Molecular and morphometric assessment of the taxonomic status of Ectemnorhinus weevil species (Coleoptera: Curculionidae, Entiminae) from the sub-Antarctic Prince Edward Islands

There are long‐standing controversies on the taxonomic status of Ectemnorhinus weevil species occurring on the sub‐Antarctic Prince Edward Islands. Since the two islands that constitute the Prince Edward Islands archipelago (PEIA), Marion Island (MI) and Prince Edward Island (PEI), differ in terms of alien invasive species such as the introduced house mouse Mus musculus and conservation management strategies, it is important to consider inter‐island dynamics when investigating inter‐specific relationships. Using a combined molecular phylogenetic and morphometric approach, we attempted to resolve the taxonomic status of the PEIA Ectemnorhinus weevil species. A COI gene phylogeny was inferred following the genetic characterization of 52 Ectemnorhinus weevils from both islands, and morphometric assessment using a set of 15 linear, external measurements was used to differentiate between the two currently recognized species, Ectemnorhinus similis and Ectemnorhinus marioni. Analyses revealed the presence of two genetically and morphometrically distinct species on PEI, whilst evidence for a single species, comprising diverse genetically discrete populations was found on MI. Based on these results, the species unique to PEI has been designated Ectemnorhinus kuscheli n. sp. whilst we confirm the synonymy between E. similis and E. marioni, the two species originally described from MI. E. kuscheli appears to be restricted to PEI, whereas E. similis occurs on both MI and PEI.     

New records of alien vascular plants from Marion and Prince Edward Islands, sub-Antarctic

A survey was made of the distribution of introduced vascular plants on Marion and Prince Edward Islands. The results of this survey were compared to results of previous surveys (1965/66, 1975, 1981, 1989). Four new introductions to Marion Island have taken place, three of which involved species that had been introduced in the past, but had disappeared or were eradicated. Eighteen species of alien vascular plants are now known from Marion Island. Of these, three were not observed during the present survey, and another three have been eradicated. Many of the naturalised aliens are still increasing markedly in area and/or in numbers. Rates of spread of up to 300 m year⁻¹ occur. Three alien vascular species occur on Prince Edward Island. Two are recent introductions, presumably transported to this island from neighbouring Marion Island by wind or birds. Accepted: 22 November 1998     

Water balance and osmoregulation in weevil larvae (Coleoptera: Curculionidae: Brachycerinae) from three different habitats on sub-antarctic Marion Island

Summary Ectemnorhinine weevils are the most successful group of beetles in the sub-antarctic region, which is undoubtedly due partly to the ability of these weevils to tolerate a wide variety of abiotic conditions. In the laboratory, larvae of three species of ectemnorhinine weevils, from three diverse habitats on Marion Island, were exposed to desiccating conditions and to water of two different salinities to elucidate the physiological basis of their ability to tolerate various abiotic conditions. In the desiccation experiment, the supralittoral Palirhoeus eatoni (C.O. Warerhouse) larvae lost water faster than larvae of the inland epilithic species, Bothrometopus randi Jeannel, and could not fully replenish lost water by drinking. However, larvae of P. eatoni showed greater osmoregulatory ability than the latter species when exposed to hypoand hypcrosmotic conditions. The detritus-dwelling larvae of Ectemnorhinus similis C.O. Waterhouse showed rates of water loss similar to those of the B. randi larvae in the desiccation experiment, but took longer to replace lost water by drinking. All three species showed little change in haemolyrnph water activity despite approximately 28% reduction in water content during desiccation. These physiological responses seem to reflect an equilibrium between the species and their environments which may be considered an adaptation (sensu Coddington 1988) in the case of B. randi, but which appears to be a result of phylogenetic constraint in E. similis. P. eatoni's status as a marine weevil is confirmed.     

