Magellanic woodpecker ( Campephilus magellanicus) abundance and foraging in Tierra del Fuego, Chile

The Magellanic woodpecker (Campephilus magellanicus) is a vulnerable and poorly studied bird in the sub-antarctic deciduous and evergreen beech (Nothofagus) forests of South America. On Tierra del Fuego island (Chile), we compared Magellanic woodpecker abundance and its foraging habitat in two forest types: pure N. pumilio and mixed forests composed by N. pumilio and N. betuloides, including managed and non managed stands. At a regional scale, abundance of woodpeckers was greater in landscapes including both forest types than in pure N. pumilio landscapes. When both forest types occurred together, woodpecker abundance did not differ between them. The number of trees with foraging signs was correlated with Magellanic woodpecker abundance and was also associated with N. betuloides and snag densities, but was not affected by forest management. Occurrence of pecking on foraging trees was greater in mixed Nothofagus than pure N. pumilio stands. Woodpeckers foraged disproportionately more on larger diameter and more decayed trees. Moreover, trees used for foraging were positively correlated with canopy cover and snag density and were negatively correlated with distance to nearby peatlands and beaver ponds. Direct observation revealed that the flying distance between trees was negatively correlated with proportion of trees with foraging signs. Woodpeckers chose trees that were visited before, suggesting a pattern of tree recognition within foraging territories.Communicated by F. Bairlein     

New species of dictyostelids from Patagonia and Tierra del Fuego, Argentina

In late Jan and early Feb 2005 samples for isolation of dictyostelid cellular slime molds (dictyostelids) were collected in five different provinces and from six national parks (all located 39-55°S) in Patagonia and Tierra del Fuego, Argentina. Southern beech (Nothofagus) forests represented the primary vegetation type investigated, but some samples were obtained from Patagonian steppe, alpine meadows, Valdivian temperate rainforests and coniferous forests dominated by Araucaria, Austrocedrus and Fitzroya. Among the dictyostelids isolated from the samples we collected were seven species new to science. These species (Dictyostelium austroandinum, D. chordatum, D. fasciculoideum, D. gargantuum, D. leptosomopsis, D. valdivianum and Polysphondylium patagonicum) are described herein on the basis of both morphology and molecular (SSU rDNA) data. One of the new species, D. gargantuum, is one of the largest representatives of the group reported to date. Another unusual species, D. chordatum, produces long interwoven sorocarps that do not appear to respond to a spacing gas similar to the condition first noted in D. implicatum.     

First mitochondrial DNA analysis of the spectacled porpoise (Phocoena dioptrica) from Tierra del Fuego,Argentina

The spectacled porpoise (Phocoena dioptrica, Lahille, 1912) is one of the cetacean species about which least is known. Most information on the biology and ecology of this species has been obtained from stranded specimens and sightings at sea. In this study, analysis of 380 bp fragment of mitochondrial DNA (mtDNA) control region sequences (N = 50) was performed to provide a preliminary assessment of the genetic variation in spectacled porpoise specimens found stranded or by caught on the coast of Tierra del Fuego, Argentina. Results showed high levels of mtDNA diversity, as expected in large size and stable populations, and similar to other species of porpoises. The star-like shape phylogeny of haplotypes indicates a recent population expansion. This is the first report on the genetic variation of this species. Other lines of evidence (microsatellite loci, single-nucleotide polymorphism (SNPs)) are needed to improve our knowledge on the molecular biology of the spectacled porpoise.     

Comparative analysis of the phytoplankton communities of a peat bog from Tierra del Fuego (Argentina)

The phytoplankton communities of five water hollows and a river from the Rancho Hambre peat bog (Tierra del Fuego, Argentina) are compared as to species composition and densities, as well as morphological, chemical and physical data.A total of 212 taxa is reported, the river having the highest species richness (105) and algal density (6374 ind. ml^–1). Water hollows showed remarkable differences in the structure of their phytoplankton communities.A cluster analysis, based on species presence-absence, clearly distinguishes the river from the water hollows. The hollows fall into groups. One contains the shallow ones the other, the smallest, deepest ones.Correlation analyses between biotic and abiotic variates shows strong correlations between the relative frequencies of some major groups (Chrysophyceae, Euglenophyceae, Tribophyceae) and the values of abiotic variables (alkalinity, pH, conductivity and dissolved phosphate).     

