No abstract

Ecosystem function is the outcome of species interactions, traits, and niche overlap - all of which are influenced by evolution. However, it is not well understood how the tempo and mode of niche evolution can influence ecosystem function. In evolutionary models where either species differences accumulate through random drift in a single trait or species differences accumulate through divergent selection among close relatives, we should expect that ecosystem function is strongly related to diversity. However, when strong selection causes species to converge on specific niches or when novel traits that directly affect function evolve in some clades but not others, the relationship between diversity and ecosystem function might not be very strong. We test these ideas using a field experiment that established plant mixtures with differing phylogenetic diversities and we measured ten different community functions. We show that some functions were strongly predicted by species richness and mean pairwise phylogenetic distance (MPD, a measure of phylogenetic diversity), including biomass production and the reduction of herbivore and pathogen damage in polyculture, while other functions had weaker (litter production and structural complexity) or nonsignificant relationships (e.g., flower production and arthropod abundance) with MPD and richness. However, these divergent results can be explained by different models of niche evolution. These results show that diversity-ecosystem function relationships are the product of evolution, but that the nature of how evolution influences ecosystem function is complex.

1.Ecologists are increasingly involved in city-making, especially in the development of green infrastructure and other designed plant communities. 2. Plant communities that are more phylogenetically related are more similar in functional traits and adaptations to their environment than distant relatives. 3. Knowledge of how evolutionary relationships among plant species influence ecosystem functions could be applied to green infrastructure to improve benefits such as urban cooling, habitat creation and stormwater management. 4. The intended outcomes of manipulations of phylogenetic diversity (PD) may vary depending on project goals, particularly when considering the trade-offs between multiple ecosystem functions. For instance, constraining PD could improve survival and performance in stressful environments or short growing seasons. Increasing PD could improve habitat diversity, aesthetics and other direct human benefits. 5. Synthesis and applications. Given the potential benefits of considering phylogenetic relationships of plant communities in green infrastructure, we recommend that ecologists work with landscape architects and other design professionals to test how ecophylogeneticsthe application of phylogenies in ecologymight aid in achieving desired outcomes for green infrastructure.

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.