Integrative study of various populations of Aporrectodea rosea (Savigny, 1826) based on morphological and molecular analyses (Oligochaeta: Lumbricidae).

Background: Aporrectodea rosea (Savigny, 1826) is a common earthworm species found in the temperate regions of the Holarctic region. This species exhibits significant intraspecific variation, and several cryptic genetic lineages having been described. The high genetic diversity is likely due to its ecological plasticity and adaptability to different environmental conditions. Integrative approaches that combine morphological, ecological, and molecular data have proven to be useful in resolving taxonomic uncertainties in earthworm species. In this study, we investigated the genetic and morphological diversity of several populations of A. rosea from Iran. By combining molecular analyses with morphological and ecological data, we evaluated whether the observed diversity can be linked to phylogeographic origins (Eurosiberian vs. Mediterranean regions). This integrative approach provides new insights into the taxonomy and evolutionary history of A. rosea, contributing to a better understanding of earthworm biodiversity in the Holarctic region.

Methods and results: We evaluated the molecular variation within A. rosea by analyzing both nuclear and mitochondrial markers. The phylogenetic results were combined with morphological data, ecological information, and genetic distances using the COI K2P method to assess species delimitations. Cluster analysis revealed the existence of two distinct morphotypes: a reddish morphotype associated with organic-rich, woodland habitats, and a pale morphotype found in drier grassland environments. Our molecular analyses involving sequencing the mitochondrial COI gene and the nuclear histone H3 gene confirmed the existence of two lineages within A. rosea: a Eurosiberian lineage and a Mediterranean lineage.

Conclusions: Our analyses confirmed that nearly all specimens collected from Iran fall within the two established lineages: Mediterranean and Eurosiberian. The observed genetic differences between the two morphotype samples can be related to their phylogeographic origins (Eurosiberian/Mediterranean).