Sexually signalling animals must trade off the benefits of attracting mates with the consequences of attracting predators. For male guppies, predation risk depends on their behaviour, colouration, environmental conditions and changing intensity of predation throughout the day. Theoretically, this drives diel patterns of display behaviour in native Trinidadian populations, where males display more under low-light conditions when their most dangerous predator is less active. Here, we observed Australian guppies in a laboratory setting to investigate their diel display pattern, and if (...) this pattern is controlled by ambient light intensity. We also quantified individual variation in both the daily frequency and diel pattern of displays, and if such variation relates to body size, colouration and a non-sexual behaviour. Under a typical daily light regime, male guppies displayed mostly in the first hour of observation. Extending the duration of dawn-like lighting, however, resulted in an extended period of high display, demonstrating that light intensity per se is an important cue for this behaviour. These findings mirror those obtained for Trinidadian populations, suggesting that male courtship timing is likely shaped by broad, potentially generalizable features of guppy ecology. The effect of acclimation to captive conditions on male behaviour is also discussed. Whereas the temporal pattern of display appeared consistent, individuals varied in their daily display frequency, and this was correlated with variation in colour phenotype and a measure of non-sexual risk acceptance behaviour. Such relationships pose promising avenues for integrating behavioural and sensory ecology with contemporary work on behavioural syndromes and animal personality. (shrink)

The Queensland fruit fly (Bactrocera tryoni) is a generalist pest that poses a significant threat to the Australian horticultural industry. This species has become broadly established across latitudes that encompass tropical to temperate climates, and hence populations occupy diverse thermal niches. Successful expansion across this range may have been brokered by evolutionarily labile features of breeding phenology, physiology and/or behaviour. We explored the potential role of behavioural flexibility by characterizing variation in adult thermal preference using a novel gradient apparatus. Flies (...) oriented within this apparatus essentially at random in the absence of thermal variation, but sought and maintained precise positions when presented with an established gradient. Male and female flies from an ‘old’ colony (>300 generations) and a ‘young’ (F7) colony were compared. Whereas we found no difference between the sexes, flies from the young colony preferred higher temperatures (30.93 ± 7.30 °C) and had greater individual variation than their counterparts from the old colony (28.16 ± 5.63 °C). Given that B. tryoni are routinely maintained at 25 °C in the laboratory, a lower mean preference of the old colony is consistent with thermal adaptation. This is further supported by their reduced phenotypic variance, which follows as a logical consequence of stabilising selection given long-term environmental constancy. These results demonstrate that B. tryoni seek to thermoregulate via adult behaviour, and that individual temperature preference can be precisely measured using a gradient apparatus. The evidence for adaptive tuning of this behaviour has importance for both the design of captive rearing protocols as well as the prediction of invasive potential and species biogeography under future climatic variation. -/- . (shrink)

The concept of animal personality is based on consistent individual differences in behaviour, yet little is known about the factors responsible for such variation. Theory based on sex-specific selection predicts sexual dimorphism in personality-related traits and, in some cases, differences in trait variances between the sexes. In this study, we examined the sources of individual variation for boldness behaviour in guppies (Poecilia reticulata). We first demonstrated heightened boldness expression in males relative to females across feral wild types, artificially selected domestic (...) ‘designer’ guppies, and putative hybrids of the two. Boldness and body size covaried at the strain level but were not associated among individuals within strains. We also found high and repeatable behavioural differences among individuals (0.40 > intraclass r > 0.60) in all sex/strain groups except hybrid strain females. However, there was no evidence for the heightened inter-individual male variance anticipated for personality traits subject to certain forms of directional sex-specific selection. Domestic fish were boldest overall, and indicated the largest sex difference, which is consistent with genetic linkage between boldness and male ornamental colouration. Consistently high intrinsic variation in boldness behaviour, which extends to inbred domesticated fish, may in part underpin the invasive potential of this species. (shrink)