Faculty of Science School of Animal ,Plant and Enviromental Sciences 9707660j McConnachie@ukzn.ac.za / Characteristics comprising an energy budget of Pseudocordylus melanotus melanotus were investigated in terms of limiting factors for the lizard’s distribution, and included measures of thermal biology, metabolism and digestive physiology. Pseudocordylus m. melanotus is rupicolous, is limited to the temperate parts of southern Africa and exhibits adaptations to these environments. The distribution of the lizard was modelled using two different climate envelope modelling techniques, which are discussed in terms of the energy budget and factors limiting the distribution of the lizard. Pseudocordylus m. melanotus exhibits wide thermal tolerances. It can withstand body temperatures (Tb) below freezing, but freezing of body water, which occurs at ca. -5 ºC, is lethal. The lower critical minimum temperature was a surprisingly high measure for an apparently cold-adapted lizard. In the laboratory, the selected body temperature (Tsel) was ca. 30 ºC. In the wild, lizards thermoregulate by shuttling between hot and cold microclimates, modifying body postures and regulating activity times, and select Tbs of ca. 29 ºC in summer and ca. 26 ºC in winter. Energy expenditure was measured over a range of temperatures. MR increases significantly with increasing temperature. Body mass and metabolic rate (MR) were significantly related at 30 ºC only. The lack of significance at other temperatures can be ascribed to the small range of body mass over which measures were made. Energy gain in P. m. melanotus was quantified in terms of prey capture rates and by measuring aspects of digestive physiology. Prey capture attempts were 35 % successful and occurred ca. every 2 h 30 min in the field. Lizards consumed a variety of arthropods, but mainly ate beetles. Digestive rate and appetite increased significantly with increasing temperature. Apparent digestive efficiency (ca. 94 %) and apparent assimilation efficiency (ca. 87.2 %) were not affected by temperature. iii Two energy budgets were calculated; one based mainly on laboratory measures and the other based on the thermal profile of lizard body temperature measured in the field. The laboratory energy budget was approximately half that of the field energy budget. The field energy budget, however, provided a more realistic view of energy expenditure since it covered almost the entire thermal range experienced by lizards. Between 592.53 kJ (field energy budget) and 940.06 kJ (laboratory energy budget) per year is required for a standard 30 g P. m. melanotus to remain in energy balance. This means that lizards need to consume between 73.55 and 116.69 g of mealworms per year, which equates to ca. 740 to 1200 average mealworms. Any energy gained over and above these requirements can be allocated to growth, reproduction and storage. In terms of the lizard’s distribution, it will be excluded from areas where the available thermal environment and prey abundance do not allow the lizard to maintain a positive energy balance. The lizard is apparently at the cold limit of its range, so predicted climate change in southern Africa is unlikely to have a significant effect on the distribution of the lizard. Suitable crevices are essential to the lizard’s survival, particularly during periods of extreme cold when lizards may experience Tbs where they are incapacitated, or effectively ‘comatose’, while in retreats.

