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Report on IUCN Island Invasives Conference, Auckland, February 2001
Islands support some of the world’s most remarkable ecosystems. They are home to numerous distinctive species, interlocking in unique plant and animal communities. They are demonstrations of evolution in action.
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.
Decline in the distribution and abundance of flesh-footed shearwaters on Lord Howe Island Australia
The flesh-footed shearwater (Puffinus carneipes) is a migratory seabird that ranges widely across the Pacific and Indian Oceans. The principal breeding populations are in Australia and New Zealand. The only breeding site in eastern Australia is on Lord Howe Island. Despite it being afforded a high level of legislative protection, the population on Lord Howe Island has declined substantially during the last few decades.
Lepidorrhachis mooreana must surely rate as one of the most narrowly distributed of all palms. Not only is this monotypic genus endemic to the remote Pacific island of Lord Howe 580 km off the eastern coast of Australia, but it is also restricted to the summits of the island’s two mountains, Mt. Gower (875 m) and Mt. Lidgbird (777 m), where it occurs above 750 m in dwarf mossy forest.
Conservation issues for the vascular flora of Lord Howe Island
The flora of the Lord Howe Island Group (31°30’S, 159°05’E) comprises a unique mix of elements of Australian, New Zealand and New Caledonian floras. It is significant for its high degree of endemism and for its structural and biological (leaves, flowers, fruit) role in supporting a diverse array of fauna. Conservation of this flora is dependant upon: reducing current habitat degradation (mostly the result of exotic weeds); minimising any future impacts, in particular the effects of climate change on the unique cloud forests of the southern mountains and the continued introduction and spread of weeds and the pathogen Phytophthora cinnamomi.
Breeding biology of the Black-winged Petrel, Pterodroma nigripennis, on Lord Howe Island
The Black-winged Petrel, Pterodroma nigripennis, is a recent coloniser of Lord Howe Island, with adults present between late October and early May. Four nests were monitored during both the 1989-90 and 1990-91 breeding seasons.
Breeding biology of Masked Boobies (Sula dactylatra tasmani) on Lord Howe Island
The breeding biology and reproductive output of a colony of Masked Boobies on Mutton Bird Point, Lord Howe Island, Australia, were studied during the 2001 02 breeding season. The colony produced a total of 200 clutches. Eggs were laid between 31 May and 15 September 2001, with 80% of clutches begun before 21 July. More than 90% of clutches consisted of two eggs, laid, on average, 5.3 days apart.
Little Shearwaters, Puffinus assimilis assimilis, breeding on Lord Howe Island
Little Shearwaters, Puffinus assimilis assimilis, were thought to have disappeared from Lord Howe Island during the early 1900s. This study reports Little Shearwaters breeding on Lord Howe Island between 1990 and 2001. A survey in 2000 recorded 85 nestlings. It is unclear whether this species has persisted on Lord Howe Island in low numbers throughout last century or whether it is recolonising.
Sympatric speciation in palms on an oceanic Island
The origin of species diversity has challenged biologists for over two centuries. Allopatric speciation, the divergence of species resulting from geographical isolation, is well documented. However, sympatric speciation, divergence without geographical isolation, is highly controversial. Claims of sympatric speciation must demonstrate species sympatry, sister relationships, reproductive isolation, and that an earlier allopatric phase is highly unlikely. Here we provide clear support for sympatric speciation in a case study of two species of palm (Arecaceae) on an oceanic island. A large dated phylogenetic tree shows that the two species of Howea, endemic to the remote Lord Howe Island, are sister taxa and diverged from each other well after the island was formed 6.9 million years ago. During fieldwork, we found a substantial disjunction in flowering time that is correlated with soil preference. In addition, a genome scan indicates that few genetic loci are more divergent between the two species than expected under neutrality, a finding consistent with models of sympatric speciation involving disruptive/divergent selection. This case study of sympatric speciation in plants provides an opportunity for refining theoretical models on the origin of species, and new impetus for exploring putative plant and animal examples on oceanic islands.
Disruption of recruitment in two endemic palms on Lord Howe Island by invasive rats
Invasive species may have negative impacts on many narrow range endemics and species restricted to oceanic islands. Predicting recent impacts of invasive species on long-lived trees is, difficult because the presence of adult plants may,mask population changes. We examined the impact of introduced black rats (Rattus rattus) on two palm species restricted to cloud forests and endemic to Lord Howe Island, a small oceanic island in the southern Pacific. We combined estimates of the standing size distribution of these palms with the proximal impacts of rats on fruit survival in areas baited to control rats and in unbaited areas. The size distribution of palms with trunks was comparable across baited and unbaited sites. Small juvenile palms lacking a trunk (<50 cm tall) were abundant in baited areas, but rare in unbaited sites for Lepidorrhachis mooreana, and rare or absent in 3 out of 4 unbaited Hedyscepe canterburyana sites. All ripe fruits were lost to rats in the small fruited L. mooreana. Fruit removal was widespread but less (20–54%) in H. canterburyana. Both palms showed evidence of a reduced capacity to maintain a juvenile bank of palms through regular recruitment as a consequence of over 90 years of rat impact. This will limit the ability of these species to take advantage of episodic canopy gaps. Baiting for rat control reduced fruit losses and resulted in the re-establishment of a juvenile palm bank. Conservation of both endemic palms necessitates control (or eradication) of rat populations on the unique cloud forest summits of the island.
Floristics and structure of the mossy cloud forest of Mt Gower summit, Lord Howe Island
The summit of Mt Gower, Lord Howe Island (31°33’8, 159°05’E), is a small area of 27 ha supporting mossy cloud forest. This study describes patterns in the floristic composition and structure of the vegetation of the summit, in relation to a range of environmental variables. A total of 42 vascular plant species was recorded, 86% of which are endemic to Lord Howe Island, and 17% of which are found only on the summit and upper slopes of Mt Gower and adjacent Mt Lidgbird. A complete species list for Mt Gower is presented, including species from the present survey and all previously recorded species. The composition of the vegetation differed In gullies and on ridges, reflecting differences in substrate rockiness and soil moisture, and was also influenced by the number of bird burrows and aspect. The summit of Mt Gower is of high conservation significance, due to the restricted distribution of the habitat type it represents, its relatively undisturbed state and high levels of endemism. Potential threats to the summit vegetation include the impacts of climate change, seed predation by introduced rats, and the introduction of weed species and exotic pathogens such as Phytophthora cinnamomi.