Mitochondrial DNA diversity of the Southwestern Atlantic humpback whale (Megaptera novaeangliae) breeding area off Brazil, and the potential connections to Antarctic feeding areas

In the Southwestern Atlantic Ocean, humpback whales migrate every winter to the Brazilian coast for breeding and calving in the Abrolhos Bank. This breeding stock represents the remnants of a larger population heavily exploited during the beginning of the 20th century. Despite its relevance to conservation efforts, the degree of current genetic variation and the migratory relationship with Antarctic feeding areas for this population are still largely unknown. To examine these questions, we sequenced ∼400 bp of the mitochondrial DNA control region from samples taken off the Brazilian coast (n = 171) and near the Antarctic Peninsula (n = 77). The genetic variability of the Brazilian humpback whale breeding population was high and similar to that found in other Southern Hemisphere breeding grounds. Phylogenetic analysis suggested the existence of a new mitochondrial clade that exists at low frequency among Southern Hemisphere populations. Direct comparison between the Brazilian and the Colombia breeding populations and the Antarctic Peninsula feeding population showed no genetic differentiation between this feeding region and the Colombian breeding area or between feeding Areas I and II near the Antarctic Peninsula. In contrast, these populations were genetically distinct from the Brazilian population. Two humpback whales sampled off South Georgia Islands, in the Scotia Sea, shared identical haplotypes to whales from Brazil. Our results, supported by photo-identification and satellite telemetry data, suggest that the main feeding area of the Southern Hemisphere humpback whale population is likely to be located near the South Georgia/South Sandwich Islands area and not in the Antarctic Peninsula.     

Foraging location and range of White-chinned Petrels Procellaria aequinoctialis breeding in the South Atlantic

The foraging range and principal feeding areas of White‐chinned Petrels breeding at South Georgia were determined using satellite telemetry. Foraging trips during incubation lasted 12–15 days and covered 3000–8000 km and 2–11 days and 1100–5900 km during chick‐rearing. Adults covered less distance per day during chick‐rearing (71 km) than during incubation (91 km) but the proportion covered at night (47%) was the same. Mean (31–34 km/h) and maximum (80 km/h) flight velocities were similar during both periods of the breeding season and during day and night. Between incubation shifts, White‐chinned Petrels travelled to the Patagonian shelf; during chick‐rearing they foraged more extensively. Most locations were between 30° to 55°W and 52° to 60°W around South Georgia/Shag Rocks and south to the South Orkney Islands. Diet samples from known foraging locations suggested birds fed mainly on krill and squid. They caught the squid Brachioteuthis? picta and Galiteuthis glacialis around Shag Rocks/South Georgia and also at sites close to the South Orkney Islands; Illex argentinus on the Patagonian shelf. Dispersal of adults after breeding failure was south to the South Orkney Islands then west to the Falkland Islands. This study confirms that breeding White‐chinned Petrels are amongst the widest‐ranging of seabirds; they may minimise competition with other Procellariiformes in the South Atlantic by their more extensive foraging range. The nature and extent of their range also brings substantial risk of high mortality rate in South Atlantic long‐line fisheries.     

Aspects of the biology of Antarctomysis maxima (Crustacea: Mysidacea)

Summary Population structure and aspects of the reproductive biology of Antarctomysis maxima from South Georgia and the South Orkney Islands were examined. Size frequency analysis indicated that the generation time is two years at South Georgia, but may approach four years at the South Orkneys. Egg production is greater for a given size of female at South Georgia but by virtue of a larger egg, brood production in terms of ash-free dry weight is slightly greater at the South Orkneys. Young are brooded over winter at both sites and are released in spring. Females are clearly capable of breeding twice at South Georgia and it is suggested that this is also the case at the South Orkneys. These results are discussed in relation to other studies on cold water mysids and to environmental adaptations exhibited by other Antarctic marine invertebrates.     

