Developmental Constraints Do Not Influence Long-Term Phenotypic Evolution of Marsupial Forelimbs as Revealed by Interspecific Disparity and Integration Patterns
Developmental Constraints Do Not Influence Long-Term Phenotypic Evolution of Marsupial Forelimbs as Revealed by Interspecific Disparity and Integration Patterns
复制标题
种间差异和整合模式表明，发育限制不影响有袋动物前肢的长期表型进化
作者：
A. Martín‐Serra;R. Benson
有袋动物的前肢生态形态范围比胎盘哺乳动物小，这可能是有袋动物特殊的生殖生物学所施加的宏观进化限制的结果。具体来说，有袋动物前肢的加速发育使新生儿能够爬向母亲的育儿袋，但可能会限制成年动物的形态。这一假说提出了三个主要的预测：(1)有袋动物的前肢应该比后肢表现出更少的种间差异；(2)有袋动物前肢内部的形态整合比四肢之间的整合更强；(3)这些模式应该在双原齿动物身上表现得最强烈，它们在出生时经历了最严格的爬行。我们使用51种有袋动物的肢体骨骼的三维几何形态测量数据集来测试这些预测。我们发现：(i)有袋动物的前肢和后肢表现出类似的差异，（ii）在四肢内部或四肢之间的整合没有明显的差异，（iii）双原齿动物与其他有袋动物的模式相同，甚至校正了谱系年龄。因此，目前几乎没有证据表明有袋动物的发育生物学限制了它们的宏观进化模式。功能选择有可能克服发育限制对宏观进化时间尺度的影响。我们的研究结果表明，应该重新考虑发育限制在解释有袋动物（与胎盘动物相比）有限的表型变异性中的作用。
Marsupials show a smaller range of forelimb ecomorphologies than placental mammals, and it is hypothesized that this results from macroevolutionary constraints imposed by the specialized reproductive biology of marsupials. Specifically, the accelerated development of the marsupial forelimb allows neonates to crawl to the mother’s pouch but may constrain adult morphology. This hypothesis makes three main predictions: (i) that marsupial forelimbs should show less interspecific disparity than their hindlimbs, (ii) that morphological integration within the marsupial forelimb is stronger than integration between limbs, and (iii) that these patterns should be strongest in diprotodontians, which undergo the most rigorous crawls as neonates. We use a three-dimensional geometric morphometric data set of limb bones for 51 marsupial species to test these predictions. We find that (i) marsupial forelimbs and hindlimbs show similar disparities, (ii) no clear differences in integration exist either within or between limbs, and (iii) the same patterns occur in diprotodontians as in other marsupials, even correcting for lineage age. Therefore, there is currently little evidence that the developmental biology of marsupials has constrained their macroevolutionary patterns. It is possible that functional selection can overcome the effects of developmental constraint on macroevolutionary timescales. Our findings suggest that the role of developmental constraints in explaining the limited phenotypic variability of marsupials (compared with that of placentals) should be reconsidered.