Our national plant, Welwitschia mirabilis, is a unique Namib Desert endemic, occurring only in Namibia and Angola. It is in its own taxonomic family, Welwitschiaceae, with closest relatives in two distantly related families comprising the order Gnetales. Well developed male and female cones are indicative traits of the plant’s gymnosperm heritage, and substantial molecular evidence now confirms this fact, and that the Gnetales are correctly positioned within the Gymnosperm clade (Mundry & Stutzel 2004, Pham & Sinha 2003, Rydin & Fliis 2005, Xi et al. 2013). Based on male cone characters of a limited number of greenhouse plants, Leuenberger (2001) proposed two geographic subspecies of W. mirabilis located in Namibia and Angola respectively, but this has recently been refuted and requires further phylogenetic study (Jacobson et al. In Press).
“Welwitschia”, as it is commonly referred to, is well known for its longevity, with carbon dating suggesting some individuals are 1500-2000 years old (see Henschel & Seely 2000 for specific references). Although it is hard to believe when viewing a mature plant, Welwitschia has only two leaves extending from the central meristem. As the plant grows, the leaves curl up and around the central part of the plant and extend across the ground. Welwitschia has an extensive root system that extends both laterally and vertically (Jacobson et al. 1993) and has long been assumed to be a classic phreatophyte (Di Salvatore et al. 2013). Recent isotopic fog studies suggest that plants growing in the central Namib do not use fog moisture (Soderberg 2010). Despite the extreme aridity of the Namib Desert, Welwitschia is a predominantly C3 plant which uses CAM photosynthesis only in the summer months when cones are being produced (von Willert et al. 2005).
Pollination is achieved primarily by insects (Wetschnig & Depisch 1999) and the female cones bear winged seeds that are dispersed via wind once the cones dry. Seedling recruitment is very rare, however, occurring only in response to rain events in excess of 30 mm (personal observation - K. Jacobson). Plants are found in small isolated populations (e.g. Welwitschia Wash and Hope Mine populations near Gobabeb with <200 plants) to large expansive populations with thousands of plants (e.g. in the Swakop River region). A preliminary assessment found significant levels of genetic variation within and between five geographically discrete populations, and no evidence of inbreeding even in the small southern populations (Jacobson & Lester 2003). This initial study suggested that gene flow, via pollination and seed dispersal, is occurring between populations located 6 km apart, but is less common in populations that are more than 18 km apart.
Insect populations associated with Welwitschia (Henschel & Seely 2000), appear to be localized solely with these plant populations in the Namib landscape but this deserves further study. These insects are also primary agents of dispersal of black Aspergillus species, primarily Aspergillus welwitschiae (Hong et al. 2013), that occur in Welwitschia populations throughout Namibia (Cooper-Driver 2000, Pekarek et al. 2006, Whitaker et al 2004, Whitaker et al. 2008a&b). Ongoing studies suggest that this fungus suppresses seedling recruitment. Despite minimal current recruitment, Welwitschia populations currently range throughout the Namib Desert from Namibe Province in Angola south to the Kuiseb River. The unique and unusual plant has likely survived eons of climatic change in this region. Fossil male cones and pollen have been found in the Brazilian Basin from 114 MYA, when South America and Africa were on the same continent (Dilcher et al. 2005).
The closest Welwitschia population to Gobabeb is located at Welwitschia Wash. The plants at this site have been part of the long-term ecological monitoring project at Gobabeb since 1985. Other sites in the central Namib that are easily accessed from Gobabeb include Hope Mine and the very large populations north and south of the Swakop River in the northern part of the Namib-Naukluft Park.
Recently, members of the NERMU team excavated and transplanted Welwitschia plants that were in the path of a road construction in the mining area in the northern part of the Park. An extensive analysis of root structure was performed and the survival of the plants is currently being monitored in their new locations.
Henschel & Seely (2000) published a comprehensive review and bibliography of Welwitschia research (~250 papers) since Hooker’s description of the plant in 1863. In addition, van Jaarsveld and Pond (2013) have published a beautifully illustrated book documenting the history of discovery and the natural history of Welwitschia, as well as the art and artists that have been inspired by this plant.
