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

Abstract

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