RAPD analysis of genetic variation and dispersal of the moss Bryum argenteum in Ross Island and Victoria Land, Antarctica

The Random Amplified Polymorphic DNA technique was used to assess the level of genetic diversity in Bryum argenteum from Ross Island and southern Victoria Land, Antarctica. Samples were collected from three separate transects, and from other geographically distinct populations within 150 km of Ross Island. Moss growth in two transects, sampled down small exposed meltstream channels at Cape Royds and Cape Chocolate, was very sparse with no other moss colonies found within 0.4 or 4 km, respectively. However, samples from these channels showed similar levels of genetic variation to those from a transect at Granite Harbour, where moss colonies were large, luxuriant and turf-like between boulders. In all transects, high levels of genetic diversity were apparent both within and between colonies, and some spatial relationships were observed down the length of the channels, with more extensive variation at the top than the bottom of two transects. Samples from other sites in the region showed varying but high levels of genetic diversity; overall, the majority showed some clustering according to site of collection, with short-distance dispersal of propagules by water and transmission between sites presumably by wind. The extensive genetic diversity observed appears mainly due to somatic mutation within colonies, with some contribution by immigration of propagules from elsewhere into established colonies. Accepted: 10 January 1999     

RAPD analysis of genetic variation and dispersal of the moss Bryum pseudotriquetrum from Southern Victoria Land, Antarctica

The RAPD technique (Random Amplified Polymorphic DNA) was used to assess the level of genetic diversity in Bryum pseudotriquetrum from Southern Victoria Land, Antarctica. Isolates were collected from two transects, and from several other geographically distinct populations within 150 km of Ross Island. Moss growth in one transect, sampled down a small exposed meltstream channel at Cape Chocolate, was very sparse with no other moss colonies found within several hundred meters. Isolates from this transect showed low levels of genetic variation, with many moss clumps appearing identical; these were probably dispersed by water along the channel. In another transect analysed from Granite Harbour, the moss colonies were large, luxuriant and protected by boulders. These isolates showed considerably higher levels of genetic variability than the Cape Chocolate samples, and both within- and between-clump variation was observed. Samples from other sites showed varying levels of genetic diversity. It appears from these results that the degree of protection from the harsh Antarctic environment can influence not only the type of moss growth, but also the level of genetic diversity. Evidence is presented for both short-distance dispersal by water and long-distance dispersal by wind. Received: 29 December 1997 / Accepted: 10 April 1998     

Antarctic terrestrial ecosystems: The Vestfold Hills in context

Antarctic terrestrial ecosystems are briefly described, with emphasis on Signy Island in the maritime antarctic region, and the McMurdo oasis, southern Victoria Land, and Vestfold Hills in the continental antarctic region.As the largest and best known coastal ice-free oasis, the Vestfold Hills contain excellent examples of terrestrial sublithic, epilithic, chasmoendolithic, epiphytic and terricolous algal communities, as well as epilithic, endolithic, and epiphytic lichen communities, and moss communities. Many of the numerous lakes support dense communities of aquatic algae.     

Daphniopsis studeri (Crustacea: Cladocera) in lakes of the Vestfold Hills,Antarctica

Summary The adult sizes and reproductive capabilities of populations of the cladoceran Daphniopsis studeri Rühe from freshwater and slightly saline lakes in the Vestfold Hills, Princess Elizabeth Land were monitored during December, 1990. The population of Crooked Lake was studied in detail from July 1990–March 1991. Limited samples were also obtained from Heard Island (sub Antarctic). Obligate parthenogenesis involving the production of subitaneous eggs appears to be the case. No males occurred. The overwintering populations of continental Antarctica consist mainly of adult females containing extensive fat reserves. The main reproductive effort occurs in spring. some females produce a smaller second brood during the summer. Reproductive output increases with adult size which is related to the nutrient status of the lake and its productivity. The Heard Island populations have a higher weight to length ratio than the Vestfold populations and have a much greater reproductive output.     

