Southern Tierra Del Fuego Research Articles

Chinook salmon (Oncorhynchus tshawytscha, Walbaum 1792) in the Beagle Channel, Tierra del Fuego: the onset of an invasion

In this paper we provide the first report of the presence of exotic Chinook salmon (Oncorhynchus tshawytscha) in two rivers off the Beagle Channel, Lapataia and Ovando, in southern Tierra del Fuego. We also confirm that successful reproduction occurred in the fall of 2007, as we captured yearlings in freshwater. Scale pattern analyses of adult fish caught were all of the “stream” ecotype, with ages ranging between 3 and 5 (average 4.2 year). Stable isotope analysis of Ovando-Lapataia Chinook population indicates general patterns consistent with those of other populations in the region, but characteristically enriched levels of C indicates a distinct ocean feeding location as compared to Atlantic populations in the Santa Cruz River. Two different haplotypes, one identical to the unique haplotype of the Caterina River population, were found in the Ovando-Lapataia rivers, providing partial evidence for some level of contemporary segregation between these two populations. As an exotic species, Chinook salmon have been able to use the ocean as a waterway to rapidly colonize new habitats both in New Zealand and in several Pacific and Atlantic river basins of continental Patagonia. This record expands the known distribution of this species in Patagonia further south and into the Island of Tierra del Fuego. Its presence in the Beagle Channel creates the conditions for its expansion to a significant collection of new rivers, as well as to adjacent marine areas in and around the Southern Fuegian Channels. Our results provide support to the idea that, in practice, no district of Patagonia is sheltered from the colonization by invasive anadromous Salmonids.

Mass balance evolution of Martial Este Glacier, Tierra del Fuego (Argentina) for the period 1960–2099

Abstract. The Martial Este Glacier in southern Tierra del Fuego was studied in order to estimate the surface mass balance from 1960 until 2099. For this reason a degree-day model was calibrated. Air temperature and precipitation data obtained from 3 weather stations as well as glaciological measurements were applied. The model was driven using a vertical air temperature gradient of 0.69 K/100 m, a degree-day factor for snow of 4.7 mm w.e. K−1 day−1, a degree-day factor for ice of 9.4 mm w.e. K−1 day−1 and a precipitation gradient of 22%/100 m. For the purpose of surface mass balance reconstruction for the time period 1960 until 2006 a winter vertical air temperature gradient of 0.57 K/100 m and a summer vertical air temperature gradient of 0.71 K/100 m were added as well as a digital terrain model. The key finding is an almost continuous negative mass balance of −772 mm w.e. a−1 throughout this period. While the calculation of the mass balance for the period 1960–2006 is based on instrumental records, the mass balance for the years 2007 until 2099 was estimated based on the IPCC SRES A2-scenario. To accomplish this estimation, the dataset of the global climate model HadCM3 was statistically downscaled to fit local conditions at Martial Este Glacier. Subsequently, the downscaled air temperature and precipitation were applied to a volume-area scaling glacier change model. Findings reveal an enduring deglaciation resulting in a surface area reduction of nearly 93% until 2099. This implicates that the Martial Este Glacier might be melted off at the beginning of the 22nd century.

Middle–Late Holocene palynology and marine mollusks from Archipiélago Cormoranes area, Beagle Channel, southern Tierra del Fuego, Argentina

The palynology and marine mollusks of a marine sequence from Río Ovando (54° 51′ S, 68° 35′ W), Archipiélago Cormoranes, Beagle Channel, has been studied in order to reconstruct paleoenvironmental conditions during the Middle–Late Holocene. The dinoflagellate cyst assemblages from Río Ovando sequence reflect fjord (estuarine) environments close to terrestrial ice field, affected by glacier meltwater discharge, and characterized by short-term oscillations of sea-surface water parameters. The base of the section, which is dated at about ca. 4160 14C yr B.P. (4736 cal yr B.P.) (Palynological Subzone RO-2c), is characterized by a high species diversity of dinocyst and mollusks, and it is immediately followed by an interval (Palynological Subzone RO-2b) characterized by the presence of the Echinidinium– Islandinium complex and the monospecific Mytilus mollusk assemblage. This subzone registers an inverse correlation between Nothofagus dombeyi type and Echinidinium– Islandinium complex concentration values during ca. 4160 14C yr B.P. (4736 cal yr B.P.)–4064 14C yr B.P. (4540 cal yr B.P.), suggesting a variable climatic condition, probably related to Neoglacial episodes occurred in the southern Patagonia Andes during this interval. The pollen assemblages permit direct correlations with the onshore palynostratigraphy from southern of Tierra del Fuego. The high percentages of Nothofagus dombeyi type recorded throughout most of the profile strongly suggest the presence of a closed forest, confirming the existence of a variable, cool and wet climate for the Archipiélago Cormoranes area during the Middle–Late Holocene.

