PhD defence LISANNA SCHMIDT 12 December at 9:15
On 12 December at 9:15 Lisanna Schmidt will defend her doctoral thesis "Phenotypic and genetic differentiation in the hybridizing species pair Carex flava and C. viridula in geographically different regions"
Senior Research Fellow Tatjana Oja, University of Tartu
Prof. Dr. Paul Ashton, Edge Hill University, United Kingdom
Plants experience different climatic and environmental conditions in different locations of their distribution areas. This can lead to different growth between populations. Moreover, populations may adapt to their local conditions. Plants of closely related plant species may also hybridize, i.e. cross between species, which may result in increased similarity. Less common species are expected to show stronger differences between regions and populations than more common species because random processes are more likely to affect the smaller populations of less common species. On the other hand, if two species hybridize with each other, they may also show similar differences between regions. We asked whether regional differences were larger in the less common sedge species Carex viridula than in the more common C. flava. We also tested whether regional differences between Estonia and lowland and highland Switzerland are mainly environmentally determined or also have a genetic basis. We assessed regional differences in morphological, size-related and floral traits in 43 populations in the field, and we studied molecular genetic differentiation. Moreover, we grew plants of all populations in three common gardens, one in each study region, which enabled us to test whether differences between species and regions are genetic, and whether plants are adapted to the environmental conditions of the home region. We found clear morphological and genetic differences between the two hybridizing species indicating that C. flava and C. viridula are indeed separate species. Nevertheless, we also found hybridization between the two and backcrossing of hybrids with the two species, which may contribute to their considerable morphological similarity. We further found that environmental effects, genetic differences and genetic differences in the expression of environmental effects all contributed to regional differences and that these differences were more pronounced in the less common C. viridula than in C. flava. This thesis contributes to understanding geographic differences in hybridizing species. This is an understudied field, which is important, however, for understanding species responses to global change and for plant conservation.
Location: Lai 40-218, Tartu