Plant performance in central and northern peripheral populations of the widespread Plantago coronopus

Abstract

Peripheral populations have long been predicted to show lower vital rates, higher demographic fl uctuations, and lower densities than central populations. However, recent research has questioned the existence of clear patterns across species ’ ranges. To test these hypotheses, we monitored fi ve central and six northern peripheral populations of the widespread herb Plantago coronopus along the European Atlantic coast during 5 yr. We estimated population density, and calculated mean values and temporal variability of four vital rates (survival, individual growth, fecundity and recruitment) in hundreds of plants in permanent plots. Central populations showed higher fecundity, whereas peripheral populations had higher recruitment per reproductive plant, indicating a higher overall reproductive success in the periphery. Central populations showed a marginally signifi cant tendency for higher growth, and there were no diff erences between range positions in survival. Fecundity and growth were aff ected by intraspecifi c competition, and recruitment was aff ected by precipitation, highlighting the importance of local environmental conditions for population performance. Central and peripheral populations showed no signifi cant diff erences in temporal variability of vital rates. Finally, density was signifi cantly higher in peripheral than in central populations, in discrepancy with the abundant-centre model. Density was correlated to seedling recruitment, which would counterbalance in peripheral populations the lower fecundity and the tendency for lower growth of established plants. Such compensations among vital rates might be particularly common in widespread plants, and advise against simplistic assumptions of population performance across ranges. Th e whole species ’ life cycle should be considered, since diff erent arrangements of vital rates are expected to maximize fi tness in local environments. Our results show also the importance of discerning between geographical periphery and ecological marginality. In a context of climate-induced range shifts, these considerations are crucial for the reliability of nichemodels and the management of plant peripheral populations.