Opportunities of DNA barcoding for taxonomists

A few days ago a paper I co-authored came out in Molecular Ecology Resources. That paper is of relevance to this blog because it releases over 20,000 DNA sequences (gene CO1) from over 2,000 species and 50 genera of Microgastrinae braconid wasps, collected in over 75 countries. The number of sequences made available for free use of the scientific community and the general public it is likely one of the highest ever released. It speaks volumes of the efforts made by the International Barcode of Life or iBOL (among many other institutions, partnerships and initiatives) that are promoting the use of DNA barcoding to help cataloging, studying and describing the amazing diversity of life in this planet. [For those interested in more information about DNA barcoding, there are many resources online to look at, probably an easy way is to just start browsing the iBOL website and related sites mentioned there. Suffice to say that DNA barcoding has many practical applications, but for this post I will only focus on its potential for taxonomists working with parasitoid wasps].

The sequences we are talking about today were amassed during the last eight years and they represent the effort of many scientists and institutions -that explains the long chain of authors being part of the paper. The resources can be accessed using BOLD (The Barcode of Life Data Systems) a magnificent online resource designed to support the generation and application of DNA barcode data.

A view of the BOLD website with summarized information about microgastrinae wasps. Accessed on December 21, 2012. For a larger view and more information on the group click here.

Back to the paper mentioned, it not only releases a significant amount of data, but it also provides suggestions on how to use it in the near future. For example, we considered the sequences to be important in efforts related to: 1) Discovery of cryptic species and description of new taxa; 2) Estimating species numbers in biodiversity inventories; 3) Clarification of generic boundaries within Microgastrinae; 4) Biological control programmes; 5) Molecular studies of host-parasitoid biology and ecology; 6) Evaluation of shifts in species distribution and phenology; and (7) Fostering collaboration at national, regional and world levels. 

All of the above mentioned points are relevant to this blog -and are indeed relevant to biocontrol workers, biodiversity researchers, taxonomists, etc. What is more important: many specimens mentioned in the paper actually come from Canada (~6,000 specimens), or from related areas in the Nearctic or Palearctic regions (+3,000). And that will allow us to advance researches in a way that would not have been possible in the past, before the arrival of DNA barcoding.

Braconid wasps and forest pests in Canada

In a previous post, I analyzed some interesting data coming from the Canadian Forest Pest Management Forum. I could find at least 119 species within 20 families of caterpillars (Lepidoptera) that have been mentioned as pests of some kind to our forests in the past few years. As a taxonomist working with braconid wasps, my next logical step was then to see how many parasitoid species have been recorded out of those 119 lepidopterans.

For such a compilation I used the great resource that is Taxapad. [I have mentioned previously what Taxapad is, and promise that will dedicate a future post to that magnificent database maintained by Dicky Yu (Canada), Cornelis van Achterberg (The Netherlands) and Klaus Horstmann (Germany). Suffice to say for now that Taxapad should be considered as a key tool by many biologists and entomologists, especially those working in biocontrol].

Altogether, 299 species of Braconidae have been found, worldwide, attacking those pest caterpillars. I stress here the world "worldwide" in the sense that those records go beyond Canada to include ANY braconid wasp that has been cited in the scientific literature as a parasitoid of those lepidopterans. It is difficult and very time consuming to separate the sources of information for each individual species and pinpoint the country source. And it is even more difficult to be sure about the certainty of some of those records -some are likely to be wrong for a number of causes. Still, they give us a kind of ballpark estimate about the diversity of parasitoids of forest pest caterpillars. So, for the purpose of this post we can take the worldwide totals as a first approximation to the story of what is going on in Canada.

The first thing that becomes clear is how few we know about the parasitoid of those forest pests. Surely that 299 braconids sounds like an awfully large number of wasps, but the numbers are misleading (see the graph below). Because for 40 (33.6%) of those caterpillar species there is ZERO braconid wasps recorded as parasitoids. That means one third of the caterpillars where we know NOTHING of its parasitoid biology. For another 31 species of lepidopterans (26%) we only know one or two species of braconid parasitoids.

