Latitudinal gradients in ichneumonid species-richness in Australia

Abstract

ABSTRACT.

• 1New data from Australia support previous suggestions that the Ichneumonidae as a whole is not more species-rich in the tropics than the group is in temperate regions.
• 2Part of the overall lack of increase in tropical species-richness results from an absence of large groups whose sawfly hosts are not present.
• 3In comparison with temperate faunas, a larger proportion of tropical ichneumonids are generalists, exploit pupae/prepupae, or have long ovipositors, corroborating predictions made by hypotheses advanced to explain the anomalous tropical diversity of ichneumonids.
• 4Two large groups of pupal/prepupal parasitoids (Pimplinae and Mesostenini) are more speciose in equatorial areas.
• 5Diurnal lepidopterous larval parasitoids, and specialist lepidopterous pupal/prepupal parasitoids are scarcer in the tropics than one might expect, but nocturnal lepidopterous larval parasitoids show an increased species-richness in the tropics. It is suggested that this may be a result of a larger proportion of the suitable host larvae being nocturnally active.