Patterns of scleractinian coral recruitment at Lord Howe Island,an isolated subtropical reef off eastern Australia

Changing oceanic conditions, particularly ocean warming and altered currents, can affect the reproductive success of corals. Improving the knowledge of coral reproductive processes at the marginal range limits of coral reefs is important for understanding the ecology of subtropical coral communities and the potential for coral species to expand their ranges in higher latitudes in the future. The extent of live coral cover around subtropical Lord Howe Island (LHI; 31°33′S, 159°05′E) approximately 600 km off the east coast of Australia, has been relatively stable over the last several decades; however, shifts in dominant species in the adult coral community have been reported. To examine the potential influences of recent altered currents and shifts in dominant scleractinian taxa within this community, this study examined spatial and seasonal variation of coral larval settlement at different habitats within the LHI reef lagoon. The study also assessed whether the assemblage of scleractinian corals settling at LHI has changed between 1990–1991 and 2011–2012. Mean densities of coral settlement in 2011–2012 (230 spat m^?2 yr^?1) were consistent with those reported in 1990–1991 and in other regions. However, changes in taxonomic composition were apparent with increases in the proportion of Acroporidae spat at some sites. Settlement of all taxa was highest over summer months, whereas during winter only one coral spat (Pocilloporidae) was detected. Coral settlement was highest and most taxonomically diverse at sites closest to the reef crest, where mortality of settled spat was also greatest. Rates of settlement were high compared with juvenile densities; hence, post-settlement mortality is also likely to be high. Post-settlement processes, influenced by local environmental conditions, are likely to be very important in structuring the adult coral communities within the LHI reef lagoon.     

Catastrophic disturbance and vegetation on Little Slope,Lord Howe Island

Little Slope is a series of debris avalanche deposits below basalt cliffs 700 m high at the southern end of Lord Howe Island (31°35′S 159°05′E). There are five distinct physiographic areas on the slope, each separated by sharp boundaries which mostly correspond to boundaries between features on the cliffs above. The physiography is a consequence of a series of landslides of different, but unknown, ages. A model of the physiographic history is presented. Each physiographic area supports a different vegetation community, also separated by sharp boundaries. The present structure of two communities, Melaleuca howeana scrub and Howea forsterana forest, is a consequence of damage by feral animals. Melaleuca scrub has replaced Cyperus lucidus sedgeland destroyed by goats (Capra hircus) browsing from 1914 until their extermination in 1955. Howea forest has a markedly unimodal age distribution with very few small individuals of the dominant palms. This is a result of the combined effects of browsing by goats on small palms, and seed predation by black rats (Rattus rattus) from the 1920s, preventing regeneration. Unless rat numbers are periodically reduced to reduce seed predation, regeneration may be insufficient to guarantee long-term survival of the forest.     

Reassembling island ecosystems: the case of Lord Howe Island

Exotic species that invade remote islands, usually following human settlement, have had catastrophic effects on native biota. However, on islands it is increasingly feasible to eradicate key exotic species allowing extant native species to recover in situ or to return naturally. The practice of marooning threatened species on islands where the threat is absent, irrespective of whether the threatened species once occurred on the island, is well established. However, less focus has been given to the 'island' as the management unit on which to return extirpated species or related surrogates for extinct species. We use the example of Lord Howe Island as a case study to explore options for island restoration should the remaining critical exotic pests (rodents and perhaps owls in this case) be eradicated as planned. Lord Howe Island, in the south-west Pacific Ocean, is remote, biologically diverse, has a high degree of endemism, and was only discovered by humans in 1778. Consequently, the original and exotic biota and their interactions are all better known than for many islands with a more ancient human history. Two species of plants, nine terrestrial birds, one bat and at least four invertebrates have been lost from the island since 1778. One plant and two invertebrates could be returned as conspecifics. One plant and all the terrestrial birds that are extinct could be replaced by closely related species from elsewhere in the Pacific Ocean. Decisions on replacing extinct species with surrogates should be based on the taxonomic relatedness of the candidates for reintroduction: the same species before subspecies before genera, with functional replacement being a further filter on candidates that are not the same species. In our opinion, taxa with functional equivalence but without taxonomic relatedness would not be acceptable candidates for reintroduction.     

