An assessment of the effects of sexual selection and the social environment on mating behaviors in two tiger beetle species (Coleoptera: cicindelidae)
Date
2008-05
Authors
Williams, Clay
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Abstract
Mate guarding is a sexually selected behavior performed by males of many species that results due to sperm competition. Facultative mating behaviors are predicted to occur in these taxa when changes in the social environment alter the benefits for guarding males. I used field observations and lab experiments in 2006 and 2007 to investigate the factors influencing mating behaviors in two tiger beetle species that exhibit mate guarding behavior in central Texas, Cicindela belfragei and C.formosa. Mate guarding and copulation durations were affected by female size, indicating that males may be capable of assessing female size once in physical contact with the female. The social environment of C. belfragei experiments did not affect guarding or copulation durations, but in C formosa, social context was important. In C. formosa, mating behavior durations (guarding and copulation durations) were greatest when only one female was available, but were also longer when non-mating males were in the mating area, compared to when females were abundant.
Size assortative mating and female-biased sexual size dimorphism (SSD) are expected to occur in taxa with post-copulatory mate guarding due to selection for male choice of large females when male time investment is high. Both species displayed female-biased SSD, but size assortative mating did not occur in the field. However, the mean size of mating C. belfragei females collected in the field in 2006 was larger than the mean size of non-mating females, suggesting that large females may have a mating advantage. The results of this study suggest that male choice of large females does not cause the female-biased SSD in these species, assortative mating may not be a characteristic of these species, and that mating behavior durations may not be affected by the extent of mating male harassment by non-mating males or by the outcome of male contests for females. Instead, this study supports previous findings, that Cicindela mating behavior may be determined by other factors, such as the location of oviposition sites and the ability to fly.
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Keywords
tiger beetles, sexual selection, mating, sperm competition
Citation
Williams, C. (2008). An assessment of the effects of sexual selection and the social environment on mating behaviors in two tiger beetle species (Coleoptera: cicindelidae) (Unpublished thesis). Texas State University-San Marcos, San Marcos, Texas.