Offspring size and maternal environments mediate the early juvenile performance of two congeneric whelks
Offspring size variation can have pervasive ecological and evolutionary implications for both offspring and mother, affecting an organism’s performance throughout its life. Using 2 marine intertidal whelk species Cominella virgata and C. maculosa as model organisms, we examined how different maternal environments and contrasting hatchling size influence juvenile performance. The average size of field-collected hatchlings greatly differed between the species and at different scales of variation (i.e. among sites). Species-specific differences in hatching size were reflected in juvenile performance. Overall, C. virgata with larger hatchlings (~3 mm), exhibited faster growth rates and higher survival than the smaller C. maculosa (~1.5 mm). Desiccation treatment did not affect the performance of fed juveniles; however, large hatchlings had higher growth rates than small conspecifics for both species. Starved hatchlings of both species performed more poorly than fed ones; however, species- specific and size differences were less significant for the evaluated traits, suggesting a non- size-related allocation of resources and similar resource utilization during starvation conditions (i.e. within species). As has been described for many taxa, large offspring often perform better than small conspecifics; however, because this performance is likely context-dependent, understanding the importance of different scales of variation is crucial for determining when variation in size is an advantage or a disadvantage in terms of an organism’s performance.