In this master thesis, the thermoregulation model proposed by Heath (1970) was updated, integrating the effects of the hydration level on the thermoregulation behavior and the thermal tolerance limits of the Bull Frog, Lithobates catesbeianus (Chapter I). For the thermoregulation behavior the preferred body temperatures (PBT) of hydrated and dehydrated individuals were measured, and as thermal tolerance, the Voluntary Thermal Maximum (VTMax) and the Critical Thermal Maximum (CTMax) were measured in groups of individuals with different hydration levels. Chapter II uses the information collected in chapter I to evaluate the effects of the hydration level on the time to loss the locomotor function of L.catesbeianus individuals exposed to their VTMax. Both chapters indicates that dehydration negatively affects not only the thermoregulation behavior and thermal tolerance of this species, but also the time it takes for individuals to lose their locomotor function when exposed to their VTMax. Our data suggest that dehydration is an important variable that must be included to evaluate the effects of high temperatures and dry conditions on wet skin ectotherms. The temperature-dehydration integration and its effects on these organisms can be included in mechanistic distribution models to update their climate vulnerability under current and future scenarios of climate change / Nesta tese de mestrado foi atualizado o modelo de termorregulação proposto por Heath (1970), integrando os efeitos do nível de hidratação sobre o comportamento de termorregulação e a tolerância térmica da Rã touro, Lithobates catesbeianus (Capitulo I). Para o comportamento de termorregulação foram medidas as temperaturas corpóreas preferenciais (pelas suas siglas em inglês, PBT) de indivíduos hidratados e desidratados, e como tolerância térmica, foram medidas a temperatura voluntária máxima e a temperatura crítica máxima (pelas suas siglas em inglês, VTMax e CTMax, respetivamente) em grupos de indivíduos com diferentes níveis de hidratação. O capítulo II utiliza as informações levantadas no capitulo I para avaliar os efeitos do nível de hidratação sobre o tempo de perda da função locomotora de indivíduos de L.catesbeianus expostos a sua VTMax. O conjunto de dados dos capítulos I e II apontam que a desidratação afeta negativamente não só o comportamento de termorregulação e tolerância térmica desta espécie, mas também o tempo necessário para os indivíduos perderem sua função locomotora ao serem expostos a sua VTMax. Nossos dados sugerem que a desidratação é uma variável importante que deve ser incluída para avaliar os efeitos das altas temperaturas e secas nos ectotermos de pele úmida. A integração temperatura-desidratação e seus efeitos nestes organismos podem ser incluídos em modelos de distribuição mecanicistas para atualizar a vulnerabilidade climática deles nos cenários atuais e futuros das mudanças climáticas

Endotherms living in cold environments must pay the energetic cost of maintaining a high core body temperature. This cost can be potentially alleviated by an important yet often overlooked mechanism: “activity-thermoregulatory heat substitution” (i.e., the use of the heat generated by active skeletal muscles to replace heat that would have been generated by thermogenesis). While substitution has been documented numerous times, the extent of individual variation in substitution has never been quantified. I used a respirometry cage system to repeatedly measure substitution through the concomitant monitoring of metabolic rate (MR) and locomotor activity in 46 female white-footed mice (Peromyscus leucopus) in neutral and cold ambient temperatures. I took a total of 117 measures of substitution by quantifying the difference in the slope of the relationship between MR and locomotor activity speed at two different ambient temperatures. Consistency repeatability (±se) of substitution was 0.313±0.131 – hence, about a third of the variation in substitution occurs at the among-individual level. Including key morphological traits such as trunk surface area, tail mass, heart mass, and body length accounted for the majority of the among-individual variation, suggesting that I have successfully identified traits underlying individual differences in substitution. Overall, my results show that substitution is repeatable and hence might potentially be subject to selection. Future studies should test if substitution conveys fitness advantages directly (by providing energetically cheaper activity which in turn can be utilized for reproduction), or indirectly (i.e., driven by individual differences in morphology). Future studies should also test if there is a trade-off between substitution and dry heat transfer (a thermoregulatory mechanism essential for preventing hyperthermia).

