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Original article
Distribution and ecological consequences of ploidy variation in
Artemisia sieberi in Iran
Adel Jalili
a
,
*
, Mina Rabie
b
, Hossein Azarnivand
c
, John G. Hodgson
d
, Hossein Arzani
c
,
Ziba Jamzad
a
, Younes Asri
a
, Behnam Hamzehee
a
, Farzaneh Ghasemi
a
,
S.M. Hesamzadeh Hejazi
a
, R. Abbas-Azimi
a
a
Research Institute of Forests and Rangelands, P.O. Box 13185-116, Tehran, Iran
b
Payamenoor University, Karaj Branch, Karaj, Iran
c
Faculty of Natural Resources, University of Tehran, Karaj, Iran
d
Peak Science and Environment, Station House, Leadmill, Hathersage, Hope Valley S32 IBA, UK
article info
Article history:
Received 6 March 2013
Accepted 23 September 2013
Available online 17 October 2013
Keywords:
Artemisia
Asteraceae
Cytotypes
Irano-Turanian region
Leaf anatomy
Polyploidy
Steppe
Semi-desert
abstract
Because of their high proportion in the plant kingdom polyploid taxa are considered to have had
evolutionary advantages over their diploid ancestors. These advantages may have included new char-
acteristics that enable polyploids to occupy a broader range of habitats. In this context, we assess the
ecological range of Artemisia sieberi, a canopy dominant within an important vegetation type in Iran. We
assess the extent to which ploidy covaries with geographical and ecological distribution and look for
ecologically-significant differences in the functional characteristics of diploids and polyploids.
Populations of A. sieberi were sampled widely in Iran and soil characteristics, climate and anatomical
and phytochemical plant attributes were measured. Also, in parallel, an independent genetic assessment
of populations was carried out using genetic fingerprinting.
Two ploidy levels were identified: 75% of the 34 populations of A. sieberi populations sampled were
tetraploid (2n¼4x¼36) with the remainder diploid (2n¼2x¼18). Plants of differing ploidy also
differed anatomically, genetically and chemically. Tetraploid populations had larger cells and lower
stomatal densities and a different essential oil composition. They also appear ecologically distinct,
occupying more fertile, mesic habitats than diploids.
Genetic fingerprinting revealed the existence of two genetically differentiated subgroups independent
of ploidy but with some geographic and ecological pattern. We conclude that diploids and tetraploids
have a different ecological distribution and that the absence of mixed diploid-tetraploid populations is a
reflection of differing fitness in different habitats. We suspect that a key ecological difference between
diploids and tetraploids is the increased stomatal size of tetraploids, possibly resulting from the
increased genome and hence cell size following polyploidisation. Polyploid-formation may be con-
strained in arid habitats by problems of water-use efficiency associated with the larger stomata originally
produced.
Ó2013 Elsevier Masson SAS. All rights reserved.
1. Introduction
A majority of angiosperms appears to be of polyploid origin (see
Masterson, 1994). This implies that polyploid taxa often have an
evolutionary advantage over related diploids (Mandakova and
Munzbergova, 2008). Genome duplication can fundamentally
alter a plant’s genetic make-up, morphology, physiology and ecol-
ogy within a single or few generations. The effects of these changes
are, however, far from uniform. Polyploidy variously affects species
interactions (Thompson et al., 2004), habitat preferences (Arvanitis
et al., 2007) and long-distance dispersal (Harbaugh, 2008). More-
over, new functions and novel phenotypic variation may evolve
(Soltis and Soltis, 2000; Bretagnolle and Thompson, 2001; Udall
and Wendel, 2006) with some polyploids able to exploit strongly
fluctuating environments or effectively colonize new or a wider
range of habitats (Levin, 1983; Bayer et al., 1991; Rieseberg and
Willis, 2007; Rivero-Guerra, 2008; te Beest et al., 2012).
