Distribution and Differentiation ofHenosepilachna diekei(Coleoptera: Coccinellidae) on Two Host-Plant Species Across Java, Indonesia

Abstract

Divergent natural selection on different host plants may be a crucial factor in promoting the remarkable diversity of phytophagous insects, and might occur in any geographical context. Because the intensity and consequences of divergent selection on different hosts can vary depending on the degree of gene flow between conspecific insect populations, elucidating the geographical context and degree of host specificity in the incipient phase of differential host use is indispensable to understanding the diversification process in phytophagous insects. Henosepilachna diekei Jadwiszczak & Węgrzynowicz (Coleoptera: Coccinellidae) is a tropical ladybird beetle occurring mainly on two host species from different plant families, Asteraceae and Lamiaceae. We investigated the geographical distribution of H. diekei across Java, Indonesia, in relation to the availability of the two hosts, and examined the host specificity of beetles in the laboratory. We also investigated genetic relationships among local populations of beetles using mitochondrial NADH dehydrogenase subunit 2 gene sequences. Geographic variation in host use by H. diekei was largely determined by skewed geographical distributions of the hosts, although there was a synergistic effect with extremely divergent host specificity by the beetles. The molecular analyses suggested that genetic differentiation among the beetle populations has occurred and has been maintained by the effects of both geographical distance and divergent host specificity. The geographical distribution of H. diekei populations differing in host specificity suggests that geographical distance, local host-plant availability, and divergent host specificity contribute synergistically to promote the genetic differentiation and subsequent diversification of phytophagous insects on different hosts.

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

“…, ,b; Fujiyama et al . ). This outcome reveals the unexpectedly strong impact of divergent host use on the speciation process from the initial stage of population divergence to nearly final stage, in which almost all gene flow is restricted.…”

“…The sympatry of the two host races are known only in West Java, and only one of these two host races is distributed within other parts of Java Island (Fujiyama et al . ; Matsubayashi et al . ,b).…”

“…These host races co‐occur only in the western parts of Java Island (Fujiyama et al . ; Matsubayashi et al . ,b).…”

“…; Fujiyama et al . ), these results were based on one, two or a few specific localities in the sympatric area; additionally, a detailed estimate of gene flow between host races has not yet been reported.…”

“…The host race depending on M. micrantha ( Mikania race) widely distributes over all the distribution range of this species; in contrast, the distribution of the host race depending on L. lavandulifolia ( Leucas race) is limited in Java Island, Indonesia (Fujiyama et al . ; Matsubayashi et al . 2016a,b).…”