Bot. Macaronésica 24: 73-85 (2003)
73
CORRELATIONS BETWEEN MORPHOLOGICAL-ANATOMICAL LEAF
CHARACTERISTICS AND ENVIRONMENTAL TRAITS IN SOUTHWEST
AFRICAN SPECIES OF ANDROCYMBIUM (COLCHICACEAE)
N. MEMBRIVES 1, J. PEDROLA-MONFORT1 & J. CAUJAPÉ-CASTELLS2
1
Estació Internacional de Biologia Mediterrània-Jardí Botànic Marimurtra. Passeig Karl Faust, 10. 17300
Blanes. Girona. Apdo. Correos 112. Spain. e-mail: (nuriamem@jazzfree.com and jpedrola@grn.es)
2
Jardín Botánico Canario Viera y Clavijo. Apdo 14 de Tafira Alta. 35017. Las Palmas de Gran Canaria.
Spain. e-mail: (julicaujape@granca.step.es)
Recibido: noviembre 2000
Palabras clave: Androcymbium, Colchicaceae, Sudáfrica, morfología, anatomía, aspectos ambientales,
correlaciones.
Key words: Androcymbium, Colchicaceae, South Africa, morphology, anatomy, environmental traits,
correlations.
SUMMARY
We studied 32 populations belonging to 17 Southwestern African taxa of the genus Androcymbium in
order to explore the relationships between leaf morphological and anatomical variation and environmental characteristics as measured by distribution in two different type velds (Fynbos and Karoo-Karoid
types) and the values of 16 edaphic parameters from 22 soil samples. Our results show that only hydric
disponibility (measured as the amount and distribution of annual rainfall, and the water retention capacity) correlates significantly with morphological leaf characteristics in Androcymbium. We detected no
significant correlations between pairwise combinations of anatomical traits and climatic or edaphic
parameters. These results conform to the hypothesis that the diversification of Southwestern African
species of Androcymbium, has been mainly influenced by the arid gradient that already existed when
these species began to diversify in the Late Miocene. Thus, they seem to agree with the hypothesis of
Stebbins that predicts relatively rapid plant evolution in arid to semiarid regions. Because solely some
combinations between characteristics related to aridity and morphological traits are significantly correlated, our results reflect only partially Axelrod and Raven's suggestion that the specific diversity in South
Africa is a consequence of climatic and edaphic fragmentation.
RESUMEN
Se estudiaron 32 poblaciones pertenecientes a 17 taxones del género Androcymbium distribuidas
en Sudáfrica Occidental con el objetivo de explorar las relaciones entre características morfológicas y
anatómicas foliares y características ambientales medidas según la distribución en dos tipos de vegeISSN 0211-7150
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N. MEMBRIVES, J. PEDROLA-MONFORT & J. CAUJAPÉ-CASTELLS
tación diferentes (Fynbos y Karoo-tipos karoides) y los valores de 16 parámetros edáficos procedentes
de 22 muestras de suelos. Los resultados obtenidos mostraron que solamente la disponibilidad hídrica
(medida a partir de la cantidad y distribución de las lluvias anuales, y de la capacidad de retención de
agua) se correlaciona significativamente con las características morfológicas de las hojas en Androcymbium. Respecto a los caracteres anatómicos, no se observaron correlaciones significativas con
parámetros climáticos o edáficos. Estos resultados sugieren que la diversificación de las especies de
Androcymbium en Sudáfrica Occidental ha estado condicionada principalmente por el gradiente de
aridez desde el inicio de su especiación a finales del Mioceno. Estos resultados estan de acuerdo con
la hipótesis de Stebbins que sostiene una rápida evolución de las especies vegetales en regiones
áridas y semiáridas. Nuestros resultados reflejan sólo parcialmente la hipótesis de Axelrod y Raven que
sugiere que la diversidad específica en Sudáfrica es una consecuencia de la fragmentación climática y
edáfica, debido a que únicamente algunas combinaciones entre características relacionadas con la
aridez y aspectos morfológicos están significativamente correlacionadas.
INTRODUCTION
The species of Androcymbium Willd. (Colchicaceae) are geophytes with an annual vegetative cicle that spend the unfavourable period buried like tunicated
corms. The genus includes about 50 species (ARNOLD & WET, 1993; MÜLLERDOBLIES & MÜLLER-DOBLIES, 1984, 1998; PEDROLA-MONFORT et al., 1999a, 1999b,
2000) with a disjunt distribution in arid regions of South Europe and Africa.
