It’s been quite a few years since I visited Portugal during my third year field trip as part of my undergraduate Applied Ecology degree in University College Cork. It was a memorable trip where we learned a great deal about Mediterranean ecology from our UCC lecturers. I believe one of the lasting influences from the trip was from renowned ecologist and philosopher, Matthijs Schouten of the University of Nijegmen, who in addition to having great knowledge of ecology, philosophy and history, has a remarkable ability to teach complex ideas via stories. He introduced us to the history of the region, the movement of the Moors into the system, and how they, among others, influenced and shaped the countryside, culture and civilization of Portugal today.
The Montado Region of Portugal
It was during this trip that we paid a visit to the cork oak-dominated Montado region. It is an open savannah-like landscape managed for centuries as an agri-silvo-pastoral system, dominated by evergreen oak and a rotational grazing system for domestic animals. The main commercial products from the region include cork (at one time, the only way to cork wine bottles) from cork oak trees, wood for charcoal and meat. Crops such as corn were at one time also cultivated in the region, but this trend declined in favour of more intensive practices elsewhere, but small patches are still cultivated for animal feed. Other previously important economical functions of the region included mushroom picking, beekeeping and hunting. It is in essence a high value semi-natural ecosystem owing to its cultural and aesthetic value, high levels of biodiversity (including endemic plant species) and still offers economic opportunities for local residents ranging from agricultural to eco-tourism enterprises.
Due to the recognised high value of the system, the region is now incorporated into a number of dispersed Natura 2000 sites (protected habitats for flora and fauna of European importance). The Natura 2000 network is an ambitious project and covers almost 18% of the EU territory. Farming and other human activities are not excluded from such areas, as humans have been extrinsically linked to such landscapes in Europe for thousands of years, resulting in semi natural habitats, which are important for supporting a variety of human flora and fauna that have adapted to such landscapes.
This method of patch conservation and management is sometimes questioned for its ability to maintain habitat connectivity. A species ability to disperse across a landscape can be disrupted and restricted by barriers in the landscape. Such barriers naturally include seas, lakes, mountains and climate, which is why we find different species in different regions. However, at local level such barriers can also exist, and some of these barriers can be caused by a lack of suitable corridors between habitat patches.
Modelling Connectivity via Landscape Genetics
To test the connectivity and resistance of the landscape for species dispersal and gene flow, a new study by Jacinta Mullins and colleagues from the University of Lisbon, and published in Landscape Ecology used the wood mouse as a model species. Mullins et al. trapped almost 400 mice across an area of almost 4000 km2 (which included two Natura 2000 sites, Cabrela and Sudoeste) in the south-west of Portugal, and collected a small amount of tissue from each mouse from an ear punch for DNA analysis.
Mullins’s DNA analysis showed that for the most part, the wood mouse population formed a single genetic group across the landscape illustrating that as a whole, the population was well connected. Areas of broad leaved forest primarily consisting of native oak and in a few areas, introduced eucalyptus were the best areas for wood mouse dispersal, probably due to the cover that such areas provide. Other good areas included shrubs, hedgerows and abandoned agricultural areas.
Mullin’s study highlighted an area known as Serra de Grândola, situated between the two Natura 2000 sites in the north and the south of the study area, which has yet to receive environmental protection, but represents an important area of connectivity, highlighting its need for inclusion in the Natura 2000 network.
Mullins showed that spatially isolated, but strategically placed Natura 2000 sites facilitated gene flow and dispersal across the landscape, highlighting the importance of broad leaved forest and shrub cover as important connective features. Mullins also points out that their study species was a generalist one with relatively few ecological requirements relative to other more sensitive species or habitat specialists such as the Cabrera vole which may need additional requirements to attain such levels of connectivity and gene flow. Indeed, the authors conclude that multiple species should be studied to assess the wider requirements of the ecosystem to maintain gene flow for a variety of species.
According to Mullins “this paper is part of a larger study where other species including stone marten, fox, salamander and ground beetles are being studied to see if similar landscape genetic patterns are present in other species”.
Realising the Impact of Humans
Thinking back to my days roaming the Montado, it is fascinating to think that something as small as a wood mouse is affected by how we shape and use the landscape. In the case of the Montado, having habitat patches suitable for dispersal and gene flow are important features for wildlife conservation. I’m sure that the maintenance of diverse habitats such as hedgerows and patches of woodland are important for wildlife in other regions too, especially in areas interspersed with agricultural and human activities.
Mullins J, Ascensão F, Simões L, Andrade L, Santos-Reis M, Fernandes C (2014). Evaluating connectivity between Natura 2000 sites within the montado agroforestry system: a case study using landscape genetics of the wood mouse (Apodemus sylvaticus), Landscape Ecology, DOI: 10.1007/s10980-014-0130-z