DNA barcoding reveals extent of arthropod biodiversity
The once impossible task of identifying all specimens within a large field collection of arthropod has been remedied using DNA barcoding. For areas of incredibly high arthropod biodiversity, such as Parque Nacional Cusuco in Honduras, DNA barcoding has revealed more than 1700 species so far.
By sequencing a short, standardized gene region, DNA barcoding permits both the identification of known species and the discovery of new ones. For almost all animal groups, a 648 base-pair region within the mitochondrial gene cytochrome c oxidase 1 works as a barcode for species discrimination. This powerful new and readily automated approach is increasing our capacity to monitor and manage biodiversity.
Global Malaise Trap Program
The Global Malaise Trap Program was initiated in 2012 using DNA barcoding to aid in the assessment of global arthropod diversity patterns. This program currently involves standardized sampling at 30 sites around the world, including Honduras. A Malaise trap is a tent-like apparatus which traps insects as they fly into or crawl up the tent wall before being funnelled into a collection bottle. Malaise traps have proven to be highly effective sampling devices for a significant fraction of overall arthropod biodiversity.
In the summer of 2012, Malaise traps were put out in two different areas of broad leaf forest within the research sites Base Camp and Guanales of Parque Nacional Cusuco, Honduras. The two areas were roughly 2 km apart with a 300 m elevation difference. Samples were collected for 8 weeks from mid-June to mid-August and subsequently analyzed at the University of Guelph.
Time and Cost Efficiency
Analysis began with specimen sorting. Large-bodied specimens were pinned and a leg removed for DNA extraction. Small-bodied specimens were placed directly into 96 well-plates for DNA analysis. Non-destructive DNA extraction protocols ensured that specimens were not destroyed. Following sequence analysis, specimens were imaged and preserved as vouchers at the Biodiversity Institute of Ontario. Vouchers are linked to sequences, images, and other collection data and all of this information is publicly available online (www.boldsystems.org). In total, 5355 Honduran specimens were barcoded within a two month period at a cost of roughly $2 Canadian each.
Arthropod Diversity within Honduras Malaise Traps
Samples from both sites in Parque Nacional Cusuco were similar in terms of the three major arthropod classes: Insecta (93%), Arachnida (3%), and Collembola (4%). In addition, five insect groups dominated in both sites: Diptera (56%), Hymenoptera (20%), Coleoptera (5%), Lepidoptera (5%) and Hemiptera (4%).
The barcode results revealed startling diversity – the 5355 specimens from the park included 1720 different species. The collections from Base Camp (elevation of 1500 m) and Guanales (elevation of 1200 m) included 563 and 1265 species respectively (Figure 1). Despite their small separation in distance and elevation, there was just 6% species overlap between the two sites! The majority of overlapping species were insects (90%) of which Diptera (61%) dominated. Coleoptera (15%), Hymenoptera (13%) and Lepidoptera (6%) showed significant overlap whereas no overlap was observed within Hemiptera (Figure 2).
Parque Nacional Cusuco is a 23,400 ha protected area in the Merendon Mountains of northwest Honduras, part of the Meso-American biodiversity hotspot. It consists of a complex landscape with elevation ranging from 60 m to 2242 m. If sites just two kilometers apart show such great divergence in their species composition, one can only begin to imagine the full richness of this biodiversity hotspot given the heterogeneity of the landscape as a whole.
The 2012 Malaise Program has hugely expanded our knowledge of arthropods within Honduras, formerly a diversity poorly characterized. The data gathered will play a crucial role in the creation of an online reference library. However, most exciting is the ability to place Honduran biodiversity in a global context as results become available from other countries participating in the Global Malaise Program.
This preliminary work will establish the baseline for a new method of ecosystem management within the country. As technology advances, wide-scale screening of environmental samples will be possible at low cost, allowing direct measurements of biodiversity. New samples will be queried against the reference library in order to build up a reasonably comprehensive picture of the regional dynamics of biodiversity.
Honduras is in the grip of a conservation crisis as its precious natural resources are ravaged by development. By harnessing the power of DNA barcoding, rates of biodiversity discovery and description will be hugely accelerated for the improvement of management practices.