期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：12
页码：3758-3763
DOI：10.1073/pnas.1418153112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceBiodiversification studies have often relied on constant-rate models of diversification. More recently, however, there has been an effort to identify changes in diversification rates within clades. This effort has largely focused on models of declining rates because many clades appear to have high initial rates, followed by slow-downs as ecological space fills. Here we provide an example of a 265 million-year-old marine invertebrate clade where evolutionary rates show a net increase over time instead. This is punctuated by intervals of high rates of morphological evolution, coinciding with major shifts in lifestyle and the evolution of new subclades. This study demonstrates the dynamic nature of evolutionary change within major clades. How ecological and morphological diversity accrues over geological time has been much debated by paleobiologists. Evidence from the fossil record suggests that many clades reach maximal diversity early in their evolutionary history, followed by a decline in evolutionary rates as ecological space fills or due to internal constraints. Here, we apply recently developed methods for estimating rates of morphological evolution during the post-Paleozoic history of a major invertebrate clade, the Echinoidea. Contrary to expectation, rates of evolution were lowest during the initial phase of diversification following the Permo-Triassic mass extinction and increased over time. Furthermore, although several subclades show high initial rates and net decreases in rates of evolution, consistent with "early bursts" of morphological diversification, at more inclusive taxonomic levels, these bursts appear as episodic peaks. Peak rates coincided with major shifts in ecological morphology, primarily associated with innovations in feeding strategies. Despite having similar numbers of species in today's oceans, regular echinoids have accrued far less morphological diversity than irregular echinoids due to lower intrinsic rates of morphological evolution and less morphological innovation, the latter indicative of constrained or bounded evolution. These results indicate that rates of evolution are extremely heterogenous through time and their interpretation depends on the temporal and taxonomic scale of analysis.
关键词：fossil record ; morphological diversification ; early bursts ; evolutionary innovation ; mode of evolution
