Leaf abscission phenology of a scrub oak: consequences for growth and survivorship of a leaf mining beetle

Brachys tessellatus is a leaf-mining beetle that attacks Quercus laevis (tu rkey oak), a deciduous scrub oak in the fall line Sandhills of the southeas tern United States. This oak species varies substantially in leaf abscissio n phenology. In the fall of 1994 we examined leaf abscission patterns at th ree sites in central South Carolina and found that leaves containing active miners abscised earlier than leaves without active miners. To quantify the effect of leaf abscission phenology on the survivorship and body size of l eaf miners within the abscised leaves, we marked naturally and manually abs cised leaves, left leaves on the ground to over-winter, and then collected leaves before beetles emerged the following spring. We found that beetles i nside leaves that were abscised early in the season were more likely to be killed by predators, and that they produced smaller pupae than beetles with in leaves abscised later in the season. We also evaluated the relationship between adult beetle body size and fecundity; body size of B. tessellatus i s positively correlated with lifetime fecundity and daily oviposition rate indicating that effects of leaf-abscission phenology on beetle body size li kely translate into effects on beetle fitness. We discuss how B. tessellatu s has adapted to variation of leaf abscission phenology of oaks by evolving developmental plasticity that permits successful completion of larval deve lopment over a range of season lengths.