Macroscale evolutionary patterns of flight muscle dimorphism in the carrion beetle Necrophila japonica

Abstract

Some insect species exhibit polymorphisms in flight muscles or wings, which provide opportunities for studying the factors that drive dispersal polymorphisms and the evolution of flightlessness in insects. We investigated the macroscale evolutionary pattern of flightlessness in the widespread Japanese beetle Necrophila japonica (Coleoptera: Silphidae), which exhibits flight muscle dimorphisms using phylogeographic approaches. N. japonica lives in both stable and unstable habitats, and the flight muscle dimorphisms may have been maintained through the use of these diverse habitats. We studied the distribution pattern of the proportion of individuals lacking flight muscles in relation to the genetic differentiation among geographic populations using an 842-base pair sequence of the COI-II gene. Both flight-capable and flightless individuals occurred over the distribution area, and the flight muscle condition showed no significant phylogeographic pattern. Several populations comprised flight-capable individuals only, whereas few comprised flightless ones only. Demographic expansion was suggested for major clades of COI-II haplotypes, and the genetic differentiation showed an isolation-by-distance pattern among the populations in Japan. The proportion of flightless individuals was higher in a population with a higher annual mean temperature and with higher genetic diversity among individuals. These results indicate that geographic expansion occurred recently while flight muscle dimorphisms have been maintained, that flight-capable individuals have colonized cooler (peripheral) habitats, and that flightlessness has increased in long-persisting populations as suggested by high genetic diversity.

Loss of flight promotes beetle diversification

“…The applicability of the threshold time was significantly supported in both models ( P <0.001). In N. japonica , both individuals with and without flight muscles occurred within the same populations 1750. The values in parentheses in the GMYC approach are corrected for overestimation.…”

Speciation: Don't Fly and Diversify?

“…Flight-incapable populations in these species are constrained in their dispersal capability just as permanently flightless species are. However, at least in the case of N. japonica, their genetic population structure did not differ from fully flighted species (Figure 1) [15]. Flight polymorphism provides a more flexible strategy to respond to environmental changes, as long-term survival of lineages may benefit from occasional long-distance dispersal while generally avoiding the associated risk of displacement when habitat conditions are stable [16].…”

Spatial Variation in Body Size and Wing Dimorphism Correlates With Environmental Conditions in the Grasshopper Dichroplus vittatus (Orthoptera: Acrididae)

“…The relative contribution of genetic and environmental components can vary among different genetic systems and factors that affect adaptation Denno 1997, Ikeda andSota 2011). Thus, the different flight ability can be maintained in heterogeneous spatiotemporal conditions based on the particular trade-off between dispersal capability and reproduction in each biological model (Roff and Fiarbairn 1991, Zera and Denno 1997, Roff et al 1999, Fox and Czesak 2000, Jonsson 2003.…”