My dissertation research investigates the genetic architecture and evolutionary significance of physiological variation in two wildflower species, Ipomopsis aggregata and Arabidopsis thaliana. In particular, my work focuses on water use efficiency (WUE), a critical physiological trait that dictates plant growth and performance in resource-limited environments. I used a combination of quantitative trait loci (QTL) mapping, field selection experiments, and classic quantitative genetics to investigate 1) the genetic architecture of water use efficiency and flowering time, 2) patterns of natural selection on water use efficiency, flowering time, and other ecological traits in I. aggregata, and 3) additive genetic variation, genetic correlations, and selection on water use efficiency, flowering time, and plasticity to drought in Arabidopsis thaliana. Using an Ipomopsis aggregata genetic mapping population, I identified four QTL underlying WUE, three QTL-QTL epistatic interactions, and evidence for a possible QTL x cytoplasmic interaction affecting WUE. I found a similar genetic architecture underlying flowering time, with four main effect QTLs that all adjacently localized to the same linkage groups as WUE, and three QTL-QTL epistatic interactions, which occur between the same chromosome pairs as the WUE interactions. The combined main and interactive effects explain 35% and 40% of the phenotypic variation in WUE and flowering time, respectively. The adjacent localization suggests a possible role for the evolution of co-inheritance or, if the true QTL positions actually overlap, a possible role for pleiotropy underlying the phenotypic correlation between WUE and flowering time. Additionally, these results suggest epistasis is a significant factor affecting phenotypic variation in nature. In a reciprocal transplant and water addition experiment, I demonstrated variable natural selection on WUE, flowering time, and nectar production in I. aggregata across elevation/habitat and differential water availability. At low elevation in the water addition treatment, natural selection favors early flowering and greater nectar sugar concentration, while dry conditions favor high WUE and early flowering time. At high elevation, where the growing season is shorter and drier, selection favors early flowering regardless of water addition. These results suggest natural selection on ecophysiological and floral traits varies with resource availability (e.g. water availability and pollinator visitation). Using data from a glasshouse experiment involving a global panel of accessions of Arabidopsis thaliana, I demonstrated strong positive genetic correlation between WUE and flowering time, as well as selection for low WUE and early flowering under experimental season-ending drought. Finally, I found significant genetic variation in plasticity as well as selection favoring greater WUE plasticity under drought, indicating plasticity to drought is adaptive in A. thaliana. / text

Behaviors can exhibit a wide degree of plasticity depending on the environmental context in which they are expressed. Despite this, repeatable differences have been found among and within individuals across a wide range of taxa. For my thesis, I investigated individual differences in foraging and parental care. In the first experiment, I assessed house sparrows (Passer domesticus) for domain-generality among neophobia, habituation and associative learning as they are all responses to novelty. While the results of the study find individual differences in each of these contexts the conclusion supported separate mechanisms for each response (domain-specificity). In the second experiment, I examined how the loudness of brood begging vocalizations influenced parent trip time, food load size brought to the nest and the amount of time spent in the box. The results of this study found individual differences in trip time and the time spent in the box with regard to the initial five seconds of begging loudness during a parent’s visit. Additionally, trip time was also influenced by the change in loudness within a visit. My findings reveal that individual variation may depend on the context in which individuals are measured.

No description available.