The extensive clearing and modification of natural systems from anthropogenic activities is a pressing global concern. Forest habitats and animal communities within forests are among the most highly impacted, globally. Forest destruction has been repeatedly documented as a driver of biodiversity loss. However, little is known about how animal communities respond when altered landscapes are abandoned and left to regenerate into secondary forests. It is thought that the regrowth of secondary forests may help reverse biodiversity loss by restoring habitats to similar conditions as prior to land conversion. Of the forest cover that remains, over half is secondary forest, and in many countries secondary forest cover has been steadily increasing. Therefore, it is important to understand how and if faunal communities recover during secondary forest regeneration. I combined meta-analytic, field-survey-based, and lab-based experimental techniques to determine how amphibians and reptiles respond to habitat change in general, and secondary forest regeneration on landscapes previously cleared for use as pasture. I addressed five specific questions: 1) what are the effects of habitat alteration on amphibians and reptiles?, 2) what are the effects of secondary forest succession on amphibians and reptiles?, 3) what is the relative importance of stochastic and deterministic effects on community assembly during secondary forest succession?, 4) how do amphibian and reptile species composition, probability of occurrence, and species richness change over the course of secondary forest succession?, and 5) is thermal quality of habitat an important mechanism of species response to secondary forest succession? I found that secondary forest has high conservation value for many amphibian and reptile species, environmental changes associated with secondary forest succession have a significant effect on shaping amphibian and reptile community composition, thermal quality is an important mechanism for species response and that strength of response is mediated by species-specific thermal biology. I also highlight the importance of riparian corridors in maintaining species diversity in modified habitats.

The focus of this dissertation is on bed bug thermal biology. How bed bugs react to heat exposure at the population, behavioral, and physiological levels was explored. The thermal tolerance of different bed bug populations and sublethal effects heat exposure were investigated. The temperatures that cause bed bugs to flee from their harborages was determined using a custom made arena. How bed bug physiology changes after heat exposure was determined using RT-qPCR. Finally, how conspecifics react to bed bugs that have been lethally exposed to heat was determined using still air bioassays.<br>

Mosquitoes are a significant global public health threat, claiming hundreds of thousands of lives annually due to the various pathogens they transmit, which result in diseases including dengue, malaria, and Zika. While various strategies and practices are in place to manage mosquito populations, these methods may be challenged due to a rise in insecticide resistance in some mosquito species, the increasing impacts of global climate change, and invasive species populations. This work presents four distinct projects investigating Culex spp., Ae. albopictus, and Ae. j. japonicus mosquitoes using a range of methods and techniques to bring novel insight into the biology and ecology of these mosquitoes. The first project focuses on the thermal preference and response to thermal cues of three Culex species which vary in host preference and climate of origin. The second project explores the effects of different rearing temperatures and regions of origin on the thermal performance, life-history traits, and nutrient reserves of Ae. albopictus mosquitoes. The third project shifts to the optimization of a species-specific attractive toxic sugar bait (ATSB) trap targeted toward invasive Ae. j. japonicus mosquitoes. The fourth chapter, which is field oriented, focuses on determining the role of elevation on mosquito biodiversity and pathogen prevalence. Collectively, these works explore how mosquitoes interact with their environment to support research-informed decisions in future mosquito control practices. / Master of Science in Life Sciences / Mosquitoes are the deadliest animals in the world, causing over half a million deaths every year. Mosquitoes are disease vectors, meaning they are able to transmit pathogens (such as viruses or bacteria) that cause diseases including malaria and Zika, which can lead to severe illness and death because of the lack of treatment and vaccines, or even access to these in some instances. While there are current strategies in place to reduce mosquito population numbers in areas with high levels of pathogen transmission, we are seeing increasing difficulties in managing and predicting these mosquito populations. Certain mosquito species have become resistant to chemical treatments and the growing impacts of climate change (such as more extreme weather and temperatures) are two factors that are expected to greatly influence mosquito biology and global distribution in the near future, which may expose new human populations to mosquito-borne illnesses. These issues have inspired the following projects to gain more information on how mosquitoes interact with their environment and their hosts, to highlight traits or behaviors that could inform novel mosquito management strategies in the future.

