Inflorescence Damage by Insects and Fungi in Native Pili Grass ( Heteropogon contortus ) versus Alien Foundation Grass ( Pennisetum setaceum ) in Hawai'i

Abstract

The success of introduced invaders has often been attributed to their release from natural enemies. We compared rates of seed and ovule destruction by insects and fungal pathogens in an alien invader, fountain grass (Pennisetum setaceum), and a declining native competitor, pili grass (Heteropogon contortus), to determine whether the invader experienced less damage from natural enemies. Inflorescences were sampled on O'ahu from three sites on three dates, and seeds and ovules were inspected for insect damage or pathogen infection. Total seed and ovule destruction was significantly lower in alien fountain grass at all times and sites, with the exception of one sample date on Ka'iwa Ridge when very little damage (