Environment and life cycles influence distribution patterns of hydromedusae in austral South America

We analysed hydromedusa assemblages of South America (from 22°S to 56°S and from 040°W to 080°W), their association with water masses and the influence of the life cycle on medusa distributions. The geographic distribution of 130 species of hydromedusae was compiled from literature reports (62 publications between 1913 and 2012). Seven areas were defined: Atlantic Magellanic, Argentinean, Pacific intermediate zone, Pacific Magellanic, Peruvian–Chilean, South Brazilian and Oceanic. The variance of the species–environment relationship was explained by depth and temperature. Distribution patterns of Atlantic hydromedusae are associated with neritic water masses, supporting previously proposed biogeographical provinces. Assemblages on the Pacific side of South America are under the influence of the Humboldt Current system, with a break in species distribution around Chiloé Island. Only the oceanic assemblage contained the same species in both the Pacific and Atlantic zones. We found that meroplanktonic medusae contributed more to define the neritic assemblages, while the oceanic assemblage was better defined by holoplanktonic medusae. Therefore, our data suggest that meroplanktonic hydromedusae appeared to be more restricted in distribution than holoplanktonic ones.     

Comparative composition of the snake assemblage from Sierras de Ventania mountain range,east-central Argentina

ABSTRACT

The composition of a snake assemblage from an orographic island in east-central Argentina, the Sierras de Ventania mountain chain, was analyzed. The aim was to determine the biogeographic resemblance to other snake assemblages from neighboring regions. Species composition of each region was obtained from an exhaustive review of the literature, and both fieldwork and museum records. The higher biogeographic resemblance of the Sierras de Ventania occurred with the Sierras de Tandilia and the Coastal Dunes. These regions formed a well-defined group according to their snake assemblages. On the other hand, the Sierras de Lihué Calel linked to the Sierras de Ventania, and also to the rest of the compared regions, at very low values of biogeographic resemblance. The results obtained in this study contrasted with the classic zoogeographic scheme. Snake assemblages allowed recognizing a more significant division between Central and Pampean domains. In this scheme, the limit between these two regions moved to the southwest of the classical scheme; therefore the Sierras de Ventania was part of the Pampean domain. Also, the recognition of the Subtropical domain was evident, as well as its faunistic link with the Pampean domain.     

Functional convergence of fish assemblages in urban streams of Brazil and the United States

The aim of this study was describe functional faunal assemblages occurring in streams with high influence of urbanization in USA and Brazil to answer the question whether similar biological traits of fish assemblages would be found between streams with high influence of urbanization in USA and Brazil. We compiled data on the structure and composition of freshwater fishes in 46 urban streams in the USA and 10 urban streams in Brazil. Data on functional traits was established in accordance with ordinal data on abundance. Cluster analysis was conducted to examine relationships among species composition across all sites sampled and to uncover patterns in functional traits of the fish assemblages by nonmetric multidimensional scaling (NMS). The cluster analysis separated the biogeographic regions in relation to the fish fauna composition. However, the ordination analysis (NMS) did not reveal differences between functional traits in Brazil and USA urban fish assemblages, suggesting functional similarity of very disparate zoogeographic assemblages.     

The relationship between marine fronts and fish diversity in the Patagonian Shelf Large Marine Ecosystem

Aim To evaluate the relationship between marine fronts and (1) fish diversity patterns, (2) fish biomass distribution, and (3) fish assemblage structure. Location Patagonian Shelf, Southwestern Atlantic Ocean. Methods Three main frontal systems and eight nearby zones (frontal vs. non‐frontal areas) were compared. An extensive fishery database, obtained during an a priori sampling scheme (spatial resolution 1 × 1) from 1978 to 1979, was employed. Analyses of 248 trawling stations were performed using a combination of diversity measures (species richness, Shannon diversity and evenness), biomass analyses and multivariate analyses [nonparametric analysis of similarity (ANOSIM), non‐metric multidimensional scaling ordination (NMDS) and similarity percentages (SIMPER)] to evaluate the effect of fronts on fish communities. Results In total, 46 fish taxa were identified. Demersal fish diversity increased at the tidal front of Península Valdés but decreased in the frontal zones of the Southern Shelf‐Break and Magellan frontal systems. The richness and biomass of pelagic fish were higher at the Península Valdés Tidal Front, while the biomass of demersal fish was higher at its non‐frontal counterpart. Fish diversity did not differ consistently along the Northern Shelf‐Break Front. However, a higher fish biomass was registered at the non‐frontal zone. Demersal and pelagic fish assemblages differed between frontal and non‐frontal zones. Main conclusions The Patagonian Shelf Large Marine Ecosystem has diverse frontal types that appear to have different effects on fish diversity and assemblage structure. Seasonal (tidal) or permanent fronts have different effects on the parameters analysed, which could be due to productivity–diversity relationships. The Península Valdés Tidal Front, a relatively short temporal scale system, demonstrates a stronger influence on fish diversity, biomass and assemblage structure than the other frontal areas studied. The seasonality of nutrient input owing to frontogenesis, which begins during the austral spring, may play an important role in determining local diversity. At permanent frontal features, diversity decreases when the nutrient availability is high. This is potentially because, when food resources increase, a few species become dominant.     

