Ikeda Hiroshi, Fukumori Kayoko, Shoda-Kagaya Etsuko, Takahashi Masamichi, Ito Masamichi T, Sakai Yoshimi, Matsumoto Kazuma
Faculty of Agriculture and Life Science Hirosaki University Hirosaki Japan.
National Institute of Advanced Industrial Science and Technology Tsukuba Japan.
Ecol Evol. 2018 Jan 8;8(3):1726-1735. doi: 10.1002/ece3.3777. eCollection 2018 Feb.
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 timescales, 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 cecum type, a trait closely related to habitat depth and diet, whereas that in the Lumbricidae has not been affected as such. Intestinal cecum 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 timescale and that the community assembly process can differ greatly among related lineages even though they live sympatrically.
与地上群落相比，地下群落集合尚未得到充分研究，尽管它们对于我们理解整个生态系统很重要。为了研究进化时间尺度上的地下群落集合，我们以日本受保护的山区原始森林中的陆生蚯蚓群落（寡毛纲：单孔目）为模型系统进行了研究。我们从12个地点收集了553条蚯蚓，它们大多来自两个优势科，即巨蚓科和正蚓科。我们基于对三个基因的分析构建了一个分子分类单元树，以研究生物地理因素（扩散能力）和进化因素（栖息地适应）对蚯蚓群落集合过程的影响。当纳入种内变异时，各地点蚯蚓群落的系统发育距离与地理距离呈正相关，这表明物种内的分化受生物地理因素影响。巨蚓科的群落集合过程也受到与栖息地环境和肠盲囊类型之间进化关系相关的环境条件的影响，肠盲囊类型是与栖息地深度和饮食密切相关的一个性状，而正蚓科的群落集合过程则未受此类影响。肠盲囊类型在巨蚓科谱系中呈现出生态位保守的模式。我们的结果表明，研究与生活史相关的关键性状的进化可以在长时间尺度上清晰描述群落集合过程，并且即使相关谱系同域分布，它们的群落集合过程也可能有很大差异。
