Abstract
It is known that females from native populations of the multicoloured Asian ladybird, Harmonia axyridis, have a strong photoperiodic response (enter reproductive diapause under short photoperiods), whereas the proportion of diapausing females from invasive populations is less dependent on day length. The aim of the present study was to determine the mode of inheritance of these differences. The experiments were conducted with two laboratory populations of H. axyridis, the High Diapause (HD) population originated from Irkutsk (Southern Siberia, ca 52.3°N, 104.3°E) and the Low Diapause (LD) population originated from Sochi (North Caucasus, ca 43.6°N, 39.6°E). Reciprocal first generation hybrids and reciprocal backcrosses were investigated. Under a strong diapause-inducing photoperiod (12 h) 100% of the females from the HD population and about 70% of those from the LD population entered diapause. First generation hybrids, as well as their backcrosses with individuals from the HD population, showed almost 100% diapause. Among the backcrosses with the LD population the percentage of diapausing females was widely variable (70-100%) but close to the average between the two populations. The comparison of reciprocal crosses did not reveal any significant difference. We conclude that photoperiodic induction of diapause in the populations of H. axyridis studied is most probably determined by several genes (although one of them evidently plays a leading role with diapause being dominant over non-diapause) and that male and female genotypes are equally important in the determination of female reproductive diapause.
Highlights
Diapause is an important component of insect life history crucial for surviving harsh seasonal conditions and for synchronizing reproduction and development with favorable environments (Tauber et al, 1986)
The females of Siberian and Korean native populations have a clear photoperiodic response, whereas the percentage of females entering diapause in European and Caucasian invasive populations is less dependent on day length (Reznik et al, 2015a). These results indicate that there are genetic differences in the photoperiodic responses of individuals in native and invasive populations of H. axyridis the mode of inheritance of which is unknown
Similar to that recorded in this study, diapause is dominant in the linden bug, Pyrrhocoris apterus L. (Dolezel et al, 2005), Drosophila littoralis Meigen (Lumme et al, 1975) and two Tetranychus species (Ignatowicz & Helle, 1986; Takafuji & Goka, 1999)
Summary
Diapause is an important component of insect life history crucial for surviving harsh seasonal conditions and for synchronizing reproduction and development with favorable environments (Tauber et al, 1986). It is well established that photoperiodic, thermal, trophic and other diapauseregulating responses are well adapted to local climate and may differ between species and between geographically distant populations of the same species (Denlinger, 2002; Saunders et al, 2002; Saunders, 2010; Goto & Numata, 2014) This intra-specific variability has been thoroughly investigated in several model insects (Lumme et al, 1975; Henrich & Denlinger, 1983; Kim et al, 1995; McWatters & Saunders, 1997; Doležel et al, 2005; Williams et al, 2006; Goto, 2009; Han & Denlinger, 2009) and in some other, mostly economically important, Coleoptera (Sakakibara & Kawakami, 1992; Kuang et al, 2011; Chen et al, 2012, 2014; French et al, 2014; Lehmann et al, 2016; Tanaka & Murata, 2016), Lepidoptera (Ikten et al, 2011; Söderlind & Nylin, 2011; Xia et al, 2012; Huang et al, 2013; Fu et al, 2015; Xiao et al, 2015; Pruisscher et al, 2017), Diptera (Meuti et al, 2015), Hymenoptera (Paolucci et al, 2016) and spider mites (Ignatowicz & Helle, 1986; Takafuji & Goka, 1999; Suwa & Gotoh, 2006; Kawakami et al, 2010). The inheritance of diapause-controlling reactions is considered an important area of investigation for furthering the under-
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