Changes in morphology, anatomy, and biochemistry, may affect
photosynthetic rate (Vyas et al., 2007) and result in ecological dif-
ferentiation (Otto and Whitton, 2000; Rieseberg and Willis, 2007;
*Corresponding author. Tel.: þ98 21 44580282 5.
E-mail addresses: jalili@rifr-ac.ir,jaliliadel@yahoo.co.uk (A. Jalili).
Contents lists available at ScienceDirect
Acta Oecologica
journal homepage: www.elsevier.com/locate/actoec
1146-609X/$ esee front matter Ó2013 Elsevier Masson SAS. All rights reserved.
http://dx.doi.org/10.1016/j.actao.2013.09.008
Acta Oecologica 53 (2013) 95e101
Author's personal copy
Rivero-Guerra, 2008). However, the mechanistic origin of altered
ecological behavior is often obscure. Moreover, it is complicated by
the fact that, although subsequent selection frequently causes a
reduction, the doubling in chromosome number initially results in
an increased genome size, and, therefore, in cell size, cell cycle
length and organ size (see Bennett, 1987; Bennett and Leitch, 2005;
Stupar et al., 2007;
Símová and Herben, 2012). As a result, increased
ploidy level within species is typically associated with larger sto-
matal guard cells and a decrease in stomatal density (Byrne et al.,
1981; Cohen and Yao, 1996; Hodgson et al., 2010). Water-use effi-
ciency in polyploids is potentially compromised since closure of
large stomata is inherently less rapid (Hetherington and
Woodward, 2003). Moreover, the disproportionate increase in
length of the cell cycle associated with a larger genome might be
expected to affect the phenology of recent polyploids. Large ge-
nomes predispose species to exhibit cool-season growth (see Grime
and Mowforth, 1982; Grime et al., 1985; Bennett, 1987; Hodgson
et al., 2010; Veselý et al., 2012; McIntyre, 2012). Therefore, in
addition to ecological and physiological novelty resulting directly
from qualitative changes to the composition of the genotype, im-
pacts of polyploidy on ecological distribution may result directly
through the larger cells and longer duration of the mitotic cell cycle
that is likely to be a feature of newly-formed polyploids.
Here, we explore the ecological impact of polyploidy in a context
relevant to the conservation of ecosystems. Of necessity, field
ecologists tend to identify taxa only to the species level and, as a
result, tend not to factor considerations of intraspecific variation in
polyploidy into their management recommendations. There are
situations where this may be ill-advised. Take Artemisia sieberi
Bess., perhaps Iran’s most abundant plant. A.sieberi-dominated
vegetation covers over 20 million hectares in Iran (12% of country),
mainly in the desert, arid and semi-arid steppes. Moreover, this
community plays a vital role in plant genetic and biodiversity
conservation in Iran (Rabie, 2008) and, since the canopy dominant
potentially has a marked effect on ecosystem function, ecological
differences relating to ploidy are potentially highly significant.
Accordingly, building upon earlier work on the ecological tolerance
and distributional ranges of diploid and polyploid races in Artemisia
carried out by Valles and Torrell (2001a, b), Valles et al. (2005),
Garcia et al. (2006) and Pellicer et al. (2007), we assess differ-
ences in the distribution and ecological characteristics of diploid
and polyploid A.sieberi and attempt to separate effects of genotype
and phenotype.
Here we examine the geographical distribution of ploidy in
A. sieberi throughout Iran. In each of 34 populations we took
morphological and ecological measurements and we determined
the ploidy level that characterized the population. Furthermore we
used genetic (AFLP) markers to test for population genetic differ-
entiation among populations, between ploidy levels and along
ecological and geographical gradients.
