Island Invasion by a Threatened Tree Species: Evidence for Natural Enemy Release of Mahogany (Swietenia macrophylla) on Dominica, Lesser Antilles

Despite its appeal to explain plant invasions, the enemy release hypothesis (ERH) remains largely unexplored for tropical forest trees. Even scarcer are ERH studies conducted on the same host species at both the community and biogeographical scale, irrespective of the system or plant life form. In Cabrits National Park, Dominica, we observed patterns consistent with enemy release of two introduced, congeneric mahogany species, Swietenia macrophylla and S. mahagoni, planted almost 50 years ago. Swietenia populations at Cabrits have reproduced, with S. macrophylla juveniles established in and out of plantation areas at densities much higher than observed in its native range. Swietenia macrophylla juveniles also experienced significantly lower leaf-level herbivory (~3.0%) than nine co-occurring species native to Dominica (8.4–21.8%), and far lower than conspecific herbivory observed in its native range (11%–43%, on average). These complimentary findings at multiple scales support ERH, and confirm that Swietenia has naturalized at Cabrits. However, Swietenia abundance was positively correlated with native plant diversity at the seedling stage, and only marginally negatively correlated with native plant abundance for stems ≥1-cm dbh. Taken together, these descriptive patterns point to relaxed enemy pressure from specialized enemies, specifically the defoliator Steniscadia poliophaea and the shoot-borer Hypsipyla grandella, as a leading explanation for the enhanced recruitment of Swietenia trees documented at Cabrits.

Falkland Island English

This chapter examines some of the grammatical variability and non-standardness found in the English of the Falkland Islands. The Falklands are an archipelago of over 700 islands located in the western South Atlantic Ocean, 480km off the east coast of Argentina. Although the population is small – around 3000 - the islands cover an area of over 12000km2 – slightly larger than Jamaica and half the size of Wales, making them, after Greenland, the most sparsely populated political entity in the world. In political terms, the Falklands are an Overseas Territory of the United Kingdom. In contrast to the rural isolated image that the Falklands perhaps conjure up, the community is, in demographic terms, an urban and diverse one. Over 85% of the population living in the capital Stanley. The 2006 census (Government of the Falkland Islands 2007: 6) shows that 55% of the population were not born on the Islands, with the largest migrant groups coming from the UK, St Helena (another British Overseas Territory, located in the eastern South Atlantic), Chile and Australia. It also highlighted the fact that people born in 62 different countries were resident on the islands at the time (Pascoe and Pepper 2008: 38). By way of a comparison, only Monaco and Andorra, in Europe, have a higher proportion of their populations made up of migrants. In addition to the local Falkland population, there is a large military presence on the islands at the Royal Airforce Base at Mount Pleasant, 50km south-west of Stanley. The Head of State is the monarch of the UK, who is represented on the islands by a governor. The democratically elected 11-member Legislative Assembly is responsible for day-to-day government of the islands. The Falklands are perhaps most famous because of their 74 day occupation by Argentina in 1982. It is not appropriate here to go into detail about the dispute between the UK and Argentina about the sovereignty of the Islands. What is undisputed is that there has been a continuous Anglophone speech community on the islands since the early 1830s, making it one of the most recently developed ‘Inner Circle’ (Kachru 1985) Englishes in the world. This chapter examines the grammatical characteristics of Falkland Island English, drawn from a transcribed corpus of over 500,000 words of informal conversational speech, collected by Andrea Sudbury both in Stanley and in ‘Camp’ (the local name for the rest of the islands) (see Sudbury 2000, 2001 for more details about the methods used in the survey).

Ecosystem impacts of feral rabbits on World Heritage sub-Antarctic Macquarie Island: A palaeoecological perspective

The introduction and establishment of non-indigenous species through human activities often poses a major threat to natural biodiversity. In many parts of the world management efforts are therefore focused on their eradication. The environment of World Heritage sub-Antarctic Macquarie Island has been severely damaged by non-indigenous species including rabbits, rats and mice, introduced from the late AD 1800s. An extensive eradication programme is now underway which aims to remove all rabbits and rodents. To provide a long-term context for assessing the Island's pre-invasion state, invasion impacts, and to provide a baseline for monitoring its recovery, we undertook a palaeoecological study using proxies in a lake sediment core. Sedimentological and diatom analyses revealed an unproductive catchment and lake environment persisted for ca. 7100 years prior to the introduction of the invasive species. After ca. AD 1898, unprecedented and statistically significant environmental changes occurred. Lake sediment accumulation rates increased >100 times due to enhanced catchment inputs and within-lake production. Total carbon and total nitrogen contents of the sediments increased by a factor of four. The diatom flora became dominated by two previously rare species. The results strongly suggest a causal link between the anthropogenic introduction of rabbits and the changes identified in the lake sediments. This study provides an example of how palaeoecology may be used to determine baseline conditions prior to the introduction of non-indigenous species, quantify the timing and extent of changes, and help monitor the recovery of the ecosystem and natural biodiversity following successful non-indigenous species eradication programmes.