Food, feeding ecology and ecological segregation of seabirds at South Georgia

At the sub-Antarctic island of South Georgia 25 of the 29 breeding species are seabirds. Fifteen of these have recently been studied in some detail. By examining the timing of their breeding seasons and their diet and feeding ecology (especially feeding techniques and potential foraging ranges), the nature of their ecological isolating mechanisms, and in particular the way in which they partition the resources of the marine environment, are reviewed.
Although breeding season adaptations occur (winter breeding in Wandering Albatross and King Penguin; out of phase breeding in two species-pairs of small petrels) these are less important than dillerences in food and feeding ecology. There is a fundamental distinction between the niche of pursuit-diving species (mainly penguins) and the remainder which are basically surface-feeders. The two abundant krill-eating penguins show clear differences in feeding zones. Three albatrosses and a petrel feed mainly on squid and there are differences in both the species and size of the prey of each. The remaining seabirds chiefly take krill (although the giant petrels are extensive scavengers and some smaller petrels specialize on copepods) and utilize different feeding methods and areas to do so.
Various adaptations related to inshore and offshore feeding zones are discussed. Although most species possess a combination of ecological isolating mechanisms additional evidence for the particular importance of dietary differences is presented.     

Species and sexual isolating mechanisms in sibling species of giant petrels Macronectes

Summary The two sibling species of giant petrels Macronectes halli and M. giganteus are the dominant avian scavengers in the Southern Ocean ecosystem. They breed sympatrically at a number of sub-Antarctic sites. This paper synthesises data from a detailed study at South Georgia to examine the importance of various interspecific and intersexual differences between these closely related species. Morphological, breeding, dietary, feeding and moult characteristics were investigated. The most significant interspecific differences are a six week separation in the onset of breeding and the importance of seal carrion to male M. halli, the earlier breeding species. There is a strong sexual size dimorphism with females being only 75–80% of the weight of males in both species. Intersexual dietary differences are stronger than interspecific ones and females also have later primary moult schedules. Reproductive isolation and ecological adaptations are discussed in relation to the present distribution of giant petrels, comprising a more restricted sub-Antarctic species (M. halli) and a widespread Antarctic species (M. giganteus). It is suggested that the marked sexual dimorphism evolved before the two taxa became specifically distinct.     

Conservation and genetics of the frosted flatwoods salamander (Ambystoma cingulatum) on the Atlantic coastal plain

The federally threatened frosted flatwoods salamander, Ambystoma cingulatum, occurs in isolated populations on the coastal plain of northern Florida, Georgia and South Carolina. An earlier phylogeographic study based primarily on mitochondrial DNA (mtDNA) and morphometrics demonstrated that the previously recognized species A. cingulatum contained two cryptic species, and that two distinct mtDNA clades were contained within the newly restricted A. cingulatum. However, salamanders from the northern extent of the species range in South Carolina were not previously available for analysis. Here, we used individuals from a newly discovered South Carolina breeding site to determine whether A. cingulatum from South Carolina are genetically distinct from their more southerly conspecifics. These analyses included the mitochondrial gene studied previously as well as broad geographic sampling of three rapidly evolving nuclear genes that allowed us to further investigate lineage diversification of flatwoods salamanders. The mitochondrial and nuclear results are largely congruent, yielding strong support for two distinct species of flatwoods salamanders and also two lineages within the eastern species. Further, the South Carolina specimens are closely related to other haplotypes found in eastern Georgia and Florida. Our summary of field surveys over the past 20 years indicates that this South Carolina population may be one of only three remaining in the entire Atlantic coastal plain distribution of this rare and declining amphibian species.     

Identification and breeding biology of the diving petrels Pelecanoides georgicus and P. urinatrix exsul at South Georgia