2. Materials and methods
2.1. Field sampling
Though a dominant species over large parts of Iran, A. sieberi has
a discontinuous distribution interrupted by desert dry lakes,
‘playas’and other topographical barriers. Site selection involved
two maps, the ’Iran vegetation map’(Shakoei et al., 1987 (2006))
and the ‘Iran climatic zoning map’(Khalili et al., 19641984)). From
the first map major plant communities dominated by A. sieberi
were identified. Subsequently, the second map allowed the climate
associated with A. sieberi populations to be categorized as semi-
desert, arid and semi-arid. Sites were selected so as to maximize
the range of altitude and geographical dispersion of sites within
each climatic zone while ensuring that sites were also relatively
near to climataological stations. The location of each of the 34 sites
selected is illustrated in Fig. 1 and their geographical and climatic
characteristics outlined in Supplementary Table 1.
Minimal area (MuellereDombois and Ellenberg, 1974)was
calculated at each of the 34 A. sieberi-dominated sites selected and
an appropriate plot size (including 90% of the total species present)
was subsequently adopted, typically between 4 and 16 m
2
. Each site
was then subdivided into five homogenous units. Within each
unite, one plot (replicates) was randomly located and within each
plot; fresh plant materials and achenes of five plants of A. sieberi
were individually collected. Thus we had material from 25 distinct
individuals from each population. Soil samples of each plot for
chemical and physical analysis from within the plant’s rooting zone
(ca. 0e40 cm depth) were taken. Because Artemisia is a taxonom-
ically difficult genus, the identification of each specimen collected
was confirmed using both Flora Iranica (Podlech, 1986) and the
herbarium vouchers of this research are deposited in the herbarium
of Research Institute of Forests and Rangelands (TARI).
2.2. Laboratory measurements
Soil texture; the percentage of sand, silt and clay was deter-
mined by the hydrometer method (Bouyoucus, 1951). Soil pH and
EC (electrical conductivity) in a suspension of 1:5 soil:water ratio
was determined by pH meter glass electrode and EC meter
respectively. The percentage of CaCO
3
was measured using
Calcimeter (Allison and Moode, 1965) and soil organic mater (OM)
by Walkley and Black method (Nelson and Sommers, 1996). The soil
phosphorous (Olsen et al., 1954), nitrogen (Kjeldahal method), and
K
þ
,Ca
þ2
,Na
þ
,Fe
þ2
were determined by atomic absorption spec-
troscopy (Nelson and Sommers, 1996). Leaf area, thickness, water
content and toughness leaf tensile strength, all leaf traits relating to
soil fertility and the ‘worldwide leaf economics spectrum’of Wright
et al. (2004), were measured for fresh leaves using protocols
described in Charles et al. (1997) and Cornelissen et al. (2003).
Complementary anatomical traits relating to photosynthesis and
water use efficiency (stomata density and length, cuticle and
mesophyll parenchyma thickness) were also measured. For
anatomical study, five fully expanded leaves of each individual
plant were selected and a minimum of ten transverse sections were
Fig. 1. Pattern of Artemisia sieberi geographical distribution in Iran; 2n¼18 (-),
2n¼36 (C).
A. Jalili et al. / Acta Oecologica 53 (2013) 95e10196
Author's personal copy
prepared from each and a similar number of slides of stomatal
impressions were prepared from both the upper and lower surfaces
using colorless nail polish. Stomata density (number mm
2
leaf
area), stomata length (
m
), Thickness of leaf lamina and its compo-
nent tissues (
m
) including; mesophyll layers and cuticle were
measured. All anatomical studies were carried out using a light
fluorescence microscope (Olympus BH2-RFCA). Each anatomical
attribute was measured at an appropriate magnification, e.g. 100
for stomata length, 40for parenchyma thickness and stomata
density (Rashidi et al., 2012).
To estimate the essential oil content of the plant shoot, plants
were air-dried in the shade and, after extraction by hydro-
distillation, the composition of the extract was evaluated by GC
(gas chromatography) and GCeMS (gas chromatography/mass
spectrometry) (Weyerstahl et al., 1993; Rabie et al., 2006).
