Abstract
Observations from modern communities and fossil diatom assemblages from Lake Tanganyika and Lake Malawi were analyzed to explore species richness in the genus Afrocymbella. Modern samples were collected along the shores of both lakes and from open water sites. Fossil assemblages were analyzed from two existing cores collected near the central basins of both lakes, spanning back to the late Pleistocene. We document seven previously described Afrocymbella species, namely A. muellerii, A. beccarii, A. brunii, A. gracilis, A. kociolekii, A. rossii, and A. tanganyikae. We also encountered five Afrocymbella species (A. symmetrica sp. nov., A. nyassae sp. nov., A. delphinea sp. nov., A. cocquytiana sp. nov., and A. gibba sp. nov.) in both modern samples and fossil assemblages that did not fit any existing species and are here described as new to science.
References
<p>Agardh, C.A. (1830) <em>Conspectus criticus diatomacearum</em>. Part 1. Lundae: Literis Berlingianus. pp. 1–16.</p>
<p>Battarbee, R.W. (2003) Diatom analysis. <em>In</em>: Berglund, B.E. & Ralska-Jasiewiczowa, M. (Eds.) <em>Handbook of Holocene palaeoecology and palaeohydrology</em>. Blackburn Press, Caldwell, NJ. pp. 527–570.</p>
<p>Bosworth, V., Felton, A., Wetter, L. & Russell, J. (2004) Paleoclimatic reconstruction based upon a sediment core from the Kalya region, Lake Tanganyika, East Africa. <em>Nyanza Project Annual Report</em> 2004.</p>
<p>Cocquyt, C. (1998) <em>Diatoms from the Northern Basin of Lake Tanganyika</em>. J. Cramer, Berlin - Stuttgart. 274 pp.</p>
<p>Cocquyt, C. (2000) Biogeography and species diversity of diatoms in the Northern Basin of Lake Tanganyika. <em>Advances in Ecological Research</em> 31: 125–150.</p>
<p>Cocquyt, C. & Ryken, E. (2016) <em>Afrocymbella barkeri</em> <em>sp. nov.</em> (Bacillariophyta), a common phytoplankton component of Lake Challa, a deep crater lake in East Africa. <em>European Journal of Phycology</em> 51: 217–225. https://doi.org/10.1080/09670262.2015.1126766</p>
<p>Cohen, A.S., Lezzar, K.E., Cole, J., Dettman, D., Ellis, G.S., Gonneea, M.E., Plisnier, P.D., Langenberg, V., Blaauw, M. & Zilifi, D. (2006) Late Holocene linkages between decade-century scale climate variability and productivity at Lake Tanganyika, Africa. <em>Journal of Paleolimnology</em> 36: 189–209. https://doi.org/10.1007/s10933-006-9004-y</p>
<p>Cohen, A.S., Stone, J.R., Beuning, K.R.M., Park, L.E., Reinthal, P.N., Dettman, D., Scholz, C.A., Johnson, T.C., King, J.W., Talbot, M.R., Brown, E.T. & Ivory, S.J. (2007) Ecological consequences of early Late Pleistocene megadroughts in tropical Africa. <em>Proceedings of the National Academy of Sciences</em> 104: 16422–16427.</p>
<p>Ehrenberg, C.G. (1832) Über die Entwickelung und Lebensdauer der Infusionsthiere; nebst ferneren Beiträgen zu einer Vergleichung ihrer organischen Systeme. <em>Abhandlungen der Königlichen Akademie Wissenschaften zu Berlin, Physikalische Klasse</em> 1831: 1–154.</p>
