Different phylogeographic patterns in two Japanese Silpha species (Coleoptera: Silphidae) affected by climatic gradients and topography

Abstract

To reveal differences in phylogeographic patterns of flightless insect species occurring in different regions of Japan, we studied the phylogeography and demographic history of Silpha beetles occurring in cool-temperate habitats of two major islands, Honshu and Hokkaido, using sequences of the mitochondrial cytochrome oxidase subunit I (COI) gene. Honshu has a more mountainous topography, and cool-temperate habitats occur discontinuously, whereas Hokkaido, located to the north of Honshu, has more continuous cool-temperate habitats. A species endemic to Honshu, S. longicornis occurs on Honshu, whereas S. perforata occurs on Hokkaido and the East Asian continent.Our results indicate that the ancestors of S. longicornis colonized Honshu via a south-west route c. 0.7 Mya and the species has highly divergent populations in isolated mountainous areas of Honshu, whereas S. perforata colonized Hokkaido via a northern route less than 90 000 years ago and has less divergent geographic populations. During the last glacial period, S. perforata was probably restricted to refugia in southern Hokkaido and later expanded into northern Hokkaido, whereas S. longicornis populations existed in many isolated refugia, probably because of the complex topography of Honshu. Thus, our study demonstrates that, even between closely related species, interactions among biology, latitudinal climatic gradients and topography can produce different phylogeographic patterns.

Spermatophore expulsion in the carrion beetle Silpha perforata (Coleoptera: Silphidae)

“…Meanwhile, flight ability is not important in searching for invertebrates that are abundant on and in soil. Ikeda et al . (2009) discussed that the change in feeding habitats had gone ahead, and then flight ability was lost in derivative species.…”

“…In Silphidae, feeding habitat and flight ability are different among species. Molecular phylogeny indicates that flying species that feed on vertebrate carcasses are ancestral, and flightless species that feed mainly on soil invertebrates are derivative (Ikeda et al 2009). Since it is unpredictable when and where vertebrate carcasses appear, flying beetles have advantages in resource competition.…”

“…Meanwhile, flight ability is not important in searching for invertebrates that are abundant on and in soil. Ikeda et al (2009) discussed that the change in feeding habitats had gone ahead, and then flight ability was lost in derivative species. It is possible that change in feeding habitat would also influence the evolution of reproductive strategy, although there is little information on mating behavior of beetles belonging to the subfamily Silphinae.…”

“…However, there is little information about the life history of this taxon. Silpha perforata inhabits the forests and grasslands throughout East Asia (Ikeda et al . 2009).…”

“…However, there is little information about the life history of this taxon. Silpha perforata inhabits the forests and grasslands throughout East Asia (Ikeda et al 2009). Stable isotope ratios indicate that soil invertebrates are their primary prey, although they occasionally feed on vertebrate carcasses (Ikeda et al 2007).…”