Identifying factors that create and maintain a hybrid zone is of great interest to ecology, evolution and, more recently, conservation biology. Here, we investigated the role of environmental features in shaping the spatial dynamics of a hybrid zone between the southern tigrina, Leopardus guttulus, and Geoffroy's cat, L. geoffroyi, testing for exogenous selection as the main force acting on its maintenance. These Neotropical felid species are mainly allopatric, with a restricted area of sympatry in the ecotone between the Atlantic Forest and Pampa biomes. As both biomes have experienced high rates of anthropogenic habitat alteration, we also analysed the influence of habitat conversion on the hybrid zone structure. To do this, we used 13 microsatellite loci to identify potential hybrids and generated ecological niche models for them and their parental species. We compared the influence of variables on parental species and hybrid occurrence and calculated the amount of niche overlap among them. Parental species showed different habitat requirements and predicted co‐occurrence was restricted to the forest‐grassland mosaic of the ecotone. However, hybrids were found beyond this area, mainly in the range of L. geoffroyi. Hybrids demonstrated higher tolerance to habitat alteration than parental types, with a probability of occurrence that was positively related with mosaics of cropland areas and remnants of natural vegetation. These results indicate that exogenous selection alone does not drive the dynamics of the hybrid zone, and that habitat conversion influences its structure, potentially favouring hybrids over parental species.

The maned wolf (Chrysocyon brachyurus) is one of the largest South American canids, and conservation across this charismatic carnivore's large range is presently hampered by a lack of knowledge about possible natural subdivisions which could influence the population's viability. To elucidate the phylogeographic patterns and demographic history of the species, we used 2 mtDNA markers (D-loop and cytochrome b) from 87 individuals collected throughout their range, in Argentina, Bolivia, Brazil, and Uruguay. We found moderate levels of haplotype and nucleotide diversity, and the 14 D-loop haplotypes were closely related. Genetic structure results revealed 4 groups, and when coupled with model inferences from a coalescent analysis, suggested that maned wolves have undergone demographic fluctuations due to changes in climate and habitat during the Pleistocene glaciation period approximately 24000 years before present (YBP). This genetic signature points to an event that occurred within the timing estimated for the start of the contraction of the Cerrado around 50000 YBP. Our results reveal a genetic signature of population size expansion followed by contraction during Pleistocene interglaciations, which had similar impacts on other South American mammals. The 4 groups should for now be considered management units, within which future monitoring efforts should be conducted independently.

ABSTRACT. The pampas deer (Ozotoceros bezoarticus Linnaeus, 1758) was in the recent past one of the most characteristic species in the Uruguayan grasslands. However, today the species is very rare, with small relict populations inhabiting in few ranches. To improve our understanding of pampas deer habitat use in modified ecosystems and propose management guidelines we analyzed the pampas deer feeding ecology at Los Ajos ranch. We performed an annual vegetation survey with the purpose to identify the main components of pampas's deer diet and the spatial overlap with livestock. Vegetation offer was characterized by predominance of monocotyledon plants; in three of the four sample periods. The preference values for the crops were positive for ryegrass in winter (0.24) and spring (0.54), the moments of greatest productivity of this pasture; while the rice crops values were negative all year round. The spatial overlap indexes with sheep show a complete exclusion, whereas with cattle the indexes gave values of 0.95 in spring to 0.14 in summer. The niche amplitude was significantly correlated with the spatial overlap levels with cattle. Pampas deer foraging behaviour is opportunistic, typical of mixed feeders. Conservation efforts should focus on implementation of management guidelines of agriculture and cattle breeding activities.KEYWORDS. Diet, habitat use, mixed feeders, niche overlap, pampas deer. RESUMO. Ecología trófica deOzotoceros bezoarticus: implicaciones para su conservación en Uruguay. El venado de campo (Ozotoceros bezoarticus Linnaeus, 1758) fue en el pasado reciente una especie focal de las pasturas uruguayas. Sin embargo, hoy día es una especie rara, con pequeñas poblaciones aisladas que ocupan establecimientos agropecuarios. En este trabajo se analizan aspectos de la ecología trófica en una población de venado de campo. El objetivo es: comprender la interacción entre esta especie y un ecosistema modificado por la actividad agrícola-ganadera. Se busca así proponer medidas de manejo de la población y del ambiente que ocupa. En este trabajo se identifican los principales componentes de la dieta y el grado de solapamiento espacial con el ganado doméstico, para ello se realizó un muestreo anual de la vegetación, se colectaron fecas de venado de campo y se analizó la distribución espacial de los distintos herbívoros que ocupan el establecimiento agropecuario. La oferta de vegetación se caracterizó, en tres de cuatro períodos de muestreo, por una predominancia de plantas monocotiledóneas. Los valores de preferencia para los cultivos fueron positivos para el ryegrass en invierno (0.24) y primavera (0.54), los momentos de mayor productividad de esta pastura; mientras que el cultivo de arroz mostró valores negativos de preferencia a lo largo de todo el año de estudio. Los índices de solapamiento espacial mostraron una completa exclusión con el ganado ovino, mientras que con el ganado bovino se obtuvieron índices de 0.95 en primavera a 0.14 en el verano. La amplitud de nicho tuvo una correlación significativa con...

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