<p>Ivory, S.J., Blome, M.W., McGlue, M.M., King, J.W., Cohen, A.S. & Cole, J.E. (2016) Environmental change explains cichlid adaptive radiation at Lake Malawi over the past 1.2 million years. <em>Proceedings of the National Academy of Sciences</em> 113: 11895–11900. https://doi.org/10.1073/pnas.1611028113</p>
<p>Johnson, T.C., Werne, J.P., Brown, E.T., Abbott, A., Berke, M., Steinman, B.A., Halbur, J., Contreras, S., Grosshuesch, S., Deino, A., Scholz, C.A., Lyons, R.P., Schouten, S. & Damsté, J.S.S. (2016) A progressively wetter climate in southern East Africa over the past 1.3 million years. <em>Nature</em> 537: 220–224. https://doi.org/10.1038/nature19065</p>
<p>Kociolek, J.P., Hamsher, S.E., Kulikovskiy, M. & Bramburger, A.J. (2017) Are there species flocks in freshwater diatoms? A review of past reports and a look to the future. <em>Hydrobiologia</em> 792: 17–35. https://doi.org/10.1007/s10750-016-3075-1</p>
<p>Kociolek, J.P. & Stoermer, E.F. (1993) Freshwater gomphonemoid diatom phylogeny: preliminary results. <em>Hydrobiologia</em> 269–270: 31–38. https://doi.org/10.1007/BF00028001</p>
<p>Krammer, K. (2003) <em>Diatoms of Europe: Diatoms of the European Inland Waters and Comparable Habitats. Volume 4: Cymbopleura, Delicata, Navicymbula, Gomphocymbellopsis, Afrocymbella.</em> Lange-Bertalot, H. (Ed.) A.R.G. Gantner Verlag K.G. 530 pp.</p>
<p>Müller, O. (1905) Bacillarien aus dem Nyassalande und einigen benachbarten Gebieten. Dritte Folge. <em>Botanische Jahrbucher fur Systematik</em> 36: 137–206.</p>
<p>Patterson, G. & Kachinjika, O. (1995) Limnology and Phytoplankton Ecology. <em>In</em>: Menz, A. (Ed.) <em>The Fishery Potential and Productivity of the pelagic zone of the Lake Malawi/Niassa</em>. Natural Resources Institute, London. pp. 1–67.</p>
<p>Reichardt, E. (1999) <em>Annotated Diatom Micrographs: Zur Revision der Gattung Gomphonema: Die Arten um G. affine/insigne, G. angustatum/micropus, G. acuminatum sowie gomphonemoide Diatomeen aus dem Oberoligozän in Böhmen</em>. Koeltz, Koenigstein. 203 pp.</p>
<p>Robinson, K. (2004) Preliminary investigation of diatom flora distribution in transitional sediment sequences as a possible indicator of annual to decadal precipitation fluctuations. <em>Nyanza Project Annual Report </em>2004: 3–6.</p>
<p>Ross, R. (1983) Endemism and cosmopolitanism in the diatom flora of the East African great lakes. <em>In</em>: Sims, R.W, Price, J.H. & Whalley, P.E.S. (Eds.) <em>Evolution, time and space: the emergence of the biosphere. Systematics Association Special Volume 23</em>. Academic Press, London, pp. 157–177.</p>
<p>Round, F.E., Crawford, R.M. & Mann, D.G. (1990) <em>The Diatoms: Biology & Morphology of the Genera</em>. Cambridge University Press, Cambridge, U.K. 747 pp.</p>
<p>Salzburger, W., Van Bocxlaer, B. & Cohen, A.S. (2014) Ecology and Evolution of the African Great Lakes and Their Faunas. <em>Annual Review of Ecology, Evolution, and Systematics</em> 45: 519–545. https://doi.org/10.1146/annurev-ecolsys-120213-091804</p>
