When morphology and DNA are discordant: Integrated taxonomic studies on the Eisenia fetida/andrei complex from different parts of Iran (Annelida, Clitellata: Megadrili)

Abstract

Recent studies have indicated the presence of high cryptic diversity in some clitellate species. Eisenia fetida/andrei is an earthworm species complex that is commonly used in ecotoxicological assays, where undetected differences in contaminant responses between cryptic lineages may lead to confusing or misleading results. Furthermore, because of the key role that earthworm species play in the soil ecosystem, a better understanding of cryptic diversity is necessary to investigate if divergent lineages play different roles within their environments. This can be a serious problem for the reliability of the standard ecotoxicological tests. Traditional earthworm (Annelida, Clitellata: Megadrili) classifications have been mainly built using morphological characters. However, due to the limited number of diagnostic external features, morphological differences alone sometimes do not allow correct identification, especially for sibling taxa which are morphologically similar and whose requirements, overall reproductive performances, and life cycles do not differ significantly. In this study we have demonstrated that the classical morphological distinction between E. fetida and E. andrei does not fit with their phylogenetic structure and we have confirmed that the Eisenia fetida/andrei complex consists of two cryptic sibling species. We have also evaluated the distribution of this species complex according to some scale ecological inferences.