Wednesday, February 11, 2015

[Botany • 2015] Sirdavidia solannona • An Extraordinary New Genus of Annonaceae from Gabon


Sirdavidia solannona Couvreur & Sauquet.

Abstract
A distinctive new monotypic genus from Gabon is described in the tropical plant family Annonaceae: Sirdavidia, in honor to Sir David Attenborough. Molecular phylogenetic analyses confirm that Sirdavidia, which is very distinct from a morphological standpoint, is not nested in any existing genus of Annonaceae and belongs to tribe Piptostigmateae (subfamily Malmeoideae), which now contains a total of six genera. The genus is characterized by long acuminate leaves, fully reflexed red petals, 16–19 bright yellow, loosely arranged stamens forming a cone, and a single carpel topped by a conspicuous stigma. With just three known collections, a preliminary IUCN conservation status assessment is provided as “endangered” as well as a distribution map. The discovery of Sirdavidia is remarkable at several levels. First, it was collected near the road in one of the botanically best-known regions of Gabon: Monts de Cristal National Park. Second, its sister group is the genus Mwasumbia, also monotypic, endemic to a small area in a forest in Tanzania, some 3000 km away. Finally, the floral morphology is highly suggestive of a buzz pollination syndrome. If confirmed, this would be the first documentation of such a pollination syndrome in Magnoliidae and early-diverging angiosperms in general.

Keywords: Piptostigmateae, Monts de Cristal, buzz pollination, vicariance, Annonaceae, Central Africa, Magnoliidae


Figure 1. Maximum likelihood tree with support values indicated on branches (ML bootstrap above; MP bootstrap below). Flower morphology of the genera in the Piptostigmateae tribe.
a Annickia affinis (Exell) Versteegh & Sosef b Greenwayodendron suaveolens (Engl. & Diels) Verdc c Piptostigma multinervium Engl. & Diels d Polyceratocarpus parviflorus (Baker) Ghesq e Sirdavidia solannona f Mwasumbia alba.
Photos: TLP Couvreur. Note: there is some confusion around the proper identification of the accession Lugas 111 (Woodiellantha sp in this study). | doi: 10.3897/phytokeys.46.8937

Taxonomic description

Sirdavidia Couvreur & Sauquet, gen. nov.

 Diagnosis: Genus with Solanum-like flowers, inflorescences axillary or cauliflorous, sepals valvate, petals valvate, subequal, recurved at anthesis, red; stamens bright yellow; carpel single; monocarp sessile, placentation lateral, ovules uniseriate.

Type species: Sirdavidia solannona Couvreur & Sauquet.

Small trees with distichous, simple pinnately veined leaves with an entire margin and reticulate third-order venation. Species androdioecious (?) (flowers unisexual staminate or bisexual). Inflorescences one to three-flowered, axillary on old branches or at base of trunk, with one to three short sympodial rachilla. Flowers actinomorphic. Perianth of 9 free tepals in 3 alternate, valvate whorls of 3 each, differentiated in outer tepals (sepals) and middle and inner tepals (petals). Petals similar (subequal in length), spreading horizontally or reflexed at anthesis. Stamens 16-19, free, basifixed with a very short filament. Anthers introrse, probably opening by two longitudinal slits, connectives tongue shaped, yellow. Carpel one, densely pubescent, stigma cylindrical coiled, ovules 7–10, uniseriate. Monocarp sessile, cylindrical densely pubescent.


Figure 4. Sirdavidia solannona.
a
Opened flower and flower buds (Couvreur 596) b Flower with recurved petals at anthesis (Couvreur 596) c Staminate flower (Couvreur 597) d Flower with all petals and part of the stamens removed, showing the silvery aspect of the carpel and the long stigma (Couvreur 596) e Cauliflorous flower and flower bud (Couvreur 596) f Young fruit, cauliflorous (Couvreur 596).
Photos: TLP Couvreur | Annonaceae.myspecies.info | doi: 10.3897/phytokeys.46.8937

A single species only known to Gabon (Fig. 2).

Etymology: We dedicate this new genus to Sir David Attenborough, British broadcaster and naturalist, in honor of his lifelong dedication to nature, conservation, evolution and natural history programs. His passion for nature have influenced and inspired a generation of biologists and naturalists, including the first and senior authors of this paper. The species name epiteth highlights the striking resemblance with flowers of some species of Solanum, an unusual and new feature for a flower of Annonaceae.




Figure 4. Sirdavidia solannona.
a Opened flower and flower buds (Couvreur 596) b Flower with recurved petals at anthesis (Couvreur 596) c Staminate flower (Couvreur 597) d Flower with all petals and part of the stamens removed, showing the silvery aspect of the carpel and the long stigma (Couvreur 596) e Cauliflorous flower and flower bud (Couvreur 596) f Young fruit, cauliflorous (Couvreur 596).
Photos: TLP Couvreur | Annonaceae.myspecies.info | doi: 10.3897/phytokeys.46.8937

Thomas L.P. Couvreur, Raoul Niangadouma, Bonaventure Sonké and Hervé Sauquet. 2015. Sirdavidia, An Extraordinary New Genus of Annonaceae from Gabon.
PhytoKeys 46: 1-19. doi: 10.3897/phytokeys.46.8937

Plant genus named after Sir David Attenborough http://gu.com/p/45fny/stw

Résumé: Un nouveau genre monotypique du Gabon est décrit dans la famille tropicale des Annonaceae: Sirdavidia, en honneur à Sir David Attenborough. Des analyses phylogénétiques confirment que Sirdavidia, caractérisé par une morphologie unique, n’appartient à aucun genre connu d’Annonaceae et se place au sein de la tribu des Piptostigmateae (dans la sous-famille des Malmeoideae), laquelle compte désormais un total de six genres. Le genre est caractérisé par des feuilles avec un long acumen, des pétales rouges réfléchis, 16–19 étamines jaunes qui forment un cône lâche et un carpelle surmonté d’un stigmate bien visible. Avec seulement trois récoltes connues, un statut de conservation préliminaire de “endangered” est proposé sur la base des critères de l’UICN. Une carte de distribution est également fournie. La découverte de Sirdavidia est remarquable pour plusieurs raisons. Tout d’abord le nouveau genre a été collecté près de la route dans l’une des régions les plus connues botaniquement du Gabon: le Parc National des Monts de Cristal. Ensuite, son groupe-frère est le genre, Mwasumbia, également monotypique, endémique d’une petite région en Tanzanie à plus de 3000 km. Enfin, les caractères floraux suggèrent un syndrome de pollinisation appélé « buzz pollination». Si cela se confirme, ce sera la première documentation de ce type de syndrome pour les Magnoliidae et les Angiospermes basales en général.

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