Pine marten vs. stone marten in agricultural lowlands: a landscape-scale, genetic survey

We applied molecular analysis methods to faecal samples to determine both the overall level of occupancy for pine marten (Martes martes) and current stone marten (Martes foina) distribution in the western Po plain. Surveys were carried out in a 10 x 10-km grid, applying a hybrid sampling design. The specific identification of faecal samples was accomplished either by a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method or by amplifying and sequencing a 330-bp mtDNA fragment of the control region (D-loop). Identification success was 93.7 % by the PCR-RFLP and 71.7 % by DNA sequencing. Overall, we collected 47 pine marten records and 24 stone marten records. Thirty-six squares (81.8 %) were found to be positive for at least one marten species, the distribution range of the two species scarcely overlapping. The pine marten was shown to be widespread in lowland areas on the north bank of the River Po, which is probably acting as a barrier to its expansion. In this area, stone marten records were few, while it is was widespread on the south bank of the river. Pine marten expansion may have forced the stone marten to restrict itself to less suitable agricultural and urban areas. Nonetheless, we cannot exclude that stone marten range and/or numbers may being declining as a consequence of pine marten expansion. Six pine marten samples belonged to the Central-Northern European (CNE) phylogroup. The relatively high percentage of CNE martens is consistent with the hypothesis of an ongoing expansion of Alpine and trans-Alpine pine marten populations.