Genetic diversity in the moss Hennediella heimii in Miers Valley, southern Victoria Land, Antarctica

The moss Hennediella heimii constitutes a significant proportion of the terrestrial flora of East Antarctica, especially in the McMurdo Dry Valleys region of southern Victoria Land. This is the first investigation of the extent of genetic variation within a population of H. heimii. Random Amplified Polymorphic DNA has been used to study both genetic diversity and dispersal of this moss in Miers Valley, southern Victoria Land. The results showed that genetic variation does occur in H. heimii (possibly due to increased exposure to UV-B irradiation), even between shoots within single colonies, and that colonies collected from three transects along meltstreams within the valley constitute a single large population. However, comparison with samples of the same species from nearby valleys and sites up to 500 km distant showed that the Miers Valley population is distinct from these other populations. The results also indicate that wind plays a major role in dispersal of H. heimii in this region of Antarctica. Accepted: 2 September 1998     

RAPD profiling of genetic diversity in two populations of the moss Ceratodon purpureus in Victoria Land, Antarctica

Isolates of the moss Ceratodon purpureus were collected down a channel formed by a meltstream waterfall at Granite Harbour in Southern Victoria Land, Antarctica. The RAPD technique was used to analyse the extent of genetic variation within clumps, between clumps, and between this population and specimens of the same species from two other areas in Antarctica (one a few hundred metres away, the other at Edmonson Point, 300 km further north) and from Sydney, Australia. Genetic variation was detected within and among clumps, with some spatial structure to the population within the channel. Isolates from the nearby location were quite closely related, whereas those from Edmonson Point formed an outgroup on a phylogenetic tree of relatedness. Received: 10 June 1997 / Accepted: 30 September 1997     

High levels of intraspecific genetic divergences revealed for Antarctic springtails: evidence for small‐scale isolation during Pleistocene glaciation

We examined levels of genetic variability within and among populations of three Antarctic springtail species (Arthropoda: Collembola) and tested the hypothesis that genetic divergences occur among glacially‐isolated habitats. The study was conducted in southern Victoria Land, Ross Dependency, Antarctica, and samples were collected from locations in the vicinity of the Mackay Glacier. We analyzed mtDNA (cytochrome c oxidase subunit I; COI) sequence variability for 97 individuals representing three species (Gomphiocephalus hodgsoni, N = 67; Cryptopygus nivicolus, N = 20; and Antarcticinella monoculata, N = 8). Haplotype diversity and genetic divergences were calculated and used to indicate population variability and also to infer divergence times of isolated populations using molecular clock estimates. Two of the three species showed high levels of genetic divergence. Gomphiocephalus hodgsoni, a widespread and common species, showed 7.6% sequence divergence on opposite sides of the Mackay Glacier. The more range restricted C. nivicolus showed 4.0% divergence among populations. The third species, A. monoculata, was found in only one location. Molecular clock estimates based on sequence divergences suggest that populations separated within the last 4 Mya. We conclude that habitat fragmentation resulting from Pliocene (5 Mya) and Pleistocene (2 Mya to 10 Kya) glaciations has promoted and maintained high levels of diversity among isolated springtail populations on relatively small spatial scales. The region surrounding the Mackay Glacier is likely to have provided refugia for springtail populations during glacial maxima and remains an area of high genetic and species diversity for Collembola within the Ross Sea region.     

Variation in the ribosomal ITS-sequence of the lichens Buellia frigida and Xanthoria elegans from the Vestfold Hills,eastern Antarctica

