Zelditch Miriam Leah, Ye Ji, Mitchell Jonathan S, Swiderski Donald L
Museum of Paleontology, University of Michigan, Ann Arbor, Ann Arbor, 48109.
Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, 48109.
Evolution. 2017 Mar;71(3):633-649. doi: 10.1111/evo.13168. Epub 2017 Jan 28.
Convergence is widely regarded as compelling evidence for adaptation, often being portrayed as evidence that phenotypic outcomes are predictable from ecology, overriding contingencies of history. However, repeated outcomes may be very rare unless adaptive landscapes are simple, structured by strong ecological and functional constraints. One such constraint may be a limitation on body size because performance often scales with size, allowing species to adapt to challenging functions by modifying only size. When size is constrained, species might adapt by changing shape; convergent shapes may therefore be common when size is limiting and functions are challenging. We examine the roles of size and diet as determinants of jaw shape in Sciuridae. As expected, size and diet have significant interdependent effects on jaw shape and ecomorphological convergence is rare, typically involving demanding diets and limiting sizes. More surprising is morphological without ecological convergence, which is equally common between and within dietary classes. Those cases, like rare ecomorphological convergence, may be consequences of evolving on an adaptive landscape shaped by many-to-many relationships between ecology and function, many-to-one relationships between form and performance, and one-to-many relationships between functionally versatile morphologies and ecology. On complex adaptive landscapes, ecological selection can yield different outcomes.
趋同被广泛视为适应性的有力证据，常被描绘为从生态学角度可预测表型结果的证据，超越了历史偶然性。然而，除非适应度景观简单，由强大的生态和功能限制构建，否则重复的结果可能非常罕见。这样一种限制可能是对体型的限制，因为性能通常与体型相关，这使得物种仅通过改变体型就能适应具有挑战性的功能。当体型受到限制时，物种可能通过改变形状来适应；因此，当体型受限且功能具有挑战性时，趋同形状可能很常见。我们研究了体型和饮食作为松鼠科动物颌骨形状决定因素的作用。正如预期的那样，体型和饮食对颌骨形状有显著的相互依存效应，生态形态趋同很少见，通常涉及高要求的饮食和受限的体型。更令人惊讶的是没有生态趋同的形态趋同，这在不同饮食类别之间和同一饮食类别内部同样常见。这些情况，就像罕见的生态形态趋同一样，可能是在由生态与功能之间的多对多关系、形态与性能之间的多对一关系以及功能多样的形态与生态之间的一对多关系所塑造的适应度景观上进化的结果。在复杂的适应度景观上，生态选择可能会产生不同的结果。
