Novel host associations and habitats for Senecio-specialist herbivorous insects in Auckland

Abstract

We studied the genus- and species-specialist monophagous herbivorous insects of Senecio (Asteraceae) in Auckland, New Zealand. With the exception of the widespread S. hispidulus, the eight native Senecio species in mainland Auckland (two endemic) are typically uncommon and restricted to less modified conservation land. However, 11 naturalised Senecio have established and are often widespread in urban and rural habitats. Three endemic Senecio‑specialist herbivores – Nyctemera annulata, Patagoniodes farnaria, and Tephritis fascigera – formed novel host associations with naturalised Senecio species and spread into modified landscapes. Host associations for these species were not related to whether Senecio species are naturalised or native. However, the abundances of Patagonoides farnaria and Tephritis fascigera were significantly higher in wildland habitats than rural or urban habitats, and wildland Senecio were on average 1.4 times more likely to experience >5% folivory then urban conspecifics.