The six species in Northern Africa distribute all along the Mediterranean Basin
and in the Canary Islands. The rest of species in the genus (aproximately 45) are
distributed in South Africa, mainly in the Western region. Southwestern African
species display much higher variability levels at the morphological (BAKER, 1974;
KRAUSE, 1920; MEMBRIVES, 2000), seminal (MEMBRIVES et al., 2000a), palynological (MARTÍN et al., 1993; MEMBRIVES, 2000), anatomical (MATEU-ANDRÉS et al.,
1996; MEMBRIVES et al., 2000b), karyological (MARGELÍ et al., 1998; MONTSERRAT et
al., in prep.), allozymatic (MEMBRIVES, 2000), and cpDNA levels (CAUJAPÉCASTELLS et al., 1999), than their Northern African congeners (PEDROLA-MONFORT,
1993; PEDROLA-MONFORT & CAUJAPÉ-CASTELLS, 1996).
STEBBINS (1952 in AXELROD, 1972) suggested that there are several reasons
why plant evolution would be relatively rapid in arid and semiarid regions. First,
local diversity of soils (and other factors) in areas where the moisture is limited has
a greater effect on the flora and vegetation than in regions where moisture is adequate. Second, the regional diversity of semi-arid climates promotes the fragmentation of medium to large-sized populations into smaller units which are isolated
from each other but can exchange genes by occasional migration and establish
populations that may give rise to new species. And third, in dry regions, many different specialized vegetative structures (e.g., reduced leaf size, specialized leaf
covering, deciduous habit, deep root system, swollen trunks or bulbs) can evolve
which may enable plants to withstand periods of severe drought. More recent
works argued that the climatic and edaphic fragmentation that characterizes
Southwest Africa (RICHERSON & LUM, 1980; SHMIDA & WILSON, 1985; BROWN, 1988;
DIAMOND, 1988; WILLIAMSON, 1983; CORNELL, 1993; COWLING et al., 1997) is the
main cause of the specific diversity of its flora and fauna (AXELROD & RAVEN, 1978).
Thus, climatic and edaphic heterogeneity could be one relevant factor to explain
the observed morphological and anatomical differentiation among the species of
CORRELATIONS BETWEEN MORPHOLOGICAL-ANATOMICAL LEAF CHARACTERISTICS…
75
Figure 1.- Geographical distribution of genus Androcymbium according to the veld types (Fynbos and
Karoo-Karoid types). Abbreviations of populations are described in Table 1.
Androcymbium distributed in this area, and between them and their Northern African congeners. The main objective of this work is to explore the possible relationships between the morphological and anatomical variation and environmental (climatic and edaphic) parameters in this geographical circumscription of Androcymbium.
MATERIAL AND METHODS
The material studied comes from 32 populations belonging to 17 Southwestern
African taxa of the genus Androcymbium (Table 1, Fig. 1). These samples are currently in cultivation at the greenhouses of the “Estació Internacional de Biologia
Mediterrània-Jardí Botànic Marimurtra”. Morphological and anatomical characteristics were taken from MEMBRIVES et al. (2000b) and are summarized in Table 2.
Climatic and edaphic parameters- The studied populations are distributed in two
veld types –Fynbos, and Karoo-Karoid- (Table 1, Fig. 1) according to the classification in ACOCKS (1988). Twenty-two soil samples from these populations of Androcymbium (Table 3) were analyzed following the analytic methods described in
HERRERO-BORGOÑON (1992). The measures of pH were taken from a pH-meter
Beckman H-2 with glass electrodes and calomelans. Water retention capacity
N. MEMBRIVES, J. PEDROLA-MONFORT & J. CAUJAPÉ-CASTELLS
76
Table 1.- Populations of Androcymbium analyzed, according to the type veld where inhabit (Fynbos and
Karoo-Karoid types).
Species
Code
Locality
Taxa inhabiting the Fynbos
A. austrocapense U.Müll.-Doblies & D. AUST-GH
3418AC (SIMONSTOWN) Good Hope Cape
Müll.-Doblies
AUST-WP
3418AD (SIMONSTOWN) Whales Point.