To provide material for chromosome counts, root tip meristems
of young seedlings were pre-treated with cold water at 0
C for
24 h, fixed in Carnoy’s reagent for at least 24 h at room temperature
and subsequently rinsed for 1 h in distilled water. The tissues were
hydrolyzed in 1 N HCl at 60
C for 8 min, stained with hematoxylin
for 3e4 h and squashed in a droplet of 45% acetic acid and lactic
acid (10:1). Preparations were examined under an optical micro-
scope (SZH-ILLB Olympus supplemented digital color video cam-
era) at a magnification of 1500. At least five metaphase plates
were selected and chromosome numbers were counted (Saedi
et al., 2005).
DNA was extracted from 4 g of fresh young leaves stored in
liquid nitrogen at 80
C using the method of SaghaieMaroof et al.
(1984). AFLP, a technique for DNA fingerprinting, followed the
protocol described by Vos et al. (1995), with slight modifications.
The primary template was prepared by the simultaneous digestion
of DNA with Eco RI and Mse I and subsequent ligation of asymmetric
quantities of enzyme specific adapters. Pre-amplification and
selective-amplification were performed with eight primer pairs.
Active amplification products were size-fractionated on 6% poly-
acrylamide denaturing gel. Electrophoresis was carried out for 1 h
in 1TBE at 85 v/cm at 50
C. The gels were stained with silver
nitrate for 30 min and the bands developed. Data from AFLP were
scored for presence (1) and absence (0) and entered into a binary
matrix representing the data profile of each accession.
The amount of information obtained by AFLP is a factor of the
number of selective nucleotides employed and the size and
complexity of the genome being analyzed. As with other attributes,
DNA was studied for all 34 populations of Artemisia. Moreover, each
population had five plots, or replicates, for DNA extraction. The
inclusion of all these samples allowed the robustness and repro-
ducibility of the AFLP protocol to be tested.
2.3. Data analysis
AFLP from the 8 primer pairs were registered in terms of the
presence or absence of bands in each of the 34 accessions evalu-
ated. The results were converted into a similarity matrix, based on
Jaccard’s index. To identify possible DNA-based Groups, the simi-
larity matrix was analyzed, using the computer program NTSYS
(Rohlf, 1990) with dendrograms constructed using the option TREE
and the Complete method. To analyze the complementary or
redundancy of the information, a correlation index was calculated
between the similarity matrices resulting from the eight different
primer pairs.
To simplify subsequent analyses, and to account for multiple
measures per plant and per leaf that led to our having different
numbers of replicates for different plant characteristic, we calcu-
lated mean value of each measured characteristic for each popula-
tion, giving us 34 values for each character. The main axes of
variation in environmental variables and leaf characters were
identified by principal components analysis (PCA) using MINITAB-
14. To test differences between ploidys or genetic groups for the
measured characters we used one way analysis of variance (ANOVA).
3. Results
Two ploidy levels of A. sieberi were identified. Diploid
(2n¼2x¼18) and tetraploid populations (2n¼4x¼36) were both
widely distributed throughout Iran (Fig. 1;Supplementary Table 1).
However, tetraploids were more commonly recorded, representing
75% of the populations studied. For each population, all 25 in-
dividuals examined belonged to the same cytotype, with no cases of
both diploid and tetraploid cytotypes co-occurring within any
population studied. The species is distributed at a wide range of
latitudes and altitudes (Fig. 1). Its distribution with increasing lati-
tude is negatively associated with increasing altitudes, but this
pattern of geographical distribution regarding to altitude and lati-
tude ranges is unrelated to different ploidy levels (Supplementary
Fig. 1).
The PCA of the genetic-fingerprinting data also generated two
groups (see Supplementary Table 1). Each of these DNA-based
groups included both diploid and tetraploid populations and,
Table 1
Anatomical differences in leaf anatomy and phytochemistry between diploid and tetraploid races and DNA-based groupings of Artemisia sieberi.
