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Sensitivity to water availability is a key physiological trait for grassland species located in arid and semiarid environments, where successful germination is closely related to rainfall dynamics. Festuca pallescens inhabits diverse environments along a steep precipitation gradient in North Patagonia, thus offering a suitable model for the study of germination behavior in response to water availability. By analyzing germination in nine populations using a hydrotime model approach, we aimed to find within-species variation. Seed population behavior was analyzed under different hydric conditions using hydrotime model parameters (hydrotime, mean base water potential and its standard deviation). We estimated the mean base water potential for F. pallescens (ψb(50) = − 2.79 ± 0.45 MPa), which did not differ significantly between populations. However, the hydrotime parameter (θH) varied markedly, suggesting physiological adaptation to local environments. Higher values of θH were found in populations located at the extremes of the distribution gradient, indicating that germination may be prevented or delayed in conditions that are suboptimal for the species. Since the variation in hydrotime model parameters did not follow a cline, micro-environmental cues may have the greatest influence on the physiological behavior of the species, rather than the macroscale rainfall gradient.

Studies of genetic differentiation in fragmented environments help us to identify those landscape features that most affect gene flow and dispersal patterns. Particularly, the assessment of the relative significance of intrinsic biological and environmental factors affecting the genetic structure of populations becomes crucial. In this work, we assess the current dispersal patterns and population structure of Ctenomys "chasiquensis", a vulnerable and endemic subterranean rodent distributed on a small area in Central Argentina, using 9 polymorphic microsatellite loci. We use landscape genetics approaches to assess the relationship between genetic connectivity among populations and environmental attributes. Our analyses show that populations of C. "chasiquensis" are moderately to highly structured at a regional level. This pattern is most likely the outcome of substantial gene flow on the more homogeneous sand dune habitat of the Northwest of its distributional range, in conjunction with an important degree of isolation of eastern and southwestern populations, where the optimal habitat is surrounded by a highly fragmented landscape. Landscape genetics analysis suggests that habitat quality and longitude were the environmental factors most strongly associated with genetic differentiation/uniqueness of populations. In conclusion, our results indicate an important genetic structure in this species, even at a small spatial scale, suggesting that contemporary habitat fragmentation increases population differentiation.

ABSTRACT. Geographic patterns of variation in life-history traits have puzzled researchers for decades. However, the widely accepted idea that mating systems exhibit a tropical-temperate latitudinal trend, with extra-pair mating systems being the norm among temperate species and genetic monogamy the norm among tropical species, is supported by sparse data, particularly for birds breeding in the tropics and even more so for birds that breed in the southern hemisphere temperate zone. Our objective was to examine the genetic mating system of Chilean Swallows (Tachycineta meyeni) breeding at 54°S in Tierra del Fuego, Argentina. From 2006 to 2009, we examined the paternity of young in 52 broods. Contrary to predictions based on their congeners that breed at equivalent latitudes in the northern hemisphere, Chilean Swallows in our study had low rates of extra-pair paternity (EPP), with 13.5% of nests (N = 52) having at least one extra-pair young and 6.8% of all nestlings (N = 161) fathered by extra-pair males. These rates are also lower than those reported for species of Tachycineta swallows that breed at tropical latitudes. We found no support for a tropical-south temperate latitudinal cline in EPP rates. The highly unpredictable weather of the island of Tierra del Fuego might be influencing parental investment at this site; small clutch sizes and low EPP rates are expected if biparental attention is crucial for chick survival and reproductive success for these aerial insectivores. We argue that the sparse sampling of mating systems in birds worldwide may have contributed to a misapprehension of a global pattern. More studies of tropical and south-temperate systems are needed to build on theories based on a wider set of taxa. RESUMEN. Paternidad extra-pareja en una población de Golondrina Patagónica a los 54 grados surLos patrones de variación geográficos en rasgos de historias de vida han intrigado a los investigadores por décadas. Sin embargo, la idea ampliamente aceptada que establece que los sistemas de apareamiento presentan una tendencia latitudinal del trópico a las latitudes templadas, con sistemas de apareamiento extra-pareja siendo la norma en las especies templadas, y la monogamia genética la norma entre especies tropicales, se apoya en muy pocos datos; en especial para especies de aves que se reproducen en el trópico, y más aun para aquellas de la zona templada del hemisferio sur. Nuestro objetivo fue estudiar el sistema genético de apareamiento de la golondrina Patagónica Tachycineta meyeni a los 54°S en Tierra del Fuego, Argentina. Entre 2006-2009 examinamos la paternidad de los polluelos de 52 nidadas. Contrario a nuestras predicciones basadas en los congéneres que se reproducen en latitudes equivalentes del hemisferio norte, en nuestro estudio las golondrinas Patagónicas tienen tasas muy bajas de paternidad extra-pareja con 13.5% de nidos con por lo menos un polluelo extra-pareja (N = 52) y 6.8% de polluelos extra-pareja en la población (N = 161). Estas tasas son más bajas que las encontradas en especie...

In Patagonia, arid and semiarid lands are being affected both by inappropriate management practices, which are leading to degradation, and by volcanic activity, whose effects are still unclear. This study aimed to test whether superficial deposition of volcanic tephra could benefit two of the most prominent Patagonian forage grass species (Poa ligularis and Pappostipa speciosa var. speciosa). Pots with P. ligularis and P. speciosa were kept under wet (W) and dry (D) conditions in the presence (Tþ) or absence (TÀ ) of tephra for 105 days, and then were all well-watered. We determined the effects of tephra on soil water retention and conservation, soil moisture content (% v/v), plant growth, stomatal conductance (gs), and gs recovery capacity. The water regime significantly affected both species performance and gs. The presence of tephra increased soil water conservation, soil moisture content in wet conditions, and P. ligularis gs in wet conditions, and decreased senescence in dry conditions (9% in P. ligularis and 16% in P. speciosa). The presence of tephra allowed roots to grow in 8/10 and 2/10 pots in W conditions for P. ligularis and P. speciosa, respectively, and in only 1/10 pots in D conditions, only for P. ligularis. Tephra was also associated with gs recovery after dry conditions. Poa ligularis was more positively affected by tephra than P. speciosa, probably because P. ligularis has higher phenotypic plasticity. The positive effects of tephra may increase the resilience and resistance of P. speciosa and P. ligularis to periods of water shortage.

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