Department of Evolutionary Ecology, Estación Biológica de Doñana (EBD-CSIC), Sevilla, Spain.
Department of Conservation Biology, Estación Biológica de Doñana (EBD-CSIC), Sevilla, Spain.
Mol Ecol. 2019 Jan;28(2):379-390. doi: 10.1111/mec.14968. Epub 2019 Jan 17.
The high relevance of host-switching for the diversification of highly host-specific symbionts (i.e., those commonly inhabiting a single host species) demands a better understanding of host-switching dynamics at an ecological scale. Here, we used DNA metabarcoding to study feather mites on passerine birds in Spain, sequencing mtDNA (COI) for 25,540 individual mites (representing 64 species) from 1,130 birds (representing 71 species). Surprisingly, 1,228 (4.8%) mites from 84 (7.4%) birds were found on host species that were not the expected to be a host according to a recent bird-feather mite associations catalog. Unexpected associations were widespread across studied mite (40.6%) and bird (43.7%) species and showed smaller average infrapopulation sizes than typical associations. Unexpected mite species colonized hosts being distantly related to the set of their usual hosts, but with similar body size. The network of bird-mite associations was modular (i.e., some groups of bird and mite species tended to be more associated with each other than with the others), with 75.9% of the unexpected associations appearing within the module of the typical hosts of the mite species. Lastly, 68.4% of mite species found on unexpected hosts showed signatures of genetic differentiation, and we found evidence for reproduction or the potential for it in many of the unexpected associations. Results show host colonization as a common phenomenon even for these putatively highly host-specific symbionts. Thus, host-switching by feather mites, rather than a rare phenomenon, appears as a relatively frequent phenomenon shaped by ecological filters such as host morphology and is revealed as a fundamental component for a dynamic coevolutionary and codiversification scenario.
宿主转换对于高度宿主特异性共生体（即通常栖息在单一宿主物种中的共生体）的多样化具有高度相关性，这就需要更好地了解生态尺度上的宿主转换动态。在这里，我们使用 DNA 宏条形码技术研究了西班牙雀形目鸟类的羽毛螨，对 25540 只个体螨（代表 64 个物种）的 mtDNA（COI）进行了测序，这些螨来自 1130 只鸟（代表 71 个物种）。令人惊讶的是，在 84 只鸟（占 7.4%）中发现了 1228 只（占 4.8%）螨，这些鸟并不是根据最近的鸟类-羽毛螨关联目录预期的宿主。在研究的螨（40.6%）和鸟（43.7%）物种中，意外的关联广泛存在，且其亚种群平均规模小于典型关联。意外的螨物种会在与它们通常宿主关系较远的宿主上定殖，但这些宿主的体型相似。鸟类-螨类关联网络是模块化的（即，一些鸟类和螨类物种的群组往往彼此之间的关联比与其他群组之间的关联更密切），其中 75.9%的意外关联出现在螨类物种的典型宿主模块内。最后，在意外宿主上发现的 68.4%的螨物种表现出遗传分化的特征，并且我们在许多意外关联中发现了繁殖或潜在繁殖的证据。结果表明，宿主定殖是一种常见现象，即使对于这些假定的高度宿主特异性共生体也是如此。因此，羽毛螨的宿主转换似乎是一种相对频繁的现象，而不是一种罕见的现象，它是由宿主形态等生态过滤器塑造的，并被揭示为动态协同进化和共适应情景的基本组成部分。
