A TOTAL EVIDENCE APPROACH TO UNDERSTANDING PHYLOGENETIC RELATIONSHIPS AND ECOLOGICAL DIVERSITY IN SELAGINELLA SUBG. TETRAGONOSTACHYS

• 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 similar to 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 identified two significant 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.

Ämnesord

NATURVETENSKAP  -- Biologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences (hsv//eng)

Nyckelord

Ecological niche shift

lycophyte

Ornstein-Uhlenbeck models

Selaginella

Sonoran Desert

DIVERGENCE TIMES

HERBACEOUS LYCOPSIDS

SEQUENCE ALIGNMENTS

MOLECULAR

EVOLUTION

ABSOLUTE RATES

DIVERSIFICATION

SELECTION

HISTORY

PLANTS

TREES

LOUIS

MISSOURI

V91

P150

RATIGRAPHY FROM THE NORTH AMERICAN CORDILLERA

V442

P313

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