Abstract:

Research in eco-evolutionary dynamics and community genetics has demon- strated that variation within a species can have strong impacts on associated communities and ecosystem processes. Yet, these studies have centred around individual focal species and at single trophic levels, ignoring the role of phenotypic variation in multiple taxa within an ecosystem. Given the ubi- quitous nature of local adaptation, and thus intraspecific variation, we sought to understand how combinations of intraspecific variation in multiple species within an ecosystem impacts its ecology. Using two species that co-occur and demonstrate adaptation to their natal environments, black cottonwood (Populus trichocarpa) and three-spined stickleback (Gasterosteus aculeatus), we investigated the effects of intraspecific phenotypic variation on both top-down and bottom-up forces using a large-scale aquatic mesocosm experiment. Black cottonwood genotypes exhibit genetic variation in their productivity and consequently their leaf litter subsidies to the aquatic system, which mediates the strength of top-down effects from stickleback on prey abundances. Abundances of four common invertebrate prey species and available phosphorous, the most critically limiting nutrient in freshwater systems, are dictated by the interaction between genetic variation in cotton- wood productivity and stickleback morphology. These interactive effects fit with ecological theory on the relationship between productivity and top- down control and are comparable in strength to the effects of predator addition. Our results illustrate that intraspecific variation, which can evolve rapidly, is an under-appreciated driver of community structure and eco- system function, demonstrating that a multi-trophic perspective is essential to understanding the role of evolution in structuring ecological patterns.

Author affiliation: Rudman, Seth M.. University Of British Columbia; Canadá

Author affiliation: Rodriguez Cabal, Mariano Alberto. University Of British Columbia; Canadá. Universidad Nacional del Comahue; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación en Biodiversidad y Medioambiente; Argentina

Author affiliation: Stier, Adrian. University Of British Columbia; Canadá. Nnational Center for Ecological Analysis and Synthesis; Estados Unidos

Author affiliation: Sato, Takuya . Kobe University. Graduate school of Science. Department of Biology; Japón

Author affiliation: Heavyside, Julian. University Of British Columbia; Canadá

Author affiliation: El Sabaawi, Rana W. . University Of Victoria; Canadá

Author affiliation: Crutsinger, Gregory M. . University Of British Columbia; Canadá

Abstract:

Many host-plants exhibit genetic variation in resistance to pathogens; however, little is known about the extent to which genetic variation in pathogen resistance influences other members of the host-plant community, especially arthropods at higher trophic levels. We addressed this knowledge gap by using a common garden experiment to examine whether genotypes of Populus trichocarpa varied in resistance to a leaf-blistering pathogen, Taphrina sp., and in the density of web-building spiders, the dominant group of predatory arthropods. In addition, we examined whether variation in spider density was explained by variation in the density and size of leaf blisters caused by Taphrina. We found that P. trichocarpa genotypes exhibited strong differences in their resistance to Taphrina and that P. trichocarpa genotypes that were more susceptible to Taphrina supported more web-building spiders, the dominant group of predatory arthropods. We suspect that this result is caused by blisters increasing the availability of suitable habitat for predators, and not due to variation in herbivores because including herbivore density as a covariate did not affect our models. Our study highlights a novel pathway by which genetic variation in pathogen resistance may affect higher trophic levels in arthropod communities.

Author affiliation: Slinn, Heather. University of Nevada; Estados Unidos

Author affiliation: Barbour, Matthew A.. University of British Columbia; Canadá

Author affiliation: Crawford, Kerri. University Of Houston; Estados Unidos

Author affiliation: Rodriguez Cabal, Mariano Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina

Author affiliation: Crutsinger, Gregory M.. Parrot Inc; Estados Unidos

Abstract:

Phenology, or the timing of life cycle events, is a key trait of organisms that has significance for how communities are assembled and ecosystems function. Although variation in phenology in plants has received increased attention over the past decade as a result of changing climate, we are only beginning to understand the role of genetic variation in these phenological traits on ecological interactions and ecosystem-level processes. The influence of tree species on riparian environments presents an interesting system for understanding the effects of phenology in terrestrial species on aquatic ecosystems. Here, we used a dominant riparian tree (Populus trichocarpa: Salicaceae) and tested intraspecific genetic variation in the phenological timing of leaf drop, which influenced leaf-litter inputs into our experimental aquatic ecosystems. Our empirical results found that genotypic differences in P. trichocarpa explained much of the variation both in leaf-litter decomposition and aquatic invertebrate species richness within our experimental ponds. Moreover, our results showed that variation in the timing of leaf-litter inputs outweighed the effects of variation in leaf-litter quality among P. trichocarpa genotypes on aquatic invertebrate species richness. Taken together, our results suggest that genetic variation in the timing of litter inputs from dominant plant species is likely to be a strong underlying mechanism driving litter decomposition and invertebrate communities in aquatic ecosystems. This emphasises that studies disregarding phenology may significantly underestimate an important and variable component in communities and ecosystems.

Author affiliation: Rodriguez Cabal, Mariano Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. University of British Columbia; Canadá

Author affiliation: Barrios Garcia Moar, Maria Noelia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. University of British Columbia; Canadá. Administración de Parques Nacionales. Parque Nacional "Nahuel Huapi"; Argentina

Author affiliation: Rudman, Seth M.. University of British Columbia; Canadá

Author affiliation: McKown, Athena D.. University of British Columbia; Canadá

Author affiliation: Sato, Takuya. Kobe University; Japón

Author affiliation: Crutsinger, Gregory M.. University of British Columbia; Canadá