L’étude qualitative et quantitative du mode de développement des plantes envahissantes est actuellement considérée comme une étape clef dans la compréhension des phénomènes d’invasion. L’objectif de ce travail est de préciser les relations qui existent entre la structure architecturale des buissons et leur caractère proliférant. Nous avons sélectionné cinq espèces buissonnantes (Cornus sericea L., Cornaceae ; Prunus virginiana L., Rosaceae ; Rhamnus cathartica L., Rhamnaceae ; Rhus typhina L., Anacardiaceae ; Zanthoxylum americanum Mill., Rutaceae) qui sont connues pour leur aptitude à bloquer la succession végétale sous certaines conditions au Sud du Québec (Canada). L’analyse architecturale a permis chez ces espèces de caractériser les unités structurelles et leurs modifications ontogéniques. Ces modifications ontogéniques doivent être prise en compte afin d’obtenir une description complète de la plasticité phénotypique chez ces espèces. L’analyse des différentes unités structurelles révèle qu’elles ne possèdent pas la même signification fonctionnelle : les niveaux d’organisation les plus grands sont responsables majoritairement des capacités de plasticité phénotypique de la plante et de sa compétition. Ces analyses ont abouti à la définition de trois stratégies architecturales correspondant à des comportements individuels et qui sont également pertinentes pour expliquer la prolifération des populations. / Qualitative and quantitative studies of the pattern of invasive plant development is now considered a key aspect in understanding invasiveness. This work was performed to determine relationships between shrub architectural plasticity and proliferating behaviour. We selected five shrub species (Cornus sericea L., Cornaceae ; Prunus virginiana L., Rosaceae ; Rhamnus cathartica L., Rhamnaceae ; Rhus typhina L., Anacardiaceae ; Zanthoxylum americanum Mill., Rutaceae) known to arrest plant succession under certain conditions in Southern Québec, Canada. Architectural analysis revealed species’ structural units and their ontogenic changes. These ontogenic changes need to be calibrated if a full description of phenotypic plasticity is to be obtained. Analysis of the plant structural units reveals that they are of different functional significance: the higher the level of organization, the greater the capacity for phenotypic plasticity and competition. We defined three architectural strategies related to individual behaviours and which can relevantly explain the population proliferation of shrubs. / Réalisé en cotutelle avec l'Université Montpellier II

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

Climate change predictions suggest that the continent most vulnerable to climate change is Africa. The impacts of potential changes which include increases in air temperatures and rainfall variability are negative with potential species extinctions projected throughout southern Africa. A number of climate models have been applied to examine the consequences of climate change for ranges of South African animal species. One such model frequently predicted range shifts from west to east, which is realistic considering the marked aridity gradient in an east-west direction across the country, but the authors suggested that these shifts may not be as marked if species are able to use physiological and behavioural methods to adapt to an increase in aridity. Information on the degree to which behavioural and physiological flexibility affect species range in southern Africa is scant which is surprising given its importance with regard to climate change. Thallomys nigricauda occurs along an east-west aridity gradient in southern Africa, inhabiting mesic, semi-xeric and xeric regions. One would expect phenotypic flexibility in physiological and behavioural traits in response to the diverse environmental conditions to be related to the success and range of the species. The wide distribution and arboreal habits, suggesting that T. nigricauda is exposed to greater extremes of temperature than fossorial rodents, makes T. nigricauda an ideal species to test this assumption. Hence I expected that T. nigricauda would exhibit variation in physiological and behavioural traits measured along an aridity gradient. This has important implications in predicting the survival of small mammal species in the light of climate change in southern Africa. Thallomys nigricauda were live-trapped in winter 2006 and 2007 and summer 2007 using Elliot traps in three sites: mesic site Weenen Game Reserve (KwaZuluiv Natal Province, South Africa); semi-xeric site Haina Game Farm (Botswana) on the northern boundary of the Central Kalahari Desert and xeric site Molopo Nature Reserve (southern Kalahari savannah, North-West Province, South Africa). I studied the home-range size of T. nigricauda by radiotracking 12 males and 16 females in winter 2006, 2007 and summer 2007. Home ranges were estimated using 100% and 95% minimum convex polygons and 95% and 50% fixed kernels. Home ranges varied widely, from 166 to 80199m2 for males and from 46 to 8810m2 for females. Males had larger home ranges than females, which supports a promiscuous mating system reported for the species. Although range size was reduced in both sexes in winter, this was not significant. I found no significant difference in home range size along the aridity gradient. It is suggested that