The Improbable Journeys of Epiphytic Plants Across The Andes: Historical Biogeography ofCycnoches(Catasetinae, Orchidaceae)

Abstract

The Andean uplift is one of the major orographic events in the New World and has impacted considerably the diversification of numerous Neotropical organisms. Despite its importance for biogeography, the specific role of mountain ranges as a dispersal barrier between South and Central American lowland plant lineages is still poorly understood. The swan orchids (Cycnoches) comprise ca 34 epiphytic species distributed in lowland and pre-montane forests of Central and South America. Here, we study the historical biogeography of Cycnoches to better understand the impact of the Andean uplift on the diversification of Neotropical lowland plant lineages. Using novel molecular sequences (five nuclear and plastid regions) and twelve biogeographic models with and without founder-event speciation, we infer that the most recent common ancestor of Cycnoches may have originated in Amazonia ca 5 Mya. The first colonization of Central America occurred from a direct migration event from Amazonia, and multiple bidirectional trans-Andean migrations between Amazonia and Central America took place subsequently. Notably, such biological exchange occurred well after major mountain building periods. The Andes have not acted as an impassable barrier for epiphytic lowland lineages such as orchids having a great potential for effortless dispersal because of the very light, anemochorous seeds.

Recent origin and rapid speciation of Neotropical orchids in the world's richest plant biodiversity hotspot

“…(,b), Pérez‐Escobar et al . (), and Ramírez et al . (), using the R‐package megaptera v.1.0 (available at https://github.com/cran/megaptera.git).…”

“…Annonaceae, Pirie et al ., ; Rubiaceae, Antonelli et al ., ; or Fabaceae, Pennington et al ., ). This result probably relates to the biology of orchids, which produce large amounts of dust‐like, wind‐dispersed seeds, allowing for occasional long‐distance dispersal (Arditti & Ghani, ; Antonelli et al ., ; Barthlott et al ., ; Givnish et al ., ; Pérez‐Escobar et al ., ), enabling occasional crossing of the Andes, and perhaps more frequently migration to different elevation zones. Taken together, these findings suggest that the Andes constitutes a semipermeable barrier to biotic dispersal, and that orchids may be more geographically constrained by intrinsic factors, such as fungal symbionts and pollinator mutualists, which differ among elevational zones (Arroyo et al ., , ; Lugo et al ., ) than by distance.…”

“…Analyses of phylogenetic incongruence detection identified 259 and 125 potential conflicting tips in Cymbidieae and Pleurothallidinae, respectively (Figs S3, S4), all of which clustered in weakly to moderately supported clades (< 75% bootstrap support, BS) or in clades with extremely long branches. These analyses indicated the absence of supported phylogenetic incongruence (Mason-Gamer & Kellog, 1996;P erez-Escobar et al, 2016b). In the absence of supported phylogenetic conflicts, nuclear and plastid partitions of Cymbidieae and Pleurothallidinae were concatenated.…”

“…Poorly aligned positions were excluded from the alignments using GBLOCKS v.0.9 (Talavera & Castresana, 2007). To statistically detect potential incongruences between plastid and nuclear DNA phylogenies, we used the tool PROCRUSTES APPROACH TO COPHYLOGENY (PACo; http://www.uv.es/cophylpaco/) (Balbuena et al, 2013;P erez-Escobar et al, 2016b). Maximum likelihood (ML) tree inference was performed using RAXML-HPC v.8.0 (Stamatakis, 2014), under the GTR + G substitution model with four gamma categories (best model for both datasets as inferred via the Akaike information criterion (AIC) in JMODELTEST v.2.1.6; Darriba et al, 2012), with 1000 bootstrap replicates and data partitioning by genome compartment.…”

From tree tops to the ground: Reversals to terrestrial habit in Galeandra orchids (Epidendroideae: Catasetinae)

“…Miocene origin of Galeandra in Amazonia Galeandra arose towards the Late Miocene, about 10 Ma, close to the climatic optimum when several plant clades in the Neotropical Region originated (Antonelli et al, 2009;Gustafsson et al, 2010;Hoorn et al, 2010;Pérez-Escobar et al, 2017c). At that time, the Guiana and the Brazilian Shields became large islands.…”