Figure 1

Ecosystem map of northwestern Peru indicating the location of samples. The inset map on the bottom right corner shows the position of Peru (in grey) and of the study region (in black) within South America. Pictures of the habitats of four of the localities (their location indicated by the numbers on the map, which follow the numbering of the pictures) are also included to show the abrupt transition between habitats along the altitudinal range of A. mollis. On the central-north and southeast Peruvian Andes the abrupt transition between forested and non-forested habitats occurs when the humid Andean cloud forest is replaced by an elfin forest [10, 35], which itself is replaced at higher elevations by grasslands called páramos. These grasslands are characterized by high atmospheric humidity, high rainfall, and a continuous layer of short vegetation, dwarf shrubs, and wetlands [36–38]. On the central-south and southwest Peruvian Andes, this abrupt transition occurs between the xeric habitats characteristic of this region and a short forest dominated by quenoa trees (Polylepis spp.), which is then replaced by puna at higher elevations [39]. The puna ecosystem corresponds to steppes of isolated grasses and shrubs, low productivity, and an annual precipitation markedly seasonal and lower than that of the páramo [40–42]. Picture of Menocucho (locality 1 above), courtesy of The Field Museum, [CSZ36381].