Novel Consumer Impacts on Alpine Grassland Plants Across Elevational Gradients

Changes in climatic conditions affect plants as well as their consumers and thereby reshape the strength and outcome of biotic interactions. Furthermore, climate change may also create novel interactions between plants, herbivores, and pathogens as species shift their latitudinal or elevational ranges at different rates. These novel-plant-consumer interactions remain largely unstudied but likely have consequences for plant populations, community dynamics, and ecosystem functioning. Particularly in alpine ecosystems, where climatic conditions vary strongly due to steep environmental gradients.

In order to address this knowledge gap, we conducted a large-scale transplant experiment with nine focal alpine plant species across an elevational gradient. The species were selected based on their growth strategy as well as their altitudinal distribution range, including low and high-elevation species, as well as herbs, grasses, and legumes. We planted our focal species in higher, lower, or home elevations to expose them to different consumer communities and to simulate current and future climates in the European Alps over the next century. By combining these transplants with insect, mollusk, and pathogen exclusion experiments, we isolate and disentangle the impacts of home and novel consumer groups on plant fitness. Additionally, we conducted vegetation surveys of the surrounding plant community to assess the effects of diversity and community composition on consumer impacts.

We hypothesize that low-elevation consumers, which are accustomed to warmer and more productive systems, will exert stronger negative effects on plants than high-elevation consumers. Further, we anticipate high-elevation plant species to be more negatively affected by low-elevation consumers. When focal plants are grown in communities, we expect consumer effects to vary with similarity of phytometer and community growth strategy, and that disregarding these interactions could underestimate climate change impacts.

Here, we present first results from this experiment, providing new insights into the role of biotic interactions in shaping alpine plant responses to warming. Furthermore, we show how neighboring community growth strategy and biodiversity modify consumer effects on focal species. Our research will improve predictions of alpine community dynamics under future climate scenarios.