Vegetation patterns., plant distribution and life forms across the alpine zone in southern Tierra del Fuego., Argentina

The alpine zone is examined at meso- and microscales in southern Tierra del Fuego (54°49′S), where the full zone is expressed. Mesoscale patterns were studied on opposing aspects, and microscale patterns were studied on a series of solifluction terraces, in a hanging valley overlooking the Beagle Channel. Plant cover and life form data were collected within 50-m altitudinal bands on north and south aspects and comprehensive plant lists were compiled for each band. Topography and associated surface cover were recorded on the terraces. Six alpine plant communities, in lower and upper floristic zones, were differentiated with multivariate analyses and significantly related to five ecological factors. Equivalent communities were separated by approximately 185 m altitude on opposing aspects, which related to a soil temperature difference of approximately 3.0°C. The richness (and range) of 80 local vascular taxa (18.6% of the regional flora), decreased with increasing altitude (6.6 per 100 m); however, richness differed significantly with aspect (north: 5.6, south: 7.5). Upper altitudinal limits (approximately 1250 m a.s.l.), were associated with a midsummer isotherm of approximately 1.7°C. Chamaephytes and hemicryptophytes dominated throughout but the tall tussock form was conspicuously absent. Reasons for this are discussed in the context of the Nothofagus treeline, which conformed to a midsummer isotherm of only approximately 6.0°C. Such patterns are at variance with those found in the oceanic subantarctic islands, other oceanic perhumid temperate mountain regions and tropical high mountains. However, the microscale pattern of fines, pebbles, stones and rock across the active solifluction terraces, with dense vegetation on their steep risers, had a clear affinity with that of other subantarctic regions. Inferences that alpine systems of the Southern Hemisphere are necessarily equivalent to those at similar northern latitudes are cautioned against. Likewise, such comparisons within the Southern Hemisphere may also be invalid.

Paleoecology and paleobiogeographic patterns of mid-Holocene mollusks from the Beagle Channel (southern Tierra del Fuego, Argentina).

As the Beagle Channel lies between the Atlantic and the Pacific oceans, this is a critical region for the interpretation of faunal distributions in the Magellan Region. This work proposes a paleoenvironmental interpretation of the Holocene, inferred from malacological data. The development of different local benthic paleocommunities during the mid-Holocene is associated with the diversity of habitats inside this channel. The analysis of records of Venus antigua and Ensis macha through time and their geographic links to ecological factors showed that these taxa are typical elements of the cold-temperate seas throughout the Magellan Region, showing a similar range of distribution and paleodistribution. The presence of these taxa in life position (AMS 14C of 6,276±41 years BP) suggests that during the mid-Holocene the Beagle Channel was a path for dispersion of these taxa between the two oceans. Whether Venus antigua andEnsis macha are Pleistocene survivors or Holocene migrants is herein discussed. In the future, integrated cross-disciplinary studies will be necessary for a better understanding of the biogeographic relationships among magellanic mollusks.

Paleoecology and paleobiogeographic patterns of mid-Holocene mollusks from the Beagle Channel (southern Tierra del Fuego, Argentina)

As the Beagle Channel lies between the Atlantic and the Pacific oceans, this is a critical region for the interpretation of faunal distributions in the Magellan Region. This work proposes a paleoenvironmental interpretation of the Holocene, inferred from malacological data. The development of different local benthic paleocommunities during the mid-Holocene is associated with the diversity of habitats inside this channel. The analysis of records of Venus antigua and Ensis macha through time and their geographic links to ecological factors showed that these taxa are typical elements of the cold-temperate seas throughout the Magellan Region, showing a similar range of distribution and paleodistribution. The presence of these taxa in life position (AMS 14C of 6,276±41 years BP) suggests that during the mid-Holocene the Beagle Channel was a path for dispersion of these taxa between the two oceans. Whether Venus antigua andEnsis macha are Pleistocene survivors or Holocene migrants is herein discussed. In the future, integrated cross-disciplinary studies will be necessary for a better understanding of the biogeographic relationships among magellanic mollusks.

