Journal of the Cycad Society of South Africa
ENCEPHALARTOS
Tydskrif van die Broodboom Vereniging van Suid-Afrika
No. 105
October 2011
ISSN 1012-9987
Multiple cones in Eastern Cape species:
Evolutionary considerations.
Philip Rousseau*
The Eastern Cape province of South Africa is host to
one of the largest diversity of Encephalartos species in
Africa. As with most cycad species many of these are endemic or nearly-endemic to the region. Of the 13 species
known to occur in the region eight are thought to form a
species group: Encephalartos arenarius, E. horridus, E.
latifrons, E. lehmannii, E. longifolius, E. trispinosus with
E. princeps somewhat removed. To this effect Dr. Piet
Vorster—in his chapter on Encephalartos in the hugely
influential Cycad Classification: Concepts and recommendations—places species of the region into 5 groups
(Vorster 2004): (1) E. altensteinii (in a group including E.
natalensis and E. transvenosus); (2) E. caffer and E. villosus (in a group including other subterranean species);
(3) E. friderici-guilielmii and E. ghellinckii (in a group
including other narrow leaflet species); (4) E. lehmanii,
E. arenarius, E. latifrons, E. horridus, E. longifolius, E.
trispinosus in a single group while (5) E. princeps is
placed in a group of its own. The first three groups are
clearly distinct and found to not be of close relation to
each other or the other two groups (see Treutlien et al.
2004 who produced a molecular tree outlining relations
in the genus). The last two groups however are clearly
closer too each other based on their appearance and distribution. So much so that the following is found to be
shared among the members of both group’s 4 and 5:
Narrowly endemic too a small part of the Eastern Cape;
lobed and/or waxy blue leaves, long clear petioles; and
a relatively high sterile sporophyll percentage and sarcotesta index (see Grobbelaar 2002). Superficially then the
only difference between groups 4 and 5 is the amount of
cones formed with E. princeps habitually producing multiple, warty cones (Figure 1) while members from group 4
only produce solitary cones. This has been somewhat additionally substantiated in molecular analysis, as E. princeps has been found not to group within group 4 though
always close to them (specifically analysed in Van der
Bank et al. 1998, 2001, but also found in Treutlien et
al. 2004).
Figure 1.—: Encephalartos princeps with 2 female cones.
ARTICLES
This reproductive limitation is an interesting but not
uncommon phenomenon in the plant kingdom and reproductive traits such as this is often very diagnostic for
species groups, for example in flowering plants ovule
numbers as well as ovary chamber number are often employed. It is also interesting in evolutionary terms as a
movement towards or away from single cone production
could shed light on relationships within Encephalartos
and between Encephalartos and other cycad genera.
These traits are able to do so as they are often highly conserved, i.e. unchanged due to environmental conditions
or through evolutionary time. However it would seem that
the trait of single cone production in species of group 4
is not an absolute. Numerous examples are show below
*African Center for DNA Barcoding (ACDB), University of
Johannesburg, Department Botany and Plant Biotechnology.
Contact: [email protected].
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October 2011
No. 105
Figure 2.—: E. lehmanii male with 2 cones.
Figure 3.—: E. horridus with 3, probably male, cones.
Figure 5.—: E. trispinosus with 2 male cones.
Figure 4.—: E. trispinosus with 2 male cones.
Figure 6.—: E. trispinosus with 2 female cones.
(Figures 2-6) including E. lehmanii (Figure 2), E. horridus (Figure 3) and E. trispinosus (Figure 4-6) showing
multiple immature cones produced in cultivation, even
female ones (Figure 6). Females are significant as they
habitually produce fewer cones than their male counterparts (Grobbelaar 2002) and would thus be even more
“resistant” to multiple cone production. According to literature however in nature only single cones are produced
and this is most often the case even in cultivation. A possible explanation for the phenomenon then may be an increase in resources or a decrease in stress allowing plants
in cultivation to produce multiple cones. If this is the case
this could indicate an even closer relationship between
E. princeps and the members of group 4 than previously
thought. Evolutionary speaking though this trait is still of
interest—perhaps even more so. The fact that these species are able to produce multiple cones may indicate an
evolution from a multi-cone bearing ancestor as they still
carry its “evolutionary baggage” allowing them to do so.
Thus the tendency towards single cone production may
be a derived trait, an important clue for understanding
evolution in Encephalartos.
tions might be indicative of. And now at the end of this
article I feel a need to impress upon my fellow society
members the value of doing just that: sharing your knowledge, observations and opinions about cycads. It might
get others thinking and open that all important dialogue
between interested parties which societies such as ours
is founded on.
Figure 1 taken at Kirstenbosch Botanical Garden.
Figures 3–6 taken at the nursery “Cycad World of Innovations”.
References
GROBBELAAR, N. 2002. Cycads—with special reference to the southern African species. Pretoria, South Africa.
TREUTLIEN, J., VORSTER, P. & WINK, M. 2005. Molecular relationships in Encephalartos (Zamiaceae, Cycadales) based on nucleotide sequences of nuclear ITS 1 & 2, rbcL, and genomic ISSR
fingerprinting. Plant Biology 7:1-12.
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To end of I would like to ask the readers if anyone
has seen plants in habitat producing multiple cones male
or female? Or individuals in cultivation of E. longifolius,
E. arenarius and E. latifrons producing multiple cones?
Lastly when I started this article I had no intention of
it taking such a technical and scientific turn, I simply
wanted to share my observation and know whether it was
shared amongst other members. However due to both my
interests and training I kept realising what my observa-
Acknowledgments
VAN DER BANK, F. H., VORSTER, P., VAN DER BANK, M. & WINK, M.
1998. Phylogeny of Encephalartos: Some Eastern Cape Species.
The Botanical Review 70 (2): 250-259.
VAN DER BANK, F.H., WINK, M., VORSTER, P., TREUTLEIN, J.,
BRAND, L., VAN DER BANK, M. & HURTER, J. 2001. Allozyme
and DNA sequence comparisons of nine species of Encephalartos
(Zamiaceae). Biochem Syst Ecol 29 (3):241-266.
VORSTER, P. 2004. Chapter 6: Classification Concepts in Encephalartos (Zamiaceae). In Walters, T. & Osborne, R. (eds.). Cycad
Classification: Concepts and recommendations. CABI Publishing,
Wallingford.
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