Abstract
Mast-seeding species exhibit not only a large inter-annual variability in seed production but also considerable variability among individuals within the same year. However, very little is known about the causes and consequences for population dynamics of this potentially large between-individual variability. Here, we quantified seed production over ten consecutive years in two Mediterranean oak species – the deciduous Quercus canariensis and the evergreen Q. suber - that coexist in forests of southern Spain. First, we calibrated likelihood models to identify which abiotic and biotic variables best explain the magnitude (hereafter seed productivity) and temporal variation of seed production at the individual level (hereafter CVi), and infer whether reproductive effort results from the available soil resources for the plant or is primarily determined by selectively favoured strategies. Second, we explored the contribution of between-individual variability in seed production as a potential mechanism of satiation for predispersal seed predators. We found that Q. canariensis trees inhabiting moister and more fertile soils were more productive than those growing in more resource-limited sites. Regarding temporal variation, individuals of the two studied oak species inhabiting these resource-rich environments also exhibited larger values of CVi. Interestingly, we detected a satiating effect on granivorous insects at the tree level in Q. suber, which was evident in those years where between-individual variability in acorn production was higher. These findings suggest that individual seed production (both in terms of seed productivity and inter-annual variability) is strongly dependent on soil resource heterogeneity (at least for one of the two studied oak species) with potential repercussions for recruitment and population dynamics. However, other external factors (such as soil heterogeneity in pathogen abundance) or certain inherent characteristics of the tree might be also involved in this process.
Highlights
There is a growing interest, from an ecological and evolutionary perspective, in understanding the phenomenon of mast-seeding, a very common reproductive strategy in perennial plants that consists of producing occasional large seed crops followed by years of low seed production with a high level of synchronization among neighbouring individuals [1,2,3]
Applying this hypothesis to variation among individuals instead of among years, it would be expected that plants growing in moister and more fertile soils will produce on average larger seed crops than those growing in resource-limited environments
The two studied oak species showed considerable variability among years in seed production, with higher values of CVp and component of individual seed production (CVi) for Q. canariensis compared with Q. suber (Table 1 and Fig. 1)
Summary
There is a growing interest, from an ecological and evolutionary perspective, in understanding the phenomenon of mast-seeding, a very common reproductive strategy in perennial plants that consists of producing occasional large seed crops followed by years of low seed production with a high level of synchronization among neighbouring individuals [1,2,3]. Between-individual variability in seed production could merely respond to variation in available resources for the plant, by analogy with the most parsimonious explanation for masting (resource-tracking hypothesis [2], [9]). Applying this hypothesis to variation among individuals instead of among years (i.e. spatial instead of temporal variation), it would be expected that plants growing in moister and more fertile soils will produce on average larger seed crops than those growing in resource-limited environments. To what extent reproductive investment tracks resource availability or is primarily determined by selectively favoured strategies is a question that remains largely unexplored, in long-lived species whose reproductive performance varies episodically over time
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