Abstract:Thalli of the lichens Buellia frigida and Xanthoria elegans were collected from five different locations each 5–15 km apart in the Vestfold Hills, Princess Elizabeth Land, eastern Antarctica. A further collection was made from Mawson Station, Mac Robertson Land, eastern Antarctica, 660 km away. DNA was extracted from whole thalli and the ribosomal ITS region amplified by PCR using fungal specific primers. Resulting products were sequenced to gain an indication of whether or not variation was present within populations of lichen-forming fungi from continental Antarctica, and therefore of the availability of genetic resources to react to pressures such as climate change. Three genotypes ofB. frigida and two of X. elegans were detected in the Vestfold Hill collections. However, these differed by only one nucleotide position suggesting the presence of relatively little genetic variation, if the ITS region is indicative of the overall genome. Buellia frigida collected from Mawson Station had an identical ITS region sequence to the most common Vestfold Hills genotype, indicating that this species may have a low level of genetic variation across much of eastern Antarctica. In contrast, X. elegans collected from Mawson showed considerable genetic variation from the Vestfolds thalli, differing at 14·2% of nucleotide positions and had an identical ITS region sequence to an isolate from maritime Antarctica 4960 km away. Samples from the Vestfold Hills formed a distinct cluster in a phylogenetic analysis of ITS sequences from a worldwide collection of X. elegans isolates.     

Decadal changes in habitat characteristics influence population trajectories of southern elephant seals

Understanding divergent biological responses to climate change is important for predicting ecosystem level consequences. We use species habitat models to predict the winter foraging habitats of female southern elephant seals and investigate how changes in environmental variables within these habitats may be related to observed decreases in the Macquarie Island population. There were three main groups of seals that specialized in different ocean realms (the sub‐Antarctic, the Ross Sea and the Victoria Land Coast). The physical and climate attributes (e.g. wind strength, sea surface height, ocean current strength) varied amongst the realms and also displayed different temporal trends over the last two to four decades. Most notably, sea ice extent increased on average in the Victoria Land realm while it decreased overall in the Ross Sea realm. Using a species distribution model relating mean residence times (time spent in each 50 × 50 km grid cell) to 9 climate and physical co‐variates, we developed spatial predictions of residence time to identify the core regions used by the seals across the Southern Ocean from 120°E to 120°W. Population size at Macquarie Island was negatively correlated with ice concentration within the core habitat of seals using the Victoria Land Coast and the Ross Sea. Sea ice extent and concentration is predicted to continue to change in the Southern Ocean, having unknown consequences for the biota of the region. The proportion of Macquarie Island females (40%) utilizing the relatively stable sub‐Antarctic region, may buffer this population against longer‐term regional changes in habitat quality, but the Macquarie Island population has persistently decreased (?1.45% per annum) over seven decades indicating that environmental changes in the Antarctic are acting on the remaining 60% of the population to impose a long‐term population decline in a top Southern Ocean predator.     

Genetic diversity in Orobanche crenata populations from southern Spain

The pattern of genetic variation within and among natural populations of broomrape (Orobanche crenata Forsk.) from southern Spain was analysed by RAPD markers. Hierarchical analysis of phenotypic diversity using AMOVA was performed to analyse the partitioning of the variation among populations and among individuals. Although most of the genetic diversity was attributable to differences among individuals within a population (94.29%), significant φ_st values among populations suggested the existence of phenotypic differentiation. Moreover, corresponding HOMOVA analysis revealed that molecular variances were significantly heterogeneous among populations although no clear grouping pattern could be established. These results are to be expected considering the predominant outcrossing behaviour of O. crenata. Received: 10 January 2001 / Accepted: 12 February 2001     

East–west genetic differentiation in Musk Ducks (<Emphasis Type="Italic">Biziura lobata</Emphasis>) of Australia suggests late Pleistocene divergence at the Nullarbor Plain

Musk Ducks (Biziura lobata) are endemic to Australia and occur as two geographically isolated populations separated by the Nullarbor Plain, a vast arid region in southern Australia. We studied genetic variation in Musk Duck populations at coarse (eastern versus western Australia) and fine scales (four sites within eastern Australia). We found significant genetic structure between eastern and western Australia in the mtDNA control region (Φ_ST = 0.747), one nuclear intron (Φ_ST = 0.193) and eight microsatellite loci (F_ST = 0.035). In contrast, there was little genetic structure between Kangaroo Island and adjacent mainland regions within eastern Australia. One small population of Musk Ducks in Victoria (Lake Wendouree) differed from both Kangaroo Island and the remainder of mainland eastern Australia, possibly due to genetic drift exacerbated by inbreeding and small population size. The observed low pairwise distance between the eastern and western mtDNA lineages (0.36%) suggests that they diverged near the end of the Pleistocene, a period characterised by frequent shifts between wet and arid conditions in central Australia. Our genetic results corroborate the display call divergence and Mathews’ (Austral Avian Record 2:83–107, 1914) subspecies classification, and confirm that eastern and western populations of Musk Duck are currently isolated from each other.     

