Phylogeography and thermal physiology of Meroles knoxii (Family: Lacertidae) : relevance for species responses to climate change

Strauss, Paula (2016-12)

Thesis (MSc)--Stellenbosch University, 2016.

Thesis

ENGLISH ABSTRACT: Climate change is considered to be one of the greatest threats to species and ecosystems globally and is likely to contribute to the rapidly increasing number of species extinction. In South Africa, these climatic changes have been noted and are thought to persist. Lizards, as ectotherms, are exceptionally vulnerable to changes in their thermal environments and could face even greater extinction risk if they lack the capacity to behaviourally mediate or rapidly adapt to changing thermal environments. Species distribution models have only recently started incorporating genetic and physiological mechanistic variables to more accurately predict species responses to climate change. This study investigates genetic and physiological traits in order to elucidate genetic patterns and thermal traits that could aid in more accurately predicting the climate change responses of a southern African lacertid lizard. In Chapter 2, I investigated the phylogeographic occurrence of Meroles knoxii along the west coastal margin of southern Africa, with special focus on the southern mesic extent of the distribution range. Phylogeographic and population genetic analyses consistently retrieved three distinct genetic clades (north, central and south) that occur allopatrically on a north-south axis along the coastline. Body size differences occur between the northern and southern clades with the northern xeric clade displaying significantly larger body sizes than the southern mesic clade, suggesting local adaptation to these environments in conjunction with the genetic differentiation observed. The southern clade exhibited no genetic differentiation at a small spatial scale and is thus considered a single population. In Chapter 3, the thermal sensitivity of several traits of M. knoxii was investigated comparing two sites within the southern clade to determine whether and which traits are variable or conserved at a small spatial scale. Selected body temperatures differed significantly between sites. However, these differences are not considered biologically relevant in this study. Critical thermal limits, resting metabolic rate and total evaporative water loss did not differ significantly between sites and is considered a conserved thermal trait at this small spatial scale. In addition, the potential trade-off of thermal performance traits (sprint speed and stamina) was investigated for this ambush predator at one site, Zandvlei Nature Reserve. As expected, M. knoxii displayed optimal sprint speed capacity at high test temperatures and optimal stamina at lower test temperatures. This study aims to illustrate the importance of incorporating ecologically relevant mechanistic variables into species distribution models to more accurately predict species potential responses to future climate change.

AFRIKAANS OPSOMMING: Klimaatsverandering word beskou as een van die grootste bedreigings tot spesies en ekosisteme wêreldwyd en sal moontlik bydra tot „n toenemende aantal spesie-uitsterftes. Hierdie veranderinge is aangeteken in Suid-Afrika en word beskou as voortdurend. Akkedisse, as ektoterme diere, is besonders kwesbaar tot veranderinge in hulle termiese omgewings en kan selfs „n groter uitsterwingsrisiko in die gesig staar as hulle die vermoë ontbreek om deur gedrag aan te pas by snel-veranderende termiese omgewings. Spesieverspreidingsmodelle het eers onlangs begin om genetiese en fisiologiese meganistiese veranderlikes in te sluit om spesieresponse tot klimaatsverandering meer akkuraat te voorspel. Hierdie studie ondersoek genetiese en fisiologiese kenmerke om genetiese patrone en termiese karaktereienskappe toe te lig, wat kan bydra tot meer akkurate voorspellings van die reaksies van „n Suid-Afrikaanse sandakkedis ten opsigte van klimaatsverandering. Hoofstuk 2 ondersoek die filogeografiese verspreiding van Meroles knoxii aan die weskus van suidelike Afrika, met spesifieke fokus op die suidelike nat-omgewingsomvang van die verspreidingsgebied. Filogeografiese- en bevolkingsgenetika-analise toon konsekwent drie unieke genetiese klades (noord, sentraal en suid) wat allopatries voorkom op 'n noord-suid-as langs die kuslyn. Verskille in liggaamsgroote kom voor tussen die noordelike en suidelike klades, waar die noordelike droë-omgewingsklade beduidend groter liggame toon in vergelyking met die suidelike nat-omgewingsklade. Dit dui op plaaslike aanpassing tot hierdie omgewings in samewerking met die genetiese differensiasie opgemerk. Die suidelike klade toon geen genetiese differensiase op „n klein ruimtelike skaal nie en word dus beskou as „n enkele populasie. In Hoofstuk 3 word die termiese vatbaarheid van verskeie kenmerke van M. knoxii ondersoek. Twee studieterreine binne die suidelike klade word vergelyk om vas te stel of en watter kenmerke veranderlik of behoue is op „n klein ruimtelike vlak. Gekose liggaamstemperature het beduidend verskille tussen studieterreine getoon, alhoewel hierdie verskille word nie as biologies relevant beskou vir hierdie studie nie. Kritiese termiese limiete, rustende metaboliese tempo en algehele waterverdampingsverlies het nie beduidend verskil tussen studieterreine nie en word beskou as „n behoue termiese kenmerke op hierdie klein ruimtelike skaal. Voorts, is die potensiële kompromieë van die termiese werkverrigtings-vermoëns (naelloopspoed en stamina) ook ondersoek vir hierdie lokval roofdier op een van die studieterreine, Zandvlei Natuurreservaat. Soos verwag, toon M. knoxii optimale naelloopspoedkapasiteit by hoë toetstemperature en optimale stamina by laer toets temperature. Hierdie studie poog om te wys dat die insluiting van ekologies-relevante meganistiese veranderlikes in spesieverspreidingsmodelle belangrik is om meer akkurate voorspellings te kan maak met betrekking tot potensiële response tot toekomstige klimaatsverandering.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/100177
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