Aquatic microinvertebrate abundance and species diversity in peat bogs of Tierra del Fuego (Argentina)

Peat bogs are regarded as extreme environments due to their low pH and low nutrient concentration, and thus hold a unique biota adapted to these particular conditions. The island of Tierra del Fuego encompasses the southernmost extensive peat bog area in the world, and is therefore particularly interesting from a biogeographical viewpoint. Within the same peat bog, different environment types can be identified: clear ponds, vegetated ponds and Sphagnum patches. In this study we compare the abundance, richness and species diversity of microinvertebrates (Copepoda, Cladocera and Rotifera) in these three types of environments from two peat bogs (Andorra and Rancho Hambre). Out of the 29 taxa recorded, 19 were common to both peat bogs, including four cladocerans endemic to Southern Patagonia and three rotifers endemic to Fuegian peat bogs. The rotifers were the dominant group in all environment types from Rancho Hambre, while in Andorra the Sphagnum moss was dominated by copepods, particularly harpacticoids. The results revealed that the environment type rather than peat bog was the key factor at explaining differences in species richness and diversity among microinvertebrate communities. This study highlights the importance of Sphagnum moss as a low diversity extreme environment which supports highly endemic species.     

Nest site selection of the Kelp gull (Larus dominicanus) in the Beagle Channel, Tierra del Fuego, Argentina

Nest site selection of Kelp gulls Larus dominicanus breeding in Conejo and Bridges islands, Tierra del Fuego, Argentina, was assessed between 14 and 30 December 2005 to describe variability in nest site features and determine variables affecting nest choice. Fourteen microhabitat variables were quantified at 40 nest sites and at 40 random points in each island during the late incubation stage. Nests at the two colonies were placed on different kinds of substrates across areas with varying degrees of cover provided either by rocks or vegetation. Despite the variability observed in nest site features, rock cover and rocky substrates were the main factors determining nest site selection. At Conejo Island, nest sites presented more rock cover, less percentage of vegetation cover and of vegetation debris substrate, and were placed further from the nearest vegetation in comparison to random points. Similarly, gulls at Bridges Island selected nest sites with more rock cover which were placed mainly on rocky and vegetation substrates. This contrasts with results previously obtained in Argentina, which indicated that vegetation is a key factor influencing Kelp gull nest site selection. Over 80% of the nests at both study colonies were placed on the northern slopes of the islands, relatively more protected from the strong prevailing southwest winds, and nests at both colonies tended to be more protected on their southern side either by rocks or vegetation. Results obtained at Tierra del Fuego confirm the plasticity of microhabitat use by Kelp gulls, and their ability to take advantage of nesting sites according to availability and local environmental factors.     

Saprolegnia oliviae sp. nov. isolated from an Argentine river (Tierra del Fuego Province,Argentina)

Saprolegnia oliviae sp. nov. is described from litter (floating dead twigs, leaves and roots) in the Olivia River, Ushuaia Department, Tierra del Fuego Province (Argentina). The new species is illustrated and compared with other species of the genus. Distinguishing characteristics of S. oliviae are the production of smooth oogonia (with some lateral or terminal projections) and the absence of antheridial branches on the majority of the oogonia, but when present, they are mostly diclinous, at times oogonia are supplied with androgynous and monoclinous antheridial branches. The oogonial stalks are predominantly short and straight or long and bent, curved or many times coiled; oospores are distinctive subcentric, (1-) 15-50 (-70) per oogonium. Morphological details of the new species and its comparison with other described species are discussed here.     

