@ARTICLE{TreeBASE2Ref24323, author = {Juan Carlos Villarreal and Susanne S Renner and Natalie Cusimano}, title = {Biogeography and diversification rates in hornworts: The limitations 1 of diversification modeling}, year = {2015}, keywords = {biogeography; diversification modeling; extinction rates; geographic disjunctions; hornworts}, doi = {10.12705/642.7}, url = {http://}, pmid = {}, journal = {Taxon}, volume = {}, number = {}, pages = {}, abstract = { Hornworts comprise ca. 220 species and are among the oldest landplant lineages, even though their precise phylogenetic position remains unclear. Deep within-hornwort divergences, highly uneven species numbers/genus, and the assumed high stem age together suggest a history of changing diversification (i.e., speciation minus extinction) rates. To study the geographic distribution of modern hornworts and their patterns of species accumulation, we generated a mitochondrial and plastid DNA matrix for 103 species representing all major groups and then applied molecular-clock dating, using a different calibration approach than in earlier work. We used the BAMM software to fit rate-variable and constant-rate birth-death diversification models to the dataset, and we also inferred ancestral areas to a time depth of 55 Myr (Early Eocene). We analyzed diversification rates for all hornworts and separately for species-rich subclades. Under BAMM?s variable-rates model (which fits the data better than a constant-rate birth-death model, but still assumes that each species has the same speciation and extinction probability regardless of its age), hornworts have gradually increasing rates of speciation and a constant background extinction rate. No shifts in diversification rate could be detected. The implausible finding of a constant background extinction rate illustrates the limitations of diversification modeling especially as regards extinction rates. } }

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