Unidirectional transitions in nectar gain and loss suggest food deception is a stable evolutionary strategy in Epidendrum (Orchidaceae): insights from anatomical and molecular evidence

Abstract

BackgroundNectar gain and loss are important flower transitions observed in angiosperms, and are particularly common in orchids. To understand such transitions, the availability of detailed anatomical data and species-level phylogenies are crucial. We investigated the evolution of food deception in Epidendrum, one of the largest orchid genera, using genus phylogeny to map transitions between nectar gain and loss among different clades. Associations between anatomical and histochemical changes and nectar gain and loss were examined using fresh material available from 27 species. The evolution of nectar presence/absence in Epidendrum species was investigated in a phylogenetic framework of 47 species, using one nuclear and five plastid DNA regions available from GenBank and sequenced in this study.ResultsThe presence or absence of nectar was strongly associated with changes in the inner epidermal tissues of nectaries. Nectar-secreting species have unornamented epidermal tissue, in contrast to the unicellular trichomes found on the epidermis of food deceptive species. Bayesian tests confirmed that transitions occurred preferentially from nectar presence to nectar absence across the Epidendrum phylogeny. In addition, independent nectar loss events were found across the phylogeny, suggesting a lack of constraint for these transitions.ConclusionsOrnamented nectaries may play an important role in the deceptive pollination strategy by secreting volatile organic compounds and providing tactile stimuli to pollinators. The recurrent and apparently irreversible pattern of nectar loss in Epidendrum suggests that food deception may constitute an alternative evolutionarily stable strategy, as observed in other orchid groups.Electronic supplementary materialThe online version of this article (10.1186/s12870-018-1398-y) contains supplementary material, which is available to authorized users.

A Review of Current Knowledge of Zamiaceae, With Emphasis on Zamia From South America

“…Recently, the number of phylogenetic analyses with Zamiaceae has increased (Gutie´rrez-Ortega, Kajita, & Molina-Freaner, 2014;Gutie´rrez-Ortega, Jimenez-Cedillo, et al, 2018a;Gutie´rrez-Ortega, Yamamoto, et al, 2018b), offering an unprecedented amount of molecular data. Such phylogenetic inferences will deepen our understanding about the evolution of niche conservatism, morphological traits associated with specific reproductive strategies, and speciation rates, as observed in other plant groups (Cardoso-Gustavson et al, 2018;Vasconcelos et al, 2019). Since cycads represent an old lineage of seed plants, new evidence on diversification mechanisms obtained by using multiple approaches would provide a solid framework for the comprehension of plant evolution and speciation pathways and also contribute to the conservation of this Note.…”

Hybridization and geographic distribution shapes the spatial genetic structure of two co-occurring orchid species

“…The two species are clearly distinguishable based on phylogenetic, morphometric, and cytogenetic data (Pessoa et al 2012). According to the most recent phylogenetic analysis of Epidendrum (Cardoso-Gustavson et al 2018), E. fulgens and E. puniceoluteum are closely related but not sister species, belonging to the Atlantic Clade within subgenus Amphyglottium. Both species are self-compatible and pollinated by several butterfly species.…”

“…Both species are self-compatible and pollinated by several butterfly species. Due to the absence of nectar reward in flowers from both species (Cardoso-Gustavson et al 2018), pollinators potentially avoid plants in the same patch, decreasing the levels of inbreeding and genetic differentiation among populations (Pinheiro et al 2010(Pinheiro et al , 2011. Hybrids between these two species (Supplementary Fig.…”

Differential gene expression reveals mechanisms related to habitat divergence between hybridizing orchids from the Neotropical coastal plains

“…1 ), i.e., depressions between successive beach ridges that are seasonally flooded (see [ 59 ]). Both species are pollinated by butterflies and produce no nectar, following a model of pollination by deceit that favor interspecific gene flow [ 28 , 29 , 60 ]. In sympatric areas, these species share pollinators and have overlapping flowering phenologies [ 29 ].…”

“…However, model systems are mostly from temperate regions of the northern hemisphere, limiting our understanding about the role of ecology on the process of adaptation and evolution of biodiversity in the tropics [ 27 ]. In our study, we investigate the genetic basis of adaptation in two closely related Neotropical orchids [ 28 ], the diploid Epidendrum fulgens and tetraploid E. puniceoluteum , which hybridize in the Atlantic coastal plains in southeast Brazil, a narrow vegetation physiognomy known as restingas [ 29 , 30 ]. These species are associated with contrasting adjacent habitats; whereas E. fulgens predominantly occurs in sand dunes, E. puniceoulutem is found in swampy areas further inland (Fig.…”