Institut für Evolution und Ökologie

Theme 3: Morphological variability in plants growing along steep and subtle environmental gradients - an evolutionary test of the stress gradient hypothesis

Bettina Springer
(K. Tielbörger, Co-supervisor: K. Harter)

In this subproject, we will test two primary hypotheses:

  1. The stress gradient hypothesis (SGH, see e.g. Bertness & Callaway 1994) applies independent of the intensity of stress and independent of species, i.e. positive interactions dominate stressful environments and vice-versa.
  2. Morphological variability is a good indicator for stress, i.e. plants become more asymmetric as stress increases and this is a phenotypic response to stress.


As case studies we use
a) an extreme gradient of aridity in Israel (see e.g. Holzapfel et al. 2004),
b) a less extreme gradient of nutrient availability and water availability in Germany (Swabian Alb), and possibly
c) a gradient of increasing temperature stress (frost) in the Bavarian Alps.


For the first two gradients, we have data on fitness response and morphological response of dominant plants species to increasing levels of resource limitation. Additional field work designed to evaluate symmetry (leaves and flowers) of most component species along the gradients and evaluation of variability of symmetry within populations allows to test the above hypotheses. The molecular basis of floral symmetry will then be evaluated in project no. 2. We predict decreasing asymmetry with increasing stress and increased symmetry within populations with neighbors under stressful conditions and vice-versa. Local adaptation to stress will be evaluated in a series of common garden experiments and via cross-transplants.

Key words: fluctuating asymmetry, stress gradient hypothesis, facilitation, competition

Literature