Délimitation taxonomique et étude de la biologie de la reproduction du genre africain Cyrtorchis Schltr. (Orchidaceae)

The genus Cyrtorchis, grouped of 18 angraecoid orchids species endemic to tropical Africa, and was known for its large, white, fragrant flowers with a long spur well suited for studies on reproductive biology. It was also known for its taxonomic delimitation problems, which can be detrimental to the conservation of the species.This PhD thesis aims to address the delimitation problems within the genus at the inter- and intraspecific level using an integrative taxonomic approach and to investigate its reproductive biology.Visual inspection of 1752 specimens, morphometric and phylogenetic analyses was used to clarify the taxonomy within the genus. Visual inspection delineated 27 a priori morphogroups, from which a sample of 171 specimens representing 20 morphogroups was used for morphometric analyses. For phylogenetic reconstructions, 69 specimens representing 21 of the 27 morphogroups were sequenced with six molecular markers. The characterization of flowering patterns and the observation of pollinators were carried out respectively through a three-year shadehouse phenological survey of 494 living specimens representing 15 taxa and a survey of the natural in situ pollination of two taxa in Cameroon. The assessment of factors affecting fruit and viable seed production was carried out in two species of the genus through 448 hand pollination tests for which the effect of pollination system and resource limitation were examined.Morphological approaches allow to distinguish two groups corresponding to the two sections previously identified for the genus Cyrtorchis. Molecular analyses support only the monophyly of on of the sections, Cyrtorchis sect. Cyrtorchis. Eight morphologically defined taxa including three new species are also well supported by morphometric and phylogenetic analyses. The insertion point of the stipites at the rear third of the length of the viscidium appears to be one of the main reproductive characters supporting the monophyly of the genus while other traits (such as the viscidium structure, the shape of the stipites and the lateral lobes of the rostellum) are found to be important criteria for inferring phylogenetic relationships within the genus. Finally this analysis highlights 27 taxa within the genus (including six new taxa to be described), of which 12 taxa, confirmed by morphometric and/or phylogenetic approaches. Flowering of most species at the shadehouse is peaking during the main rainy season (between August and October). However, some sympatric species present non-overlapping flowering periods and an asynchronism of flowering between populations of the same species. Natural pollination is a rare event and difficult to observe in the two studied species. Indeed, the overall pollination/fruiting rate is low (39% of flowers with pollinia removed and 16% of fruits produced in C. okuensis; 31-15% of flowers with pollinia removed and 7-4% of fruits produced in C. letouzeyi) because of the reduced number of pollinators visits. Additionally, both species were found to be pollinated by hawkmoths. Manual pollination tests revealed that cross-pollination appears to be the most efficient pollination system to produce fruits and viable seeds. However, more species will need to be tested to confirm this pattern.The multidisciplinary approaches developed in this work provide a solid basis to define and implement effective conservation strategies for threatened orchid species. To produce a complete taxonomic revision of the genus, a completed phylogeny including the five remaining and the yet unresolved taxa is required. The newly identified taxa should be described and the conservation status assessed for all species recognised in the genus.Le genre Cyrtorchis, groupait 18 espèces d’orchidées angraecoïdes endémiques d'Afrique tropicale, était connu pour ses grandes fleurs blanches, odorantes à long éperon bien adaptées pour des études sur la biologie de la reproduction. Il était également