Cape Point Reserve
A. capense (L.) K.Krause
CAPE-HO
3318AB (CAPE TOWN) Malmesbury to
Hopefield Road, Km 49
A. eghimocymbion U.Müll.-Doblies & D. EGHI-CI
3218DB (CLANWILLIAM) Piketberg to CiMüll.-Doblies
trusdal Pass
Taxa inhabiting Karoo-Karoid vegetation types
3219AA (WUPPERTAL) Clanwilliam to
A. albanense Schönland subsp. clanwi- ALBA-PK
Wuppertal Road. Km 10
lliamense Pedrola, Membrives & J.
M.Monts
A. bellum Schltr. & K. Krause
BELL-VI
2817DC (VIOOLSDRIFT) Steinkopf to
Vioolsdrift Road, Km 40
A. burchellii Baker subsp. burchellii
BURC-HX
3319BC (WORCESTER) Worcester to
Towsrivier Road.
A. burchellii Baker subsp. pulchrum Pe- PULC-CA
3119DA (CALVINIA) Calvinia to Ceres Road,
drola, Membrives, J. M. Monts & Caujapé
7 km turnoff to Kreitzberg
PULC-NI
3118AA (CALVINIA) Wild flower reserve of
Nieuwoudtville
A. circinatum Baker
CIRC-NB
2917DB (SPRINGBOK) Springbok to Nababeep Road, 100 m
CIRC-SB
2917DB (SPRINGBOK) 3 km W of Springbok
A. cuspidatum Baker
CUSP-CA
3119DA (CALVINIA) Calvinia to Ceres Road,
7 km turnoff to Kreitzberg
CUSP-MO 3320CD (MONTAGU) Near Montagu-Badskloof. W of the Gorgo
A. dregei C.Presl
DREG-PK
3219AA (WUPPERTAL) Clanwilliam to
Wuppertal Road, Km 28
A. eghimocymbion U. Müll.-Doblies & D. EGHI-PK
3219AA (WUPPERTAL) Clanwilliam to
Müll.-Doblies
Wuppertal Road, Km 28
A. hantamense Schinz
HANT-CA
3119DA (CALVINIA) Calvinia to Ceres Road,
7 km turnoff to Kreitzberg
A. henssenianum U. Müll.-Doblies & D. HENS-EK
2817CC (VIOOLSDRIFT) Eksteenfontein to
Müll.-Doblies
Modderfontein Road
A. huntleyi Pedrola, Membrives, J. M. HUNT-EK1 2917AD (SPRINGBOK) Springbok to Port
Monts & Caujapé-Castells
Nolloth Road, 14 km to Eksteenfontein
HUNT-EK3 2917AD (SPRINGBOK) Springbok to Port
Nolloth Road, 20 km to Eksteenfontein
A. irroratum Schltr. & K. Krause
IRRO-EK
2917AD (SPRINGBOK) Springbok to Port
Nolloth Road, 6 km to Eksteenfontein
IRRO-EK2 2917AD (SPRINGBOK) Springbok to Port
Nolloth, 15 km to Eksteenfontein
IRRO-EK6 2817CC (VIOOLSDRIFT) Eksteenfontein to
Modderfontein Road
IRRO-KA
3018CB (KAMIESBERG) Bitterfontein to
Kliprand Road
IRRO-KW
3118BC (VANRHYNSDORP) Vredental to
Koekenaap Road, 100 m to train station
IRRO-VP
3119AC (CALVINIA) Vanrhynspass
IRRO-VY
3118AD (VANRHYNSDORP) Vrendendal to
CORRELATIONS BETWEEN MORPHOLOGICAL-ANATOMICAL LEAF CHARACTERISTICS…
A. poeltianum U. Müll.-Doblies & D. Müll.- POEL-CO
Doblies
POEL-NB
POEL-ST
A. villosum U. Müll.-Doblies & D. Müll.- VILL-EK
Doblies
VILL-ST
A. walteri Pedrola, Membrives & J. WALT-ST
M.Monts
77
Vanrhynsdorp Road
2917DB (SPRINGBOK) Springbok to Concordia Road
2917DB (SPRINGBOK) Springbok to Nababeep Road, 100 m
2917DC (SPRINGBOK) Steinkopf to Springbok Road, 5 km
2817CC (VIOOLSDRIFT) 1 km S of Eksteenfontein
2917BC (SPRINGBOK) 3 km S of Steinkopf
2917DC (SPRINGBOK) Steinkopf to Springbok Road, 5 km
(WRC) was measured as the percentage of water retained in the soil after the centrifugation of 1000 g of moist sample by capillar ascension. The total percentage of
carbonate was analyzed with a Bernard calcimeter. The percentage of organic
material was measured following the Jackson method, which is based on the oxidation in cold of the organic matter with Potassium bichromate in acid solution. The
surplus of dicromate was calculated with ferric sulphate. The quantity of mineral
nitrogen (the only kind assimilable by plants) was determined by distillation of a soil
extract in KCl 2N and collected with a flask containing a mixture of indicators. This
solution was titrated with sulphuric acid 0.001 N. The amount of assimilable phosphor was evaluated by the Olsen method, and the colorimetric measures were
made with a Zeiss spectrophotometer using a wavelength of 660 mu. The amount
of assimilable potassium was estimated by atomic absortion spectrophotometry.