a combination of precipitation, habitat productivity and breeding system influences the size of home range of the species, and that this species displays phenotypic flexibility in terms of its behavioural responses to these factors. I measured the urine concentrating ability (UCA), as indicated by urine osmolality and relative medullary thickness (RMT), and water turnover rate (WTR) of T. nigricauda. There was no significant difference in RMT between sites or sex and no difference in osmolalities when site, season and sex were taken into account. In addition, specific WTR was not significantly influenced by season. Lack of significant differences could be the result of the high degree of individual variation in the traits measured, an indication of the flexibility in UCA and WTR. However, higher urine osmolality and lower WTR’s were recorded in the dry winter months. I quantified the thermal environment perceived by a small, arboreal, mammalian endotherm using a number of methods at three study sites in winter and summer. Our area of interest was how well these methods accurately portrayed the actual temperatures that small mammals are exposed to. Temperature differences between the methods were largest during the midday, when temperatures were highest. All methods recorded a greater range of temperatures during photophase than during scotophase. Black-bulb and model temperatures produced more accurate, rapid measurements when compared to measurements produced by direct temperature recording devices, particularly during photophase, when solar radiation is the major influence of heating. Other methods lagged behind black-bulb measurements. Although the mean temperatures of some of the methods were significantly different, there was a high degree of correlation between all methods, even after randomization and generation of 25% and 10% subsamples. Computed thermal indices and blackbulb temperatures produced similar thermal profiles. In studies requiring accurate time series measurements, it is suggested that black-bulb or copper models be employed rather than direct temperature recording devices. Simpler measurement devices would suffice for studies requiring an estimate of the temperature variation and trends in the microclimate of small mammalian endotherms, particularly arboreal or cavity dwelling species. In the wild, across an aridity gradient, I measured abdominal body temperarture (Tb) of T. nigricauda using implanted iButtons®. All but three T. nigricauda displayed significant 24 h Tb rhythmicity. The Tb range for free-living T. nigricauda was 32.33-40.63 oC (n = 13) and 32.69-40.15 oC (n = 17) in winter and summer respectively. Although there was variation in Tb profiles, T. nigricauda generally displayed a bimodal distribution of Tb, with high and low Tb values during scotophase and photopase respectively. Body temperature range was significantly greater in winter, when T. nigricauda reduced its minimum Tb. It was shown that the maximum amplitude of circadian rhythms of body temperature was on average 259.6% of expected values. To determine the extent to which the microclimate of T. nigricauda cavities assists in the maintenance of Tb, I measured the temperatures of cavities across the gradient, providing an indication of the degree of buffering provided by refugia. I measured the temperatures of shallow and deep regions of cavities using iButtons® in summer and winter and recorded operative and shade temperatures for comparison. Compared with operative temperature, cavities had stable microclimates, displaying smaller ranges in temperature. Mean minimum and maximum cavity temperatures differed significantly to operative temperature and between seasons, whereas there was no significant difference between shallow and deep measurements in cavities. Differences in the buffering capacities of the cavities between seasons were not significant. To determine whether T. nigricauda alter its length of exposure in response to lower ambient temperatures in winter as a means of maintaining Tb, I measured the activity of T. nigricauda, defined as the proportion of fixes outside the home cavity of the individual. Males spent a greater proportion of the active phase away from their home cavity in summer, and significantly in winter when compared with females, but there were no differences between seasons. It is suggested that T. nigricauda realize energy savings by lowering its Tb during their rest phase during the day, allowing them to maintain nocturnal activity and overall energy balance. Thus, besides the larger male home range, a result of the reproductive pattern, the physiological and behavioural traits of T. nigricauda measured in this study did not differ between aridity sites or seasons. The results of this study, in highlighting the variation in physiological and behavioural responses of subpopulations of T. nigricauda to diverse conditions, suggest that this variation is due to phenotypic flexibility. Understanding the extent and nature of this flexibility is critical to our comprehension of the consequences climate change. By defining the presence and extent of intraspecific variation in physiology and behaviour, this study resolved the necessary first step towards this understanding for the widely distributed T. nigricauda in southern Africa. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.