Geomorphic effects of large wood jams on a sub‐antarctic mountain stream

AbstractDead wood pieces, especially when organized in jams, play an important geomorphic role in streams because of the effects on flow hydraulics, pool formation and sediments storage. The increase in stream morphological diversity and complexity also exerts an important ecological role. This work reports on geomorphic role of large wood (LW) pieces and jams in a third‐order mountain stream located in the Southern Tierra del Fuego (Argentina), and draining an old‐growth Nothofagus‐forested basin not influenced by the beavers damming activity. Even if the in‐stream number of wood pieces (length >1 m; diameter >0.1 m) is comparable to that observed in other climatic areas, the slow growth of the Nothofagus forest causes a lower wood abundance in terms of volumetric load. Because of the relatively small dimensions of the surveyed LW pieces, almost 70% of them demonstrated to have been fluvial transported and also the wood jams reflect the apparent dynamic nature of wood in the channel. Wood jams exert a significant influence on the channel morphology, representing almost half of the drop caused by steps and being responsible for the creation of 30% of the pools. LW‐forced pool volume is strongly and positively correlated to the height of the LW jam. The geomorphic influence of LW jams is also exerted by a considerable sediment storing capacity. Copyright © 2008 John Wiley & Sons, Ltd.

Acumulaciones de detritos leñosos en un cauce de montaña de Tierra del Fuego: análisis de la movilidad y de los efectos hidromorfológicos

SUMMARY This work reports on the geomorphic role of large wood pieces and jams in a third order mountain stream located in Southern Tierra del Fuego (Argentina), and draining an old-growth nothofagus forested basin not influenced by beaver damming activity. Even if the in-stream number of wood pieces (2,300) is comparable to that observed in other climatic areas, the slow growth of the nothofagus forest causes a lower wood abundance in terms of volumetric load (121 m 3 ha –1 ). Due to the relatively small dimensions of the large wood pieces located inside bankfull edges (83% of the total surveyed pieces), almost the 70% of them demonstrated to have been transported by runoff and 6% derived from bank erosion or landslides. Wood jams exert a significant influence on the channel morphology, being responsible for the creation of 30% of pools. The geomorphic influence of LW jams is also exerted by a considerable sediment storing capacity (about 1,750 m3). The LW-forced pool volume is strongly and positively correlated to the height of the LW jam. The results confirm that dead wood pieces, especially when organized in jams, play an important geomorphic role also in sub-Antarctic streams. The amount of large wood pieces quantified in the study site represents reference values for the assessment of the geomorphic effects of beaver activity in other Tierra del Fuego streams.

Species richness and faunistic affinities of the Gammaridea and Corophiidea (Amphipoda) from shallow waters of southern Tierra del Fuego, Argentina: preliminary results

Species richness and faunistic affinities of gammaridean and corophiidean amphipods from southern Tierra del Fuego were studied. The material was collected with dredges and grabs at 7 locations (15 sampling stations) in a range of 5 to 35 m depth. A total of 61 species belonging to 20 families and 43 genera were identified. The genera Cephalophoxoides, Ceradocopsis and Photis are reported for the first time from the Magellan region and 3 species belonging to Atylus, Ischyrocerus and Photis appear to be new to science. Most of the species collected belong to Phoxocephalidae, whereas most individuals were contained in the Stenothoidae and Lysianassidae s.l. The analysis of the faunistic affinities showed that 16 species (39%) are endemic to the Magellan region, 9 species (22%) extend to the south, 5 species (12.2%) to the north and 5 other species (12.2%) to both the north and south. In addition, 6 species extend beyond the Magellan region as far as Oceania.

