Miocene and Pliocene dominated diversification of the lichen-forming fungal genus Melanohalea (Parmeliaceae, Ascomycota) and Pleistocene population expansions
- Steven D LeavittAffiliated withDepartment of Botany, The Field Museum Email author
- , Theodore L EsslingerAffiliated withDepartment of Biological Sciences #2715, North Dakota State University
- , Pradeep K DivakarAffiliated withDepartamento de Biología Vegetal II, Facultad de Farmacia, Universidad Complutense de Madrid
- , H Thorsten LumbschAffiliated withDepartment of Botany, The Field Museum
Factors promoting diversification in lichen symbioses remain largely unexplored. While Pleistocene events have been important for driving diversification and affecting distributions in many groups, recent estimates suggest that major radiations within some genera in the largest clade of macrolichens (Parmeliaceae, Ascomycota) vastly predate the Pleistocene. To better understand the temporal placement and sequence of diversification events in lichens, we estimated divergence times in a common lichen-forming fungal genus, Melanohalea, in the Northern Hemisphere. Divergence times were estimated using both concatenated gene tree and coalescent-based multilocus species tree approaches to assess the temporal context of major radiation events within Melanohalea. In order to complement our understanding of processes impacting genetic differentiation, we also evaluated the effects of Pleistocene glacial cycles on population demographics of distinct Melanohalea lineages, differing in reproductive strategies.
We found that divergence estimates, from both concatenated gene tree and coalescent-based multilocus species tree approaches, suggest that diversification within Melanohalea occurred predominantly during the Miocene and Pliocene, although estimated of divergence times differed by up to 8.3 million years between the two methods. These results indicate that, in some cases, taxonomically diagnostic characters may be maintained among divergent lineages for millions of years. In other cases, similar phenotypic characters among non-sister taxa, including reproductive strategies, suggest the potential for convergent evolution due to similar selective pressures among distinct lineages. Our analyses provide evidence of population expansions predating the last glacial maximum in the sampled lineages. These results suggest that Pleistocene glaciations were not inherently unfavorable or restrictive for some Melanohalea species, albeit with apparently different demographic histories between sexually and vegetatively reproducing lineages.
Our results contribute to the understanding of how major changes during the Miocene and Pliocene have been important in promoting diversification within common lichen-forming fungi in the northern Hemisphere. Additionally, we provide evidence that glacial oscillations have influenced current population structure of broadly distributed lichenized fungal species throughout the Holarctic.
KeywordsBayesian skyline plot BEAST Divergence times Coalescence Concatenation Lichens Melanohalea Pleistocene Reproductive strategy Species tree
- Miocene and Pliocene dominated diversification of the lichen-forming fungal genus Melanohalea (Parmeliaceae, Ascomycota) and Pleistocene population expansions
- Open Access
- Available under Open Access This content is freely available online to anyone, anywhere at any time.
BMC Evolutionary Biology
- Online Date
- September 2012
- Online ISSN
- BioMed Central
- Additional Links
- Bayesian skyline plot
- Divergence times
- Reproductive strategy
- Species tree
- Author Affiliations
- 1. Department of Botany, The Field Museum, 1400 S. Lake Shore Drive, Chicago, IL, 60605, USA
- 2. Department of Biological Sciences #2715, North Dakota State University, PO Box 6050, Stevens Hall, Fargo, ND, 58108-6050, USA
- 3. Departamento de Biología Vegetal II, Facultad de Farmacia, Universidad Complutense de Madrid, Madrid, 28040, Spain