The distribution of intra-genomically variable dinoflagellate symbionts at Lord Howe Island,Australia

The symbiotic dinoflagellates of corals and other marine invertebrates (Symbiodinium) are essential to the development of shallow-water coral reefs. This genus contains considerable genetic diversity and a corresponding range of physiological and ecological traits. Most genetic variation arises through the accumulation of somatic mutations that arise during asexual reproduction. Yet growing evidence suggests that occasional sexual reproductive events also occur within, and perhaps between, Symbiodinium lineages, further contributing to the pool of genetic variation available for evolutionary adaptation. Intra-genomic variation can therefore arise from both sexual and asexual reproductive processes, making it difficult to discern its underlying causes and consequences. We used quantitative PCR targeting the ITS2 locus to estimate proportions of genetically homogeneous symbionts and intra-genomically variable Symbiodinium (IGV Symbiodinium) in the reef-building coral Pocillopora damicornis at Lord Howe Island, Australia. We then sampled colonies through time and at a variety of spatial scales to find out whether the distribution of these symbionts followed patterns consistent with niche partitioning. Estimated ratios of homogeneous to IGV Symbiodinium varied between colonies within sites (metres to tens of metres) and between sites separated by hundreds to thousands of metres, but remained stable within colonies through time. Symbiont ratios followed a temperature gradient, with the local thermal maximum emerging as a negative predictor for the estimated proportional abundance of IGV Symbiodinium. While this pattern may result from fine-scale spatial population structure, it is consistent with an increased susceptibility to thermal stress, suggesting that the evolutionary processes that generate IGV (such as inter-lineage recombination and the accumulation of somatic mutations at the ITS2 locus) may have important implications for the fitness of the symbiont and that of the coral host.     

Distribution of Acanthaster planci at Lord Howe Island,the southern-most Indo-Pacific reef

Lord Howe Island, at 31°33S, supports the southern-most coral reef in the Indo-Pacific region, located approximately 150 and 200 km south of Elizabeth and Middleton Reefs and 1000 km south of the Great Barrier Reef (GBR). Systematic SCUBA searches in 1987 indicated that Acanthaster planci was present at 3 of 10 sites surveyed, at densities of up to 5 individuals ha^-1. Further surveys in 1989 indicated that the population was increasing, with densities of 20–46 ha^-1 recorded from 7 of 13 sites. The size structures of the 1987 and 1989 populations were suggestive of annual recruitment since 1985. Individuals larger than 25 cm diameter were gravid during both surveys, raising the possibility that the population may be self-seeding. Alternatively, the population may be maintained by larvae dispersed in the East Australian Current from the southern GBR or in eddies from Elizabeth and Middleton Reefs. This study provides the first records for distribution of 7 species of scleractinian coral at Lord Howe Is. Reef.     

Extreme convergence in stick insect evolution: phylogenetic placement of the Lord Howe Island tree lobster

The ‘tree lobsters’ are an enigmatic group of robust, ground-dwelling stick insects (order Phasmatodea) from the subfamily Eurycanthinae, distributed in New Guinea, New Caledonia and associated islands. Its most famous member is the Lord Howe Island stick insect Dryococelus australis (Montrouzier), which was believed to have become extinct but was rediscovered in 2001 and is considered to be one of the rarest insects in the world. To resolve the evolutionary position of Dryococelus, we constructed a phylogeny from approximately 2.4 kb of mitochondrial and nuclear sequence data from representatives of all major phasmatodean lineages. Our data placed Dryococelus and the New Caledonian tree lobsters outside the New Guinean Eurycanthinae as members of an unrelated Australasian stick insect clade, the Lanceocercata. These results suggest a convergent origin of the ‘tree lobster’ body form. Our reanalysis of tree lobster characters provides additional support for our hypothesis of convergent evolution. We conclude that the phenotypic traits leading to the traditional classification are convergent adaptations to ground-living behaviour. Our molecular dating analyses indicate an ancient divergence (more than 22 Myr ago) between Dryococelus and its Australian relatives. Hence, Dryococelus represents a long-standing separate evolutionary lineage within the stick insects and must be regarded as a key taxon to protect with respect to phasmatodean diversity.     

