Species Distribution Modeling and Population Genetics of Nannophya pygmaea (Odonata: Libellulidae)

The Scarlet Pygmy Nannophya pygmaea Rambur, 1842 (Odonata: Libellulidae), the smallest described dragonfly species, is found across the Pacific coast and along the island chains of eastern Asia. Previous research has questioned whether N. pygmaea is potentially a complex of multiple species. Past studies have proposed a new species, N. koreana, based on mitochondrial genetic data, but the N. pygmaea complex remains unresolved. Using increased taxon sampling, we assessed genetic differentiation across populations and reconstructed evolutionary relationships of the N. pygmaea complex.From 141 COI-5P sequences, we calculated genetic structure through estimation of pairwise FST values among 10 populations and constructed a haplotype network to determine genetic differentiation, which revealed extremely high differentiation between northern populations (Japan, South Korea, China, Laos) and southern peninsula/island chain populations (Malaysia, Singapore, Indonesia, and Vietnam). Species distribution models showed large stretches of less suitable habitat between regions populated by N. pygmaea. A lack of gene flow and geographical isolation between the clades supports these highly differentiated populations being described as separate species.Additionally, our species distribution models (SDMs) explored the prevalence of present suitable habitats and how habitat suitability may shift between now and 2070. Our paleodistribution modeling provides insight into possible land migration routes that would allow N. pygmaea, as a weak flyer, to have dispersed to its present-day distribution. Ordination analysis of niche divergence between the northern and southern clades found no significant levels of niche differentiation or similarity between the two clades.猩红侏蜻（Nannophya pygmaea Rambur, 1842，蜻蜓目：蜻科）是目前已描述的体型最小的蜻蜓物种，分布于太平洋沿岸及东亚岛链区域。既往研究曾对该物种是否为多物种复合群提出质疑。过往研究基于线粒体遗传数据提出了新物种朝鲜侏蜻（N. koreana），但N. pygmaea复合群的分类问题仍未得到解决。本研究通过扩大类群采样量，评估了该复合群不同种群间的遗传分化，并重建了其系统发育关系。基于141条COI-5P序列，本研究通过估算10个种群间的成对FST值分析遗传结构，并构建单倍型网络以解析遗传分化，结果显示北部种群（日本、韩国、中国、老挝）与南部半岛/岛链种群（马来西亚、新加坡、印度尼西亚、越南）之间存在极高的遗传分化。物种分布模型（Species Distribution Models, SDMs）显示，N. pygmaea分布区域之间存在大片适宜性较低的生境。演化支间缺乏基因交流且存在地理隔离，这一结果支持将这些高度分化的种群描述为独立物种。此外，本研究的物种分布模型（SDMs）还分析了当前适宜生境的分布状况，并预测了2070年前后生境适宜性的变化趋势。本研究的古分布建模为这种飞行能力较弱的N. pygmaea如何扩散至当前分布范围提供了潜在的陆地迁移路径线索。对南北演化支的生态位分化进行排序分析后发现，二者之间既无显著的生态位分化，也无显著的生态位相似性。