The radiation and biogeography of snakes across south-eastern Africa with respect to the evolution of the savanna biome
| dc.contributor.advisor | Tolley, Krystal A. | en_ZA |
| dc.contributor.advisor | Mouton, P. L. N. | en_ZA |
| dc.contributor.author | Engelbrecht, Hanlie M. | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology. | en_ZA |
| dc.date.accessioned | 2017-10-19T10:38:23Z | |
| dc.date.accessioned | 2017-12-11T10:26:17Z | |
| dc.date.available | 2018-06-30T03:00:05Z | |
| dc.date.issued | 2017-12 | |
| dc.description | Thesis (PhD)--Stellenbosch University, 2017. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: The heterogeneous landscape of the African continent was preceded by a pan-African forest that has been transformed by concomitant contractions and expansions of this biome since the Oligocene epoch, to primarily savanna at present. As such, faunal groups that emerged during the Paleogene/Neogene period and have species distributed in both forest and savanna habitat should show a genetic signature of the possible evolutionary impact of these biome developments. Crotaphopeltis and Philothamnus were ideal candidate taxa to investigate the evolutionary impact of these biome developments on widespread African colubrid snakes. Species in these two genera occur throughout sub-Saharan Africa and are associated with either closed (forest), open (e.g. savanna), as well as both habitat types. The main research aim was to investigate synchronised timing and patterns of radiation for Crotaphopeltis and Philothamnus with respect to these African biome developments. Knowledge of the evolutionary relationships for the two genera was needed to construct their biogeographic histories reliably. Therefore, described species of Crotaphopeltis and Philothamnus were investigated for their validity under the Evolutionary Species Concept with an aim to identify cryptic species that are otherwise masked by phenotypic and/or ecological parallels. Newly identified species were used in subsequent analysis of timing of lineage diversification and the reconstruction of ancestral habitat states. The influence of historical environmental conditions on the evolution of the climatic niche of two wide-ranging species in each of the genera, C. hotamboeia and P. angolensis were additionally studied. The climatic distributions of the two species were modelled for contrasting climatic conditions during the Pleistocene period and their ancestral climatic states were reconstructed. Results show that both genera are monophyletic. Up to seven candidate species are recognised within Philothamnus and two within Crotaphopeltis, which provide a basis for future taxonomic revisions. Timing of lineage diversification and associated shifts of species into novel habitats correspond to the historical developments of the forest and savanna biomes, since the Oligocene. Philothamnus showed an ancestral preference toward closed habitat, while the ancestral habitat type for Crotaphopeltis was equivocal between closed and open habitat types. The Miocene epoch signifies a period of increased diversity within both genera. It specifically appears that the climatic oscillations during Early/Mid-Miocene facilitated the evolution of C. hotamboeia as a climatic generalist, whilst the Late-Miocene climatic conditions induced specialisation of P. angolensis in subtropical climate. The research presented here demonstrates that development of habitat throughout the Late Oligocene influenced the radiation patterns of the colubrid snake genera, Crotaphopeltis and Philothamnus. