Chromosome studies on eight species of Eryngium L

Vol. 55, no. 4: 315-321, 2002
CARYOLOGIA
Chromosome studies on eight species of Eryngium L.
(Saniculoideae, Apiaceae) from Argentina
CAROLINA I. CALVIÑO, NATALY O’LEARY, EDUARDO GREIZERSTEIN*, SUSANA MARTÍNEZ and
LIDIA POGGIO
Lab. de Citogenética y Evolution, Departamento de Ecologia, Genètica y Evolucion, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, 1428, Buenos Aires, 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. et Arn. (2n=2x=16; 14m + 2sm), E. echinatum Urb. (2n=2x=16; 12m
+ 2m-sm + 2sm), E. nudicaule Lam. (2n=2x=14; 8m + 2m-sm + 4sm), E. eburneum
Decne. (2n=2x=16; 8m + 2m-sm + 6sm), E. horridum Malme (2n=2x=16; 12m +
4sm), E. megapotamicum* Malme (2n=4x=32; 4m + 6m-sm + 22sm), E. mesopotamicum* Pedersen (2n=6x=48; 30m + 16sm +2st), and E. pandanifolium Cham. et
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. pandanifolium 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.
Key Words: aneuploidy, chromosome number, Eryngium, karyotype, polyploidy,
taxonomy.
INTRODUCTION
Eryngium is the largest genus of the family
Apiaceae, widely distributed in every continent
except tropical and austral Africa. WOLFF (1913)
proposed the division of the almost 300 known
species of Eryngium into 34 sections. In Argentina, the genus is represented with 7 sections and 30
species which mostly grow in the northeast and
center of the country (MARTÍNEZ 1999; MARTÍNEZ
and CALVIÑO 2000). The majority of them belong
to sections Foetida (7 species) and Panniculata
* Corresponding author: fax: +54 11 45763384; e-mail:
[email protected].
(13 species). While the first is constituted by small
herbs with petiolate, reticulate-nerved leaves, the
second is a group of huge perennials marked by
the possession of elongated, parallel-veined leaves.
These last characters include Panniculata in a
major informal group called “monocotiledonoid”
which is exclusively American. Species of both
sections are important weeds (E. coronatum, Sect.
Foetida; E. horridum, Sect. Panniculata); others,
like E. paniculatum, Sect. Panniculata, are used as
forages in arid and semiarid zones in center and
south Argentina (ROSSI 1985; ELIZALDE 1986;
SABATINI et al. 1989).
The cytological knowledge of Eryngium consists of chromosome counts of more than a hun-
316
CALVIÑO, O’LEARY, GREIZERSTEIN, MARTINEZ
dred species (BELL and CONSTANCE 1957, 1960,
1966; CONSTANCE et al. 1971, 1976; HORE 1979;
P E R D I G O I A R I S O 1981; C O N S TA N C E and
CHUANG 1982). These data indicate the existence of at least 4 different basic chromosome
numbers (x=5, 6, 7, 8) in the genus, being x=8
the most common one. CONSTANCE (1977) mentions that about one half of the American studied
species are polyploids, with x=8 as their basic
chromosome number. Panniculata is a good
example of this as most of its species are polyploids. On the other hand, all members of section Foetida are diploids and some of them show
a basic chromosome number (x=7) lower than
the modal x=8.
Despite the great number of chromosome
counts reported for Eryngium, there has never
been described any karyotype of its species until
present. This lack of information about the karyology of the group is probably due to the small
size of its chromosomes, which impairs the distinction of the different pairs.
In this contribution, we report original chromosome numbers and karyotypes of eight species
of Eryngium belonging to sections Foetida:
E. coronatum Hook. et Arn., E. echinatum Urb.,
E. nudicaule Lam. and Panniculata: E. eburneum
Decne., E. horridum Malme, E. megapotamicum
Malme, E. mesopotamicum Pedersen, and E. pandanifolium Cham. et Schlechtd.. The significance
of the results is discussed with regards to their
taxonomic position and the relationship between
the analyzed species.
and POGGIO
MATERIALS AND METHODS
Plant material
All the material studied was collected from different populations in Argentina, as detailed in Table 1.
Voucher specimens have been deposited at the
herbaria of Instituto de Botánica Darwinion (IBODA)
except E. coronatum which is cultivated in the Botanical Garden of the Facultad de Agronomía, U.B.A.
