DOI: 10.5061/dryad.35935
title: Data from: Multiple independent origins of auto-pollination in tropical orchids (Bulbophyllum) in light of the hypothesis of selfing as an evolutionary dead end

description: Background: The transition from outcrossing to selfing has long been
 portrayed as an ‘evolutionary dead end’ because, first, reversals are
 unlikely and, second, selfing lineages suffer from higher rates of
 extinction owing to a reduced potential for adaptation and the
 accumulation of deleterious mutations. We tested these two predictions in
 a clade of Madagascan Bulbophyllum orchids (30 spp.), including eight
 species where auto-pollinating morphs (i.e., selfers, without a
 ‘rostellum’) co-exist with their pollinator-dependent conspecifics (i.e.,
 outcrossers, possessing a rostellum). Specifically, we addressed this
 issue on the basis of a time-calibrated phylogeny by means of ancestral
 character reconstructions and within the state-dependent evolution
 framework of BiSSE (Binary State Speciation and Extinction), which allowed
 jointly estimating rates of transition, speciation, and extinction between
 outcrossing and selfing. Results: The eight species capable of selfing
 occurred in scattered positions across the phylogeny, with two likely
 originating in the Pliocene (ca. 4.4–3.1 Ma), one in the Early Pleistocene
 (ca. 2.4 Ma), and five since the mid-Pleistocene (ca. = 1.3 Ma). We infer
 that this scattered phylogenetic distribution of selfing is best described
 by models including up to eight independent outcrossing-to-selfing
 transitions and very low rates of speciation (and either moderate or zero
 rates of extinction) associated with selfing. Conclusions: The frequent
 and irreversible outcrossing-to-selfing transitions in Madagascan
 Bulbophyllum are clearly congruent with the first prediction of the dead
 end hypothesis. The inability of our study to conclusively reject or
 support the likewise predicted higher extinction rate in selfing lineages
 might be explained by a combination of methodological limitations (low
 statistical power of our BiSSE approach to reliably estimate extinction in
 small-sized trees) and evolutionary processes (insufficient time elapsed
 for selfers to go extinct). We suggest that, in these tropical orchids, a
 simple genetic basis of selfing (via loss of the ‘rostellum’) is needed to
 explain the strikingly recurrent transitions to selfing, perhaps
 reflecting rapid response to parallel and novel selective environments
 over Late Quaternary (= 1.3 Ma) time scales.
description: Majority-rule consensus
 phylogenetic tree Bulbophyllum clade C (Figure 2)Majority-rule consensus
 of Madagascan Bulbophyllum clade C (sects. Calamaria, Humblotiorchis,
 Bifalcula) estimated under Bayesian Inference (MRBAYES version
 3.1.2)Majority-rule consensus tree
 Bulbophyllum clade C (Figure
 2).nex5,000 post-burn-in trees
 of the BI analysis (Figure 3A)Last 5,000 post-burn-in
 trees of the BI analysis used for ancestral character reconstruction (in
 BAYESTRAITS version 1.0)5,000 post-burn-in trees of the
 BI analysis.nex1,000 dated BEAST trees
 (Figure 3,4; Table 3,4)1,000 secondarily
 calibrated BEAST (version 1.6.1 ) trees resampled at a lower frequency
 (LOGCOMBINER version 1.6.1). Used for ancestral character reconstruction
 (Figure 3B), LTT plot (Figure 3), diversifcation analyses (Figure
 4,Tab.3,Tab.4) using R packages APE and DIVERSITREE.1,000 dated BEAST
 trees.nexChronogram of Madagascan
 Bulbophyllum clade C (Figure 3C)Secondarily calibrated
 BEAST version 1.6.1 chronogram of Madagascan Bulbophyllum clade
 C.Chronogram of Madagascan
 Bulbophyllum clade C.nex