The effect of feral goats (Capra hircus L.) on the vegetation of Lord Howe Island

The conflicting but informative literature relating to goats on Lord Howe Island (31° 35’5 159° 05’ E) is reviewed. Observations made in 1970–72 indicate that the effects of goats are localized. Invasion of goat camps by naturalized plants is widespread. Changes attributable to goats are considered and one well documented example is discussed in detail. The effects of goats and pigs are compared. Goats occupy different but overlapping habitats from pigs. A total of 228 goats was shot in an extermination programme. Overall density is 0·17 goats/ha but local densities may vary from 0·56 goats/ha to 26·34 goats/ha. Rumen content analyses indicate that goats are both selective and individualistic feeders. Naturalized plants are eaten in the same proportion as they occur in the flora. The relationship between naturalized weeds and goats appears to be commensal.     

A new genus of apterous scelionid from Lord Howe Island (Hymenoptera; Scelionidae)

Abstract. Psyllobaeus pecki gen. and sp.n., is described from Lord Howe Island, Australia. This genus is unique in the Baeini in that both sexes (not just the female) are apterous, have a sessile metasoma and have a pair of long spines on the apex of the hind femur. The relationships of Psyllobaeus and its biology are discussed.     

Comparison of seedling recruitment under arborescent palms in two Neotropical forests

Certain overlying strata in forests may disproportionately reduce seedling density and species richness. For eight arborescent palm species, we quantified the relative restriction of seedling recruitment under individual palms versus non-palm sites and extended to the landscape scale by quantifying the total area covered by arborescent palms at Barro Colorado Island (BCI), Panama and La Selva Biological Station, Costa Rica. We also examined whether differences among palm species in restricting seedling recruitment were associated with differences in crown architecture, litter depth, and light availability. Woody seedlings had lower mean density/m² and mean number of species/m² under individual palms than at non-palm sites for all four palm species at BCI, but for none at La Selva. Estimated species richness for woody seedlings, derived via rarefaction, was lower under palm than non-palm microsites at both BCI and La Selva, but not for non-woody seedlings. Differences in seedling density corresponded to some key architectural characters that differed among the palm species. Light availability was lower under palm than non-palm microsites at both BCI and La Selva, but only estimated species richness of woody seedlings at BCI was strongly correlated with % canopy openness. The coverage of arborescent palms was much lower at BCI than La Selva. Therefore, at BCI, the relative restriction of woody seedling recruitment under individual palms does not accumulate greatly at the landscape scale. At La Selva, for woody seedlings, only estimated species richness was relatively limited under palms, and non-woody seedlings had relatively lower mean density/m² and mean number of species/m² under only one palm species. Therefore, the relative restriction of seedling recruitment by arborescent palms at La Selva is limited at both individual and landscape scales.     

Impacts of a population outbreak of the urchin Tripneustes gratilla amongst Lord Howe Island coral communities

