Evaluating the effects of changing global climate on amphibian functional groups of southern Africa: an ecophysiology modelling approach
| dc.contributor.advisor | Measey, John | en_ZA |
| dc.contributor.author | Mokhatla, Mohlamatsane McDonald | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology. | en_ZA |
| dc.date.accessioned | 2018-09-18T09:51:03Z | |
| dc.date.accessioned | 2018-12-10T06:34:49Z | |
| dc.date.available | 2018-09-18T09:51:03Z | |
| dc.date.available | 2018-12-10T06:34:49Z | |
| dc.date.issued | 2018-12 | |
| dc.description | Thesis (PhD)--Stellenbosch University, 2018. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: Global climate change is suggested to be one of the leading threats to anuran diversity by the end of the century. This is largely because, compared to other vertebrates, anurans have characteristically small distribution ranges and limited dispersal abilities, making them particularly vulnerable to climate change. To predict how climatic changes may impact species, biologists have used correlative-based species distribution models (SDMs). However, correlative-based SDMs have been criticised for their simplistic approach of correlating known distributions with climatic variables, and thus not accounting for other process-based variables that determine distributions such as physiology, performance and morphology. Using a multi-disciplinary approach, the aim of this study is to synergise data from multiple lines of evidence and incorporate them into SDMs to aid in accurately predicting the responses of southern African amphibians with different life-history traits to climate change. In chapter two, I used correlative-based SDMs to determine the impact of past (LGM: Last Glacial Maximum, HGM: Holocene Glacial Minimum) and future (2080) climate change on species distribution ranges of 37, narrowly distributed Cape Floristic Region (CFR) anuran fauna. I found that the biotic velocity at which the CFR anuran community is expected to shift North and East far exceeds historical rates. These models further suggest that the CFR anuran community has already lost ≈ 56% of suitable climate space since the LGM and this is expected to accelerate under future emission scenarios. Chapter three assessed the impacts of climate change on the distribution ranges of three widely distributed anuran species with different ecological specialisations: Xenopus laevis, Amietia delalandii and Sclerophrys capensis. Although all three species have lost suitable climate since the LGM, the models further suggest that A. delalandii is expected to gain suitable climate space by 2080, at least under two GCMs namely, CCSM (25%) and MPI-ESM (7%), while S. capensis and X. laevis are expected to lose suitable climate space by 2080. In chapter four, I examined how changes in ambient temperature (Ta) and body mass (Mb) affect body temperature (Tb), standard metabolic rates (SMR) and evaporative water loss (EWL). I found that Tb, whole-animal EWL and whole-animal SMR increased with an increase in temperature. Body temperature increased with an increase in Mb in A. delalandii and S. capensis but not in X. laevis. Wholeanimal SMR increased with an increase in Mb in S. capensis only. Chapter five examined the impact of temperature on i) burst swimming and hopping (velocity and acceleration) and hoppping endurance (distance and time) in the same three frog species. Here, I show that temperature changes affect thermal reaction norms only in terrestrial performance traits. Furthermore, A. delalandii outperformed X. laevis in both speed and acceleration traits in both burst swimming and hopping experiments, despite X. laevis being adapted to an aquatic lifestyle. Lastly, I implemented ecophysiology models using the results of the temperature-trait relationships obtained in chapter four and five by constructing spatially explicit surface models which were used as input layers in Maxent. Following the same methods as in chapter three, I found that ecophysiology modelling techniques accurately predict current distributions of these widely distributed African anurans. Although species have lost suitable climate space in the past, models predict that A. delalandii will gain thermally suitable space by the year 2080 while X. laevis is also expected to gain suitable thermal space only under MPI-ESM GCM. Sclerophrys capensis is expected to lose suitable climate space in the same period under all GCMs. In conclusion, I showed that although correlative-based SDMs are useful, bottom-up trait-based techniques such as ecophysiology models improves our understanding on how large-scale climate variables affect key physiological traits in shaping what we observe at species distribution level. In addition to biological traits and ecological specialisations, the incorporation of climate variation in modelling processes is also a necessary aspect, given that we have no clear understanding of how climate change will eventually take place. