January 16, 2013

Open for business: Apanteles fumiferanae

The microgastrine wasp Apanteles fumiferanae Viereck is one the most important Braconidae -as forest pest management concerns- in North America. Based on specimens available in collections, it is the most common braconid parasitoid reared from the spruce budworm Choristoneura fumiferanae (Harris) (Lepidoptera: Tortricidae), which in turn is one of the major forest pests in the region.

Very few pests rival the spruce budworm in importance, and thus this lepidopteran species has been extensively studied over the years. There are hundreds of papers covering details of its biology, ecology, damage and control (biological, chemical, integrated). As part of those studies, for many years its caterpillars have been collected and reared for parasitoids, providing perhaps the best information ever available for a single forest pest in the Neartic. And still there are many details to be researched and understood!

Some recent papers summarize what we know until now. For example, an excellent analysis of the complex relationships between the spruce budworm and its parasitoids/hyperparasitoids/pathogens, was published by Eldon Eveleigh (Canadian Forest Service, CFS) and ten co-authors in 2007; it can be freely downloaded here. Reading that paper will open anyone eyes regarding the complexities of the food webs in a temperate forest. I especially recommend to check Figure 1 of that paper (which is not for the faint of heart!). One can only image similar analysis for a tropical forest... it is just mind boggling.

From a parasitoid perspective, John Huber, also from the CFS, led a team of four taxonomists to produce a series of papers covering all major groups of parasitoids of the genus Choristoneura in the Nearctic region: chalcid wasps (Huber, 1996), tachinid flies (O'Hara, 2005), ichneumonid wasps (Bennett, 2008) and braconid wasps (Fernández-Triana and Huber, 2010). Those works provided numerous illustrations, keys, and taxonomic notes to help identifying the large fauna of currently known parasitoids (230 species within 106 genera and 13 different families; see figures 155-157 and Discussion in Fernández-Triana and Huber (2010). [Unfortunately those papers can be downloaded for free, except for their Abstracts. However, being one of the authors of the braconid paper, I have plenty of reprints for that one, and would be pleased to send copies to anyone interested].

Which bring us back to the topic of this post: Apanteles fumiferanae. The species is widely distributed in the Nearctic region (there is also a record from Poland, but that might be incorrect). It has been reared from caterpillars of 17 lepidopteran species representing 4 families (although some of those early records, from historical references, are likely to be wrong). Close to one hundred scientific papers have dealt with that wasp species, and there is reason to believe more are needed... Why? Because A. fumiferanae actually comprises a complex of morphologically cryptic species (i.e. species that cannot be easily separate based on external morphology, yet are distinct biological entities).

This is nothing new. After the description of the species, in 1912, a couple of papers have split A. fumiferanae in several species. In 1974, the Canadian William R. M. Mason, a great braconid expert, described four new species of Apanteles from Choristoneura, based on a study of several hundred reared specimens. And the 2010 paper by Fernández-Triana and Huber mentioned above reported yet another three different species -among samples of over 2,000 reared Apanteles examined. Two of those species were then described as new in another paper (which can be freely downloaded here). [And it only made sense for me to name one of those new species as Apanteles huberi, after John Huber, for his tireless efforts pushing the rest of us to produce the series of papers on Choristoneura parasitoids].

Thus, we already know that what was thought to be one species (Apanteles fumiferanae) at the beginning of the XX century, is actually several species. Some are host-specific (for example, Apanteles huberi is only found in British Columbia parasitizing Choristoneura bienis). Others not. But still A. fumiferanae remains with too many hosts associated, which strongly suggest there may be additional species hidden under that name. In fact, that is implied when looking at data from DNA barcoded specimens (I already wrote a previous post about the importance of DNA barcoding as another tool to be used by taxonomists). Based on data from specimens deposited in several Canadian collections, there might still be a couple of additional  species within this complex awaiting discovery and description. And that does not even include specimens from United States collections, which are likely to have additional species from southern areas in North America.

K2P tree of 97 specimens of "Apanteles fumiferanae" deposited in several Canadian collections. Click on the image to see a larger file. Based on data from BOLD (http://www.boldsystems.org/) accessed on January 16, 2013.

All of the above is tremendously important because of the current situation in Canadian forest. It is thought that the new outbreak of Choristoneura fumiferanae is already on its way in parts of Eastern Canada (for more information on those outbreaks and the latest news on that, check the Forest Pest Management website, which was previously mentioned in this blog). That means many researchers across the country soon starting to rear spruce budworm caterpillars (or are already doing that!). Thus, we will be getting more material that must be compared against historical specimens from previous outbreaks. It is not unlikely to think that the new material to be gathered will help to solve some of the cryptic species that remain to be discovered. And the biologists working with the control of the spruce budworm -and related species of Lepidoptera- would want to know more about what they are rearing. There are LOTS of opportunities here to advance yet another chapter in the far-from-being-done saga of Choristoneura and its parasitoids!

Because of its importance as a key parasitoid, Apanteles fumiferanae (sensu lato) stands out as something to be studied with more details.We will continue the topics of this post in following contributions; where more details about the species (and other related Apanteles) will be provided, including photos and detailed distribution based in collection records.

I welcome anyone in Canada/US rearing caterpillars of Choristoneura (and related species), and getting braconid wasps of the subfamily Microgastrinae, to send their material here (the Canadian National Collection, in Ottawa) for identification.

In other words, we are "Open for business". Well, not in the sense of actual business (there is no money involved) but in the sense of offering free help to interested researchers.

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