<p>Scholz, C.A., Cohen, A.S., Johnson, T.C., King, J.W., Talbot, M.R. & Brown, E.T. (2011) Scientific drilling in the Great Rift Valley: The 2005 Lake Malawi Scientific Drilling Project—An overview of the past 145,000years of climate variability in Southern Hemisphere East Africa. <em>Palaeogeography, Palaeoclimatology, Palaeoecology</em> 303: 3–19. https://doi.org/10.1016/j.palaeo.2010.10.030</p>
<p>Shinohara, K., Maruyama, A., Rusuwa, B. & Ohtsuka, T. (2014) Taxonomic revision of three diatoms found in Lake Malawi: <em>Afrocymbella brunii </em>(Fricke) <em>comb. nov.</em>, <em>Afrocymbella rossii</em> (Kociolek & Stoermer) <em>comb. nov.</em>, and <em>Aulacoseira euareolata</em> (O.Müller) <em>comb. nov. et nom. nov.</em> <em>Phycological Research</em> 62: 9–15. https://doi.org/10.1111/pre.12036</p>
<p>Stone, J.R., Westover, K.S. & Cohen, A.S. (2011) Late Pleistocene paleohydrography and diatom paleoecology of the central basin of Lake Malawi, Africa. <em>Palaeogeography, Palaeoclimatology, Palaeoecology</em> 303: 51–70. https://doi.org/10.1016/j.palaeo.2010.01.012</p>
<p>Tierney, J.E., Russell, J.M., Huang, Y., Sinninghe Damsté, J.S., Hopmans, E.C. & Cohen, A.S. (2008) Northern hemisphere controls on tropical southeast African climate during the past 60,000 years. <em>Science</em> 322: 252–255. https://doi.org/10.1126/science.1160485</p>
<p>De Wever, A., Muylaert, K., Van Der Gucht, K., Pirlot, S., Cocquyt, C., Descy, J.P., Plisnier, P.D. & Vyverman, W. (2005) Bacterial community composition in Lake Tanganyika: Vertical and horizontal heterogeneity. <em>Applied and Environmental Microbiology</em> 71: 5029–5037. https://doi.org/10.1128/AEM.71.9.5029-5037.2005</p>
<p>Wolff, C., Haug, G.H., Timmermann, A., Damsté, J.S.S., Brauer, A., Sigman, D.M., Cane, M.A. & Verschuren, D. (2011) Reduced interannual rainfall variability in East Africa during the last ice age. <em>Science</em> 333: 743–748.</p>
<p>Yuretich, R.F. & Cerling, T.E. (1983) Hydrogeochemistry of Lake Turkana, Kenya: Mass balance and mineral reactions in an alkaline lake. <em>Geochimica et Cosmochimica Acta</em> 47: 1099–1109.</p>
<p>Battarbee, R.W. (2003) Diatom analysis. <em>In</em>: Berglund, B.E. & Ralska-Jasiewiczowa, M. (Eds.) <em>Handbook of Holocene palaeoecology and palaeohydrology</em>. Blackburn Press, Caldwell, NJ. pp. 527–570.</p>
<p>Bosworth, V., Felton, A., Wetter, L. & Russell, J. (2004) Paleoclimatic reconstruction based upon a sediment core from the Kalya region, Lake Tanganyika, East Africa. <em>Nyanza Project Annual Report</em> 2004.</p>
<p>Cocquyt, C. (1998) <em>Diatoms from the Northern Basin of Lake Tanganyika</em>. J. Cramer, Berlin - Stuttgart. 274 pp.</p>
<p>Cocquyt, C. (2000) Biogeography and species diversity of diatoms in the Northern Basin of Lake Tanganyika. <em>Advances in Ecological Research</em> 31: 125–150.</p>
<p>Cocquyt, C. & Ryken, E. (2016) <em>Afrocymbella barkeri</em> <em>sp. nov.</em> (Bacillariophyta), a common phytoplankton component of Lake Challa, a deep crater lake in East Africa. <em>European Journal of Phycology</em> 51: 217–225. https://doi.org/10.1080/09670262.2015.1126766</p>
