A team of Japanese researchers has successfully demonstrated that loss of flight has been the major driving force for beetle diversification.
Carrion beetles: winged species Necrophila brunnicollis at left and wingless species Silpha longicornis at right (Insects.jp / Shuhei Nomura)
Insects are an enormously species-rich group representing more than half of all described species. One of the most important events for the insect diversification is the acquisition of flight, occurred about 400 million years ago.
Flight ability facilitates the search and colonization of distant habitats, wide dispersal, and the ability to find mates and food. However, many insect species have lost their ability to fly by losing flight muscles and wings.
Prof. Teiji Sota of the Kyoto University and his team tested the hypothesis that the loss of flight promotes allopatric speciation and leads to the high species richness in Coleoptera using carrion beetles as a model system.
Allopatric speciation occurs when biological populations of the same species become isolated due to geographical changes.
“To test our hypothesis that the loss of flight promotes allopatric speciation and leads to higher species richness, we addressed, in detail, the causal relationship between flight loss and diversification using carrion beetles, two lineages of which (in the subfamily Silphinae) lost their flight ability due to evolutionary shifts in feeding habit,” the team wrote in the paper, published on Jan. 31 in Nature Communications.
The researchers compared the geographical differentiation patterns and flight abilities of eight silphine species, widely distributed throughout the Japanese archipelago, using population genetic approaches.
The finding reveals that flightless species retain higher genetic differentiation among populations and comprise a higher number of genetically distinct lineages than flight-capable species, indicating high possibility for allopatric speciation.
To verify that the pattern shown in carrion beetles is common among different beetle families, the team conducted a meta-analysis of the molecular variances among and within populations in the mitochondrial COI-II gene, using data of 51 species from 15 coleopteran families.
“A meta-analysis reveals higher genetic differentiation among populations in flightless compared with flight-capable species,” the team concluded.
“In beetles, which represent almost one-fourth of all described species, repeated evolution of flightlessness may have contributed to their steady diversification since the Mesozoic era.”
