Centaurea corymbosa, a cliff-dwelling species tottering on the brink of extinction: A demographic and genetic study

Abstract

Centaurea corymbosa (Asteraceae) is endemic to a small area (<3 km 2 ), and <500 individuals reproduce in any given year. Nevertheless, enzyme polymorphism was found within and among the six local extant populations, the most distant at 2.3 km. Levels of gene f low among populations and seed and pollen dispersal data indicated very low dispersal capacity. Rarity of long distance dispersal events coupled with traits such as prolonged juvenile period, monocarpy, and self-incompatibility precludes the establishment of new populations and thus the evolution toward colonization ability through increased dispersal rate, polycarpy, or selfcompatibility. The species thus appears to be trapped on an evolutionary dead-end toward extinction, even though, from a preliminary introduction experiment, we conclude that several nearby unoccupied sites would be suitable for the species.

Biologie et écologie du gaillet nain (Galium minutulumJordan,Rubiaceae) sur les îles d'Hyères (Var, France); implications pour la conservation de l'espèce

“…En France, les etudes relatives a Ia conservation des vegetaux rares et menaces demeurent peu nombreuses et les caracteristiques biologiques de ces especes sont peu connues (Debussche & Thompson, 1999). La plupart des vegetaux rares etudies en France sont des endemiques perennes " emblematiques " : Cyclamen balearicum (Affre et al, 1995(Affre et al, , 1997Debussche et al, 1996), Centaurea corymbosa (Colas et al, 1997), Anchusa crispa (Quilichini, 1999). Par contre, le statut des especes annuelles rares, fugaces et peu visibles, a jusqu'ici ete neglige (voir cependant Paradis, 1993et Paradis et al, 1995.…”

Ecological magnitude and fine scale dynamics of the mediterranean narrow endemic therophyte,Arenaria provincialis(Caryophyllaceae)

“…Rare and very narrowly distributed mediterranean plant species may show strict ecological requirements and can be restricted to particular habitats (e.g. Colas et al, 1997). Remarkably, although rare and restricted to only 145 km 2 of limestone moutain chains close to Marseilles, A. provincialis is found along a wide altitudinal, i.e.…”

Allopolyploid origin of highly invasive Centaurea stoebe s.l. (Asteraceae)

“…Both of these species are endemics of small regions outside of the continuous C. stoebe range. Furthermore, adaptation to specific habitats, such as crevices of calcareous cliffs in the case of the Mediterranean C. corymbosa (Colas et al, 1997), or extremely dry steppes in the Black Sea region in C. diffusa, could further accelerate morphological differentiation of these taxa.…”