A regional biogeography of shore molluscs: influence of the Kuroshio current and the two capes

The regional pattern of shore molluscan assemblages was investigated along a 650-km coastline of the Kii Peninsula in central Japan. Hydrography of the coastal waters differed between three subareas, the Inner Kii Channel (IKC), the Outer Kii Channel (OKC), and the Sea of Kumano (SOK), which are demarcated by the two prominent capes, Cape Hinomisaki and Cape Shionomisaki. The water of OKC was warm, saline, and transparent compared to that of the other subareas, due to the influence of the intruding Kuroshio current. Corresponding to this hydrographic difference, the composition of shore malacofauna differed between OKC and the other subareas. Species diversity and relative abundance of the southern species (< 35° N) increased southward and were higher in the OKC than in the other subareas. Multivariate analysis on various environmental and biotic parameters detected significant relationships between the temperature and geographic groups of species, and between substratum geology and trophic groups. The present and previous results elucidated the following biogeographic process in the study area. The Kuroshio washes the coast of the OKC, and enriches the southern species by increasing the temperature and providing their larvae; thus the diversified warm-water malacofauna of the OKC intervenes between the colderwater malacofaunas of the IKC and SOK. This major pattern is further modified by shore geology and the degree of wave exposure at local scales. The present survey method, a semi-quantitative timed search for intertidal assemblages required less time than, and yet yielded results similar to, the widely used dispersed quadrat survey for the parameters selected in the present analysis.     

Explaining the causes of the zoogeographic transition around the Isthmus of Kra: using bats as a case study

Aim  The causes of a zoogeographic divide in peninsular Thailand around the Isthmus of Kra have not been adequately resolved. We explored climatic, historical and geological perspectives to gain insights into factors that may have contributed to the development and maintenance of this zoogeographic transition, and to determine whether a faunal transition occurs for bats. Location  Southeast Asia, focusing on the Thai Peninsula. Methods  Spatial principal components analysis was used to determine the relationship between climate and species distribution patterns. We studied bats (order Chiroptera) because of their ability to bypass small‐scale geophysical barriers. Spatial data on bat species distributions on the Thai Peninsula were analysed in relation to multivariate measures of climate to determine the possible influence of climatic zonation on distribution patterns. We assessed the effects of the interaction of climatic zonation with the highly dynamic environmental conditions the area has undergone in relation to species distribution patterns. Results  A zoogeographic transition was found, with 44 species (out of 127) restricted to the north of the Isthmus of Kra and 29 restricted to the south, although there were relatively few abrupt changes in distribution at the exact position of the isthmus. Northern and southern species were associated with specific climatic conditions. Major transitions in the distribution of bat species exist at 6–6.5° N and 13–13.5° N, with a smaller peak at 11.0° N. These major peaks fall in the same areas as the borders of climatic zones, and the 6–6.5° N peak falls in the same area as a floristic divide (the Kangar–Pattani Line). Main conclusions  On the mainland, climatic zones cause gradual changes in species distributions. However, in addition to climatic factors, repeated changes in the breadth of the Sunda Shelf during recent glacial cycles may have caused locally high extinction rates at narrow points on the peninsula, exacerbating transitions in species distribution patterns along the region, in the context of a peninsula effect that reduces opportunities for recolonization.     