GENETIC VARIABILITY AND POTENTIAL SOURCES OF GRATELOUPIA DORYPHORA (HALYMENIACEAE,RHODOPHYTA), AN INVASIVE SPECIES IN RHODE ISLAND WATERS (USA)1

Grateloupia doryphora (Montagne) M.Howe is an invasive foliose alga that was reported for the first time in Rhode Island, USA in 1997. The population has since increased in size and expanded in range. In this study, the genetic variation and potential sources of the Rhode Island G. doryphora population were examined using three types of molecular markers: randomly amplified polymorphic DNA (RAPD), nuclear internal transcribed spacer (ITS) sequences, and mitochondrial cox2–cox3 intergenic spacer (COX) sequences. No variation was detected in ITS or COX sequences among Rhode Island G. doryphora individuals. RAPDs, however, did reveal genetic variation, although banding patterns were similar, with RAPD genetic distances between individuals ranging from 0.00 to 0.17. The low level of genetic diversity observed within the Rhode Island population may be due to a small founder population or a founder population derived from a genetically uniform source. To identify possible sources of the Rhode Island invasion, individuals from nine geographically diverse populations of foliose Grateloupia were compared. Phylogenetic trees inferred from RAPD distances and ITS and COX sequences had similar topologies; thus there was phylogenetic congruence among these independent loci. The Rhode Island G. doryphora specimens were genetically similar to specimens from G. doryphora populations located in Portsmouth, England; Tholen Island, The Netherlands; and Brittany and Hérault, France. Interestingly, the G. doryphora population in each of these locations is itself due to an introduction event within the past 40 years.     

Mummified and skeletal southern elephant seals (Mirounga leonina) from the Victoria Land Coast,Ross Sea,Antarctica

We report on an accumulation of mummified southern elephant seals (Mirounga leonina) from Inexpressible Island on the Victoria Land Coast (VLC), western Ross Sea, Antarctica. This accumulation is unusual, as elephant seals typically breed and molt on sub‐Antarctic islands further north and do not currently occupy the VLC. Prior ancient DNA analyses revealed that these seals were part of a large, Antarctic breeding population that crashed ~1,000 yr ago. Radiocarbon dates for Inexpressible Island mummies range from 380 to 3,270 yr before present, too old to have been created by Scott's Northern Party in 1912 and varying too widely in age to represent a catastrophic death assemblage. Skeletal measurements reveal that most Inexpressible Island mummies are adult or subadult males. The presence of male elephant seals on Inexpressible Island until several hundred years ago suggests that, at a minimum, it served as a haul‐out site for the large Antarctic population and may have hosted a breeding colony. The conditions that allowed this Antarctic population to use the Ross Sea, the factors spurring its decline, and the implications for the adaptability and sensitivity of the species to environmental change all merit further study.     

Genetic diversity and dispersal of the moss Sarconeurum glaciale on Ross Island, East Antarctica

The extent of genetic variation and dispersal mechanisms were investigated over short distances of 1–100 m, and up to 3 km, by the random amplified polymorphic DNA (RAPD) technique, for the moss Sarconeurum glaciale , at three locations on Ross Island, Antarctica. At Arrival Heights, genetic variation occurred within single colonies, and the relationships between clumps indicated that they were dispersed down small, meltwater drainage channels by water. The genetic similarities between the colonies from Arrival Heights and others from Scott Base and Crater Hill, a few km away, together with the prevailing wind direction and absence of this moss in the intervening snow-covered area, suggested longer-distance dispersal by wind. Overall, the Ross Island samples appeared to form a single, polymorphic population that was distinct from another population at Canada Glacier, 110 km distant. Somatic mutation, rather than immigration of genetically different propagules from elsewhere, appeared to be the most probable cause of genetic variability in these haploid, vegetatively reproducing Antarctic moss populations. Initiation of recolonization of S. glaciale across a dirt track at Arrival Heights was also investigated by RAPDs, to investigate how regrowth of mosses in disturbed areas occurred in the extreme environment of Antarctica.     

