Defining species using DNA sequences
Delimiting species is at the core of multiple disciplines and practices in science and society. Our study published in Systematic Entomology proposes a new approach to standardize species definitions in butterflies, combining genetic data and taxonomic knowledge using a Bayesian framework.
Photo: Pierella hyceta hyceta from Peru, Pasco Region, Cañón de Huancabamba, 29.vii.2017. ©Markéta Aubrechtová.
Species are the currency of biology. Yet biologists have a difficult time to define and delimit them. The multispecies coalescent (MSC) is a model that jointly considers population-level processes and evolutionary patterns at large temporal scale in a single statistical framework. MSC can be a faster and reproducible approach to delimit species using genetic data. However, without any external information, the MSC is at risk of erroneously inflating species diversity when relying solely on DNA sequences; the MSC is not able to distinguish species from subpopulations with a long non-breeding history.
Matos-Maraví and colleagues (2019) evaluated the performance of the MSC illuminated by taxonomic knowledge to delimit species, a novel approach that aimed to bridge traditional taxonomy with recently developed coalescent-based methods. This synergistic approach was used to study butterflies classify in the tribe Haeterini—common insects, some of them having transparent wings, from undisturbed rainforests of the American tropics. The authors added species diversity estimates made by numerous researchers over the last 150 years directly to the MSC Bayesian framework as prior distributions. The statistical support for the resulting species hypotheses were then compared using a Bayesian model adequacy test so-called Bayes factors. Altogether, this paper provided a solid background for the recognition of 22 species in the tribe Haeterini. Importantly, this novel pipeline overcomes limitations in both traditional taxonomy and molecular-based methods, by recognizing crypic species and by distinguish them from structured populations.
Matos-Maraví P., Wahlberg N., Antonelli A., Penz C. (2019). Species limits in butterflies (Lepidoptera: Nymphalidae): Reconciling classical taxonomy with the multispecies coalescent. Systematic Entomology, doi: 10.1111/syen.12352