Hybridization between Senecio smallii and S. tomentosus (Compositae) on the granitic flatrocks of the Southeastern United States
Senecio smallii andS. tomentosus occasionally hybridize on the granitic flatrocks of the Piedmont of the Southeastern United States. These hybrids are intersectional crosses between sectionsAurei andTomentosi. The parental species have different chromosome numbers withn = 22 inS. smallii andn = 23 inS. tomentosus. Meiosis in the hybrids is abnormal with 22ns and li or 2iis and 3is, and the percentage of stainable pollen is greatly reduced over that of the parents. The hybrid pollen grains are structurally abortive as demonstrated by the scanning electron microscope. Origin of the natural hybrids was documented by the production of artificial hybrids including F1’s, F2’s, and BC’s. Very few of the F2 seeds germinated, and all of the F2 seedlings later died, indicating hybrid breakdown. Seeds of the F1 and BC generations germinated well, and the seedlings were vigorous. Population samples indicate that there is some variation within the natural population systems; however, no evidence of introgression was detected. The isolating mechanisms and possible evolutionary effects of this natural hybridization are discussed.
Bertilia — A new monotypic genus in the Senecioneae (Asteraceae) from South Africa
Abstract The unusual disjunct distribution of the yellow-flowered, radiate, Northern Cape endemic Emilia hantamensis J.C.Manning & Goldblatt, relative to the other Emilia species in southern Africa, prompted investigation into its phylogenetic position and relationships. Phylogenies based on the ITS and trn L– trn F regions reveal that it is not a member of the genus Emilia but belongs in a well-supported clade with Bolandia , a genus comprising five species mainly from the Western and Northern Cape, and the monotypic genera Stilpnogyne and Mesogramma . It is placed sister to Bolandia and its cypselas match those of Bolandia in shape, colour and indumentum, except for a distinct ridge of hairs on the inner rib of the ray cypselas. It is further distinguished from Bolandia by its annual habit and conical disc floret style apices and obtuse to rounded ray floret style apices. It is recognised and described here as a new monotypic genus, Bertilia Cron with the single species B. hantamensis (J.C.Manning & Goldblatt) Cron.
Grundzüge der Pflanzenverbreitung in der Aegäis I
Einleitung . . . . . . . . . I. Die phytogeographische Stellung und Gliederung der Aeg~is Die SteUung der Aeg~is innerhalb des Mittelmeergebietes und dessen Begrenzung . . . . Die floristische Gliederung der Aeg~is. Uebersicht Ueber die Aeg~iis allgemein verbreitete Arten Das wesfiig~iische Gebiet Das nord~igNische Gebiet Das nordost~g~ische Gebiet Das ost~g~ische Gebiet Das siid~g~ische Gebiet 1. Oestliche Arten 2. Weitverbreitete Arten 3. Siidliche Arten 4. Westliche Arten 5. Balkanische Arten" 6. Balkanisch-anatolische ~t~ten Das zentraliigiiische Gebiet 55 56