Personality and pace-of-life behavioral syndromes in a model species, the House Sparrow (Passer domesticus)

Consistent individual differences in behaviour ( animal personality ) may be favoured by natural selection because they are driven by adaptive differences in life-history and physiology traits, constituting a pace-of-life syndrome (PoLS). Here we test this hypothesis as well as other behavioural syndrome structures using individual behavioural assays of 198 house sparrows (Passer domesticus) in captivity, and connecting individual levels of behaviour (activity in a novel environment and with a novel object and novel food) with morphological and basal metabolic rate (BMR) data. Variation between individuals in the measured behaviours and BMR, and the covariance pattern of behaviours, BMR and morphological measures were quantified using univariate tests and structural equation modelling, respectively. Activity level was the only consistent behaviour across time and contexts, and all behavioural variation was driven by an 'activity' syndrome, suggesting that our assays failed to capture any meaningful variation in neophilia or foraging innovation. There was no individual consistency in distance to the novel object or food, or in BMR. There were no sex differences in behaviour, and there was no obvious link between metabolism and personality in 'activity'. We cannot necessarily conclude from this that there is no PoLS in house sparrows, because these populations were studied only in the winter and due to BMR-based experiments there is limited reliable information on the details of their life-history traits (i.e., rates of reproduction). However, many of the most obvious phenotypic covariances hypothesised by the PoLS do not seem to be present here. There was a male-specific 'status' syndrome involving positive covariation of plumage traits and age that were related to individual quality. Again, there were surprisingly few links between 'status', individual male 'activity' behaviour and/or BMR. This suggests that the individual variation in behaviour (and BMR) measured in our sparrows is largely explained by within-individual plasticity, rather than personality or a wider pace-of-life syndrome structure

CTmax is repeatable and doesn't reduce growth in zebrafish

Critical thermal maximum (CTmax) is a commonly and increasingly used measure of an animal’s upper thermal tolerance limit. However, it is unknown how consistent CTmax is within an individual, and how physiologically taxing such experiments are. We addressed this by estimating the repeatability of CTmax in zebrafish, and measured how growth and survival were affected by multiple trials. The repeatability of CTmax over four trials was 0.22 (0.07–0.43). However, CTmax increased from the first to the second trial, likely because of thermal acclimation triggered by the heat shock. After this initial acclimation response individuals became more consistent in their CTmax, reflected in a higher repeatability measure of 0.45 (0.28–0.65) for trials 2–4. We found a high innate thermal tolerance led to a lower acclimation response, whereas a high acclimation response was present in individuals that displayed a low initial CTmax. This could indicate that different strategies for thermal tolerance (i.e. plasticity vs. high innate tolerance) can co-exist in a population. Additionally, repeated CTmax trials had no effect on growth, and survival was high (99%). This validates the method and, combined with the relatively high repeatability, highlights the relevance of CTmax for continued use as a metric for acute thermal tolerance

Dataset for repeatability of CTmax manuscript.txt

Dataset to accompany manuscript entitled "CTmax is repeatable and doesn't reduce growth in zebrafish

Are model organisms representative for climate change research? Testing thermal tolerance in wild and laboratory zebrafish populations

Model organisms can be useful for studying climate change impacts, but it is unclear whether domestication to laboratory conditions has altered their thermal tolerance and therefore how representative of wild populations they are. Zebrafish in the wild live in fluctuating thermal environments that potentially reach harmful temperatures. In the laboratory, zebrafish have gone through four decades of domestication and adaptation to stable optimal temperatures with few thermal extremes. If maintaining thermal tolerance is costly or if genetic traits promoting laboratory fitness at optimal temperature differ from genetic traits for high thermal tolerance, the thermal tolerance of laboratory zebrafish could be hypothesized to be lower than that of wild zebrafish. Furthermore, very little is known about the thermal environment of wild zebrafish and how close to their thermal limits they live. Here, we compared the acute upper thermal tolerance (critical thermal maxima; CTmax) of wild zebrafish measured on-site in West Bengal, India, to zebrafish at three laboratory acclimation/domestication levels: wild-caught, F1 generation wild-caught and domesticated laboratory AB-WT line. We found that in the wild, CTmax increased with increasing site temperature. Yet at the warmest site, zebrafish lived very close to their thermal limit, suggesting that they may currently encounter lethal temperatures. In the laboratory, acclimation temperature appeared to have a stronger effect on CTmax than it did in the wild. The fish in the wild also had a 0.85–1.01°C lower CTmax compared to all laboratory populations. This difference between laboratory-held and wild populations shows that environmental conditions can affect zebrafish’s thermal tolerance. However, there was no difference in CTmax between the laboratory-held populations regardless of the domestication duration. This suggests that thermal tolerance is maintained during domestication and highlights that experiments using domesticated laboratory-reared model species can be appropriate for addressing certain questions on thermal tolerance and global warming impacts