ENCEPHALARTOS Tydskrif Van Die Broodboom Vereniging Van Suid-Afrika
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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 en- demic 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 recom- mendations—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. vil- losus (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 dis- tribution. 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 sarco- testa index (see Grobbelaar 2002). Superficially then the Figure 1.—: Encephalartos princeps with 2 female cones. only difference between groups 4 and 5 is the amount of cones formed with E. princeps habitually producing mul- tiple, warty cones (Figure 1) while members from group 4 only produce solitary cones. This has been somewhat ad- ditionally substantiated in molecular analysis, as E. prin- ceps 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). This reproductive limitation is an interesting but not uncommon phenomenon in the plant kingdom and re- productive 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 em- ployed. 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 con- served, 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. ARTICLES Contact: [email protected]. Figure 2.—: E. lehmanii male with 2 cones. 22 Encephalartos October 2011 No. 105 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. hor- tions might be indicative of. And now at the end of this ridus (Figure 3) and E. trispinosus (Figure 4-6) showing article I feel a need to impress upon my fellow society multiple immature cones produced in cultivation, even members the value of doing just that: sharing your know- female ones (Figure 6). Females are significant as they ledge, observations and opinions about cycads. It might habitually produce fewer cones than their male counter- get others thinking and open that all important dialogue parts (Grobbelaar 2002) and would thus be even more between interested parties which societies such as ours “resistant” to multiple cone production. According to lit- is founded on. erature however in nature only single cones are produced and this is most often the case even in cultivation. A pos- Acknowledgments sible explanation for the phenomenon then may be an in- crease in resources or a decrease in stress allowing plants Figure 1 taken at Kirstenbosch Botanical Garden. in cultivation to produce multiple cones. If this is the case Figures 3–6 taken at the nursery “Cycad World of Innova- this could indicate an even closer relationship between tions”. E. princeps and the members of group 4 than previously thought. Evolutionary speaking though this trait is still of References interest—perhaps even more so. The fact that these spe- cies are able to produce multiple cones may indicate an GROBBELAAR, N. 2002. Cycads—with special reference to the south- evolution from a multi-cone bearing ancestor as they still ern African species. Pretoria, South Africa. carry its “evolutionary baggage” allowing them to do so. TREUTLIEN, J., VORSTER, P. & WINK, M. 2005. Molecular relation- Thus the tendency towards single cone production may ships in Encephalartos (Zamiaceae, Cycadales) based on nucle- be a derived trait, an important clue for understanding otide sequences of nuclear ITS 1 & 2, rbcL, and genomic ISSR fingerprinting. Plant Biology 7:1-12. evolution in Encephalartos. ARTICLES VAN DER BANK, F. H., VORSTER, P., VAN DER BANK, M. & WINK, M. To end of I would like to ask the readers if anyone 1998. Phylogeny of Encephalartos: Some Eastern Cape Species. The Botanical Review 70 (2): 250-259. has seen plants in habitat producing multiple cones male or female? Or individuals in cultivation of E. longifolius, VAN DER BANK, F.H., WINK, M., VORSTER, P., TREUTLEIN, J., E. arenarius and E. latifrons producing multiple cones? BRAND, L., VAN DER BANK, M. & HURTER, J. 2001. Allozyme and DNA sequence comparisons of nine species of Encephalartos Lastly when I started this article I had no intention of (Zamiaceae). Biochem Syst Ecol 29 (3):241-266. it taking such a technical and scientific turn, I simply VORSTER, P. 2004. Chapter 6: Classification Concepts in Encepha- wanted to share my observation and know whether it was lartos (Zamiaceae). In Walters, T. & Osborne, R. (eds.). Cycad shared amongst other members. However due to both my Classification: Concepts and recommendations. CABI Publishing, interests and training I kept realising what my observa- Wallingford. No. 105 October 2011 Encephalartos 23 .