The distribution and abundance of white-chinned petrels (Procellaria aequinoctialis) breeding at the sub-Antarctic Prince Edward Islands

The white-chinned petrel (Procellaria aequinoctialis) is the seabird most often killed on longlines in the Southern Ocean and is listed as vulnerable to extinction. We estimated the population breeding at the Prince Edward Islands, the last breeding site for the nominate subspecies that lacks a recent population estimate. White-chinned petrel burrows are largely confined to deep, muddy soils, usually on slopes below 200?m, but locally up to 420?m. After correcting for count bias, Marion Island has an estimated 29,900 nests (95?% CI 27,700–32,400). Burrow occupancy rates at the start of the incubation period were 65?% during one-off surveys, but repeat surveys found that at least 73?% of burrows were occupied and 87?% of burrows showed signs of occupancy. This suggests that there were roughly 24,000 occupied nests on Marion Island (95?% CI 20,000–28,000). A more cursory survey on Prince Edward Island yielded 14,700 burrows, suggesting that there are 9,000–15,000 occupied nests. The nominate subspecies of white-chinned petrel occupies approximately 974,200 nests (95?% CI 678,000–1,286,000), with the Prince Edward Islands, the third most important breeding site, after South Georgia and Kerguelen. Assuming that populations breeding at islands in the Atlantic and Indian Oceans winter in different regions, the impact of fishery bycatch is likely to have had a greater impact on the Indian Ocean population. The Marion Island survey provides a baseline against which future population changes can be assessed.     

Biology and ecology of theDusmoecetes Jeannel (Col. Curculionidae) species complex on Marion Island

Summary TheDusmoecetes species complex on sub-Antarctic Marion Island comprises two species. The larger species,D. similis (C.O. Waterhouse), feeds on angiosperms as adults and detritus as larvae, whereas the smaller species,D. marioni Jeannel feeds on bryophytes in all stages.D. similis has seven larval instars and a generation time of one year or longer.D. marioni has between five and seven larval instars, depending on the plant community it inhabits, and a generation time of one year or less. Immatures ofD. similis have a theoretical null point of development of -0.62°C and aQ ₁₀ of 3.57. In both species there are overlapping generations in the field, although in the case ofD. similis there is a distinct seasonal emergence of adults starting in September. Mean standing crop of larvae on the coastal plain is approximately 5.5 kg (dry mass)·ha^-1, but can be as high as 11.85 kg (dry mass)·ha^-1 inAzorella selago dominated communities. This study indicates that both species are important herbivores and/or detritivores on Marion Island.     

Burrow densities and nest site preferences of petrels (Procellariidae) at the Prince Edwards Islands

Summary The nest-site preferences of six burrowing petrel species, Salvin's prion Pachyptila vittata salvini, blue petrel Halobaena caerulea, great-winged petrel Pterodroma macroptera, Kerguelen petrel Pterodroma brevirostris, soft-plumaged petrel Pterodroma mollis and white-chinned petrel Procellaria aequinoctialis, in the northeastern part of Marion Island (Prince Edward Island group, southern Indian Ocean) were analyzed by step-wise multiple regression. The nest-site characteristics measured were slope angle, soil depth and moisture content, percentage cover by stones or boulders and percentage cover by each of seven major plant species. The major nest-site preferences were: exposed areas with shallow soil (Salvin's prion); steep coastal slopes (blue petrel); sheltered well-drained slopes with deep soil (great-winged petrels); wet areas along drainage lines (Kerguelen petrel); steep slopes (soft-plumaged petrel); and areas with deep soil (white-chinned petrel). Similar species showed no significant avoidance of nest sites where there were burrows of potential competitors but did tend to nest spread out over different habitats. Burrow densities were determined in six habitat and seven vegetation types. Salvin's prion was the most abundant species (81% of burrows, with a maximum density of 279 burrows ha^-1) and used both burrows and natural cavities for nesting. For all species combined, burrow densities at Marion Island were lower than in comparable habitats and vegetation types at neighbouring Prince Edward Island. Depredation by feral house cats Felis catus, absent from Prince Edward Island, is assumed to be largely responsible for this difference.     

