Among-population differences in immunological traits allow to assess both evolutionary and plastic changes in organisms' resistance to pathogens. Such knowledge also provides information necessary to predict responses of such traits to environmental changes. Studies on latitudinal trends in insect immunity have so far yielded contradictory results, suggesting that multispecies approaches with highly standardised experimental conditions are needed. Here, we studied among-population differences of two parameters reflecting constitutive immunity – phenoloxidase (PO) and lytic activity – using common garden design on three distantly related moth species represented by populations ranging from northern Finland to Georgia (Caucasus). The larvae were reared at different temperatures and host plants under a crossed factors experimental design. Haemolymph samples to measure immune status were taken from the larvae strictly synchronously. Clear among-population differences could be shown only for PO activity in one species (elevated activity in the north). There was some indication that the cases of total absence of lytic activity are more common in southern populations. The effects of temperature, host and gender on the immunological traits studied remained highly species-specific. Some evidence was found that lytic activity may be involved in mediating trade-offs between immunity and larval growth performance. In contrast, PO did rarely covary with fitness-related traits, neither were the values of PO and lytic activity correlated with each other. The relatively inconsistent nature of the detected patterns suggests that studies on geographic differences in immunological traits should involve multiple species, and rely on several immunological indices if general trends are a point of interest.
- Received December 7, 2016.
- Accepted May 4, 2017.
- © 2017. Published by The Company of Biologists Ltd