Distribution, abundance and associations of seabirds in the Beagle Channel, Tierra del Fuego, Argentina

We studied the distribution and abundance of seabirds along the Beagle Channel during February and March 1997. We examined the distribution and abundance, following the strip transects methodology, of species and their relation with habitat and foraging strategy of the birds. We divided the study area into six zones a priori. We made 20 trips aboard tourist vessels. The species most abundant in the study area were the imperial cormorant, dolphin gull, kelp gull, black-browed albatross, South American tern and Chilean skua. We concluded that seabirds were distributed non-randomly in the marine environment of the Beagle Channel. The shallow waters present the largest seabird density in the Beagle Channel. The Islas Bridges zone had the highest total density of seabirds, followed by the Bahía Ushuaia zone. The first zone holds colonies of most of the seabird species nesting in the channel. The presence of seabirds in the Bahía Ushuaia zone is influenced by the Islas Bridges zone itself, from where breeding birds come, and also by Ushuaia city, the port and the open garbage dump, where birds that feed on carrion can find alternative sources of food. The distribution of species in the whole study area was related to the foraging strategies, interactions with other species and characteristics of the habitat. We identified three groups of bird species and four independent species by cluster analysis. The first group included the black-browed albatross and the Magellanic penguin, which were associated with deep waters. In the second group the imperial cormorant and Chilean skua were associated with shallow waters along the study area, especially in the Islas Bridges zone where these species breed. Lastly, the kelp gull and southern giant petrel formed interspecific groups on the coast in places influenced by humans. The independent species numbered four. The rock cormorant associated with shallow waters in kelp bed areas. Showing a completely different foraging behaviour from the rest of the species, the dolphin gull occurred in shallow waters in the Islas Bridges zone associated with sea lions' and cormorants' colonies. Diving petrels were associated with deep waters on the west side of the channel. The South American tern was distributed all along the study area. Accepted: 14 November 1999     

Trichomycetes living in the guts of aquatic insects of Misiones and Tierra del Fuego, Argentina

Fourteen species of Trichomycetes living in the guts of aquatic insects are reported from two provinces of Argentina, Misiones and Tierra del Fuego. Twelve of the species belong to the Harpellales and two are Amoebidiales. Five harpellid species are reported from Misiones in the extreme northeast of the country (Genistellospora homothallica, Harpella tica, Smittium culisetae, Smittium sp., Stachylina sp.) and seven are from Tierra del Fuego, the southern tip of South America (H. meridianalis, Glotzia sp., S. culicis, S. cellaspora, S. imitatum, Stachylina minima, Penella simulii). Insect hosts all were immature stages of Culicidae, Simuliidae, Chironomidae, Ceratopogonidae (Insecta: Diptera), and Ephemeroptera and Plecoptera. The lower diversity of Trichomycetes found at Misiones, which has a subtropical climate and rainforest vegetation, was due possibly to the warmer temperatures of the water (15-24 C), compared to the colder streams of Tierra del Fuego (9-15 C), with forests and steppes as typical vegetation.     

Magellanic Woodpecker (Campephilus magellanicus) sap feeding and its role in the Tierra del Fuego forest bird assemblage

Several woodpecker species feed on phloem-sap flowing from pecked trees. We report sap consumption by the magellanic woodpecker (Campephilus magellanicus) inhabiting beech (Nothofagus) forests of Tierra del Fuego island (Chile). Magellanic woodpeckers drilled sap wells in N. betuloides trees close to their nests and also when they were moving in family groups. Three other bird species were observed foraging and competing for sap: the austral parakeet (Enicognathus ferrugineus) and two small passerines, the patagonian sierra-finch (Phrygilus patagonicus) and the white-crested elaenia (Elaenia albiceps). The abundance of these three bird species was greater in sites around sap wells than in other forest sites, suggesting that magellanic woodpecker is an important species in maintaining the Nothofagus forest bird assemblage.     