Abstract

The biology of two species of diving petrel (Pelecanoides georgicus and P. urinatrix exsul) was studied at Bird Island, South Georgia. Existing criteria (bill shape and morphology, wing length) for distinguishing these species are reviewed, and several new characters are recognised. For adults bill depth, the colour of the posterior part of the tarsus, and vocalisations are distinctive; chicks have down of different colours (pale grey in P. u. exsul, dark grey in P. georgicus). At South Georgia the species breed in different habitats and at different times - P. u. exsul nests in steep tussock slopes in very early summer, P. georgicus in fine scree slopes in midsummer. P. georgicus lays a proportionately larger egg, and has an incubation period of 46 days (c.54 days in P. u. exsul) and a chick fledging period of 46 days. The fledging period of P. u. exsul is 54 days, very similar to recorded values for P. u. urinatrix (53.5 days) and P. u. chathamensis (56 days). Data on feeding frequency and feed size were derived from daily chick weighings and from twice-daily weighing during 30 days preceding fledging. In both species chicks are fed every night, and often by both parents. In P. georgicus true mean chick feed size is c.37 g; in P. u. exsul it may be slightly less. Analysis of chick stomach contents suggests that P. u. exsul feeds extensively on copepods, whereas P. georgicus largely takes krill (Euphausia superba). P. u. exsul breeding adults commence moulting before their chicks have fledged; P. georgicus moults exclusively in the non-breeding season. Ectoparasites were collected, and the feather louse Pelmatocerandra setosa was found to be restricted to P. u. exsul, and Pelmatocerandra enderleini to P. georgicus. P. georgicus, which breeds later and whose chicks fledge faster, is suggested to be better adapted to the climatic and marine environmental conditions than P. u. exsul, which may be the more recent colonist of these high latitudes.     

Ecological drivers of change at South Georgia: the krill surplus,or climate variability

Macaroni penguins Eudyptes chrysolophus are thought to be one of the most important mesopredators in the Southern Ocean having a greater impact on prey availability and abundance than any other seabird species. Their population centre has long been held to be South Georgia where populations were thought to comprise many million animals. Here we report the results of a recent census of the macaroni population at South Georgia undertaken using aerial survey methods. We report dramatic declines in numbers (～1.0 million breeding pairs) compared to numbers observed in the late 1970s (～5.4 million pairs), but show that these reductions have occurred principally at sites where numbers had previously been very large. During the breeding season, the main foraging grounds of birds from these sites overlap with the foraging grounds of Antarctic fur seals Arctocephalus gazella, a major competitor for their principal prey, Antarctic krill Euphausia superba. We suggest that the redistribution of the macaroni penguin population at South Georgia reflects the recent recovery of fur seal populations and thus the ongoing consequences of human intervention at South Georgia, a process which started more than 2 centuries previously. The implied resource competition and the observed population changes may also be exacerbated by recent reductions in Antarctic krill abundance which have been linked with reductions in seasonal sea ice following recent, rapid, regional warming in the Antarctic; however, the recovery of fur seal populations, and the ongoing recovery of krill‐eating whale populations argues that tropho‐dynamic interactions may be sufficient to explain the observed changes.     

Spatial and temporal variations in moss-inhabiting summer diatom communities from Potter Peninsula (King George Island, Antarctica)

This work represents the first analysis of the spatial and temporal variations in the diversity and community structure of diatoms associated with mosses, either dry or wet, sampled during the summer season from the littoral zone of three ponds in Potter Peninsula (King George Island, South Shetland Islands). It also seeks to explore the effect moisture content in the mosses can have on the structure of the diatom assemblages. The ponds approximately had the same number of species, and differences were found between the dry and wet sampling points. The same 4 species were predominant in the three ponds (Nitzschia alpina, N. perminuta, Staurosira oldenburgiana, and Pinnularia subantarctica var. elongata), but not in the same proportions. The first three species differed from those which were found to be dominant in other basins covered by mosses in southern South America and in the sub-Antarctic region. The latter, P. subantarctica var. elongata, had only been found to be abundant in a moss sample from another South Shetland Island. The diatom assemblages were found to be more strongly related to habitat traits (e.g. distance to the sea, ponds’ areas, and the vegetation’s moisture levels) than to the physical–chemical variables measured in the water.     

Dietary composition of juvenile Dissostichus eleginoides (Pisces, Nototheniidae) around Shag Rocks and South Georgia, Antarctica

A diet analysis of the Patagonian toothfish Dissostichus eleginoides, trawled in the South Georgia Islands area in March–April 1996, was carried out by frequency of occurrence (F%) and coefficient Q (%) methods. The samples consisted chiefly of immature specimens, with predominant length ranges of 30–70 cm (TL). Fish was by far the main food on the shelves of Shag Rocks and South Georgia, accounting for about 70% of prey. Krill appeared as secondary food, although its importance was overestimated by the frequency of occurrence method. Cephalopods and mysids were infrequent in the stomachs, and only at Shag Rocks and South Georgia, respectively. Lepidonotothen kempi, Champsocephalus gunnari and Chaenocephalus aceratus constituted the main fish prey and their variability between Shag Rocks and South Georgia depended on their local abundance. The large proportion of fish exhibiting stomachs full or close to fullness (together 62%) suggests that feeding intensity of the species was high.     

