Isozymes, Speciation and Evolution in the Polyploid Complex Cochlearia L. (Brassicaceae)

Abstract

Within the genus Coch/earia l. sect. Coch/earia three isozyme systems (aspartate aminotransferase, leucine aminopeptidase and phosphoglucomutase) have been analysed at the populational level for eleven species with different ploidy levels. Nine loci complexes were resolved with a total of 33 alleles from 89 populations.In general, polypiaids displayed higher numbers of alleles per species and per population. A notable exception is diploid C.pyrenaiea with as many alleles as some polyploids. Data support: (1) the origin of tetraploid C.officinalis from C.pyrenaiea s.l., particularly from C.aestuaria; (2) the atuopolyploid origin of octoploid C. anglica from C.offieinalis; (3) the allopolyploid origin of hexaploid inland taxa C.p%niea, C.tatrae and C.bavariea via hybridization between C.pyrenaiea and C.officinatis; (4) a putative allopolyploid origin of hexaploid coastal species C.daniea by hybridization between C.pyrenaiea s./. and C. officinalis accompanied by a shift in chromosome complement. A scenario summarizing our present understanding of the evolution within Coch/earia sect. Coch/earia is presented.

Conflicting patterns of genetic and morphological variation in European Gentianella section Gentianella

“…4). Hybridization and repeated backcrossing during postglacial colonization and succession, as observed in oaks (Petit et al, 1997) and in Cochlearia (Koch, Huthmann & Hurka, 1998;Koch, 2002), is a possible explanation for these genetic similarities that are in line with poor morphological characterization leading to uncertainties in taxonomic treatments of the taxa. Reticulate evolution, however, need not be a postglacial phenomenon.…”

A Time-Calibrated Road Map of Brassicaceae Species Radiation and Evolutionary History

“…An increase in the number of polyploids coupled with increased speciation rates and species richness has been demonstrated for a few significant groups within the Brassicaceae: tribe Arabideae, and in particular for the largest genus in the family, Draba, with ;400 species (Jordon-Thaden et al, 2013); tribe Heliophileae (Mandáková et al, 2012); and Cochlearia within tribe Cochlearieae (Koch et al, 1998). These radiations are all recent diversifications seen within the scenarios of increased aridity in the Late Pliocene and of alternating cold and warm phases during Pleistocene glaciation and deglaciation cycles (Warren and Hawkins, 2006;Mandáková et al, 2012).…”

“…Finally, we added 12 newly sequenced chloroplast genomes from various Brassicaceae including five chloroplast genomes from Arabidopsis representing all major lineages of the genus (Hohmann et al, 2014), as well as their close relatives Capsella rubella and Camelina sativa. Five genomes were added from Cochlearia and Ionopsidium representing the best documented example of reticulate evolution that has generated a series of auto-and allopolyploids (Koch et al, 1998(Koch et al, , 1999(Koch et al, , 2003Koch, 2002Koch, , 2012. In total, we included 29 Brassicaceae chloroplast genomes from 11 tribes and all three major evolutionary lineages.…”

Molecular systematics of the New ZealandPachycladon(Brassicaceae) complex: Generic circumscription and relationships toArabidopsissens. lat. andArabissens. lat.

“…it is up to 6.0% (Mummenhoff et al 1997b;Franzke et al 1998;Koch et al 1999a;Koch & AlShehbaz 2000). For more distantly related congeneric species or closely related genera of the Brassicaceae, sequence divergence is often greater than 10%, and sometimes over 25% (Franzke et al 1998;Koch et al 1998;Koch & Al-Shehbaz 2000;Koch & Mummenhoff 2001). …”