Subtidal reef surveys within the Lord Howe Island Marine Park revealed that populations of the sea urchin Tripneustes gratilla underwent an explosive outbreak in some regions of the park over a 2-year period. This urchin was rare or absent during 2006 surveys at 33 sites studied, but at sites off northern Lord Howe Island in 2008, densities averaged >1.3 m⁻². Dramatic increases in T. gratilla density (exceeding 4 m⁻²) were observed at some sites. We quantify community-level impacts of T. gratilla using ‘before-after’ and ‘control-impact’ data. Zones closed to fishing exhibited similar increases in T. gratilla density to zones open to fishing. Although not previously reported as a keystone species affecting coral habitat, T. gratilla was found to possess an ‘ecosystem engineer’ function. Outbreak sites were characterised by significant declines in cover of foliose algae, including red algae, which decreased from 11.2% in 2006 compared to 2.5% in 2008. Brown foliose algae also declined at sites where T. gratilla outbreaks occurred, averaging 20.4% in 2006 compared to 1.8% in 2008. By contrast, crustose coralline algal cover increased at sites where high T. gratilla densities were observed, from 2.7% in 2006 to an average of 42.6% in 2008. We found no clear indication of impacts on sessile invertebrates or flow-on effects to other levels of the food web, with no significant change in coral cover or densities of mobile invertebrates or fish populations associated with the T. gratilla outbreak.     

Human-Assisted Invasions of Pacific Islands by Litoria Frogs: A Case Study of the Bleating Tree Frog on Lord Howe Island

There are substantial differences among taxonomic groups in their capacity to reach remote oceanic islands via long-distance overwater dispersal from mainland regions. Due to their permeable skin and intolerance of saltwater, amphibians generally require human-assisted dispersal to reach oceanic islands. Several Litoria frog species have been introduced to remote islands throughout the Pacific Ocean region. Lord Howe Island (LHI) is an oceanic island that lies approximately 600 km east of the Australian mainland and has a diverse, endemic biota. The bleating tree frog (Litoria dentata) is native to mainland eastern Australia, but was accidentally introduced to LHI in the 1990s, yet its ecology and potential impact on LHI has remained unstudied. We used a mitochondrial phylogeographical approach to determine that L. dentata was introduced from the Ballina region in northeastern New South Wales. The founding population was likely accidentally introduced with cargo shipped from the mainland. We also completed the first detailed investigation of the distribution, ecology and habitat use of L. dentata on LHI. The species is widespread on LHI and is prevalent in human habitat, cattle pasture and undisturbed forest. We discuss the potential impact of introduced Litoria species on Pacific islands and outline what biosecurity protocols could be implemented to prevent the introduction of further amphibian species to the ecologically sensitive oceanic area.     

Notes on the biology, captive management and conservation status of the Lord Howe Island Stick Insect (Dryococelus australis) (Phasmatodea)

The Lord Howe Island Stick Insect (Dryococelus australis: Phasmatodea: Phasmatidae: Eurycanthinae) is a large, flightless stick insect once thought to be extinct but rediscovered on an island (Balls Pyramid) near Lord Howe Island in 2001. A captive population at Melbourne Zoo is now in its fourth generation and aspects of the biology of the species are discussed. Observations focussed on the eggs as indicators of the health of the population and inbreeding depression, but included data on the juveniles where possible. Behavioural observations reveal that this species is very different from other Australian stick insects, but similar in many ways to overseas members of the Eurycanthinae. Veterinary interventions and post mortems have provided substantial information about the captive population and its environmental stresses, and have wider implications for captive invertebrate populations, particularly those involved in conservation programs. Evidence of inbreeding and the conservation significance of this species is discussed in context with other programs and their implications.     

Predation on endemic Hawaiian land snails by the invasive snail Oxychilus alliarius

The native land snails of the Hawaiian Islands have suffered numerous extinctions and continue to decline rapidly. A leading cause of these extinctions has been the impact of non-native predators. Oxychilus alliarius is a European predatory snail that has been in Hawaii since at least 1937 and has become one of the most abundant invasive snails in the islands. It is a facultative carnivore and will also consume non-animal food. However, this species has been mostly ignored as a threat and the majority of conservation attention has been focused on Euglandina rosea, the Rosy Wolf Snail. Here we report predation by O. alliarius on two rare and endemic Hawaiian snail species: Kaala subrutila (Helicarionidae) and Pleuropoma cf. sandwichiensis (Helicinidae). The wide distribution of O. alliarius in Hawaii, its high abundance, and now compelling evidence that it preys on native (and probably endangered) snails, indicate that it could be a much greater threat than previously thought.     