Collembola of sub-Antarctic South Georgia

Qualitative samples of Collembola were obtained from a range of substrates near Husvik, Stromness Bay, South Georgia, between January and March 1996. Collections made at Hope Point near Grytviken (Cumberland East Bay) in 1980/1982 and 1997 were also examined. Fifteen species of Collembola were recorded around Husvik; most were widely distributed. Two of these, Friesia sp. nov. and Cryptopygus badasa, represent additions to the previously recognised fauna of 17 species. A new record of an introduced species, Hypogastrura purpurescens, was identified in collections from Hope Point in 1980/1982, bringing the total South Georgian fauna to 20 species. A key to South Georgian Collembola is included. H. purpurescens and the congeneric Hypogastrura viatica, both cosmopolitan invasive species, have also been recognised on other sub-Antarctic islands and have displaced resident species from some habitats. Their presence on South Georgia, and the dominance of H. viatica in some habitats, highlight the importance of strict quarantine measures to avoid the introduction of further alien invertebrates. Accepted: 30 November 1998     

Bats benefit from beavers: a facilitative link between aquatic and terrestrial food webs

Bat populations are declining in many areas, partly because up to two-thirds of their wetland habitats have been lost. One natural agent creating wetlands is the beaver, which is recolonizing its former range. Beaver flowages are known for their high production of aquatic invertebrates. We tested the hypothesis that the high numbers of insects emerging from beaver flowages influences their use by foraging bats. We compared bat use and bat numbers above flowages of introduced Canadian beavers Castor canadensis and in nearby control ponds where beavers were absent. The two bat species detected, Eptesicus nilssoni and Myotis daubentoni, used beaver flowages more than non-beaver ponds. This is especially the case for Eptesicus nilssoni. Bats also seemed to forage in larger groups while above beaver ponds compared to the control ponds. Beaver flowages appeared to improve bat habitats. A plausible reason for this could be the high number of insects emerging from beaver ponds. Favouring the beaver in habitat management is a tool for creating suitable conditions for many other species, such as bats. In areas not suited for the beaver, insect production can be achieved by imitating the beaver with man-made impoundments. This is especially important in areas which have lost most of their wetlands.     

Microsatellite analysis reveals genetic differentiation between year-classes in the icefish <Emphasis Type="Italic">Chaenocephalus aceratus</Emphasis> at South Shetlands and Elephant Island

Chaenocephalus aceratus is one of the most abundant Antarctic icefish species in the Atlantic sector and has been a by-catch species in the fishery for mackerel icefish, Champsocephalus gunnari, between the mid-1970s and mid-1980s at South Georgia, South Orkney, and South Shetland Islands. The species became the target of the fishery in particular seasons, such as at South Georgia in 1977/78. In our paper, we report results on genetic differentiation for 11 microsatellite loci in C. aceratus samples collected at the South Shetlands and Elephant Island. This study represents the first report on microsatellite variability of an icefish species. Our results support the evidence from previous studies on differences in infestation patterns of parasites that a single panmictic population of C. aceratus exists, spanning the two sampling sites separated by about 100 km. Moreover, our study indicates the presence of a significant genetic differentiation between individual year-classes pointing out the existence of dynamic processes acting at the population genetic level, according to recent results for broadly distributed marine species. Both small effective population size and immigration from unsampled differentiated stocks may be at the base of the differentiation found in C. aceratus. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Chironomid assemblages from seabird-affected High Arctic ponds