Cathionic interchange capacity (CIC) was evaluated by the Bower method, with
little modifications. The mechanic analysis consisted of evaluating the soil texture
and the amounts of sand, mud and clay contained in samples with the method of
the Bouyoucos densimeter.
Data analysis.- The differences among pairwise combinations of morphological
and anatomical characteristics and veld types were evaluated using a student-t
test. Associations among morphological and anatomical characteristics and
edaphic parameters were calculated with Pearson's correlation. Qualitative characteristics were coded with numerical values (leaf color: 0=green, 1=glaucous;
leaf margin indument: 0=smooth or with papillaes, 1=hairy; epidermic cells shape:
1=rectangular, 2=romboidal, 3=polygonal; mesophyll cells: 0=undifferentiated,
1=differentiated; section: 1=flat, 2=semi-flat, 3=V-shaped; idyoblasts at leaves:
0=unfrequent, 1=frequent; central lamina cells: 0=different in size from the other
cells; 1=similar in size to the other cells). Data analyses were made using the statistic package SPSS/PC+ version 6.1.2 (1995).
RESULTS
a) Correlations between morphological-anatomical characteristics and veld
types
Leaf length, leaf section and the central epidermic cells sizes were the only
three characters that differred significantly between the two veld types where the
examined populations occur (Table 4). The four populations from the Fynbos
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N. MEMBRIVES, J. PEDROLA-MONFORT & J. CAUJAPÉ-CASTELLS
CORRELATIONS BETWEEN MORPHOLOGICAL-ANATOMICAL LEAF CHARACTERISTICS…
79
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N. MEMBRIVES, J. PEDROLA-MONFORT & J. CAUJAPÉ-CASTELLS
studied showed leaves significantly longer than those of populations from the Karoo, a V-shaped section and central cells similar in size to the rest. Androcymbium
capense, that exhibited a flat leaf section and whose central epidermic cells were
larger than the rest was the only exception to this pattern (MEMBRIVES et al.,
2000b). Conversely, species distributed in the Karoo-Karoid types showed flat or
semi-flat section (except for A. bellum, A. dregei and A. eghimocymbion), and central cells larger than the rest (except for A. cuspidatum and A. dregei).
b) Correlations between morphological-anatomical characteristics and edaphic
parameters
Table 5 shows that only the edaphic characteristics related to soil texture
showed significant correlations with most morphological variables studied. Leaf
length and shape (lenght/width) were significantly correlated with the percentage of
clay. Soils with a low percentage of clay were associated with long and lanceolate
leaves, while soils with a high percentage of clay were associated with predominantly short and rounded leaves. Bract length was positively correlated with CIC,
WRC and percentage of mud and clay, and negatively correlated with the percentage of sand. Leaf section was significantly correlated with WRC and percentage of
clay and sand. Flat leaf sections were associated with soils with high WRC, while
V-shaped sections were observed predominantly in low WRC soils. Leaf color
(green or glaucous) and bract shape did not correlate significantly with any of the
edaphic parameters analyzed.
The morphology of the epidermic cells on the adaxial face of the lamina was
positively correlated with CIC, WRC, and with the percentage of clay. Romboidal
and polygonal cell shapes were associated to soils with high CIC, WRC and percentage of clay, whereas rectangular cells were associated with more arid conditions. Adaxial side stomatic indices were significantly correlated only with the percentage of mud and in abaxial side were significantly correlated with percentage of
sand, mud and clay. Presence of hairs in the leaf margin was positively correlated
with CIC, WRC and the percentage of clay, and negatively correlated with the percentage of sand. Mesophyll cell types and the amount of idyoblasts on the leaves
were not significantly correlated with any of the edaphic traits considered.
