We combined tools of phylogeography, population genetics and biogeographical interpretation to analyse a group of phylogenetically independent lineages (animals and plants) that coexist within the same geographical region, yet under markedly different environments, in order to identify generalized barriers for gene flow. We tested the hypothesis that major geographic features have produced a concordant genetic structure in phylogenetically independent lineages. A rigorous bibliographic search was performed, selecting available molecular information from six taxa occupying distinct southern biomes of South America: Yungas, Prepuna, Puna and northern Monte. We estimated within-population genetic diversity, the genetic structure and haplotype phylogenies to assemble distribution maps of genetic barriers for each species. We found a strong association between genetic variation and latitudinal distribution of populations. We detected a major barrier for six taxa at 27°S latitude and a second one for a group of three species at 25–26°S. Two alternative non-exclusive hypotheses – geology and/or climate – explain concordant genetic barriers in divergent lineages. We suggest that the term ‘biogeographically significant units’ portrays a group of populations of phylogenetically unrelated taxa that inhabit the same geographic region that have been similarly impacted by major physical events, which can be used to identify priority areas in landscape conservation.

Amazonas and San Martin are two of the most densely populated regions in rural Peru and have some of the highest deforestation rates in the country. They are also home to many threatened and endemic species and are considered a high priority for conservation. Under Peruvian law individuals and community groups can create private conservation areas and conservation concessions, and we evaluated the successes and challenges experienced in the creation and management of such areas, using direct observation, questionnaires and key-informant interviews. Our results show that far from being a problem for conservation many rural communities are actively promoting or participating in conservation initiatives on a local scale with landscape-level impacts. These initiatives include land protection, hunting control and reduced deforestation, thus providing effective solutions to threats. The main obstacles we identified in relation to such campesino (peasant farmer) conservation initiatives were the lack of access to support from governmental and non-governmental institutions and to economic resources to fund the extensive bureaucratic processes of registering protected areas. Many campesino communities bypass these restrictions through informal conservation initiatives.