Divergent host plant preference causes assortative mating between sympatric host races of the ladybird beetle,Henosepilachna diekei

Abstract

Divergent host preference (i.e. host fidelity) plays a significant role in the speciation process in phytophagous insects. However, how and to what extent this divergence reduces gene flow between populations has rarely been measured. Here, we estimated the intensity of assortative mating caused solely by host fidelity in two host races of the phytophagous ladybird beetle Henosepilachna diekei, specialized on Mikania micrantha (Asteraceae) and Leucas lavandulifolia (Lamiaceae) in West Java, Indonesia. These host races mated randomly in the absence of host plants under laboratory conditions, but demonstrated nearly complete assortative mating in field cages with the two host plants, by spending almost all of their time on their respective host plants. The frequency of assortative mating in the field cages was not affected drastically by host plant patch structure. These results suggest that fidelity to the different host plants yields directly almost complete reproductive isolation between the host races by limiting the habitat on the respective host plant. In addition, the high host fidelity also ensures female oviposition on the original host plant. As larvae cannot survive on non-host plants, a positive association between female oviposition preference and larval performance on the host plant on which the beetles are specialized will further facilitate the evolution of host fidelity.

Revisiting the particular role of host shifts in initiating insect speciation

“…Genetic comparisons using the mitochondrial gene NADH dehydrogenase subunit 2 and the nuclear gene ITS2 demonstrate genetic differentiation between populations found on each plant host (Matsubayashi et al. ). In addition, there is strong evidence that reproductive barriers related to host plant use restrict gene flow between host‐associated populations.…”

“…H. diekei females exhibit host plant fidelity and preferentially oviposit on their natal hosts, resulting in strong habitat isolation between populations (Matsubayashi et al. ). Under laboratory conditions, H. diekei larvae preferentially fed on their natal host and larval survivorship decreased on the alternative host plant (Matsubayashi et al.…”

“…In the absence of all host plants, inter‐ and intrapopulation matings occur at similar frequencies (Matsubayashi et al. ) indicating a lack of precopulatory sexual isolation between groups. However, the introduction of one or both host plants to the mating experiments results in a significant decrease in interpopulation matings, suggesting that host association plays an important role in mate selection for H. diekei populations (Matsubayashi et al.…”

Molecular Population Structure ofJunoniaButterflies from French Guiana, Guadeloupe, and Martinique

“…"nigrosuffusa" (taxonomic affinities uncertain) appear to establish mating territories in the interdune and slack areas between the sand dunes. It is not clear whether these North American Junonia habitat preferences are due to preferences for abiotic conditions of the microhabitat itself or whether the presence or relative abundance of preferred larval host plants for each form in the favoured microhabitats is the driver of habitat preference [123]. In French Guiana, the presence of different Junonia taxa appears to be closely tied to the abundance and phenology of larval host plants [23].…”

Extremely divergent host plant acceptance with gene flow between sympatric host races of the phytophagous ladybird beetle Henosepilachna diekei

“…Marking–recapture experiments undertaken using field cages indicated the critical contribution of adult host preference to different host plants to determine the mating site and the oviposition site of these host races (Matsubayashi et al . ). A previous mitochondrial DNA analysis revealed significant genetic divergence between the host races sampled at two sympatric sites (Matsubayashi et al .…”