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Een van die grootste bedreigings vir anuran diversiteit teen die einde van die eeu is Klimaatsverandering. Wat anurans anders as ander gewerweldes maak, is hul kenmerkend klein verspreidingsgebiede en beperkte verspreidingsvermoëns. Om te voorspel hoe klimaatsverandering anurans gaan beinvloed, het wetenskaplikes die korrelatiewe-gebaseerde spesieverspreidings modelle (SDMs) gebruik. Tog word hierdie metode gekritiseer vir die simplistiese benadering van korrelasie van bekende verspreidings van klimaat veranderlikes. Die doel van hierdie studie is om met behulp van 'n multi-dissiplinêre benadering, inligting uit verskeie areas (fisiologie, prestasie en morfologie) te inkorporeer in SDMs om te help met ‘n meer akkurate voorspelling vir Suider-Afrikaanse amfibiese diere met verskillende lewens-kenmerke vir klimaatsverandering. Eerstens het ek die SDM metode gebruik om die impak van klimaatsverandering op die verspreidingsgebied van 37 nouverspreide spesies anuran van die Kaap Floristiese Streek vas te stel. Ek het korrelatiewe-SDMs gebruik vir huidige kondisies en dit gebruik op 2 tydperke in die verlede naamlik i) die Laaste Ystydperk Maksimum (LYM) en ii) die Holoseen Ystydperk Minimum (HYM). Ek het ook die metode gebruik om die tydperk tot 2080. My bevinding was dat die biotiese snelheid waarteen die KFS amfibiese gemeenskap na verwagting sal skuif is veel vinniger as historiese verpsreidingsgroei. Hierdie modelle dui verder daarop dat die KFS amfibiese gemeenskap reeds ≈ 56% verloor het van geskikte klimaatruimte sedert die LYT en dit sal na verwagting versnel onder toekomstige scenarios. Proef drie: Met soortgelyke metodes as hierbo, word die impak van klimaatsverandering vasgestel op die verspreidingsgebiede van drie wyd verspreide anuran spesies met verskillende ekologiese agtergronde: Xenopus laevis, Amietia delalandii, en Sclerophrys capensis. Ek het korrelatiewe gebaseerde SDM modelle gebruik vir huidige toestande en vir die LYM en om 2080 te voorspel. Alhoewel al drie spesies geskikte klimaat sedert die LYM verloor het, dui daarop dat A. delalandii sal na verwagting geskikte klimaat ruimte te bykry, ten minste onder twee ASM naamlik CCSM (25%) en MPI-ESM (7%), terwyl S. capensis en X. laevis verwag om geskikte klimaatruimte te verloor tot 2080. Proef vier het ek fisiologiese eksperimente gedoen om die rol van omgewingstemperatuur (Ta) en liggaamsmassa (Mb) op liggaamstemperatuur (Tb), standaard metaboliese tariewe (SMR) en verdamping waterverlies (EWL) te bepaal. Liggaamstemperatuur verhoog met 'n toename in Mb in A. delalandii en S. capensis maar nie in X. laevis. Ek het egter nie 'n beduidende effek gevind van beide Mb en seks op die geheel-dier EWL in al drie spesies. Geheel-dier SMR verhoog met 'n toename in Mb in net S. capensis. Proef vyf dan bepaal ek hoe veranderinge in temperatuur die volgende beïnvloed: i) spring - swem (snelheid en versnelling) en uithouvermoë (afstand en tyd) in verskillende. Ek het gevind daar was beduidende verskille in spesies reaksie norme net in terrestriële prestasie eienskappe. A. delalandii het beter gevaar as X. laevis in beide die spoed en versnelling eienskappe in swem en spring eksperimente, ten spyte daarvan dat X. laevis aangepas is vir akwatiese leefwyse. Sclerophrys capensis het beter gevaar as X. laevis en A. delalandii in spring uithouvermoë proe (afstand en tyd), ten spyte van veranderinge in Ta. Laastens, het ek die resultate gebruik van hierdie temperatuur-eienskap (dit wil sê, fisiologie, prestasie en morfologie) verkry in proef drie en vier in 'n ekofisiologie modellering platform. Hierdie temperatuur-eienskap verhoudings is gebruik om ruimtelik eksplisiete oppervlak modelle te bou wat gebruik word om inset lae tot huidige spesie verspreiding met behulp van Maxent model te bou. Ek het toe hierdie modelle gebruik op verspredings soortgelyk aan ASM as in proef drie. Die resultaat was dat die ekofisiologie modelleringstegnieke die verspreiding van wyd-verspreide Suid-Afrikaanse anurans akkuraat kan voorspel. Van belang is dat die modelle dui daarop dat A. delalandii meer klimaatgeskikteruimte sal verkry teen die jaar 2080, met al ASM ingesluit, terwyl X. laevis ook na verwagting meer geskikteklimaatruimte sal verkry, maar net onder MPI-ESM ASM. Sclerophrys capensis sal na verwagting geskikteklimaat ruimte verloor in dieselfde tydperk onder al die ASM. Ten slotte, Ek het getoon dat, hoewel korrelatiewe SDM's korrek is, onderliggende eienskappe soos ekofisiologie modelle ons begrip verbeter oor hoe grootskaalse klimaatveranderlikes belangrike fisiologiese eienskappe beïnvloed in die vorming van wat ons waarneem op spesieverspreidingsvlak. Benewens biologiese eienskappe en ekologiese spesialisasies, is die inkorporering van klimaatsvariasie in modelleringsprosesse ook 'n noodsaaklike aspek, aangesien ons nie verstaan het hoe klimaatsverandering uiteindelik sal plaasvind nie. | af_ZA |
| dc.description.version | Doctoral | en_ZA |
| dc.format.extent | xiii, 135 leaves (some color), maps (some color) | |
| dc.identifier.uri | http://hdl.handle.net/10019.1/105152 | |
| dc.language.iso | en | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch Univesity | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | Amphibians -- Climatic changes -- Africa, Southern | en_ZA |
| dc.subject | Amphibians -- Biogeography | en_ZA |
| dc.subject | Ecophysiology -- Mathematical models | en_ZA |
| dc.subject | UCTD | en_ZA |
| dc.subject | Amphibian declines -- Africa, Southern | en_ZA |
| dc.title | Evaluating the effects of changing global climate on amphibian functional groups of southern Africa: an ecophysiology modelling approach | en_ZA |
| dc.type | Thesis | en_ZA |