Data from: Exploring the impact of habitat size on phylogeographic patterning in the Overberg velvet worm Peripatopsis overbergiensis (Onychophora: Peripatopsidae)

Evolutionary relationships in the velvet worm species, Peripatopsis overbergiensis, were examined in 3 forest areas in the Overberg region of South Africa to explore the impact of historical habitat fragmentation on the population genetic structure of the species. We collected 84 P. overbergiensis specimens from Grootvadersbosch, Koppie Alleen, and Marloth Nature Reserves and sequenced all these specimens for the cytochrome c oxidase subunit I (COI) locus, whereas a subset of 13 specimens were also sequenced for the 18S rRNA locus. Phylogenetic analyses of the 20 unique COI haplotypes revealed 4 genetically distinct clades, a result that is corroborated by the haplotype network. A hierarchical analysis of genetic variation was performed on the COI haplotype data within the 2 large forested areas, Grootvadersbosch and Marloth Nature Reserves, and across all 3 of the sample localities. These results revealed low haplotypic and nucleotide diversity within the largest Grootvadersbosch Nature Reserve forest and high haplotypic and nucleotide diversity within the fragmented Marloth Nature Reserve forest, whereas Koppie Alleen had the lowest haplotypic and nucleotide diversity. Across all 3 main localities statistically significant F ST values were found, together with the absence of shared haplotypes indicating the absence of maternal gene flow. Divergence time estimations based on the 20 COI haplotypes calculated in BEAST suggest a Pleistocene/Holocene divergence between the 4 clades as a result of habitat fragmentation and the aridification of the region. Our results indicate that conservation efforts should also prioritize linked, smaller fragmented habitats together with continuous habitats to maximize the genetic diversity of saproxylic fauna.

本研究针对南非奥弗贝格（Overberg）地区的3处林区，对奥弗贝格天鹅绒虫（*Peripatopsis overbergiensis*）的演化关系展开分析，旨在探究历史生境破碎化对该物种种群遗传结构的影响。我们从格罗特瓦德博斯自然保护区（Grootvadersbosch）、科普阿尔伦自然保护区（Koppie Alleen）以及马洛斯自然保护区（Marloth Nature Reserves）采集了84号奥弗贝格天鹅绒虫标本，对所有标本的细胞色素c氧化酶亚基I（cytochrome c oxidase subunit I, COI）基因座进行测序；同时选取其中13号标本，额外对18S rRNA基因座开展测序。对20个独特COI单倍型的系统发育分析显示存在4个遗传分化显著的进化支，单倍型网络分析结果也验证了这一结论。基于COI单倍型数据，我们分别在格罗特瓦德博斯与马洛斯这两处大型林区内部，以及全部3个采样点之间开展了分层遗传变异分析。分析结果显示，面积最大的格罗特瓦德博斯自然保护区林区内单倍型多样性与核苷酸多样性均处于较低水平；生境破碎化的马洛斯自然保护区林区内则呈现较高的单倍型与核苷酸多样性；而科普阿尔伦自然保护区的两项多样性指标均为最低。在全部3个主要采样点之间，均检测到具有统计学显著性的F_ST值，且未发现共享单倍型，这表明该物种不存在母系基因流。基于20个COI单倍型、通过BEAST软件估算的分化时间显示，4个进化支的分化发生在更新世/全新世时期，这一事件由该区域的生境破碎化与干旱化所导致。本研究结果表明，保护工作应同时优先保护连片的连续生境与相互连通的小型破碎生境，以最大化腐木依赖型动物群落的遗传多样性。