The beautiful complexity of caterpillar-parasitoid food webs

This morning the good friend and colleague Dr. Jan Hrcek sent me a copy of his last paper on caterpillar-parasitoid food webs in Papua New Guinea (PNG). In the past we had collaborated regarding some work on braconid wasps, especially microgastrines. Jan has been researching caterpillars and their parasitoids in PNG for several years and has published quite a few interesting and amazing papers on the topic.

The title of the paper that he sent me today is "Parasitism rate, parasitoid community composition and host specificity on exposed and semi-concealed caterpillars from a tropical rainforest", and was published in Oecologia. It documents parasitism rate and host specificity in a highly diverse caterpillar-parasitoid food web encompassing 266 species of lepidopteran hosts and 172 species of hymenopteran or dipteran parasitoids from a lowland tropical forest in PNG.

I strongly recommend the reading of this paper -which, unfortunately, is not open access, but I guess the interested reader could contact Jan to ask for a copy. Anyone rearing caterpillars and/or dealing with caterpillar parasitoids will find the data reported there useful. I found the comparison between parasitoids of external and semi-concealed host very telling, even though some results are not in line with some preconceived ideas -such as ichneumonid wasps being more generalists than tachinid flies. But preconceived ideas are just that, and field data may change our "old thinking" on parasitoids. This study is based in collecting almost 40,000 caterpillars in the wild, with a rearing success of more than 11,000 adult Lepidopterans and over 1,500 parasitoids (wasps and flies) which represented 12% of parasitism rate. That is certainly a sizable database to extract some valid conclusions -although it may be risky to make generalizations to the world fauna based on only one study site, but I look at this as a very valuable piece of information.

And, of course, I liked the fact that braconids, and especially Microgastrinae, are considered the most suitable group for the biological control of caterpillars (but I am totally biased here ;-)

Most importantly, it is an eye-opener to realize that there has been no resarch like this in the past. Even the most comprehensive studies rearing caterpillars in several regions of the world -Jan cites in his paper a good number of such studies- have not fully addressed the potential differences between parasitoid communities of exposed and concealed (or semi-concealed) hosts. We still know so few about this and many other related topics!

After I read Jan's paper I went to briefly check some of those past researches that he mentioned. And I spent some time analyzing the diverse approaches, merits and/or shortcomings of those studies. There are many logistics difficulties, lack of resources and time constraints that limit what we can do -especially in tropical, hyperdiverse areas... I will try to cover those topics in future posts.

It is never a simple thing this endeavour of rearing caterpillars and study their parasitoids!

New genus of Microgastrinae published today

The journal Zootaxa publishes today an important paper on the microgastrine wasps of the African Reunion Island, in the vicinity of Madagascar. It covers 34 species, 18 of them described as new; as well as the description of a new genus: Dodogaster Rousse, 2013. [The link provided just gives access to the title, abstract and key words, anyone interested in a full copy should contact the authors, because the paper is not open access].

This is the first comprehensive paper dealing with Afrotropical species in almost 50 years, and we can only hope it will be followed by similar works in the near future. As far as I know, there are two other projects underway related to Africa (Arabian Peninsula and Madagascar) which should have papers ready for submitting relatively soon. I plan to cover those efforts in future posts. Nevertheless, much remains to be done yet.

The authors of the paper on the Reunion Island fauna are Pascal Rousse (currently a post-doctoral associate with Simon van Noort in the Iziko Museums, Cape Town, South Africa) and Ankita Gupta (a scientist with the National Bureau of Agriculturally Important Insects, Division of Insect Systematics, in Bangalore, India). Both are talented researchers working with Microgastrinae -among other groups- for the past few years. 

 

Dodogaster, the new genus, is a distinctive one, and it remains to be seen if it is also found elsewhere outside Reunion. We just need to keep working on this amazing group of wasps because there are so many species still awaiting for discovery... Sincere congratulations to the authors!

An elusive genus from the Old World Tropics

While the main emphasis of this blog is on Nearctic braconid wasps attacking caterpillars, from time to time it is nice to expand the geographic coverage. Especially when new information about uncommon species is available to be shared. In this post I will be commenting on the genus Neoclarkinella, described from India in 1996 by Rema and Narendran.

Currently that genus of Microgastrinae comprises three species, two from India and one from China. Those species have been described within the last 20 years or so, and the information on them is extremely scarce, with just seven papers in the scientific literature referring to Neoclarkinella. 

However, the genus is actually quite diverse and spread in the Old World tropics, especially Southeast Asia. In the Canadian National Collection, Ottawa (CNC), I have mounted and studied many specimens (mostly from Thailand, Malaysia, Philippines, China, etc.), representing at least two dozen undescribed species. Many CNC specimens have also been sampled for DNA (CO1 gene) and the resulting barcodes were made freely available recently (in a paper I mentioned in a recent post).

Undescribed species of Neoclarkinella from Thailand, deposited in the CNC (Ottawa), with collection code CNCH2006.