Phylogenetic analysis of the angiosperm-floricolous insect–yeast association: Have yeast and angiosperm lineages co-diversified?

摘要

Metschnikowia (Saccharomycetales, Metschnikowiaceae/Metschnikowia clade) is an ascomycetous yeast\udgenus whose species are associated mostly with angiosperms and their insect pollinators over all continents.\udThe wide distribution of the genus, its association with angiosperm flowers, and the fact that it\udincludes some of the best-studied yeasts in terms of biogeography and ecology make Metschnikowia an\udexcellent group to investigate a possible co-radiation with angiosperm lineages. We performed phylogenetic\udanalyses implementing Bayesian inference and likelihood methods, using a concatenated matrix\ud( 2.6 Kbp) of nuclear DNA (ACT1, 1st and 2nd codon positions of EF2, Mcm7, and RPB2) sequences. We\udincluded 77 species representing approximately 90% of the species in the family. Bayesian and parsimony\udmethods were used to perform ancestral character reconstructions within Metschnikowia in three key\udmorphological characters. Patterns of evolution of yeast habitats and divergence times were explored\udin the Metschnikowia clade lineages with the purpose of inferring the time of origin of angiosperm-associated\udhabitats within Metschnikowiaceae. This paper presents the first phylogenetic hypothesis to\udinclude nearly all known species in the family. The polyphyletic nature of Clavispora was confirmed\udand Metschnikowia species (and their anamorphs) were shown to form two groups: one that includes\udmostly floricolous, insect-associated species distributed in mostly tropical areas (the large-spored Metschnikowia\udclade and relatives) and another that comprises more heterogeneous species in terms of habitat\udand geographical distribution. Reconstruction of character evolution suggests that sexual characters\ud(ascospore length, number of ascospores, and ascus formation) evolved multiple times within Metschnikowia.\udComplex and dynamic habitat transitions seem to have punctuated the course of evolution of the\udMetschnikowiaceae with repeated and independent origins of angiosperm-associated habitats. The origin\udof the family is placed in the Late Cretaceous (71.7 Ma) with most extant species arising from the Early\udEocene. Therefore, the Metschnikowiaceae likely radiated long after the Mid-Cretaceous radiations of\udangiosperms and their diversification seems to be driven by repeated radiation on a pre-existing diverse\udresource