Flynn, D. F. B. | bioRxiv Science

bioRxiv2018

On the importance of accounting for intraspecific genomic relatedness in multi-species studies

1. Analyses in many fields of ecology are increasingly considering multiple species and multiple individuals per species. Premises of statistical tests are often violated with such datasets because of the non-independence of residuals due to phylogenetic relationships or intraspecific population structure. Comparative approaches that account for the phylogenetic relationship of species--for which the benefits are demonstrated--are well developed. However, the importance of accounting for the intraspecific genetic structure, especially with the phylogenetic structure, is rarely addressed in the ecological literature.\n\n2. We investigated whether it is beneficial to account for intraspecific genomic relatedness in multi-species studies. For this, we used a Phylogenetic Mixed Model to analyze simulated data and results from a budburst experiment where clippings of 10 tree and shrub species were subjected to different treatments in terms of temperature and photoperiod.\n\n3. We found that accounting for intraspecific genomic relatedness yields more accurate and precise fixed effects as well as increased statistical power, but more so when the relative importance of the intraspecific to the phylogenetic genetic structure is greater. Analysis of the budburst experiment further showed that accounting for intraspecific and phylogenetic structures yields improved estimates of warming and photoperiod effects and their interactions in explaining the time to budburst.\n\n4. Our results show that important statistical gains can be made by incorporating information on the intraspecific genomic relatedness of individuals in multi-species studies. This is relevant for investigations that are interested in intraspecific variation and that plan to include such observations in statistical tests.

ecology↗

bioRxiv2017

Community selection increases biodiversity effects

Species extinctions from local communities can negatively affect ecosystem functioning. Ecological mechanisms underlying these impacts are well studied but the role of evolutionary processes is rarely assessed. Using a long-term field experiment, we tested whether natural selection in plant communities increased the effects of biodiversity on productivity. We re-assembled communities with 8-year co-selection history adjacent to communities with identical species composition but no history of co-selection (\"naive communities\"). Monocultures and in particular mixtures of two to four co-selected species were more productive than their corresponding naive communities over four years in soils with or without co-selected microbial communities. At the highest diversity level of eight plant species, no such differences were observed. Our findings suggest that plant community evolution can lead to rapid increases in ecosystem functioning at low diversity but may take longer at high diversity. This effect was not modified by treatments that simulated additional co-evolutionary processes between plants and soil organisms.

ecology↗