I have always been puzzled by how plants perceive their environment and respond to it. Especially I am interested in interactions between plants and their mutualistic or antagonistic partners such as pollinators, seed predators, herbivores, mycorrhizae, and parasitoids. For my MSc project, I focused on plant defences against herbivory. During my PhD I started to look at the relative importance of herbivory (more precisely frugivory) and pollination for plant fitness. Now I am exploring how pollination and frugivory could contribute to selection on particular floral traits.

Since the beginning of my PhD thesis, I have been working with the white campion, Silene latifolia (Caryophyllaceae), a short-lived perennial plant with separate sexes. I combined controlled greenhouse experiments with common garden experiments, and laboratory work to investigate which factors and traits affected the receipt of pollen, and how variation in these traits influenced male, female and offspring fitness. At the individual flower level, we used molecular markers to investigate male fitness, and microscopy to observe changes in the female reproductive structures. We found a significant effect of the timing of pollen arrival from two males on their relative paternity success, and on the individual seed mass of their offspring, but no significant effect on seed set. We observed a significant paternity advantage of the first male before pollen tubes reached the ovary and flower wilting. At the inflorescence (plant) level, post-pollination wilting of flowers also affects floral display of female plants, which is known to play a role in the attraction of pollinators and pre-dispersal seed predators. An important pollinator of the white campion, the moth Hadena bicruris (Noctuidae), also lays eggs in the flowers and its larvae feed on the developing seeds. We investigated the costs and benefits of varying flower number and size on the plant and insect fitness. We found that large flowers (or fruits) gave rise to larger larvae, and that abortion of infested fruits, a plant defence, was detrimental to larval growth. We are now investigating how floral display affects plant fitness, and whether the interaction with the seed predator could impose ecological constraints on plant reproductive traits, or select for particular floral traits.

Lecture on plant-pollinators interactions for MSc students in Plant Ecology and Physiology.
Excursions on plant ecology for BSc students in Biology.
Laboratory in cell microscopy & botany for BSc students in Biology.
Laboratory in pharmaceutical botany for first year students in Pharmacy

PhD in life sciences, supervision by Prof. G. Bernasconi,
University of Lausanne and University of Neuchâtel, 2009.

Research assistant in evolutionary botany, University of Lausanne, 2006.

Research assistant, Federal Agronomy Research Station, Changins, 2004

MSc in Ecology and Evolution, University of Fribourg, 2003.

Burkhardt A, Delph LF, and Bernasconi G. 2009. Benefits and costs to pollinating, seed-eating insects: the effect of flower size and fruit abortion on larval performance. Oecologia 161: 87-98.

Burkhardt  A, Internicola A, and Bernasconi G. 2009. Effects of pollination timing on seed paternity and seed mass in Silene latifolia (Caryophyllaceae). Annals of Botany 104: 767-773

Teixeira S, Burkhardt A, and Bernasconi G. 2008. Genetic variation among females affects paternity in a dioecious plant. Oikos 117: 1594-1600.