Relative effects of local and regional factors as drivers for plant community diversity, functional trait diversity and genetic structure of species on Baltic uplift islands
Final Report Abstract
The dramatic loss of biodiversity across ecosystems and the decline in associated ecosystem functioning is an important ecological challenge requiring a deeper understanding of the mechanisms driving different components of biodiversity, such as composition, structure, and function at different levels of organismic organization, i.e. genes, species and landscapes. Although we know that both local factors (e.g. habitat size, abiotic conditions) and regional factors (e.g. landscape structure and configuration) drive local species diversity, only few empirical studies in real landscapes evaluated mechanisms at various spatial scales in a comparative approach. As another important facet of biodiversity, landscape genetics extends the neutral population genetic model and tries to understand how landscape structure and environmental factors shape the genetic structure of species. However, despite its appeal to both basic and applied questions, only a small proportion of landscape genetic studies deal with plants. In the current project, we have analysed the effects of local and regional factors on different aspects of species diversity of plant communities and on the genetic structure of selected plant species on islands in three archipelagos in the Baltic Sea. We selected continental land uplift islands, a relatively simple type of ancient cultural landscape, since these (i) present a suitable study system to address the relative role of local and regional factors, (ii) the basic driving forces are well described by the theory of island biogeography, and (iii) there is a lack of studies on species diversity, landscape ecology/genetics but even studies addressing basic population genetic hypotheses. Vegetation composition and species diversity depended more on local variables than on landscape configuration. Especially soil fertility and soil morphology had strong effects on vegetation composition and species diversity. The proportion of unexplained variance was habitat-specific, possibly reflecting a community maturity gradient with larger impacts of random processes along shore habitats. Our results stress the need of including habitat-based approaches when analysing species-environment relationships on islands. Concerning species dispersal among island, geese play an important role since they disperse large amounts of diaspores of many terrestrial island plant species. They act as a filter for species assembly since geese select species with certain suites of traits from the regional species pool. The relative importance of geese as dispersal vectors may increase under ongoing land-use changes and cessation of grazing networks. Genomic population structure of plant species in the Blekinge archipelago was species specific with strong population differentiation and isolation-by-distance in Allium schoenoprasum. Here, spatially coherent gene pools are reflect the spatial structure of coastline and island groups. In contrast, Lotus corniculatus, Galium verum and Potentilla anserina showed very low differentiation without pronounced spatial patterns, indicating that in these grassland species human management enhanced gene flow among islands. Finally, the grass Phalaris arundinacea showed weak differentiation with IBD. On the large scale, Phalaris showed distance dependent differentiation among the three archipelagos suggesting that the species maintains a gene flow drift – equilibrium across various scales. Species-genetic diversity correlations (SGDC), i.e. correlations between genomic variation and species richness, were found both for three of the five investigated species and for a composite multi species diversity estimate. This indicates that both species richness and genetic variation are affected by common external drivers. Because also island area and grassland management were related to genetic variation, further analyses are necessary to disentangling the importance of individual causal factors.
Publications
- 2018. New insights into island vegetation composition and species diversity - Consistent and conditional responses across contrasting insular habitats at the plot-scale. PLoS One 13: e0200191
Hattermann D., Bernhardt-Römermann M., Otte A. & Eckstein R.L.
(See online at https://doi.org/10.1371/journal.pone.0200191) - 2019. Geese are overlooked dispersal vectors for vascular plants in archipelago environments. Journal of Vegetation Science
Hattermann D., Bernhardt-Römermann M., Otte A. & Eckstein R.L.
(See online at https://doi.org/10.1111/jvs.12742)