Molecular markers reveal little genetic differentiation among Aconitum noveboracense and A. columbianum (Ranunculaceae) populations

Aconitum noveboracense, a rare, herbaceous perennial, is restricted to recently unglaciated areas in Iowa, Wisconsin, Ohio, and New York, and federally classified as a threatened species. These populations may be disjuncts of the common congener, A. columbianum Nutt., which occurs in the mountains of the western United States. Morphological characters do not reliably separate these taxa. The identity of Black Hills populations, located between the ranges of the rare and common species, is also uncertain. We characterized genetic variation within and among the Aconitum populations in question using isozymes and randomly amplified polymorphic DNA (RAPDs). Isozymes indicate a high degree of similarity among all populations and a high level of genetic diversity in Black Hills populations. Of 97 scorable RAPD loci, 89.7% are polymorphic and clearly resolve most populations. Like isozymes, RAPDs indicate high levels of genetic diversity in the Black Hills and very strong similarity of these populations to A. columbianum from the Bighorn Mountains. Aconitum noveboracense populations show >80% similarity to A. columbianum populations. A population of A. uncinatum from Ohio shows the greatest differentiation from other populations. Therefore, both isozyme and RAPD data concur with the recent treatment of A. noveboracense and A. columbianum as a single species.     

High levels of genetic variability in the moss Ceratodon purpureus from continental Antarctica, subantarctic Heard and Macquarie Islands, and Australasia

The random amplified polymorphic DNA (RAPD) technique, and DNA sequencing of the conserved nuclear ribosomal DNA internal transcribed spacer region (ITS1-5.8S-ITS2), have been used to assess levels of genetic diversity in the moss Ceratodon purpureus from several locations in Australasia, subantarctic Heard and Macquarie Islands, and continental Antarctica. Populations from Heard and Macquarie Islands and from Antarctica maintain high levels of genetic variation. Both within- and among-colony variation were observed at these locations. DNA sequence analysis showed that samples from the Ross Sea region of Antarctica were most closely related to colonies from Casey and Macquarie Island, and that one colony from Heard Island was most closely related to one from Europe. DNA sequence data separated two Australian populations from the Antarctic and subantarctic group on a dendrogram. Detailed RAPD analysis of a single colony from continental Antarctica demonstrated that mutation probably causes the high variability observed in this moss. DNA sequencing and RAPD analysis are complementary techniques for genetic investigation of Antarctic moss populations.Jenny Ninham was an integral part of this research team for several years. Unfortunately she did not live to see these results published.     

Phylogeography of the New Zealand blue duck (<Emphasis Type="Italic">Hymenolaimus malacorhynchos</Emphasis>): implications for translocation and species recovery

Translocation of individuals among extant populations is an important tool in species conservation that allows managers to supplement dwindling populations and potentially alleviate the deleterious effects of inbreeding. Ideal translocation strategy should consider historical relationships among existing populations to avoid potential disruption of population subdivision and local adaptation. Here, we examine mitochondrial sequence variation in the endangered blue duck Hymenolaimus malacorhynchos, a New Zealand endemic riverine specialist, to facilitate informed decision making in future translocations. Behavioural observations suggest that blue duck dispersal is limited and may result in genetic structure within and between regional populations. We analysed 894 base pairs of mitochondrial control region in 78 adult blue ducks sampled from 11 river catchments across the species’ range (representing four regions in the North Island and three regions in the South Island) and found strong and significant genetic structure both within and among islands. These results, combined with a 2.0% sequence divergence between islands, indicates that North Island and South Island blue ducks should be treated as separate management units. The relationship between genetic differentiation and geographic distance for blue ducks on the South Island conformed to an “isolation by distance” pattern. Overall, we recommend that translocations of blue ducks should not be made between the North and the South Islands and those within each island should be restricted to neighbouring catchments.     

