The fate of natural populations is mediated by complex interactions among vital rates, which can vary within and among years. While the effects of random, among-year variation in vital rates have been studied extensively, relatively little is known about how periodic, non-random variation in vital rates affects populations. This knowledge gap is potentially alarming as global environmental change is projected to alter common periodic variations, such as seasonality. We investigated the effects of changes in vital-rate periodicity on populations of three species representing different forms of adaptation to periodic environments: the yellow-bellied marmot (Marmota flaviventer), adapted to strong seasonality in snowfall; the meerkat (Suricata suricatta), adapted to inter-annual stochasticity as well as seasonal patterns in rainfall; and the dewy pine (Drosophyllum lusitanicum), adapted to fire regimes and periodic post-fire habitat succession. To assess how changes in periodicity affect population growth, we parameterized periodic matrix population models and projected population dynamics under different scenarios of perturbations in the strength of vital-rate periodicity. We assessed the effects of such perturbations on various metrics describing population dynamics, including the stochastic growth rate, log λ_S. Overall, perturbing the strength of periodicity had strong effects on population dynamics in all three study species. For the marmots, log λ_S decreased with increased seasonal differences in adult survival. For the meerkats, density dependence buffered the effects of perturbations of periodicity on log λ_S. Finally, dewy pines were negatively affected by changes in natural post-fire succession under stochastic or periodic fire regimes with fires occurring every 30 years, but were buffered by density dependence from such changes under presumed more frequent fires or large-scale disturbances. We show that changes in the strength of vital-rate periodicity can have diverse but strong effects on population dynamics across different life histories. Populations buffered from inter-annual vital-rate variation can be affected substantially by changes in environmentally-driven vital-rate periodic patterns; however, the effects of such changes can be masked in analyses focusing on inter-annual variation. As most ecosystems are affected by periodic variations in the environment such as seasonality, assessing their contributions to population viability for future global-change research is crucial.

Data collection

Yellow-bellied marmot (Marmota flaviventer) 

We used seasonal data on survival, life-history stages, and recruitment of individual female yellow-bellied marmots. The data were collected between 1976 and 2016 in nine marmot colonies living at 2900 masl in the upper East River Valley near Gothic, Colorado, United States. To collect these demographic data, individuals were live-trapped each year throughout their summer active season, and ear-marked in the first capture event.

Meerkat (Suricata suricatta)

We used seasonal data on survival, life-history stages and social status, emigration, and recruitment of individual female meerkats. The data were collected by frequently visiting (one to three times per week) wild groups of individually-marked meerkats in the Kuruman River Reserve, South Africa. For this study, we used 20 years of individual data (1997–2016). We also used data on population density, calculated as the number of individuals per km² of population range at each census.

Dewy pine (Drosophyllum lusitanicum) 

We used data on survival, life-history stages, and reproduction of individual dewy pines. The data were collected annually for nine years between April 2011 and April 2019 on dewy-pine populations occurring in three sites of southern Spain and facing different types of post-fire disturbance: human-disturbed (i.e., heavy persistent browsing) or natural (i.e., little browsing). The seed bank-related vital rates (seed germination or stasis) were estimated from seed-burial and greenhouse germination experiments. In addition, we used data on population density, calculated as the number of aboveground dewy pines per 1-m² square within a study transect in each site and each post-fire habitat state.

The dataset contains all data (as .csv files) to replicate the analyses performed in Conquet et al. 2022 "Demographic consequences of changing environmental periodicity", Ecology. Information regarding specific files is available in the README files.