Why are deceptive orchids so phenotypically variable?
Giovanni Scopece1
1Department of Biology, University of Naples Federico II. giovanni.scopece@unina.it
An unusually high intraspecific continuous or discrete floral trait variability has been described within deceptive orchids, as opposed to rewarding ones. The reasons that can explain this pattern stimulated a long-standing debate. An appealing hypothesis is that phenotypically variable deceptive species would have a reproductive success advantage compared to those with a constant floral display because floral trait variability would decrease pollinator avoidance learning in dealing with nectarless flowers, hence increasing their visitation rate. Nonetheless, a review of the studies attempting to demonstrate this hypothesis showed non-significant results thus suggesting that the high phenotypic variability is not likely to enhance deceptive orchids’ reproductive success but is more likely to be a consequence of relaxed selection by pollinators. Contrary to this idea, however, in recent years, several studies report on widespread directional selection mediated by pollinators in these deceptive orchids contrasting the idea of relaxed selection. The reasons that lay at the basis of the elevated pheotypic polymorphism of deceptive orchids are thus still to be completely discovered, however, a recent study showed significant differences in selection differentials across years in deceptive orchids suggesting that fluctuating selection can also contribute to the maintenance of phenotypic variation.
Key words: fluctuating selection, food-deceptive orchids, phenotypic polymorphism, pollinator behaviour, reproductive success.
Funded by: This research was carried out in the frame of Programme STAR, financially supported by UniNA and Compagnia di San Paolo.
Macro- and microevolutionary drivers of allopolyploid evolution in Dactylorhiza (Orchidaceae)
Marie K. Brandrud1, Thomas Wolfe1, Francisco Balao2, Mikael Hedrén3, Mark W. Chase4 & Ovidiu Paun1
1Plant Ecological Genomics, University of Vienna, Austria; 2University of Seville, Sevilla, Spain;
3Lund University, Sweden; 4Royal Botanic Gardens, Kew, UK. m.chase@kew.org
Early-generation allopolyploids need to quickly accommodate divergent genomes into one nucleus with ecological consequences. Dactylorhiza, with its diverse array of often ecologically distinct polyploids, constitutes an excellent system to investigate allopolyploid evolution. With RADseq data we document the origins of more than ten independently formed Dactylorhiza allopolyploids.
We bring examples of frequent gene flow in contact zones between related polyploids of different ages. This process enriches the genetic pool of these populations, but the patterns observed point to some genomic regions resilient to admixture. We further exemplify with RNAseq the molecular basis of ecological divergence between two of these independent, sibling allopolyploids, D. majalis and D. traunsteineri. Significant expression differences between these allopolyploids affect several ecologically relevant genes. For example, genes in the photosynthesis metabolic pathway have been significantly upregulated in D. traunsteineri, which is adapted to northern environments. Finally, we conclude that the major transcriptomic divergence observed among the diploid parents became reconciled in different ways in the sibling Dactylorhiza polyploids, as a result of an interplay between stochastic genomic alterations and distinct selection pressures specific to their respective environments.
Key words: allopolyploidy, ecological differentiation, Orchidoideae, tetraploids, transcriptomic divergence.
Research in support of orchid conservation and reintroduction Michael F. Fay1, Roberta Gargiulo1 & Hassan Rankou1
1Royal Botanic Gardens, Kew, Richmond, TW9 3AB, UK. m.fay@kew.org
With > 28,000 species, orchids are one of the largest families of angiosperms, and they are also one of the most threatened, in part due to their complex life history strategies. Threats include climate change and habitat destruction, and many orchids are also threatened by harvest for horticulture, food or medicine. In addition to being unsustainable, this trade is often illegal and/or undocumented. In this talk, I will provide examples of some current projects to illustrate approaches to orchid conservation. Focused approaches for the species at the highest risk will continue to be applied on a species-by-species basis, but the level of some of these threats now outstrips our abilities to combat them at a species level for all species in orchids (and other large groups). If we are to conserve orchids for the future, we will need to use approaches allowing us to address the threats for groups of species to complement the more focused methods.
Key words: conservation, illegal trade, Orchidaceae, reintroduction, threats.
Ecology of floral perfumes in the Neotropical orchid genus Catasetum: does chemical composition predict pollinating orchid bee genera?