Thesis (PhD)-- Stellenbosch University, 2012. / ENGLISH ABSTRACT: Climate change and biological invasions are major threats to biodiversity. In particular, these threats are predicted to influence terrestrial systems in the sub-Antarctic, where significant ecosystem responses to both have already been seen. In this thesis, the sub-Antarctic Prince Edward Island group is used as a model system in which to investigate key questions relating to climate change and invasive species impacts. The island group comprises two islands, Marion (MI) and Prince Edward (PEI), both of which are experiencing rapid warming, yet have different invasive assemblages and in consequence are experiencing different impacts. Variation in the patterns of invasive species richness and abundance and their underlying causes are matters of considerable ecological and conservation significance. While an increase in thermal energy availability typically results in an increase in species richness, the mechanisms underlying these patterns are poorly understood. In Chapter 2 of this thesis, these relationships are explored for springtails, an important component of the soil fauna on Marion Island. Energy explains a large amount of the spatial variation in indigenous and invasive springtail species richness. Disturbance thresholds and stressful temperatures are more important than increased population sizes in determining this variation in species richness. As both indigenous and invasive springtail species richness and abundance are strongly related to temperature, a warming climate could have far-reaching consequences for these organisms. In particular, invasive species are predicted to be at an advantage relative to indigenous species under warming conditions. One species where this seems especially likely, given its physiological responses to experimental warming and drying, is the large invasive tomocerid, Pogonognathellus flavescens. Determining whether this will be the case depends on understanding the factors underlying its range limits and abundance structure. Moreover, few studies have sought to distinguish the causal basis of abundance structure and range limits, particularly for invasive species. Thus, in Chapter 3, local microclimate variables and physiological tolerances of the invasive springtail, P. flavescens (a habitat generalist), are examined. The results suggest that the species should be widely distributed across a range of habitats on MI. However, the springtail is restricted to indigenous Poa cookii tussock grassland habitats in the southeast. The current range limits are set by dispersal limitation (i.e. contingent absences) whilst abundance structure is a function of variation in soil substrate quality. However, over time, the widening distribution of P. cookii, as a consequence of a major management intervention (the eradication of feral cats), may enable P. flavescens to colonise all suitable areas. In Chapter 4, the focus changes to what has been considered the third major response to climate change, along with range and phenological responses - changing animal body sizes. Body size is one of the most significant and obvious features of animals and is of considerable ecological and physiological importance. A prediction of the temperature-size rule (TSR) is that with warming, body size of the weevil species on both MI and PEI should decline. However, predation by mice of the weevils on MI should fundamentally affect the pattern of such change, causing it to differ from neighbouring PEI, indicating synergistic impacts between climate change and invasions. Analysis of a 24-year data set indicates a decline in the body size of all weevil species on PEI with increasing temperature. However, on MI, a negative relationship between mean annual temperature and body size is found only for Palirhoeus eatoni, a species not eaten by mice. A possible explanation for the positive relationships found for the other species could be due to higher metabolic demands imposed on mice in colder years than in warmer ones. Any increase in predation coupled with a preference for larger sizes, which the mice clearly show, would lead to a decline in the mean size of the weevil species. Due to the relationship between body size and metabolic rate and the importance of the weevils in the islands’ food webs, changes to the body size of these organisms could have significant consequences for the island ecosystems’ functioning. The thermal