Anne A. Besson

Thermal dependence of locomotor performance in two cool-temperate lizards

Temperate-zone ectotherms experience varying or very low ambient temperatures and may have difficulty in attaining preferred body temperatures. Thus, adaptations to reduce the thermal dependence of physiological processes may be present. We measured the optimal temperature range for sprint speed and compared it with the selected body temperatures (Tsel) of two sympatric, cool-temperate lizards: the diurnal skink Oligosoma maccanni and the primarily nocturnal gecko Woodworthia (previously Hoplodactylus) “Otago/Southland”. We also investigated whether time-of-day influenced sprint speed. Contrary to results for other reptiles, we found that time-of-day did not influence speed in either species. For each species, the optimal temperature range for sprinting and Tsel overlapped, supporting the ‘thermal coadaptation’ hypothesis. However, the optimal range of temperatures for speed is not always attainable during activity by either species, which have limited opportunities to attain Tsel in the field. The thermal sensitivity of sprint speed in these two species does not appear to have evolved to fully match their current thermal environment. More data on cold-adapted species are needed to fully understand physiological adaptation in ectotherms.

Thermal properties of artificial refuges and their implications for retreat-site selection in lizards

Artificial retreats or refuges (ARs) provide a useful method for sampling lizards and a possible means of restoring habitat to aid population persistence. Previous research suggests that preferences for ARs may vary among species and between different designs. To test these ideas further, we examined the influence of thermal and structural characteristics on use of three types of ARs by the nocturnal common gecko (Hoplodactylus maculatus) and diurnal McCanns skink (Oligosoma maccanni), two lizards endemic to New Zealand. The field study confirmed that the three ARs (triple-layered Onduline, triple-layered iron, solid concrete) differed in retreat-site temperatures provided during each of three seasons (winter, spring and summer). In their top spaces, Onduline ARs were the warmest by day, coolest by night, and thus displayed the largest diel variations in temperature. In the laboratory, common geckos showed a significant preference for Onduline whether ARs were exposed to a radiant overhead heat source or not, whereas skinks did not display any preference among the three types of ARs regardless of heating. The three types of ARs provided field temperatures within the thermal preference range of both species (data obtained from the literature) but only for the top spaces of the ARs and only during summer. Onduline was the only AR to consistently provide the temperatures preferred by pregnant females. Although this study suggests that structural properties alone may be sufficient to explain the preference of geckos for triple-layered Onduline stacks, it does not eliminate the possibility that attractive thermal properties also contribute. Long-term studies are needed to test the effects of artificial refuge supplementation on reptiles, and on their predators and competitors.

Missing links: testing the completeness of host-parasite checklists.

Host-parasite checklists are essential resources in ecological parasitology, and are regularly used as sources of data in comparative studies of parasite species richness across host species, or of host specificity among parasite species. However, checklists are only useful datasets if they are relatively complete, that is, close to capturing all host-parasite associations occurring in a particular region. Here, we use three approaches to assess the completeness of 25 checklists of metazoan parasites in vertebrate hosts from various geographic regions. First, treating checklists as interaction networks between a set of parasite species and a set of host species, we identify networks with a greater connectance (proportion of realized host-parasite associations) than expected for their size. Second, assuming that the cumulative rise over time in the number of known host-parasite associations in a region tends toward an asymptote as their discovery progresses, we attempt to extrapolate the estimated total number of existing associations. Third, we test for a positive correlation between the number of published reports mentioning an association and the time since its first record, which is expected because observing and reporting host-parasite associations are frequency-dependent processes. Overall, no checklist fared well in all three tests, and only three of 25 passed two of the tests. These results suggest that most checklists, despite being useful syntheses of regional host-parasite associations, cannot be used as reliable sources of data for comparative analyses.

Effect of maternal diet on offspring coping styles in rodents: a systematic review and meta‐analysis

Maternal nutrition can have long‐term effects on offspring morphology, physiology and behaviours. However, it is unclear whether mothers ‘program’ offspring behavioural coping strategy (proactive/reactive) according to the predicted nutritional quality of their future environment. We conducted a systematic review on this topic and meta‐analytically synthesized relevant experimental data on mice and rats (46 studies). We included data from experiments where dams were subjected to caloric restriction, protein restriction or overfeeding around gestation and subsequently measured offspring activity, exploration, or anxiety. Overall, little evidence existed for effects of maternal nutrition on the three investigated behavioural traits. The high heterogeneity observed in the data set suggests that maternal programming may sometimes occur. However, because offspring had access to a balanced diet before testing, behaviours may have been reprogrammed. Our results may indicate that reprogrammed behaviours could ameliorate negative effects associated with sub‐optimal nutrition in early life. Further, our systematic review revealed clear knowledge gaps and fruitful future research avenues.

Parental experience of a risky environment leads to improved offspring growth rate

Parasites (or diseases) are a major selective force for the evolution of life history traits and parasite–host evolution. Mothers can show a variety of responses to parasites during pregnancy, with different consequences for them or their offspring. However, whether information in the maternal environment before pregnancy can cause a change in the phenotype of the offspring is unknown. To avoid the confounding effect of pathogens and to reduce the risk of a direct effect of maternal immune system activation, we injected female laboratory mice with lipopolysaccharides (LPS) before they mated. In order to provide constant information on the potential infectious risk of the environment, females were mated with males that were also exposed to LPS before mating. Offspring from immune-challenged parents were larger and grew at a faster rate than offspring from control parents (injected with PBS). Additionally, offspring from immune-challenged parents that suffered the most from inflammation grew at a faster rate than offspring from low suffering parents. Producing heavier offspring that will reach sexual maturity earlier is likely to have fitness benefits for parents and offspring through improved reproductive success.