Plant characteristics 2n¼2x¼18 2n¼4x¼36 Fvalue Pvalue DNA Group1 DNA Group2 Fvalue pvalue
Mean SE Mean SE Mean SE Mean SE
Main vascular bundle (
m
) 186 10.61 202 5.20 2.18 0.15 ns 199.31 6.58 193.48 6.01 0.29 0.59 ns
Blade thickness (
m
) 252 7.66 277 10.4 2.02 0.17 ns 270.84 10.22 269.84 12.66 0 0.96 ns
Cuticle thickness (adaxial) (
m
) 5.42 0.37 6.59 0.35 4.14 0.05* 6.34 0.38 6.12 0.38 0.12 0.73 ns
Cuticle thickness (abaxial) (
m
) 5.26 0.38 6.71 0.42 4.16 0.05* 6.49 0.47 5.94 0.35 0.51 0.48 ns
Palisade parenchyma thickness (adaxial) (
m
) 91.73 6.23 113.48 4.76 6.1 0.019* 105.46 4.90 113.16 7.59 0.7 0.41 ns
Palisade parenchyma thickness (abaxial) (
m
) 83.44 5.29 100.05 4.13 4.76 0.037* 93.23 3.88 101.47 7.59 0.51 0.48 ns
Stomata density (adaxial) (N/mm
2
) 149.51 14.23 107.44 4.12 15.08 0*** 120.30 7.77 114.46 6.01 0.21 0.65 ns
Stomata density (abaxial) (N/mm
2
) 123.33 9.60 94.35 3.52 12.62 0.01** 102.28 5.52 101.40 5.38 0.01 0.93 ns
Stomata length (adaxial) (
m
) 24.693 0.50 28.935 0.69 12.44 0.001*** 27.98 0.82 27.40 0.94 0.19 0.67 ns
Stomata length (abaxial) (
m
) 24.244 0.57 28.78 0.75 12.12 0.001*** 27.91 0.82 26.82 0.64 0.55 0.47 ns
Camphene (%) 2.628 0.71 5.827 0.64 7.63 0.009** 4.36 0.61 6.47 0.94 3.15 0.09 ns
1,8-cineole (%) 5.554 1.74 13.071 1.59 6.88 0.013* 10.13 1.41 13.37 2.85 1.17 0.29 ns
a-thujone (%) 20.42 7.41 5.85 1.65 8.04 0.008** 12.29 3.27 3.53 2 2.69 0.11 ns
Camphor (%) 6.98 2.87 31.51 4.55 9.79 0.004** 23.11 4.50 29.6 8.23 0.57 0.46 ns
Terpinen-4-ol (%) 8.822 3.85 2.878 1.18 4.13 0.05* 3.66 1.43 6.34 3.48 0.78 0.38 ns
Chrysanthemyl acetate (%) 2.531 0.88 1.075 0.28 4.22 0.048* 1.28 0.31 1.90 0.82 0.75 0.39 ns
P<0.05 *; P<0.01 **, P<0.001 ***; P>0.05; ns., df. of polidy level ¼1 and denominator df’¼32; df. of DNA grouping ¼1 and denominator df ¼32.
A. Jalili et al. / Acta Oecologica 53 (2013) 95e101 97
Author's personal copy
hence, the DNA-groupings appear largely independent of ploidy
(Supplementary Fig. 1; Supplementary Table 1). The first DNA-
based group was widespread while the second had a relatively
lower altitudinal distribution (Supplementary Fig. 1).
Leaf anatomy and phytochemistry all differed between the two
cytotypes (Table 1). Leaf cuticles and the palisade mesophyll were
consistently thicker in tetraploids and stomata were larger and at a
lower frequency. The percentages of camphene, 1,8-cineole and
camphor were higher in tetraploids whereas those of
a
-thujone,
terpinen-4-ol and chrysanthemyl acetate were greater in diploids.
There were no significant differences between DNA-based groups
(Table 1).