Vegetation patterns, plant distribution and life forms across the alpine zone in southern Tierra del Fuego, Argentina

AbstractThe alpine zone is examined at meso‐ and microscales in southern Tierra del Fuego (54°49′S), where the full zone is expressed. Mesoscale patterns were studied on opposing aspects, and microscale patterns were studied on a series of solifluction terraces, in a hanging valley overlooking the Beagle Channel. Plant cover and life form data were collected within 50‐m altitudinal bands on north and south aspects and comprehensive plant lists were compiled for each band. Topography and associated surface cover were recorded on the terraces. Six alpine plant communities, in lower and upper floristic zones, were differentiated with multivariate analyses and significantly related to five ecological factors. Equivalent communities were separated by approximately 185 m altitude on opposing aspects, which related to a soil temperature difference of approximately 3.0°C. The richness (and range) of 80 local vascular taxa (18.6% of the regional flora), decreased with increasing altitude (6.6 per 100 m); however, richness differed significantly with aspect (north: 5.6, south: 7.5). Upper altitudinal limits (approximately 1250 m a.s.l.), were associated with a midsummer isotherm of approximately 1.7°C. Chamaephytes and hemicryptophytes dominated throughout but the tall tussock form was conspicuously absent. Reasons for this are discussed in the context of the Nothofagus treeline, which conformed to a midsummer isotherm of only approximately 6.0°C. Such patterns are at variance with those found in the oceanic subantarctic islands, other oceanic perhumid temperate mountain regions and tropical high mountains. However, the microscale pattern of fines, pebbles, stones and rock across the active solifluction terraces, with dense vegetation on their steep risers, had a clear affinity with that of other subantarctic regions. Inferences that alpine systems of the Southern Hemisphere are necessarily equivalent to those at similar northern latitudes are cautioned against. Likewise, such comparisons within the Southern Hemisphere may also be invalid.

Paleovegetational and paleoclimatic changes during the Late Quaternary in southwestern Buenos Aires Province and Southern Tierra del Fuego (Argentina)

Pollen analysis from a sedimentary section in the valley of the Sauce Grande River (southwestern Buenos Aires Province) and a peat core from the Andorra Valley (southern Tierra del Fuego) provides evidence for the apparent large‐scale synchroneity of major past vegetational changes and inferred climatic trends during the late Pleistocene and Holocene in this region. Climate before 10,000 years B.P. was relatively cold and dry, both in southwestern Buenos Aires Province and in southern Tierra del Fuego. A climatic amelioration to wanner and wetter conditions during the late Pleistocene and early Holocene is recorded in both regions. Late Holocene climates show greater variability and they suggest the onset of modern environmental conditions as represented by cool and wet conditions in southern Tierra del Fuego, and by arid to semi‐arid conditions in southwestern Buenos Aires Province.

Younger Dryas in southernmost south America — An update

High resolution pollen data from a peat section in southern Tierra del Fuego documents high paleoenvironmental variability between 11 ka and 9 ka. Detailed analysis of plant macro remains in the same section showed that the repeated high-amplitude changes in pollen taxa were related to repeated fire disturbance burning at least once even the surface of the mire. In many peat sections from southernmost Patagonia and Tierra del Fuego charcoal particles have been found intermittently since about 13 ka and in great abundance especially after 11 ka. This suggests that the environmental changes previously interpreted to imply a return to colder climates comparable to the North Atlantic Younger Dryas event instead are in response to local and regional disturbances by fires.

Geometry and Evolution of the Frontal Part of the Magallanes Foreland Thrust and Fold Belt (Vicuna Area), Tierra del Fuego, Southern Chile