Braconidae species (299) recorded as parasitoids of 119 pests caterpillars of some relevance to Canadian forests. Data source mostly from Taxapad (2012). The numbers on top of each bar represent the actual number of braconids in each category.


On the other side of the spectrum, we have recorded 30 or more braconid parasitoids for 4 species of caterpillars. They represent important pests (such as the spruce budworm or the gipsy moth) which at some point have been the focus of serious rearing efforts from biocontrol workers, resulting in hundreds of research papers. If anything, that should be the example to follow with other pest species that are important as well. 

Canadian Microgastrinae described by L. A. Provancher. Part I

One of the main reasons to have this blog is to share new information on species of Canadian Braconidae which may interest biocontrol workers. That includes photos, descriptions, new distribution and host records, etc. The idea is to prepare "Species Profiles" for as many braconids as possible, in time creating a library that might be freely consulted and used by interested researchers.

I am still trying to deposit the photos in the website of the Canadian National Collections of Insects (CNC), to be able to provide high resolution images and distribution maps. But there are some technical details to be sorted out, and thus I have decided to start posting that info in the blog for the time being. As soon as the Species Profiles can be uploaded in the CNC website I will let the readers know.

Today I am sharing colour pictures of the holotypes of three Microgastrinae species described by León Abel Provancher in the 1880's. The specimens are deposited in the Collections de l'Université Laval, Sainte-Foy, Québec; where many specimens collected by Provancher are well kept and preserved. I thank Gisèle Wagner and Jean-Marie Perron for kindly loaning the specimens. I am also very much indebted to Dicky Yu (CNC) for his extraordinary work compiling the information that makes Taxapad (all distribution and host records provided below are from Taxapad, although I plan to increase that by adding later new information from specimens deposited in the CNC). 

Cotesia acauda (Provancher, 1886). Originally described as "Microgaster acaudus", it is now placed in the genus Cotesia. The head of the female holotype is missing  but otherwise the specimen is in relatively good condition. The species is distributed in eastern North America (Canada: Nova Scotia, Ontario, Quebec; U.S.A: Connecticut, Massachusetts, New Jersey, New York, Pennsylvania, Rhode Island, Virginia, West Virginia, and Wisconsin). It has been reared from two lepidopteran species of the Family Geometridae: Rheumaptera prunivorata and R. undulata.

Forest Pest Management Forum

This week Ottawa hosted, once again, the Forest Pest Management Forum. This is an annual meeting where people from all over Canada (and a few from the United States) gather together to share updated information about forestry pests and its management in the country. 

I have never been to those meetings, but this year a good friend and colleague, Dr. John Huber, from the Canadian Forestry Service and the Canadian National Collection of Insects (CNC) in Ottawa, suggested me to attend. And I was seriously planning to go when some unexpected complications at work prevented me to do it. 

As a "consolation prize" I ended checking the website of the meeting to at least have a sense of what was going on there. First I found a nice compilation of pdf files with the proceedings of past meetings. Anyone interested in the topics of Entomology, Forestry and Pest Management should take the time and revise that valuable source of data. There are tons of information there. One of the most interesting, in my humble opinion, is to see the historical pattern of pests, within the country and in individual provinces. You can follow the evolution of different pest problems that Canadian forests have experienced during the past years by just reading those proceedings.

I went back only seven years, up to the proceedings of the 2005 meeting. But found quite a few interesting details, and this post is to share what I found about Lepidoptera pests.

First of all, I could compile a list of 119 species and 20 families of Lepidoptera caterpillars that have been considered forestry pests in Canada (see detailed list at the end of this post).  Half of all species belong to just two families: Geometridae (27%) and Tortricidaae (26%), and seven families account for three quarters of the species.

Lepidoptera considered as pest of Canadian forests (grand total: 119 species and 20 families). For an explanation of the data sources, see detailed list of species added at the end of this post.

