Intraspecific host preferences of mopane moths (Imbrasia belina) in mopane (Colophospermum mopane) woodland

Abstract

Colophospermum mopane trees are a common larval food plant of the mopane moth (Imbrasia belina), which commonly reaches outbreak proportions. Our study  investigated factors determining host tree choice by ovipositing mopane moths within a single host species (C. mopane). Tree size was the primary determinant of oviposition at both the habitat (tall riverine-, medium height woodland- and short-shrub mopane) and individual tree scale, with an increase in the number of egg masses with increasing tree size (estimated by height and canopy volume). Preference for larger trees was only evident at the habitat scale, however, as individual trees were utilized as expected according to the availability of their canopy size class. More detailed tree characteristics, such as leaf size, shoot size, stem number and even leaf chemistry (protein:tannin ratio and total polyphenols) had no influence on host choice. Host choice was based on the most obvious measure of resource abundance, namely tree size, as expected for an outbreak species, since resource availability rather than nutritional quality is likely to be the primary determinant of larval survival.

Key words: host choice, resource abundance, tree size, outbreak, oviposition.