Pollen Studies in Subtribe Centaureinae (Asteraceae): The Carthamus Complex and the Genus Aegialophila Analyzed with Electron Microscopy

Abstract

Recent molecular and karyologic studies have deeply modified the delimitation of the genera of the Carthamus complex, and have led to a new classification of the group in four genera (Carduncellus, Carthamus, Femeniasia and Phonus). Molecular studies have confirmed the position of the group among the derived genera of the subtribe Centaureinae, and have suggested a faint relationship between the Carthamus complex and the small genus Aegialophila. However, despite the importance of pollen evolution in the subtribe, a comprehensive study of the pollen of the involved genera with electron microscopy was lacking. Therefore, we have carried out a survey of pollen morphology and ultrastructure in a wide sample of the genera, using both scanning and transmission electron microscopy. Our results suggest that pollen type of the Carthamus complex is homogeneous and should be classified as a new pollen type in the classification of Wagenitz. Pollen type of Aegialophila shows strong similarities with the Centaurea scabiosa pollen type of Wagenitz, but there are slight differences in shape and in ultrastructure of the exine. These differences are evaluated, together with morphological and molecular evidence; the authors conclude that similarities are the result of parallel evolution and that pollen of Aegialophila could be considered a new pollen type. Some considerations are made on the placement of the new types in the cadre of pollen and molecular evolution in the subtribe Centaureinae.

Key words

Aegialophila - Carduncellus - Carthamus - Femeniasia - Phonus - pollen - electron microscopy

References

• 01 Ashri,  A., and Knowles,  P. F.. (1960);  Cytogenetics of safflower (Carthamus L.) species and their hybrids.  Agron. J.. 52 11-17
• 02 Avetisian,  E. M.. (1950);  Simplified method of pollen preparation by acetolysis (in Russian).  Zurn. Russk. Bot. Obsc. Akad. Nauk SSSR. 35 385
• 03 Dittrich,  M.. (1977) Cynareae - systematic review. The Biology and Chemistry of Compositae, Vol. I. Heywood, V. H., Harborne, J. B., and Turner, B. L., eds. London; Academic Press pp. 999-1015
• 04 Erdtman,  G.. (1952) Pollen morphology and plant taxonomy. Angiosperms. Stockholm; Almqvist and Wiksell
• 05 Estilai,  A., and Knowles,  P. F.. (1978);  Relationship of Carthamus leucocaulos to other Carthamus species (Compositae).  Canad. J. Genet. Cytol.. 20 221-233
• 06 Faegri,  K., and Iversen,  J.. (1964) Textbook of pollen analysis. Oxford; Blackwell Scientific Publications
• 07 Garcia-Jacas,  N., and Susanna,  A.. (1994);  Centaurea prolongi and C. crocata in Portugal: an old confusion.  Nord. J. Bot.. 14 31-38
• 08 Garcia-Jacas,  N.,, Susanna,  A.,, Garnatje,  T.,, and Vilatersana,  R.. (2001);  Generic delimitation and phylogeny of the subtribe Centaureinae (Asteraceae): a combined nuclear and chloroplast DNA analysis.  Ann. Bot. (London). 87 503-515
• 09 Garcia-Jacas,  N.,, Susanna,  A.,, Mozaffarian,  V.,, and Ilarslan,  R.. (2000);  The natural delimitation of Centaurea (Asteraceae: Cardueae): ITS sequences analysis of the Jacea group.  Pl. Syst. Evol.. 223 185-199
• 10 Hanelt,  P.. (1963);  Monographische Übersicht der Gattung Carthamus L. (Compositae).  Feddes Repert.. 67 41-180
• 11 López González,  G.. (1990);  Acerca de la clasificación natural del género Carthamus L., s.l.  Anales J. Bot. Madrid. 47 11-34
• 12 Martín Villodre,  J., and Garcia-Jacas,  N.. (2000);  Pollen studies in subtribe Centaureinae (Asteraceae): the Jacea group analyzed with electron microscopy.  Bot. J. Linn. Soc. . 133 473-484
• 13 Petit,  D. P.,, Mathez,  J.,, and Qaid,  A.. (1996) Early differentiation of the Cardueae sense lato: morphology and pollen. Compositae: Systematics. Proceedings of the International Compositae Conference, Kew, 1994. Hind, D. J. N. and Beentje, H. G., eds. Kew; Royal Botanical Gardens pp. 79-93
• 14 Susanna,  A., and Garcia-Jacas,  N.. (2001) The tribe Cardueae. The Families and Genera of Flowering Plants; Asteraceae. Kubitzki, J., ed.; Kadereit, J., ed. Heidelberg; Springer in press
• 15 Susanna,  A.,, Garcia-Jacas,  N.,, Soltis,  D. E.,, and Soltis,  P. S.. (1995);  Phylogenetic relationships in tribe Cardueae (Asteraceae) based on ITS sequences.  Amer. J. Bot.. 82 1056-1068
• 16 Susanna,  A., and Vilatersana,  R.. (1996);  Las afinidades de Femeniasia Susanna (Compositae) o rectificar es de sabios.  Anales J. Bot. Madrid. 54 355-357
• 17 Tornadore,  N.,, Marcucci,  R.,, and Marchiori,  S.. (1998);  Aegialophila pumila (L.) Boiss. (Asteraceae): a new species in Italy.  Israel J. Pl. Sci.. 46 (1) 61-65
• 18 Vilatersana,  R.,, Susanna,  A.,, Garcia-Jacas,  N.,, and Garnatje,  T.. (2000 a);  Generic delimitation and phylogeny of the Carduncellus-Carthamus complex (Asteraceae) based on ITS sequences.  Pl. Syst. Evol.. 221 89-105
• 19 Vilatersana,  R.,, Susanna,  A.,, Garcia-Jacas,  N.,, and Garnatje,  T.. (2000 b);  Karyology, generic delineation and dysploidy in the genera Carduncellus, Carthamus and Phonus (Asteraceae).  Bot. J. Linn. Soc.. 134 425-438
• 20 Wagenitz,  G.. (1955);  Pollenmorphologie und Systematik in der Gattung Centaurea L. s.l.  Flora. 142 213-279
• 21 Wagenitz,  G., and Hellwig,  F. H.. (1996) Evolution of characters and phylogeny of the Centaureinae. Compositae: Systematics. Proceedings of the International Compositae Conference, Kew, 1994. Hind, D. J. N. and Beentje, H. G., eds. Kew; Royal Botanical Gardens pp. 491-510
• 22 Wagenitz,  G., and Hellwig,  F. H.. (2000);  The genus Psephellus Cass. (Compositae, Cardueae) revisited with a broadened concept.  Willdenowia. 30 29-44

Section Editor: F. Salamini