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Conservatoire et Jardin botaniques de la Ville de Genève
Systematics and evolution of neotropical Gesneriaceae
The main goal of our research is to inventory and classify the taxons pertaining to the Gesneriaceae family in order to understand the origin of their diversity, focusing our interest on the neotropical lineages that belong to the subfamily Gesnerioideae. This monophyletic group includes some 1050 species that occur in different biomes of tropical America (i.e. Brazilian Atlantic Forest, Andes, Amazonia). These species display an astonishing diversity in morphology and ecology, as in the case of adaptations to pollination by hummingbirds, bats, bees or habitats that can be epiphytic, saxicolous or terrestrial. Our research follows three main axes: - Inventories and Floras Geographic distribution, morphology and ecological data are compiled from field trips, herbaria studies, mainly in Brazil. These data allow the production of check-lists, red-lists or floristic treatments at local, regional, country or continent levels. During this process, new species are recognized, leading to their formal description and publication. - Systematics The phylogenetic relationships between species are investigated through DNA sequences analysis, from nuclear and plastidic genomes. These analyses were focused on different neotropical lineages, i.e. Sinningieae (85 spp.), Gloxinieae (167 spp.), Sphaerorrhizeae (4 spp.), Episcieae (477 spp.). Results of these analyses allow us to propose new classifications for these groups and to understand the evolution of selected morphological characters. - Origin and radiation processes The history and the radiation processes of Gesneriaceae are studied by combining phylogenetical results with species distribution and ecology data. We focused on Brazilian clades for which we rely on an exhaustive sampling along with many data on the species biology like the tribe Sinningieae or the genera Codonanthe/Nematanthus. For these groups we infer the biogeographic history of the lineages and evaluate the importance of geographical and ecological factors within the radiation processes, as well as the role of plants-pollinators relationships vs. floral diversification. In addition, the molecular bases for evolutionary transitions in some phenotypes like the flower color are also investigated.
The tribe Sinningieae comprises some 85 species mostly occurring in the Brazilian Atlantic Forest Biome; a few taxa are found in other biomes in Brazil or elsewhere in Tropical America. The monograph will deal with an exhaustive treatment of the taxa, including identifications keys, full descriptions, distribution maps, illustrations and discussions about ecological and morphological aspects. The data are mainly obtained from investigations in European and North or South American herbaria, along with material and information provided by a network of numerous scientists and plant growers established since the early 1980’s. Field trips are regularly done in order to obtain missing or incomplete data. Besides herbarium sheets, fertile part are fixed in alcohol, leaf tissues are desiccated for future DNA analyses. Cuttings or other vegetative parts are gathered in order to introduce them in cultivation in Brazil (long term collaboration with Mauro Peixoto in São Paulo) or in the Geneva Conservatoire et Jardin Botaniques greenhouses, in accordance with national and international rules and legal procedures.
This project put together geographic, morphological and ecological data obtained in the field and during herbaria investigations. Results are organized for treatments in various ongoing Brazilian state or local floras. In this process, new species are recognized and formal publication is done, often in collaboration with Brazilian students at bachelor, master, PhD or post-doc levels.
This project aims to produce a systematic revision of the tribe Sinningieae (85 spp. mainly in Brazil), which includes the genera Sinningia, Paliavana, et Vanhouttea. Previous phylogenetic analyses have shown that Paliavana et Vanhouttea are not monophyletic and embedded within Sinningia (Perret et al. 2003). In order to get a better resolution of the relationships within Sinningieae, two additional molecular markers (ITS et rps16) will be added to the existing data and a morphological matrix will be produced. The six newly described species of Sinningia will be included in these analyses. Our goal is to get a robust phylogenetic tree for the group that will serve as a basis to redefine the generic boundaries in the tribe and to better understand its striking diversification. PERRET, M., A. CHAUTEMS, R. SPICHIGER, G. KITE, AND V. SAVOLAINEN. 2003. Systematics and evolution of tribe Sinningieae (Gesneriaceae): evidence from phylogenetic analyses of six plastid DNA regions and nuclear ncpGS. American Journal of Botany 90: 445-460.
