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     

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).     

Two new species of Penicillium from the Tierra del Fuego (Argentina and Chile)

Two new species of Penicillium Link ex Fries are described and illustrated. They were recovered from sandy soils in the Chilean and Argentinian Tierra del Fuego. They clearly differ from all species of the genus described so far and are, therefore, described and proposed as two new taxa: Penicillium turris-painensis sp. nov and Penicillium lapatayae sp. nov.     

Pelagic swarms and beach strandings of the squat lobster Munida gregaria (Anomura: Munididae) in the Beagle Channel, Tierra del Fuego

The present article is the first formal record of pelagic swarms and beach strandings of the squat lobster Munida gregaria in the Beagle Channel, southern South America. To describe size composition and natural diet of beach strandings and swarms, samples from strandings were taken in April 2007, March 2008 and March 2010. Samples from swarms were taken in May 2007 and April 2010. Also, during November 2008 and January 2009, two acoustic surveys were carried out to describe both, horizontal distribution and school metrics of swarms. Pelagic swarms and beach strandings were composed of 100% individuals of the morph gregaria of M. gregaria. Mean size of males and females in both, beach strandings and swarms, were similar. The diet of pelagic M. gregaria was composed mainly of crustaceans, unicellular algae and small macroalgae, sediment and particulate organic matter. Swarms of pelagic Munida took the shape of extended layers of varying density and height. Their positions in the water column were also variable: swarms were found at different depths, from the subsurface layer to near the sea bottom. Occasionally, some large swarms occupied most of the water column. In the Beagle Channel, SW winds during spring tides could be a forcing factor for M. gregaria strandings. The absence of shoaling animals in the Beagle Channel between 1997 and 2002 and the recent occurrence of swarms are coincident with their appearance in other locations in Patagonia. In consequence, we hypothesize that the factor influencing the formation of swarms must be acting at a regional scale.     

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.     

The role of the predator Trophon geversianus in an intertidal population of Mytilus chilensis in a rocky shore of the Beagle Channel,Tierra del Fuego,Argentina

Predation influences changes in the abundance and the limits of spatial distribution of organisms on rocky shores. We quantified the effect of the predation pressure of the gastropod Trophon geversianus on the mytilid Mytilus chilensis in a rocky intertidal community of the Beagle Channel, Tierra del Fuego. We quantified the density of T. geversianus along with the density of T. geversianus preying on M. chilensis and examined the potential relationship between sizes of both T. geversianus and M. c hilensis. Additionally, we carried out laboratory experiments to quantify the drilling and ingestion rates of T. geversianus on M. c hilensis at different aerial exposure times. At mid intertidal levels, unlike at low intertidal levels, T. geversianus consumed more frequently the available size range of mussels. On average, sizes of predator and prey consumed were positively correlated. The drilling rate decreased with increasing time of aerial exposure. Additionally, permanently submerged predators invested less time consuming the same amount of food than individuals exposed for 4 out of 12?h (4/12?h). Predators exposed for 9/12?h invested less time and consumed less food than those exposed 4/12?h. Our results suggest that T. geversianus is an efficient predator of M. chilensis, due to both its high density and feeding rate. Our results suggest that the strong predation pressure of T. geversianus on M. chilensis prevents this key competitor from monopolizing space at the low level through controlling their abundance, and further limits their vertical distribution.     

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.     

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.     

Human-nature connection and soundscape perception: Insights from Tierra del Fuego,Argentina

Human disconnection from nature is thought to have contributed to the environmental crises we currently face, and increasing connection with nature has been proposed as one way of promoting pro-environmental behavior, nature conservation, and social-ecological sustainability. Some efforts to increase connection with nature (“nature relatedness”) have centered on exploring the social-ecological importance of soundscapes, but there is a paucity of empirical evidence supporting the theoretical linkage between soundscape perception and nature relatedness. Using prerecorded and in situ soundscape prompts, we conducted a street intercept survey in Ushuaia, Tierra del Fuego, Argentina to assess: 1) the relative importance of senses in experiences of nature, 2) the relationship between nature relatedness and soundscape perception, 3) differences in soundscape perception between various soundscapes, and 4) possible sociodemographic influences on sense importance, nature relatedness, and soundscape perception. Participants reported that hearing was of secondary importance to vision in experiences of nature. We also found that nature relatedness was positively correlated with the valuation of soundscapes—particularly more natural ones—but not with the discernment of soundscapes or identification of where soundscapes were recorded. Valuation of more natural soundscapes was higher than valuation of more technophonically dominated soundscapes, while soundscape discernment and location identification were higher for soundscapes that were likely more familiar to listeners. Sociodemographic influences on these variables were minor, but women reported higher sense importance, and having a nature-based occupation was associated with higher nature relatedness and valuation of a soundscape from a penguin colony. Our study highlighted a number of potential research areas concerning soundscape perception, including differences between prerecorded and in situ soundscape prompts, defining various aspects of soundscape perception, and the relative influences of sound sources and quantitative acoustic parameters on soundscape perception. Further research is certainly needed to account for global diversity in cultures and soundscapes, but we found some promising empirical support for the use of natural-soundscape-focused educational programs in efforts to promote nature relatedness.     

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).     

