Impacts of seed-feeding beetles and their parasitoids on seed germination of Leucaena leucocephala and Senna multijuga (Fabaceae) in Brazil

Abstract

We investigated the influence of seed-feeding beetles (Chrysomelidae, Bruchinae) and their parasitoids on the germination performance of two Fabaceae, Leucaena leucocephala and Senna multijuga. We collected 150 fruits per species in forest fragments in the city of Lavras, Minas Gerais, Brazil, between July and August 2020. Seeds were examined and separated into predated and non-predated categories. The predated category was divided into two subcategories: predated by Coleoptera (Bruchinae) (PCO) and predated in the presence of Coleoptera parasitoids (PARCO). The non-predated category was divided into artificially injured (AI), intact seeds without insect infestation (IS), and intact seeds with insect infestation (SIF). Seeds of S. multijuga and L. leucocephala germinated to 40% and 30%, respectively. PCO and PARCO seeds not only had a negative and restricting influence on S. multijuga germination (no germination) but also contributed to a large proportion of non-viable predated seeds (38%). PCO (7%) and PARCO (23%), on the other hand, improved L. leucocephala germination. This work represents one of the first attempt to evaluate the parasitoid effect on seeds germination. Our results contribute to a better understanding of the effect of herbivore predation and the presence of parasitoids on host plant seed germination, which can be critical to mother plant fitness depending on plant species. Further studies are necessary to determine the extend seed consumption by beetles and the presence of their parasitoids may facilitate or impair seed germination, and consequently plant fitness in other systems.