Preserving the biodiversity of freshwater ecosystems in a scenario of increasing desertification: lessons from genetics

Abstract

The European Union is faced with the challenge of environmental alteration. In recent years, human activities and accelerating climate change have had a great impact in many regions, with the freshwater ecosystems of Mediterranean countries being hit particularly hard. Spain has the greatest biodiversity of Europe. The country’s maritime barriers, the Pyrenees, and its orographic and climatic peculiarities, invest it with its unique biogeographic characteristics, which together have led to the appearance of many endemic freshwater species. However, the freshwater ecosystems of Spain are suffering great modification at the hands of climate change (some Mediterranean regions now receive 20% less rain than a century ago), environmental degradation, habitat fragmentation, the rise in human demand for water, and a range of human activities; together these factors have contributed to a notable increase in the size of Spain’s arid and semiarid regions, and to changes in its biodiversity. The country’s aquatic biodiversity is now threatened, and the Spanish Ministry of the Environment and the Rural and Marine Environments and the Biodiversity Foundation have seen the need to launch several biodiversity conservation programmes. A major goal of such programmes should be to preserve genetic variability. Indeed, knowledge of the levels and patterns of distribution of genetic diversity in populations of freshwater species is critical when making conservation management decisions. Our group is conducting research into the genetic variation, and its distribution, in two cornerstone freshwater groups: the genus Barbus, which has the greatest species diversity of all Iberian fish genera, and the white-clawed crayfish Austropotamobius pallipes. The latter was once widely distributed throughout most of the country’s limestone basins; now much more rare, it enjoys protection under regional, national and European legislation. The ecological importance and the conservation interest surrounding the above organisms led us to analyse the genetic variability of their populations over their entire distribution ranges. To obtain as complete a picture as possible, nuclear (RAPD, ISSR) and mitochondrial (coI, cyt b and 16S genes) molecular markers were studied. Evidence is provided suggesting that the genetic variability in barbel species is low. The genetic variation seen for A. Pallipes, however, was slightly higher than expected, allowing some hope of its recovery. We are also generating a genetic database for both groups; this could serve as an aid to managers and policy-makers involved in freshwater conservation.