Explaining ecosystem multifunction with evolutionary models

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

Plant Species\u27 Origin Predicts Dominance and Response to Nutrient Enrichment and Herbivores in Global Grasslands

Exotic species dominate many communities; however the functional significance of species\u27 biogeographic origin remains highly contentious. This debate is fuelled in part by the lack of globally replicated, systematic data assessing the relationship between species provenance, function and response to perturbations. We examined the abundance of native and exotic plant species at 64 grasslands in 13 countries, and at a subset of the sites we experimentally tested native and exotic species responses to two fundamental drivers of invasion, mineral nutrient supplies and vertebrate herbivory. Exotic species are six times more likely to dominate communities than native species. Furthermore, while experimental nutrient addition increases the cover and richness of exotic species, nutrients decrease native diversity and cover. Native and exotic species also differ in their response to vertebrate consumer exclusion. These results suggest that species origin has functional significance, and that eutrophication will lead to increased exotic dominance in grasslands

Plant species' origin predicts dominance and response to nutrient enrichment and herbivores in global grasslands

Exotic species dominate many communities; however the functional significance of species’ biogeographic origin remains highly contentious. This debate is fuelled in part by the lack of globally replicated, systematic data assessing the relationship between species provenance, function and response to perturbations. We examined the abundance of native and exotic plant species at 64 grasslands in 13 countries, and at a subset of the sites we experimentally tested native and exotic species responses to two fundamental drivers of invasion, mineral nutrient supplies and vertebrate herbivory. Exotic species are six times more likely to dominate communities than native species. Furthermore, while experimental nutrient addition increases the cover and richness of exotic species, nutrients decrease native diversity and cover. Native and exotic species also differ in their response to vertebrate consumer exclusion. These results suggest that species origin has functional significance, and that eutrophication will lead to increased exotic dominance in grasslands

Brassica tournefortii: Phenology, Interactions and Management of an Invasive Mustard

ABSTRACT OF THE DISSERTATIONBrassica tournefortii: Phenology, Interactions and Management of an Invasive Mustardby Robin Gene Marushia Doctor of Philosophy, Graduate Program in Plant Biology University of California, Riverside, June 2009 Dr. Jodie S. Holt, Chairperson Brassica tournefortii (Gouan), or Sahara mustard, is a nonnative, invasive annual forb currently invading the deserts of North America. Despite its increasing distribution and dominance in desert plant communities, little is known about the biology or impacts of B. tournefortii, and few options exist for management. This dissertation sought to answer three basic questions. First, this dissertation questioned "Why is B. tournefortii able to invade desert ecosystems, whereas closely-related invasive mustards are not?" Four biotypes of invasive Brassicaceae, including desert and more mesic populations of B. tournefortii, Brassica nigra, and Hirschfeldia incana were grown with climate and watering treatments over three years. Results show that all biotypes are capable of equal fitness under desert and drought conditions. Although no differences were found between mesic and desert populations of B. tournefortii, the species had a more rapid phenology than its congeners, suggesting that B. tournefortii succeeds because it can reproduce quickly. Second, this dissertation asks, "What are the interactions of B. tournefortii with native annual forbs?" Because native annuals fill a similar ecological niche, I hypothesized that B. tournefortii would have negative impacts on natives with increasing density and cover. Success of the plant community and individual native species was correlated to B. tournefortii dominance. Results show that B. tournefortii has mostly negative interactions with natives with high precipitation, but positive relationships with low precipitation, suggesting that interactions of B. tournefortii with natives change from negative to positive based on resource availability. Finally, this dissertation asks, "Can B. tournefortii be selectively managed in desert ecosystems?" This research compared hand-weeding, a common control technique, to an emergence-stage application and rosette-stage application of glyphosate, vs. no treatment. Emergence-stage application was hypothesized to selectively control B. tournefortii and other invasives by taking advantage of their non-specific germination requirements and rapid emergence. This hypothesis was supported by results showing that native cover can be maintained by applying herbicide at emergence while reducing exotic cover. Hand-weeding selectively removed B. tournefortii, but promoted annual cover and richness only underneath shrubs at a site with few other invasives present. Late herbicide produced high mortality in all species. Results suggest that herbicide can be used as a selective technique to remove most desert invasives, not just B. tournefortii. In conclusion, B. tournefortii is a unique case study for biological invasions in extreme ecosystems, and presents challenges for ecologists and land managers alike

Plant species’ origin predicts dominance and response to nutrient enrichment and herbivores in global grasslands

Exotic species dominate many communities; however the functional significance of species' biogeographic origin remains highly contentious. This debate is fuelled in part by the lack of globally replicated, systematic data assessing the relationship between species provenance, function and response to perturbations. We examined the abundance of native and exotic plant species at 64 grasslands in 13 countries, and at a subset of the sites we experimentally tested native and exotic species responses to two fundamental drivers of invasion, mineral nutrient supplies and vertebrate herbivory. Exotic species are six times more likely to dominate communities than native species. Furthermore, while experimental nutrient addition increases the cover and richness of exotic species, nutrients decrease native diversity and cover. Native and exotic species also differ in their response to vertebrate consumer exclusion. These results suggest that species origin has functional significance, and that eutrophication will lead to increased exotic dominance in grasslands.This article is published as Seabloom, E., Borer, E., Buckley, Y. et al. Plant species’ origin predicts dominance and response to nutrient enrichment and herbivores in global grasslands. Nat Commun 6, 7710 (2015). doi:10.1038/ncomms8710. Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted

Plant species’ origin predicts dominance and response to nutrient enrichment and herbivores in global grasslands

Exotic species dominate many communities; however the functional significance of species’ biogeographic origin remains highly contentious. This debate is fuelled in part by the lack of globally replicated, systematic data assessing the relationship between species provenance, function and response to perturbations. We examined the abundance of native and exotic plant species at 64 grasslands in 13 countries, and at a subset of the sites we experimentally tested native and exotic species responses to two fundamental drivers of invasion, mineral nutrient supplies and vertebrate herbivory. Exotic species are six times more likely to dominate communities than native species. Furthermore, while experimental nutrient addition increases the cover and richness of exotic species, nutrients decrease native diversity and cover. Native and exotic species also differ in their response to vertebrate consumer exclusion. These results suggest that species origin has functional significance, and that eutrophication will lead to increased exotic dominance in grasslands