Environmental seasonality and latitude drive clutch size diversity in female lizards across populations

Global patterns in clutch size variations across species have been linked to resource availability and seasonal climate change. However, our understanding of the specific local-scale drivers of clutch size diversity has remained unclear, especially among populations of ectotherms with relatively homogeneous genetic structures experiencing varying local environmental conditions. And understanding the specific local-scale drivers of clutch size diversity within species can provide insight into the local adaptation of species or the evolution of key life history traits. Here, we collected clutch size data of a wide-ranging female lizard (Eremias argus) from field observation and literature across populations of varying elevations and latitudes in China. We then used mixed-effects models to test the relationship between clutch size, body size, habitat type, elevation, latitudes, and climate conditions. Unsurprisingly, body size was positively correlated with clutch size variations across all populations. When we accounted for body size, females from populations at higher latitudes had larger clutches, while females in less variable rainfall environments had smaller clutches. Interestingly, we found that females occupying higher geographic gradients (e.g., latitude and elevation) with certain habitats (e.g., grasslands and farmlands) were associated with larger clutch sizes. Thus, our study shows support for similar global macroecological drivers of clutch size diversity among lizard species, and also suggests that female ectotherms might have different reproductive decisions employed in response to local climates to maximise population replacement.