The fern genus Elaphoglossum section Lepidoglossa (Dryopteridaceae) in Africa,Macaronesia, the mid‐Atlantic and southern Indian Ocean Islands

Elaphoglossum section Lepidoglossa in Africa, Macaronesia (Azores and Madeira), the mid‐Atlantic Ocean Islands (St Helena, Gough and Tristan da Cunha Island groups) and the southern Indian Ocean Islands (Marion and Prince Edward Islands) is reviewed. Fifteen Elaphoglossum species from this region are ascribed to the section. A new species, Elaphoglossum rivularum , confined to the Chimanimani Mountains in eastern Zimbabwe and formerly ascribed to E. kuhnii from West Africa, is described. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 165 , 20–63.     

Leucistic southern elephant seal at Marion Island

We observed a light coloured female southern elephant seal juvenile (Mirounga leonina) twice at Marion Island in August 2008 and confirmed that it was leucistic rather than albinistic. Though there have been a few previous reports of light-coloured southern elephant seals, this is the first confirmed case of leucism in this species. Judged to be 1-year old, perhaps 2-years old at the most, and because we have not observed any leucistic pups at Marion Island during the past 2 years despite an extensive monitoring and tagging program, we think that this animal was born at nearby Prince Edward Island or perhaps further afield at Îles Crozet.     

New records of Acari from the sub-Antarctic Prince Edward Islands

Sixty species of Acari are recorded from the sub-Antarctic Marion and Prince Edward Islands (the Prince Edward archipelago). Twenty of the 45 species collected on recent expeditions are new and currently undescribed. Other new taxa include a family of Mesostigmata, four new genera, and the first sub-Antarctic records of Cillibidae (Mesostigmata) and Eryngiopus (Prostigmata). Fifteen of the 31 species previously reported from the islands are confirmed, although eight of the previous accounts remain doubtful. The fauna, which shows a distinction between the shoreline and terrestrial components, comprises endemic, South Indian Ocean Province and sub-Antarctic mite species. Accepted: 18 July 1998     

Comparative nutritional ecology of bryophyte and angiosperm feeders in a sub-Antarctic weevil species complex (Coleoptera: Curculionidae)

Abstract.

• 1 Highly productive and st,ructurally diverse angiosperm communities occur on sub-Antarctic Marion Island, yet cryptogams are the main source of energy and nutrients for five of the six native weevil species (Curculionidae: Ectemnorhinini) that occur there.
• 2 Previously it has been hypothesized that low-temperature regimes, during the Pleistocene, precluded angiosperm herbivory. This hypothesis was based, inter alia, on the assumption that at low temperatures feeding on bryophytes is more nutritionally advantageous than feeding on vascular plants.
• 3 This assumption was tested by comparing the consumption rate (CR) and approximate digestibility (AD) (mass and energy) of bryophytes and angiosperms in two Dusmoecetes species indigenous to Marion Island.
• 4 The approximate digestibility of Blepharidophyllum densifolium (Scapaniaceae) energy and dry mass were similar for D.marioni Jeannel adults at 5°C and at 10°C. D.similis (C. O. Waterhouse) adults fed Azorella selago Hook (Apiaceae) leaves also had similar AD for food dry mass and energy at 5°C and at 10°C. However, the performance of D.similis on A.selago leaves and flowers at 5°C was better than that of D.marioni on bryophytes at both temperatures.
• 5 Bryophyte feeding does not appear to be nutritionally more advantageous at low temperatures in the sub-Antarctic, nor does angiosperm herbivory appear to be comparatively disadvantageous at low temperatures, although D.similis does not feed on Acaena magellanica (Lam.) (Rosaceae) at 5°C. It seems likely that moss-feeding evolved in response to an absence of angiosperms during glacial periods, rather than because of a nutritional advantage associated with bryophagy at low temperatures.

     

Do feral house mice have an impact on invertebrate communities on sub‐Antarctic Marion Island?

