Abstract
In this study, the influence of geographic isolation on the levels of morphological and genetic differentiation among populations of the karst forest-adapted Pilea pteridophylla (Urticaceae) was evaluated. Based on our results, there is a strong morphological differentiation among the only two know populations of Pilea pteridophylla. Both populations can be clearly differentiated based on vegetative and reproductive characters, and the observed variation is geographically structured. Moreover, our genetic data from the chloroplast genome show strong levels of population differentiation and no shared haplotypes were observed between populations. Also, our estimation of divergence times supports a long-term isolation hypothesis between populations. Based on our results, dispersal seed limitation, long-term forest isolation and topographic heterogeneity (local adaptation) are related to high levels of endemism and species turnover in the mountain karst forests of Mexico.
Keywords: Endemic, Neotropics, Mexico, Phylogeography, Speciation, Tropical rainforest
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| Pilea monroi Ortiz-Rodr. and Lagos-Báez (Urticaceae). A Habit, plant with pistillate inflorescences. B Stem, a leafless portion with inflorescences. C Flower bud. D Staminate flower with four stamens and four tepals. E Infructescence. F Stem portion with pistillate inflorescences. Drawn by Robin Pérez Lucas based on Lagos-Báez 57 (MEXU) |
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| Pilea monroi Ortiz-Rodr. and Lagos-Báez & Pilea pteridophylla A. K. Monro B Individual from the Chiapas population (Blue). C Individual from the Tabasco population (Red) |
Pilea monroi Ortiz-Rodr. & Lagos-Báez sp. nov.
Similar to Pilea pteridophylla in general fern-like appearance, but clearly differentiated by its dentate (vs. pectinate) leaves, and larger stem and leaf size. Furthermore, they are allopatrically distributed and under different environmental conditions.
Etymology: Pilea monroi named in honour of Dr Alex Monro, taxonomist, specialist in the genus Pilea (Urticaceae) and especially interested in the study of the plant diversity in the karstic forests of America and China.
Notes: Pilea monroi is the only species in Mexico with linear lanceolate, deeply dentate leaves, and like Pilea pteridophylla, its fern-like appearance makes it easily distinguishable from other species. However, the leaf margins of Pilea monroi are dentate and not pectinate as in Pilea pteridophylla.
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