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CHAPTER 1 Diversity and ecology of tropical African fungal spores 1.2.3. Palaeoenvironmental reconstructions Using two independent moisture-balance proxies extracted from the Challa sediment record, Verschuren et al. (2009) reconstructed past changes in lake level and rainfall over the past 25,000 years, i.e. from before the Last Glacial Maximum (LGM) to the present. This showed that in this equatorial region with bimodal seasonal rainfall regime, the intensity of monsoon rainfall varied at half-precessional (~11,500-year) intervals in phase with orbital insolation forcing. On submillennial time scales, hydrological change in equatorial East Africa shows clear signatures of northern high-latitude climate variability, such as an episode of pronounced aridity during the period 13,000-11,700 cal. yr BP, i.e. broadly coeval with the Younger Dryas (YD). Here we compare the stratigraphic record of fossil NPPs in Lake Challa sediments with that of the Branched and Isoprenoid Tetraether (BIT) index (Hopmans et al., 2004), which describes the relative abundance of glycerol dialkyl glycerol tetraether (GDGT) membrane lipids derived from terrestrial soil bacteria versus those derived from aquatic archaea. The BIT record of Lake Challa is interpreted as a moisture-balance proxy mainly reflecting the amount of soil run-off to the lake, which is taken to be influenced primarily by the amount and intensity of monsoon rainfall (Verschuren et al., 2009). On orbital and millennial time scales this inference is supported by the history of Challa lake-level changes, reconstructed from seismic-reflection data (Moernaut et al., 2010). The history of regional temperature change is represented by the TEX 86 -inferred palaeo-temperature reconstruction from Lake Tanganyika in central equatorial Africa (Tierney et al., 2008). The TEX 86 proxy is based on the relative degree of cyclization of isoprenoidal GDGT lipids in the cell membrane of aquatic archaea (Schouten et al., 2002), which is linearly related to temperature (Powers et al., 2004). The evolution of terrestrial vegetation is represented by pollen curves of a selection of common plant taxa (Fig. 1.3), expressed as percentages of the non-local pollen sum and based on total pollen counts between 130 and 2300 grains (on average 694) per sample (Rucina et al., unpublished data). The processing of sediment samples for pollen analysis was identical to that for NPP analysis. 1.3. Results Analysis of 93 depth intervals in the Challa sediment record produced a total of 16,403 distinct NPP specimens, which based on a variety of diagnostic character states could be assigned to 65 different, and well-defined, NPP Types. Sixtyone of these NPPs are fungal spore types, and 42 of these could be linked to known fungal taxa. However, genus and species attribution is not always certain, because many morphological features necessary for proper identification (fruit bodies, asci, conidiophores) were not found. Most of the recovered fungal remains are spores of Ascomycetes and Dematiaceae, taxa known to occur on a variety of substrates. In the following overview, taxonomic descriptions of 61 Types follow the sequence of assigned Type numbers. We include the descriptions and illustrations of 16 Types which are rare in the Challa record and are not included in the stratigraphic diagram (Fig. 1.2) due to their erratic distribution. Little descriptive information about the spores is provided, as the morphological details illustrated in plates I-III can hardly be improved with text. Newly described taxa start with Type number 1001, because most numbers below 1000 have been assigned in earlier studies. The arrangement of Type numbers in this paper is simply sequential and does not infer any relationship between the fossils, unless otherwise indicated. . 46 .
