Data from: Ecological opportunity and ecomorphological convergence in Australasian robins (Petroicidae)

Ecological theories of adaptive radiation predict that ecological opportunity (EO) stimulates cladogenesis through entry into a novel environment and/or release of competition pressures. Due to its dynamic paleoclimatic and geological history, the Australo-Papuan region constitutes an opportune scenario to study patterns of diversification in relation to the colonization of new ecological niches. Here, we employ a comparative framework using the Australasian robins (Petroicidae) as a model system to test whether the diversification of this bird family fulfils a niche-filling process as predicted by the EO model, and to test whether the observed morphological similarity is described by a pattern of phylogenetic niche conservatism (PNC) or convergence. Although we detected an early-burst, we did not find a slowdown in speciation or morphological evolution as expected in a niche-filling scenario. Divergence in tarsus length and tail length (PC1) was consistent with a multi-peak model, in which PC1 represents a convergent trait among distantly related clades sharing the same foraging strategy. Our study thus shows that convergence rather than PNC seems to explain the existence of morphological similarity across independent lineages in the Petroicidae. We also found a low level of PNC regarding annual variations in temperature and precipitation, which is in agreement with the hypothesis that diversification within the Petroicidae involved repeated radiations. We suggest two non-mutually exclusive hypotheses to explain the overall lack of density-dependent cladogenesis. First, the extreme spatial and temporal heterogeneity of this region may have generated a pattern of repeated ecological opportunity over time and, second, this family may not yet have reached equilibrium diversity.

适应辐射的生态学理论预测，生态机会（ecological opportunity, EO）可通过进入全新环境或缓解竞争压力来推动分支演化。澳大拉西亚-巴布亚地区因其动态变化的古气候与地质历史，成为研究新生态位拓殖相关分化模式的理想场景。本研究以澳鵖科（Petroicidae）为模式系统，采用比较研究框架，旨在验证该鸟类类群的分化过程是否符合EO模型预测的生态位填充模式，并探究观测到的形态相似性究竟源于系统发育生态位保守性（phylogenetic niche conservatism, PNC）还是趋同演化。尽管研究检测到早期爆发信号，但并未发现生态位填充场景中预期的物种形成速率放缓或形态演化速率放缓现象。跗跖长度与尾长的分化（主成分1，PC1）符合多峰模型，该模型中PC1代表共享相同觅食策略的远缘支系间的趋同性状。因此本研究表明，相较于PNC，趋同演化更能解释澳鵖科不同独立支系间的形态相似性。我们还发现，针对温度与降水的年际变化，该类群的PNC水平较低，这与澳鵖科的分化涉及重复适应辐射的假说相符。最后，我们提出两个非互斥的假说来解释整体上缺乏密度制约分支演化的现象：其一，该地区极端的空间与时间异质性可能随时间推移反复产生生态机会；其二，该鸟类类群可能尚未达到均衡多样性水平。