The interrelationships between the physical and chemical
environment of A. sieberi sites are complex (Fig. 3). Nevertheless,
two main axes of variation were identified, one relating to soil
fertility and structure and one to rainfall and soil potassium and
populations of A. sieberi pattern with these two axes (Fig. 2). Diploid
populations appeared restricted to more sandy, infertile and rela-
tively drier habitats (towards the lower end of PCA axis 1) while
tetraploids occupied a wider ecological spectrum. In contrast, the
partial separation of the DNA-based groupings, each of which in-
cludes both diploids and polyploids, appears to relate to climate.
Group1 is associated with cooler annual mean temperatures
(Fig. 4).
4. Discussion
4.1. Differences in field distribution relating to ploidy and identified
DNA-based groups
It has often been reported that polyploids are more widely
distributed than diploid populations (Levin, 1983; Bayer et al., 1991;
Husband and Schemske, 1998; Lumaret et al., 1987; Soejima et al.,
2001; Soltis et al., 2004; Rivero-Guerra, 2008; Lo, 2008) and
many authors have proposed that polyploids have radiated and
expanded more successfully than diploids and play major role in
the wider distribution (Ehrendorfer, 1980; Brochmann et al., 2004;
Garcia et al., 2006). The greater abundance and wider geographical
distribution of tetraploid populations of A. sieberi, and the absence
of mixed diploid-tetraploid populations (Fig. 1) are consistent with
the greater ‘success’of polyploids.
The differences between diploids and polyploids may also
extend to the quality of the habitat. Although Pellicer et al. (2007)
linked polyploidy with extreme habitats, Valles and Torrell
(2001a) found that the widespread Artemisia species in the desert
zones of Uzbekistan were tetraploids whereas more chronically-
restricted species were diploids and the conclusions of Raabova
et al. (2008) were similar. In our study, also, diploid populations
were restricted to nutritionally-impoverished and more dry soils
(Fig. 2).
Some studies indicate that polyploid Artemisia species are
distributed in higher mountains (Valles and Torrell, 2001a) and
high altitudes or in arid lands (Valles et al., 2005) while, four diploid
species of Isoetes are found at high and the other six polyploid
species occur at low altitude regions (Liu et al., 2004). Moreover,
there may be no clear altitudinal and latitudinal separation of
diploid and tetraploid populations (Johnson et al., 2001) and this is
the situation in the current study (see Fig. 1;Suppl. Fig. 1). Thus,
while ploidy does effect an ecological separation of populations for
A. sieberi, it does not effect a climatic one. In this context, the DNA-
based groups, which differ in the temperature of their localities
(Fig. 3), and appear uncoupled from ploidy (see Fig. 1;Suppl. Fig. 1),
may be key to understanding the missing climatic dimension to the
distribution of A. sieberi.
4.2. Towards an interpretation of ecological differences between
populations
Ecological differences between populations are not necessarily
solely a direct consequence of qualitative differences in genetic
composition and heterozygosity. For example, a doubling in chro-
mosome number initially results in an increased genome size, and,
therefore, in cell size and cell cycle length (see Bennett, 1987;
Bennett and Leitch, 2005;
Símová and Herben, 2012). This
increased genome size has important ecological implications in its
own right. Because cells are larger in recently-formed polyploids,
potentially all cells are larger and, in particular, stomatal size is
increased and density decreased in tetraploids (see Byrne et al.,
1981; Cohen and Yao, 1996; Romero-Aranda et al., 1997;Stupar
et al., 2007; Hodgson et al., 2010). Consistent with this, larger
cells in a variety of leaf tissues and lower stomatal densities were
regularly found in tetraploid A. sieberi (Table 1). The effects of these
morphological and anatomical changes on photosynthesis are
potentially great (see Vyas et al., 2007). In particular, water-use
efficiency is potentially compromised in polyploids since closure
of large stomata is inherently less rapid (Hetherington and
Woodward, 2003). Consistent with this theoretically-postulated
reduced water-use efficiency in polyploids, only diploid pop-
ulations were found on (freely-drained) sandy soils in areas of low
rainfall whereas tetraploids were largely restricted to more water-
retentive clay soils and/or areas of higher rainfall (Fig. 2).
