Exceptional endemicity of Aotearoa New Zealand biota shows how taxa dispersal traits, but not phylogeny, correlate with global species richness

Species’ with more limited dispersal and consequently less gene flow are more likely to form new spatially segregated species and thus contribute disproportionally to endemic biota and global species richness. Aotearoa New Zealand has exceptional endemicity, with 52% of its 54,000 named species endemic, including 32%, 39% and 68% for freshwater, marine and terrestrial environments respectively. The lower endemicity of freshwater biota (excluding insects) is attributed to their need to disperse between habitats that are temporary on evolutionary timescales. The percent endemicity of higher taxa (Order to Kingdom), a measure of phylogenetic relationships, was not correlated with regional and global species richness. However, there was a positive correlation between endemicity and species richness across dispersal trait groups based on their environment, typical body size, mobility (including flight), and if marine, whether pelagic or benthic. Typically flighted taxa had high endemicity contrary to the dispersal-endemicity hypothesis, but reflecting exceptional isolation by distance and time, and reduced flight ability as occurs on islands. It is proposed that the high richness and endemicity of mobile macrofauna is caused by a combination of niche specialisation opportunities and predation limiting dispersal respectively. Thus, dispersal traits better predicted endemicity and global species richness than phylogeny.

扩散能力有限、进而基因交流更少的物种类群，更易形成空间隔离的新物种，因此在特有生物区系与全球物种丰富度中贡献不成比例的份额。奥特亚罗瓦（Aotearoa）新西兰拥有极高的特有性水平：其已命名的54000个物种中，52%为特有物种，其中淡水、海洋与陆地环境的特有物种占比分别为32%、39%和68%。淡水生物（昆虫除外）的特有性较低，这归因于它们需要在演化时间尺度上属于临时性的生境之间进行扩散。高级分类单元（目至界）的特有性百分比——这是系统发育关系的一类衡量指标——与区域及全球物种丰富度并无相关性。然而，基于生存环境、典型体型、移动能力（包括飞行能力）以及海洋类群是否为远洋或底栖类群划分的扩散性状组中，特有性与物种丰富度之间存在正相关关系。通常具备飞行能力的类群拥有较高的特有性，这与扩散-特有性假说相悖，但却反映出极强的距离与时间隔离效应，同时也体现出岛屿环境下飞行能力的退化。研究提出，移动大型动物类群的高丰富度与高特有性，分别由生态位特化机遇与捕食作用限制扩散这两个因素共同导致。因此，相较于系统发育，扩散性状能更好地预测特有性与全球物种丰富度。