Poster

Title: Temporal shifts in diversification rate from a molecular phylogeny of a cosmopolitan family of mycorrhizal mushrooms (Inocybaceae)

Authors:
P. Brandon Matheny, Department of Ecology and Evolutionary Biology, University of Tennessee, and David S. Hibbett, Biology Department, Clark University

Abstract:
About 700 species have been described in the Inocybaceae, a species-rich
family of mycorrhizal fungi that forms root symbioses with diverse angiosperms
and conifers throughout the world. We wish to test the null hypothesis that the
rate of diversification in the Inocybaceae has been constant over time. If
rejected, we would like to determine the timing of such shifts. To do this, we
assembled a multi-gene data set for 189 taxa and reconstructed an ultrametric
phylogenetic tree under a Bayesian relaxed molecular clock model in the
program BEAST. LASER is a package in the R programming language
environment that performs a maximum likelihood analysis of speciation and
extinction rates, and fits rate-variable models to phylogenetic data contrasting
the likelihood of these data to those produced by constant rate models. If internal
nodes are dated, temporal shifts in diversification rate can be estimated. Our
results support rapid diversification of Inocybaceae most likely during the early
Tertiary, but show a significant decrease in diversification during the Oligocene,
a period marked by global cooling, massive vegetational changes, and significant
extinctions. A sharp increase in speciation ensued during the Miocene. Though
fossils of Inocybaceae are lacking, molecular data can be utilized in combination
with diversification models to draw inferences about macro-evolutionary patterns
in fungi.