The stability of ecological communities has important consequences for the functioning of ecosystems, and several different mechanisms have been linked to delivering that stability. It has been shown, for example, that the stability of the species’ populations present within the community, together with the degree of synchrony that exists between them, can influence overall community stability. Larger populations tend to be more stable than smaller populations because they typically have greater genetic diversity and more capacity to adjust to environmental changes through natural selection, while populations situated closer to the middle of their preferred environmental niche tend to be more stable than those located at the margins. This study sought to identify which of these mechanisms was more important.
Using data collected by volunteers participating in three national butterfly monitoring schemes - operating in Spain, the UK and Finland - this paper explores the mechanisms shaping community stability in this familiar group of insects. The researchers use a two-stage approach, first seeking to understand how the underlying species characteristics of the European butterfly assemblage influence population abundance and stability, and then going on to look at how these factors, and their variability, subsequently affect community stability.
The results of the study suggest that measures of the niche characteristics of these butterfly communities can help us to understand differences in both species diversity and population stability at study sites. While the main drivers of community stability were found to vary between the three countries, synchrony was the most consistent factor explaining these differences.
The study highlights that an understanding of the ecological niches of component species can prove informative when considering communities and their stability. In addition to contributing to our theoretical understanding of communities, the work adds to our understanding of the wider causes and consequences of biodiversity loss, and suggests where interventions could be aimed at halting it.
At large scales, the mechanisms underpinning community stability in natural populations may vary in importance due to changes in species composition, mean abundance, and species richness. Here we link species characteristics (niche positions) and community characteristics (richness and abundance) to evaluate the importance of stability mechanisms in 140 butterfly communities across three European countries and spanning five bioclimatic regions. We construct niche-based hierarchical structural Bayesian models to explain first differences in abundance, population stability, and species richness between the countries, and then explore how these factors directly and indirectly (via synchrony and population stability) impact community stability. Species richness was partially explained by the position of a site relative to the niches of the species pool, and species near the centre of their niche had higher average population stability. The differences in mean abundance, population stability, and species richness then influenced how much variation in community stability they explained across the countries. We found, using variance partitioning, that community stability in Finnish communities was most influenced by community abundance, whereas this was unimportant in Spain with species synchrony explaining most variation; the UK was somewhat intermediate with both factors explaining variation. Across all countries, the diversity-stability relationship was indirect with species richness decreasing synchrony which increased community stability, with no direct effects of species richness. Our results suggest that in natural communities, biogeographic variation in key drivers of stability, such as population abundance and species richness, lead to community stability being limited by different factors and that this can partially be explained due to the niche characteristics of the European butterfly assemblage.
Notes
We thank the volunteers collecting butterfly data and the funders of the schemes for the obtaining the data required for this study. The UK Butterfly Monitoring Scheme is organized and funded by Butterfly Conservation, the Centre for Ecology and Hydrology, British Trust for Ornithology, and the Joint Nature Conservation Committee. The Catalan BMS is funded by the Catalan Government, the Barcelona Provincial Council and other local partners. The Catalan BMS also incorporates the Andorra BMS that is run by CENMA and funded by Govern d'Andorra. The Finnish BMS is organized and funded by the Finnish Environment Institute (SYKE) and the Finnish Ministry of Environment.
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