Power of a multidisciplinary approach: use of morphological, molecular and digital methods in the study of harpacticoid cryptic species

Abstract

A multidisciplinary approach amenable to auto- mation and involving digital techniques in conjunction with detailed taxonomical observations and molecular genetic analyses was used to assess the phenotypic and genetic vari- ability of 3 harpacticoid copepods previously identified as Cletocamptus deitersi. C. deitersi may be the most problem- atic species among congeners due to its intraspecific morpho- logical variability. Specimens of C. deitersi collected from inland and coastal habitats in Alabama, California and Louis- iana were analyzed to determine the degree of separation between specimens. Levels of extreme genetic differentiation at both mitochondrial and nuclear loci and incipient but congruent morphological differences among specimens of the 3 populations strongly suggest that each genetic lineage belongs to a different species. Discrimination among species was also detected using a digital correlation method invariant to position and rotation. This analysis involved an algorithm using the square module of the fast Fourier transform. Digital images of specimens from the 3 populations were processed to obtain their diffraction patterns. To discriminate among species, all diffraction patterns were correlated with a special filter containing different random fixed views of each species. Results indicate that new identification methods of micro- scopic organisms could be developed to reduce the amount of time of direct observation. In order to build these methods on a solid taxonomic validation, it is necessary to implement a multidisciplinary approach in which expertise in taxonomy, molecular biology and digital processing work in conjunction to maximize their reliability and precision.