Graduate

Paropsis atomaria (Coleoptera; Chrysomelidae) is a eucalypt feeding leaf beetle endemic to southern and east coast Australia, and it is an emergent pest of the eucalypt hardwood industry. Paropsis atomaria was suspected to be a cryptic species complex based on apparent differences in life history characteristics between populations, its wide geographical distribution, and extensive host range within Eucalyptus. In this study genetic and ecological characters of P. atomaria were examined to determine the likelihood of a cryptic complex, and to identify the nature and causes of ecological variation within the taxon. Mitochondrial sequence variation of the gene COI was compared between populations from the east coast of Australia (South Australia to central Queensland) to assess genetic divergence between individuals from different localities and host plant of origin. Individuals from four collection localities used for the molecular analysis were then compared in a morphometric study to determine if observed genetic divergence was reflected by morphology, and common-garden trials using individuals from Lowmead (central Qld) and Canberra (ACT) were conducted to determine if morphological (body size) variation had a genetic component. Host plant utilisation (larval survival, development time, and pupal weight) by individuals from Lowmead and Canberra were then compared to determine whether differential host plant use had occurred between populations of P. atomaria; individuals from each population were reared on an allopatric and sympatric host eucalypt species (E. cloeziana and E. pilularis). Finally, developmental data from each population was compared and incorporated into a phenology modelling program (Dymex(tm)) using temperature as the principle factor explaining and predicting population phenology under field conditions. Molecular results demonstrated relatively low genetic divergence between populations of P. atomaria which is concomitant with the single species hypothesis, however, there is reduced gene flow between northern and southern populations, but no host plant related genetic structuring. Morphometric data revealed insufficient evidence to separate populations into different taxa; however a correlation between latitude and size of adults was discovered, with larger beetles found at lower latitudes (i.e., adhering to a converse Bergmann cline). Common garden experiments revealed body size to be driven by both genetic and environmental components. Host plant utilisation trials showed one host plant, E. cloeziana, to be superior for both northern and southern P. atomaria populations (increased larval survival and reduced larval development time). Eucalyptus pilularis had a negative effect on pupal weight for Lowmead (northern) individuals (to which it is allopatric), but not so for Canberra (southern) individuals. DYMEX(tm) modelling showed voltinism to be a highly plastic trait driven largely by temperature. Results from across all trials suggest that P. atomaria represents a single species with populations locally adapted to season length, with no evidence of differential host plant utilisation between populations. Further, voltinism is a seasonally plastic trait driven by temperature, but with secondary influential factors such as host plant quality. These data, taken combined, reveal phenotypic variability within P. atomaria as the product of multiple abiotic and biotic factors and representing a complex interplay between local adaptation, phenotypic plasticity, and seasonal plasticity. Implications for pest management include an understanding of population structure, nature of local adaptation and host use characteristics, and predictive models for development of seasonal control regimens.

Η θερμοκρασία ανάπτυξης αποτελεί παράγοντα μεγάλης σημασίας στην οντογένεση των ιχθύων, αφού ως ποικιλόθερμοι οργανισμοί είναι συνεχώς εκτεθειμένοι στις μεταβολές του περιβάλλοντός τους. Έχει παρατηρηθεί πως η θερμοκρασία ανάπτυξης δύναται να προκαλέσει μετατόπιση του χρονοδιαγράμματος των οντογενετικών γεγονότων και πλαστικότητα σε μορφολογικούς και φυσιολογικούς χαρακτήρες (πχ στο μυοσκελετικό και το καρδιαγγειακό σύστημα). Ωστόσο, μέχρι σήμερα δεν έχει μελετηθεί η επίδραση της θερμοκρασίας ανάπτυξης στο πρότυπο της γονιδιακής έκφρασης του zebrafish και σκοπός της παρούσας εργασίας είναι η μελέτη του ολικού μεταγραφικού προτύπου νυμφών zebrafish. Για το λόγο αυτό σχεδιάστηκαν δύο πειράματα, όπου τρεις θερμοκρασιακές συνθήκες ανάπτυξης (22, 28 και 32oC) εφαρμόστηκαν στην πρώιμη οντογενετική περίοδο: για το διάστημα 0-20 dpf* (1ο πείραμα) και 10-20 dpf (2ο πείραμα). Πραγματοποιήθηκε απομόνωση ολικού RNA από τα άτομα ηλικίας 20 dpf όλων των πληθυσμών και από τα άτομα ηλικίας 10 dpf του πληθυσμού των 28oC του 2ου πειράματος και ακολούθησε υβριδοποίηση σε ολιγονουκλεοτιδικές μικροσυστοιχίες