Scorzoneroides autumnalis as a model to link phenotypic expression and genomic differentiation with ecotype specialization, phylogeographic history and taxonomic complexity

Ecotype differentiation in Scorzoneroides autumnalis

Scandinavia has been recolonized by plants after the last glaciation and few species are therefore endemic to the region. On the other hand, several groups of plants have developed more or less distinct ecotypes. These may represent a first step towards speciation, initiated after post-glacial migration. They may alternatively represent older lineages that have arrived from different directions and at different times. Differentiation may thus have originated at one or several occasions and the future development is dependent on local selection pressures, current gene flow among ecotypes and possible development of sterility barriers.

The Asteraceae family belong to the crown of the angiosperm phylogenetic tree, representing one of the fastest radiating families during the recent millions of years. We aim to understand what traits have made this plant family successful through studies of Scorzoneroides (Leontodon) autumnalis. This taxon incorporates several different ecotypes specialized for certain habitats – meadow ecotype, coastal ecotype, alvar ecotype and most probably several different alpine ecotypes, which of at least one appear to be specialized for snowbed vegetation. The species is known to be out-crossing, uniform with respect to chromosomal counts and predominantly self-incompatible. Despite being one of the most widely
distributed species in Scandinavia, its ecotypes are still poorely characterized and only provisionally taxonomically investigated.

The doctorate project is devided into three subprojects:
(1) Morphometric studies based on herbarium specimens aiming at a general description of the geographic distribution of morphotypes/ecotypes/taxa in the Nordic area and the degree to which different characters are affected by local selection pressures.
(2) Common-garden studies aiming at specifying patterns of heritability, phenotypic plasticity and interfertility of different morphotypes/ecotypes.
(3) Assessment of genetic differentiation and phylogeographic patterns among ecotypes and populations from different geographic regions. We plan to use RAD-sequencing (restriction assisted DNA sequencing), a next generation sequencing technique by which thousands of SNPs distributed over the entire genome can be studied.

The ultimate goals of the project are to understand the processes that are promoting respectively counteracting speciation in plants, and to understand which traits are selected among the ecotypes and how this is linked to differences at genomic level.