Abstract House mice (Mus domesticus L.) have been present on sub‐Antarctic Marion Island since the early 1800s. Several authors have suggested that an increase in mice density as a result of a general warming trend in the sub‐Antarctic climate from the 1960s has led to a decline in invertebrate biomass and abundance. These suggestions have been supported by the observation that the invertebrates of nearby mouse‐free Prince Edward Island are apparently larger and more numerous than on Marion. Our experiment was designed to determine whether mice have a direct effect on invertebrate abundance, biomass and community structure, or an effect on the vegetation community and thus potentially an indirect effect on invertebrates. We constructed five wire‐mesh mouse‐free exclosures in one habitat type on Marion Island and recorded both the soil macro‐invertebrate community and the vegetation inside and outside each of the exclosures before the start of the experiment in 1996 and twice thereafter (1998 and 2000). Mice had no significant effect on any of the eight prey groups' abundance or biomass, or on community structure (diversity and composition). Four of the prey groups changed significantly over time in either biomass or abundance, independent of the presence of mice. Our results, which may have been affected by generally low statistical power, suggest that factors other than mice had a larger impact on invertebrates than mice alone.     

Relationship between cover of Chondrus crispus (Gigartinales,Rhodophyta) and Phymatolithon (Corallinales,Rhodophyta) on friable rock substrata

Field observations in sublittoral Prince Edward Island, Canada, indicated that on a friable sandstone substratum Chondrus crispus was more commonly associated with Phymatolithon sp. than with bare rock. Thus, a substantial proportion of the population of Irish moss along the coast of Prince Edward Island occurs on this encrusting coralline. These observation may be explained on the basis of the relative stability of the substratum in contrast to other studies in which sloughing of epithallial cells by species of both Phymatolithon and Lithothamnium has been reported to limit epiphytism by fleshy macrophytes.Issued as NRCC 31426.     

Habitat modelling of tracking data from multiple marine predators identifies important areas in the Southern Indian Ocean

Aim

The distribution of marine predators is driven by the distribution and abundance of their prey; areas preferred by multiple marine predator species should therefore indicate areas of ecological significance. The Southern Ocean supports large populations of seabirds and marine mammals and is undergoing rapid environmental change. The management and conservation of these predators and their environment relies on understanding their distribution and its link with the biophysical environment, as the latter determines the distribution and abundance of prey. We addressed this issue using tracking data from 14 species of marine predators to identify important habitat.

Location

Indian Ocean sector of the Southern Ocean.

Methods

We used tracking data from 538 tag deployments made over a decade at the Subantarctic Prince Edward Islands. For each real track, we simulated a set of pseudo‐tracks that allowed a presence‐availability habitat modelling approach that estimates an animal's habitat preference. Using model ensembles of boosted regression trees and random forests, we modelled these tracks as a response to a set of 17 environmental variables. We combined the resulting species‐specific models to evaluate areas of mean importance.

Results

Real tracking locations covered 39.75 million km², up to 7,813 km from the Prince Edward Islands. Areas of high mean importance were located broadly from the Subtropical Zone to the Polar Frontal Zone in summer and from the Subantarctic to Antarctic Zones in winter. Areas of high mean importance were best predicted by factors including wind speed, sea surface temperature, depth and current speed.

Main conclusions

The models and predictions developed here identify important habitat of marine predators around the Prince Edward Islands and can support the large‐scale conservation and management of Subantarctic ecosystems and the marine predators they sustain. The results also form the basis of future efforts to predict the consequences of environmental change.

     

Littoral Acari of Marion Island: ecology and extreme wave action

Fourteen species of littoral Acari (Arachnida) were collected from the shores of sub-Antarctic Marion Island, of which Parasitiphis brunneus (Kramer) (Ologamasidae), Rhombognathus apsteini Lohmann and R. gressitti Newell (Halacaridae) are new to the Prince Edward Islands. Acari, impoverished both in terms of diversity and abundance, were confined to the few micro-habitats, including rocky-shore lichens, kelp holdfasts, other macroalgae and the surface pitting of mobile boulders, which provided protection from the direct and indirect stresses of severe wave action.     

