Accounting for stochasticity in demographic compensation along the elevational range of an alpine plant

Abstract

Demographic compensation arises when vital rates change in opposite directions across populations, buffering the variation in population growth rates, and is a mechanism often invoked to explain the stability of species geographic ranges. However, studies on demographic compensation have disregarded the effects of temporal variation in vital rates and their temporal correlations, despite theoretical evidence that stochastic dynamics can affect population persistence in temporally varying environments. We carried out a seven-year-long demographic study on the perennial plant Arabis alpina (L.) across six populations encompassing most of its elevational range. We discovered demographic compensation in the form of negative correlations between the means of plant vital rates, but also between their temporal coefficients of variation, correlations and elasticities. Even if their contribution to demographic compensation was small, this highlights a previously overlooked, but potentially important, role of stochastic processes in stabilising population dynamics at range margins. N, number of individuals. Daily mean temperature (T mean ) and daily temperature range (T range ) were measured with in-situ data-loggers. Values are means and (minimum and maximum) over plots and years for the month of July. Means and 95% confidence interval for the stochastic population growth rate (logk s ) were calculated by randomly sampling the values calculated using matrix populations models constructed using predicted vital rates from 200 bootstrapped demographic datasets and 10 resampled imputed datasets. The N per site per year is shown in Figure S2.

Arabis alpina: A perennial model plant for ecological genomics and life‐history evolution

“…In addition to showing little spatial variation, population growth rates were negative in all sites, suggesting that populations are declining and might eventually go locally extinct (Andrello et al, 2020).…”

Arabis alpina: a perennial model plant for ecological genomics and life-history evolution

“…These findings in A. alpinareflect common patterns in life histories of herbaceous plants: Small, long-lived species tend to inhabit high elevations, and vice-versa (Laiolo & Obeso, 2017;Nobis & Schweingruber, 2013). Andrello et al (2020) also observed that individual A. alpina plants frequently grew larger and produced more fruits when the surrounding vegetation was composed of tall-growing species with large specific leaf areas. This could indicate a response to competition with other plants or an effect of temperature, because vegetative height and specific leaf area commonly increase with temperature (Read, Moorhead, Swenson, Bailey, & Sanders, 2014;Rosbakh, Römermann, & Poschlod, 2015).…”

“…Despite marked clines in demographic rates along elevation, A. alpina showed surprisingly little variation in population growth rates across its full elevational range (Andrello et al, 2020). This lack of spatial variation in growth rates could be partly ascribed to demographic compensation among different life-cycle components (Andrello et al, 2020).…”

Climate change impacts on population growth across a species’ range differ due to nonlinear responses of populations to climate and variation in rates of climate change

“…Only a few studies quantify how sensitivity varies across populations across a species' range (e.g., ref. [41]), and fewer still quantify whether this variation arises from local adaptation or simply variation in driver values across a species' range. Past work suggests that populations should be relatively insensitive to climate drivers that were historically highly variable [42].…”