Pattern of richness and distribution of groundwater Copepoda (Cyclopoida: Harpacticoida) and Ostracoda in Romania: an evolutionary perspective

Abstract

It is assumed that the south-eastern Europe and especially the Romanian Carpathians were important regions for surface and underground invertebrates survival during glacial periods and acted as a source of post-glacial colonization processes. We analyzed data from 233 georeferenced records for 164 species of groundwater copepods and ostracods from Romania and used a comparative approach to recognize the determinants of the regional-scale richness, endemism, and distribution patterns, with a primary focus on species from the Carpathian Mountains. In addition, we examined the driving forces for the observed pattern of distribution and richness linked to contemporary (groundwater habitat fragmentation and heterogeneity, climate, vegetation) and historical (past climate and vegetation) environmental conditions. Our analyses showed that: (1) species richness was high, irrespective of habitat heterogeneity, in karst and non-karst areas; (2) the main driver accounting for high species richness in the karst landscape was the rainfall regime (> 1350 mm per year), whereas, in non-karst areas, it was woodland vegetation; and (3) there was significant species richness and richness of phyletic lineages in hypothetical forest glacial refugia of the Carpathian arc. The combination of the distribution pattern, diversification, and evolution of stygobite lineages provides reliable evidence for species persistence in the Romanian groundwater during Pleistocene.