SP 4: Plant genetics

Genetics of trees and shrubs in the BEF-Experiment, and their relevance for fitness and the biodiversity-ecosystem functioning relationship

Principal investigator(s):

Co-Principal investigator(s):

Phd candidate(s):

Contact adress:

Department Community Ecology, Helmholtz-Centre for Environmental Research-UFZ, Theodor-Lieser-Str. 4, D-06120 Halle (Saale), Germany

Institute of Plant Sciences, University of Bern, Altenbergrain 21, CH-3013 Bern, Switzerland

Summary

Species diversity, genetic diversity of the compound species and ecosystem function may be mutually interrelated. This project addresses this issue using several approaches. First, we hypothesize that genetic variation of quantitative traits determines the performance increasingly with increasing levels of species diversity. For that purpose we analyze species whose individuals are well characterized genetically (e.g. by provenance or seed family). Additionally, we use seed families (half-sib progeny) of a limited number of tree and shrub species that are planted in the overall design. In these plants adaptive, quantitative traits like stem height, growth or phenology, and their phenotypic variation and broad sense heritability are measured and related to plant performance. Secondly, we hypothesize, that genetic diversity is a response variable, specifically that provenances and seed families may respond differently to species diversity because of varying selection. Thus, effects of species diversity may result in genotype x species diversity interactions which are analyzed with phytometer plants of one species that are planted into all plots. Thirdly, we test the hypothesis that species diversity and genetic variation are correlated. We use molecular markers to quantify level and structure of genetic variation across diversity and successional gradients for a considerable number of species within natural communities and relate species and genetic diversity. Furthermore, we hypothesize that increasing species richness, via reduced population density, reduces the amount on gene flow and thus leads to reduced pollen flow distances and more pronounced small scale genetic structure within populations. The Chinese twin-project will use the same plant material and focus on ecophysiological parameters (e.g. photosynthesis, transpiration) in the analysis of phenotypic variation and heritability of quantitative traits in the nursery and main experiment.

Objectives

This subproject addresses both the role of genetic variation as a determinant of plant performance and genetic variation as response variable that is affected by species diversity.

• (1) We test the hypothesis that plant performance (e.g. growth, survival, reproduction, pathogen resistance) is positively correlated to genetic variation in these traits and that this correlation becomes more pronounced with increasing species diversity, i.e. interspecific competition.
• (2) We test whether different levels of species diversity exert different selection pressures on different provenances and seed families.
• (3) We test the hypothesis that in natural communities species diversity is related to genetic diversity within component species due to the action of neutral processes like dispersal or density-dependent gene flow.
• (4) We use the Comparative Study Plots to test the hypothesis that increasing species richness leads to i) reduced pollen flow and a decrease in the number of pollen donors fathering offspring in a target plant, resulting in reduced levels of outcrossing, ii) increased genetic differentiation at small scale (i.e. within plots), resulting in a more pronounced genetic structure.