Allee effects within small populations of Aconitum napellus ssp. lusitanicum, a protected subspecies in northern France.
Plants growing at low density can suffer from Allee effects as a result of pollen limitation. Previous studies of Allee effects have focused on the effects of variation among populations in size or density on reproduction. Here, the effects of plant distribution within populations on fitness components are explored in a rare plant, Aconitum napellus ssp. lusitanicum, and ecological and genetic mechanisms underlying these effects are identified. To detect pollen limitation, seed production was compared under natural versus hand-supplemented pollinations on inflorescences of different sizes in natural patches differing both in flower density and in isolation from other patches. Germination rate and juvenile survival of seeds produced in low- and high-density patches were also compared. Pollen-supplemented flowers always produced more seeds than open-pollinated flowers, especially among small plants and plants growing at low density. Offspring produced in low-density patches exhibited lower fitness that those produced in high-density patches. This could have been caused by post-fertilization mechanisms, including inbreeding depression or differential maternal resource allocation. These results show that Allee effects on fitness components (ecological and genetic Allee effects) occur within A. napellus populations at different spatial scales. The spatial distribution of plants seems to be a crucial factor affecting reproductive output and fitness.
Conservatoire Botanique National du Bassin Parisien (CBNBP), USM Inventaire et Suivi de la Biodiversité, Muséum National d'Histoire Naturelle (MNHN), 61, rue Buffon, F-75005 Paris, France.
Solenn
S
Le Cadre
Laboratoire Fonctionnement et Évolution des Systèmes Écologiques, CNRS UMR 7625, École Normale Supérieure, 46 rue d'Ulm, 75230 Paris cedex 05, France.
Thomas
T
Tully
Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA 93106, USA.
Susan J
SJ
Mazer
Laboratoire GPIA, Université Montpellier II, place Eugène Bataillon, Bt 24 CC063, F-34095 Montpellier cedex, France.
Jean-Baptiste
JB
Ferdy
Conservatoire Botanique National du Bassin Parisien (CBNBP), USM Inventaire et Suivi de la Biodiversité, Muséum National d'Histoire Naturelle (MNHN), 61, rue Buffon, F-75005 Paris, France.
Jacques
J
Moret
Conservatoire Botanique National du Bassin Parisien (CBNBP), USM Inventaire et Suivi de la Biodiversité, Muséum National d'Histoire Naturelle (MNHN), 61, rue Buffon, F-75005 Paris, France.|Unité Conservation des Espèces, Restauration et Suivi des Populations, UMR 5173, Muséum National d'Histoire Naturelle, 61, rue Buffon, F-75005 Paris France.
Nathalie
N
Machon
D031841:Aconitum / Q000235:genetics / Q000254:growth & development*; D003247:Conservation of Natural Resources; D005602:France; D018525:Germination / Q000235:genetics / Q000502:physiology; D011058:Pollen / Q000502:physiology; D054817:Pollination / Q000235:genetics / Q000502:physiology*; D011156:Population Density; D011157:Population Dynamics; D012639:Seeds / Q000235:genetics / Q000254:growth & development