Effects of pulsed resources on the dynamics of seed consumer populations: a comparative demographic study in wild boar

Abstract

Mast seeding is a well-known example of pulsed resources in terrestrial ecosystems. Despite the large literature available so far on the effects of mast seeding on the dynamics of seed consumer populations, it remains unknown whether heterogeneity in demographic responses to mast seeding exists both within a population of consumers and among consumer populations. Here, we fill this knowledge gap by assessing the effects of acorn production (i.e., oak mast) on all stage-specific demographic rates (i.e., survival, growth, reproduction) in several consumer populations. From long-term capture-mark-recapture data collected in three wild boar populations in Europe and detailed information on annual acorn production, we quantified the effects of acorn production on body mass-specific demographic rates in these populations. We then built a body mass-structured population model for each population and assessed the effect of acorn production on generation time-the mean age of mother at childbirth-and population growth rate using a combination of prospective and retrospective demographic analyses. Within populations, acorn production had a positive effect on reproduction (proportion of breeding females) and growth of small-sized females. Survival remained buffered against environmental variation, in accordance with the demographic buffering hypothesis. Thus, all stage-specific demographic rates were not influenced in the same way by acorn production. In turn, higher reproduction and growth probabilities involved higher population growth rates and shorter generation times. Despite these common demographic responses to mast seeding among populations, we highlighted marked among-population variation in the magnitude of these responses. Also, while populations inhabiting resource-rich environments took advantage of current acorn conditions, populations under resource-poor environments stored and allocated acorns produced the preceding year to reproduction indicating contrasting breeding tactics along the capital-income continuum. Our results suggest heterogeneity in demographic responses to mast seeding, within and among populations. This is an important finding for our understanding of the effects of mast seeding on the dynamics of seed consumer populations.

Amplified Cyclicality in Mast Seeding Dynamics Positively Influences the Dynamics of a Seed Consumer Species

“…blue noise) the mean generation time of our population (i.e. 2.46 years and 2.50 years for good and poor years of acorn production, respectively; see Gamelon et al 2021a). This is the author's accepted manuscript without copyediting, formatting, or final corrections.…”

“…This fast-living species has a short generation time of about two years (Servanty et al 2009 andGamelon et al 2012 and2021). Taking advantage of long-term capture-mark-recapture data collected in a wild boar population and information on annual acorn production, we previously showed that increasing acorn availability positively influenced the probability for a female to reproduce and, hence, increased population growth rate (Touzot et al 2020;Gamelon et al 2021a). However, whether a good match between wild boar generation time and cyclicality of mast seeding events positively influences population growth rate has never been tested.…”

Plasticity’s role in adaptive evolution depends on environmental change components

“…Such differences cause further disparities in transient dynamics of population trends [62]. Further, nonlinear relationships between environmental states and vital rates across st/age classes within populations ('reaction norms') can induce varying demographic buffering capabilities across populations and species [63,64]. Variation in degrees of demographic buffering via plasticity of vital rates, can contribute to the observed inconsistencies in comparative analyses of population dynamics in variable environments [65].…”

Does mast seeding shape mating time in wild boar? A comparative study

“…Any changes in the amount of berries available may thus impact bears' reproduction. Likewise, high seed production positively influences the reproductive output of seed consumer species such as eastern chipmunk (Tamias striatus) [20] or wild boar (Sus scrofa) [11,21]. For the latter, improved reproductive performance following high acorn availability positively influences population growth rate [11,[21][22][23], with potentially important implications for management and conservation [24].…”

“…Likewise, high seed production positively influences the reproductive output of seed consumer species such as eastern chipmunk (Tamias striatus) [20] or wild boar (Sus scrofa) [11,21]. For the latter, improved reproductive performance following high acorn availability positively influences population growth rate [11,[21][22][23], with potentially important implications for management and conservation [24]. Understanding how quantitative changes in mast seeding influence the timing of reproduction of seed consumers, not only their reproductive output, is crucial in the current context of global warming and remains to be investigated.…”