SPECIES DELIMITATION AND GLOBAL BIOSECURITY

BOYKIN, L. M. (1), Armstrong, K. A. (1), Kubatko, L. S. (2), De Barro, P. (3)

(1) Bio-Protection Research Centre, Lincoln University, New Zealand
(2) Departments of Statistics and Evolution, Ecology, and Organismal Biology, The Ohio State University, United States of America
(3) CSIRO Entomology, Indooroopilly, Australia

Plenary Talk, Opening Plenary, Elder Hall, Wednesday, 11:20 to 11:30

Species delimitation directly impacts on global biosecurity. It is a critical element in the decisions made by national governments in regard to the flow of trade and to the biosecurity measures imposed to protect countries from the threat of invasive species. Here we outline a novel approach to species delimitation, “tip to root”, for two highly invasive insect pests, Bemisia tabaci (sweetpotato whitefly) and Lymantria dispar (Asian gypsy moth). Both species are of concern to biosecurity, but illustrate the extremes of phylogenetic resolution that present the most complex delimitation issues for biosecurity; B. tabaci having extremely high intra-specific genetic variability and L. dispar composed of relatively indistinct subspecies. This study tests a series of analytical options to determine their applicability as tools to provide more rigorous species delimitation measures and consequently more defensible species assignments and identification of unknowns for biosecurity. The analytical approaches included the commonly used Kimura two-parameter (K2P) inter-species distance plus four more stringent measures of taxon distinctiveness: 1) Rosenberg’s reciprocal monophyly, P(AB); 2) Rodrigo’s P(randomly distinct); 3) genealogical sorting index, gsi; and 4) General mixed Yule Coalescent (GMYC). For both insect datasets, a comparative analysis of the methods revealed that the K2P distance method does not capture the same level of species distinctiveness revealed by the other four measures; in B. tabaci there are more distinct groups than previously identified using the K2P distances and for L. dipsar far less variation is apparent within the predefined subspecies. A consensus for the results from P(AB), P(randomly distinct) and gsi offers greater statistical confidence as to where genetic limits might be drawn. Overall, the approach ("tip to root") is recommended where careful consideration of species delimitation is required to support crucial biosecurity decisions based on accurate species identification.

Keywords: Insects, Quarantine/Plant Protection, Data Analysis