Comparative tests of the species-genetic diversity correlation at neutral and non-neutral loci in four species of stream insect

A fundamental question linking population genetics and community ecology is how adaptive processes (e.g., natural selection) and neutral processes (e.g., drift-migration equilibrium) underpin the species-genetic diversity correlation (SGDC). Here we combine genome scans and outlier loci detection with community analysis to separately test for neutral and non-neutral SGDCs in four species of stream insect. We sampled 60 localities in Japan and examined the relationships among population AFLP band richness (Br), taxon richness of the total community (S) and of the trophic guild (Str) richness, and 15 habitat parameters that could potentially drive adaptation and influence richness. Neutral Br was positively correlated with S only in the dominant species of these communities, suggesting Br may be constrained when intra-specific competition is pronounced. Non-neutral Br was correlated with Str in a species restricted to high elevations where habitat heterogeneity was highest. Community distance and genetic distance (β-SGDC) was correlated in two of the four species at both neutral and non-neutral loci. Distance-based redundancy analysis found geographic isolation and elevation to drive divergence of both communities and populations. This suggests that both neutral and adaptive divergence occurred through the shared influences of geographic isolation and local adaptation at the two levels of diversity.

将种群遗传学（population genetics）与群落生态学（community ecology）相联结的核心议题之一，是适应性过程（如自然选择）与中性过程（如漂变-迁移平衡）如何支撑物种-遗传多样性相关性（species-genetic diversity correlation, SGDC）。本研究将基因组扫描（genome scans）与异常位点检测（outlier loci detection）技术结合群落分析方法，针对4种溪流昆虫的中性与非中性SGDC分别开展检验。我们在日本境内布设60个采样点，分析了种群扩增片段长度多态性（AFLP）条带丰富度（Br）、总群落类群丰富度（S）、营养功能群类群丰富度（Str），以及15项可能驱动适应性演化并影响丰富度的生境参数之间的关联。仅在上述群落的优势物种中，中性Br与S呈正相关，提示当种内竞争显著时，Br可能受到约束。仅在生境异质性最高的高海拔特有物种中，非中性Br与Str呈现显著相关。在4个物种中的2个物种内，中性与非中性位点的群落距离与遗传距离（β-SGDC）均呈显著相关。基于距离的冗余分析（distance-based redundancy analysis）表明，地理隔离与海拔是驱动群落与种群分化的核心因素。这意味着，中性与适应性分化均通过地理隔离与局部适应的共同作用，在两个多样性层面得以实现。