Rubén D. Quintana

CHARACTERISTICS OF NEST SITES OF SKUAS AND KELP GULL IN THE ANTARCTIC PENINSULA

Abstract We investigated nest-site selection of sympatrically breeding skuas (Catharacta spp.) and Kelp Gulls (Larus dominicanus) in the Antarctic Peninsula. We evaluated habitat preferences of nesting skuas and gulls in a patchy landscape by counting the numbers of nests in each of ten habitat types. Additionally, we evaluated the importance of 11 habitat variables (known to be influential to the reproductive success of marine birds) on nest-site selection by skuas and gulls. Both skuas and Kelp Gulls did not used habitat types in proportion to their availability. Skuas tended to nest in highlands with a north-northwest aspect, and in depressed areas with stable substrata. Kelp Gulls nested exclusively on coastal cliffs and pebble beaches, with no difference in tendency to use either habitat. Skua and gull nest sites were differentiated by elevation, percent of vegetation cover, slope, and microtopography. Grasses (for Kelp Gull), mosses (for skuas), and rockiness were the main variables predicting differential use of the available environment. Factors such as type of nest materials, proximity to foraging areas, social interactions, and presence of other species, among others, probably also affect nest-site selection for both skuas and gulls at Cierva Point, Antarctic Peninsula.

Wetland loss due to land use change in the Lower Paraná River Delta, Argentina

Wetland loss is a global concern because wetlands are highly diverse ecosystems that provide important goods and services, thus threatening both biodiversity and human well-being. The Paraná River Delta is one of the largest and most important wetland ecosystems of South America, undergoing expanding cattle and forestry activities with widespread water control practices. To understand the patterns and drivers of land cover change in the Lower Paraná River Delta, we quantified land cover changes and modeled associated factors. We developed land cover maps using Landsat images from 1999 and 2013 and identified main land cover changes. We quantified the influence of different socioeconomic (distance to roads, population centers and human activity centers), land management (area within polders, cattle density and years since last fire), biophysical variables (landscape unit, elevation, soil productivity, distance to rivers) and variables related to extreme system dynamics (flooding and fires) on freshwater marsh conversion with Boosted Regression Trees. We found that one third of the freshwater marshes of the Lower Delta (163,000ha) were replaced by pastures (70%) and forestry (18%) in only 14years. Ranching practices (represented by cattle density, area within polders and distance to roads) were the most important factors responsible for freshwater marsh conversion to pasture. These rapid and widespread losses of freshwater marshes have potentially large negative consequences for biodiversity and ecosystem services. A strategy for sustainable wetland management will benefit from careful analysis of dominant land uses and related management practices, to develop an urgently needed land use policy for the Lower Delta.

The role of river drainages in shaping the genetic structure of capybara populations

The capybara, Hydrochoerus hydrochaeris, is an herbivorous rodent widely distributed throughout most of South American wetlands that lives closely associated with aquatic environments. In this work, we studied the genetic structure of the capybara throughout part of its geographic range in Argentina using a DNA fragment of the mitochondrial control region. Haplotypes obtained were compared with those available for populations from Paraguay and Venezuela. We found 22 haplotypes in 303 individuals. Hierarchical AMOVAs were performed to evaluate the role of river drainages in shaping the genetic structure of capybara populations at the regional and basin scales. In addition, two landscape genetic models, isolation by distance and isolation by resistance, were used to test whether genetic distance was associated with Euclidean distance (i.e. isolation by distance) or river corridor distance (i.e. isolation by resistance) at the basin scale. At the regional scale, the results of the AMOVA grouping populations by mayor river basins showed significant differences between them. At the basin scale, we also found significant differences between sub-basins in Paraguay, together with a significant correlation between genetic and river corridor distance. For Argentina and Venezuela, results were not significant. These results suggest that in Paraguay, the current genetic structure of capybaras is associated with the lack of dispersion corridors through permanent rivers. In contrast, limited structuring in Argentina and Venezuela is likely the result of periodic flooding facilitating dispersion.

Use of Capybaras in Argentina

Capybaras (Hydrochoerus hydrochaeris) have been used in Argentina since pre-Columbian times as a source of hide, meat, and fat. Hide is the most valuable capybara by-product and, at present, represents the major hunting pressure for this species in the country. Until recently it has been among the most frequently consumed wild terrestrial vertebrates after the coypu (Myocastor coypus) and the tegu lizard (Tupinambisspp.), representing an important live natural resource due to the social and economic impact of its use in all provinces with wild populations of this rodent. In particular, products made from the manufacture of leather goods feature within the “typical regional products”, which are sought by both local buyers and foreign tourists. Furthermore, due to its high abundance in many localities within its distribution range, this species also has an important ecological role in wetlands associated with large river basins in the northeastern region of the country. This chapter deals with the ecological and socioeconomic importance of capybaras in Argentina, providing an overview of the capybara’s status, its historical use, present legislation, and associated trade issues. Finally it analyzes capybara production systems, progress in wild population management, and future needs for administration of this natural resource.

Ground beetles (Coleoptera: Carabidae) inhabiting anthropogenic habitats in the lower delta of the Paraná river, Argentina: geographic distribution and ecological characteristics

The primary aims of this paper were to provide the first inventory of carabid beetles collected in five different anthropogenic habitat types of the Lower Delta of the Paraná River, to describe their main ecological characteristics and to provide information on their distribution range in ecoregions, subregions and ecosystem complexes of Argentina and across the Neotropical region. Species were grouped according to six classes of distributions in relation to their presence in the Delta of the Paraná River. In addition, rarefaction curves were built in order to compare the seasonal species richness. We collected 1486 individuals belonging to 48 species. The southernmost distribution limit of 50% of the species is located south of the Delta region. Moreover, 21% of the species are confined to the Delta and Islands of the Parana and Uruguay Rivers ecoregion and to localities within the neighbouring ecoregions of Espinal and Pampa. Most (63%) of the species were zoophagous and 25% were either omnivorous or seed eaters; 52% were hydrophilous, 44% mesophilous and one was xerophilous. The high number of species found in this ecoregion emphasising its importance as a biodiversity hotspot of South American carabids. Human activities have led to changes in the landscape of the Delta Islands which could favour the establishment of mesophilous and xerophilous species from other ecoregions. Seasonal carabid richness is higher in the warm seasons (spring and summer) compared with the cold seasons (autumn and winter). Although, the highest absolute richness was found in the most anthropised habitat types, secondary forests had exclusive species, showing the importance of preserving the ecological mosaic of the landscape.