On the whole, the variability of some morphological and anatomical structures in
genus Androcymbium was only associated with water disponibility (i.e., with the
edaphic characteristics related to the percentage of clay and WRC). Species that
grow in soils with low WRC and low percentage of clay were characterized by long
and linear or linear-lanceolate leaves, rectangular epidermic cells, smooth or with
papillaes at margin, V-shaped leaf section, and short bracts. By contrast, species
that occur in soils with high WRC and high percentage of clays were characterized
by short and ovate leaves, romboidal or polygonal epidermic cells, pluricellular
hairs at the leaf margin, flat leaf section and long bracts.
DISCUSSION
Large amounts of variability in morphological and anatomical characteristics
were described for Southwest African species of Androcymbium, reflecting the
large variation detected in other variables (palynological, flower morphology,
CORRELATIONS BETWEEN MORPHOLOGICAL-ANATOMICAL LEAF CHARACTERISTICS…
81
allozymes or cpDNA RFLPs). By contrast, Northern African species of
Androcymbium showed large variation in some anatomical leaf characteristics,
despite the narrow morphological similarity (MATEU-ANDRÉS et al., 1996).
Some morphological leaf characters of Southwestern African Androcymbium
species seem to evolve associated only with the climatic and edaphic factors related to hydric disponibility (amounts and distribution of annual rainfall, and soil
texture). The two veld types where the studied populations occur are characterized
by different winter rainfall regimes. The Cape Region (dominated by a Fynbos
vegetation) receives more than 250 mm/year (80 % in winter), while the Karoo area
receives less than 300 mm/year (60 % in winter). Androcymbium austrocapense,
A. eghimocymbion, and A. capense occur in the Cape Region and showed bigger
leaf sizes than the rest of species that inhabit in Karoo-Karoid Regions (mean leaf
length values are in Table 2). We detected a significant association between leaf
length and veld types. Therefore, a possible explanation for the bigger leaf size in
Androcymbium species from the Cape Region could be the higher winter rainfall in
this area. The observation that Southeastern African species of Androcymbium
(mainly A. burkei, A. decipiens, A. leistneri, A. longipes, and A. natalense) live in a
regime of much higher winter rainfall and show a leaf size similar to species of the
Fynbos Region agrees with our hypothesis.
Although we can rule out a direct relationship between leaf length and winter
rainfall regime in Androcymbium, other leaf characteristics lend themselves to generalization and fit better theoretical predictions. Species of Androcymbium with a
big leaf surface (ovato-lanceolate shape) inhabit in soils with a high percentage of
clay, while species with little leaf surface (linear or linear-lanceolate shapes) inhabit
in soils with low percentage of clay. Thus, there seems to be an association between leaf surface and soil's texture.
Morphological and anatomical characteristics
t
P
3.87**
0.001
Leaf shape (length/width)
0.38
0.707
Bract length
-0.54
0.591
Leaf length
Bract shape (length/width)
-0.57
0.574
Leaf section
2.33*
0.027
Indument at leaf margin
0.16
0.877
Epidermic cell shapes
-0.10
0.918
Stomatic index at adaxial face
1.51
0.142
Central cell sizes
2.66*
0.013
Mesophyll cell types
1.19
0.242
Frequency of leaf idioblasts
-1.33
0.193
Table 4.- Results of Student's t tests to contrast morphological and anatomical characteristics in species
of Androcymbium from the Fynbos and the Karoo-Karoid vegetation types. **, significant at the 0.01
level. *, significant at the 0.05 level.
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N. MEMBRIVES, J. PEDROLA-MONFORT & J. CAUJAPÉ-CASTELLS
By contrast, bract shape is not significantly correlated with soil texture, and this
might indicate that the characteristics of the bracts could be more influenced by
other factors, probably related to pollination effectiveness. There is a close relation
between levels of allozymic diversity and pollination effectiveness in self-incompatible species of Androcymbium (MEMBRIVES, 2000; MEMBRIVES et al., in prep.).
Previous studies suggested that bract colour and other characteristics related to
the reproductive system (like nectar production and odour) were important to
estimate the allozymic diversity in Southwest African species of Androcymbium.
