The role of herbivory in the macroevolution of vertebrate hormone dynamics.

Vertebrates have high species-level variation in circulating hormone concentrations, and the functional significance of this variation is largely unknown. We tested the hypothesis that interspecific differences in hormone concentrations are partially driven by plant consumption, based on the prediction that herbivores should have higher basal hormone levels to 'outcompete' plant endocrine disruptors. We compared levels of glucocorticoids (GCs), the hormones with the most available data, across 166 species. Using phylogenetically informed comparisons, we found that herbivores had higher GC levels than carnivores. Furthermore, we found that the previously described negative relationship between GC levels and body mass only held in herbivores, not carnivores, and that the effect of diet was greatest at extreme body sizes. These findings demonstrate the far-reaching effects of diet on animal physiology, and provide evidence that herbivory influences circulating hormone concentrations. We urge future direct testing of the relationship between phytochemical load and GC levels.

No evidence for environmental filtering of cavity-nesting solitary bees and wasps by urbanization using trap nests.

Spatial patterns in biodiversity are used to establish conservation priorities and ecosystem management plans. The environmental filtering of communities along urbanization gradients has been used to explain biodiversity patterns but demonstrating filtering requires precise statistical tests to link suboptimal environments at one end of a gradient to lower population sizes via ecological traits. Here, we employ a three-part framework on observational community data to test: (I) for trait clustering (i.e., phenotypic similarities among co-occurring species) by comparing trait diversity to null expectations, (II) if trait clustering is correlated with an urbanization graient, and (III) if species' traits relate to environmental conditions. If all criteria are met, then there is evidence that urbanization is filtering communities based on their traits. We use a community of 46 solitary cavity-nesting bee and wasp species sampled across Toronto, a large metropolitan city, over 3 years to test these hypotheses. None of the criteria were met, so we did not have evidence for environmental filtering. We do show that certain ecological traits influence which species perform well in urban environments. For example, cellophane bees (Hylaeus: Colletidae) secrete their own nesting material and were overrepresented in urban areas, while native leafcutting bees (Megachile: Megachilidae) were most common in greener areas. For wasps, prey preference was important, with aphid-collecting (Psenulus and Passaloecus: Crabronidae) and generalist spider-collecting (Trypoxylon: Crabronidae) wasps overrepresented in urban areas and caterpillar- and beetle-collecting wasps (Euodynerus and Symmorphus: Vespidae, respectively) overrepresented in greener areas. We emphasize that changes in the prevalence of different traits across urban gradients without corresponding changes in trait diversity with urbanization do not constitute environmental filtering. By applying this rigorous framework, future studies can test whether urbanization filters other nesting guilds (i.e., ground-nesting bees and wasps) or larger communities consisting of entire taxonomic groups.

Manipulating plant phylogenetic diversity for green roof ecosystem service delivery.

Plant species and functional trait diversity have each been shown to improve green roof services. Species and trait differences that contribute to ecosystem services are the product of past evolutionary change and phylogenetic diversity (PD), which quantifies the relatedness among species within a community. In this study, we present an experimental framework to assess the contribution of plant community PD for green roof ecosystem service delivery, and data from one season that support our hypotheses that PD would be positively correlated with two services: building cooling and rainwater management. Using 28 plant species in 12 families, we created six community combinations with different levels of PD. Each of these communities was replicated at eight green roofs along an elevation gradient, as well as a ground level control. We found that the minimum and mean roof temperature decreased with increasing PD in the plant community. Increasing PD also led to an increase in the volume of rainwater captured, but not the proportion of water lost via evapotranspiration 48 hr following the rain event. Our findings suggest that considering these evolutionary relationships could improve functioning of green infrastructure and we recommend that understanding how to make PD (and other measures of diversity) serviceable for plant selection by practitioners will improve the effectiveness of design and ecosystem service delivery. Lastly, since no two green roof sites are the same and can vary tremendously in microclimate conditions, our study illustrates the importance of including multiple independent sites in studies of green roof performance.