1.3.1. Descriptions and illustrations of African fungal spore types Type HdV-89: Tetraploa aristata Berk. & Broome (van Geel, 1978) (Plate I; Fig. 1.2) . 47 . CHAPTER 1 Diversity and ecology of tropical African fungal spores Conidia verrucose, muriform, 4 columns of cells terminating in septate setiform appendages. Tetraploa aristata is known from many locations worldwide, mainly in subtropical and tropical regions but also in the temperate climatic zone. It is found on a variety of host plants, usually on leaf bases and stems just above the soil (Ellis, 1971; Farr and Rossman, 2009). Type HdV-113: Sporormiella type (van Geel et al., 2003) (Plate I; Fig. 1.2) Ascospores of modern-day Sporormiella species are three- to multi-septate. Each ascospore cell shows an oblique to diagonal germ slit, extending over the entire length of the cell. The ascospores easily split up in separate cells, consequently in the fossil state usually no complete ascospores are found. Identification of Sporormiella and similar genera to the species level is not possible because fruit-bodies, asci and complete ascospores are not available (Ahmed and Cain, 1972). Representatives of the related genus Sporormia lack germ slits, but as the descriptions of Ahmed and Cain (1972) are based on non-germinated spores, a slit may appear after germination, and thus we cannot exclude that our fossil assemblages also include Sporormia (van Geel and Aptroot, 2006). Both Sporormia and Sporormiella are coprophilous fungi, often associated with the dung of large herbivores (Comandini and Rinaldi, 2004). Fossil Sporormiellalike part-spores were distinguished by Davis et al. (1977), Davis and Turner (1986), Davis (1987), Burney et al. (2003), and van Geel et al. (2003). The spores are considered to be a reliable proxy for large herbivore populations occurring near the site of recovery (Burney et al., 2003). Sporormiella type spore cells of variable size (10-16 µm) are common throughout the Lake Challa record. Type HdV-172: Coniochaeta cf. ligniaria (Greville) Massee (van Geel et al., 1983a) (Plate I; Fig. 1.2) Ascospores circular to ellipsoid in outline, 14-20 x 11-15 µm, one-celled, bilaterally flattened, the two flattened dark brown sides have a light brown zone encircling the spore. A germ slit is present along the narrow side in the light brown zone. Jarzen and Elsik (1986) described and illustrated similar spores from river deposits in Zambia as Exesisporites. According to Munk (1957), C. ligniaria is common on dung and wood (see also Farr and Rossman, 2009). Ascospores of this species were found in soil surface samples from a Roman Period settlement site with strong evidence for a high density of domesticated animals (van Geel et al., 2003; van Geel and Aptroot, 2006). This Type is common throughout the Challa record, particularly during the Holocene. Type HdV-1001: Caryospora sp. (Plate I) Ascospores 3-septate, apiculate, bigger cells dark brown, smaller cells light brown, ca. 50 x 28 µm. Caryospora species occur on dead plant material (Barr, 1979). Only one specimen was found in the Challa record (in the full-Glacial section). Type HdV-1004 (Plate I) Fungal spores (conidia?) cylindrical with rounded end cells, 3-5 septate, ca. 24-31 x 10 µm. Small pore in end cells. Rare in the Challa record; all 4 specimens were found in the full-Glacial section.
Page 3: 2011 Thesis submitted in partial fu
Page 7: Voorwoord . 7 . VOORWOORD Aarde, wa
Page 10: DANKWOORD / ACKNOWLEDGEMENTS door K
Page 14 and 15: TABLE OF CONTENTS A.1. Septated spo
Page 17 and 18: Abstract . 17 . ABSTRACT In tropica
Page 19 and 20: Introduction . 19 . INTRODUCTION
Page 21 and 22: . 21 . INTRODUCTION Atlantic Ocean
Page 23 and 24: 1 Figure 2 Global Land-Cover 2000 m
Page 25 and 26: Fig. iv. Rainfall variation in east
Page 27 and 28: . 27 . INTRODUCTION metallurgy main
Page 29 and 30: . 29 . INTRODUCTION analysis of fos
Page 31 and 32: . 31 . INTRODUCTION (iv) illuminate
Page 33 and 34: . 33 . INTRODUCTION Coniochaeta spe
Page 35 and 36: . 35 . INTRODUCTION university pres
Page 37 and 38: . 37 . INTRODUCTION Mumbi, C.T., Ma
Page 39 and 40: . 39 . INTRODUCTION lipids in an eq
Page 41 and 42: . 41 . CHAPTER 1 Diversity and ecol
Page 43 and 44: Equator b 0° Altitude (m) a >3000
Page 45: . 45 . CHAPTER 1 Diversity and ecol
Page 49 and 50: Type HdV-1005: Brachydesmiella sp.
Page 51 and 52: Type HdV-1020 (Plate II) . 51 . CHA
Page 55 and 56: Type HdV-1051 (Plate III) . 55 . CH
Page 63 and 64: RefeRences . 63 . CHAPTER 1 Diversi
Page 69: . 69 . CHAPTER 1 Diversity and ecol
Page 72 and 73: CHAPTER 2 Modern non-pollen palynom
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CHAPTER 2 Modern non-pollen palynom
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CHAPTER 3 Effects of Land use on th
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CHAPTER 4 Validation of non-pollen
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General discussion and conclusion .
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. 189 . GENERAL DISCUSSION AND CONC
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SAMENVATTING beperkingen (i.v.m. de
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APPENDICES Appendix I. Raw NPP data
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APPENDICES Mahuhura Kitere Katanda
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APPENDICES Appendix II. Raw NPP dat
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APPENDICES L. Chibwera Identificati
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APPENDICES L. Chibwera Identificati
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APPENDICES Appendix III. Raw NPP da
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APPENDICES L. Kanymukali Identifica
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APPENDICES L. Kanymukali Identifica
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Photograph by Bob Rumes Front cover
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