Affymetrix, με 15.509 αντιπροσωπευτικές αλληλουχίες γονιδίων (probe sets). Τα 21 μεταγραφικά προφίλ επεξεργάσθηκαν με τα εξειδικευμένα προγράμματα ανάλυσης μικροσυστοιχιών, dChip και MeV (v.4.5.1). Η κανονικοποίηση και το φιλτράρισμα των δεδομένων των μικροσυστοιχιών απέδωσε μεταγραφικά πρότυπα με 9.488 probe sets. Με τεχνικές πολυπαραμετρικής στατιστικής ανάλυσης (HCL και PCA) πραγματοποιήθηκαν οι συγκρίσεις των μεταγραφικών προτύπων μεταξύ των πειραματικών πληθυσμών για κάθε θερμοκρασία ανάπτυξης και οντογενετικό στάδιο. Οι HCL και PCA αναλύσεις έδειξαν i) σαφή διαχωρισμό των μεταγραφικών προτύπων μεταξύ των δύο πειραμάτων, ii) σαφή διαχωρισμό των προτύπων των 28oC και 32oC ως προς αυτά των 22oC και στα δύο πειράματα, και iii) σαφή διαχωρισμό των προτύπων των 28oC διαφορετικού οντογενετικού σταδίου (ηλικίας 10 dpf vs 20 dpf). Θα αναμέναμε τα πρότυπα έκφρασης των 28oC να παρουσιάζουν παρόμοιο πρότυπο, κάτι που δεν παρατηρείται. Αυτό οφείλεται στο πειραματικό σφάλμα που υπεισέρχεται από το διαφορετικό χρόνο πραγματοποίησης των δύο πειραμάτων και τις ρυθμίσεις κατά την υβριδοποίηση. Έτσι πραγματοποιήθηκε η κανονικοποίηση των “28”, που απαλείφει το πειραματικό σφάλμα. Οι HCL και PCA αναλύσεις έδειξαν i) σαφή διαχωρισμό των μεταγραφικών προτύπων των 28oC και 32oC ως προς αυτά των 22oC ως αποτέλεσμα της επίδρασης της θερμοκρασίας ανάπτυξης, ii) σαφή διαχωρισμό των προτύπων των 22oC των δύο πειραμάτων ως αποτέλεσμα της επίδρασης της περιόδου εφαρμογής και διάρκειας της θερμοκρασιακής αγωγής και iii) σαφή διαχωρισμό των πρότυπων των 28oC (ηλικίας 10 dpf vs 20 dpf) ως αποτέλεσμα της επίδρασης του οντογενετικού σταδίου. Ακολούθως, πραγματοποιήθηκε ανάλυση σημαντικότητας (SAM) και λειτουργική γονιδιωματική ανάλυση (λογισμικό DAVID) των στατιστικώς σημαντικών γονιδίων που διαφοροποιούν τα πρότυπα. Η ανάλυση των γονιδίων, ως προς την ιστοειδική έκφραση ανέδειξε γονίδια που σχετίζονται με την ανάπτυξη του ματιού, των θωρακικών πτερυγίων και του εγκεφάλου στους πληθυσμούς των 22oC έναντι των 28oC και 32oC. Η παρούσα εργασία αποδεικνύει την επίδραση της θερμοκρασίας ανάπτυξης και της διάρκειας της θερμοκρασιακής αγωγής, καθώς επάγει μηχανισμούς πλαστικότητας στο επίπεδο της γονιδιακής έκφρασης. Τέλος, υποδεικνύεται πως η πρώιμη οντογενετική περίοδος τείνει να είναι περισσότερο θερμοευαίσθητη, καθώς παρατηρείται εντονότερη επίδραση της θερμοκρασίας (στην περίπτωση των 22οC)στην ανάπτυξη του ατόμου. *dpf: days post fertilization / Developmental temperature plays a principal role in the ontogeny of fish. It is known that developmental temperature may shift the initiation time of the ontogenetic stages and induce plasticity in morphological and physiological characters e.g. the musculoskeletal and the cardiovascular system. However, its effect on the gene expression pattern has not previously been attempted for zebrafish. In the present study, zebrafish Affymetrix microarrays of 15,509 probe sets were used to map the transcriptome profile of: a) 20 dpf* old zebrafish larvae at three developmental temperatures, i.e. 22oC, 28oC and 32oC (1st experiment) and b) 20 dpf old zebrafish larvae, which were all grown at 28oC for the first 10 days and subsequently divided into three groups, which were grown at 22oC, 28oC and 32oC, respectively; the profile of 10 dpf old larvae was also measured (2nd experiment). We have isolated total RNA from the above populations and then, hybridization of RNA samples has been done on oligonucleotide Affymetrix microarrays of 15,509 probe sets. All 21 profiles were normalized and filtered (dChip software), and multivariate statistical analysis techniques were used on the normalized 9,488 probe set expression profiles (TM4 MeV software). Hierarchical Clustering (HCL) and Principal Component Analysis (PCA) on expression profiles indicated: a) clear separation of the two experiments based on their transcriptomic patterns, b) clustering of the 28oC and 32oC profiles of the 20 dpf old larvae separately from those at 22oC in both experiments and c) clear separation of the 28oC profiles based on the developmental stage. We would expect expression profiles of 28oC to be clustered together, though this was not observed because of experimental parameters during the hybridization, as the two experiments were carried out independently on different dates. So the normalization of “28” profiles took place, in order to eliminate the experimental noise. HCL and PCA, then, indicated: a) clustering of the 28oC and 32oC profiles of the 20 dpf old larvae separately from those at 22oC, as the effect of developmental temperature, b) clear separation of 22oC profiles of the two experiments, based on the effect of the period and duration of thermal conditions and c) clear separation of the 28oC profiles based on the developmental stage. Then, Significant Analysis of Microarrays (SAM) and Functional Genomic Classification Analysis (DAVID software) of statistically significant genes was carried out. Analysis of genes based on tissue-specific expression indicated characteristic genes for the development of the eye, pectoral fins and brain in 22oC profiles versus 28oC and 32oC profiles. The present study has proved that thermal effect is determinative among the early ontogenetic stage, especially in the case of longer cold thermal period, and developmental temperature may induce plastic response of gene expression, that could affect the fate of fish. *dpf: days post fertilization

