THE EMPIRICAL QUESTION OF THRESHOLDS AND MECHANISMS OF MATE CHOICE

Theoretical discussions concerning how animals might best sample and s elect mates have suggested that individuals could base decisions eithe r on a sample of mates (sampled-based decisions) or on a threshold of comparison (threshold-based decisions). Recent theoretical work demons trates that threshold-based mating decisions generate higher expected fitness than sample-based mating decisions when search costs exist. Em pirical results from most unmanipulated systems, however, either concl ude that females make sample-based decisions or are inconclusive. A fe w experimental studies designed to detect mating thresholds purport to demonstrate threshold-based choice but an examination of these studie s indicates such conclusions were premature. We believe that few examp les of threshold-based choice exist because protocols designed to iden tify mating thresholds were often inconsistent with models of threshol d choice. We suggest that future empirical work strive not to document mating thresholds per se. Rather, future work might best reveal decis ion rules by manipulating the distribution of quality among potential mates; such manipulations predict uniquely how females using sample-ba sed and threshold-based decision rules should behave.