Population genetics of ecological communities with DNA barcodes: An example from New Guinea Lepidoptera

Abstract

Comparative population genetics of ecological guilds can reveal generalities in patterns of differentiation bearing on hypotheses regarding the origin and maintenance of community diversity. Contradictory estimates of host specificity and beta diversity in tropical Lepidoptera (moths and butterflies) from New Guinea and the Americas have sparked debate on the role of host-associated divergence and geographic isolation in explaining latitudinal diversity gradients. We sampled haplotypes of mitochondrial cytochrome c oxidase I from 28 Lepidoptera species and 1,359 individuals across four host plant genera and eight sites in New Guinea to estimate population divergence in relation to host specificity and geography. Analyses of molecular variance and haplotype networks indicate varying patterns of genetic structure among ecologically similar sympatric species. One-quarter lacked evidence of isolation by distance or host-associated differentiation, whereas 21% exhibited both. Fourteen percent of the species exhibited host-associated differentiation without geographic isolation, 18% showed the opposite, and 21% were equivocal, insofar as analyses of molecular variance and haplotype networks yielded incongruent patterns. Variation in dietary breadth among community members suggests that speciation by specialization is an important, but not universal, mechanism for diversification of tropical Lepidoptera. Geographically widespread haplotypes challenge predictions of vicariance biogeography. Dispersal is important, and Lepidoptera communities appear to be highly dynamic according to the various phylogeographic histories of component species. Population genetic comparisons among herbivores of major tropical and temperate regions are needed to test predictions of ecological theory and evaluate global patterns of biodiversity. community ecology | DNA barcoding | phylogeography | plant-insect interactions | speciation

DNA barcoding in floral and faunal research

“…While phylogeography might often best be done with longer sequences and more genes, DNA barcode data offer distinct advantages in many cases, being relatively inexpensive to produce with high throughput methods and having the benefit of large comparative libraries for many taxa (Craft et al, 2010). For example, Craft et al (2010) were able to sample COI haplotypes from 28 Lepidoptera species and 1359 individuals across 4 host plant genera and 8 sites in New Guinea to estimate population divergence in relation to host specificity and geography, a much larger dataset than most previously published phylogeographical analyses, which had tended to focus on single species. The possibilities for community phylogenetic analyses using large quantities of DNA barcode data are exciting, especially in organisms such as hosts and their parasites, and herbivorous insects and their host plants (Kress et al, 2009(Kress et al, , 2010Emerson et al, 2011).…”

“…The work in PNG involves the large-scale rearing of caterpillars to adults, as part of the analysis of ecological and biogeographical patterns among host plants, caterpillars and their parasites (e.g. Miller et al, 2003Miller et al, , 2013Craft et al, 2010;Novotny et al, 2012). The PNG research started in 1994 with parataxonomists taking the first pass at morphospecies identifications, with the aid of a database with images as a working identification tool (Basset et al, 2000(Basset et al, , 2004, then a review in my laboratory based on external morphology and then extensive dissection of genitalia, to purify species concepts and to associate the species concepts with species names based on published revisions or type specimens.…”

“…After an initial assessment by external morphology (including a few splits in morphospecies), we sent up to five individuals per morphospecies to the University of Guelph for sequencing using their standard protocols (Craft et al, 2010;Wilson, 2012). This yielded 227 sequences, covering all morphospecies, deposited in GenBank as accession numbers GU695412-5, GU695431-2, GU695434-66, GU695468-9, GU695504-46, GU695548-58, GU695561, GU695575-80, GU695623-36, GU695639-701, GU695716-7, GU695720-1, GU695745, HM376367-75, HM376381-4, HM422448-56, HM902704-15, HQ947496-7, HQ956600-1 and HQ956613-4.…”

“…The choice of gene regions has focused on species level identification. While barcoding is not intended as a tool for higher classification research or for population genetics research, sometimes the barcoding gene regions have useful information at those levels (Craft et al, 2010). …”

Godfrey M Hewitt (1940–2013): highlights in Heredity from a career in evolutionary genetics

“…Indeed, phylogenetic inference for Hegeter taxa did turn out to have lower resolution than in Pimelia, although with supposedly 'intraspecific' variation achieving as much as 12%, we would now infer, using expectations from the many published barcoding studies (for example, Craft et al, 2010), that the samples used are likely to have been harbouring a substantial number of additional, cryptic taxa. However, analysing incipient radiations on a single island was more challenging than establishing among island relationships, due to a lack of statistical support for some of the putatively monophyletic lineages (see below).…”