIB. We then used Next-Generation Sequencing to identify a variety of potential eukaryotic parasites from amphibian skin swabs. Island populations exhibited higher potential parasite richness (proportion of eukaryotic microbe operational taxonomic units or OTUs from parasitic taxa) relative to mainland populations. MHC homozygotes hosted a lower diversity of potential parasites, and population-level MHC diversity was negatively associated with parasite richness. Our results show that genetic erosion can occur at the MHC IIB locus following fragmentation, which may contribute to increased susceptibility to parasites.