environment experienced by organisms also has a direct effect on survival, growth and reproduction. The physiological response of organisms to rapidly changing climates is therefore a primary concern. Organisms may respond to variable environmental conditions through phenotypic plasticity as well as behaviour. Chapter 5 of this thesis shows that of the weevil species and populations investigated on MI, most display phenotypic plasticity, the form of which is in keeping with the ‘Hotter is Better’ hypothesis. This could be due to rare extreme temperature events and the advantage for the performance curves to incorporate high temperatures experienced in the environment. Mismatches between thermal optima and preferred temperatures displayed by all species could mean that these weevils are well equipped to cope with warming conditions on MI unless the prediction of an increase of rare extreme events such as extreme temperatures is realised. Rapidly changing climates and an increase in the introduction of non-indigenous species are issues of major conservation concern. This has increased the significance of studies on the impacts of these threats. However, this thesis shows that to understand such processes, it is essential that an integration of disciplines be undertaken. This thesis thus adopts a multidisciplinary approach and highlights key issues associated with both climate change and biological invasions. The patterns and predictions of species and community responses to these environmental changes are complex. Moreover, predicting such responses is likely to be problematic, especially as multiple factors will change concurrently and how these factors might change is unclear. This highlights the importance of long-term records for understanding organism responses to such changes. Furthermore, impacts on indigenous species are likely to be exacerbated by the predicted increase in the rate of introductions with climate change. This makes the case for preventing the dispersal of invasive species to new areas all the more important. / AFRIKAANSE OPSOMMING: Klimaatsverandering en indringer spesies is belangrike bedreigings vir biodiversiteit. In besonder word voorspel dat hierdie bedreigings terrestriële sisteme in die sub-Antarktiese sal beïnvloed, waar beduidende ekosisteem reaksie aan beide reeds gesien is. In hierdie tesis word die sub-Antarktiese Prince Edward eiland groep as a model sisteem gebruik om belangrike vrae met betrekking tot klimaatsverandering en die impak van indringer spesies te ondersoek. Die eiland groep bestaan uit twee eilande, Marion (ME) en Prince Edward (PEE), wat beide versnellende verwarming ervaar, maar tog verskillende indringer samestellings het en vervolgens verskillende impakte ervaar. Variasie in die patrone van indringerspesierykheid en vollopheid en hulle onderliggende oorsake is van aansienlike omgewings en bewarings betekenis. Terwyl 'n toename in die beskikbaarheid van energie tipies lei tot 'n toename in spesierykheid, word die onderliggend meganismes van hierdie patrone swak verstaan. In Hoofstuk 2 van hierdie tesis, word hierdie verhoudings vir springsterte ondersoek, 'n belangrike komponent van die grond fauna op ME. Energie verduidelik 'n groot hoeveelheid van die ruimtelike variasie in inheemse en indringende springstert spesierykheid. Versteuringsdrempels en stressvolle temperature is meer belangrik as die toename in bevolking groottes in die bepaling van hierdie variasie in spesierykheid. Aangesien beide inheemse en indringende springstert spesierykheid en vollopheid sterk verwant is aan temperatuur, kan 'n verwarmende klimaat verreikende gevolge vir hierdie organismes hê. In die besonder word voorspel dat indringerspesies bevoordeeld sal wees relatief tot inheemse spesies onder verwarmende toestande. Een spesie waar dit veral blyk om geneig te wees, gegewe sy fisiologiese reaksie tot eksperimentele verhitting en uitdroging, is die groot indringer tomocerid, Pogonognathellus flavescens. Om te bepaal of dit die geval sal wees, hang af van die begrip van die onderliggende faktore van sy voorkomsgrense en vollopheidstruktuur. Daarbenewens is daar min studies wat gepoog het om te onderskei tussen die veroorsakende basis van vollopheidstruktuur en voorkomsgrense, veral vir indringerspesies. Dus, in Hoofstuk 3, word plaaslike mikroklimaat veranderlikes en fisiologiese toleransies van die indringer springstert, P. flavescens ('n habitat generalis), ondersoek. Die