An apparent population decrease,or change in distribution,of Weddell seals along the Victoria Land coast

Ground counts during 1959–1968 compared with counts using high resolution (0.6 m²) satellite imagery during 2008–2012 indicated many fewer Weddell seals (Leptonychotes weddellii) at two major molting areas in the western Ross Sea: Edisto Inlet‐Moubray Bay, northern Victoria Land, and McMurdo Sound, southern Victoria Land. Breeding seals have largely disappeared from Edisto‐Moubray, though the breeding population in McMurdo Sound appears to have recovered from harvest in the 1960s. The timing of decline, or perhaps spreading (lower numbers of seals in more places), is unknown but appears unrelated to changes in sea ice conditions. We analyzed both historic and satellite‐derived ice data confirming a large expansion of pack ice mostly offshore of the Ross Sea, and not over the continental shelf (main Weddell seal habitat), and a thinning of fast ice along Victoria Land (conceivably beneficial to seals). Timing of fast ice presence and extent in coves and bays along Victoria Land, remains the same. The reduction in numbers is consistent with an altered food web, the reasons for which are complex. In the context of a recent industrial fishery targeting a seal prey species, a large‐scale seal monitoring program is required to increase understanding of seal population changes.     

Rapid Response of a Marine Mammal Species to Holocene Climate and Habitat Change

Environmental change drives demographic and evolutionary processes that determine diversity within and among species. Tracking these processes during periods of change reveals mechanisms for the establishment of populations and provides predictive data on response to potential future impacts, including those caused by anthropogenic climate change. Here we show how a highly mobile marine species responded to the gain and loss of new breeding habitat. Southern elephant seal, Mirounga leonina, remains were found along the Victoria Land Coast (VLC) in the Ross Sea, Antarctica, 2,500 km from the nearest extant breeding site on Macquarie Island (MQ). This habitat was released after retreat of the grounded ice sheet in the Ross Sea Embayment 7,500–8,000 cal YBP, and is within the range of modern foraging excursions from the MQ colony. Using ancient mtDNA and coalescent models, we tracked the population dynamics of the now extinct VLC colony and the connectivity between this and extant breeding sites. We found a clear expansion signal in the VLC population ~8,000 YBP, followed by directional migration away from VLC and the loss of diversity at ~1,000 YBP, when sea ice is thought to have expanded. Our data suggest that VLC seals came initially from MQ and that some returned there once the VLC habitat was lost, ~7,000 years later. We track the founder-extinction dynamics of a population from inception to extinction in the context of Holocene climate change and present evidence that an unexpectedly diverse, differentiated breeding population was founded from a distant source population soon after habitat became available.     

Randomly Amplified Polymorphic DNA Variation in Populations of Eastern Australian Koalas, Phascolarctos cinereus

Randomly amplified polymorphic DNA (RAPD) variation in populations of the koala, Phascolarctos cinereus, was investigated, revealing significant differences in the level of diversity between southern and northern regions of eastern Australia. Of the 20 polymorphic RAPD markers identified in koalas, 4-7 were polymorphic in southern populations, while 12-17 were polymorphic in northern populations. Analysis of molecular variance revealed a significant difference in the estimated variance between koalas from northern and those from southern regions (P < 0.001), where populations from the north were greater than twice as variable as their southern cousins. The total genetic diversity observed was attributed to regional differences (30.91%), population differences within a region (11.77%), and differences among individuals within a population (57.32%). For the within-region analyses, a large proportion of the genetic diversity was attributable to individual differences within a population, 80.34% for the north and 91.23% for the south. These results demonstrate that RAPD markers are useful for determining population structure among koalas.