<p>Cohen, A.S., Lezzar, K.E., Cole, J., Dettman, D., Ellis, G.S., Gonneea, M.E., Plisnier, P.D., Langenberg, V., Blaauw, M. & Zilifi, D. (2006) Late Holocene linkages between decade-century scale climate variability and productivity at Lake Tanganyika, Africa. <em>Journal of Paleolimnology</em> 36: 189–209. https://doi.org/10.1007/s10933-006-9004-y</p>
<p>Cohen, A.S., Stone, J.R., Beuning, K.R.M., Park, L.E., Reinthal, P.N., Dettman, D., Scholz, C.A., Johnson, T.C., King, J.W., Talbot, M.R., Brown, E.T. & Ivory, S.J. (2007) Ecological consequences of early Late Pleistocene megadroughts in tropical Africa. <em>Proceedings of the National Academy of Sciences</em> 104: 16422–16427.</p>
<p>Ehrenberg, C.G. (1832) Über die Entwickelung und Lebensdauer der Infusionsthiere; nebst ferneren Beiträgen zu einer Vergleichung ihrer organischen Systeme. <em>Abhandlungen der Königlichen Akademie Wissenschaften zu Berlin, Physikalische Klasse</em> 1831: 1–154.</p>
<p>Ivory, S.J., Blome, M.W., McGlue, M.M., King, J.W., Cohen, A.S. & Cole, J.E. (2016) Environmental change explains cichlid adaptive radiation at Lake Malawi over the past 1.2 million years. <em>Proceedings of the National Academy of Sciences</em> 113: 11895–11900. https://doi.org/10.1073/pnas.1611028113</p>
<p>Johnson, T.C., Werne, J.P., Brown, E.T., Abbott, A., Berke, M., Steinman, B.A., Halbur, J., Contreras, S., Grosshuesch, S., Deino, A., Scholz, C.A., Lyons, R.P., Schouten, S. & Damsté, J.S.S. (2016) A progressively wetter climate in southern East Africa over the past 1.3 million years. <em>Nature</em> 537: 220–224. https://doi.org/10.1038/nature19065</p>
<p>Kociolek, J.P., Hamsher, S.E., Kulikovskiy, M. & Bramburger, A.J. (2017) Are there species flocks in freshwater diatoms? A review of past reports and a look to the future. <em>Hydrobiologia</em> 792: 17–35. https://doi.org/10.1007/s10750-016-3075-1</p>
<p>Kociolek, J.P. & Stoermer, E.F. (1993) Freshwater gomphonemoid diatom phylogeny: preliminary results. <em>Hydrobiologia</em> 269–270: 31–38. https://doi.org/10.1007/BF00028001</p>
<p>Krammer, K. (2003) <em>Diatoms of Europe: Diatoms of the European Inland Waters and Comparable Habitats. Volume 4: Cymbopleura, Delicata, Navicymbula, Gomphocymbellopsis, Afrocymbella.</em> Lange-Bertalot, H. (Ed.) A.R.G. Gantner Verlag K.G. 530 pp.</p>
<p>Müller, O. (1905) Bacillarien aus dem Nyassalande und einigen benachbarten Gebieten. Dritte Folge. <em>Botanische Jahrbucher fur Systematik</em> 36: 137–206.</p>
<p>Patterson, G. & Kachinjika, O. (1995) Limnology and Phytoplankton Ecology. <em>In</em>: Menz, A. (Ed.) <em>The Fishery Potential and Productivity of the pelagic zone of the Lake Malawi/Niassa</em>. Natural Resources Institute, London. pp. 1–67.</p>
<p>Reichardt, E. (1999) <em>Annotated Diatom Micrographs: Zur Revision der Gattung Gomphonema: Die Arten um G. affine/insigne, G. angustatum/micropus, G. acuminatum sowie gomphonemoide Diatomeen aus dem Oberoligozän in Böhmen</em>. Koeltz, Koenigstein. 203 pp.</p>
