Variation in stochastic demography between and within central and peripheral regions in a widespread short‐lived herb

Abstract

Analyzing intraspecific variation in population dynamics in relation to environmental factors is crucial to understand the current and future distributions of plant species. Across ranges, peripheral populations are often expected to show lower and more temporally variable vital rates than central populations, although it remains unclear how much any differences in vital rates actually contribute to differences in population growth rates. Moreover, few demographic studies accounting for environmental stochasticity have been carried out both at continental and regional scales. In this study we calculated stochastic growth rates in five central and six northern peripheral populations of the widespread shortlived herb Plantago coronopus along the Atlantic Coast in Europe. To evaluate at two spatial scales how mean values and variability of vital rates (i.e., fecundity, recruitment, survival, growth, and shrinkage) contributed to the differences in stochastic growth rates, we performed Stochastic Life Table Response Experiment (SLTRE) analyses between and within central and peripheral regions. Additionally, we searched for correlations between vital rate contributions and local environmental conditions. Lower mean values and greater variability for some vital rates in peripheral than in central populations had an overall negative but nonsignificant effect on the stochastic growth rates in the periphery. Different life cycle components accounted for differences in population growth depending on spatial scale, although recruitment was the vital rate with the highest influence both between and within regions. Interestingly, the same pattern of differentiation among populations was found within central and peripheral areas: in both regions, one group of populations displayed positive contributions of growth and shrinkage and negative contributions of recruitment and survival; the opposite pattern was found in the remaining populations. These differences in vital rate contributions among populations within regions were correlated with precipitation regime, whereas at the continental scale, differences in contribution patterns were related to temperature. Altogether, our results show how populations of P. coronopus exhibit life cycle differences that may enable the species to persist in locations with widely varying environmental conditions. This demographic flexibility may help to explain the success of widespread plants across large and heterogeneous ranges.

Divergence between phenotypic and genetic variation within populations of a common herb across Europe

“…The existence of a distinct phylogenetic clade containing all the northern populations analyzed in this study supports this hypothesis. It is interesting to note, though, that in contrast with past demographic events, northern peripheral populations of P. coronopus show at present higher densities and comparable population sizes and growth rates than central ones (Villellas et al 2013a, Villellas et al 2013b). Similar divergences between present demographic and genetic patterns have been indeed reported for other perennial herbs, such as Lychnis viscaria (Lammi et al 1999) and Cirsium heterophyllum (Jump et al 2003), and call for caution when using information from one component of species' biology to infer patterns in other components.…”

“…On the other hand, the reliability of environmental variation as an indicator for evolutionary potential must not always be taken for granted, because stochasticity could sometimes result in a lower demographic performance of populations (Lewontin and Cohen 1969) that would hamper the development of their evolutionary potential. However, populations of P. coronopus with higher environmental (and phenotypic) variation show similar growth rates than those subject to lower environmental variation (Villellas et al 2013b), suggesting no demographic limitations for evolutionary potential.…”

Predicting changes in the distribution and abundance of species under environmental change

“…Indeed, none of these ‘hybrid’ approaches allow vital rates to respond idiosyncratically to climate variation, despite evidence that they do (Doak & Morris ; Villellas et al . ,b). A general problem with hybrid models is that they continue to rely on SDMs to predict vital rates, carrying capacity or suitable habitat.…”

Ecological and evolutionary impacts of changing climatic variability

“…If so, vital rate variances may be higher in peripheral populations, suggesting that even higher climatic variability beyond the margin may be contributing to the range limit. While some studies have found higher demographic variation in peripheral populations (Angert, ; Doak & Morris, ), others have not (Villellas et al, ; Villellas, Morris & García, ).…”