Data from: DNA barcoding reveals a largely unknown fauna of Gracillariidae leaf-mining moths in the Neotropics

Higher taxa often show increasing species richness towards tropical low latitudes, a pattern known as the latitudinal biodiversity gradient (LBG). A rare reverse LBG (with greater richness towards temperate high latitudes) is exhibited by Gracillariidae leaf-mining moths, in which most described species occur in northern temperate areas. We carried out the first assessment of gracillariid species diversity in two Neotropical regions to test whether the relatively low tropical species diversity of this family is genuine or caused by insufficient sampling and a strong taxonomic impediment. Field surveys in six French Guianan and one Ecuadorian site produced 516 gracillariid specimens that were DNA barcoded to facilitate identification and to match larvae inside leaf mines with adults. Species delineation from sequence data was approximated using Automatic Barcode Gap Discovery and Refined Single Linkage Analysis through the Barcode Index Number system, and the proportion of described/undescribed species was estimated after comparison with types of 83% of described species. Locally, alpha-diversity far exceeds that of any known temperate fauna, with as many as 108 candidate species (59.3% as singletons) collected at one site, and with an estimated species richness lower bound of 240 species. Strikingly, at least 85% of the species collected as adults were found to be undescribed. Our sampling represents the most thorough survey of gracillariid species diversity in the Neotropics to date and the results from both our molecular and morphological analyses indicate that the current reverse LBG seen in this group is an artefact of insufficient sampling and a strong description deficit in the Neotropics.

高级分类单元通常在热带低纬度地区呈现出更高的物种丰富度，这一格局被称为纬度生物多样性梯度（latitudinal biodiversity gradient, LBG）。细蛾科（Gracillariidae）潜叶蛾类群则展现出罕见的反向纬度生物多样性梯度——即物种丰富度随温带高纬度地区纬度升高而增加，该科绝大多数已描述物种均分布于北温带区域。本研究针对两个新热带区开展细蛾科物种多样性的首次系统性评估，旨在验证该科在热带地区物种丰富度偏低的现象究竟是真实存在的，还是由采样不足以及严重的分类学障碍所导致。我们在法属圭亚那的6个采样点与厄瓜多尔的1个采样点开展野外调查，共采集到516号细蛾科标本，并对其进行DNA条形码测序，以辅助物种鉴定，同时将潜叶幼虫与成虫进行匹配。基于序列数据的物种界定，通过条形码索引编号（Barcode Index Number, BIN）系统下的自动条形码间隙发现法（Automatic Barcode Gap Discovery, ABGD）与改进单连接分析（Refined Single Linkage Analysis, RESL）进行近似推断；同时通过与83%已描述物种的模式标本进行比对，估算已描述与未描述物种的占比。从局域尺度来看，其α多样性远超所有已知温带动物区系，单个采样点采集到的候选物种多达108种（其中59.3%为单例样本），估算得到的物种丰富度下限为240种。尤为引人注目的是，采集到的成虫物种中至少有85%为未描述新物种。本次采样是迄今为止新热带区细蛾科物种多样性最为全面的系统性调查，分子与形态学分析结果均表明，该类群目前呈现的反向纬度生物多样性梯度，实则是新热带区采样不足以及物种描述严重缺失所造成的人为假象。