Cytological analysis
Cytological observations were made on mitotic cells
of root-tips obtained from germinating seeds. After a
pretreatment in 8-hydroxyquinoline 0.02M solution during 3.5 hours at room temperature, the root tips were
fixed in absolute ethanol-acetic acid (3:1) and then
stained according to the Feulgen’s technique.
The nomenclature used for the description of chromosome morphology is that proposed by LEVAN et al.
(1964). The level of karyotype asymmetry was established
using two parameters according to ROMERO ZARCO
(1986): A1 = intrachromosomal asymmetry index and A2
= interchromosomal asymmetry index. Both indexes are
independent of chromosome number and size.
Determination of karyotype parameters was carried
out using the Photoshop 6.0 Programme. For chromosome counts a minimum of 17 cells were observed; mean
descriptive values for karyotypes were calculated from a
minimum of 5 scattered metaphase plates in each accession.
RESULTS
Somatic chromosome numbers, karyotype formulae, ploidy levels, satellite positions and asym-
Table 1 – Origin of the samples used in the cytological observations.
Section
Species
Foetida
E. coronatum
E. echinatum
»
E. nudicaule
Panniculata
E. eburneum
E. horridum
E. megapotamicum
»
E. mesopotamicum
E. pandanifolium
»
Voucher
Argentina. Ciudad de Buenos Aires. Agronomía. Jardín Botánico de la Facultad de
Agronomía, U.B.A. Martínez and Calviño 01.
Argentina. Entre Ríos. Dept. Concordia. Parque Nacional El Palmar. A° El Palmar. Martínez
et al. 21bis.
Argentina. Entre Ríos. Dept. Concordia. Parque Nacional El Palmar. A° Los Loros. Martínez
et al. 14.
Argentina. Entre Ríos. Dept. Concordia. Parque Nacional El Palmar. A° Los Loros. Martínez
et al. 17.
Argentina. Buenos Aires. Dept. Campana. Loc. Otamendi. Near the Reserva Provincial
Otamendi. Martínez and Calviño 4Ota.
Argentina. Buenos Aires. Dept. Campana. Loc. Otamendi. Near the Reserva Provincial
Otamendi. Martínez and Calviño 1Ota.
Argentina. Entre Ríos. Dept. Concordia. Calabacillas. Martínez et al. 11.
Argentina. Entre Ríos. Dept. Concordia. Parque Rivadavia. Martínez et al. 33bis.
Argentina. Buenos Aires. Dept. Campana. Loc. Otamendi. Near the wharf. O´Leary and
Calviño 24Ota.
Argentina. Entre Ríos. Dept. Concordia. Calabacillas. Martínez et al. 6.
Argentina. Entre Ríos. Dept. Concordia. Parque Nacional El Palmar. A° Los Loros. Martínez
et al. 29.
317
CHROMOSOME STUDIES IN ERYNGIUM
metry indexes of the eight species of Eryngium
studied are indicated in Table 2. Chromosome
counts of the species that are reported for the
first time are marked with an asterisk (*).
Section Foetida – The three species studied of
this section are diploids (Fig. 1). E. coronatum
and E. echinatum show 2n=16 (Fig. 1a, c), while
E. nudicaule shows 2n=14 (Fig. 1b).
The ideograms of the three species are shown
in Fig. 2. Most of their chromosomes are metacentric, except a few submetacentric pairs.
Besides, E. nudicaule has a big submetacentric
pair not present in the other two species (Fig.
2b). The karyotype asymmetry indexes result of
moderate level in all entities owing to the prevailing of metacentrics over submetacentrics. The
dispersion diagram resultant of both indexes of
asymmetry (A1 and A2) is shown in Fig. 4. The
species of Foetida that presents the most asymmetric karyotype is E. nudicaule, having the highest values of A1 and A2 indexes (Table 2, Fig. 4).
The three species present one pair of satellites.
These are placed in the short arm of the metacentric pair no. 2 in E. coronatum and E. echinatum. Otherwise, satellites are placed in the submetacentric pair no. 7 in E. nudicaule (Figs. 1, 2).
Section Panniculata – All the species of Panniculata analyzed present a basic chromosome
number x=8, still they show different ploidy levels.
E. eburneum (Fig. 1d) and E. horridum (Fig. 1e)
are diploids with 2n=2x=16; E. megapotamicum
(Fig. 1f) is tetraploid with 2n=4x=32; and E. pandanifolium (Fig. 1g) and E. mesopotamicum (Fig.
1h) are hexaploids with 2n=6x=48.
