How Patch Selection Shapes Life History Traits: Insights from a Damselfly Emergence

Environmental heterogeneity can drive intraspecific variation in life history traits. Sampling across multiple habitat patches enables the detection of such spatial variation, offering a more comprehensive understanding of species-level variation in traits resulting from responses to fine-scale environmental conditions. This study investigates how life history traits in the damselfly Calopteryx haemorrhoidalis differ among habitat patches in a lotic freshwater system. We tested the hypothesis that individuals emerging from different patches potentially exhibit distinct traits (phenology, body size, and seasonal patterns). We sampled exuviae from seven patches along a stream in northeastern Algeria during spring and summer 2012. We recorded exuvia abundance, emergence timing, body size at emergence, and sex ratio. We found significant variation among patches in exuviae abundance, emergence phenology, and seasonal trends in body size. While body size at emergence remained largely consistent across patches, the seasonal pattern in size differed, with some patches showing strong temporal patterns (declines) and others showing none. Sex ratio was female-biased overall but did not differ significantly between patches. Our findings highlight the ecological relevance of spatial heterogeneity at small scales. Sampling a single patch may yield biased estimates of key life history traits, thus incorporating spatial replicates is essential for accurately characterizing population-level patterns and informing effective conservation strategies in freshwater ecosystems.