Host jumps shaped the diversity of extant rust fungi (Pucciniales)

Abstract

SummaryThe aim of this study was to determine the evolutionary time line for rust fungi and date key speciation events using a molecular clock. Evidence is provided that supports a contemporary view for a recent origin of rust fungi, with a common ancestor on a flowering plant.Divergence times for > 20 genera of rust fungi were studied with Bayesian evolutionary analyses. A relaxed molecular clock was applied to ribosomal and mitochondrial genes, calibrated against estimated divergence times for the hosts of rust fungi, such as Acacia (Fabaceae), angiosperms and the cupressophytes.Results showed that rust fungi shared a most recent common ancestor with a mean age between 113 and 115 million yr. This dates rust fungi to the Cretaceous period, which is much younger than previous estimations. Host jumps, whether taxonomically large or between host genera in the same family, most probably shaped the diversity of rust genera. Likewise, species diversified by host shifts (through coevolution) or via subsequent host jumps. This is in contrast to strict coevolution with their hosts.Puccinia psidii was recovered in Sphaerophragmiaceae, a family distinct from Raveneliaceae, which were regarded as confamilial in previous studies.

Cryptic diversity in Tranzscheliella spp. (Ustilaginales) is driven by host switches

“…Cospeciation was traditionally the main explanation for host-parasite cophylogenies1516. With more available data and improved tools for cophylogenetic analyses, host switches rather than cospeciation, has become currently the most likely explanation for the diversification of many parasites, including fungal pathogens1718. Host-shift speciation rather than cospeciation explained the cophylogenetic patterns of the smut fungus genus Anthracoidea found on species of the genus Carex (Cyperaceae)19.…”

The intriguing and convoluted life of a heteroecious rust fungus in New Zealand

“…Melampsoraceae (100% MLBS) was recovered in a highly supported clade (100% MLBS) with Pucciniastraceae (77% MLBS) and Coleosporiaceae (93% MLBS), which is similar to previously recovered topologies (e.g. McTaggart et al ., ). The 10 isolates mentioned above were recovered in a highly supported clade (100% MLBS).…”

“…Recent studies (e.g. McTaggart et al ., ) have demonstrated that host jumping appears to have a dominant influence in diversification of rust species. In the case of P. otagensis , it can be reasonably confidently assumed that the species spread to R. ×rhabarbarum and R. sagittatus in New Zealand within the last 60–150 years, which was when these plants were putatively introduced into the country.…”

A dynamic, web-based resource to identify rust fungi (Pucciniales) in southern Africa

“…It is interesting that two new rusts were found on introduced, well-studied plants in southern Africa. Host jumps were found to be one of the main drivers of speciation for rust fungi (McTaggart et al 2016b), and host shifts or jumps from native plant species in South Africa to introduced species may explain the observed new taxa on exotic, well-studied hosts.…”