Systematics of the tribe Gloxinieae s.l. has been extensively revised on the basis of recent molecular and morphological studies (Roalson et al 2005a, 2005b). These works have shown the non-monophyly of several genera (e.g., Gloxinia) and the segregated position of Gloxinia sarmentiana, now included in the new tribe Sphaerorrhizeae. In collaboration with Dr. Andrea O. Araujo, we proposed to continue these efforts through a detailed analysis of the Brazilian taxa (21 species; Araujo 2007). A phylogenetic analysis of these species will performed using several molecular markers (matK, trnL-trnF, rps16, rpl16, atpB-rbcL ncpGS, ITS). Results of this analysis will be used to better define generic and species boundaries for these Brazilian taxa and their relationships within the Neotropical Gesneriaceae.
This project aims to produce a systematic revision of the genera Codonanthe (18 spp.) and Nematanthus (32 spp.) that belong to the tribe Episcieae (Gesneriaceae). The genus Nematanthus is endemic to the Brazilian Atlantic forest, whereas the Codonanthe also occur at low altitude in northern South America and Central America. Species of these genera are all epiphytic plants displaying either hummingbird flowers (in Nematanthus) or bee flowers (in Codonanthe). Preliminary results suggest that these two genera belong to a single clade and that Codonanthe is likely paraphyletic. To verify these hypothesis, we will further evaluate phylogenetic relationships within this groups based on a three molecular markers (trnL-trnF, rps16 et ITS) and an exhaustive species sampling. This phylogenetic framework will be used as a basis for a new generic arrangement in the group and to better understand the evolution of certain floral traits such as pollination syndrome and resupination.
Understanding the origin and causes of diversification is a major challenge in biology. Recent phylogenetic methods allowing to test the association between shift in diversification rates and a particular evolutionary event have opened new perspective towards the understanding of the factors that trigger radiations. In plants, the researches have focused primarily on potential « key traits » mainly linked to floral morphology and dispersal mode, whereas more recent study stress the importance of dispersal events in new geographic areas. Beyond the identification of lineage attributes, evolution of geographical distributions and ecological differentiation within clades may also influence diversification rates through their effect on speciation and species coexistence. These correlates of plant radiations and their impact on diversification are the focus of this proposal.
The main goal of this project is to understand the processes that contribute to the origin and maintenance of biodiversity in the sub-family Gesnerioideae, a monophyletic group of 1050 species endemic to the Neotropics. This study group may be particularly appropriate to study the evolution of plant diversity in the Neotropics since its radiation took place in various biomes of tropical America and was accompanied by extensive ecological and phenotypic diversification. To achieve this goal, we will assemble available DNA sequences and complement molecular and taxonomic sampling in selected groups to produce a global phylogenetic tree for the Gesnerioideae with a complete species sampling in several lineages. Plant tissue for additional sequencing will be collected during two field trips in Brazil and Peru, and by visiting various herbaria and living collections. Based on this historical framework, we will reconstruct the evolution of geographical distribution and morphological innovations (e.g., hummingbird pollination, epiphytism, fleshy fruit) and evaluate their impact on diversification rates. To explore the relative role of geographic and ecologic factors in promoting speciation and species maintenance in the different Gesnerioideae lineages, we will collect detailed information on species distribution, local environmental conditions and climatic tolerance in targeted clades. These data will be used to evaluate the importance of geographical isolation and ecological shifts in speciation by comparing sister species and to characterize how geographical and ecological space is occupied during radiation by inferring the evolution of niche characteristics. Results from this project may contribute to identify general patterns in the relationships between species diversification, species distribution and the evolution of ecological disparity within plant radiations in the Neotropics.