Scale-dependent size variability of Cyprideis torosa (Ostracoda)

Organism size is considered a master trait influencing virtually every aspect of life, but the underlying mechanisms of phenotypic variation are still poorly understood. This study examined the valve size (length, height, width) of an ostracod species (Cyprideis torosa) collected from different lakes of the Mansfeld Lakes (ML), Central Germany. Size variability were investigated on different temporal (ecological and geological) scales and compared on different spatial (regional and local) scales. Statistical methods were applied to explore size variation between and within sample locations and the relationship between size traits and physical and chemical parameters (salinity, oxygen, temperature, pH). In ML no significant differences in size between contiguous lakes were detected but two morphotypes in males were identified in stratigraphically separated Holocene samples and co-occurring within Recent samples. Seasonal effects were detected for females (smaller size in spring than in autumn) and males (smaller size range in spring, higher variability in autumn). The correlation of size traits with environmental parameters revealed no general patterns, but a locally limited correlation between size and salinity in ML exists. On spatial and temporal scales, males and females show sex-specific size patterns, possibly due to differences in life history traits or selection pressure.