Data from: Anatomy of a neotropical insect radiation

Background: Much evolutionary theory predicts that diversity arises via both adaptive radiation (diversification driven by selection against niche-overlap within communities) and divergence of geographically isolated populations. We focus on tropical fruit flies (Blepharoneura, Tephritidae) that reveal unexpected patterns of niche-overlap within local communities. Throughout the Neotropics, multiple sympatric non-interbreeding populations often share the same highly specialized patterns of host use (e.g., flies are specialists on flowers of a single gender of a single species of host plants). Lineage through time (LTT) plots can help distinguish patterns of diversification consistent with ecologically limited adaptive radiation from those predicted by ecologically neutral theories. Here, we use a time-calibrated phylogeny of Blepharoneura to test the hypothesis that patterns of Blepharoneura diversification are consistent with an “ecologically neutral” model of diversification that predicts that diversification is primarily a function of time and space. Results: The Blepharoneura phylogeny showed more cladogenic divergence associated with geography than with shifts in host-use. Shifts in host-use were associated with ~20% of recent splits (<3 Ma), but >60% of older splits (>3 Ma). In the overall tree, gamma statistic and maximum likelihood model fitting showed no evidence of diversification rate changes though there was a weak signature of slowing diversification rate in one of the component clades. Conclusions: Overall patterns of Blepharoneura diversity are inconsistent with a traditional explanation of adaptive radiation involving decreases in diversification rates associated with niche-overlap. Sister lineages usually use the same host-species and host-parts, and multiple non-interbreeding sympatric populations regularly co-occur on the same hosts. We suggest that most lineage origins (phylogenetic splits) occur in allopatry, usually without shifts in host-use, and that subsequent dispersal results in assembly of communities composed of multiple sympatric non-interbreeding populations of flies that share the same hosts.研究背景：诸多进化理论均指出，生物多样性的产生同时源自适应辐射（adaptive radiation，即由群落内生态位重叠抗性选择驱动的物种分化）与地理隔离种群的分化。本研究聚焦于闪实蝇属（Blepharoneura，实蝇科Tephritidae）这类类群，其本地群落内呈现出出人意料的生态位重叠模式。在整个新热带区，多个同域非交配种群往往共享高度特化的寄主利用模式（例如，实蝇仅特化寄生于单一寄主植物物种的单性花器官）。类群通过时间（Lineage through time, LTT）图可用于区分符合生态受限适应辐射的物种分化模式，与生态中性理论所预测的分化模式。本研究利用闪实蝇属的时间校准系统发育树（time-calibrated phylogeny），检验如下假说：闪实蝇属的物种分化模式符合“生态中性”分化模型，该模型预测物种分化主要是时间与空间的函数。 研究结果：闪实蝇属的系统发育树显示，相较于寄主利用的转变，地理分布差异关联的分支分化更为显著。寄主利用转变与约20%的近期分化事件（距今<3百万年）相关，但与超过60%的古老分化事件（距今>3百万年）相关。对整体系统发育树的伽马统计量（gamma statistic）与最大似然模型拟合（maximum likelihood model fitting）结果显示，未发现多样化速率发生改变的证据，但其中一个亚支系呈现出微弱的多样化速率放缓信号。 研究结论：闪实蝇属的整体多样性模式，与传统的适应辐射解释并不相符——传统理论认为，生态位重叠会导致多样化速率下降。姊妹支系通常使用相同的寄主物种与寄主器官，且多个非交配的同域种群经常共同栖息于同一寄主之上。我们认为，多数支系起源（系统发育分化事件）均发生于异域分化（allopatry）过程中，通常未伴随寄主利用的转变；后续的扩散事件促成了群落构建，群落内包含多个共享同一寄主的同域非交配实蝇种群。