Structure of ground-dwelling arthropod assemblages in vegetation units of Área Natural Protegida Península Valdés,Patagonia, Argentina

Knowing the spatial variation of insect and arachnid assemblages and their relationship with habitat variables is critical to understand the structure and dynamics of these communities in arid environments. The aim of this paper was to analyze the variation in ground-dwelling arthropod assemblages across three representative vegetation units of the Área Natural Protegida Península Valdés (Patagonia, Argentina). We asked whether environmental differences among representative vegetation units were associated to distinct arthropod assemblages. We selected three plant communities: grass, dwarf-shrub, and shrub steppes, and established three sampling sites within each of them. We measured variables of vegetation structure and soil characteristics and collected the arthropods using 10 pitfall traps per site. We analyzed the structure of arthropod assemblages at both family and ant species taxonomic levels. Each plant community displayed a distinctive assemblage, with differences in diversity, taxa abundance, trophic structure and functional groups of ants. Vegetation variables explained a higher proportion of the variation in the structure of the ground-dwelling arthropod assemblages than the soil variables. This work highlights the importance of the different vegetation units for the conservation of ground-dwelling arthropod biodiversity in Península Valdés.     

Evidence of biogeography in surface ocean bacterioplankton assemblages

Regardless of the importance of bacterial assemblages as essential components of ecosystems, little is known about how their populations are structured. We analyzed the composition and turnover rates, based on 16S rDNA sequences, of surface water oceanic bacterial assemblages of the fraction between 0.1 and 0.8 μm along a latitudinal gradient (45°6′42′′N in the North Atlantic to 15°8′37′′S in the South Pacific) including geographic distance, temperature, chlorophyll a and salinity. Here we show that oceanic bacterial assemblages between 0.1 and 0.8 μm, can be structured by a variety of environmental interactions that include separation by distance and chlorophyll a concentration in temperate North Atlantic coastal samples and temperature in tropical Atlantic and Pacific coastal and open ocean samples. Bacterial phyla composition diverged between temperate and tropical regions. This study suggests that some bacterial assemblages could be structured both by environmental and spatial factors, while others by environmental factors alone.     

SUMMER DISTRIBUTION OF PELAGIC BIRDS OFF THE COAST OF ARGENTINA

Eighteen species of sea–birds were observed from CSS 'Hudson' in the South Atlantic between the Rio de la Plata and Tierra del Fuego in late January and late February 1970. Major feeding areas were noted off Mar del Plata, the Valdes Peninsula and Tierra del Fuego, Argentina, the first two in rich modified or unmodified water of the subantarctic Falkland Current, associated with upwelling. The southernmost area had most birds, the northernmost fewest. A temperate–latitude assemblage including Yellow–nosed Albatross and Cory's Shearwater occurred off Mar del Plata in warmed water of subantarctic (Falkland Current) origin. South of 39°S these two species were replaced by Black–browed Albatross and Great Shearwater in cold offshore water of the Falkland Current. Off the Valdes Peninsula Black–browed Albatross, Great and Sooty Shearwaters, White–chinned Petrels and family groups of Magellanic Penguins occurred near the edge of highly–productive water of the Falkland Current. The largest feeding area, east of Tierra del Fuego, had Magellanic and Rockhopper Penguins, Great Shearwaters, King Cormorants, South American Terns and jaegers, but no oceanographic information is available. At 50°S prions and diving petrels appeared for the first time, marking a possible oceanographic discontinuity or proximity to colonies on the Falkland Islands. Several common species of the South Atlantic were not seen on the transect including Cape Pigeon, Southern Fulmar, Soft–plumaged Petrel, Schlegel's Petrel and Pediunker. Kelp Gull, South American Tern, Manx Shearwater and jaegers were rare or absent far from land. New southern limits for the western South Atlantic Ocean were established for Cory's and Manx Shearwaters, and the Great Shearwater was observed for the first time in Chilean waters.     