Not an ancient relic: the endemic Livistona palms of arid central Australia could have been introduced by humans

Livistona mariae is an endemic palm localized in arid central Australia. This species is separated by about 1000 km from its congener L. rigida, which grows distantly in the Roper River and Nicholson-Gregory River catchments in northern Australia. Such an isolated distribution of L. mariae has been assumed to have resulted from contraction of ancestral populations as Australia aridified from the Mid-Miocene (ca 15 Ma). To test this hypothesis at the population level, we examined the genetic relationships among 14 populations of L. mariae and L. rigida using eight nuclear microsatellite loci. Our population tree and Bayesian clustering revealed that these populations comprised two genetically distinct groups that did not correspond to the current classification at species rank, and L. mariae showed closest affinity with L. rigida from Roper River. Furthermore, coalescent divergence-time estimations suggested that the disjunction between the northern populations (within L. rigida) could have originated by intermittent colonization along an ancient river that has been drowned repeatedly by marine transgression. During that time, L. mariae populations could have been established by opportunistic immigrants from Roper River about 15 000 years ago, concurrently with the settlement of indigenous Australians in central Australia, who are thus plausible vectors. Thus, our results rule out the ancient relic hypothesis for the origin of L. mariae.     

Disruption of male sexual behavior in rats by tetrahydrofurandiols (THF-diols)

The mitogenic agent that disrupts male and female sexual behavior has been isolated from corncob bedding. The disrupting activity resides in an isomeric mixture of linoleic acid derivatives with a tetrahydrofuran ring and two hydroxyl groups (THF-diols) that include 9, (12)-oxy-10, 13-dihydroxtstearic acid and 10, (13)-oxy-9, 12-dihydroxystearic acid. We examined the effects of exposure of male rats to THF-diols in drinking water on several parameters of male sexual behavior. THF-diols disrupt sexual behavior in male rats by reducing mounting and intromission frequencies. The mount, intromission and ejaculatory latencies are enhanced while the ejaculatory responses are diminished. These findings suggest that the THF-diols modulate hypothalamo-pituitary axis to regulate steroid hormone-dependent male sexual behavior.     

Contrasting strategies to cope with drought by invasive and endemic species of Lantana in Galapagos

This study compares how Lantana camara, an invasive species, and L. peduncularis, an autochthonous one, cope with drought in Galapagos. Soil surface temperature was the abiotic environmental parameter that best explained variations in photosynthetic stress. Higher soil surface temperatures were recorded in the lowlands and in rain-shadow areas, which were also the driest areas. L. peduncularis, with a shallow root system, behaved as a drought-tolerant species, showing lower relative growth rates, which decreased with leaf water content and higher photosynthetic stress levels in the lowlands and in a northwest rain-shadow area in comparison with higher and wetter locations. Its basal and maximal fluorescences decreased at lower altitudes, reflecting the recorded drops in chlorophyll concentration. In contrast, L. camara with a deep root system behaved as a drought-avoiding species, showing leaf and relative water contents higher than 55% and avoiding permanent damage to its photosynthetic apparatus even in the driest area where it showed very low chlorophyll content. Its relative growth rate decreased more in dry areas in comparison to wetter zones than did that of L. peduncularis, even though it had greater water content. Furthermore, L. camara showed higher water contents, growth rate, and lower photosynthetic stress levels than L. peduncularis in the arid lowlands. Thus, L. peduncularis maintained lower maximum quantum efficiency of photosystem II photochemistry (F _v/F _m) than L. camara even at sunrise, due to higher basal fluorescence values with similar maximal fluorescence, which indicated permanent damage to PSII reaction centres. Our results help to explain the success and limitations of L. camara in the invasion of arid and sub-arid environments.