Search

The south of Patagonia is characterized by its semi-arid weather and numerous small, temporary and permanent shallow ponds. The aquatic crustaceans of these water bodies are characterized by their endemism and species richness. The present study was done in the surroundings of Punta Arenas (53°S, Chile), and included six shallow ponds. Samples for conductivity, total dissolved solids, chlorophyll, and crustacean zooplankton as well as littoral species of crustacea were collected. Our study revealed that Branchinecta gaini Daday, 1910 occurred at low conductivity (0.55 mS/cm), and low total dissolved solids (0.28 g/l) and chlorophyll (2.70 μg/l) concentrations, such compared to sites without fairy shrimp populations, that had significantly high conductivity (3.58 mS/cm), and high total dissolved solids (1.80 mg/l) and chlorophyll (12.80 μg/l) concentrations. The results partially agree with the first descriptions of Patagonian water bodies that indicated the presence of fairy shrimps in low conductivity waters. The observations of the presence of B. gaini and other associated microcrustaceans are similar to descriptions of unpolluted water bodies in Antarctica, and those results would support the observations of the present paper. Other reports on fairy shrimp habitats mentioned a wide range of both salinity and trophic status. Other ecological and biogeographical topics on fairy shrimps are also discussed. [ABSTRACT FROM AUTHOR]

Effective population size (Ne) is a parameter of central importance in evolutionary biology and conservation. Factors such as unequal sex ratios of breeding individuals, periodic fluctuation in population size and variance in reproductive success can affect the Ne in general. At present, South American sea lions, Otaria flavescens, from northern Patagonia, Argentina, belongs to one of the several populations that are recovering from overhunting which occurred in the early 20th century. Here, we present the estimate of Ne for this population that takes into account the effects of their polygynous mating system and variation in population size through time. The resultant overall Ne's were 4171 ± 2450 or 4745 ± 2681 breeding animals depending on the inclusion of peripheral adult males. The estimated Ne's are not critical, because they are close to the average mean minimum viable population for vertebrates (5000 breeding adults). Even though the northern Patagonian population of O. flavescens is increasing its abundance is still far below its historical numbers. The Ne estimated should be considered the minimum range to be maintained, especially in light of bycatch related to fishery interactions along the Patagonian coast. We emphasise the importance of estimating Ne for future management plans of the species within different populations. [ABSTRACT FROM AUTHOR]

The Chilean Patagonian lakes are characterized by their oligotrophy, high endemism, significant predominance of calanoid copepods in comparison to daphnid cladocerans, and low species richness. These characteristics are in marked contrast to the situation in North American lakes. In the present study, published information of chlorophyll concentrations and species richness for Chilean Patagonian lakes was considered. The results denoted direct correlations between chlorophyll concentration and species richness, as well as an inverse correlation between latitude and species richness, whereas a relationship between lake surface and species richness was not observed. The results obtained would indicate that the oligotrophic status of the sites studied is the main cause of low species richness. Our conclusions most probably reveal the existence of different regulator mechanisms in comparison to North American lakes. Ecological and biogeographical topics are discussed. [ABSTRACT FROM AUTHOR]