Individual crop size increases predispersal predation by beetles in a tropical palm

Predispersal seed predation is one of the main causes of seed mortality in plant populations, contributing to decreased plant recruitment. Seed loss has previously been found to be related to crop size. Thus, we examined the influence of individual crop size on predispersal seed predation by beetles in the palm Syagrus flexuosa in the Brazilian savanna. The study was carried out in three tropical woodland savanna sites, where we sampled the total seed crop of 46 fruiting palms and checked the presence of beetle larvae inside all seeds per plant. We observed predispersal seed predation of S. flexuosa from all sites and a high variation in the number of seeds preyed on per individual palm. Crop size had a positive influence on the number of seeds lost to predispersal seed predators. Variations in levels of predispersal seed predation may also be accounted for by the reproductive phenology of S. flexuosa. If fruits are not available at the same time, less resource is available for predators and therefore a high proportion of seeds may be preyed on. Thus, our study demonstrates that an individual plant trait, crop size, is an important predictor of beetle seed damage per palm and a driver of the number of seeds lost to predispersal seed predators.

Predispersal seed predation on three Vachellia species and one Senegalia species (Fabaceae: Mimosoideae) in the Rift Valley of Ethiopia and Menagesha forest, Ethiopia

This study on predispersal seed predation of the leguminous speciesVachellia abyssinica(Hochst. Ex. Benth.) Kyal & Boatwr.,Senegalia senegal(L.) Britton,Vachellia seyal(Del.) P.J.H. Hurter, andVachellia tortilis(Forssk.) Galasso & Banfi was conducted around Lake Langano and Menagesha Forest in Ethiopia to identify the associated seed predators and determine their impact on seed germination. Eight seed beetlesBruchidius albosparsus(Fåhraeus, 1839),B. aurivillii(Blanc, 1889),B. djemensisDecelle 1971,B. discoidalis(Fåhraeus, 1839),B. sinaitus(K. Daniel, 1907),B. silaceus(Fåhraeus, 1839),B. sp 411,B. simulans(Anton and Delobel, 2003), and one unidentified species of Cerambycidae were found associated with seeds of theseAcaciaspecies. These predators damaged less than 9% of seeds of these species, which exhibited lower germination. This study provides unrecorded lists of predispersal seed predators associated with seeds ofVachelliaandSenegaliaspecies in Ethiopia, and some associations are new. There is need to assess the distribution, abundance and effects of predispersal seed predators on otherVachellia, as well as other tree species.

Evidence of a component Allee effect driven by predispersal seed predation in a plant ( Pedicularis rex , Orobanchaceae)

A small or sparse population may suffer a reduction in fitness owing to Allee effects. Here, we explored effects of plant density on pollination, reproduction and predation in the alpine herb Pedicularis rex over two years. We did not detect a significant difference in the pollination rate or fecundity (fruit set and the initial seed set) before predation between sparse and dense patches in either year, indicating no pollination-driven Allee effect. However, dense patches experienced significantly fewer attacks by predispersal seed predators in both years, resulting in a significantly decreased realized fecundity (final seed set), suggesting a component Allee effect driven by predispersal seed predation. Predation-driven Allee effects have been predicted by many models and demonstrated for a range of animals, but there is scant evidence for such effects in plants. Our study provides strong evidence of a component Allee effect driven by predation in a plant species.