Seabirds can shunt nutrients and contaminants from marine to terrestrial ecosystems by forming dense breeding colonies and releasing wastes to these sites. A large colony of seabirds at Cape Vera (Devon Island, High Arctic Canada) has resulted in eutrophic conditions and potentially toxic concentrations of sedimentary metals in several freshwater ponds that drain their nesting sites. Here, we investigated the effects of elevated nutrient and sedimentary metal concentrations on the distribution of subfossil chironomids in surface sediments from 21 ponds that span a gradient of seabird influence. Although many ponds registered high nutrient concentrations (e.g., mean TP = 45 μg l ⁻¹), eutrophic taxa typical of temperate waters were not common, with most assemblages being dominated by morphotypes of Psectrocladius and Tanytarsina, as well as Corynoneura arctica-type, and Metriocnemus hygropetricus-type. Although the ponds within and outside the area influenced by seabirds contained largely similar taxa, variations did exist in the relative abundances of the different species. Lakewater pH was the only measured environmental variable that explained statistically significant amounts of variation in the chironomid assemblages. Although direct effects of pH on chironomids cannot be ruled out, pH is likely tracking production-related changes driven by limnetic dissolved inorganic carbon dynamics. Sediment cores collected from seabird-affected and seabird-free ponds showed a greater number of chironomid taxa and higher head capsule abundances in the pond receiving seabird inputs. Chironomid assemblages in both cores recorded increased abundances in recent decades, likely in response to warmer conditions and lengthened growing seasons.     

Extinction and recolonization of maritime Antarctica in the limpet Nacella concinna (Strebel, 1908) during the last glacial cycle: toward a model of Quaternary biogeography in shallow Antarctic invertebrates

Quaternary glaciations in Antarctica drastically modified geographical ranges and population sizes of marine benthic invertebrates and thus affected the amount and distribution of intraspecific genetic variation. Here, we present new genetic information in the Antarctic limpet Nacella concinna, a dominant Antarctic benthic species along shallow ice‐free rocky ecosystems. We examined the patterns of genetic diversity and structure in this broadcast spawner along maritime Antarctica and from the peri‐Antarctic island of South Georgia. Genetic analyses showed that N. concinna represents a single panmictic unit in maritime Antarctic. Low levels of genetic diversity characterized this population; its median‐joining haplotype network revealed a typical star‐like topology with a short genealogy and a dominant haplotype broadly distributed. As previously reported with nuclear markers, we detected significant genetic differentiation between South Georgia Island and maritime Antarctica populations. Higher levels of genetic diversity, a more expanded genealogy and the presence of more private haplotypes support the hypothesis of glacial persistence in this peri‐Antarctic island. Bayesian Skyline plot and mismatch distribution analyses recognized an older demographic history in South Georgia. Approximate Bayesian computations did not support the persistence of N. concinna along maritime Antarctica during the last glacial period, but indicated the resilience of the species in peri‐Antarctic refugia (South Georgia Island). We proposed a model of Quaternary Biogeography for Antarctic marine benthic invertebrates with shallow and narrow bathymetric ranges including (i) extinction of maritime Antarctic populations during glacial periods; (ii) persistence of populations in peri‐Antarctic refugia; and (iii) recolonization of maritime Antarctica following the deglaciation process.     

Cetacean sightings near South Georgia islands,South Atlantic Ocean

The information about cetacean occurrence around the Island of South Georgia is scarce. With the main goal of gathering information on a feeding ground of humpback whales (Megaptera novaeangliae) that winter in Brazilian waters, we conducted an expedition to South Georgia. We present here the information regarding cetacean sightings during the expedition. From 28 January to 2 March, 2006 we carried out 13 research cruises, covering 700 nautical miles and 110 h of observation. We registered 10 sightings, in 7 h of ad libitum observations, of the following species: Megaptera novaeangliae, Eubalaena australis, Balaenoptera physalus, Mesoplodon layardii, Orcinus orca and Lagenorhynchus cruciger. We present data on location, depth, group size, structure, and behavior for this geographical area of essential importance for cetacean conservation.     

