Phylogeographic analysis reveals high genetic structure with uniform phenotypes in the paper wasp Protonectarina sylveirae (Hymenoptera: Vespidae)

Swarm-founding wasps are endemic and common representatives of neotropical fauna and compose an interesting social tribe of vespids, presenting both complex social characteristics and uncommon traits for a eusocial group, such as the absence of castes with distinct morphology. The paper wasp Protonectarina sylveirae (Saussure) presents a broad distribution from Brazil, Argentina and Paraguay, occurring widespread in the Atlantic rainforest and arboreal Caatinga, being absent in the Amazon region. Given the peculiar distribution among swarm-founding wasps, an integrative approach to reconstruct the evolutionary history of P. sylveirae in a spatial-temporal framework was performed to investigate: the presence of genetic structure and its relationship with the geography, the evolution of distinct morphologic lineages and the possible historical event(s) in Neotropical region, which could explain the observed phylogeographic pattern. Individuals of P. sylveirae were obtained from populations of 16 areas throughout its distribution for DNA extraction and amplification of mitochondrial genes 12S, 16S and COI. Analysis of genetic diversity, construction of haplotype net, analysis of population structure and dating analysis of divergence time were performed. A morphometric analysis was also performed using 8 measures of the body of the adult (workers) to test if there are morphological distinction among populations. Thirty-five haplotypes were identified, most of them exclusively of a group and a high population structure was found. The possibility of genetic divergence because of isolation by distance was rejected. Morphological analysis pointed to a great uniformity in phenotypes, with only a small degree of differentiation between populations of south and the remaining. Divergence time analysis showed a Middle/Late Miocene origin, a period where an extensive marine ingression occurred in South America. Divergence of haplogroups began from the Plio/Pleistocene boundary and the last glacial maximum most likely modeled the current distribution of species, even though it was not the cause of genetic breaks.群栖筑巢胡蜂（swarm-founding wasps）是新热带区动物区系的特有且常见类群，隶属于胡蜂科（Vespidae）中一个颇具研究价值的社会性部落，兼具复杂的社会性特征与真社会性类群罕见的性状——例如不存在具有形态分化的品级。造纸胡蜂*Protonectarina sylveirae（Saussure）*的分布范围涵盖巴西、阿根廷与巴拉圭，在大西洋雨林及林木型卡廷加植被区广泛分布，但未在亚马孙地区被记录。鉴于该物种在群栖筑巢胡蜂中具有独特的分布格局，本研究采用整合研究方法，在时空框架下重建*P. sylveirae*的演化历史，旨在探究遗传结构的存在及其与地理格局的关联、不同形态谱系的演化过程，以及新热带区的历史事件能否解释观测到的系统地理格局。研究人员在该物种的整个分布范围内的16个种群中采集了*P. sylveirae*个体，用于DNA提取及线粒体基因12S rRNA、16S rRNA和细胞色素C氧化酶亚基I（COI）的扩增。后续开展了遗传多样性分析、单倍型网络（haplotype net）构建、种群结构（population structure）分析及分化时间测年分析（dating analysis of divergence time）。此外，还针对成虫职虫（workers）的8项身体量度指标开展形态测量分析（morphometric analysis），以检验不同种群间是否存在形态分化。本研究共鉴定出35个单倍型（haplotype），其中多数为类群特有单倍型，且检测到高度显著的种群结构。距离隔离（isolation by distance）导致遗传分化的假说被排除。形态分析结果显示该物种表型整体高度统一，仅南部种群与其余种群间存在微弱的形态分化。分化时间测年结果表明，该类群起源于中新世中晚期（Middle/Late Miocene）——这一时期南美大陆曾发生广泛海侵（marine ingression）；单倍型群的分化始于上新世-更新世边界（Plio/Pleistocene boundary）；末次盛冰期（last glacial maximum）虽未造成遗传隔离，但极可能塑造了该物种当前的分布格局。