More direct genetic effects on the ecological characteristics of
populations are more difficult to identify and quantify. For example,
the essential oils of Artemisia vary according to species (Abad et al.,
2012) and in A. sieberi may perhaps play a part in the chemical
defense of plant tissues (Farzaneh et al., 2006; Negahban et al.,
2007). Thus, potentially, essential oils have ecological significance
as well as being under genetic control. Moreover, there are differ-
ences between diploids and tetraploids in essential oil composition
(Table 1). The results are, however, difficult to interpret. We are
uncertain as to the exact functional significance of the essential oils
and the extent to which composition is controlled bygenetic and by
environmental factors. We cannot even be sure whether factors
relating to the larger cell size and longer duration of the cell cycle in
polyploids (see Bennett, 1987; Bennett and Leitch, 2005;
Símová
and Herben, 2012) are involved. Thus, the traits that we have
measured do not illustrate for certain that qualitative genetic
changes associated with polyploidy affect the ecological
Fig. 2. Pattern of distribution of Artemisia sieberi populations with different ploidy
level (2n¼2x ¼18, 2 n¼4x¼36) based on Principal Component Analysis using plant
chemistry and anatomical characteristics.
A. Jalili et al. / Acta Oecologica 53 (2013) 95e10198
Author's personal copy
characteristics of A. sieberi. The correlation between climatic dis-
tribution and DNA-based groups suggests the existence of
genetically-determined ecotypes but this separation is unrelated to
ploidy (see Fig. 1;Suppl. Fig. 1). Again, its mechanistic origin is
obscure. To date, there are no simple easily-measured traits for
assessing the functional origins of climatic restriction (Cornelissen
et al., 2003).
4.3. Conclusions and future prospects
In this study we provide a partial view of the ecological signif-
icance of polyploidy. Probably because changes in size are amongst
the easiest plant attributes to detect and interpret, our most
striking evidence for an ecological impact of polyploidy relates to
cell size. It will be important in future work to directly measure its
likely determinant, genome size, for diploid and tetraploid pop-
ulations of A. sieberi and to look at water-use efficiency in the two
cytotypes in relation to stomatal characteristics. Perhaps,
polyploid-formation is largely restricted to habitats that are more
mesic than those exploited by their parental diploids. Additionally,
the disproportionate increase in the length of the cell cycle asso-
ciated with a larger genome might have been expected to affect the
phenology. Large genomes predispose species to exhibit cool-
season growth (see Grime and Mowforth, 1982; Grime et al.,
1985; Bennett, 1987; Hodgson et al., 2010; Veselý et al., 2012;
McIntyre, 2012) and the possibility that tetraploids populations of
A. sieberi have a greater tendency for cool-season growth than
diploids also requires study.
Further investigations are needed to elucidate the genetic con-
sequences of polyploidy and the evolutionary origin of the DNA-
based groups. Equally, much future work will centre on the
impact of ecological differences between diploid and tetraploid
populations of the canopy dominant, A. sieberi upon ecosystem
processes. We will pay particular attention to the biodiversity,
functional characteristics and conservation value of the species
with which different cytotypes and DNA-based groups of A. sieberi
are associated and will use this information to inform Iranian
conservation policy.
Fig. 3. Interrelationships between environmental factors in Artemisia sieberi habitats. (A) Soil chemistry and soil structure, (B) soil chemistry and climate.
A. Jalili et al. / Acta Oecologica 53 (2013) 95e101 99
Author's personal copy
Acknowledgments
This study was carried out in the Research Institute of Forests
and Rangelands (RIFR) and supported by Tehran and Payamenoor
Universities.
Appendix A. Supplementary data
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.actao.2013.09.008.
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