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：2014
卷号：111
期号：46
页码：16419-16424
DOI：10.1073/pnas.1406304111
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceShifts in biological diversity often are associated with particular anatomical traits. Anatomical data from over 300 clades of brachiopods, molluscs, arthropods, echinoderms, and chordates show that trait-based diversification shifts are common at even fairly low (genus and species) taxonomic levels. Cambrian taxa present the lone major exception. Among post-Cambrian taxa, diversification shifts correlate strongly with elevated net extinction of primitive taxa rather than elevated net speciation of derived taxa or increased morphological disparity among derived taxa. This finding emphasizes the importance of extinction in shaping morphological and phylogenetic diversity among closely related species and genera as well as suggests another way in which Cambrian evolution was unique. Evolution provides many cases of apparent shifts in diversification associated with particular anatomical traits. Three general models connect these patterns to anatomical evolution: (i) elevated net extinction of taxa bearing particular traits, (ii) elevated net speciation of taxa bearing particular traits, and (iii) elevated evolvability expanding the range of anatomies available to some species. Trait-based diversification shifts predict elevated hierarchical stratigraphic compatibility (i.e., primitive[->]derived[->]highly derived sequences) among pairs of anatomical characters. The three specific models further predict (i) early loss of diversity for taxa retaining primitive conditions (elevated net extinction), (ii) increased diversification among later members of a clade (elevated net speciation), and (iii) increased disparity among later members in a clade (elevated evolvability). Analyses of 319 anatomical and stratigraphic datasets for fossil species and genera show that hierarchical stratigraphic compatibility exceeds the expectations of trait-independent diversification in the vast majority of cases, which was expected if trait-dependent diversification shifts are common. Excess hierarchical stratigraphic compatibility correlates with early loss of diversity for groups retaining primitive conditions rather than delayed bursts of diversity or disparity across entire clades. Cambrian clades (predominantly trilobites) alone fit null expectations well. However, it is not clear whether evolution was unusual among Cambrian taxa or only early trilobites. At least among post-Cambrian taxa, these results implicate models, such as competition and extinction selectivity/resistance, as major drivers of trait-based diversification shifts at the species and genus levels while contradicting the predictions of elevated net speciation and elevated evolvability models.
