Sympatric speciation in Yponomeuta: no evidence for host plant fidelity

Abstract

According to sympatric speciation theory, adaptation to different host plants is expected to pleiotropically lead to assortative mating, an important factor in the reduction of gene flow between the diverging subpopulations. This scenario predicts mating on and oviposition preference for the respective hosts in both the diverging subpopulations and recently originated species. Here, we test both predictions in the oligophagous Yponomeuta padellus (L.) and the monophagous Yponomeuta cagnagellus (Hübner) (Lepidoptera: Yponomeutidae), two closely related small ermine moth species from the western European clade of Yponomeuta for which speciation in sympatry has been proposed. Mating location and adult host acceptance were evaluated under both semi-field (in a large outdoor cage with a choice of host and non-host plants) and field conditions. In the semi-field experiment, only Y. cagnagellus showed some preference for mating on its own host (16% of all mating pairs) over non-host plants (3% of all mating pairs). However, in both species, more than 80% of the mating pairs were not formed on a plant but instead on the cage itself. Further examination of the mating site of Y. cagnagellus in the field revealed no preference for host plants over non-host plants in the two consecutive years of observation. Yponomeuta padellus females, collected from and reared on Prunus spinosa L. (Rosaceae), showed an oviposition preference for the alternative host Crataegus monogyna Jacq. (Rosaceae) in the semi-field experiment. We thus found no evidence that host-plant fidelity (in terms of mating site) has been the driving force in the speciation process of these Yponomeuta species, nor did we find evidence of host race formation in the tested population of the oligophagous Y. padellus .

Alpha taxonomy of the genus Kessleria Nowicki, 1864, revisited in light of DNA-barcoding (Lepidoptera, Yponomeutidae)

“…All these taxa are extremely similar in external and internal morphology. This is a phenomenon well known from the related genus Yponomeuta , namely the Yponomeuta cagnagellus species-complex which includes morphologically virtually indistinguishable species (Bakker et al 2008), which furthermore often share DNA barcodes. Evolution and reproductive isolation in this genus was likely driven by specific host-plant associations and sex pheromones (Menken 1981, Menken et al 1992, Menken 1996, Löfstedt 1991, Turner et al 2010).…”

Ecological speciation in phytophagous insects

“…Thus, it appears that habitat isolation may be a common form of reproductive isolation in phytophagous insects. Although habitat isolation is the most commonly reported form of reproductive isolation in herbivorous insects (Table 1), we note that this pattern is likely influenced by a strong bias towards studying this form of isolation [see Bakker et al. (2008) for an example of a lack of host fidelity].…”

Impacts of climate warming on hybrid zone movement: Geographically diffuse and biologically porous “species borders”

“…There was no indication that host affiliations of the specialized or oligophagous Yponomeuta species had any impact on mating preferences between host races (Bakker et al , 2008). Changes in the insect nervous system that functionally change plant recognition and host plant specificity may represent autonomous evolutionary events, and as such may be intrinsic to the genome (and not evoked by ecological selection, Jermy, 1993).…”