Cryptically galled infructescence: a new sheoak gall type in Allocasuarina luehmannii and Casuarina pauper (Casuarinaceae)

Abstract

Insect galls formed within the infructescences (cones) of Allocasuarina luehmannii and Casuarina pauper in southern New South Wales, Australia, are described. The galling was internal within the infested cones, which were small and irregularly developed, but could appear superficially normal except that they had a higher than normal proportion of samaras retained on bracteole dehiscence. Cross-sections revealed abnormal morphology and wasp larval chambers. All exit holes found were between bracteole pairs of either fertile or infertile florets. Emergent wasps were tentatively identified as Eurytoma sp. sensu lato (Hymenoptera: Eurytomidae). These cryptically galled infructescences represent a previously undescribed gall type in the Casuarinaceae and, for Eurytoma, potentially a rare instance of phytophagy in Australia. Infested cones were found in a season when normal cones in this drought affected area were not easily found. It was concluded that this phytophagy could negatively impact the regeneration potential of two already compromised sheoak species.