Of course, most of those species are of low significance and cause minor affectations to forestry (or the damage is just too sporadic or too sparse to consider them of real importance). Actually less than a dozen species can be considered as serious pests. Still, this grand total of 119 species should remind us of how quickly things can go wrong with an insect pest. Unfortunately, the next "new pest" outbreak might be just around the corner...

Why Microgastrinae and why they may interest you

When rearing caterpillars, it is common to find some small parasitoid wasps (1.5-8 mm long), often black or yellow and with rather short "abdomen". They belong to the subfamily Microgastrinae (Order Hymenoptera, Family Braconidae), and are one of the most important groups parasitizing butterflies and moths (Order Lepidoptera). These wasps are key components in the biological control of agriculture and forestry pests; and have also been extensively used in biodiversity, ecological, behavioral and molecular studies. However, its narrow host specificity and extraordinary diversity (more than 2,200 described species, with an estimate of 20-40,000 worldwide) presents an immense challenge. 

Addressing the need of more information about those fascinating insects is the main reason of this website. Tips to recognize different genera, species profiles, new biological data, distribution records, and other comments will be provided in following posts. Also, the readers are encouraged to send any question and/or contribution they may have about microgastrines (or any braconid wasp) parasitizing caterpillars. 

Detailed distribution of species and their host records will be compiled from different sources (mostly mined from the large and rich collection available in the Canadian National Collection of Insects, as well as other collections I have visited and/or borrowed material from). Contents intend to be useful to anyone already working or just interested in rearing caterpillars and their parasitoids. It will hopefully interest workers on biological control, bioinformatics, biodiversity researchers, wasp taxonomists, conservation authorities and entomological societies looking for information of species in particular areas. 

What do we know about the largest Apanteles species in North America?

In a previous post it was mentioned that the braconid wasps of the subfamily Microgastrinae comprise specimens ranging from 1.5 to 8.0 mm of body length. The truth is that most of the microgastrines are rather small, usually 2.0 to 3.5 mm long. The "record" of 8 mm is reserved for "giant" specimens of Larissimus, a tropical genus in South America. However, in North America there are very few species that surpass the 4 mm mark, and most of those species are in the genera Microgaster and Protomicroplitis...

Among the largest specimens of microgastrine wasps in North America, the species Apanteles crassicornis stands on its own with around 5 mm of length. That species is also noteworthy because of its elongate face and enlarged glossa, which is supposedly related to the gathering of pollen or nectar. 

Apanteles crassicornis (Provancher, 1866). Antennae and legs are missing some segments. Photo of the holotype of the species, deposited in Laval University, Quebec.

An overview of braconid wasps in Canada

Braconid wasps are the second largest group within Hymenoptera (the insect order that comprises bees, stinging wasps, ants, sawflies and parasitoid wasps). The last version of Taxapad records 956 described species of Braconidae for Canada. Of course, that is just the total of species that have been given scientific names by taxonomists. But it does not account for the many undescribed and/or unrecorded species that remain to be discovered. How many species are actually out there in the Great White North?  

Main subfamilies of Braconidae (Hymenoptera) in Canada. Total number of species: 956 [based on Taxapad (2012)].

While it is impossible to be certain, it is likely that at least twice the current figure, or about 2,000 species of braconid wasps will be found in Canada when all is said and done. 

Think about that for a second. The only group of living things (excluding perhaps microorganisms) that is more diverse than braconids wasps is yet another group of parasitoid wasps: Ichneumonidae, which happens to be the sister group to braconids. Ichneumonid wasps currently comprise almost 3,000 species in Canada (2,834, according to Taxapad). Nothing else comes even close to those figures -and the same situation is probably found in most other areas of the planet. We are talking here about the biodiversity heavy-weights.

Two thousand species of braconid wasps in Canada is a great number, and it amazes to think that we are still missing ONE THOUSAND species to be recorded -let alone studied in detail! The vast majority of those tiny wasps play a capital role in the natural regulation of herbivores -which might otherwise become pests of our crops and forests. Thus, this is not only a matter of scientific inquiry, but also a practical issue with economical implications.