The Magallanes foreland thrust and fold belt is a thin-skinned foreland thrust and fold belt of Paleocene to Oligocene age that deforms Upper Jurassic through Tertiary volcanic, volcaniclastic, and siliciclastic strata of the Magallanes basin, southern Andean Cordillera, Chile. This paper is a detailed description and analysis of the geology and structural evolution of the thrust front (Vicuna area of southern Tierra del Fuego). Reflection seismic and well data, together with 1:50,000 scale geological mapping, have been used in the analysis. In the southern part of the Vicuna area, two different thrust systems have been found: an upper imbricate fan that deforms Upper Jurassic and Cretaceous strata, and a younger, lower duplex composed of Cretaceous and probably Upper Jurassic rocks. The imbricate fan is characterized by fault-propagation folding in which listric thrust faults merge downward into a sole thrust that probably is located within the Upper Jurassic stratigraphy. This fan system generates an intercutaneous wedge with a well-developed triangle zone at its leading edge. The sole thrust of the upper imbricates forms the roof thrust of the underlying duplex. In the northern part of the Vicuna area, the syntectonic sedimentary wedge of the foredeep consists of Late Cretaceous through Tertiary siliciclastics that have been deformed and uplifted by passive back thrusting at the triangle zone. The structural style in the foreland region shows three main subhorizontal detachment levels located within the sedimentary wedge as a result of the progressive transfer of slip from the thrust belt to the foreland. Minor blind thrusts produce stacked pop up and triangle structures that result in complex geometries in the cores of anticlines. A forward-breaking sequence of thrusting is interpreted. During deformation, the active foredeep wedge migrated at least 10 km northward. Balanced geological cross sections indicate approximately 60% (-30 km) shortening for this part of the Magallanes thrust belt.

Late-glacial and Holocene vegetation and climate of Subantarctic South America

Extending >8° farther south than other land masses in the mid-latitude Southern Hemisphere, South America at 56°S comes closest to the Antarctic. Thus, climate reconstructed from fossil pollen in southern Tierra del Fuego (55°S) is a measure of conditions in Antarctica and the Southern Ocean. Assemblages over the past 13,500 years at first show limited expanse of southern beech under moderating conditions, followed by impoverished tundra implying coldest, driest climate after 13,000 and before 10,500 years B.P., and later, warming with the spread of beech and, after 5000 years B.P., cooler, mesic conditions with development of beech forest and mires. Data confirm changes of antarctic isotope temperature in the Byrd Station, Dome C, and Vostok ice cores.

Climate and chronology of Antarctica and adjacent South America over the past 30,000 yr

Well-dated records of paleoclimate, essential for developing general circulation models of the atmosphere during the Quaternary, are limited in the subpolar Southern Hemisphere. For Antarctica, where dating is particularly restricted, records from distal South America provide a measure to assess antarctic ice sheet chronology and to establish the timing of past climatic events. Of the continental and insular land masses in the middle latitudes, South America lies closest to Antarctica and most reflects conditions in the polar region. Close-interval dating of a pollen record at Harberton (54°52′S, 67°53′W) in southern Tierra del Fuego strengthens implications drawn from paleoecological data and from fluctuations of glaciers to show a climatic parallel with isotope temperature/climate data developed from antarctic ice cores. Over the time span of approximately 30,000 yr since before the full glacial, coldest conditions both in Antarctica and South America appear centered at 20,000 yr B.P. Warming of climate occurred in the late-glacial after 15,000 yr B.P., interrupted by a cold episode between about 13,000 and 10,500 yr B.P., with maximum warmth at 9000 yr B.P. in the early Holocene, after which temperatures were lower, varying only moderately until the present. This deglacial pattern, although inconsistent in other Southern Hemisphere records, is reproducible on a global scale.

Late Quaternary vegetation and climate of southern Tierra del Fuego

Vegetation and climate over approximately the past 13,000 yr are reconstructed from fossil pollen in a 9.4-m mire section at Caleta Róbalo on Beagle Channel, Isla Navarino (54°56′S, 67°38′W), southern Tierra del Fuego. Fifty surface samples reflecting modern pollen dispersal serve to interpret the record. Chronologically controlled by nine radiocarbon dates, fossil pollen assemblages are: Empetrum-Gramineae- Gunnera-Tubuliflorae (zone 3b, 13,000–11,850 yr B.P.), Gramineae- Empetrum-assorted minor taxa (zone 3a, 11,850-10,000 yr B.P.), Nothofagus-Gramineae-Tubuliflorae-Polypodiaceae (zone 2, 10,000–5000 yr B.P.), Nothofagus-Empetrum (zone 1b, 5000-3000 yr B.P.), and Empetrum-Nothofagus (zone 1a, 3000-0 yr B.P.). Assemblages show tundra under a cold, dry climate (zone 3), followed by open woodland (zone 2), as conditions became warmer and less dry, and later, with greater humidity and lower temperatures, by closed forest and the spread of mires (zone 1). Comparisons drawn with records from Antarctica, New Zealand, Tasmania, and the subantarctic islands demonstrate broadly uniform conditions in the circumpolar Southern Hemisphere. The influences of continental and maritime antarctic air masses were apparently considerable in Tierra del Fuego during cold late-glacial time, whereas Holocene climate was largely regulated by interplay between maritime polar and maritime tropical air.

