Selective recruitment for pollen and nectar sources in honeybees

Honeybees (Apis mellifera) use cues and signals to recruit nestmates to profitable food sources. Here we investigate whether the type of resource advertised within the colony (i.e., pollen or nectar) correlates with the recruits’ choices at the feeding site. We observed that pollen recruits preferred to collect pollen once arrived for the first time at the feeding site, while nectar recruits preferred to forage sucrose solutions. Bees recruited by foragers carrying both resources show intermediate preferences. Studying the plasticity of this response, we found that nectar recruits have a low probability of switching to pollen collection, yet pollen recruits were likely to switch to sucrose solution of increasing concentrations. Our results show that cues associated with the advertised resource type correlate with recruits foraging tendency for pollen and sucrose solution, a feature that would guarantee an efficient resource collection.

How macroecology affects macroevolution: the interplay between extinction intensity and trait-dependent extinction in brachiopods

Selection is the force behind differences in fitness, with extinction being the most extreme example of selection. Modern experiments and observations have shown that average fitness and selection strength can vary over time and space. This begs the question: as average fitness increases, does selection strength increase or decrease? The fossil record illustrates how extinction rates have varied through time, with periods of both rapid and slow species turnover. Using Paleozoic brachiopods as a study system, I developed a model to understand how the average taxon duration (i.e. fitness) varies over time, to estimate trait-based differences in taxon durations (i.e. selection), and to measure the amount of correlation between taxon fitness and selection. I find evidence for when extinction intensity increases, selection strength on geographic range also increases. I also find strong evidence for a non-linear relationship between environmental preference for epicontinental versus open-ocean environments and expected taxon duration, where taxa with intermediate preferences are expected to have greater durations than environmental specialists. Finally, I find that taxa which appear more frequently in epicontinental environments will have a greater expected duration than those taxa which prefer open-ocean environments. My analysis supports the conclusions that as extinction intensity increases and average fitness decreases, as happens during a mass extinction, the trait-associated differences in fitness would increase. In contrast, during periods of low extinction intensity when fitness is greater than average, my model predicts that selection associated with geographic range and environmental preference would decrease and be less than average.

Negative frequency-dependent preferences and variation in male facial hair

Negative frequency-dependent sexual selection maintains striking polymorphisms in secondary sexual traits in several animal species. Here, we test whether frequency of beardedness modulates perceived attractiveness of men's facial hair, a secondary sexual trait subject to considerable cultural variation. We first showed participants a suite of faces, within which we manipulated the frequency of beard thicknesses and then measured preferences for four standard levels of beardedness. Women and men judged heavy stubble and full beards more attractive when presented in treatments where beards were rare than when they were common, with intermediate preferences when intermediate frequencies of beardedness were presented. Likewise, clean-shaven faces were least attractive when clean-shaven faces were most common and more attractive when rare. This pattern in preferences is consistent with negative frequency-dependent selection.