DNA barcoding reveals diversity of Hymenoptera and the dominance of parasitoids in a sub-arctic environment

Julie K Stahlhut,Paul Dn Hebert,Matthias Buck,Mark T Merilo,José Fernández-Triana,Sarah J Adamowicz,Cory S Sheffield,John T Huber,M Alex Smith,Thomas Woodcock,Henri Goulet

doi:10.1186/1472-6785-13-2

Abstract

BackgroundInsect diversity typically declines with increasing latitude, but previous studies have shown conflicting latitude-richness gradients for some hymenopteran parasitoids. However, historical estimates of insect diversity and species richness can be difficult to confirm or compare, because they may be based upon dissimilar methods. As a proxy for species identification, we used DNA barcoding to identify molecular operational taxonomic units (MOTUs) for 7870 Hymenoptera specimens collected near Churchill, Manitoba, from 2004 through 2010.ResultsWe resolved 1630 MOTUs for this collection, of which 75% (1228) were ichneumonoids (Ichneumonidae + Braconidae) and 91% (1484) were parasitoids. We estimate the total number of Hymenoptera MOTUs in this region at 2624-2840.ConclusionsThe diversity of parasitoids in this sub-Arctic environment implies a high diversity of potential host species throughout the same range. We discuss these results in the contexts of resolving interspecific interactions that may include cryptic species, and developing reproducible methods to estimate and compare species richness across sites and between surveys, especially when morphological specialists are not available to identify every specimen.

Highlights

Insect diversity typically declines with increasing latitude, but previous studies have shown conflicting latitude-richness gradients for some hymenopteran parasitoids
Molecular operational taxonomic unit (MOTU) counts For the overall Churchill collection (N = 7870), MOTU counts calculated with jMOTU ranged from a high of 1898 to a low of 1221
For the Churchill 2010 subcollection, MOTU counts ranged from a high of 798 (1% cutoff ) to a low of 660 (3% cutoff )

Summary

Introduction

Insect diversity typically declines with increasing latitude, but previous studies have shown conflicting latitude-richness gradients for some hymenopteran parasitoids. Historical estimates of insect diversity and species richness can be difficult to confirm or compare, because they may be based upon dissimilar methods. Previous studies of hymenopteran subtaxa [1,2] and aquatic insects [3,4] have increased previous species richness estimates for this region by integrating morphological and molecular methods for species delimitation. Biodiversity gradients generally show higher species richness at lower latitudes, but parasitoid Hymenoptera have been a commonly noted exception in some earlier literature, at least in comparisons of tropical vs temperate regions [8,9]. A recent study of the boreal and Arctic Microgastrinae (Braconidae) increased by 50% the estimate of species richness for this subfamily in Canada and Alaska [20]

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Discussion

Conclusion