Data from: Evolution of a key trait greatly affects underground community assembly process through habitat adaptation in earthworms

Underground community assemblies have not been studied well compared with aboveground communities, despite their importance for our understanding of whole ecosystems. To investigate underground community assembly over evolutionary time scales, we examined terrestrial earthworm communities (Oligochaeta: Haplotaxida) in conserved mountainous primary forests in Japan as a model system. We collected 553 earthworms mostly from two dominant families, the Megascolecidae and the Lumbricidae, from 12 sites. We constructed a molecular taxonomic unit tree based on the analysis of three genes to examine the effects of a biogeographic factor (dispersal ability) and an evolutionary factor (habitat adaptation) on the earthworm community assembly process. The phylogenetic distance of the earthworm communities among sites was positively correlated with geographic distance when intraspecific variation was included, indicating that the divergence within species was affected by biogeographic factors. The community assembly process in the Megascolecidae has also been affected by environmental conditions in relation to an evolutionary relationship between habitat environment and intestinal caecum type, a trait closely related to habitat depth and diet, whereas that in the Lumbricidae has not been affected as such. Intestinal caecum type showed a pattern of niche conservatism in the Megascolecidae lineage. Our results suggest that investigating the evolution of a key trait related to life history can lead to the clear description of community assembly process over a long time scale and that the community assembly process can differ greatly among related lineages even though they live sympatrically.

尽管地下群落构建（community assembly）相较于地上群落构建的研究程度仍显不足，但其对于我们完整理解生态系统具有重要意义。为探究进化时间尺度下的地下群落构建过程，我们以日本保护完好的山地原始森林中的陆生蚯蚓群落（寡毛纲：单向蚓目）作为研究模式系统。我们于12个样点中共采集到553号蚯蚓标本，其中绝大多数隶属于两个优势科：巨蚓科（Megascolecidae）和正蚓科（Lumbricidae）。我们基于3个基因的分析构建了分子分类单元树，以探究生物地理因子（扩散能力）和进化因子（生境适应）对蚯蚓群落构建过程的影响。当纳入种内变异时，各样点间蚯蚓群落的系统发育距离与地理距离呈正相关，表明物种内部的分化受到生物地理因子的调控。巨蚓科的群落构建过程还受到与生境环境和肠盲囊类型演化关联相关的环境条件调控——肠盲囊类型是与栖息深度和食性密切相关的性状——而正蚓科的群落构建过程则未受到此类因素的影响。在巨蚓科的演化支中，肠盲囊类型呈现出生态位保守性（niche conservatism）的演化模式。本研究结果表明，探究与生活史相关的关键性状的演化，能够清晰阐明长时间尺度下的群落构建过程；且即便近缘类群同域分布，其群落构建过程也可能存在显著差异。