Substratum karstificability, dispersal and genetic structure in a strictly subterranean beetle. ferreri

Aim The deep subterranean environment is an ideal system to test the effect of physical constraints on the ecology and evolution of species, as it is very homogeneous and with simple communities. We studied the effect of substratum karstificability in the dispersal of the strictly subterranean Troglocharinus ferreri Reitter (Coleoptera, Leiodidae) by comparing the genetic diversity and structure of populations in limestone (more soluble) and dolostone (less soluble) in the same karstic system.Location Troglocharinus ferreri is only known from ca.100 vertical shafts in an area of less than 500 km2 SW of Barcelona (Spain).Methods We sequenced mitochondrial and nuclear markers of a representative sample to identify main lineages within T. ferreri and estimate their temporal origin, and used mitochondrial data of 129 specimens from 41 caves to reconstruct their demographic history and estimate dispersal among caves.Results Troglocharinus ferreri diverged from its sister in the Early Pliocene, with an initial divergence of the sampled populations in the Early Pleistocene. The best demographic model was a constant population size with a fast population increase in the middle Pleistocene. The ancestral population was likely in limestone, with a probability of transition from limestone to dolostone triple to that from dolostone to limestone, suggesting a higher permeability of limestone to the transit of individuals. Populations in dolostone caves had lower gene flow between them and higher genetic variability than those in limestone, although the low genetic variability for the studied markers and the lower abundance of dolostone caves rested statistical power to the results.Main conclusions Our results point to the physical characteristic of the substratum as a determinant of dispersal and gene flow, potentially conditioning the long-term evolution of subterranean biodiversity.