Recent changes in the seaweed community of Western Prince Edward Island: implications for the seaweed industry

Prior to 1980, seaweed beds of western Prince Edward Island, Canada, were dominated by Chondrus crispus Stackhouse, associated with 37 other species of common algae. Furcellaria lumbricalis (Huds.) Lamour. occurred in 4.6% of the samples from the Pleasant View bed but never reached measurable levels of cover. By 1991 F. lumbricalis was reported in 67% of the samples from this bed. Furcellaria lumbricalis biomass was negatively correlated with C. crispus biomass and positively correlated with Phyllophora Grev. spp. biomass. F. lumbricalis biomass and cover peaked in subtidal areas below 4 m at 359 ± 299 SD fresh g 0.25 m^–2. Harvesters avoid concentrations of F. lumbricalis, resulting in a 5% content of this species in the commercial harvest. Systematic harvesting located concentrations of F. lumbricalis in seven of 10 commercial beds. Proposed causes for change in species dominance from C. crispus to F. lumbricalis range from general environmental change, natural succession to excessive human perturbation.     

Feeding dynamics and respiration of the bottom-dwelling caridean shrimp Nauticaris marionis Bate, 1888 (Crustacea: Decapoda) in the vicinity of Marion Island (Southern Ocean)

The feeding dynamics and oxygen uptake of the bottom-dwelling caridean shrimp Nauticaris marionis were studied during the April/May 1984, 1996 and 1997 cruises to Marion Island (Prince Edward Islands, Southern Ocean). N. marionis is thought to have an opportunistic feeding mode. Prey composition varied considerably between the years and sites investigated. Overall, benthic (mainly hydrozoans and bottom-dwelling polychaetes) and, at times, pelagic (largely euphausiids and copepods) prey items dominated in the stomachs of N. marionis both by occurrence and by volume. Generally, pelagic prey contributed more to the diets of smaller shrimps, while benthic prey was a more important component in the guts of larger specimens. Wet, dry and ash-free dry weight were determined for specimens used in respiration experiments. The respiration rates of N. marionis females with carapace length 6.6–11.1 mm ranged from 80 to 250 μl O₂ individual⁻¹ · h⁻¹, or from 0.588 to 2.756 μl O₂ · mg⁻¹ dry weight h⁻¹. Regression analyses showed highly significant correlations between oxygen consumption and carapace length for N. marionis. Daily ingestion rates estimated using an in situ gut content analysis technique (4.4% of body dry weight) and an energy budget approach (average 4.7% of body dry weight, range 2.0–7.5%) showed good agreement with each other. Accepted: 29 July 1998     

Genetics of the sex ratio anomaly in Drosophila hybrids of the Virilis group

Summary A study was made of the effect of genotype and temperature (25 and 17°C) on sex ratio in the hybrids D. virilis Sturt. X D. littoralis Sokolov. A genetic system has been found controlling sex-differential viability. In the F₁ of the reciprocal hybrids D. virilis X D. littoralis the sex ratio is normal, though at 17°C females are slightly excessive. The abnormal sex ratio is observed only in the progeny of test crosses.The major gene causing the death of female progeny of the cross [ (, D. virilis x , D. littoralis) x D. virilis] x D. littoralis is located on chromosome 2 of D. virilis. It is expressed as a lethal if chromosome 5 is heterogeneous virilis-littoralis. Chromosome 3 of D. virilis bears a modifier-enhancer and chromosome 5, a suppressor, of this lethal found in chromosome 2. This genetic system has a maternal effect and functions at 25°C, interacting with the X-chromosome of D. littoralis. If the maintainance temperature is lowered to 17°C, the progeny of the cross hybrid FB₁ x D. littoralis is predominantly female. Partial death of males is accounted for by a disturbance in the interaction between the genes of X-chromosome in certain combinations with the D. virilis autosomes and the Y-chromosome of the paternal species D. littoralis.Sex-differential mortality in the hybrids D. virilis x D. littoralis is one of the isolating factors between these species which does not appear to act until the second and subsequent F₁ generations due to the formation of the recombination load.     

