Cryptic speciation of hormogastrid earthworms revealed by mitochondrial and nuclear data

Abstract

Species delimitation of earthworms has been difficult to determine with certainty due to their structural simplicity. We sequenced fragments of COI, 16S, t-RNAs and 28S for 202 Hormogastridae individuals from the central Iberian Peninsula and three outgroup taxa. A morphological constancy was found but a high genetic diversity suggests the presence of five cryptic allopatric species. Results showed a pattern of isolation by distance and a positive but weak correlation between some soil properties (coarse sand and total loam content) and genetic distances, which indicates that these populations may have been shaped genetically but not morphologically, by the environment.