Responses to solar ultraviolet-B radiation in a shrub-dominated natural ecosystem of Tierra del Fuego (southern Argentina)

A study was made of the effects of solar ultraviolet‐B radiation (UV‐B) on the growth of the dominant plant species of a shrub‐dominated ecosystem in Tierra del Fuego. This part of southern Argentina can be under the direct influence of the Antarctic ‘ozone hole’ during the austral spring and lingering ozone‐depleted air during the summer. The plant community is dominated by an evergreen shrub (Chiliotrichum diffusum) with an herbaceous layer of Gunnera magellanica and Blechnum penna‐marina in the interspaces between the shrubs. Inspections of ozone trends indicate that the springtime and summertime ozone column over Tierra del Fuego has decreased by 10–13% from 1978/9 to 1998/9. In a set of well‐replicated field plots, solar UV‐B was reduced to approximately 15–20% of the ambient UV‐B using plastic films. Polyester films were used to attenuate UV‐B radiation and UV‐transparent films (～90% UV‐B transmission) were used as control. Treatments were imposed during the growing season beginning in 1996 and continued for three complete growing seasons. Stem elongation of the shrub C. diffusum was not affected by UV‐B attenuation in any of the three seasons studied. However, frond length of B. penna‐marina under attenuated UV‐B was significantly greater than that under near‐ambient UV‐B in all three seasons. Attenuation of solar UV‐B also promoted the expansion of G. magellanica leaves in two of the growing seasons. Differences between treatments in leaf or frond length in B. penna‐marina and G. magellanica did not exceed 12%. Another significant effect of UV‐B attenuation was a promotion of insect herbivory in G. magellanica, with a 25–75% increase in the leaf area consumed. Changes in plant phenology or relative species cover were not detected within the time frame of this study. The results suggest that the increase in UV‐B radiation associated with the erosion of the ozone layer might be affecting the functioning of this ecosystem to some degree, particularly by inhibiting the growth of some plant species and by altering plant–insect interactions.     

Solar ultraviolet-B radiation affects plant-insect interactions in a natural ecosystem of Tierra del Fuego (southern Argentina)

We examined the effects of solar ultraviolet-B radiation (UVB) on plant-herbivore interactions in native ecosystems of the Tierra del Fuego National Park (southern Argentina), an area of the globe that is frequently under the Antarctic “ozone hole” in early spring. We found that filtering out solar UVB from the sunlight received by naturally-occurring plants of Gunnera magellanica, a creeping perennial herb, significantly increased the number of leaf lesions caused by chewing insects. Field surveys suggested that early-season herbivory was principally due to the activity of moth larvae (Lepidoptera: Noctuidae). Manipulative field experiments showed that exposure to solar UVB changes the attractiveness of G. magellanica leaf tissue to natural grazers. In a laboratory experiment, locally caught moth caterpillars tended to eat more tissue from leaves grown without UVB than from leaves exposed to natural UVB during development; however, the difference between treatments was not significant. Leaves grown under solar UVB had slightly higher N levels than leaves not exposed to UVB; no differences between UVB treatments in specific leaf mass, relative water content, and total methanol-soluble phenolics were detected. Our results show that insect herbivory in a natural ecosystem is influenced by solar UVB, and that this influence could not be predicted from crude measurements of leaf physical and chemical characteristics and a common laboratory bioassay. Received: 4 December 1997 / Accepted: 12 May 1998     

Preliminary comments on a redescription of Pseudolithophyllum fuegianum and Titanoderma conspectum (Rhodophyta,Corallinales) in Tierra del Fuego,Argentina

The effect of twelve drugs and chemical compounds on the narcosis of Brachionus plicatilis was studied using standardized laboratory conditions. Drug efficacy was compared by calculating EC₅₀ (effective concentration causing narcosis in 50% of animals), time necessary to reach narcosis in 50% of animals, concentration range of activity, and degree of extension after preservation. The local anesthetic Bupivacaine was found to be most effective by all criteria. Our previous data and preliminary field experiments indicated that drug sensitivity varies widely, even between congeneric taxa. The anesthetic effect of carbonated water was also investigated.     

