The patterns of geographic differentiation in fern species have been linked to climatic differences across regions and the distribution of available habitat. In this paper, the association between some climatic features and patterns of geographic differentiation in American tree ferns was evaluated. For this, the occurrence ranges of 190 species were plotted and then analysed using track analysis. Here we identify six generalised tracks that span the main highland regions of tropical America: the Andes, the Guyana Highlands, the Brazilian Atlantic coast, lower Central America, the Greater Antilles, and upper Central America-Mexico. We did not find an association between cloud forest habitat and the differentiation pattern revealed by generalised tracks in Central America. Instead, these patterns are congruent with well-documented geological boundaries in the region. Climatic variables associated with cloud forest habitat were extracted from each generalised track and subjected to ANOVA, showing that most tracks have equivalent climates. The Andean track showed significant climatic differences with the Brazilian and Guyanan tracks, which were associated with main habitat discontinuities. From these results, we propose that historical isolation has been important in promoting geographical differentiation in tree ferns and that differentiation by dispersal cannot fully explain the large-scale geographical patterns observed in tree ferns.
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Vol. 105 • No. 2