Predispersal seed predation on five Piper species in tropical rainforest

Abstract

Absolute number of seeds lost to predispersal seed predators and proportion of total seeds lost per infructescence were compared among five Costa Rican Piper species of different annual fecundities. Mean seed number and mean seed size in the five species were negatively correlated. The impact of predation on these species was inversely related to the number of seeds they produced. The two early successional species had very high fecundities, a combination of many seeds per infructescence, many infructescences per plant, and, in one species, year-round reproduction. Although seed predators destroyed as many or more seeds of these early successional species than they did of the less fecund, late successional species, this loss accounted for a relatively minor proportion (9 and 12%) of the seeds of the early successional species. In contrast, late successional species produced fewer, larger seeds in a smaller number of infructescences and were not continually in fruit. One of these species, which produced intermediate numbers of intermediately sized seeds, lost 30% of the seeds in each infructescence on average. Seed predators destroyed a larger proportion (65 and 76%) of the seeds per infructescence in the two species with fewest seeds per infructescence. High levels of insect damage in these late successional species caused many of their infructescences to abort prematurely. Taken together these factors resulted in annual fecundities several orders of magnitude smaller in shade-tolerant Piper species than the annual fecundities of shade-intolerant, early successional species. Seedlings of the two early successional species were common in large gaps and other sunny clearings and seedlings of the species with 30% seed loss were occasional, whereas no seedlings were seen of the two species with the highest proportional seed loss, suggesting that seed predation on the latter species may limit seedling recruitment.

Keywords: Costa Rica; Piper; Plant fecundity; Predispersal seed predation; Tropical rainforest.