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Afrotropical Hymenoptera Initiative

(Life: Kingdom: Metazoa (animals); Phylum: Arthropoda; Class: Hexapoda; Order: Hymenoptera)

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Motivational overview

Insects are a vital component of any ecosystem from both an abundance and species richness perspective, as they represent the bulk of all animal diversity. From conservation perspectives insects are important pollinators, playing a critical role in the maintenance and evolution of floral species richness, and have the potential to play a valuable role as indicator species in conservation and ecological monitoring. Hymenoptera (wasps, bees and ants) are an extremely important group of insects from both an economic and a conservation perspective. Parasitoid wasps play a vital ecological role as natural controllers of insect populations, including those that are detrimental to agriculture, forestry, and human and animal health, and have vast potential for use in managed bio-control programs. Wasps and bees are also important pollinators, playing a critical role in the functioning of any ecosystem. Some wasps and ants are pests, while others, such as the honeybee, provide beneficial resources. Ants are valuable indicator species in conservation and ecological monitoring. To manage and conserve wasps, ants and bees, we need to inventory the species that are involved, a prerequisite to understanding the role that they play in ecological processes.

The Hymenoptera, particularly the economically important Parasitica, are poorly known from a taxonomic and species richness perspective, with an estimated 20% or less of the extant species known to science. Current estimates of described world hymenopteran species richness tally at 153 088, of these only 18 347 described species are known from the Afrotropical region (van Noort in prep). A conservative extrapolated estimate suggests there are as many as 90 000 species, with a possibility that the total may be as high as 460 000 species in the Afrotropical region alone. With current rates of environmental degradation and habitat destruction, inventory of undocumented species from under-sampled or threatened habitats is a matter of urgency. Comprehensive biodiversity inventory surveys are increasingly being implemented in the Afrotropical region to collect and describe the wealth of new species. However, a major hurdle in the inventory process is the lack of a synthesized taxonomic resource to enable identification of this rich fauna. Pertinent information is available for many groups of Hymenoptera, but this information is scattered through the literature and not readily accessible. The majority of available taxonomic treatments and identification keys are out of date.

A user-friendly identification guide, synthesizing our current state of knowledge, is required to facilitate and streamline the hymenopteran diversity inventory process in the Afrotropical biogeographical region.

Scientific background

Species richness

The Hymenoptera (wasps, bees & ants) are an extremely species rich and abundant group of insects, with only the Coleoptera and Lepidoptera, having more described species (Arnett 1985). However, the perception that the Hymenoptera is less species rich than either the Coleoptera or Lepidoptera is likely to be a function of disparate taxonomic attention, a contention supported by more recent investigations of local insect species richness. In some temperate regions the Hymenoptera is the most species rich of the insect orders (Gaston 1991) and was shown to have the highest species richness in tropical forest canopies (Stork 1991). Globally the number of described species of Hymenoptera was previously estimated to be 115 000 (Gaston 1993; Grissell 1999; LaSalle & Gauld 1993), but a recent assessment places the number of extant described species at 153 088 (Aquiar et al. 2013). Taxonomic knowledge of Afrotropical Hymenoptera, as it is on a global basis, is in its infancy at species level. An indication of just how poor this knowledge is can be gleaned from the current taxonomic status of the Afrotropical Ichneumonidae, which can be used as a benchmark for extrapolation of hymenopteran species richness. An estimated 12 000 species of Ichneumonidae occur in the Afrotropical Region (Townes, 1969), of which only 1 942 have been described (Yu et al. 2012). This means that roughly 16% of the Afrotropical ichneumonids are known to science, a situation indicative of global hymenopteran taxonomy. Based on estimations of the richness of Costa Rica’s hymenopteran fauna in relation to estimates of global hymenopteran richness, it seems likely that around 11-13% of the world hymenopteran fauna has been described to date (Gaston et al., 1996), although other estimates have put the figure as low as 4-5% (Gauld & Gaston, 1995; Stork, 1997). Whichever estimate is more accurate it is clear that the Hymenoptera are taxonomically poorly known. In light of this the estimate that 16% of the Afrotropical ichneumonid species have been described can be feasibly extrapolated to the rest of the Afrotropical hymenopteran fauna which includes 65 families, incorporating 2000 genera and 18 374 species, resulting in an estimation of a total of 115 000 species (van Noort, in prep). The figure could, however range from a relatively conservative 90 000 species up to as many as 460 000 species.

Sampling effort

The proposed guide will address the fundamental lack of knowledge of hymenopteran diversity in the Afrotropical region. Historically there are important Hymenoptera collections from the region that are housed in a number of European Museums including the Natural History Museums in London, Paris, Tervuren and Munich to name a few. There is also a wealth of recently sampled Hymenoptera residing in African and USA museums. Simon van Noort (Iziko South African Museum) and Brian Fisher (California Academy of Sciences) have implemented numerous structured insect inventory surveys across Africa (Gabon, Central African Republic, Namibia, South Africa, Tanzania, Uganda) over the last 25 years. Brian Fisher has also carried out extensive sampling in Madagascar. Bob Copeland affiliated with the National Museum of Kenya and the Systematic Entomology Lab, USDA/ARS in Washington DC is currently running an extensive Malaise trapping program in East Africa. Mike Sharkey (University of Kentucky) recently ran a survey in Congo. The Hymenoptera have been extracted from these samples and sorted to family level ready for processing by respective specialists providing an unparalleled resource from which the systematics and diversity of Afrotropical Hymenoptera can continue to be elucidated. There are also valuable Hymenoptera collections containing a wealth of associated biological data present in the National Collection of Insects (ARC, Pretoria) and the Albany Museum in Grahamstown.

Given the current rates of environmental degradation and habitat destruction the documentation of the fauna and flora of the Afrotropical region is a high priority. An online interactive electronic resource will facilitate the process of inventory and description of the wealth of hymenopteran diversity in the region. This will lead to the compilation of comprehensive databases, which will in turn provide baseline information allowing for informed management decisions for the future conservation of our natural heritage.

Web author Simon van Noort (Iziko South African Museum)


Citation: van Noort, S. 2019. WaspWeb: Hymenoptera of the Afrotropical region. URL: www.waspweb.org (accessed on <day/month/year>).

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