connu pour ses problèmes de délimitation taxonomique qui peuvent s’avérer préjudiciables pour la conservation des espèces.La présente thèse de doctorat ambitionne de résoudre les problèmes de délimitation au sein du genre au niveau inter et intraspécifique en utilisant une approche de taxonomie intégrative et de documenter sa biologie de la reproduction.Une inspection visuelle de 1752 spécimens, les analyses morphométriques et phylogénétiques ont été utilisées pour clarifier la taxonomie au sein du genre. L’inspection visuelle a permis de délimiter 27 morphogroupes à priori, desquels un échantillonnage de 171 spécimens représentant 20 morphogroupes a été utilisé pour les analyses morphométriques. Pour les reconstructions phylogénétiques, 69 spécimens représentant 21 des 27 morphogroupes ont été séquencés à partir de six marqueurs moléculaires. La caractérisation des patrons de floraison et l’observation et des pollinisateurs ont été réalisées au Cameroun grâce à un suivi phénologique en ombrière sur trois ans de 494 spécimens vivants représentant 15 taxons, et un suivi de la pollinisation naturelle in situ de deux de ces taxons. L’évaluation des facteurs affectant la production des fruits et des graines viables a été réalisée chez deux espèces du genre à travers 448 tests de pollinisation manuelle pour lesquels l’effet du système de pollinisation et de la limitation des ressources ont été examinés.Les approches morphologiques permettent de distinguer deux groupes correspondant aux deux sections préalablement identifiées pour le genre Cyrtorchis. Les analyses moléculaires quant à elles ne soutiennent que la monophylie d’une des deux sections, Cyrtorchis sect. Cyrtorchis. Huit taxons morphologiquement définis dans le genre incluant trois nouvelles espèces sont également bien supportés par les analyses morphométriques et phylogénétiques. Le point d’insertion des stipites au tier supérieur du viscidium semble être l’un des principaux caractères reproducteurs soutenant la monophylie du genre alors que d’autres traits (tels que la structure du viscidium, la forme des stipites et des lobes latéraux du rostelle) se révèlent être d’importants critères permettant d’inférer des relations phylogénétiques au sein du genre. Au final, cette analyse met en évidence 27 taxons au sein du genre(incluant six nouveaux taxons à décrire), dont 12 taxons, confirmé par les approches morphométriques et/ou phylogénétiques. La phénologie de la floraison des espèces en ombrière montre un pic de floraisons à la grande saison de pluie (entre août et octobre). Un décalage de la floraison est observé chez certains taxons distribués en sympatrie et un asynchronisme de la floraison entre population de la même espèce. La pollinisation naturelle est un évènement rare et difficile à observer chez les deux espèces étudiées (C. letouzeyi et C. okuensis). En effet, le taux de pollinisation/fructification est globalement faible (39 % de fleurs avec les pollinies emportées et 16 % de fruits produits chez C. okuensis ; 31-15 % de fleurs avec les pollinies emportées et 7-4 % de fruits produits chez C. letouzeyi), et ce, à cause du nombre réduit des visites des pollinisateurs. Par ailleurs, les pollinisateurs des deux espèces ont été identifiés et la pollinisation par les sphinx est confirmée dans le genre. Les tests de pollinisation manuelles ont révélé que la pollinisation croisée semble être le système de pollinisation le plus efficace pour la production de fruits et de graines viables. Cependant, davantage d’espèces devront être testées pour confirmer ce patron.Les approches multidisciplinaires développées dans ce travail sont des bases solides pour la définition et la mise en oeuvre de stratégies efficaces de conservation pour les espèces d’orchidées menacées. Afin de produire une révision taxonomique complète du genre, une phylogénie complète incluant les cinq taxons restants et ceux encore non résolus est nécessaire. Les nouveaux taxons identifiés devraient être décrits et les statuts de conservation évalués pour l’ensemble des espèces reconnues dans le genr