Karyotype formulae for these species are composed mainly of metacentric and submetacentric
chromosomes (Fig. 3), with the exception of
E. pandanifolium which shows two pairs of subtelocentric chromosomes (Fig. 3e) and E.
mesopotamicum (Fig. 3f) which shows one pair of
subtelocentric chromosomes. The dispersion diagram resultant of both asymmetry indexes is
shown in Fig. 4.
The diploid species E. eburneum and E. horridum show one pair of satellites in the chromosome pair no. 8 (Fig. 3a-b). The tetraploid species
E. megapotamicum shows two pairs of satellites in
chromosome pairs no. 8 and no. 13 (Fig. 3c). In
these three species, satellites are placed in the
short arm of submetacentric chromosomes. In the
hexaploid species satellites are difficult to recognize but a maximum of 4 satellites was observed in
E. pandanifolium and in E. mesopotamicum (data
not shown).
DISCUSSION
Seven of the eight species here studied present
x=8, the most frequent basic chromosome number
in the genus Eryngium, and in most members of
the subfamily Saniculoideae (HORE 1979; CONSTANCE and CHUANG 1982). Chromosome numbers of E. coronatum (2n=2x=16), E. megapotamicum (2n=4x=32) and E. mesopotamicum
(2n=6x=48) are reported for the first time. For
the other species, previous counts in meiotic cells
(CONSTANCE et al. 1971, 1976) support our study
and confirm the same chromosome number for
different populations of the same species. Karyomorphological investigations for the genus are
not available probably due to the small size of the
chromosomes of its species, thus karyotypes for all
the species studied in this contribution are original.
Section Foetida – E. nudicaule (2n=2x=14) is
the only species analyzed on this investigation
that presents a different – lower – basic chromosome number than the modal. In the discussion
of the different chromosome numbers of the
diploid Eryngium species, CONSTANCE (1977) was
Table 2 – Somatic chromosome numbers, karyotype formulae, ploidy levels, satellite positions and asymmetry indexes of the
eight species of Eryngium. Chromosome counts reported for the first time are marked with an asterisk (*).
Section
Species
2n
Ploidy level
Karyotype formula
Satellite position
A1
A2
Foetida
»
»
Panniculata
»
»
»
»
E. coronatum*
E. echinatum
E. nudicaule
E. eburneum
E. horridum
E. megapotamicum*
E. mesopotamicum*
E. pandanifolium
16
16
14
16
16
32
48
48
2x
2x
2x
2x
2x
4x
6x
6x
14m + 2sm
12m + 2m-sm + 2sm
8m + 2m-sm +4sm
8m + 2m-sm +6sm
12m + 4sm
4m + 6m-sm + 22sm
30m + 16sm + 2st
26m + 4m-sm + 14sm + 4st
2sa
2sa
7sa
8sa
8sa
8sa, 13sa
?
?
0.23
0.33
0.33
0.40
0.42
0.44
0.40
0.36
0.17
0.23
0.26
0.28
0.23
0.24
0.28
0.30
sa: short arm, ?: uncertain.
318
CALVIÑO, O’LEARY, GREIZERSTEIN, MARTINEZ
and POGGIO
➤
➤
➤
➤
➤
➤
➤
➤
➤
➤
➤
➤
➤
Fig. 1 – Somatic chromosomes of Eryngium. a. E. coronatum, 2n=16; b. E. nudicaule, 2n=14; c. E. echinatum, 2n=16;
d. E. eburneum, 2n=16; e. E. horridum, 2n=16; f. E. megapotamicum, 2n=32; g. E. pandanifolium, 2n=48; h. E. mesopotamicum, 2n=48; Scale 10µm. Arrowheads show satellites.
CHROMOSOME STUDIES IN ERYNGIUM
Fig. 2 – Idiograms of Eryngium, Sect. Foetida. a. E. coronatum, 14m + 2sm; b. E. echinatum, 12m + 2m-sm + 2sm;
c. E. nudicaule, 8m + 2m-sm + 4sm. Scale 2µm.
319
the first to propose that: “There appears to be a
widespread tendency to reduce the basic chromosome number of x=8…”. Phylogenetic analysis on section Foetida using other American
species of Eryngium and other genus of Saniculoideae (Sanicula, Astrantia and Alepidea) as outgroups, revealed that x=7 is a derivate basic chromosome number in Eryngium (CALVIÑO, 2001).
