Host shift capability of a specialist seed predator of an invasive plant: roles of competition, population genetics and plant chemistry

Abstract

Acanthoscelides macrophthalmus is a seed predator that has become widely distributed along with its native host, Leucaena leucocephala (Mimosoideae), which is a neotropical leguminous tree and one of the most invasive plants worldwide. Previous studies revealed that A. macrophthalmus is able to host-shift to several mimosoid species. Here, we aim to test the hostshift potential to other mimosoid and non-mimosoid plants and possible roles of interspecific competition, genetic background, and plant chemistry in host-shift. First, we found that A. macrophthalmus predator completed development on two new hosts: pigeon pea Cajanus cajan and Cajanus scarabaeoides (Faboideae), by rearing from seeds collected in South/Southeast Asia and Hawaii. In contrast, in most regions, both Cajanus species were infested only by other beetle species. Second, we performed no-choice tests using 11 leguminous plants, covering all three subfamilies as potential hosts, including the two new hosts. A Taiwanese A. macrophthalmus population reared in the laboratory on Leucaena did not deposit eggs on any of the seeds of each tested species. To compare host-shift responses between populations, we also used a Hawaiian A. macrophthalmus population that had completed its development on freshly collected Leucaena seeds from the field. This population deposited eggs onto and hatching larvae burrowed into C. cajan seeds, although none developed beyond the larval stage. Third, the surface chemical composition of seed-pods of L. leucocephala and the two Cajanus species was dissimilar, although that of seeds was highly similar. Finally, all of the host-shifting A. macrophthalmus populations shared the same haplotypic group.

New haplotype and inter‐strain reproductive compatibility ofWolbachia‐uninfected alfalfa weevil,Hypera postica(Coleoptera:Curculionidae), inJapan

“…Multiple genetic strains have been identified in various invasive alien insect pests in areas of their introduction (Rauch & Nauen ; Tuda et al . 2004, 2014a,b; Horowitz et al . ; Boubou et al .…”

How bean weevil (Acanthoscelides obtectus, Coleoptera, Bruchinae) larvae die on legume seeds

“…Egg-laying should be accompanied by physiological adaptation of larvae to handle compounds metabolically once they are inside seeds [60,61]. Unless preadaptation [62] played a role, as was recently suggested with a related species (A. macrophthalmus) [63,64], host-shift with the bean weevil is less likely.…”

Métodos alternativos para controle de insetos praga em sementes

“…Com a maturidade, a semente está apta a demonstrar seu vigor fisiológico, dependente das condições ambientais e das características genéticas presentes na semente, podendo, assim, ser passível de classificação de acordo com sua capacidade de germinação, emergência e vigor (Paparella et al, 2015). Um dos importantes fatores depreciadores da qualidade das sementes são as injúrias de natureza biológica, como o ataque de insetos-praga (Miransari & Smith, 2014;Tuda et al, 2014;Nodari & Guerra, 2015).…”

“…Os problemas produzidos por insetos-praga em vegetais têm aumentado significativamente, variando entre 7% e 34% (utilização de inseticidas) e 18% (metodologias alternativas) (Nodari & Guerra, 2015). Tuda et al (2014) descrevem que existe uma coevolução entre as plantas e seus predadores (herbívoros), com um suporte ecológico bem acentuado nessa interação, sendo tais pontos também válidos para a interação entre insetos-praga e sementes.…”

“…No século XIX, foram introduzidos tratamentos com moléculas químicas com diferentes modos de ação e organismos-alvo. Atualmente, tem sido pesquisada muito a utilização dos seguintes controles alternativos: metabólitos secundários vegetais, organismos biocontroladores, indutores de resistência, controle físico e manejo integrado (Tuda et al, 2014;Sharma et al, 2015;Paparella et al, 2015;Yurela, 2015).…”