Role of parasite load and differential habitat preferences in maintaining the coexistence of sexual and asexual competitors in fish of theCobitis taeniahybrid complex

Abstract

In the context of the paradoxical ubiquity of sex, we tested whether stable coexistence of sexual and asexual fish of the genus Cobitis is mediated by parasites, as asexual fish suffer more from parasitic infections because of their lower genetic variability [the Red Queen hypothesis (RQH)], or by partial niche shift of the two strains differing in mode of reproduction. We did not find a clear correlation between infection risk with a helminth parasite and the proportion of sexuals, and we found similar infection rates among sexual females and co-occurring asexuals in general, including the most frequent clone in particular. These results suggest that the mechanisms of the RQH are not directly engaged in stabilizing this asexual complex. On the other hand, the temporally stable gradient in sexual/asexual proportions along the river correlated with gradients in environmental parameters (physicochemical water parameters, velocity, and shading of the habitat) and turnover in the fish assemblage structure. Sexual and asexual forms thus appear to prefer different habitats. The Cobitis teania asexual complex thus contributes to the view that persistence of sex may, as in many taxa, be driven by case-specific processes.

Growth differences in different biotypes of the hybrid complex of Cobitis elongatoides × Cobitis tanaitica (Actinopterygii: Cypriniformes: Cobitidae) in the Okna River (Danube River basin), Slovakia

“…All these findings support the opinion that the two different forms (diploid and polyploid) representing different reproductive strategies and may differ in ecological niche utilisation (Kotusz et al 2014).…”

“…The diploid-polyploid ratio of Cobitis from Lake Müggelsee (Germany), however, at 1 : 7.4, is considered extreme, sex ratio 1 : 22 in favour of females (Bohlen and Ritterbusch 2000). According to Kotusz et al (2014), the diploid-polyploid ratio in Cobitis population has remained relatively stable for around a decade, though the male-female ratio varies with age in the majority of populations (Soriguer et al 2000, Patimar et al 2011, Mousavi Sabet et al 2011, 2012, Kırankaya and Ekmekçi 2014. As such, the survival rate differs between the sexes (Aoyama 2007, Juchno and Boroń 2010) and between individuals of different ploidies (Bobyrev et al 2003).…”

“…Within the genus Cobitis, strains with different ploidy display high morphological similarity (Kotusz 2008), though they clearly differ in physiological and ecological performance, including metabolic rate (Maciak et al 2011), body condition, and habitat preference (Kotusz et al 2014), and length of spawning period and oocyte size (Juchno et al 2007). All these findings support the opinion that the two different forms (diploid and polyploid) representing different reproductive strategies and may differ in ecological niche utilisation (Kotusz et al 2014).…”

Parthenogenetic vs. sexual reproduction in oribatid mite communities

“…It therefore predicts sexual taxa to dominate in habitats where parasite-host and/ or predator-prey interactions control community dynamics (Hamilton, 1980;Jaenike, 1978), which is often the case when predators/ parasites reach high densities (Ladle, 1992). A number of field and laboratory studies supported the RQT (Gibson & Fuentes, 2015;Haafke, Chakra, & Becks, 2016;Kotusz et al, 2014), but many are based on a single parasite-host system, the snail Potamogyrgus antipodarum and its trematode parasite (Jokela, Dybdahl, & Lively, 2009;King, Delph, Jokela, & Lively, 2009;Lively, 2010). A number of field and laboratory studies supported the RQT (Gibson & Fuentes, 2015;Haafke, Chakra, & Becks, 2016;Kotusz et al, 2014), but many are based on a single parasite-host system, the snail Potamogyrgus antipodarum and its trematode parasite (Jokela, Dybdahl, & Lively, 2009;King, Delph, Jokela, & Lively, 2009;Lively, 2010).…”

Parasitic infection of Cobitis elongatoides Băcescu & Mayer, 1969 by zoonotic metacercariae Clinostomum complanatum (Rudolphi, 1814)

“…An earlier study, however, did not record any impact of Cobitis spp. ploidy on the intensity of infection (Kotusz et al, ). Out of the statistical results, the presence of triploid (12) and tetraploid females (1) that we recorded was characterized by higher mean water depth (80 cm), contrary to diploid specimens (50 cm), which is probably linked to a preferable depth of feeding herons (McKilligan, ).…”