Assessing genetic variation and population structure of invasive North American beaver (<Emphasis Type=Italic>Castor Canadensis</Emphasis> Kuhl, 1820) in Tierra Del Fuego (Argentina)

The North American beaver (Castor Canadensis) was introduced into Isla Grande de Tierra del Fuego, Argentina in 1946 as a potential source of wild fur. The species showed high growth potential, reaching close to 100,000 individuals from an original founding stock of 25 females and 25 males. Beavers adapted rapidly to their new environment and became invasive, providing an excellent model of successful adaptation of introduced populations to a new habitat. In this study, we used polymorphic mitochondrial (mt) DNA to evaluate genetic variation in the introduced beaver population from Tierra del Fuego. Nucleotide variation in partial sequences of Cytochrome b (500 bp) and 12S rRNA (421 bp) genes and the main non-coding D-loop region (521 bp) were analyzed. Our study allowed to identify 10 different mtDNA lineages in the invasive population, none of them shared among the source populations. The pattern observed is a consequence of cessation of gene flow following expansion of the founding beaver population since the time of its introduction. This approach contributes to the understanding of effects of genetic changes on survival ability and reproductive success of invasive species. It also has important management implications to invasive species.     

Epidemiological surveillance of cystic echinococcosis in rural population of Tierra del Fuego, Argentina, 1997-2006

Cystic echinococcosis (CE) is the most prevalent zoonosis in Tierra del Fuego. In 1997, ulrasonography (US) was selected as the method of choice for the development of population surveys for epidemiological surveillance and early diagnosis in rural population. The aim of this work was to present the results of the epidemiological surveillance of CE by means of US in rural population of Tierra del Fuego, Argentina between 1997 and 2006. The ultrasonographic diagnostic was realized once a year. The population was stratified in children (4 to 17 years) and adults. From each individual, name, age, sex, actual residence and origin were registered. The images compatible with cysts were graded according to location, number and characteristics. A total of 1400 rural inhabitants were examined for CE. From the total of studied individuals, 27 (1.9%) exhibited images compatible with cysts on the abdominal ultrasound scan. Thirteen of these persons were finally diagnosed as having CE. The overall prevalence of CE was 0.9%. This value is in accordance with the decrease in the prevalence observed in the definitive host and the intermediate hosts (sheep and cattle). The absence of cases in children during the studied period, evidence no transmission of the disease to humans in the recent past.     

Reproductive cycle and reproductive output of the sea urchin Loxechinus albus (Echinodermata: Echinoidea) from Beagle Channel, Tierra del Fuego, Argentina

Reproductive cycle, frequency and duration of spawning, energetic content of gonads, and reproductive output of the common green sea urchin Loxechinus albus were analyzed in the Beagle Channel (Tierra del Fuego) between May 2004 and May 2005. Gonad indices (GI, percentages of gonad mass in total body mass) were significantly higher in March, April, July, and August than in November and May, thus showing a negative correlation with the photoperiod. Highest GI values of mature individuals were observed in August, and spawning occurred from September to December. In females, the mass-specific energy content of gonads (ECG) was highest in spawned gonads and lowest in mature ones, while in males ECG values were higher in immature stage and lower in premature and mature stages. High ECG values can be explained by the abundance of nutritive phagocytes. Both ECG and total gonad energy content (TECG) were higher in females than in males. Mean reproductive output was 7.28% for females and 6.15% for males (expressed as the difference between mean GI of mature and spawned gonads) and 25.02 kJ for females and 19.26 kJ for males (expressed as the difference between mean TECG of mature and spawned gonads).     

Knowledge of the endoparasitic fauna of Lama guanicoe Muller, 1776, from the Mitre Peninsula, Tierra del Fuego, Argentina

Parasitological fauna of Lama guanicoe in the Peninsula Mitre, Tierra del Fuego, Argentina, is analyzed in this paper. Coproparasitological tests of 58 samples were performed, and on this basis, the presence of the following genera was determined: Haemonchus, Marshallagia, Cooperia, Nematodirus, Ostertagia, Trichostrongylus, Oesophagostomun and Chavertia. Marshallagia and Chabertia are reported for the first time for this host. The dung piles are not considered as parasitic barriers. Infections occur in two seasons: at the beginning of the spring and at the beginning of summer, as a survival strategy of parasitic nematodes. Parasites of L. guanicoe would be secondarily acquired form cattle.