@ARTICLE{TreeBASE2Ref18727, author = {Stacey DeWitt Smith and Richard E. Miller and Sarah P. Otto and Richard G. FitzJohn and Mark D. Rausher}, title = {The effects of flower color transitions on diversification rates in the morning glories (Ipomoea subg. Quamoclit, Convolvulaceae). In M. Long (ed.) Darwin-China 2009.}, year = {2010}, keywords = {}, doi = {}, url = {}, pmid = {}, journal = {Peking University Press}, volume = {}, number = {}, pages = {}, abstract = {As in many clades of flowering plants, the Quamoclit clade of morning glories (Ipomoea subgenus Quamoclit) exhibits skewed proportions of different flower colors, with pigmented species outnumbering unpigmented species by nearly a factor of 7. We examined three possible macroevolutionary explanations for this pattern: (1) asymmetric transition rates; (2) low transition rates preventing the flower colors from reaching equilibrium; and (3) differential diversification. In order to discriminate among these explanations, we employ the newly-developed Binary-State Speciation and Extinction (BiSSE) model which jointly estimates transition rates among states and the speciation and extinction rates in each state. Using maximum likelihood and Bayesian BiSSE estimation, we find no evidence for asymmetrical transition rates. Also, BiSSE simulations of character evolution demonstrate that the estimated transition rates tend to produce a much higher proportion of white species than we observe in Quamoclit, suggesting that low-transition rates do not fully account for the paucity of white species. In contrast, we find support for the differential diversification hypothesis with the rate of speciation in pigmented lineages estimated as three-fold greater than the rate in unpigmented lineages. Our analyses thus indicate the low frequency of white-flowered morning glory species is due largely to lineage selection. Our analysis also suggests that estimating character transition rates without simultaneously estimating speciation and extinction rates can lead to greatly biased estimates.} }

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