Structure and tree-fall gap dynamics of old-growth Nothofagus forests in Tierra del Fuego,Argentina

Abstract. Tree size and age structure, tree-fall and gap characteristics, and regeneration in gaps were studied in Nothofagus-dominated old-growth forests in Tierra del Fuego, Argentina. Gap-phase regeneration has resulted in all-aged populations for N. pumilio, N. betuloides, and Drimys winteri, and regeneration in gaps appears to be maintaining coexistence between species in mixed stands. N. betuloides fills many gaps via advance regeneration and some individuals persist for > 150 yr in the understory. Multiple periods of release and suppression indicate that N. betuloides may take advantage of several gap events to reach the main canopy. Likewise, Drimys grows well under closed canopy and can rapidly respond to gap formation, sometimes impeding the regeneration of N. betuloides. In contrast, N. pumilio regenerates in gaps mainly from seed or from advance regeneration of small, ephemeral seedlings. Gap turnover times in Fuegian forests were estimated at 300 - 500 yr, although gap formation was highly episodic and possibly associated with regionally extensive windstorms, earthquakes, and stand-level dieback. 92 % of gaps involved multiple tree-falls, and at least 53 % involved secondary expansion. Gap and tree-fall characteristics in Tierra del Fuego were similar to results from northern Patagonia, Chile, and New Zealand; however, we emphasize that regeneration of Nothofagus spp. and Drimys winteri in gaps depends on associated vegetation and varies along both local and regional environmental gradients.     

Community structure of lice (Insecta: Phthiraptera) from two sympatric gull species: kelp gull (Larus dominicanus) and Franklin's gull (Larus pipixcan) in Talcahuano, Chile

A total of 1,177 lice of four species were collected from 124 kelp gulls (Larus dominicanus) and 137 lice of the same four species from 60 Franklin's gulls (Larus pipixcan). The louse Saemundssonia lari (O Fabricius) (Phthiraptera: Philopteridae) was the most numerous on both gull species, with infestation rates of 4.9 on kelp gulls and 1.8 on Franklin's gulls. The second most abundant louse was Quadraceps punctatus (Burmeister), with a high infestation rate but low prevalence on kelp gulls; those parameters were much lower among lice from Franklin's gulls. The composition and community structure of the lice were similar on both host species, but not their infestation rates. In addition, the feather mite Zachvatkinia larica Mironov (Acari: Avenzoariidae) is recorded from kelp gulls and Franklin's gulls for the first time, while the gamasid mite Larinyssus sp. is recorded from kelp gulls, also for the first time. The population parameters of all species of ectoparasites are discussed.     

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.     

The subtidal macrobenthic assemblages of Bahía San Sebastián (Tierra del Fuego,Argentina)

Bahía San Sebastián (BSS), a shallow and protected environment on the eastern coast of Tierra del Fuego (Argentina), is a prime habitat for several species of nearctic migratory birds that visit the area during summer to feed in its huge intertidal mudflats. The area has also great economic value due to the extraction and transport of hydrocarbons. Twenty-three dredge stations were analysed and presence/absence data were used to classify stations and species by cluster analysis. Two algae and 113 taxa of macrobenthic invertebrates from 12 animal phyla were identified. Species richness was one order of magnitude higher (mean 29.0 sp st⁻¹) in stations located outside or in the southern unprotected section of BSS than in most muddy or sandy stations within the bay (mean 3.7 sp st⁻¹). Hard bottom stations outside BSS were dominated by a rich assemblage of sessile filter-feeders, mainly bryozoans, hydrozoans, ascidians, sponges, and the bivalve Aulacomya atra. Soft bottom areas inside BSS were mainly populated by relatively few species of deposit-feeders, such as the orbiniid polychaete Phylo felix, which was particularly frequent and widespread. Shells of the clam Mulinia edulis are very common, representing one of the few hard substrata available for sessile species on soft bottoms. Epibenthic assemblages within BSS were dominated by the detritivorous isopod Serolis paradoxa and the crab Eurypodius latreillei. The macrobenthic fauna of BSS can be regarded as typical of the Magellan region, showing affinities with those of other localities around Tierra del Fuego, the Straits of Magellan and the southern Chilean fjords.     

Historical demography and spatial genetic structure of the subterranean rodent Ctenomys magellanicus in Tierra del Fuego (Argentina)

Ctenomys (tuco‐tuco) is the most numerous genus of South American subterranean rodents and one of the most genetically diverse clades of mammals known. In particular, the genus constitutes a very interesting model for evolutionary studies of genetic divergence and conservation. Ctenomys magellanicus is the southernmost species of the group and the only one living in Isla Grande de Tierra del Fuego (Argentina). This species presents two chromosomal forms (Cm34 and Cm36) fragmented into demes distributed from the north region (steppe) to the south region (ecotone) of the island, respectively; no hybrids or overlapping areas were detected. To study the historical demography and the spatial genetic structure of the C. magellanicus population we used mitochondrial DNA (mtDNA) (D‐loop and cytochrome b) and microsatellite loci. Nine mtDNA haplotypes were identified, three of them belonging to the north and the other six to the south. Shared haplotypes between regions were not detected. mtDNA and microsatellite genotypes showed a marked pattern of population structure with low values of genetic flow between regions. The south is made up of small populations or isolated demes making up an endogamic metapopulation with unique alleles and haplotypes. Also, the results suggest a northward expansion process starting from an ancestral haplotype from the south. That population might have lived at a refuge through the adverse Pleistocene environmental conditions that took place at Tierra del Fuego. Results of this study are relevant to the conservation of C. magellanicus, suggesting that each region (north and south) might be considered as an Evolutionarily Significant Unit. © 2013 The Linnean Society of London     

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     

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.