Foraging parameters of gentoo penguins Pygoscelis papua at Marion Island

Summary We measured the foraging parameters of breeding gentoo penguins Pygoscelis papua at sub-Antarctic Marion Island. Mean swimming speed was 7.9 km h^-1. Penguins spent on average 8.1 h away from the colony if they returned on the same day they left and 23.7 h away if they remained at sea overnight. Sixteen percent of the total time away at sea was spent swimming. Time spent swimming, and consequently distance travelled, during a foraging trip were highly variable and showed significant intercolony differences. However, 80% of all foraging trips totalled less than 40 km. Meal sizes were small and there was no correlation between meal size and distance travelled, suggesting a low availability of food. Prey items in the diet consisted mainly of the benthic shrimp Nauticaris marionis and the demersal fish Notothenia squamifrons. On evidence from stomach contents and the distances the penguins travelled, we suggest that Nauticaris marionis has a more restricted distribution around Marion Island than does Notothenia squamifrons. The concentration of gentoo penguin breeding colonies along the east coast of Marion Island and the south-east coast of Prince Edward Island may be attributable to favourable feeding conditions between the two islands.     

Production and standing stocks of the kelp Macrocystis laevis Hay at the Prince Edward Islands,Subantarctic

Summary The recently described species Macrocystis laevis Hay is endemic to the Prince Edward Islands. Aerial photographs of Marion Island were used to outline the distribution of the kelp and to assess its cover. M. laevis occurs along the lee shore of the island, between the 5 and 20 m isobaths. Plant densities and gross plant morphology were measured by divers during April/May 1988. Net production was estimated from growth measurements taken in April/May 1988 and 1989 and again during August 1989. The mean biomass of kelp was 0.67 kgC·m^–2 within the kelp beds. Net production was estimated at 7.7 gC·m^–2·d^–1 and 11.5 gC·m^–2d^–1 during the months of April and August respectively. M. laevis had a uniform frond-length frequency distribution, which suggests that only the oldest fronds are lost by wave action or senescence. Based on calculations for M. laevis and Durvillaea antarctica (the two species making up most of the macrophyte biomass) macrophytes are more productive per unit area than the phytoplankton but contribute less to the seas around the Prince Edward Islands by virtue of their small spatial coverage. Neither of the kelps lose much material as particulate or dissolved organic carbon through fragmentation. The extent of grazing on live M. laevis fronds is unknown, and only D. antarctica contributes to a macrofaunal detrital community. The contribution of M. laevis production to the nearshore ecology of the islands seems limited, as we suspect that almost all of its production is exported to the open ocean pelagic system.     

Diatom communities from the sub-Antarctic Prince Edward Islands: diversity and distribution patterns

During an extensive survey of the freshwater and moss-inhabiting diatoms of the Prince Edward Islands, a total of 214 taxa belonging to 60 genera were found. Three main communities can be found on the two islands. A large part of the samples was grouped into an aquatic group, bringing together all samples from lentic and lotic waterbodies. A second, contrasting, group was formed by all dry samples whereas in a third group all habitats with higher mineral contents were found. The habitats differed clearly in taxa composition reflecting that way possible environmental differences. Although the diatom composition between the two islands of this island group (Marion and Prince Edward Island) showed some minor qualitative differences, no marked quantitative differences have been observed. The diatom flora shows a distinct similarity with the other islands in the southern Indian Ocean, such as the Crozet archipelago and the Kerguelen Islands forming a biogeographical entity in this part of the ocean, distinctly separated from the non-marine diatom flora in other parts of the (sub-)Antarctic Region.