Synoptic revision of the genus Cyrtorchis Schltr. (Angraecinae, Orchidaceae) in Central Africa, with the description of a new species restricted to submontane vegetation

International audienceAs a preliminary step to the taxonomic revision of the genus Cyrtorchis, a synoptic revision of the species occurring in Central Africa was undertaken. Based on a detailed examination of 1,039 herbarium specimens, including nomenclatural types, we have recognized 14 species in Central Africa (one of which is divided into two subspecies), including one new species that the study brought to light, described here as Cyrtorchis submontana. The new species closely resembles C. guillaumetii and C. brownii in general aspect, but differs from them in having thinner, small elliptic leaves and shorter, fewer-flowered, more lax inflorescences with shorter bracts. The species is restricted to submontane vegetation of Central Africa and is assessed as Endangered following the IUCN Red List Categories and Criteria. Cyrtorchis latibracteata and C. subcylindrifolia are lectotypified, and the latter is placed as a synonym under C. henriquesiana. Many new records are reported, and for each taxon the distribution, habitat and ecology are given. An identification key for the Central African taxa is also provide

Taxonomic description and pollination ecology of Cyrtorchis okuensis (Orchidaceae, Angraecinae), a new species endemic to the Cameroon Volcanic Line

International audienceBackground and aims-A recent taxonomic and molecular study of the genus Cyrtorchis revealed three new species. Here, we describe one of these new species, endemic to the Cameroon Volcanic Line (CVL), and compare it to its closest relatives. Its conservation status is provided along with detailed information on its ecology and reproductive biology. Material and methods-A detailed examination of 21 herbarium specimens was performed using standard practices of herbarium taxonomy. The conservation status of the new species was assessed using the IUCN Red List Categories and Criteria. Furthermore, we investigated the reproductive biology of the new species in an easily accessible subpopulation in Cameroon and tested the hypothesis of hawkmoth pollination in the genus Cyrtorchis. Key results-The newly discovered species, here named C. okuensis, is restricted to the montane forest (1600 to 2500 m elevation) of the CVL and is currently assessed as Near Threatened (NT). Among angraecoid orchids in which hawkmoth pollination is recorded (~16 species), C. okuensis has the shortest nectar spur (19-40 mm). In situ observations revealed hawkmoths with short proboscis of the genus Hippotion (H. celerio, H. eson, and H. osiris) as the main pollinators. The rate of pollination and fruiting under natural conditions was low and among the 448 surveyed flowers only 38.8% (174/448 flowers) had their pollinia removed, 19% produced fruits (87/448 flowers), and 16% (70/448 flowers) set mature fruits. Conclusion-Cyrtorchis okuensis is clearly differentiated from C. submontana by its longer and wider floral bracts, longer anther caps, and wider triangular dorsal sepal

A near comprehensive phylogenetic framework gives new insights toward a natural classification of the African genus Cyrtorchis (Angraecinae, Orchidaceae)

International audienceThe genus Cyrtorchis is renowned for its conspicuous white, long-spurred flowers, but also for its challenging problems of species delimitation due to the great morphological resemblance of their flowers. Based on a preliminary visual inspection of 1752 specimens, 27 morphogroups were defined including 6 unpublished taxa. Then, we used a representative sampling of 171 dried and alcohol-preserved specimens representing 20 morphogroups to perform linear morphometrics through multivariate analyses on 43 morphological characters in order to confirm morphogroups delineation and identify their discriminant characters. Moreover, the monophyly of the two sections and of 21 morphological entities was tested through molecular analyses in order to produce a natural classification of the genus. DNA sequences from 69 Cyrtorchis specimens belonging to 15 published taxa (seven from C. sect. Homocolleticon, eight from C. sect. Cyrtorchis), six putative new Cyrtorchis taxa, as well as four taxa used as outgroups, were produced using one nuclear (nrITS-1) and five plastid regions (matK, rps16, trnC-petN intergenic spacer, trnL-trnF intergenic spacer, ycf1), and were analyzed using maximum likelihood and Bayesian approaches. We used this phylogenetic framework to infer the morphological character-state evolution of six floral traits and assess their taxonomic value. Morphological analysis revealed two groups corresponding to the published sections. However, while molecular results recovered the monophyly of C. sect. Cyrtorchis, C. sect. Homocolleticon appears paraphyletic. Of the 21 morphologically defined taxa that were included in the molecular analyses, eight, namely C. aschersonii, C. henriquesiana, C. monteiroae, C. praetermissa, C. ringens, and three new taxa were proven monophyletic. The delimitation of the 19 remaining morphologically identified taxa was assessed using morphological approach only. The ancestral state reconstruction provided new insights into character-state evolution in the genus by inferring the insertion point of the stipites at the rear third of the length of the viscidium as one of the main synapomorphic characters supporting the monophyly of the genus. Furthermore, viscidium structure, stipites shape, and the lateral lobes of the rostellum were found to be important to infer phylogenetic relationships within the genus

Integrating systematics and reproductive biology into African orchid conservation: a case study with the genus Cyrtorchis Schltr. (Angraecinae, Vandeae)

International audienceDeveloping conservation strategies of threatened species involves understanding their taxonomy, ecology and reproductive biology, and to integrate this knowledge into rational conservation management actions. Focusing on Cyrtorchis, we present here an approach that combine taxonomy and reproductive biology to develop the conservation of this angraecoid genus renowned for its challenging species delimitation problem. Indeed, its showy white long-spurred flowers, indicating a probable sphingophilous syndrome, constitute a suitable model for studieson reproductive biology of epiphytic orchids, a first step indispensable for their conservation. By using phylogenetic analyses, we tested the monophyly of 23 species hypotheses delimited using morphometrical analyses to clarify species delimitation. Based on this taxonomic background, we chose seven well-resolved species (C. aschersonii, C. ringens, C. cf ringens, C. chailluana, C. letouzeyi, C. monteiroae and a new species) to study, in our living collection in Yaoundé and in two natural populations, their breeding and pollination systems. A protocol involving phenological monitoring of 414 living specimens was implemented during which 330 hand-controlled pollination tests (177 self-vs 153 cross-pollinations) were conducted to assess factors affecting fruit set and seed viability. Pollination efficiency and reproductive success were assessed using fruit set and viable seeds production. Camera and insect light trapping were used for survey and identificationofpollinators. Preliminary results show that the flowering period of 13 species occurring in Cameroon occurs from February to November, with a flowering peak during the rainy season. For the first time in Central Africa, hawkmoths were confirmed as potential pollinators of three species of Cyrtorchis. Seeds produced are used to supply the African orchid seed bank housed at the University of Yaoundé I which currently includes 146 specimens representing 50% of Cyrtorchis species

