Species are central for understanding the diversity of life, yet there remains considerable uncertainty in how to define them. Through work on bdelloid rotifers, insects, bacteria and plants, we have developed new methods for identifying independently evolving units of diversity from broad-scale genetic data – the kind of data being collected by DNA barcoding projects. Our main interest is to identify the processes causing independent evolution, especially reproductive isolation and divergent selection, and to determine whether they do indeed act to generate simple units (species) or whether more complicated models of diversity are required.
Initially developing methods applicable to DNA barcoding data, we now focus on multilocus and whole genome approaches that are still applicable to broad-scale sample (i.e. 1000s of individuals within clades).
Our methods have been used to delimit species and estimate diversity from DNA barcodes, as in this inventory of a) mayflies, b) termites, c) butterflies, d) dung beetles and e) diving beetles from Madagascar (Monaghan et al. 2009)
Fujisawa, T., Aswad, A. and Barraclough, T.G. 2016. A rapid and scalable method for multilocus species delimitation using Bayesian model comparison and rooted triplets. Systematic Biology. 65: 759-771.
Fujisawa T, Barraclough TG. 2013. Delimiting Species Using Single-locus Data and the Generalized Mixed Yule Coalescent (GMYC) Approach: A Revised Method and Evaluation on Simulated Datasets. Syst Biol. 62: 707-724.
Tang, C.Q., Leasi, F., Obertegger, U., Kieneke, A., Barraclough, T.G., and Fontaneto, D. 2012. The widely used small subunit 18S rDNA molecule greatly underestimates true diversity in biodiversity surveys of the meiofauna. Proc. Natl. Acad. Sci. USA. 109:16208-12
Barraclough T.G. 2010. Evolving entities: towards a unified framework for understanding diversity at the species and higher levels. Phil. Trans. R. Soc. Lond. B. 365: 1801-1813.
Monaghan, M.T., Wild, R., Elliot, M., Fujisawa, T., Balke, M., Inward, D.J., Lees, D.C., Ranaivosolo, R., Eggleton, P., Barraclough, T.G., and Vogler, A.P. 2009. Accelerated species inventory on Madagascar using coalescent-based models of species delineation. Systematic Biology 58: 298 – 311
Barraclough, T.G., Hughes, M., Ashford-Hodges, N., and Fujisawa, T. 2009. Inferring evolutionarily significant units of bacterial diversity from broad environmental surveys of single-locus data. Biology Letters 5: 425-428.