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A new Darwin parasitoid wasp species from Grootbos Private Nature Reserve

06/12/2023

by Simon van Noort (Iziko Museums of South Africa)

Photograph © Simon van Noort

Since 2018, Iziko entomologist Simon van Noort has been conducting long-term continuous insect inventory surveys at Grootbos using a variety of collecting methods, including Malaise traps, yellow pan traps, pitfall traps, yellow funnel traps, Winkler bag extraction of sifted leaf litter and UV light traps. As part of these surveys three specimens of a new species of a rare Darwin parasitoid wasp in the genus Xorides have been collected. These specimens have emanated from the sorting and identification of the thousands of wasp specimens obtained during these surveys. This new species is so far only known from Grootbos. Together with previous Iziko post-doc and now ARC entomologist, Terry Reynolds, Simon will describe and name the species after Michael Lutzeyer in recognition of his immense conservation efforts. With assistance of Iziko post-doc Mikhaila Gordon and Grootbos entomologist Paula Strauss they will also attempt to figure out the biology and evolutionary relationships of the species. Xorides species are known to be parasitoids of the larvae of wood-boring insects (beetles or moths in the southern Hemisphere). The female parasitoid wasp lays her egg into the grub (larva) of the host insect and on hatching her larva devours the body contents of the host larva eventually pupating and subsequently emerging as an adult wasp.

http://www.waspweb.org/Ichneumonoidea/Ichneumonidae/Xoridinae/Xorides/index.htm 

The two females and a male specimen were collected in the Malaise traps that are running in the Afromontane and Milkwood forests and the host insect species is thus likely to be a wood borer developing in trees present in these forest habitats. It would be super exciting to figure out the ecological network of who is eating who, given that the parasitoid wasp is playing a critical ecological role, controlling the population levels of the host insect that is attacking one or possibly more than one tree species in these forests.

After having had the privilege of receiving a guided tour of the Grootbos Florilegium, we are extremely inspired to provide some relevant content for future artwork additions. If we could figure out who the host is of the new Xorides species, it would make for a fantastic addition to the Grootbos Florilegium, an awe-inspiring resource. We have a vision of the host tree; host insect wood borer; and parasitoid wasp being artistically depicted in a collage that illustrates and connects their ecological interactions, providing insight into the complexity of ecological processes and their roles in the evolution and maintenance of biodiversity. Establishing who the host is, however, is rather like looking for a needle in a haystack, but with the help of Paula in the field we may be able to rear specimens from infested trees in these forests as well as adults of the host insect. This would require some focused ecological investigation including locating infested trees and subsequent monitoring of the emerging fauna, either by bagging the branch/log in the forest or by harvesting and bringing it into an enclosed rearing area.

Simultaneously we will conduct a complimentary approach using DNA analyses to figure out the evolutionary relationships of the species within the genus, as well as to figure out the potential host association through molecular analyses. There are now molecular approaches available that we can use to attempt to detect the host larval DNA present on the adult wasps we have collected. If we can amplify and sequence the host DNA it will help us with determining the host species or at least the family/genus of the host (the barcode library is still insufficiently populated to identify species). Concurrently we will, however, barcode potential host beetles that were also collected in the same Malaise trap samples as the Xorides specimens. If we match the host barcode with one of these beetle individuals, then we will have an actual voucher specimen enabling the determination of the host species.

We gratefully acknowledge the funding received from Grootbos Foundation to pursue these goals: description of the new species and to unravel the ecological relationships of the host insect and the host tree.

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