Under-producers have a greater effect than super-producers on fruiting patterns in masting trees

Masting is a phenomenon in which a population of a given plant species reproduces en masse, producing a large, synchronized seed-set at periodic intervals. The strategy has the advantage of overwhelming seed predators in mast years while starving them in between. Older and larger individuals referred to as “super producers” are known to produce larger seed crops in general, and in some cases have been shown to be more synchronous in their production of seeds on mast years, an advantage in their reproductive success. But does this relationship hold at the lower end of the spectrum? Are smaller plants less fecund or less synchronous than larger ones?

In a new paper published in Annals of Botany, Michał Bogdziewicz and colleagues investigated whether plant size is related to both fecundity and variation in masting patterns. The group looked at 12 different mast seeding species, analyzing size, annual variation in seed set (fecundity), and predation over a period of 12 to 30 years. The species studied included both angiosperms and gymnosperms, as well as both arboreal and herbaceous plants.

The researchers found that across the species studied, small plants produced low numbers of seeds and regularly failed to produce any at all. This made their fecundity more variable and drove down their synchrony with the masting of others in their population. The effect is thought to be related to the tendency of smaller plants to allocate resources to growth over reproduction.

In general, masting plants seem to have a similar seed production regime over a wide variety of sizes, with small and low-fertility plants being the main drag on seed production and reproductive synchrony of the population. This effect is more significant than what is seen at the upper end of the spectrum. “In other words, in terms of masting patterns, there are no “super-producers”, but rather normal plants and sub-producers. This distinction is important biologically, as it shows that rather than the most fecund plants behaving differently from other plants in the population, the least fertile individuals are the outliers,” write the authors. Predation data did not show an association between fecundity and seed predation. “This pattern suggests that failure years do not have a decisive influence on the insect seed predators’ populations in these species, possibly because predators are able to move between plants,” noted the authors.