resultate stel voor dat die spesie wyd verspreid moet wees oor 'n verskeidenheid van habitatte op ME. Maar, die springstert is beperk tot inheemse Poa cookii polle grasveldhabitatte in die suidooste. Die huidige voorkomsgrense word daar gestel deur verspreidingsbeperking (dws voorwaardelike afwesighede), terwyl vollopheidstruktuur 'n funksie is van die variasie in die grond substraat kwaliteit. Maar, die uitbreidende verspreiding van P. cookii as gevolg van 'n groot bestuursingryping (die uitwissing van wilde huiskatte), kan P. flavescens in staat stel om alle geskikte gebiede te koloniseer met verloop van tyd. In Hoofstuk 4 verander die fokus na wat as die derde groot reaksie op klimaatsverandering beskou word, saam met voorkoms en fenologiese reaksies - veranderende diere liggaamsgroottes. Liggaamsgrootte is een van die beduidendste en mees voor die hand liggende eienskappe van diere en is van aansienlike ekologiese en fisiologiese belang. 'n Voorspelling van die temperatuur-grootte-reël (TGR) is dat met verwarming, liggaamsgrootte van die snuitkewerspesies op beide ME en PEE sal afneem. Hoe ookal, predasie deur muise van die snuitkewers op ME moet fundamenteel die patroon van sodanige verandering op PEE beïnvloed, wat sinergistiese impakte tussen klimaatsverandering en indringings aandui. Die ontleding van 'n 24-jarige datastel dui aan op 'n afname in die liggaamsgrootte van alle snuitkewer spesies op PEI met ‘n toename in temperatuur. Maar, op ME is 'n negatiewe verhouding tussen die gemiddelde jaarlikse temperatuur en liggaamsgrootte net gevind vir Palirhoeus eatoni, 'n spesie wat nie deur die muise geëet word nie. 'n Moontlike verduideliking vir hierdie positiewe verhoudings wat gevind is vir die ander spesies kan wees as gevolg van hoër metaboliese eise op die muise in kouer jare as in warmer jare. Enige toename in predasie, tesame met 'n voorkeur vir groter mates, wat die muise duidelik wys, sou lei tot 'n afname in die gemiddelde grootte van die snuitkewer spesies. As gevolg van die verhouding tussen liggaamsgrootte en metaboliese tempo, sowel as die belangrikheid van die snuitkewers in die eilande se voedselwebbe, kan veranderinge in die liggaamsgrootte van hierdie organismes beduidende gevolge op die eiland ekosisteme se funksionering hê. Die termiese omgewing wat deur organismes ervaar word het ook 'n direkte invloed op oorlewing, groei en voortplanting. Die fisiologiese reaksie van organismes op vinnig veranderende klimate is dus 'n primêre bron van kommer. Organismes kan reageer op veranderlike omgewingstoestande deur fenotipiese plastisiteit sowel as gedrag. Hoofstuk 5 van hierdie tesis toon dat van die snuitkewerspesies en bevolkings wat ondersoek is op ME, die meeste fenotipiese plastisiteit vertoon, die vorm wat in ooreenstemming is met die ‘Warmer is Beter’ hipotese. Dit kan wees as gevolg van seldsame uiterste temperatuur gebeure en die voordeel vir die prestasie kurwes om hoë temperature wat ervaar word in die omgewing in te sluit. Mismatches tussen termiese optima en voorkeur temperature vertoon deur alle spesies kan beteken dat hierdie snuitkewers goed toegerus is om die verhitting op ME te hanteer, tensy die voorspelling van 'n toename van seldsame uiterste gebeure soos uiterste temperature gerealiseer word. Vinnig veranderende klimate en 'n toename in die bekendstelling van nie-inheemse spesies is kwessies van groot bewarings kommer. Dit het die betekenis van studies oor die impak van hierdie bedreigings verhoog. Hierdie tesis toon egter dat om sulke prosesse te verstaan, dit noodsaaklik is dat 'n integrasie van die dissiplines onderneem word. Hierdie tesis aanvaar dus 'n multi-dissiplinêre benadering en beklemtoon die belangrike kwessies wat verband hou met beide klimaatverandering en biologiese indringing. Die patrone en voorspellings van spesies en die gemeenskapsreaksies op hierdie omgewingsveranderinge is kompleks. Verder, die voorspelling van sodanige reaksies sal waarskynlik problematies wees, veral omdat verskeie faktore gelyktydig sal verander en hoe hierdie faktore kan verander is onduidelik. Dit beklemtoon die belangrikheid van lang termyn rekords vir die begrip van organisme reaksies op sulke veranderinge. Verder, die impak van inheemse spesies is geneig om te vererger deur die voorspelde toename in die tempo van bekendstellings met klimaatsverandering. Dit maak die taak vir die bestuur van die voorkoming dat indringerspesies nuwe gebiede bereik al hoe meer belangrik.