Different diversification histories in tropical and temperate lineages in the ascomycete subfamily Protoparmelioideae (Parmeliaceae)

Abstract

Background: Environment and geographic processes affect species' distributions as well as evolutionary processes, such as clade diversification. Estimating the time of origin and diversification of organisms helps us understand how climate fluctuations in the past might have influenced the diversification and present distribution of species. Complementing divergence dating with character evolution could indicate how key innovations have facilitated the diversification of species. Methods: We estimated the divergence times within the newly recognised subfamily Protoparmelioideae (Ascomycota) using a multilocus dataset to assess the temporal context of diversification events. We reconstructed ancestral habitats and substrate using a species tree generated in *Beast. Results: We found that the diversification in Protoparmelioideae occurred during the Miocene and that the diversification events in the tropical clade Maronina predate those of the extratropical Protoparmelia. Character reconstructions suggest that the ancestor of Protoparmelioideae was most probably a rock-dwelling lichen inhabiting temperate environments. Conclusions: Major diversification within the subtropical/tropical genus Maronina occurred between the Paleocene and Miocene whereas the diversifications within the montane, arctic/temperate genus Protoparmelia occurred much more recently, i.e. in the Miocene.

Keywords: Diversification pattern; ancestral state reconstruction; dating; extra-tropical; habitat; lichenised fungi; mountain uplifts; parallel evolution; substrate.

Figure 1.

Time-calibrated phylogeny of the major lineages of Lecanorales (Lecanoraceae, Parmeliaceae, Ramboldiaceae, and Gypsoplacaceae), based on a six-locus dataset, dataset 1 (Singh et al. 2015). Cladoniaceae was used as outgroup (Arup et al. 2007, Singh et al. 2013). Mean node age, 95% highest posterior density (HPD) and posterior probability (PP) were mapped on the maximum clade credibility tree. The red circle indicates the calibration point, i.e. the split between Protoparmelioideae and Parmelioideae. Only the strongly supported nodes were considered for divergence time estimates. Geological times are indicated at the axis of the tree. The number of specimens per species is indicated in brackets in front of the taxon names. The scale at the bottom of the tree represents age in millions of years (Ma). Parmelioideae, Gypsoplacaceae, Cladoniaceae, Ramboldiaceae and Lecanoraceae clades are collapsed. In Parmelioideae, Miriquidica and Protoparmelia s. l. clades are collapsed at the species level.

Figure 2.

Ancestral states in Protoparmelioideae: Chronogram based on a six-locus dataset, dataset 2 (Singh et al. 2017), representing a species tree of Protoparmelioideae showing the ancestral states at nodes of interest. The topology is derived from the *BEAST species tree. A consensus tree was generated in TreeAnnotator. The current substrate of each species is indicated by the coloured circles in front of the name of the species. Polymorphic taxa have more than one coloured circle. Nodes at which ancestral states are reconstructed are numbered from 1 to 5. Pie charts indicate probabilities of each ancestor being in each of the two potential states at nodes of interest. The circles above the node represent bootstrap support for each character state and the circles at the bottom represent the posterior probability. A) Ancestral habitat: cold (blue), warm (red) and B) Ancestral substrate: rock (brown), bark (green).