Our karyological study shows that E. nudicaule
(x=7) has a big submetacentric pair not present in
the other two studied species of Foetida. Thus,
on the basis of the present investigation and on
previous information from phylogenetic analysis
and chromosome studies of the genus, it appears
that the basic chromosome number x=7 occurred
by chromosome aneuploidy from the modal x=8.
The most parsimonious explanation for the
reduction of chromosome number in E. nudicaule seems to be an unequal reciprocal translocation with lost of genetic material, probably noncodifying heterochromatin.
Section Panniculata – We found three different levels of ploidy in the 5 species belonging
to this section: diploid (E. horridum and E.
eburneum, 2n=2x=16), tetraploid (E. megapotamicum, 2n=4x=32) and hexaploid (E. pandanifoli-
Figs. 3 – Idiograms of Eryngium, Sect. Panniculata. a. E. eburneum, 8m + 2m-sm + 6sm; b. E. horridum, 12m + 4sm; c. E. megapotamicum, 4m + 6m-sm + 22sm; d. E. mesopotamicum, 30m + 16sm + 2st; e. E. pandanifolium, 26m + 4m-sm +14sm + 4st. Scale 2µm.
320
CALVIÑO, O’LEARY, GREIZERSTEIN, MARTINEZ
and POGGIO
Fig. 4 – Dispersion diagram showing the relation between intra (A1) and interchromosomic (A2) asymmetry indexes. Dark
figures = Sect. Foetida; Fine figures = Sect. Panniculata.
um and E. mesopotamicum, 2n=6x=48). CONSTANCE (1977) suggests there is a chance of natural hybridization between species of Eryngium;
besides he reported the existence of hybrids in
cultivars. An hybrid origin for the 5 studied
species could explain the different ploidy levels
found, and it is supported by the fact that they
are sympatric. Furthermore, the presence of one
pair of satellites in the diploid species and two
pair of satellites in the tetraploid species, may
contribute to the hypothesis of an hybrid origin
for the last one.
Both E. eburneum and E. horridum show
the same chromosome number as previously
informed (CONSTANCE et al. 1971, 1976). Meanwhile, some authors reported 24 chromosomes
for the meiotic number of E. pandanifolium
(CONSTANCE et al. 1971), while others described
it as 16 and 32 (VIANNA and IRGANG 1971). The
material analysed in this paper is 2n=48, in agreement with CONSTANCE et al. (1971).
There is a taxonomical controversy about the
taxonomic status of E. mesopotamicum and E.
pandanifolium. Some authors (MATHIAS and CONSTANCE 1971) reduce this two species to varieties
of a single species E. pandanifolium (var. lasseauxii
and var. pandanifolium, respectively). Conversely
PEDERSEN (1997) proposes to maintain these two
taxa as independent species. Differences in chromosome number, chromosome asymmetry and
karyotype morphology are not found between
both species, thus supporting the reduction of
this two taxa to varieties as proposed by MATHIAS
and CONSTANCE (1971). Nevertheless this should
be confirmed by further cytogenetical, molecular
and morphological studies.
Sections Foetida and Panniculata are easily
differentiated by their morphological aspects.
Our chromosomal study shows that both sections could also be recognized by the morphology of its chromosomes. Section Foetida presents
more metacentric chromosomes than section
Panniculata, as it is revealed by the different
range of the intrachromosomal indexes of both
sections. While Foetida, constituted by low herbs
with petiolate, reticulate-nerved leaves, includes
diploid species with a reduction on the basic
chromosome number, Panniculata, composed by
huge herbs of monocotyledonous habit, shows all
species with the modal chromosome number x=8
but different ploidy levels. It seems as if a different mechanism of speciation has taken place in
each section: aneuploidy within Foetida and polyploidy within Panniculata. It would be interesting
to analyze if polyploidy is a general mechanism of
evolution in all monocotiledonoids, while aneuploidy is the mechanism in the species which do
not have such habit.
More studies should furnish essential information in order to understand the taxonomy and
CHROMOSOME STUDIES IN ERYNGIUM
evolution of the genus. Taxonomical controversies, different mechanisms of speciation and the
variation in karyotype morphology reported at
this time, are sufficiently interesting to justify further cytological and taxonomical studies on Eryngium.
Acknowledgments – We thank Dr. Alba Papeschi for critical revision of the manuscript. This
work has been supported by grants from the Agencia Nacional de Promoción Científica, Consejo Nacional de Investigaciones Científicas y Técnicas
(CONICET) and Universidad de Buenos Aires
(UBA) to Lidia Poggio. We also thank the Universidad de Buenos Aires for the fellowship to Carolina Calviño.
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