Chromosome studies on eight species ofEryngiumL. (Saniculoideae, Apiaceae) from Argentina

Abstract

A cytological analysis of eight Argentinean species of Eryngium L. (Saniculoideae, Apiaceae) is carried out. Karyotypes of eight species and original chromosome counts for three of them (indicated with an asterisk) are notified: E. coronatum*Hook.Schlechtd. (2n=6x=48; 26m+ 4m-sm +14sm + 4st). The first three species belong to the Section Foetida, while the remaining five, belong to Panniculata. Both Sections are easily differentiated by morphology; our chromosomal study shows that these sections can also be recognized karyologically. All the species, except E. nudicaule (x=7), present x=8 which is the most common basic chromosome number in the genus and in the subfamily Saniculoideae. The karyotype analysis made on the eight species mainly shows metacentric and submetacentric chromosomes differing in proportion between species; only E. pandanzfolium and E. mesopotamicum show subtelocentric pairs. These two species only differ in the color of their inflorescences; besides, differences in their karyotypes were negligible. These facts agree with the suggestion that they would be varieties of the same species. Two different phenomena seem to have occurred during karyotype evolution in the genus Eryngium: aneuploidy within Section Foetida, and polyploidy within Section Panniculata.

Further cytogenetical studies on diploid and polyploid species of Eryngium L. (Saniculoideae, Apiaceae) from Argentina

“…The other five studied species belong to section Panniculata, a group where polyploidy seems to have played a major role in speciation. C alviño et al . (2002) found three ploidy levels: diploid ( E. horridum and E. eburneum , 2n=2x=16), tetraploid ( E. megapotamicum , 2n=4x=32) and hexaploid ( E. pandanifolium and E. mesopotamicum , 2n=6x=48).…”

“…Eryngium nudicaule is a widely distributed and highly polymorphic taxon (M artínez and G alotti 2001) that has already been cytologically studied (in meiosis and mitosis) in several Brazilian and Argentinean populations (C onstance et al 1971; V ianna and I rgang 1971; A lmada et al 2002; C alviño et al 2002). In the present work the gametic chromosome number n=7 for this diploid species is confirmed.…”

“…In a recent cladistic analysis on this section (C alviño 2001), mostly based on morphological characters, the basic chromosome number x=7 appears as a atavic number originated in the common ancestor of E. nudicaule and E. corallinum . C alviño et al (2002) and A lmada et al (2002) have suggested that aneuploidy could explain the reduction of the modal basic number x=8 to x=7. C alviño et al .…”

“…C alviño et al (2002) and A lmada et al (2002) have suggested that aneuploidy could explain the reduction of the modal basic number x=8 to x=7. C alviño et al . (2002) based on karyotype analysis, stated that the most parsimonious explanation for the reduction of the chromosome number seemed to be an unequal reciprocal translocation with loss of nonessential genetic material.…”

“…Although the most common basic chromosome number in Eryngium is x=8 (C onstance 1977) some taxa show a basic chromosome number x=7 ( E. nudicaule 2n=2x=14) (C onstance et al 1971; V ianna and I rgang 1971; C alviño et al 2002). Meanwhile, all studied species in section Panniculata show the same basic chromosome number (x=8) but different ploidy levels (C alviño et al 2002). In the latter section the delimitation and identification of the species offers difficulties due to their morphological similarities and the probable occurrence of hybridization and even some degree of introgression in transitional zones (C onstance 1977; O'L eary 2002).…”