RESOURCE-ALLOCATION TO YOUNG - SEASONAL PATTERNS WITHIN AND BETWEEN GAMMARUS-DUEBENI POPULATIONS

We examined patterns of resource allocation to young over the breeding season in a population of Gammarus duebeni from Totten Marsh in southern England and tested two hypotheses to explain seasonal changes in egg volume. Firstly, that egg volume changes in response to the effect of different environmental conditions on juvenile survival. Secondly, that females match their resource allocation pattern to the sex ratio of young produced under environmental sex determination. Our data supported the first hypothesis but lent no support to the second. We found that females vary their allocation of resources to young over the breeding season: larger eggs are produced in winter months and egg volume is significantly related to temperature. In addition, we looked at resource allocation in different populations and found a significant difference in the allocation patterns between this population and a more northern population from Budle Bay: females in the northern population do not vary egg volume over the season but produce larger eggs than females in the southern population. We propose that greater egg volume in the northern population is a constant response to a harsh environment; and that seasonal changes in egg volume in the southern population may be attributed to plasticity of resource allocation in response to environmental variability.