Hybrids between Rubus idaeus and Rubus sect. Corylifolii and their relation to R. pruinosus and R. rosanthus

We have studied hybrids between Rubus idaeus and various members of R.
Sect. Corylifolii, primarily in Sweden. With the help of DNA-ploidy level
determinations using flow cytometry and microsatellite DNA analysis of
over 500 samples, we show that the material can be divided into four
stable apomictic species (belonging to Subsect. Subidaei) and a large
number of primary hybrids. Stable species can be recognised by a
distribution that is distinct from the Corylifolii parent, a uniform
morphology and an almost invariant genetic pattern. We confirm that R.
cordatiformis has arisen from the hybrid R. eluxatus idaeus. Moreover, our
study shows that R. lagerbergii has arisen from the hybrid R. dissimulans
idaeus. For R. onsalaënsis, we unexpectedly identify the Corylifolii
ancestor as a previously unidentified blackberry with a very restricted
distribution in the northern part of the province of Halland, which is
here described as R. antecedens. Furthermore, we show that R. pruinosus s.
str. has arisen from the hybrid R. aureolus idaeus and that it is known
only from a rather restricted area in the provinces of Småland,
Östergötland and Södermanland in eastern Sweden. On the other hand, the
great majority of what has been called R. pruinosus is a diverse
collection of primary hybrids between R. idaeus and various Corylifolii
species, which show a large variation both genetically and
morphologically. The same applies to R. rosanthus, which represents R.
norvegicus idaeus hybrids: The microsatellite analysis shows that they
have arisen independently and therefore should be considered as primary
hybrids. We have identified primary hybrids between R. idaeus and R.
gothicus (by far the most common hybrid in Sweden), R. aureolus, R.
camptostachys, R. decurrentispinus, R. eluxatus, R. friesianus, R.
hallandicus, R. lidforssii and R. norvegicus.