<p>Robinson, K. (2004) Preliminary investigation of diatom flora distribution in transitional sediment sequences as a possible indicator of annual to decadal precipitation fluctuations. <em>Nyanza Project Annual Report </em>2004: 3–6.</p>
<p>Ross, R. (1983) Endemism and cosmopolitanism in the diatom flora of the East African great lakes. <em>In</em>: Sims, R.W, Price, J.H. & Whalley, P.E.S. (Eds.) <em>Evolution, time and space: the emergence of the biosphere. Systematics Association Special Volume 23</em>. Academic Press, London, pp. 157–177.</p>
<p>Round, F.E., Crawford, R.M. & Mann, D.G. (1990) <em>The Diatoms: Biology & Morphology of the Genera</em>. Cambridge University Press, Cambridge, U.K. 747 pp.</p>
<p>Salzburger, W., Van Bocxlaer, B. & Cohen, A.S. (2014) Ecology and Evolution of the African Great Lakes and Their Faunas. <em>Annual Review of Ecology, Evolution, and Systematics</em> 45: 519–545. https://doi.org/10.1146/annurev-ecolsys-120213-091804</p>
<p>Scholz, C.A., Cohen, A.S., Johnson, T.C., King, J.W., Talbot, M.R. & Brown, E.T. (2011) Scientific drilling in the Great Rift Valley: The 2005 Lake Malawi Scientific Drilling Project—An overview of the past 145,000years of climate variability in Southern Hemisphere East Africa. <em>Palaeogeography, Palaeoclimatology, Palaeoecology</em> 303: 3–19. https://doi.org/10.1016/j.palaeo.2010.10.030</p>
<p>Shinohara, K., Maruyama, A., Rusuwa, B. & Ohtsuka, T. (2014) Taxonomic revision of three diatoms found in Lake Malawi: <em>Afrocymbella brunii </em>(Fricke) <em>comb. nov.</em>, <em>Afrocymbella rossii</em> (Kociolek & Stoermer) <em>comb. nov.</em>, and <em>Aulacoseira euareolata</em> (O.Müller) <em>comb. nov. et nom. nov.</em> <em>Phycological Research</em> 62: 9–15. https://doi.org/10.1111/pre.12036</p>
<p>Stone, J.R., Westover, K.S. & Cohen, A.S. (2011) Late Pleistocene paleohydrography and diatom paleoecology of the central basin of Lake Malawi, Africa. <em>Palaeogeography, Palaeoclimatology, Palaeoecology</em> 303: 51–70. https://doi.org/10.1016/j.palaeo.2010.01.012</p>
<p>Tierney, J.E., Russell, J.M., Huang, Y., Sinninghe Damsté, J.S., Hopmans, E.C. & Cohen, A.S. (2008) Northern hemisphere controls on tropical southeast African climate during the past 60,000 years. <em>Science</em> 322: 252–255. https://doi.org/10.1126/science.1160485</p>
<p>De Wever, A., Muylaert, K., Van Der Gucht, K., Pirlot, S., Cocquyt, C., Descy, J.P., Plisnier, P.D. & Vyverman, W. (2005) Bacterial community composition in Lake Tanganyika: Vertical and horizontal heterogeneity. <em>Applied and Environmental Microbiology</em> 71: 5029–5037. https://doi.org/10.1128/AEM.71.9.5029-5037.2005</p>
<p>Wolff, C., Haug, G.H., Timmermann, A., Damsté, J.S.S., Brauer, A., Sigman, D.M., Cane, M.A. & Verschuren, D. (2011) Reduced interannual rainfall variability in East Africa during the last ice age. <em>Science</em> 333: 743–748.</p>
<p>Yuretich, R.F. & Cerling, T.E. (1983) Hydrogeochemistry of Lake Turkana, Kenya: Mass balance and mineral reactions in an alkaline lake. <em>Geochimica et Cosmochimica Acta</em> 47: 1099–1109.</p>