Diversity, Phylogeny, and historical biogeography of the genus Coccocarpia (lichenized Ascomycota: Peltigerales) in the tropics.

Abstract

Coccocarpia Pers. currently comprises 28 mostly broadly distributed tropical species of fungi associated with cyanobacteria. Three of these taxa, C. erythroxyli, C. palmicola, and C. pellita, are presumably pantropical to subcosmopolitan, with broad morphological variation across their range. This study provides the first global phylogeny of the genus, to test current species concepts and infer distribution patterns, based on samples from Colombia, Puerto Rico, Gabon, Kenya, Thailand, Fiji, and Hawaii. We also estimate divergence times within the clade and provide a first reconstruction of its biogeographic history. Based on phylogenetic reconstructions inferred from maximum likelihood and Bayesian approaches of four molecular markers (mtSSU, nuLSU, ITS, RPB2), Coccocarpia was recovered as monophyletic. However, the currently accepted taxa are largely polyphyletic entities and the underlying diversity in this genus is much higher than currently understood. Different methods for species delimitation boundaries came to agree on a scenario involving more than 150 species in the available, albeit still small, dataset. This suggests that with broader sampling, Coccocarpia may indeed represent a hyper-diverse genus, potentially containing over 200 species. The phylogeny is geographically structured: one clade is exclusive to the Paleotropics, one to the Neotropics, and one is pantropical. Coccocarpia likely emerged during the Late Cretaceous (90 ± 10 Mya) in the tropical regions of Australasia-Oceania, initially colonizing Oceania, and Asia and subsequently the Neotropics. The three main clades diverged between the Late Cretaceous and the Paleocene, with significant diversification in the Oligocene, during which the neotropical clade gave rise to morphological novelties, including the epiphylla and stellata clades.