Evolutionary aspects of host plant specialisation – a study on bruchids (Coleoptera: Bruchidae)

Abstract

We have studied the relationship of bruchids and their legume hosts by extensive field sampling throughout Hungary over 17 years and by rearing the beetles from the samples in the laboratory. The value of the system lies in the accuracy of host affiliations. A total of 138 species and subspecies of plants were sampled, representing approximately 87% of the Leguminosae in Hungary. Only 51 legume species (37.0%) harboured bruchids (12 Bruchus spp. and 15 Bruchidius spp). Bruchids occurred in 38.3% of the host plant samples. Thirty‐seven plant species congeneric with bruchid host species were unoccupied by bruchids. The degree of host specificity ranged from monophagy (at least ecological monophagy) to oligophagy. On the basis of presence/absence data we tested the null hypothesis assuming that plant taxa and seed consuming bruchid species form congruent phyletic relations at the species level. We argue that the case for coevolution between the beetles and their hosts is weak. A comparison of the available taxonomic relationships (and presumed phylogenies) best fits a case of sequential evolution, with stronger phylogenetic conservatism in Bruchus species than in Bruchidius species. Bruchid and host plant taxa showed rough congruence only at the tribe level. We suggest that host shifts are best explained by the changes in the bruchids’ chemosensory system that determines the females’ host selection behaviour.

Macroevolution and the biological diversity of plants and herbivores

“…The more common pattern appears to be that of sequential evolution (103,104): the associations have arisen by ''colonization'' from one plant lineage to another, usually related and therefore chemically similar. The radiation of insect clades associated with specific plant clades shows a degree of temporal correspondence.…”

Selection for chemical trait remixing in an invasive weed after reassociation with a coevolved specialist

“…Accordingly, some skepticism remains as to the efficacy of herbivores as selective agents (6), and alternative explanations, including top-down selection from natural enemies of herbivores, have proliferated (albeit also without an abundance of experimental demonstrations). In addition to its importance in a theoretical context, quantifying selection and rates of response is critical for evaluating the stability of host-plant resistance traits in agricultural crops as well as the sustainability of classical biocontrol of weeds.…”

Global legume diversity assessment: Concepts, key indicators, and strategies

“…Food webs of the legume-bruchine system have been studied in various geographic areas (Johnson, 1981a;Udayagiri & Wadhi, 1989;Kergoat & al., 2007a); Asia (Chujo, 1937;Arora, 1977;Tuda & al., 2005Tuda & al., , 2006, the Middle East (Johnson & al., 2004), Europe (Hoffmann, 1945;Jermy & Szentesi, 2003;Delobel & Delobel, 2006;Kergoat & al., 2007b), Africa (Johnson & al., 2004;Kergoat & al., 2005), Russia (Luk'yanovich & Ter-Minasyan, 1957) and the New World (North and Central America, Johnson, 1970Johnson, , 1983Kingsolver, 2004;Kato & al., 2010;South America, Johnson, 1990). Native bruchines are absent in arctic areas and Pacific islands and scarce in Australia (Borowiec, 1987).…”