Orchid historical biogeography, diversification, Antarctica and the paradox of orchid dispersal

Abstract

AimOrchidaceae is the most species-rich angiosperm family and has one of the broadest distributions. Until now, the lack of a well-resolved phylogeny has prevented analyses of orchid historical biogeography. In this study, we use such a phylogeny to estimate the geographical spread of orchids, evaluate the importance of different regions in their diversification and assess the role of long-distance dispersal (LDD) in generating orchid diversity. LocationGlobal. MethodsAnalyses use a phylogeny including species representing all five orchid subfamilies and almost all tribes and subtribes, calibrated against 17 angiosperm fossils. We estimated historical biogeography and assessed the importance of different regions for rates of speciation, extinction and net species diversification. We evaluated the impact of particular LDD events on orchid diversity by asking how many species evolved in the new range subsequent to those events. ResultsOrchids appear to have arisen in Australia 112Ma (95% higher probability distribution: 102.0-120.0Ma), then spread to the Neotropics via Antarctica by 90Ma (HPD: 79.7-99.5Ma), when all three continents were in close contact and apostasioids split from the ancestor of all other orchids. Ancestors of vanilloids, cypripedioids and orchidoids+epidendroids appear to have originated in the Neotropics 84-64Ma. Repeated long- and short-distance dispersal occurred through orchid history: stochastic mapping identified a mean total of 74 LDD events or 0.8Ma(-1). Across orchid history, Southeast Asia was the most important source and maximally accelerated net diversification; across epidendroids, the Neotropics maximally accelerated diversification. Main conclusionsOur analysis provides the first biogeographical history of the orchids, implicating Australia, the Neotropics and Antarctica in their origin. LDD and life in the Neotropics - especially the Andes - had profound effects on their spread and diversification; >97% of all orchid species are restricted to individual continents

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

“…The absolute ages obtained for Cymbidieae and Pleurothallidinae chronograms are also in agreement with previously published dated phylogenies (e.g. Ramírez et al ., ; Chomicki et al ., ; Givnish et al ., ). Divergence time estimates and 95% CIs inferred for all nodes of Cymbidieae and Pleurothallidinae chronograms are shown in Figs S8 and S9.…”

Conceptual and statistical problems with the DEC+J model of founder‐event speciation and its comparison with DEC via model selection

“…A few examples (of many) are Cantalapiedra, Prado, Hernández Fernández, and Alberdi (), Brown et al (), Givnish et al. (), Skeels and Cardillo () and Kok et al. ().…”

Similarity in mycorrhizal communities associating with two widespread terrestrial orchids decays with distance

“…Although mycorrhizal dependency has been increasingly recognized as an important factor influencing both the distribution and abundance of orchid populations (McCormick & Jacquemyn, ; McCormick, Whigham, & Canchani‐Viruet, ), at present little is known about the geographical distribution of orchid mycorrhizal fungi (OMF; reviewed in Jacquemyn, Duffy, et al, ). However, the widespread occurrence of orchids across the globe and in diverse ecosystems (Givnish et al, ) suggests that the OMF that are necessary for germination and seedling establishment are also widespread and not necessarily restricted to geographical regions. A major caveat in our current understanding of the biogeographical distribution of OMF is that most of the available data are very fragmentary and that often only a few populations are sampled within a restricted geographical area, making it difficult to draw any general conclusions about the distribution of fungi associated with orchids across larger scales (Jacquemyn, Duffy, et al, ).…”