- Cooper-Driver GA, Wagner C, Kolberg H. (2000) Patterns of Aspergillus niger var. phoenicis (Corda) Al-Musallam infection in Namibian population of Welwitschia mirabilis Hook. f. J Arid Environ 46: 181-98. http://dx.doi.org/10.1006/jare.2000.0660
- Dilcher DL, Bernardes-De-Oliveira ME, Pons D, Lott TA. (2005) Welwitschiaceae from the lower cretaceous of northeaster Brazil. Am J Bot 92(8): 1294-10. doi: 10.3732/ajb.92.8.1294
- Di Salvatore M Carafa AM, Carratù G. (2013) Growth and Reproductive Phenology of Welwitschia mirabilis Hook. F. The Open Plant Science Journal, 2013, 7, 39-46: http://www.benthamscience.com/open/topsj/articles/V007/39TOPSJ.pdf
- Henschel JR & Seely MK. (2000) Long-term growth of Welwitschia mirabilis, a long lived plant of the Namib Desert (including a bibliography). Plant Ecol 150: 7-26. http://squeeb1134.tripod.com/Welwitschia/HenschelandSeely2000.pdf
- Hong S-B, Lee M, Kim D-H, Varga J, Frisvad JC, et al. (2013) Aspergillus luchuensis, an industrially important black Aspergillus in East Asia. PLoS ONE 8(5): e63769. doi:10.1371/journal.pone.0063769
- Jacobson KM, Jacobson PJ, Miller Jr. OK. (1993) The mycorrhizal status of Welwitschia mirabilis. Mycorrhiza 3(1):13-17. doi:10.1007/BF00213462
- Jacobson KM, Lester E.(2003) A first assessment of genetic variation in Welwitschia mirabilis Hook . J Hered 94(3): 212-17. doi:10.1093/jhered/esg051
- Jacobson NP, Jacobson PJ, van Jaarsveld E., Jacobson K. (In Press). Field evidence from Namibia does not support the designation of two subspecies of Welwitschia mirabilis Hook. Proceedings of the Royal Society of South Africa (schedule for online publication in September 2014). http://dx.doi.org/10.1080/0035919X.2014.950187
- Kellenberger, TW & Kneubuhler M. (2009) Mapping of Welwitschia mirabilis with high resolution satellite imagery in the Namib desert. Geoscience and Remote Sensing Symposium,2009 IEEE International, IGARSS4:366-9. doi: 10.1109/IGARSS.2009.5417389
- Leuenberger, BE. (2001) Welwitschia mirabilis (Welwitschiaceae), male cone characters and a new subspecies. Willdenowia 31:357-381. http://botanischergartenberlin.com/sites/default/files/documents/w31-2Leuenberger.pdf
- McCoy SR, Kuehl JV, Boore JL, Raubeson LA. (2008) The complete plastid genome sequence of Welwitschia mirabilis: an unusually compact plastome with accelerated divergence rates. BMC Evolutionary Biology 8:130. doi:10.1186/1471-2148-8-130
- Mundry M, Stutzel T. (2004) Morphogenesis of the reproductive shoots of Welwitschia mirabilis and Ephedra distachya (Gnetales), and its evolutionary implications. Org Divers Evol 4: 91-08. http://dx.doi.org/10.1016/j.ode.2004.01.002
- Pekarek,E, KM Jacobson, Donovan A. (2006) High levels of genetic variation exist in Aspergillus niger populations infecting Welwitschia mirabilis Hook. Journal of Heredity 97 (3): 270-278.doi: 10.1093/jhered/esj031
- Pham T & Sinha N. (2003) Role of Knox Genes in Shoot Development of Welwitschia mirabilis. International Journal of Plant Sciences Vol. 164, No. 3 pp. 333-343.
- Rydin, C, Friis E.M. (2005). Pollen germination in Welwitschia mirabilis Hook. F.: differences between the polyplicate pollen producing genera of the Gnetales. Grana 44(3):137-141 doi: 10.1080/00173130500230459
- Soderberg, KS (2010) Ph.D. Dissertation: The role of fog in the ecohydrology and biogeochemistry of the Namib Desert. University of Virginia. 200 pages. https://www.researchgate.net/publication/249315072_The_role_of_fog_in_the_ecohydrology_and_biogeochemistry
- Van Jaarsveld EJ, & Pond U. (2013) Uncrowned Monarch of the Namib: Welwitschia Mirabilis Penrock Publications.
- von Willert DJ, Armbrüster N, Drees T, Zaborowski M (2005) Welwitschia mirabilis: CAM or not CAM — what is the answer? Functional Plant Biology 32, 389–395. http://dx.doi.org/10.1071/FP01241
- Wagner RE et al. (2007). Proteomic evaluation of gymnosperm pollination drop proteins indicates highly conserved and complex biological functions Sexual Plant Reproduction 20(4): 181-18. doi: 10.1007/s00497-007-0054-8
- Whitaker C, Berjak P, Kolberg H, Pammenter NW. (2004) Responses to various manipulations, and storage potential, of seeds of the unique desert gymnosperm, Welwitschia mirabilis Hook.fil. South Afr J Bot 70: 621-9. https://www.researchgate.net/publication/258926718_Responses_to_various_manipulations_and_storage_potential
- Whitaker C, Berjak P, Pammenter NW. (2008a). Abnormal morphology of the embryo and seedling of Welwitschia mirabilis, and some observations on seed-associated fungi. South African Journal of Botany 74: 338–340. http://dx.doi.org/10.1016/j.sajb.2007.12.002
- Whitaker C, Pammenter NW, Berjak P. (2008b) Infection of the cones and seeds of Welwitschia mirabilis by Aspergillus niger var. phoenicis in the Namib-Naukluft Park. South Afr J Bot 74: 41-50. http://dx.doi.org/10.1016/j.sajb.2007.08.008
- Xi Z, Rest JS, Davis CC (2013) Phylogenomics and Coalescent Analyses Resolve Extant Seed Plant Relationships. PLoS ONE 8(11): e80870. doi:10.1371/journal.pone.0080870
Gobabeb has initiated a study to investigate correlates of plant health of Welwitschia mirabilis (welwitschia) in the central Namib Desert. Welwitschia is endemic to the central and northern Namib. It is a long-lived plant that has adapted to extreme conditions, with limited water availability among other factors.
However, in spite of these extreme and challenging conditions, it has been able to grow, reproduce and persist here for
thousands of years.
Now it is predicted that a number of accumulating anthropogenic drivers resulting from several developments, including mining, might threaten the survival of the Welwitschia. This study will provide information that can be used to understand Welwitschia biology and conservation and devise better management practices that will ensure the continued survival of this iconic plant.
The study is being led by Dr. Theo Wassenaar of Gobabeb, with Mr. Titus Shuuya as MSc student and Ms. Barbara Curtis of the Polytechnic of Namibia as his supervisor. The project is conducted in collaboration with Prof. Gert Krüger and Dr. Jacques Berner of the Northwest University of South Africa, Prof. Kathy Jacobson of Grinnell College, USA, Dr Mary Seely and Dr. Joh Henschel as associates of Gobabeb, and Ms. Michele Kilbourn Louw and Ms. Angie Kanandjembo of Swakop Uranium.