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A Total Evidence Approach to Understanding Phylogenetic Relationships and Ecological Diversity in Selanginella subg. Tetragonostachys
Arrigo, Nils Therrien, James Anderson, Cajsa Lisa Windham, Michael D. Haufler, Christopher H. Barker, Michael S.
Arrigo, Nils
Therrien, James
Anderson, Cajsa Lisa
Windham, Michael D.
Haufler, Christopher H.
Barker, Michael S.
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Abstract
• Premise of the Study: Several members of Selaginella are renowned for their ability to survive extreme drought and “resurrect”
when conditions improve. Many of these belong to subgenus Tetragonostachys , a group of ~45 species primarily found in
North and Central America, with substantial diversity in the Sonoran and Chihuahuan Deserts. We evaluated the monophyly
and the age of subgenus Tetragonostachys and assess how drought tolerance contributed to the evolution of this clade.
• Methods: Our study included most Tetragonostachys species, using plastid and nuclear sequences, fossil and herbarium records,
and climate variables to describe the species diversity, phylogenetic relationships, divergence times, and climatic niche
evolution in the subgenus.
• Key Results: We found that subgenus Tetragonostachys forms a monophyletic group sister to Selaginella lepidophylla and may
have diverged from other Selaginella because of a Gondwanan–Laurasian vicariance event ca. 240 mya. The North American
radiation of Tetragonostachys appears to be much more recent and to have occurred during the Early Cretaceous–late Paleocene
interval. We identifi ed two signifi cant and nested ecological niche shifts during the evolution of Tetragonostachys associated
with extreme drought tolerance and a more recent shift to cold climates. Our analyses suggest that drought tolerance
evolved in the warm deserts of southwest North America and may have been advantageous for colonization of cold and dry
boreal climates.
• Conclusions: Our investigation provides a foundation for future research addressing the genomics of ecological niche evolution
and the potential role of reticulate evolution in Selaginella subgenus Tetragonostachys .
Description
Date
2013-08
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Publisher
Botanical Society of America
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Keywords
Ecological niche shift, Lycophyte, Ornstein-Uhlenbeck models, Selaginella, Sonoran Deser
Citation
Nils Arrigo et al. (2013). A total evidence approach to understanding
phylogenetic relationships and ecological diversity in Selaginella subg.
Tetragonostachys. American Journal of Botany 100(8):1672-82
http://www.dx.doi.org/10.3732/ajb.1200426