A novel method of comparing mating success and survival reveals similar sexual and viability selection for mobility traits in female tree crickets

Abstract

The relationship between sexual and viability selection in females is necessarily different than that in males, as investment in sexual traits potentially comes at the expense of both fecundity and survival. Accordingly, females do not usually invest in sexually selected traits. However, direct benefits obtained from mating, such as nuptial gifts, may encourage competition among females and subsidize investment into sexually selected traits. We compared sexual and viability selection on female tree crickets Oecanthus nigricornis, a species where females mate frequently to obtain nuptial gifts and sexual selection on females is likely. If male choice determines female mating success in this species, we expect sexual selection for fecundity traits, as males of many species prefer more fecund females. Alternatively, intrasexual scramble or combat competition on females may select for larger jumping legs or wider heads (respectively). We estimated mating success in wild caught crickets using microsatellite analysis of stored sperm and estimated relative viability by comparing surviving female O. nigricornis to those captured by a common wasp predator. In support of the scramble competition hypothesis, we found sexual selection for females with larger hind legs and narrower heads. We also found stabilizing viability selection for intermediate head width and hind leg size. As predicted, traits under viability and sexual selection were very similar, and the direction of that selection was not opposing. However, because the shape of sexual and viability selection differs, these episodes of selection may favour slightly different trait sizes.

Sex differences in survival: viability selection in nymphal tree crickets from a conopid fly parasitoid

“…There is also evidence of sexual selection for larger females (perhaps competing for access to gifts) as large females are more likely to pursue males resulting in them acquiring more matings than small females (Brown, 2008). Consistent with these behavioural findings, selection analyses of field populations detected sexual selection on body size in both males and females (Ercit & Gwynne, 2015, 2016. In insects, larger females are also more fecund, which results in selection for larger body size (reviewed in Bonduriansky, 2001).…”

“…These regressions were done separately for males and female tree crickets as there was an interaction between sex and body size in the main model. The sexes have also been found to be under different selection pressures as adults by Ercit and Gwynne (2015, 2016). The selection analyses were repeated using fitness scored as presence or absence of fly eggs and/or larvae.…”

“…Sex and size biases in mortality of tree crickets Oecanthus nigricornis Walker (Gryllidae) occur when they are captured, paralysed, and hauled off to a nest by a parasitoid wasp Isodontia mexicana Saussure (Sphecidae). The wasps target more females than males (O'Neill & O'Neill, 2003; Ercit, 2014) and certain sized cricket prey are more vulnerable; selection analyses revealed greater survival of males with narrower heads, larger legs and intermediate body size, and of females with intermediate body size and longer legs (Ercit & Gwynne, 2015, 2016).…”

Intrasexually selected weapons

“…Eens & Pinxten, 2000;Andersson, 2005;Simmons, 2005), it is still unclear why jacanas are the only sex-role reversed group in which female ISWs have been reported (Davison, 1985;Berglund, 2013). One explanation is that there is a deficit of detailed morphological and behavioural studies focusing on the detection of potential ISWs in sexually reversed species (see Robson & Gwynne, 2010;Ercit & Gwynne, 2016; see Section III.7 for female ISW prospects in birds). It is also possible that since sex-role reversal is relatively rare in nature, there have not been sufficient evolutionary scenarios for the appearance of 'reversed ISWs'.…”

Therapeutic advances in hormone-dependent cancers: focus on prostate, breast and ovarian cancers

“…The addition of antiangiogenic therapy to single-agent cytotoxic chemotherapy has been shown to improve response rates and PFS (124) (Supplementary Table 3). PARPi has also been shown to be of benefit to patients with germline or somatic mutations in BRCA and represents a well-tolerated option in eligible patients (125). Tamoxifen, letrozole, fulvestrant and angiogenesis inhibitors have also been evaluated for use in the platinum-resistant setting with responses similar or worse than cytotoxic chemotherapy (126, 127, 128, 129, 130).…”