The influence of abrupt climate change on the ice‐age vegetation of the Central American lowlands

Aim To investigate the effects of abrupt climate change in the North Atlantic on the vegetation history of lowland Central America. We use palynological evidence from a Central American lake on the Yucatan Peninsula to evaluate the effects of rapid climate changes during the last ice age, between 65 and 8 ka. Location Lake Petén‐Itzá, lowlands of northern Guatemala. Methods Sediment core PI‐6 was sampled at c. 170‐year resolution for pollen and charcoal analysis in order to construct a temporal sequence of environmental change. Uni‐ and multivariate statistical analyses were performed on the pollen dataset to test whether there was an association between Heinrich events in the North Atlantic and vegetation changes in the Central American lowlands. Results Pollen analysis revealed that the composition of plant assemblages on the Yucatan Peninsula varied in phase with rapid changes in North Atlantic climate. Pine savannas were the main vegetation type between c. 60 and 47 ka. These savannas gave way to pine–oak (Pinus–Quercus) forests in the latter half of the last ice age. Marked episodes of replacement of the pine–oak assemblage by xeric‐tolerant taxa occurred during Heinrich events. The Last Glacial Maximum (LGM) was characterized by mesic conditions. Main conclusions The pollen record from Lake Petén‐Itzá showed that vegetation changes associated with Heinrich events were more significant than those associated with the LGM. Each Heinrich event produced a characteristic shift towards xeric taxa. Although colder than Heinrich events, the LGM on the Yucatan Peninsula was relatively moist, and the presumed savannization of the landscape during the maximum cooling of the last glacial was not supported by our data. Our findings suggest alternative scenarios for plant diversification and genetic interchange during glacial times, and also indicate that vegetation in tropical continental settings was not as stable as previously thought.     

Allometric differences on the shell shape of two scorched mussel species along the Atlantic South American Coast

Scorched mussels (Bivalvia: Mytilidae) are an important component of rocky shore assemblages around the world. The mussel beds of the mid-intertidal coasts of the south-western Atlantic are composed of two species of scorched mussels, which dominate the physiognomy and structure of the rocky shore communities. The present study investigates the variation in the shell-shape allometric trajectories of both species of mussels throughout their distributional range in the southwestern Atlantic coast, from latitude 34°S to 53°S. Shells of Brachidontes rodriguezii were collected at two Uruguayan localities and four Argentinean localities, while shells of Perumytilus purpuratus were collected at six Argentinean localities. Shell shapes of the specimens were studied by geometric morphometrics using landmark and semi-landmark methods. Different evolutionary histories and thermal regimes characterize these two species. Brachidontes rodriguezii seems to have a long history in the region and is present in a restricted area, the warm temperate region of the south-western Atlantic, while P. purpuratus seems to have a recent history and is present in a wide thermal range, involving the cold-temperate regions of the south-western Atlantic and south-eastern Pacific and the warm-temperate region of the south-eastern Pacific. Based on these considerations, we prompt the hypothesis that allometric trajectories of P. purpuratus shell shape is more variable and adapted to a specific habitat than B. rodriguezii. The impact of allometry was larger in P. purpuratus than in B. rodriguezii. Graphical evidence was gathered, showing that these two species differ in allometric growth forms and that the allometric shell morphology changes reflect environmental constraints and adaptation. While the intertidal mussel beds of the South American coasts are ecologically similar in appearance, we found that the allometric variation of the scorched mussels occurs in response to diverging evolutionary processes such as phenotypic plasticity in P. purpuratus and canalization in B. rodriguezii.     

Role of atelomixis in replacement of phytoplankton assemblages in Dom Helvécio Lake, South-East Brazil

Scale and frequency of changes in a lake’s physical structure, light dynamics, and availability of nutrients are closely related to phytoplankton ecology. Since phytoplankton assemblages were first described, phytoplankton ecologists concluded that these assemblages provide insight into phytoplankton responses to environmental changes. Objectives of this study were to investigate ecology of phytoplankton during a complete hydrological cycle in the deepest natural lake in Brazil, Dom Helvécio, and to sort species into the list of assemblages, checking its accordance with environmental changes in a tropical system within the middle Rio Doce Lake district, South-East Brazil. Canonical Correspondence Analysis, t-test, Mann–Whitney U-test, and Kruskal–Wallis test were used to analyze climatological, environmental, and plankton data, which were obtained monthly in 2002. A new phytoplankton assemblage, N_A (atelomixis-dependent desmids), is suggested because atelomixis (robust movement of water occurring once a day) contributed to replacement of species in Dom Helvécio Lake. Stability of stratification, water chemistry, and composition of phytoplankton assemblages characterized two periods. The first period occurred in six rainy months (Jan–Mar and Oct–Dec) when the lake was stratified and phytoplankton was dominated by two assemblages: N_A and F. The second period occurred in six dry months (Apr–Sep) when the lake was nonstratified and phytoplankton was dominated by four assemblages: S2, X1, A, and L_O. Results suggest that phytoplankton in Dom Helvécio Lake was shaped by seasonal and daily changes of water temperature, even with its lower amplitude of variation within 2002 (El Niño year). These changes promoted water column stratification or mixing, reduced light, and increased nutrient availability. Temperature, therefore, is similarly important to phytoplankton ecology in tropical regions as it is in temperate ones. Sorting phytoplankton species into assemblages matched well with environmental changes and periods identified so it is also suggested that this can be further used as an appropriate tool to manage water quality when evaluating tropical lakes.     

