Unexpected female preference for smaller males in the marbled goby Pomatoschistus marmoratus.

The study tested the role of body size and of nest size in female mate choice in the marbled goby, Pomatoschistus marmoratus. The results show a female preference for smaller males, supporting the idea that smaller males may be preferred to larger ones in the absence of male-male competition. No effect of nest size was detected, suggesting that other nest characteristics, beyond nest size, may be implicated.

Spatial asymmetry of the paternity success in nests of a fish with alternative reproductive tactics.

Guard-sneaker tactics are widespread among fish, where territorial males defend a nest and provide parental care while sneakers try to steal fertilizations. Territorials and sneakers adopt diverse pre- and post-mating strategies, adjusting their ejaculate investment and/or behavioural responses to the presence of competitors. The relative distance of competitors from the spawning female plays a major role in influencing male mating strategies and the resulting paternity share. However, territorial male quality and sneaking intensity do not fully account for the variability in the relative siring success occurring among species. An often neglected factor potentially affecting sneakers proximity to females is the nest structure. We conducted a field experiment using the black goby, whose nests show two openings of different size. We found that territorial males defend more and sneaking pressure is higher at the front, larger access of the nest than at the back, smaller one. Moreover, microsatellite paternity analysis shows that territorials sire more offspring at the back of their nest. Such a predictable spatial distribution of the paternity share suggests that nest structure might work as an indirect cue of male relative siring success, potentially influencing the territorial male investment in parental care and/or the female egg deposition strategy.

Life on the edge: adaptation versus environmentally mediated gene flow in the snow buttercup, Ranunculus adoneus.

We used experimental transplant studies to understand how dispersal and habitat-specific selection interact to influence plant populations occupying heterogeneous environments. The snow buttercup (Ranunculus adoneus) occupies a steep ecological and flowering time gradient caused by persistent snowmelt differences within its snow bed habitat. We transplanted seeds, seedlings, and adults to learn about the potential interactions between dispersal and selection. We found that adaptive differentiation is not occurring along the snowmelt gradient, despite striking differences in microhabitat conditions and reproductive phenology between early- and latemelting sites. Instead, our results imply that environmentally based differences in seed quality are contributing to directional gene flow from early-melting locations toward latemelting locations. Emergence and early survival of seedlings is greater in late-melting sites in some years, but the larger seeds produced by maternal plants in early-melting locations consistently have a fitness advantage in all parts of the snow bed. Larger seeds survive longer in the soil and have a second peak of seedling emergence in their third year, but these late-emerging seedlings are successful only if dispersed to less vegetated, late-melting destinations. The longer growing season in earlymelting sites enhances vegetative growth at all life-history stages and increases fecundity of seedling transplants but also limits the opportunity for establishment from seed. Our demographic analysis suggests that maternal environmental effects on propagule quality can lead to directional gene flow from benign to marginal sites in populations occupying heterogeneous habitats.