Seed‐feeding by bruchine beetles can accelerate seedling emergence but increases its long‐term mortality

Beetles of the subfamily Bruchinae (bruchine) can increase the speed of seed germination by breaking physical dormancy. However, the larval feeding also consumes part of the endosperm, resulting in a loss of reserves and creating doubts about the seedlings' ability to survive. Consequently, the increase in germination speed may lead to misguided conclusions that bruchines can also favour seedling survival.

Because the bruchine Acanthoscelides macrophthalmus increases the germination speed of Leucaena leucocephala seeds, we tested the hypotheses that the speed of seedling emergence of L. leucocephala increases when the seeds are infested with A. macrophthalmus as well as that seedlings from the infested seeds do not have long‐term survival

Leucaena leucocephala seeds were subjected to three treatments: (1) scarified intact seeds; (2) non‐scarified intact seeds (intact seeds); and (3) infested seeds. All seeds were individually sowed in seedling tubes filled with soil, which were kept in an acclimatised room at 25 ± 3.0°C and 24 h light. The number of emerging seedlings and those that died after emergence was recorded for 121 days.

We found that seedlings from the infested seeds emerged faster than those from the intact seeds; 94.1% of the seedlings emerged within the first 10 days of sowing, and all seedlings from the intact seeds emerged after this time period. However, most seedlings from infested seeds survived less than 30 days. We showed that although seedling emergence increases when seeds are infested, they do not survive, suggesting that A. macrophthalmus acts as a predator of L. leucocephala seeds.