Data from: Environmental and scale-dependent evolutionary trends in the body size of crustaceans

The ecological and physiological significance of body size is well recognized. However, key macroevolutionary questions regarding the dependency of body size trends on the taxonomic scale of analysis and the role of environment in controlling long-term evolution of body size are largely unknown. Here, we evaluate these issues for decapod crustaceans, a group that diversified in the Mesozoic. A compilation of body size data for 792 brachyuran crab and lobster species reveals that their maximum, mean and median body size increased, but no increase in minimum size was observed. This increase is not expressed within lineages, but is rather a product of the appearance and/or diversification of new clades of larger, primarily burrowing to shelter-seeking decapods. This argues against directional selective pressures within lineages. Rather, the trend is a macroevolutionary consequence of species sorting: preferential origination of new decapod clades with intrinsically larger body sizes. Furthermore, body size evolution appears to have been habitat-controlled. In the Cretaceous, reef-associated crabs became markedly smaller than those in other habitats, a pattern that persists today. The long-term increase in body size of crabs and lobsters, coupled with their increased diversity and abundance, suggests that their ecological impact may have increased over evolutionary time.

体型的生态与生理意义早已得到学界广泛认可。然而，有关体型演化趋势对分析分类学尺度的依赖性，以及环境在调控体型长期演化过程中所扮演的角色这两大核心宏观演化问题，目前仍尚未被充分探明。本研究针对在中生代发生辐射演化的十足目甲壳类（decapod crustaceans）展开了相关问题的探讨。我们整合了792种短尾下目螃蟹（brachyuran crab）与龙虾的体型数据，分析结果显示：这类生物的最大、平均与中位体型均呈现上升趋势，但未观测到最小体型出现显著增长。该体型增长趋势并非在支系内部体现，而是源于体型更大的全新演化支（clade）的出现与/或辐射演化——这类新生演化支多为穴居、偏好栖息庇护场所的十足目类群。这一结果驳斥了支系内部存在定向选择压力的观点。相反，该趋势实为物种分选（species sorting）的宏观演化产物：即内在体型更大的十足目演化支具有更高的起源概率。此外，体型演化似乎受到生境的调控。在白垩纪（Cretaceous），礁栖螃蟹的体型显著小于其他生境中的类群，这一格局至今仍未改变。螃蟹与龙虾的体型长期增长，加之其多样性与丰度的提升，表明它们的生态影响可能随演化时间推移不断增强。