For instance, A. burchellii subsp. burchellii (with white bracts) has less allozymic
diversity than A. burchellii subsp. pulchrum (with red bracts), even though they
have the same reproduction system. This could be an important insight to consider
that bract characteristics are more conditioned to pollination effectivity than to
environmental conditions.
V-shaped leaves, glaucous colour, and indument in leaf surface and margin are
argued to represent an adaptive strategy to reduce the transpiration in Mediterranean plants. In close agreement, the V-shape of Southwestern African Androcymbium leaves was correlated with low WRC. Similarly, semi-flat shapes and leaf
surfaces covered by waxes (glaucous leaf colour) in Androcymbium species from
Namaqualand (Northern Karoo) could also represent an adaptation to the aridity in
this area. Presence of pluricellular hairs in Androcymbium is associated with soils
that exhibit a high percentage of clay and a high CIC, except for A. cuspidatum
(that lives in high percentage of clay but shows a smooth margin). The presence of
an indument in the leaf margin does not seem to be an adaptation to aridity in Androcymbium, because species with pluricellular hairs occur in clayey soils, which
exhibit high WRC.
According to these observations, hydric disponibility is associated to some morphological and anatomical characteristics in Androcymbium. Recent allozymic diversity studies (MEMBRIVES et al., in prep.) in these populations found that there is
a significant correlation between the aridity gradation described in this region and
the allozymic diversity levels. According to these analyses, the reproductive system
is the variable that most influences allozymic variability in Androcymbium. When
only self-compatible populations were considered, the genetic diversity levels in
populations distributed in the Northern region of Southwestern Africa (where aridity
is more severe) are lower than in Southern species. As the different levels of hydric
disponibility in the diverse habitats of Southwestern Africa seem to influence the
allozymic diversity levels, this edaphic trait could determine inter-specific differences in terms of evolutionary potential.
Southern African species of Androcymbium show a considerable heterogeneity
in mesophyll cell types, which was also shown for their Northern African congeners
(MATEU-ANDRÉS et al., 1996). Given the strikingly contrasting climatic and edaphic
characteristics between the arid regions in Northern and Southern Africa where the
species of Androcymbium inhabit, the mesophyll types do not seem either an
adaptative response to environmental differences or a characteristic of Androcymbium's lineage.
CORRELATIONS BETWEEN MORPHOLOGICAL-ANATOMICAL LEAF CHARACTERISTICS…
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N. MEMBRIVES, J. PEDROLA-MONFORT & J. CAUJAPÉ-CASTELLS
CONCLUSION
Because only the characteristics associated with aridity showed a clear relationship to leaf variability in Androcymbium, our results agree only partially with the
suggestion that the edaphic heterogeneity described in Southwest Africa is the
main cause to explain the high specific diversity in this region (AXELROD & RAVEN,
1978). Some other morphological and anatomical characteristics are correlated
with veld type or water disponibility. The four populations studied that occur in the
Fynbos showed longer leaves with a V-shaped section, except for A. capense,
which showed a flat leaf section. Conversely, species that inhabit the Karoo-Karoid
types, showed shorter leaves, mainly flat or semi-flat in section, except for A. bellum, A. dregei and A. eghimocymbion, with a V-shaped section. Some morphological and anatomical structures were correlated with soil texture in Androcymbium. Species with short ovate leaves, polygonal or rounded epidermic cells, pluricellular hairs at the leaf margin, flat section, and long bracts occur in soils with
high WRC. On the other side, species with long and linear or linear-lanceolate
leaves, rectangular epidermic cells, smooth or papillae margin, V-shaped section,
and short bracts inhabit soils with low WRC. The hydric gradient correlates to
allozymic variability levels in Androcymbium in much the same way as it influences
some morphological and anatomical characteristics. Species that occur in the
Northern region of Southwestern Africa showed lower morphological and genetic
variability values than species distributed in the Southern region and this could be
associated with different evolutionary potentials.
ACKNOWLEDGEMENTS
We thank Juanjo Herrero-Borgoñón for the assistance with the analytic methods
and with the interpretation of the edaphic analyses. Josep Maria Montserrat gave
meaningful suggestions on a previous draft of the manuscript. Amparo Ardanuy
provided for the welfare of the material in cultivation. We thank the Karl Faust
Foundation for the economic support of these investigations.
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