Climatic envelope models focus on the climatic variables affecting species or species assemblages, and are important tools to investigate the effect of climate change on their geographical ranges. These models have largely been proposed in order to make successful predictions on species‘ persistence, determining which variables are likely to induce range expansion, contraction, or shifting. More recent models, including the ability and the cost for individuals to respond promptly to an environmental stimulus, have revealed that species may express phenotypic plasticity able to induce adaptation to the new environment. Consequently, understanding how species evolve to a changing climate is fundamental. From this perspective, investigating intraspecific responses to an environmental variable may contribute to better understanding and prediction of the effect of climate change on the geographical range and evolution of species, particularly in the case of widespread species. In this context, the present study aimed at establishing how environmental variables (focussing mainly on temperature) may have contributed to shape the spatial distribution, physiology, reproductive biology and connectivity of two species of Southern African sandhoppers (Talorchestia capensis and Africorchestia quadrispinosa, Amphipoda, Talitridae). Most of the work was carried out on T. capensis, due to its widespread spatial distribution. A first investigation of the biogeography of T. capensis and A. quadrispinosa, revealed that, for both species, spatial patterns of abundance, size and sex ratio were not explained by the Abundant Centre Hypothesis (greater abundance at the core of a spatial range), but rather guided by bio-physical forces. Precisely, the abundance of sandhoppers was driven by the morphodynamic state of the beach, salinity and temperatures, with strong differentiation among sites that reflected local environmental conditions. In support of these findings, strong population structure in the genetics of T. capensis was found (three main groups) when investigating its phylogeography and genetic connectivity. Although such defined structure may suggests cryptic speciation, the concomitant within-population variation in the COX1 region of mtDNA, also highlighted the importance of individual genetic variability. High individual variability was also found in the response of T. capensis to temperature, both in its physiology (thermal plasticity) and its reproductive biology (maternal effects). Since temperature is one of the main variables affecting the coastal marine systems of southern Africa and the metabolism of animals in general, its effect on the physiology and reproduction of T. capensis was therefore investigated. Thermal responses to increasing/decreasing temperatures were assessed for separated populations of T. capensis. Individual variability was reported in the oxygen consumption of T. capensis in response to temperature (high variation around the means, especially for increasing temperatures). Among population differences in thermal sensitivity were significantly correlated with air temperature variability experienced over the past 23 years, highlighting the importance of historical temperature fluctuations to the current thermal physiology of these sandhoppers. Temperature also had an important effect on the reproductive plasticity of T. capensis. Different temperatures induced mothers to adjust the size of their offspring (i.e. egg size), with larger eggs produced at lower temperatures. Interestingly, females showed strongly significant among individual variation in the size of the eggs. Given the importance of understanding rapid responses of organisms to climate change and considering the fundamental role played by phenotypic plasticity in evolution, the overall study revealed the significance of individual plasticity and variability in response to the environment and highlighted its importance. Particularly, studying the thermal physiology of separated populations and understanding within population reproductive plasticity in response to temperature, helped to clarify how differences among individual responses have important consequences at the population level, possibly explaining the widespread distribution of T. capensis.