Departement für Biologie / Abt. Ökologie und Evolution
Elze Hesse
“Life history variation and population dynamics of natural Veratrum
album populations”
Most animal and plant species occur in a wide range of habitats exhibiting substantial variation in
demographic rates. A fundamental question in evolutionary ecology is how such variation affects life
history evolution and fitness. Comparing intra-specific variation among natural populations provides an
excellent opportunity to examine the selective forces involved in life history evolution. However, such
comparative demographic tests of theory are rare because they require long-term monitoring of
multiple populations. Monocarpic plants are ideal systems for testing evolutionary ideas because the
cost of reproduction is easily quantified and the timing of flowering is a key determinant of fitness.
Whilst we are beginning to understand the evolutionary dynamics of monocarps, little is known about
how selection varies among habitats. This thesis addresses this issue by exploring the dynamics of
natural Veratrum album (Liliales, Melanthiaceae) populations in contrasting habitats (i.e. forest,
meadow and pasture). Veratrum is a clonal perennial herb with monocarpic ramet and is endemic to a
wide range of alpine habitats throughout Eurasia, where it can form dense infestations. To develop
suitable population management strategies, knowledge about the contribution of life history traits to
population growth rate is essential. Data on seed bank formation, seedling establishment and ramet
demography collected in fifteen natural populations were used to parameterize a series of integral
projection models. These models were used to explore the effects of habitat-induced demographic
variation, pre-dispersal seed predation and restoring traditional management on the finite rate of
increase (  ), net reproductive rate ( R0 ) and generation time (T). Using the evolutionary stable
strategy (ESS) approach, we then predict the flowering strategy – the relationship between the
probability of flowering and plant size. This thesis clearly demonstrates that in light of growing
concerns about correctly identifying sensitive life stages in nuisance populations, intra-specific
variation in demographic rates and life history traits can not be ignored. Moreover, in an evolutionary
perspective, habitat is an important aspect of the selective environment in Veratrum populations and is
a significant factor in predicting ESS flowering strategies.
Jury:
Prof. Heinz Müller-Schärer, Dissertationsleiter
Pro. Mark Rees, externer Gutachter
Dr. Tadeusz Kawecki, Gutachter
Prof. Fritz Müller, Jurypräsident