Size-Dependent Selection on Arrival Times in Sticklebacks: Why Small Males Arrive First

Abstract

Studies on arrival time to breeding areas show that high‐quality males usually arrive first and gain the highest reproductive success. This is generally assumed to be due to phenotype‐dependent costs and benefits of early arrival. We show that the opposite arrival order can occur, probably due to selection on poor‐quality males to increase their chances of reproduction. In a fish species, the threespine stickleback, Gasterosteus aculeatus, small males arrived before larger males at the breeding grounds. Early arrival was costly because predation risk was at its highest at the start of the season and early territory establishment was selected against, as demonstrated by selection coefficients for territory maintenance and hatching success. Large males probably postponed arrival until females were available to decrease predation risk costs and increase offspring production. An experimental study showed that a delay in arrival of large males does not decrease their probability of reproduction, because large males are able to take over nest sites from small males. Small males, on the other hand, are less likely to establish territories in competition with large males but can pay the costs of early arrival in exchange for the benefit of access to territories. Thus, whereas natural selection favors later arrival, sexual selection through competition for breeding territories favors early arrival in small, competitively inferior males. This results in the benefits of early arrival depending on the competitive ability of the male, which favors size‐dependent optimal arrival times.

Fishery‐induced demographic changes in the timing of spawning: consequences for reproductive success*

“…In some areas, herring spawned in discrete waves such that the oldest females in the stock descending to age 4 years spawned in the first wave, while small 4-year olds and age 3 years first-time spawners in the second wave, about 16 days later (Ware and Tanasichuk 1989). The behaviour of older members of a stock may also be important where males are territorial as larger fish are likely to displace younger fish from premium spawning sites (Ridgway et al 1991;Candolin and Voigt 2003). There also seems to be a body size/age component to arrival on spawning grounds such that larger, older, experienced spawners tend to enter sites ahead of first-time spawners and this demographic element is likely to be embodied with environmental driven variation (Ridgway et al 1991;Trippel et al, 1997;Lawson and Rose 2000;Vandeperre and Methven 2007).…”

Priority versus Brute Force: When Should Males Begin Guarding Resources?

“…A "cascading" race to arrive early (Kokko 1999) would then not be observed. Such a strategy has indeed been described for territorial male sticklebacks Gasterosteus aculeatus; large males were found to arrive later than small males because they were able to take over territories on arrival (Candolin and Voigt 2003).…”

Should Attractive Males Sneak: The Trade-Off between Current and Future Offspring

“…The pool experiment showed that in a group of both nesting and non-nesting males, nesting males performed most sneak fertilizations, with attractive males with a high courtship success sneaking the most, but decreasing sneaking in dense vegetation where the success rate of sneak attempts was low. The aquarium experiment revealed that males were more willing to risk their current reproductive success for a sneak opportunity when the perceived value of current offspring was low, but that risk taking increased with male body size, which presumably correlated with future reproductive opportunities [33]. These results suggest that males adjust sneaking to its context-dependent costs and benefits.…”

“…The third possibility, that non-nesting males refrained from sneaking in favor of future nesting opportunities is also plausible, as the intensity of competition for nesting sites varies spatially and temporally under natural conditions [33]. The competitive ability and attractiveness of males could change over the season, particularly as they show indeterminate growth [45].…”

“…Larger males are preferred by females [49] and more successful at establishing territories [33] and should experience a lower cost of sneaking. An alternative explanation is that larger males were more inclined to chase away the neighbor, or to occupy his territory, and therefore visited the border more often.…”