Colonization ability of two invasive weevils with different reproductive modes

The flightless weevils Naupactus leucoloma and Naupactu xanthographus (Coleoptera: Curculionidae: Naupactini), which are native to and partially co-distributed in South America, apparently have asexual and bisexual reproductive modes, respectively. We used two different molecular markers to elucidate the effects of these reproductive modes on the colonization ability and genetic variability of both species. First, we investigated the occurrence of clonal reproduction in the putative parthenogenetic species (i.e. significant bias in sex ratio) and second, whether parthenogenesis was associated with higher colonization ability and low levels of genetic variability in marginal environments compared with those of the bisexual species. We assessed the central and marginal areas of distribution of these species with ecological niche modeling that includes environmental variables and with landscape interpolation of molecular variability. Our results support the idea that parthenogenetic species are more successful than bisexual ones in colonizing new environments. N. leucoloma is most probably apomictic, and would have recently experienced significant population growth concomitant with an important geographic range expansion to distant areas with moderately suitable environmental conditions. On the other hand, the populations of the bisexual species, N. xanthographus, seem to have maintained fairly constant sizes, expanding its geographic distribution to locations close to the proposed ancestral area.