Molecular, karyological, morphological and evolutionary biosystematics of Veronica and related genera (Scrophulariaceae s.l.; ´Antirrhinaceae´)

There is no unambiguous definition for evolutionary success for such plant taxa that we call successful. One such case is the genus Veronica which has managed to invade almost any habitat available to plants outside the tropics. From semideserts to aquatic, alpine, and woody habitats we find the species of Veronica. Many species have followed man into arable land like fields and gardens. What are the biological reasons for this success? Even though botanists have studied the genus, especially the European species, for a very long time, there are still many doubts about the relationships. Results of phytochemical and embryological studies of the last three decades are largely incongruent with the traditional taxonomy based on morphology and structural characters. Although such evidence has caused some doubts that the genus is possibly artificially defined and delimited, based on the four lobed, rotate corolla and only two stamens, there still exists no publication explicitly doubting the monophyly of the genus. First molecular data agree with phytochemistry and embryology in many respects and additionally show Veronica to be paraphyletic with respect to the Hebe complex and possibly other genera (Albach & Chase, 1999, submitted).Therefore, the proposed research shall further identify the relationships between major groups within the genus and related genera and elucidate the patterns of evolutionary trends of the group. Different molecular (DNA sequence data, AFLPs), karyological (chromosome numbers, genome size), phytochemical (iridoid and flavonoid compounds) and structural (especially seeds and pollen) characters will be generated in this project in cooperation with other scientists. Together, they will give us a better assessment of the relationships within the genus and the tribe and the evolution of various characters. Four studies on representative smaller groups of species within the genus will investigate evolutionary mechanisms that may be responsible for the diversification of the whole genus. Historical effects, such as glaciation, can disrupt gene flow especially between populations of alpine species and lead to independent evolution among lineages. In several taxa within Veronica, polyploidy occurs and hybridization is common in several groups. These mechanisms, particularly allopolyploidy, lead to individuals with new combinations of genes with possible novel characters giving rise to new species that allow the occupation of a different ecological niche. Finally, intraspecific variation and phenotypic plasticity allow species to grow under a wide range of habitats, but they also make it difficult to distinguish between closely related species.

Whether you are in the steppes of Central Asia, in brooklets and lakes of Central Europe or in over 5000 meters in the Himalayas, you may always - with an exception in the tropical rainforests - encounter a species of Veronica, also known as speedwells. It is astonishing how the more than 450 species of the genus with it four-lobed flowers manage to flourish in almost all environments. In our project, we determined the relationships of most species und showed for example that the species from New Zealand ("Hebe") evolved from species from the Northern Hemisphere. More importantly, we demonstrated that annual species evolved several times independently and in parallel from perennial species. This allowed investigating the evolution of annual life history in more detail. We could support the hypothesis that annual species have faster-changing DNA sequences than perennials. Another hypothesis says that annuals have less DNA per cell than perennials. This, however, seems to be an artefact based on the correlation of annual life history with self-fertilization. The latter seems to be the decisive factor causing a smaller genome in Veronica. More detailed analyses of small species groups demonstrated for example that the Mediterranean V. cymbalaria is a hybrid that evolved multiple times independently from its progenitors. We discovered a highly reduced genetic variation in V. bellidioides from the Alps, which is probably caused by a highly reduced number of individuals during the ice ages. The more widespread European V. alpina contains much more genetic variation but still not as much as its North American relatives. It, therefore, seems that the ice ages were much more severe for alpine plants in Europe than for those in North America.