THE PROBLEM OF NOMENCLATURE

Whitfield, A. K. &; Blaber, S. J. M. 1978. Feeding ecology of piscivorous birds at Lake St Lucia, Part 3: Swimming birds. Ostrich 50:10-20. The diets, foraging periodicities and feeding behaviour of the Reed Cormorant Phalacrocorax africanus, Whitebreasted Cormorant Phalacrocorax carbo and White Pelican Pelecanus onocrotalus were studied at Lake St Lucia, Natal, South Africa, during 1975 and 1976. The Reed Cormorant fishes in shallow water within 100 m of the shore and mainly caught Sarotherodon mossambicus and Solea bleekeri, while the Whitebreasted Cormorant caught Mugilidae, Rhabdosargus sarba and Thryssa vitrirostris in deeper water. The diet of the White Pelican followed three distinct phases: a pre-incubation phase when the birds followed and preyed heavily on migrating Mugil cephalus shoals; an incubation and post-incubation phase when the adults flew a round trip of 200 km to the north to obtain freshwater fish, mainly cichlids, from the Pongolo pans where fishes were concentrated and densities high; and a post-fledgling phase when both adults and juveniles fed on a variety of marine species of fish in Lake St Lucia for about a month before dispersing to other areas. The feeding and breeding of Reed Cormorants and White-breasted Cormorants is discussed in relation to wind speeds, water turbidity and flooding of backwaters. The diet and long-range foraging behaviour of White Pelicans at St Lucia are compared with data from other African lakes. The breeding season of White Pelicans at St Lucia is related to availability of fish and inaccessibility of the breeding site to predators. The latter is determined by lake levels.     

Compared distribution within a disturbed fishpond ecosystem of breeding ducks and bird species indicators of habitat quality

The distribution of breeding ducks versus three other bird species (Mute Swan Cygnus olor, Black-headed Gull Larus ridibundus and Purple Heron Ardea purpurea) among waterbodies was investigated in the Dombes area, Eastern France, where breeding duck populations have undergone a severe decline following a large-scale transformation of meadow habitat into cropland. Higher Pochard Aythya ferina, Tufted Duck Aythya fuligula, Red-crested Pochard Netta rufina and Gadwall Anas strepera pair densities were recorded in fishponds where Black-headed Gulls were nesting. In these ponds however, nesting success (assessed by the number of broods divided by the number of pairs) was not significantly higher. Similarly, Pochard pair density was higher in ponds with a Purple Heron colony, but brood densities were not. We hypothesise that, in the study region, clutch concentration in the most attractive areas could compensate for the anti-predation effect of gull colonies or overwater nesting in shore vegetation. We could not confirm the expected negative impact of Mute Swan aggressive behaviour on duck distribution. Even though Mallard Anas platyrhynchos pair density was lower in ponds with breeding swans, we did not observe difference for Mallard broods. Moreover, Red-crested Pochard pair density and nesting success were higher in ponds where swans were breeding, probably as a consequence of shared habitat preferences.     

Calanoid copepods from South Georgia,with special reference to size dimorphism within the genus Pseudoboeckella

Summary Three species of calanoid copepods, Boeckella michaelseni, Parabroteas sarsii and Pseudoboeckella poppei were recorded from 6 freshwater localities in the Husvik area, South Georgia. Of the latter species two distinct size morphs occurred, with no overlap in size even in closely situated populations. The large morph was recorded in lakes, the small was found in ponds. The small morph did not coexist with the large predatory P. sarsii, and we suggest predation pressure from this species as the major cause for the observed distribution of these morphs. The pronounced size segregation as well as small morphological dissimilarities suggest that these morphs are reproductively isolated. While the large morphotype corresponds to that of P. poppei, the taxonomic affinities of the small morph are uncertain.     

Multivariate statistical analysis of net diatom species distributions in the Southwestern Atlantic and Indian Ocean

Summary Vertical net haul diatom assemblages from near South Georgia, and from between Africa and Antarctica, were examined and compared. Variation among South Georgia stations was examined by principal component, cluster and canonical discriminant analyses. Diatom distributions provide evidence for at least two distinct water masses. The region north of the island is characterized by neritic, temperate diatoms and by an assemblage with low species diversity. The region south of the island is characterized by oceanic, antarctic species and relatively high species diversity. The regions are most distinct to the west of the island, intergrading east of the island. Within the north-south division, five station groupings were detected on the basis of distribution of dominant net diatoms. By comparing classical species ecological categorizations to results of principal component analysis, a neritic-oceanic factor was identified from net diatom distributions. This factor was common to both areas in spite of the fact that Biscoe and Agulhas collections were from different seasons.