Atlantic paleobathymetry, paleoproductivity and paleocirculation in the late Albian: the benthic foraminiferal record

Spatial distribution patterns of benthic foraminifers in upper Albian sediments from 25 DSDP/ODP sites and 31 onshore sections of the North and South Atlantic Ocean are used to generate paleobathymetric reconstructions and to identify areas of high primary production such as coastal and equatorial upwelling zones. New paleobathymetric estimates are provided for DSDP/ODP sites and onshore locations that are not situated on oceanic crust. Paleobathymetric reconstructions indicate shallow water exchange between the North and South Atlantic but show the existence of a deep-water connection between the western and eastern Tethys (>2500 m) through the Gibraltar Gateway. Strikingly, there is no evidence for a strong latitudinal gradient in deep-water benthic foraminiferal distribution during the late Albian: South Atlantic assemblages show close affinity to North Atlantic and Tethyan assemblages, exhibiting only a minor degree of provincialism. Biogeographic patterns reveal a distinct asymmetry in late Albian paleoproductivity for the North Atlantic. As for the present day, the eastern margins of the Atlantic were generally more productive than the western margins, and a belt of enhanced carbon flux export to the seafloor can be traced around the north African coast, which probably corresponded to a zone of vigorous coastal upwelling. By contrast, assemblage composition in the South Atlantic generally reflects mesotrophic to oligotrophic conditions. Benthic foraminiferal distribution patterns, thus, provide robust proxy data to test predictions from paleocirculation and paleobathymetric models for the mid-Cretaceous Atlantic Ocean and adjacent margins.     

Distribution patterns of freshwater molluscs along environmental gradients in the southern Guadiana River basin (SW Iberian Peninsula)

The taxonomic status of the freshwater mollusc fauna of the Iberian Peninsula it is reasonably well known, but, unlike other benthic macroinvertebrate, its distribution and ecology has been poorly studied. In this article, I study the relationships between environmental characteristics and distribution and community structure of freshwater molluscs along climatic, hydrological, physicochemical, and heterogeneity gradients in the southwestern Iberian Peninsula. Ninety-four sampling points were analysed, in which, in addition to habitat features, the presence/absence and abundance of species were evaluated. The environmental gradients were measured by use of principal-components analysis (PAC), which orders the variables along two gradients: headwaters-mouth gradient (PC1) and water availability (PC2). According to canonical correspondence analysis (CCA), the main environmental factors related to species distribution and community structure were conductivity, permanency, channel width, turbidity, slope, and distance to the main river axis. The relationship between biodiversity (measured as species richness and the Shannon–Weiner diversity index), the ratio of the number of introduced species to the total number of species (zoogeographic integrity coefficient), and environmental variables was best explained by a regression model incorporating, basically, the permanence of water in streams as the variable that accounted for most of the variance. This study demonstrates that the distribution of freshwater molluscs along a Mediterranean gradient highly stressed by drought depends, mainly, on the hydrological stability and environmental conditions of the headwaters and estuarine sites.     

New records and range extension of the Portuguese dogfish Centroscymnus coelolepis in the south-western Atlantic Ocean,with comments on its morphology

The Portuguese dogfish Centroscymnus coelolepis is a wide-ranging deep-water shark and a common by-catch component of the catches of several mid- to deep-water fisheries. In the present study, two new records from the south-western Atlantic Ocean are reported based on specimens caught by bottom-longline fishing vessels operating in the Argentinean–Uruguayan Common Fishing Zone. Species identification based on morphology and detailed morphometrics, as well as molecular data are presented for one of the specimens. The distribution of the species over the south-western Atlantic is discussed on the basis of the available bibliography and a thorough revision of museum collections. The records presented here expand the species' previously acknowledged distribution southwards, from around 21° S to at least 38° S, suggesting it occurs continuously along the shelf break of eastern South America. However, given the limited access to specimens of deep-water sharks in the region, the abundance and real extent of C. coelolepis distribution in the south-western Atlantic as well as its interaction with deep-water fisheries remain to be fully assessed.     

