Determinants of extinction in fragmented plant populations: Crepis sancta (asteraceae) in urban environments

• Published in: Oecologia Vol. 169; no. 3; pp. 703 - 712
• Main Authors: Dornier, Antoine, Cheptou, Pierre-Olivier
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer 01.07.2012; Springer-Verlag; Springer Nature B.V
• Subjects: Asteraceae; Biomedical and Life Sciences; Cities; Connectivity; Crepis; Crepis - genetics; Crepis sancta; Demography; Dispersal; Ecological genetics; Ecology; Extinction; Extinction, Biological; Gene flow; Genetic drift; Genetic factors; Genetic structure; genetics; Genotyping; Habitat; habitats; Heterozygosity; Hydrology/Water Resources; Inbreeding; Inbreeding depression; Life Sciences; Local population; Metapopulation ecology; Microsatellites; Plant populations; Plant Sciences; Plants; Pollination; Population Dynamics; Population ecology; Population ecology - Original research; Population genetics; Population number; Population size; Reproduction; risk; Seed Dispersal; Species extinction; Stochasticity; surveys; Urban environments; Rescue effect; Demography; Extinction; Genetic structure; Fragmentation
• ISSN: 0029-8549; 1432-1939; 1432-1939
• DOI: 10.1007/s00442-011-2229-0

Local populations are subject to recurrent extinctions, and small populations are particularly prone to extinction. Both demographic (stochasticity and the Allee effect) and genetic factors (drift load and inbreeding depression) potentially affect extinction. In fragmented populations, regular dispersal may boost population sizes (demographic rescue effect) or/and reduce the local inbreeding level and genetic drift (genetic rescue effect), which can affect extinction risks. We studied extinction processes in highly fragmented populations of the common species Crepis sancta (Asteraceae) in urban habitats exhibiting a rapid turnover of patches. A four-year demographic monitoring survey and microsatellite genotyping of individuals allowed us to study the determinants of extinction. We documented a low genetic structure and an absence of inbreeding (estimated by multilocus heterozygosity), which suggest that genetic factors were not a major cause of patch extinction. On the contrary, local population size was the main factor in extinction, whereas connectivity was shown to decrease patch extinction, which we interpreted as a demographic rescue effect that was likely due to better pollination services for reproduction. This coupling of demographic and genetic tools highlighted the importance of dispersal in local patch extinctions of small fragmented populations connected by gene flow.