Multiple paternity and sperm competition in the sibling species Drosophila buzzatii and Drosophila koepferae

Abstract

Sperm competition (SC) is a major component of sexual selection that enhances intra- and intersexual conflicts and may trigger rapid adaptive evolution of sexual characters. The actual role of SC on rapid evolution, however, is poorly understood. Besides, the relative contribution of distinctive features of the mating system to among species variation in the strength of SC remains unclear. Here, we assessed the strength of SC and mating system factors that may account for it in the closely related species Drosophila buzzatii and Drosophila koepferae. Our analyses reveal higher incidence of multiple paternity and SC risk in D. buzzatii wild-inseminated females. The estimated number of fathers per brood was 3.57 in D. buzzatii and 1.95 in D. koepferae. In turn, the expected proportion of females inseminated by more than one male was 0.89 in D. buzzatii and 0.58 in D. koepferae. Laboratory experiments show that this pattern may be accounted for by the faster rate of stored sperm usage observed in D. koepferae and by the greater female remating rate exhibited by D. buzzatii. We also found that the male reproductive cost of SC is also higher in D. buzzatii. After a female mated with a second male, first-mating male fertility was reduced by 71.4% in D. buzzatii and only 33.3% in D. koepferae. Therefore, we may conclude that postmating sexual selection via SC is a stronger evolutionary force in D. buzzatii than in its sibling.

Polyandry and postcopulatory sexual selection in a wild population

“…; Hurtado et al . ; Smith ). Further studies of natural mating rates and differential sperm use across additional species and taxa would shed more light on the prevalence of postcopulatory selection and its role in driving evolution.…”

Sperm displacement in the Drosophila bipectinata species complex: Evidence for interspecific variations

“…Similar kind of pattern was also demonstrated in three sibling species of Drosophila (D. melanogaster, D. mauritiana and D. simulans) where P2 values were found to be almost similar in all three ranging from 0.79 to 0.88 showing last male sperm precedence (Manier et al, 2013). But it is not necessary that the sibling species or closely related species would show similar trend of sperm displacement as in the case of Drosophila koepferae and Drosophila buzzatii where D. buzzatii females exhibit strong sperm competition (P2 is 0.89) and D. koepferae showing weak sperm displacement (P2 is 0.58) (Hurtado et al, 2013). This might be due to difference in female remating rate and sperm usage pattern between the two species.…”

Modeling strategic sperm allocation: Tailoring the predictions to the species

“…Based on the available data on minimum female mating frequencies in the field, which has been gathered for species of Drosophila (Frentiu and Chenoweth ; Hurtado et al. ), dung flies (Demont et al. ), crickets (Bretman and Tregenza ; Simmons and Beveridge ; Turnell and Shaw ), katydids (Simmons et al.…”

“…; Frentiu and Chenoweth ; Simmons and Beveridge ; Hurtado et al. ; Smith ; Turnell and Shaw ). Another major class of models, the intensity model (Parker et al.…”

“…Risk models (e.g., Parker 1990a,b) assume that females mate with a maximum of two males, generating a certain level of risk that the ejaculate of the focal male will compete with one other ejaculate. However, in most species, many females mate with more than two males under natural conditions (for a global analysis see Taylor et al 2014; for examples see Emery et al 2001;Bretman and Tregenza 2005;Simmons et al 2007;Frentiu and Chenoweth 2008;Simmons and Beveridge 2010;Hurtado et al 2013;Smith 2014;Turnell and Shaw 2015b). Another major class of models, the intensity model (Parker et al 1996;Ball and Parker 1997), assumes that males can assess the number of total competitors they will face postcopulation.…”