Emergence dynamics and bet hedging in a desert bee, Perdita portalis

Bees (series Apiformes, superfamily Apoidea) are most diverse in arid regions of the world. Arid regions (deserts and semi-deserts) are characterized by discrete rainy seasons and extreme temporal variability in rainfall. This paper documents several novel mechanisms by which one desert bee species (Perdita portalis) copes with harsh and unpredictable conditions in xeric habitats. These same mechanisms are likely to be present in diverse bee families. First, diapausing P. portalis follow a bet-hedging emergence pattern, such that only approximately half of the larvae pupate under optimal conditions. Second, emergence is condition dependent such that larvae with a low average body weight are significantly more likely to emerge than are larvae with a high average body weight under similar conditions. Finally, larval emergence is induced by exposure to high humidity (rainfall). The parallels between bee larvae and angiosperm seeds in arid environments are striking. In both cases there is clear evidence of bet hedging, emergence (or germination) is dependent on larval (or seed) condition and rainfall triggers emergence (or germination). These patterns of emergence are significant for understanding bee species diversity in arid regions.