From tree tops to the ground: reversals to terrestrial habit inGaleandraorchids (Epidendroideae: Catasetinae)

Abstract

The colonization of the epiphytic niche of tropical forest canopies played an important role in orchid’s extraordinary diversification in the Neotropics. However, reversals to the terrestrial habit occurred sparsely in species of Epidendroideae. To better understand which factors might have been involved in reversals to terrestrial habits in the predominantly epiphytic Epidendroideae, we investigate Galeandra diversification in time and space. We hypothesized that the reversal to the terrestrial habitat is linked to the origin of open vegetation habitats in South America. We generated a time-calibrated phylogeny based on a matrix of 17 out of 20 species of Galeandra plus outgroups and seven DNA markers. We found that Galeandra originated towards end of the Miocene, about 10 Ma in Amazonia (including the Guiana Shield). The terrestrial clade originated synchronously with the rise of dry vegetation biomes, suggesting that aridification during the last 5 million years dramatically impacted the diversification of epiphytic lineages in the Neotropics. Habit is correlated with floral spur lengths and geographic range size. The longer spurs and narrower ranges are found in epiphytic species: probably adapted to a specialized pollination mode, associated to the long-tongued Euglossini bees, which also prefer forested habits. The terrestrial species presents variable floral spurs and wide distribution ranges, with evidence of self-pollination, suggesting the loss of specialized pollination system and concomitant range expansion.

Plastid phylogenomics resolves ambiguous relationships within the orchid family and provides a solid timeframe for biogeography and macroevolution

“…Occurring from alpine ecosystems to grasslands, they have conquered virtually all ecosystems available in any elevational gradient [35][36][37] , showing independent transitions to terrestrial, rupicolous and epiphytic habit. Moreover, they have evolved a diverse array of pollination systems [38][39][40] , rewarding species offering scent, oil and nectar, and even food-and sexual deceptive species 41,42 .…”

Phylogenomic analysis points to a South American origin of Manihot and illuminates the primary gene pool of cassava

“…De‐Nova et al ., 2012). Such a pattern in which North/Central American lineages are found nested within a predominantly South American group is also found in several other neotropical lineages, such as Mimosa (Fabaceae; Simon et al ., 2011), Gochnatieae (Asteraceae; Funk et al ., 2014), Caesalpinia group (Fabaceae; Gagnon et al ., 2019), and Galeandra (Orchidaceae; Martins et al ., 2018). This biogeographic pattern can be attributed to long‐distance dispersal from South America to North/Central America, or terrestrial migration after the closure of the Panama Isthmus, which is thought to have occurred c .…”

Vascular epiphytes in the Amazon: main gaps, limitations and perspectives for studies on the subject

“…Even the anatomical studies were carried out with the objective of contributing to the taxonomic differentiation of species and clarification of the dynamics of geographic distribution of the taxa. More recently, taxonomic and phylogenetic studies began to include more robust analyses to confirm the expansion of the geographic distribution of taxa and evolution of adaptive strategies (Martins et al 2018;Smidt et al 2021).…”