Data from: Niche theory and its relation to morphology and phenotype in geographic space: a case study in woodpeckers (Picidae)

Ecogeographic analyses have recovered common environmental trends with respect to morphology; however discrepancies among trends exist. Hypothesized reasons for these divergences vary, but most relate a taxon’s morphology to its ecological niche. Morphology is known to diverge when species co-occur with competitors or predators and when species occur across different habitats and environments. A less understood divergence from ecogeographic trends is niche fixation, wherein species become locked into particular niches due to their community interactions or foraging ecology. A form of niche fixation has been hypothesized in the theory of Interspecies Social Dominance Mimicry (ISDM), in which mimics maintain relatively constant size ratios with models to perpetuate their mimicry. If true, mimics should display variation and trends in tandem with their models. Here, I use mass as a proxy for body size and examine ecogeographic trends in two sets of woodpeckers (Picidae): a Nearctic group which has been reported to interact via ISDM, and a Neotropical group which, based on similar appearances and overlapping distributions, is a potential ISDM system. I found ecogeographic trends suggestive of differential evolutionary responses, and I found evidence against niche fixation in the Nearctic clade. The Neotropic clade showed limited evidence for tandem size evolution between models and mimics, but inconsistencies in the size ratios between mimic and model populations. Here, I discuss the implications of observing divergent ecogeographic trends within mimicry systems, with specific emphasis on how environment, ecology, and community interactions guide evolution.生态地理分析已探明与形态特征相关的共性环境规律，但各类规律间仍存在分歧。针对这些分歧的假说原因各不相同，但多数将类群（taxon）的形态与其生态位（ecological niche）相关联。已知当物种与竞争者或捕食者共存，以及物种分布于不同生境与环境中时，其形态会发生分化。与生态地理规律背离、研究较少的一类现象是生态位固定（niche fixation），即物种因群落互作或觅食生态特征而被锁定于特定生态位中。物种间社会支配拟态（Interspecies Social Dominance Mimicry, ISDM）理论中便提出了一种生态位固定的形式：拟态者与模型物种维持相对恒定的体型比例，以维持其拟态效果。若该理论成立，拟态者的体型变异与变化趋势应与模型物种保持一致。本研究以体重作为体型的替代指标，对两类啄木鸟（Picidae）的生态地理规律展开分析：一类是新北界类群，已有研究表明其通过ISDM发生互作；另一类是新热带界类群，基于其外观相似且分布重叠的特征，属于潜在的ISDM研究系统。本研究发现，生态地理规律暗示类群间存在差异化的演化响应，同时在新北界演化支（clade）中找到了反对生态位固定的证据。新热带界演化支中，拟态者与模型物种间的协同体型演化证据有限，且拟态者与模型种群间的体型比例存在不一致性。本研究最后探讨了在拟态系统中观测到生态地理规律分化的研究意义，重点阐释了环境、生态学特征以及群落互作如何引导演化进程。