Arid areas have a comparatively narrow range of habitat types, with restricted variation in environmental parameters, leaving narrow boundaries for phenotypic variation to correlate with ecological ...variables. To test this presumption, we explored variation in size and shape of the mandible in the dwarf fat-tailed jerboa (Pygeretmus pumilio (Kerr, 1792)) under the constraints of a rigorous desert environment. Size varied significantly and predictably with geographic position and demonstrated a strong, nonlinear longitudinal pattern. Moreover, size was associated with several other climatic variables but not with soil properties or with proxies for primary productivity. Our results suggest that for rodents exposed to rapid and extreme changes, larger size may have multiple advantages, notably in maintaining euthermia during cold nights and efficient water metabolism under aridity stress, in accumulating fat reserves for hibernation, and in digging deeper burrows, better protected from surface extremes. Shape varied clinally along the longitudinal transect, and the pattern was affected more by temperature than by precipitation. We conclude that the success of dwarf fat-tailed jerboa in occupying an extensive geographic range relies on their ability to meet environmental heterogeneity through cohesive and diverse responses, including physiology, behaviour, life-history traits, and morphological plasticity.
The invasiveness ofRobinia pseudoacacia, one of the most invasive alien tree species in the agricultural landscapes of Central Europe, was studied in relation to its colonization of various soil and ...habitat types. The study area was a traditional agricultural landscape in Goricko Landscape Park (Slovenia), a hilly region, where half the territory is covered by forests and where R. pseudoacacia is also common. Habitat mapping in the field with a resolution of two meters was applied and further elaborated in GIS. It revealed 1307 patches colonized by R. pseudoacacia and belonging to 11 habitat types, covering 0.6% of the total study area. The most widespread were pure R. pseudoacacia stands, representing 69% of the total patch area. R. pseudoacacia is also abundantly present in small woodlots (19%) and in lowland and collinar riverine willow scrub (6%). The patches vary little in fractal dimension; the elongation index is highest in lowland and collinar riverine willow scrub, stream ash-alder woods and mixed stands. The most frequently invaded soil is pseudogley, with more than 38% of the total surface, followed by 21% for fluvisol and 17% for eutric cambisol. We confirmed that distance from nearest woodland is important, since almost 32% of the invaded patches are found at a distance of 1-100 meters from closed woodland.
