Doctoral defence: Marianne Kivastik "Heterostylous plants in an era of global change: the role of local, landscape and climatic factors"

On May 9 at 10:15 Marianne Kivastik will defend her doctoral thesis "Heterostylous plants in an era of global change: the role of local, landscape and climatic factors" for obtaining the degree of Doctor of Philosophy (in Botany and Mycology).

Supervisor:
Associate professor Tsipe Aavik, University of Tartu

Opponent:
Associate senior lecturer Øystein H. Opedal, Lund University (Sweden)

Summary:
Recent rapid land-use changes, along with shifts in climate, pose significant threats to various aspects of biodiversity. Among plants, animal-pollinated species, such as heterostylous species, are considered to be especially vulnerable to landscape changes because of their complex mating system.

Heterostyly is a floral polymorphism characterised by the presence of two or three morphologically different types (morphs) in a species. These morphs differ from each other in the positioning of sexual organs within the flower. The purpose of such floral polymorphism is to promote outcrossing between the opposite morphs via insect pollination and to avoid selfing within the same morph or individual.

The frequency of morphs within a population should be relatively equal to ensure maximal reproductive fitness. The aim of the thesis was to explore the role of different local, landscape and climatic factors on heterostylous species and uncover the genetic and evolutionary consequences of these processes.

My thesis shows that population size is one of the central factors causing the shifts of morph frequencies from the optimal balance of heterostylous plant populations. Contrary to expectations, the studies showed a dominance of one morph type over the other in Primula veris populations.

In addition, the results indicate that morph balance can also be affected by different landscape and climatic factors, such as the spread of built-up areas, loss of natural habitats and increased rainfall. Finally, I show that populations with unbalanced morph ratios may experience lower genetic diversity, which can, in turn, decrease the fitness and adaptability of such populations. The results from this thesis indicate the vulnerability of heterostylous species to rapid land use changes and highlight the need to maintain and protect natural habitats to secure the viability of animal-pollinated plant species.