Recent changes in the distribution of a marine gastropod,Patella rustica Linnaeus, 1758, and their relationship to unusual climatic events

Aim Recent colonization of northern Portuguese shores by Patella rustica Linnaeus, 1758, led to the bridging of a historical gap in the distribution known since the 1900s. Long‐term oceanographic data collected over the last half‐century were examined in order to detect possible mechanisms for the observed change in its distribution. Location This study was carried out along the entire Portuguese coastline, from 41°50′ to 37°06′ N. Time‐series of hydrographical variables (sea surface temperature and salinity) were derived for the Atlantic coast of the Iberian Peninsula. Methods Abundance and size‐frequency distributions of the newly observed limpet populations were compared with those from well‐established populations in southern Portugal. Anomalies were computed for sea surface temperature (1950–2000) and sea surface salinity (1958–2001) data, covering the whole Atlantic coast of the Iberian Peninsula. An upwelling index (1967–2005) was derived for a single location within the distributional gap of P. rustica. Split moving window analysis was performed to detect significant discontinuities in hydrographical data sets. Results Patella rustica has gradually been expanding in northern Iberia, and in the late 1990s the historical gap in distribution in northern Portugal was bridged. Size‐frequency distribution differed between historical and recent populations, the latter lacking small‐sized individuals. At the same time, several anomalous oceanographic events occurred off the Portuguese coast and were probably related to this expansion. Main conclusions Although sea surface temperature might be a major determinant of the reproductive success of P. rustica and hence its dispersal potential, it is more likely that a coincidence of several factors occurring in the late 1990s provided exceptional conditions that allowed the geographical expansion of this species.     

A Matter of Scale: Historical and Environmental Factors Structure Anuran Assemblages from the Upper Madeira River,Amazonia

Biogeographical history and current ecological interactions have usually been addressed separately to explain the spatial distribution of patterns of biodiversity. In this study, we evaluated the integrated effects of biogeographical and environmental factors in structuring the diurnal amphibian anuran assemblages of the upper Madeira River, southwestern Amazonia. We used a sampling design involving 98 standardized units, distributed across seven locations covering both banks of the river's course in the state of Rondônia, Brazil. We conducted searches for frogs in three campaigns between February 2010 and February 2011, aiming to: (1) evaluate the effect of the Madeira River as a biogeographic barrier at the species‐assemblage level, and (2) test the influence of seven environmental variables (vegetation structure, vegetation cover, soil nutrients, soil structure, slope, elevation, and distance from the river bank) on the spatial structure of the frog assemblages, separately on each riverbank. Thirteen species of diurnal frogs were recorded, six of which were restricted to one of the river margins. Multivariate analysis of variance indicated a significant effect of the river as a barrier. Multiple regression analyses suggested that the environmental variables structuring frog assemblages differ on either side of the river. We found that both historical elements (on a regional scale) and environmental factors (at a local scale) shaped the occurrence and distribution of frog species in the study area.     

Southernmost records of bottlenose dolphins, Tursiops truncatus

Bottlenose dolphins (Tursiops spp.) are cosmopolitan animals widely distributed in waters of both hemispheres. The taxonomy of Tursiops has long been controversial, with over 20 specific names being published, and subspecies and inshore/offshore forms being proposed. In the southwestern South Atlantic, subspecies T. truncatus truncatus and T. truncatus gephyreus were proposed for specimens along the coasts of Brazil, Uruguay, and Argentina. Sightings of bottlenose dolphins are common along the coast of Argentina as far south as the Province of Chubut (ca. 46°S). Here, we summarize and discuss the southernmost records of bottlenose dolphins. We cannot make inferences about the species or subspecies to which these animals belong given the small number of specimens. Future studies of external measurements, pigmentation, DNA, and isotopes from both sides of the continent should help clarify the situation off southern South America. Furthermore, research is needed to explore a possible link between an effect of general global warming and the Tursiops specimens found this far south. The sighting and specimens described here, at 53°S–nearly 55°S, are the southernmost records for the genus and extend the range of the species in the southern South Atlantic.