Paulo Milet Pinheiro1, Manfred Ayasse2, Daniela Maria do Amaral Ferraz Navarro3, Isabel Cristina Sobreira Machado1, Stefan Dötterl4 & Günter Gerlach5
1Department of Botany - Federal University of Pernambuco; 2Institute of Evolutionary Ecology and Conservation Genomics - University of Ulm; 3Department of Chemistry - Federal University of Pernambuco; 4Institute of Ecology, Biodiversity and Evolution of Plants - University Salzburg;
5Botanical Garden of Munich. miletpinheiro@hotmail.com
The orchid genus Catasetum comprises about 170 fragrance-producing species pollinated by male euglossine bees, mainly of the genera Euglossa and Eulaema. Interestingly, species pollinated by Eulaema are rarely visited by Euglossa, and vice versa, and floral perfumes are assumed to be involved in this selective attraction. Recent data suggests that the evolution of floral perfumes in Catasetum is shaped by pre-existing sensory/behaviour biases of pollinators, however, experimental support is scarce. Here we tested whether scent traits (composition and daily fluctuation) differ between species pollinated by Eulaema and Euglossa. Comparative and multivariate analyses of chemical composition showed that floral perfumes of species pollinated by Eulaema and Euglossa differ significantly from each other. With respect to daily fluctuation in scent emission, we found that the peak of emission in species pollinated by Eulaema and Euglossa occur between 06:00h and 09:00h and between 09:00h and 12:00h, respectively. This pattern matches with the peak of foraging activity of Eulaema and Euglossa species in nature. We conclude that scent traits in Catasetum predict the genus of their pollinating bees, suggesting that the plants adapt to pre-existing sensory/behaviour biases of one of the euglossine genera.
Key words: euglossine bees, floral perfumes, Neotropics, Orchidaceae, pollination.
Funded by: CAPES, CNPq, FACEPE, DFG
The role of polyploidy and apomixis in diversification of Zygopetalum mackayi orchids Samantha Koehler1, Gleicyanne V. da Costa1, Juliana L. Mayer1, Lyderson F. Viccini2, Shaiany S.
L. Gomes2, Thiago V. S. Campacci1 & Yohans A. Moura1
1Universidade Estadual de Campinas; 2Universidade Federal de Juiz de Fora. samk@unicamp.br
High elevation rocky complexes (HERCs) from eastern Brazil harbour a highly endemic and threatened flora. Yet, we know little about how polyploidy and apomixis affected diversification in HERCs. We gathered data on the reproductive biology, cytogeography, embryogenesis, and genetic diversity of the orchid Zygopetalum mackayi, a typical species from HERCs. Z. mackayi is a generalized food-deceptive species pollinated by large bees. It is also dependent on pollinators for reproduction. We identified three cytotypes. Cytotypes 8x and 16x are geographically structured and strongly associated with temperature seasonality and annual precipitation. The intermediate cytotype 12x is restricted to a secondary contact zone among 8x and 16x cytotypes. All cytotypes have meiotic irregularities, but they are more frequent in the intermediate cytotype. Facultative sporophytic apomixis is restricted to neopolyploids (12x and 16x). Paleopolyploids (8x) reproduce only sexually. Genetic variation within and among populations and cytotypes suggests apomixis is not important for the persistence of neopolyploids. Cytotype 12x likely acts as a triplod block. De novo production via crossing between 8x and 16x cytotypes is probably the primary means of 12x production. Studies are underway to evaluate how resistance to water stress and mycorrhizal associations is related to cytotype occurrence.
Key words: adventitious embryony, asexual reproduction, campos de altitude, campos rupestres, whole genome duplication.
Funded by: Coordenação de Aperfeiçoamento de Pessoal de Nível Superior; Fundação de Amparo a Pesquisa do Estado de São Paulo 2014/04426-5; Fundação de Amparo à Pesquisa do Estado de
Minas Gerais (APQ-02096-14/PPM 00478-16); Fundação de Apoio ao Ensino, Pesquisa e Extensão (PRP/Unicamp)
How do chromosomes correlate with orchid distribution?
Thaissa Engel1, Juliano S. Cabral2, Alexandre Zuntini1, Eliana Forni-Martins1, Ana Paula Moraes3
1Department of Plant Biology, Campinas State University, Campinas, São Paulo, 13083-862, Brazil; 2Ecosystem Modeling, Center for Computation and Theoretical Biology, University of Würzburg, Würzburg, 97074, Germany; 3Center of Natural and Human Science, Federal University of ABC, São Bernardo do Campo, 09606-070, Brazil. ana.moraes@ufabc.edu.br
It is a central concept in niche ecology that species distributions are primarily determined by ecological and abiotic criteria. However, genomic constraints, like the amount of DNA (genome size - GS) and chromosome organization (chromosome number - 2n) have been poorly investigated in an integrative approach that considers evolutive history and species ecological characteristics. To understand how these factors interact and how they influence plant geographical distribution, we focused on a large group of orchid which presents a wide geographic distribution and a large morphological, GS and 2n variation. Here we could detect that even with low frequency, the polyploids seem to have great influence in the number of different habitats colonized by species and in the occurrence of the exclusive epiphyte habitat (increase in 2n was negatively related with an increasein the number of habitat types and exclusive epiphyte habitat). The same was observed for GS variation: species presenting exclusively epiphytic habitat presented smaller genomes than non-epiphytic species or, at least, not exclusively. We can conclude that 2n and GS influence plant ecology and that the species geographic distribution is a product of the interaction between its GS and some abiotic characteristics.
Key words: ecology, genome size, Maxillariinae, phylogeny, polyploidy.