Domestication Syndrome in Dacryodes edulis (Burseraceae): Comparison of Morphological and Biochemical Traits between Wild and Cultivated Populations

International audienceFor millennia, people have harvested fruits from the wild for their alimentation. Gradually, they have started selecting wild individuals presenting traits of interest, protecting and cultivating them. This was the starting point of their domestication. The passage from a wild to a cultivated status is accompanied by a modification of a number of morphological and genetic traits, commonly known as the domestication syndrome. We studied the domestication syndrome in Dacryodes edulis (G.Don) H.J.Lam (known as ‘African plum’ or ‘safoutier/prunier’), a socio-economically important indigenous fruit tree species in West and Central Africa. We compared wild and cultivated individuals for their sex distribution; flower, fruit and seed morphometric characteristics; seed germination temporal dynamic and fruit lipid composition. We found a higher percentage of male and male-hermaphrodite sexual types in wild populations than in cultivated ones; a lower fruit and seed mass in wild individuals; and similar mean time of germination, oil content and fatty acid composition between wild and cultivated individuals. Our results are interpreted in light of the presence of a domestication syndrome in D. eduli

Domestication Syndrome in Dacryodes edulis (Burseraceae): Comparison of Morphological and Biochemical Traits between Wild and Cultivated Populations

For millennia, people have harvested fruits from the wild for their alimentation. Gradually, they have started selecting wild individuals presenting traits of interest, protecting and cultivating them. This was the starting point of their domestication. The passage from a wild to a cultivated status is accompanied by a modification of a number of morphological and genetic traits, commonly known as the domestication syndrome. We studied the domestication syndrome in Dacryodes edulis (G.Don) H.J.Lam (known as ‘African plum’ or ‘safoutier/prunier’), a socio-economically important indigenous fruit tree species in West and Central Africa. We compared wild and cultivated individuals for their sex distribution; flower, fruit and seed morphometric characteristics; seed germination temporal dynamic and fruit lipid composition. We found a higher percentage of male and male-hermaphrodite sexual types in wild populations than in cultivated ones; a lower fruit and seed mass in wild individuals; and similar mean time of germination, oil content and fatty acid composition between wild and cultivated individuals. Our results are interpreted in light of the presence of a domestication syndrome in D. edulis.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

P38. More than twenty years of orchid ex situ conservation in Africa and Madagascar

International audienceOrchid conservation represents a significant challenge inTropical Africa and Madagascar, areas in which habitats are facing increasing pressure from agriculture, mining and logging activities. In these regions, a large part of the epiphyte flora is composed of orchids, most of which, when lacking flowers when encountered in the field, are impossible to identify. However, accurate identification is essential for developing conservation strategies since about 69% of tropical Africanand Malagasy orchids are potentially threatened. To overcome this identification problem, a shadehouse cultivation system was developed in São Tomé in 1997 and has now been extended across Continental Africa and Madagascar, providing a powerful tool for conducting thorough orchid inventories since most epiphytes can easily be brought into cultivation and grown to produce fertile, identifiable material. The network currently counts 12 shadehouses in sixcountries and, to date, 32,013 living orchids collected in the field have been grown, representing about 500 species, from which >23,764 herbarium specimens have been collected, most associated with silicagel-preserved material and photos. This material has been usedto describe 41 previously unknown species and to assess the conservation status of hundreds of species in three key areas (West Africa, Central Africa and Madagascar), while also leading to the publication of 44 articles in taxonomy, phylogeny, floristics and for the general public. Initially designed to facilitate orchid inventory and identification, the shadehouses now contribute to orchid conservation by protecting plants in safe, controlled conditions, producing material for seeds banking. They also offer valuable training opportunities for young botanists, thereby contributing to in-country capacity building. Key factors that explain the success of this shadehouse network and its long-term survival are the support provided by reliable local partners, the involvement of young botanists and students, and the development of new techniques to grow thousands of living orchids successfully and cost-effectivel