Inferring phylogeny and speciation of Gymnosporangium species, and their coevolution with host plants.

Peng Zhao,Fang Liu,Ying-Ming Li,Lei Cai

doi:10.1038/srep29339

Peng Zhao, Fang Liu + Show 2 more

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https://doi.org/10.1038/srep29339

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Abstract

Gymnosporangium species (Pucciniaceae, Pucciniales) cause serious diseases and significant economic losses to apple cultivars. Most of the reported species are heteroecious and complete their life cycles on two different plant hosts belonging to two unrelated genera, i.e. Juniperus and Malus. However, the phylogenetic relationships among Gymnosporangium species and the evolutionary history of Gymnosporangium on its aecial and telial hosts were still undetermined. In this study, we recognized species based on rDNA sequence data by using coalescent method of generalized mixed Yule-coalescent (GMYC) and Poisson Tree Processes (PTP) models. The evolutionary relationships of Gymnosporangium species and their hosts were investigated by comparing the cophylogenetic analyses of Gymnosporangium species with Malus species and Juniperus species, respectively. The concordant results of GMYC and PTP analyses recognized 14 species including 12 known species and two undescribed species. In addition, host alternations of 10 Gymnosporangium species were uncovered by linking the derived sequences between their aecial and telial stages. This study revealed the evolutionary process of Gymnosporangium species, and clarified that the aecial hosts played more important roles than telial hosts in the speciation of Gymnosporangium species. Host switch, losses, duplication and failure to divergence all contributed to the speciation of Gymnosporangium species.

Highlights

The first report of Gymnosporangium in China was G. corniforme on J. formosana[18]
Recent phylogenetic studies confirmed the monophyly of the genus Gymnosporangium[24,26,30]
Our results from PTP and GMYC models recognized 14 Gymnosporangium species associated with its aecial host on genus Malus

Summary

Introduction

The first report of Gymnosporangium in China was G. corniforme on J. formosana[18]. Subsequently, described species in Gymnosporangium gradually increased to five[19,20]. In the genus Gymnosporangium, controversial opinions were hold among researchers toward the evolutionary relationships with host species. Based on the phylogenetic relationship of several Gymnosporangium species, Novick[26] thought host switching rather than cospeciation was the primary speciation model in the group. Because only very limited Gymnosporangium species were included in their studies, the evolutionary history and speciation mode of Gymnosporangium species on Malus species remains largely unknown. The objectives of the current study are: 1) to conduct the species delimitation analyses for Gymnosporangium species; 2) to clarify the host alternation of these recognized Gymnosporangium species on Malus; 3) to conduct the cophylogenetic analyses of Gymnosporangium species with their aecial host and telial host respectively; 4) to infer the speciation modes (cospeciation, duplication, host switch, loss and failure to diverge) of Gymnosporangium species

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