Altitudinal variation in reproductive investment among Gryllus campestris populations

Life history traits determine the organismal abundance within a population and are affected by the presence of trade-offs that modify relationships between traits. These relationships can vary across different environments either by local adaptation or phenotypic plasticity. Reproductive traits have direct fitness implications and therefore are suitable to study among population variation linked to environmental differences. Factors such as altitude are often related to differences in key physical factors like ambient temperature or the subsequent duration of the suitable period for annual activity. The aim of this work was to compare reproductive investment in females of the field cricket Gryllus campestris originated from different altitudes, but without identifying the components (genetic vs. phenotypic) of the analysed variables. This species has an annual cycle; after a winter diapause, adults emerge to breed by early mid spring to produce a new generation of nymphs. The study used females collected at the start of the 2021 breeding season, from 10 populations living in the Cantabrian region (Northern Spain). Five of them were located in areas under 170m a.s.l. and the other five above 1100m. Females were allowed to mate with a male from the same population and to lay eggs that we then collected to estimate egg mass and laying rate; both traits were analysed controlling for female size. We found no effect of altitude on any of the three measured traits, female size, egg mass, and laying rate, as well as on the relationships between each pair or traits. Our results suggest that this species is tolerant to environmental variation for the measured traits, showing that it has mechanisms to cope with a range of ambient temperatures.