A Tale of Two Hyper-diversities: Diversification dynamics of the two largest families of lichenized fungi.

Ekaphan Kraichak,Matthew P Nelsen,Ana Crespo,H Thorsten Lumbsch,Steven D Leavitt,Pradeep K Divakar,Robert Lücking

doi:10.1038/srep10028

Abstract

Renewed interests in macroevolutionary dynamics have led to the proliferation of studies on diversification processes in large taxonomic groups, such as angiosperms, mammals, and birds. However, such a study has yet to be conducted in lichenized fungi – an extremely successful and diverse group of fungi. Analysing the most comprehensive time-calibrated phylogenies with a new analytical method, we illustrated drastically different diversification dynamics between two hyper-diverse families of lichenized fungi, Graphidaceae and Parmeliaceae, which represent more than a fourth of the total species diversity of lichenized fungi. Despite adopting a similar nutrition mode and having a similar number of species, Graphidaceae exhibited a lower speciation rate, while Parmeliaceae showed a sharp increase in speciation rate that corresponded with the aridification during the Oligocene-Miocene transition, suggesting their adaptive radiation into a novel arid habitat.

Highlights

Renewed interests in macroevolutionary dynamics have led to the proliferation of studies on diversification processes in large taxonomic groups, such as angiosperms, mammals, and birds
If a partnership with photosynthetic organisms is a successful nutritional mode for fungi, why are not all lichenized fungi more or less diverse? Do the two largest families share some of the same underlying mechanisms to achieve such a high level of diversity? In this study, we investigated diversification dynamics of the two largest families of lichenized fungi – Graphidaceae and Parmeliaceae – by examining the rates and timing of diversification to ascertain whether similar mechanisms are operating in these two hugely successful lineages of lichenized fungi
Under a relaxed molecular clock model, we estimated the ages of the families Graphidaceae and Parmeliaceae at around 176 and 102 million years ago (MYA), respectively

Summary

Introduction

Renewed interests in macroevolutionary dynamics have led to the proliferation of studies on diversification processes in large taxonomic groups, such as angiosperms, mammals, and birds. Recent advances in phylogenetic reconstruction and comparative methods have renewed interest in macroevolutionary dynamics of large taxonomic groups, such as in plants[1,2,3], mammals[4], and birds[5] These studies have provided additional insights into timing and processes of diversification – a research program that has traditionally been pursued from a mostly paleontological perspective[6]. The overall success of lichenized state is hypothesised to play a critical role in early terrestrial ecosystems[9] and, in many cases, was shown to correlate with paleoclimatic events, such as global cooling and drying[10,11] This successful symbiosis has led to a wide range of growth forms and habitat preferences. Beyond this limited number of studies, our understanding of how different lichenization events contribute to diversification remains largely incomplete

Methods

Results

Conclusion