Phylogeographic analyses of theStenopsychecaddisflies (Trichoptera: Stenopsychidae) of the Asian Region

Abstract

Phylogeographic studies based on molecular information have been attracting attention because they have come to play a significant role in the elucidation of the population structure and phylogenetic relationships of species. Furthermore, molecular tools have helped to reveal evidence for cryptic biodiversity, including in many cases the discovery of new species. We focused on the phylogeography of stenopsychid caddisflies. The family Stenopsychidae has a distribution area mainly within the Southern Hemisphere, and only the Stenopsyche caddisflies have spread into parts of the Asian region of the Northern Hemisphere. They inhabit most of the major rivers/streams in Japan at relatively high density and are large and voluminous-bodied species among the benthic animals of Japanese rivers. Therefore, they are considered to be the most important species in the river ecosystem. We conducted phylogenetic analyses for 21 species of the genus Stenopsyche. The results of our genetic analyses inferred from the mitochondrial cytochrome c oxidase subunit I (COI) and nuclear elongation factor (EF)-1a strongly supported the previous morphologically based classification. Stenopsyche species inhabiting southern areas of the Asian region also have been evaluated as being lineages that diverged at a relatively earlier period than the species inhabiting northern areas of Asia. Therefore, a gradual trend has suggested an evolutionary history in which distributional expansion occurred from southern Asia toward northeastern Asia and was accompanied by corresponding species differentiation. Furthermore, newly observed genetically cryptic lineages not yet known to exist were found among the previously described species.

Phylogeography of the northernmost distributed Anisocentropus caddisflies and their comparative genetic structures based on habitat preferences

“…As such their origin may be considered to be Gondwanaland based on their current distribution area and that the Japanese Islands and their surrounding areas correspond to the northern and furthermost distribution limits of this group (Morse, 2020;Nozaki et al, 2016;Saito et al, 2018).…”

“…It is considered that these two caddisfly groups have been strongly influenced by the same geohistorical events since the division of the supercontinent. It was presumed that the caddisflies of Stenopsyche had their highest genetic diversity within the Southeastern Asian region and then speciated as they expanded distribution to the north and into the East Asian region (Saito et al, 2018). Anisocentropus caddisflies are also considered to have originated in the South-East Asian region (node X in Figure 5), similar to Stenopsyche caddisflies.…”

“…It is considered that these differences between the genetic structures of Stenopsyche and Anisocentropus are due to the differences in their habitat preferences. Larvae of Anisocentropus caddisflies prefer leaf litter packs formed from accumulations of submerged fallen leaves in ponds or/and pools within streams (Ito, 2016;Ito et al, 2012), while larvae of Stenopsyche caddisflies prefer riffle environments and gravel riverbeds in flowing water (Saito et al, 2018).…”

Community Structure of Aquatic Insects Adapted to Lentic Water Environments, and Fine-Scale Analyses of Local Population Structures and the Genetic Structures of an Endangered Giant Water Bug Appasus japonicus

“…On the other hand, there were several ponds with a large decrease in density the following spring, despite many A. japonicus inhabitants the previous autumn (i.e., No. 3,6,15,31). These ponds are considered "sinks", like the low-density ponds originally (ponds with low overwintering success rate are likely to be typical "sink" ponds; Figures 7 and 8).…”

“…However, it is very important to identify key areas for their conservation, i.e., clarification of hotspots critical to their survival. In addition, it is also extremely important to accumulate a basic biological understanding of each species at the regional population level (e.g., life cycle, reproduction season, and dispersal ability) [ 14 , 15 ]. The relationship between their population structure and their genetic structure is also of great importance [ 16 , 17 , 18 ].…”