Internal parasitoid wasps of leaf cone moths. Caloptilia

The diversity of herbivorous insects is often considered a function of host plant diversity. However, studies increasingly demonstrate examples where closely-related herbivores use the same host plant(s), suggesting that partitioning of host plants is not the only mechanism generating diversity. Herbivores sharing hosts may utilize different parts of the same plant; however, resource partitioning is often less clear, calling into question the factors that allow closely-related herbivores to coexist on shared hosts. We examined whether the partitioning of phenology or natural enemy may explain the coexistence of leaf cone moths (Caloptilia; Gracillariidae) associated with maples (Acer; Sapindaceae). Larval activity of 10 sympatric Caloptilia species found on 9 maple species was monitored every 2-3 weeks for a total of 13 sampling events, and internal parasitoid wasps were exhaustively searched using high-throughput sequencing. Blocking primers were used to facilitate the detection of wasp larvae inside moth tissue. We found considerable phenological overlap among Caloptilia species using the same hosts, with two clear peaks in July and September-October. Coexisting Caloptilia species also had grossly overlapping parasitoid communities; a total of 13 wasp species belonging to four families attacked Caloptilia in a non-specific fashion at an overall parasitism rate of 46.4%. Although coexistence may be facilitated by factors not accounted for in this study, niche partitioning may not be necessary for closely-related herbivores to stably coexist on shared hosts.