Phenotypic plasticity in Acanthoscelides quadridentatus (Coleoptera: Chrysomelidae) and its effect on the seed fate of Mimosa setosa (Leguminosae: Mimosoideae)

In animals, changes in colour pigmentation in an intraspecific context are usually described as a polymorphism adaptive to environmental factors. According to the thermal melanism hypothesis (TMH), melanic individuals are more active because they may attain higher temperature and then benefit from higher size, foraging time and reproduction. The polymorphic seed-beetle Acanthoscelides quadridentatus (Coleoptera: Chrysomelidae) naturally attacks the seeds of two plant varieties, Mimosa setosa var. paludosa and M. setosa var. setosa, in the Brazilian savanna. The authors tested TMH in this system, predicting that melanic beetles would be larger, and infringe worst germination rate and higher seed mortality. Additionally, they tested whether seed weight plays a role in germination. The authors found two beetle morphs: a melanic/1.1-fold larger and another lighter/smaller. Seeds of M. setosa var. setosa are 1.9-fold heavier and its intact seeds germinate faster and with a higher amount than the seeds of M. setosa var. paludosa. There is no difference in the attack rate by beetle morphs. The attacked seeds of both plant varieties did not germinate. The authors evidence phenotypic plasticity in A. quadridentatus, highlighting that TMH is confirmed for the relationship between melanism and larger sizes, although there was no difference in foraging of melanic individuals. This study shed light on the importance of plant varieties in driving the morphology of seed-beetles.

Automated summary

In animals, changes in color pigmentation are usually adaptive to environmental factors. The authors tested the thermal melanism hypothesis in a seed-beetle species and found that melanic beetles were larger and had an impact on seed germination and mortality. This study highlights the importance of plant varieties in driving the morphology of seed-beetles.