Seasonal variation in male alternative reproductive tactics

Abstract

Genetic parentage analyses reveal considerable diversity in alternative reproductive behaviours (e.g. sneaking) in many taxa. However, little is known about whether these behaviours vary seasonally and between populations. Here, we investigate seasonal variation in male reproductive behaviours in a population of two-spotted gobies (Gobiusculus flavescens) in Norway. Male two-spotted gobies guard nests, attract females and care for fertilized eggs. We collected clutches and nest-guarding males early and late in the breeding season in artificial nests and used microsatellite markers to reconstruct parentage from a subset of offspring from each nest. We hypothesized that mating, reproductive success and sneaking should be more prevalent early in the breeding season when competition for mates among males is predicted to be higher. However, parentage analyses revealed similar values of mating, reproductive success and high frequencies of successful sneaking early (30% of nests) and late (27% of nests) in the season. We also found that multiple females with eggs in the same nest were fertilized by one or more sneaker males, indicating that some males in this population engage in a satellite strategy. We contrast our results to previous work that demonstrates low levels of cuckoldry in a population in Sweden. Our results demonstrate marked stability in both the genetic mating system and male alternative reproductive tactics over the breeding season. However, sneaking rates may vary geographically within a species, likely due to local selection influencing ecological factors encountered at different locations.

Sex roles and sexual selection: lessons from a dynamic model system

“…This seems to be the case, as artificial PVC nest tubes introduced to the breeding habitat are usually quickly occupied (K. de Jong, unpublished data). Artificial nests have also had high occupancy rates in other populations (W Norway, Monroe et al. 2016 , Mid-Norway: T. Amundsen and S. Wacker, unpublished data).…”

“…Thus, successful males in Norwegian and Swedish study populations mate with a median of 4–5 females ( Figure 5a ; Mobley et al. 2009 ; Monroe et al. 2016 ).…”

“…2004 ) or collected (e.g., Mobley et al. 2009 ; Monroe et al. 2016 ), for instance for quantification of reproductive success, egg parameters, and parentage.…”

“…Additionally, studies (especially on alternative reproductive tactics and parental care; e.g., Skolbekken and Utne-Palm 2001 ; Utne-Palm et al. 2015 ; Monroe et al. 2016 ) have been made on a population on the West coast of Norway, from a base at Espeland Marine Biological Station (60°16′11″ N, 5°13′19″ E, Figure 4 ).…”

“…Mussel nests are often full or near-full with such numbers of clutches ( Mobley et al. 2009 ; Monroe et al. 2016 ).…”