Department of Biology, University of Vermont, Burlington, VT 05405-0086, USA.
School of Life Sciences, Shangrao Normal University, Shangrao 334001, China.
Syst Biol. 2020 Nov 1;69(6):1122-1136. doi: 10.1093/sysbio/syaa017.
Vicariance and dispersal events, combined with intricate global climatic history, have left an imprint on the spatiotemporal distribution and diversity of many organisms. Anelosimus cobweb spiders (Theridiidae), are organisms ranging in behavior from solitary to highly social, with a cosmopolitan distribution in temperate to tropical areas. Their evolutionary history and the discontinuous distribution of species richness suggest that 1) long-distance overwater dispersal and 2) climate change during the Neogene (23-2.6 Ma), may be major factors in explaining their distribution and diversification. Here, we test these hypotheses, and explicitly test if global Miocene/Pliocene climatic cooling in the last 8 Ma affected Anelosimus radiation in parallel in South America and Madagascar. To do so, we investigate the phylogeny and spatiotemporal biogeography of Anelosimus through a culmination of a 20-year comprehensive global sampling at the species level (69 species, including 84% of the known 75 species worldwide, represented by 268 individuals) using nucleotide data from seven loci (5.5 kb). Our results strongly support the monophyly of Anelosimus with an Oligocene ($\sim $30 Ma) South American origin. Major clades on other continents originate via multiple, long-distance dispersal events, of solitary or subsocial-but not social-lineages, from the Americas. These intercontinental dispersals were to Africa, Madagascar (twice), and SE Asia/Australasia. The early diversification of Anelosimus spiders coincides with a sudden thermal increase in the late Oligocene ($\sim $27-25 Ma), though no causal connection can be made. Our results, however, strongly support the hypothesis that global Neogene climatic cooling in the last 8 Ma drove Anelosimus radiation in parallel in South America and Madagascar, offering a rare empirical evidence for diversification of a socially diverse group driven by an interplay between long-distance dispersal and global Neogene climatic changes. [Cobweb spiders; diversification; global biogeography; long-distance dispersal; molecular phylogenetics; neogene climate changes; sociality; vicariance.].
隔离和扩散事件，加上复杂的全球气候历史，在许多生物的时空分布和多样性上留下了印记。Anelosimus 蛛网蜘蛛（Theridiidae）是一种行为从独居到高度社会性的生物，分布范围广泛，涵盖了温带到热带地区。它们的进化历史和物种丰富度的不连续分布表明：1）长距离跨海扩散，以及 2）新近纪（23-2.6 百万年前）期间的气候变化，可能是解释它们分布和多样化的主要因素。在这里，我们检验了这些假设，并明确检验了过去 800 万年中全球中新世/上新世气候变冷是否对南美洲和马达加斯加的 Anelosimus 辐射产生了平行影响。为此，我们通过在物种水平上进行了长达 20 年的全球综合采样（包括全世界已知的 75 种中的 84%，代表了 268 个个体），利用来自七个基因座（5.5kb）的核苷酸数据，研究了 Anelosimus 的系统发育和时空生物地理学。我们的结果强烈支持 Anelosimus 的单系性，起源于渐新世（约 3000 万年前）的南美洲。其他大陆的主要分支起源于来自美洲的多个长距离扩散事件，涉及独居或亚社会性但非社会性的谱系。这些洲际扩散事件发生在非洲、马达加斯加（两次）和东南亚/澳大拉西亚。Anelosimus 蜘蛛的早期多样化与晚渐新世（约 27-25 百万年前）的突然升温相吻合，尽管不能建立因果关系。然而，我们的结果强烈支持这样一种假说，即在过去 800 万年中全球新近纪气候变冷推动了南美洲和马达加斯加的 Anelosimus 辐射，为一个由长距离扩散和全球新近纪气候变化相互作用驱动的社会性多样化群体的多样化提供了罕见的经验证据。