Phylogeny and Historical Biogeography of Steamer-Ducks (Anatidae: Tachyeres)

-An earlier phylogenetic analysis of morphological characters (Livezey, 1986a) indicates that Tachyeres is a member of a specialized clade of Southern Hemisphere shelducks (Tadorninae). Within Tachyeres, the three flightless species appear to be monophyletic, with the two Atlantic species-T. leucocephalus and T. brachypterus-being closest relatives. This phylogenetic hypothesis mirrors the pattern of morphometric similarities among the four species. Speciation in the genus is explainable by the isolation caused by two major glaciations in southern South America and related fluctuations in sea level, and intervening dispersals. The biogeographic model is compared to a morphometric assessment of populations of T. patachonicus and electrophoretic analyses of the four species of Tachyeres. [Anatidae; flightlessness; glaciation; historical biogeography; Patagonia; phylogenetics; Pleistocene; South America; steamer-ducks; Tachyeres.J 'Ihe importance of knowledge of phylogenetic relationships is appreciated widely, not only for the construction of natural classifications of organisms (Cracraft, 1974; Farris, 1976; Wiley, 1981), but also as a basis for an understanding of historical constraints on morphology (Alberch, 1981; Lauder, 1981, 1982; Felsenstein, 1985) and biogeography (Wiley, 1981). Historical constraints are especially important in closely related species-groups in which some members share a strong, derived morphological trend (Grehan and Ainsworth, 1985). Four species of steamer-duck are recognized (Humphrey and Thompson, 1981): (1) flying steamer-duck (Tachyeres patachonicus) of freshwater and marine habitats throughout southern Argentina, Chile, and the Falkland Islands; (2) Magellanic flightless steamer-duck (T. pteneres) of coastal habitats of southern Chile and Tierra del Fuego; (3) white-headed flightless steamer-duck (T. leucocephalus) of coastal Chubut, Argentina; and (4) Falkland flightless steamer-duck (T. brachypterus) of the marine shores of the Falkland Islands. I review previous evaluations of the relationships of Tachyeres to other waterfowl and present a morphologically based phylogenetic analysis of the four species of steamer-ducks. The resultant phylogenetic hypothesis is related to the current knowledge of the geological history of the region, especially the role of glaciations as vicariance events in the marine littoral of southernmost South America. A speciation model then is compared to morphometric analyses and electrophoretic studies of the genus. OPINIONS REGARDING RELATIONSHIPS

The Pallid Falcon Falco kreyenborgi Is a Color Phase of the Austral Peregrine Falcon (Falco peregrinus cassini)

Abstract The Pallid Falcon (Falco kreyenborgi), a rare form from southern Patagonia and Tierra del Fuego, has, since its discovery in 1925, gained acceptance as a full species. In 1981, we observed 13 Pallid Falcons on the Patagonian Steppe. Four adult Pallid Falcons were paired with normal Peregrine Falcon (Falco peregrinus cassini) mates. Two normal-phased peregrine pairs produced mixed broods of normal and pallid young. One pair of pallid adults produced only pallid young. These observations lead to the conclusion that the Pallid Falcon is conspecific with and a color phase of the Peregrine Falcon.

The supposed discovery of South Georgia by Amerigo Vespucci

There have been few more controversial figures in the history of exploration than Amerigo Vespucci, and it is therefore necessary to be extremely cautious in deciding whether he did, or did not, discover the island of South Georgia in the year 1501. Humboldt and Mill believed that he might have done so, but thought that, on the whole, his most likely landfall was southern Patagonia or Tierra del Fuego. Matthews, who devoted considerable attention to working out distances and directions, came to the conclusion that Vespucci very probably arrived at South Georgia after leaving the coast of Brazil and sailing south-westwards, while the Australian map of Antarctica, published in Canberra in 1939, and the Antarctic Pilot (London, second edition, 1948) have respectively described this achievement as a probability and as a possibility.