Clone Diversity in the Polyploid Weevil Otiorhynchus Scaber

Abstract

Parthenogenetic insects are in general polyploid. These polyploid parthenogenetic forms seem to be superior competitors compared to their diploid and sexual relatives. Numerous studies have shown a surprisingly high clonal diversity in parthenogeinetic insects. We have studied Otiorhynchus scaiber, a common flightless weevil. O. scaber consists of three forms: one diploid sexually reproducing form with a very limited distribution and two widely distributed polyploid parthenogenetic forms. All forms, diploids and polyploids, coexist within the central area of distribution where both genetic and clonal diversity are highest. Diversity and degree of ploidy decrease towards the margin of distribution, so that only tetraploids inhabit the margins. This geographical pattern of distribution is a common phenomenon in parthenogenetic animals with different ploidy levels. We suggest that the high clonal diversity in populations of O. scaber is due to a continuous transition from diploid sexuality to triploid and finally to tetraploid parthenogenesis. We propose that the transition is caused by chance fertilisations of unreduced eggs.

Clonal Diversity of Otiorhynchus ligustici and O. raucus (Coleoptera, Curculionidae) in Central Ukraine

“…In our case, we have a reason to predict the allotriploid genetic constitution of the both species examined. A similar genetic constitution is found (Suomalainen, Saura, 1973;Stenberg et al, 2000) Note. Abbreviations see table 1. in a vertebrate hybrid form, where allotriplody caused the alternative reproduction mode (gynogenesis) (Stenberg et al, 1997;Quattro et al, 1992).…”

“…Th e genus Otiorhynchus Germar, 1822 includes 1288 species belonging in 113 subgenera in the Palaearctic Region (Magnano, Alonso-Zarazaga, 2013). Th e population genetic structure has been studied by far only in the Western European species O. scaber (Suomalainen, Saura, 1973;Stenberg et al, 2000;Stenberg et al, 2003). Th e genetic structures of other Otiorhynchus species populations inhabiting Eastern Europe have not been analyzed yet.…”

New data on the cytology of parthenogenetic weevils (Coleoptera, Curculionidae)

“…This phenomenon is called geographic parthenogenesis. One example is the European Otiorhynchus scaber, which has tetraploid, triploid, and diploid bisexual races (Suomalainen et al 1987;Stenberg et al 2000). The presence of diploid males of Otiorynchus raucus in a population from Slovakia could be explained by geographic parthenogenesis, but in this case both lineages occur together.…”

“…It is assumed that triploid weevils may originate when the process of oogenesis is disturbed and a diploid gamete is formed. The union of this diploid ovum with a haploid sperm produces a triploid embryo (Stenberg et al 2000). Transition of ploidy is caused by chance fertilization of unreduced eggs.…”

The Evolution of Unisexuality in Calligrapha Leaf Beetles: Molecular and Ecological Insights on Multiple Origins via Interspecific Hybridization

“…However, in other taxa, including insects, empirical evidence for this mechanism is rare. To date, introgressive hybridization has only been compellingly linked to unisexual origins in four insect genera: the stick insect Bacillus (Mantovani et al 2001), the grasshopper Warramaba (Honeycutt and Wilkinson 1989), Rhopalosiphum aphids , and the weevil Otiorhynchus (Tomiuk and Loeschcke 1992;Stenberg et al 2000). In some other organisms, such as Aramigus weevils (Normark and Lanteri 1998), this mechanism is suspected but not entirely confirmed.…”