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Die veranderlike landskap van die Afrika-vasteland is voorafgegaan deur 'n pan-Afrika-woud wat deur die aaneenlopende en ossilerende inkrimping en uitbreidings van hierdie biome verander is sedert die Oligoseen-epog, tot hoofsaaklik die huidige savanna. Sodanig kan die diere groepe wat tydens die Paleogene/Neogene periode onstaan het met spesies wat in beide die woud- en savanna habitatte voorkom genetiese kenmerke toon van die moontlike evolusionêre impak van hierdie biome se ontwikkelings. Crotaphopeltis en Philothamnus was ideale kandidaat-taxa om die evolusionêre impak van hierdie verskeie bioom-ontwikkelings op wydverspreide Afrika colubrid-slange te ondersoek. Spesies in hierdie twee genera kom wyd-verspreid in sub-Sahara Afrika voor en word geassosieer met óf beskutte (woud) óf oop (bv. savanna) sowel as albei habitat soorte. Die hoof navorsingsdoel was om gesinkroniseerde tydsberekening en patrone van radiasie vir Crotaphopeltis en Philothamnus met betrekking tot die ontwikkelingsgang van hierdie Afrika-biome te ondersoek. Inligting rakend die evolusionêre verhoudings vir die twee genera was nodig om hul biogeografiese geskiedenisse betroubaar saam te stel. Daarom is reeds beskryfde spesies van Crotaphopeltis en Philothamnus, ondersoek vir hul geldigheid onder die Evolusionêre Spesies Konsep met die doel om kriptiese spesies te identifiseer wat andersins deur fenotipiese en/of ekologiese parallelle verdoesel kan word. Nuut geïdentifiseerde spesies is gebruik in die daaropeenvolgende analise van die tydsberekening van diversifisering en die heropbou van voorouer-habitat toestande. Die invloed van historiese omgewingstoestande op die evolusie van die klimaatsnisse van twee wydverspreide spesies in elk van die genera, C. hotamboeia en P. angolensis, is verder bestudeer. Die klimaatsverspreiding van die twee spesies is gemodelleer vir kontrasterende klimaatstoestande gedurende die Pleistoseen- tydperk en hul voorouer klimaatstoestande is herbou. Resultate toon dat beide genera monofileties is. Soveel as sewe kandidaat spesies word herken binne Philothamnus en twee binne Crotaphopeltis wat 'n basis vorm vir toekomstige taksonomiese hersienings. Die tydsberekeninge van diversifisering en die gepaardgaande verskuiwings van spesies na nuwe habitatte stem ooreen met die historiese ontwikkelinge van die woud en savanna biome, sedert die Oligoseen. Philotamnus toon ‘n voorouer voorkeur vir beskutte habitat tipes, terwyl die voorouer habitat tipe vir Crotaphopeltis ewekansig was tussen beskutte en oop habitatsoorte. Die Mioseen-epog dui op 'n tydperk van toenemende diversiteit binne beide genera. Dit blyk spesifiek dat die klimaat-ossillasies tydens die Vroeë/Middel-Mioseen die evolusie van klimaats-veralgemening fasiliteer het vir C. hotamboeia , terwyl die Laat-Mioseen klimaat spesialisasie van P. angolensis in subtropiese klimaat veroorsaak het. Die navorsing wat hier aangebied word toon dat die habitatsontwikkeling van die die Laat Oligoseen die radiasie patrone van die colubrid-slanggenera, Crotaphopeltis en Philothamnus beïnvloed het. | af_ZA |
| dc.description.version | Doctoral | |
| dc.embargo.terms | 2018-06-30 | |
| dc.format.extent | xii, 94 pages : illustrations, maps | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/102568 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject.lcsh | Snakes -- Africa -- Geographical distribution | en_ZA |
| dc.subject.lcsh | Snakes -- Variation -- Africa | en_ZA |
| dc.subject.lcsh | Genotype-environment interaction | en_ZA |
| dc.subject.lcsh | Philothamnus -- Evolution | en_ZA |
| dc.subject.lcsh | Crotaphopeltis -- Evolution | en_ZA |
| dc.subject.lcsh | Evolutionary genetics | en_ZA |
| dc.subject.lcsh | Reptiles -- Effect of environment on -- Africa | en_ZA |
| dc.subject.lcsh | Savanna ecology -- Africa, Southern -- Africa, Eastern | en_ZA |
| dc.subject.lcsh | Biogeography -- Climatic factors | en_ZA |
| dc.subject.lcsh | Snakes -- Effect of temperature on | en_ZA |
| dc.subject.name | UCTD | en_ZA |
| dc.title | The radiation and biogeography of snakes across south-eastern Africa with respect to the evolution of the savanna biome | en_ZA |
| dc.type | Thesis | en_ZA |