COS 291-1 - Intraspecific variation in masting patterns largely unrelated to climate

Abstract: Highly variable, yet synchronised seed production (i.e. masting) is a widespread behaviour in plant species from diverse ecosystems and taxa. Masting has cascading effects on wider communities and enhances the ability of plant populations to regenerate, recover from disturbance and migrate in response to a changing climate. Yet, we have a limited understanding of how much intraspecific variation in masting occurs across space, and what drives this variation. Our aims are twofold: to investigate how much intraspecific variation exists in reproductive behaviour, and to examine if the environmental stress hypothesis explains the striking variability in masting. Using 435 time-series (8049 annual records, 19 species) from the MASTREE+ database, we capture the intraspecific variation in masting using three commonly utilised metrics: CV_p, AR(1), and P<sub>sd, characterising respectively the interannual variability of seed production, the temporal autocorrelation at lag 1, and the proportion of high seed production events. We found that for the majority of species the observed intraspecific range in metrics exceeded the interspecific ranges, in some cases by more than a factor of 2. This demonstrates much higher intraspecific variation than expected. Next, we conducted polynomial species-centered linear regression models to test if climatic distance from median "core" climates explained the intraspecific variation in masting. No strong evidence was found that intraspecific variation in CV_p varied in congruence with the environmental stress hypothesis. The intraspecific variation in AR(1) and P<sub>sd partially matched the predictions, although effect sizes were small. Species-specific models revealed that while the significant intraspecific relationships with climatic gradients are (partly) coherent with the theory of environmental stress, no species conformed to the overall theoretic framework across gradients and metrics. This study suggests that there is no clear delineation between masting and non-masting species, and that masting within species is likely highly context dependent. Our ability to predict responses of masting to changing environmental conditions will depend on our ability to explain this plasticity, particularly because climate gradients seem to play a limited role.