title: Historical reconstruction of climatic and elevation preferences and the evolution of cloud forest-adapted tree ferns in Mesoamerica.
abstract: BACKGROUND
  Cloud forests, characterized by a persistent, frequent or seasonal low-level cloud cover and fragmented distribution, are one of the most threatened habitats, especially in the Neotropics. Tree ferns are among the most conspicuous elements in these forests, and ferns are restricted to regions in which minimum temperatures rarely drop below freezing and rainfall is high and evenly distributed around the year. Current phylogeographic data suggest that some of the cloud forest-adapted species remainedin situor expanded to the lowlands during glacial cycles and contracted allopatrically during the interglacials. Although the observed genetic signals of population size changes of cloud forest-adapted species including tree ferns correspond to predicted changes by Pleistocene climate change dynamics, the observed patterns of intraspecific lineage divergence showed temporal incongruence.
  
  
  METHODS
  Here we combined phylogenetic analyses, ancestral area reconstruction, and divergence time estimates with climatic and altitudinal data (environmental space) for phenotypic traits of tree fern species to make inferences about evolutionary processes in deep time. We used phylogenetic Bayesian inference and geographic and altitudinal distribution of tree ferns to investigate ancestral area and elevation and environmental preferences of Mesoamerican tree ferns. The phylogeny was then used to estimate divergence times and ask whether the ancestral area and elevation and environmental shifts were linked to climatic events and historical climatic preferences.
  
  
  RESULTS
  Bayesian trees retrievedCyathea, Alsophyla, GymnosphaeraandSphaeropterisin monophyletic clades. Splits for species in these genera found in Mesoamerican cloud forests are recent, from the Neogene to the Quaternary, Australia was identified as the ancestral area for the clades of these genera, except forGymnosphaerathat was Mesoamerica. Climate tolerance was not divergent from hypothesized ancestors for the most significant variables or elevation. For elevational shifts, we found repeated change from low to high elevations.
  
  
  CONCLUSIONS
  Our data suggest that representatives of Cyatheaceae main lineages migrated from Australia to Mesoamerican cloud forests in different times and have persisted in these environmentally unstable areas but extant species diverged recentrly from their ancestors.
authors.affiliation: Departamento de Biología Evolutiva, Instituto de Ecología AC, Carretera antigua a Coatepec, El Haya, Xalapa, Veracruz, Mexico.
authors.forename: Victoria
authors.initials: V
authors.lastname: Sosa
authors.affiliation: Departamento de Biología Evolutiva, Instituto de Ecología AC, Carretera antigua a Coatepec, El Haya, Xalapa, Veracruz, Mexico.
authors.forename: Juan Francisco
authors.initials: JF
authors.lastname: Ornelas
authors.affiliation: Departamento de Biología Evolutiva, Instituto de Ecología AC, Carretera antigua a Coatepec, El Haya, Xalapa, Veracruz, Mexico.
authors.forename: Santiago
authors.initials: S
authors.lastname: Ramírez-Barahona
authors.affiliation: Departamento de Biología Evolutiva, Instituto de Ecología AC, Carretera antigua a Coatepec, El Haya, Xalapa, Veracruz, Mexico.|Instituto de Ciencias/Herbario y Jardín Botánico, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico.
authors.forename: Etelvina
authors.initials: E
authors.lastname: Gándara
keywords: Biogeography; Climate tolerance; Cloud forest; Cyatheaceae; Elevational shifts; Neogene; Neotropics; Pleistocene; Quaternary; Tree ferns