Glacial refugia and migration routes of the Neotropical genus Trizeuxis (Orchidaceae)

Marta Kolanowska

doi:10.5586/asbp.2013.024

Abstract

The morphology and anatomy of the monotypic genus Trizeuxis make this taxon almost impossible to recognize in fossil material and hereby difficult object of historical geographic studies. To estimate the distribution of potential refugia during the last glacial maximum and migration routes for Trizeuxis the ecological niche modeling was performed. The potential niche modeling was done using maximum entropy method implemented in Maxent application based on the species presence-only observations. As input data climatic variables and the digital elevation model were used. Two models of suitable glacial habitats distribution were prepared – for the studied species and for its host. The compiled map of the suitable habitats distribution of T. falcata and P. guajava during the last glacial maximum (LGM) indicate two possible refugia for the studied orchid genus. The first one was located in the Madre de Dios region and the other one in the Mosquito Coast. The models suggest the existence of two migration routes of Trizeuxis species. The results indicate that the ecological niche modeling (ENM) is a useful tool for analyzing not only the possible past distribution of the species, but may be also applied to determine the migration routes of the organisms not found in the fossil material.

Highlights

John Lindley described orchid genus Trizeuxis in 1821 [1] based on its conduplicate leaves, small, non-resupinate flowers arranged in the paniculate inflorescence with 3-lobed lip parallel to gynostemium and excavate stigma
Glacial refugia The compiled map of the suitable habitats distribution of T. falcata and P. guajava during the last glacial maximum (LGM) indicate just two regions, which could be the possible refugia for the studied orchid genus (Fig. 3)
The second probable refugium was located in the Mosquito Coast lowlands corresponded to the tropical savanna and woodland characterized by 60–20% cover of vegetation during the LGM [30]

Summary

Introduction

John Lindley described orchid genus Trizeuxis in 1821 [1] based on its conduplicate leaves, small, non-resupinate flowers arranged in the paniculate inflorescence with 3-lobed lip parallel to gynostemium and excavate stigma. In the same paper Lindley provided the description of Trizeuxis falcata L. In 1922 Schlechter described second species of the genus, T. andina, based on the specimen characterized by the lip difficult to expand with short and thick gynostemium [2], but those small differences observed in just one specimen cited by the author were recognized by taxonomists as an infraspecific variation of T. falcata [3]. The genus is a representative of oncidioid orchids, which classification is one of the most intractable group within Orchidaceae. The scientists do not agree about the taxonomic affinity of the genus.

Methods

Results

Conclusion