Extinction processes in hot spots of avian biodiversity and the targeting of pre-emptive conservation action

Hot spots of endemism are regarded as important global sites for conservation as they are rich in threatened endemic species and currently experiencing extensive habitat loss. Targeting pre-emptive conservation action to sites that are currently relatively intact but which would be vulnerable to particular human activities if they occurred in the future is, however, also valuable but has received less attention. Here, we address this issue by using data on Endemic Bird Areas (EBAs). First, we identify the ecological factors that affect extinction risk in the face of particular human activities, and then use these insights to identify EBAs that should be priorities for pre-emptive conservation action. Threatened endemic species in EBAs are significantly more likely to be habitat specialists or relatively large-bodied than non-threatened species, when compared across avian families. Increasing habitat loss causes a significant increase in extinction risk among habitat specialists, but we found no evidence to suggest that the presence of alien species/human exploitation causes a significant increase in extinction risk among large-bodied species. This suggests that these particular human activities are contributing to high extinction risk among habitat specialists, but not among large-bodied species. Based on these analyses, we identify 39 EBAs containing 570 species (24% of the total in EBAs) that are not currently threatened with severe habitat loss, but would be ecologically vulnerable to future habitat loss should it occur. We show that these sites tend to be poorly represented in existing priority setting exercises involving hot spots, suggesting that vulnerability must be explicitly included within these exercises if such sites are to be adequately protected.     

Managing genetic diversity in threatened populations: a New Zealand perspective

Genetic diversity allows a population to adapt genetically to a changing environment or to buffer it against stochastic events such as harsh weather or disease outbreaks. Genetic diversity is therefore an important consideration in the development of management strategies for threatened populations around the world, with the possible exception of New Zealand, where species recovery programmes tend to focus on increasing population size while neglecting the maintenance of genetic diversity. Many of New Zealand?s threatened species have relatively low genetic variation and consequently may still be at risk in the long-term due to reduced resilience even if the effects of introduced predators were eliminated. The three main factors affecting genetic diversity – genetic drift, inbreeding and population subdivision – are processes that potentially impact on many of our locally threatened species, but their effects tend to occur over a considerably broader timescale than ecological effects, and as such are much more difficult to detect and ultimately to justify additional resource spending towards. Our message is that genetic management of New Zealand threatened species should not take priority over other management concerns such as controlling predators or improving habitat quality, but it needs more attention than it currently receives. We recommend that genetic diversity be a fundamental component in long-term management strategies for threatened species, and that such strategies are made explicit within the New Zealand Department of Conservation?s current species recovery plans so that the persistence of biodiversity becomes of key importance, as opposed to current approaches that seek solely to maximise representation.     

Chainsawing for conservation: Ecologically informed tree removal for habitat management

Summary In many ecosystems, increases in vegetation density and the resulting closure of forest canopies are threatening the viability of species that depend upon open, sunlight‐exposed habitats. Consequently, we need to develop management strategies that recreate open habitats while minimizing the impacts on non‐target areas. Selective logging creates canopy gaps, but may result in undesirable effects in other respects. Thus, chainsaws have not been a popular tool for conservation. We conducted a landscape‐scale experiment to test whether selective tree removal can restore patch‐level habitat quality for Australia’s most endangered snake (Hoplocephalus bungaroides) and its main prey (the lizard Oedura lesueurii). We selectively removed canopy trees surrounding 25 overgrown rock outcrops and compared the resultant habitat structure and abiotic conditions to 30 overgrown, shady outcrops and 20 open, sunny outcrops. Removing vegetation decreased canopy cover by 19% in experimental plots and increased incident radiation and thermal regimes. These changes increased the availability of suitable shelter sites for our target species by 131%. At the landscape scale, our manipulations had a trivial effect on forest habitat; by increasing the area of sun‐exposed outcrops, we decreased forest cover by <0.1%. Our results show that targeted canopy removal can increase the availability of sun‐exposed habitat patches for endangered species in biologically meaningful ways. Thus, selective tree felling may be an effective conservation tool for open‐habitat specialists threatened by vegetation overgrowth.     

The impact of exotic weed competition on a rare New Zealand outcrop herb,

Nearly one quarter of New Zealand’s unique vascular plant flora is threatened, and weed invasion is implicated in the decline of more than half of these threatened species. However, there is little experimental evidence showing that invasive weeds have a direct impact on threatened native plants. This study experimentally tested the hypothesis that competition with invasive weeds threatens the rare outcrop plant Pachycladon cheesemanii (Brassicaceae). Pachycladon cheesemanii is a threatened South Island, New Zealand endemic with a distribution nearly confined to rock outcrops. It has disappeared from historical record sites throughout its range. The effects of weed competition and habitat on P. cheesemanii establishment, growth and survival were investigated by sowing seed into replicated plots subject to three treatments: weed removal, soil disturbed and unweeded control, in three habitat types: forested and open rock outcrops and open tussock grassland. The experiments were carried out at three locations: Mt Somers (Canterbury), Wye Creek and Diamond Lake (Otago). Within weedy rock outcrop habitat, weed removal significantly increased the rate of P. cheesemanii germination, and appeared to increase seedling growth rates, implying that weeds can negatively impact populations. Relative to rock outcrop habitat, P. cheesemanii germination was very low in adjacent open grassland habitat regardless of weeding treatment. Demographic monitoring of four natural populations of P. cheesemanii revealed that seed production is highly variable among populations and may be limited by browse and mechanical damage to inflorescences. Pachycladon cheesemanii does produce a persistent seed bank but most seed is found close to parent populations. Our results suggest that competition with invading weeds threatens current P. cheesemanii populations, that plant establishment can be enhanced by weed removal, and that considerable potential exists for artificially expanding populations by sowing seed into appropriate weed-free habitat.     

Severe pollen limitation in populations of the New Zealand shrub Alseuosmia macrophylla (Alseuosmiaceae) can be attributed to the loss of pollinating bird species

The loss of bird species following human colonization of New Zealand has raised concerns about the consequences for crucial ecosystem functions such as pollination. The understorey shrub Alseuosmia macrophylla (Alseuosmiaceae) exhibits characteristics typical of a bird pollination syndrome, but populations still persist in northern North Island forest remnants despite the local extinction of most endemic bird pollinators, leading to the suggestion that moths – rather than birds – may be the primary pollinators. The aim of this study was to quantify the importance of endemic birds as pollinators of A. macrophylla over several years by comparing plants on Little Barrier Island (LBI), where all extant endemic bird pollinators still occur, to plants at sites on the adjacent North Island in the Waitakere Ranges (WTK), where only one of these species remains common. Flowers on LBI were visited by endemic bellbirds (Anthornis melanura) and stitchbirds (Notiomystis cincta), while at WTK sites the most common visitors were the recently arrived silvereye (Zosterops lateralis) and the introduced honeybee (Apis mellifera), both of which acted principally as nectar robbers. Caged flowers on LBI had significantly lower fruit set than open flowers, and plants at WTK were significantly more pollen‐limited than plants on LBI. This provides evidence that the loss of endemic pollinating birds is the most likely reason for the high pollen limitation found in some North Island A. macrophylla populations, and the very low seed set of these populations could have serious implications for the long‐term persistence of this species.     

Life histories, dispersal, invasions, and global change: progress and prospects in New Zealand ecology, 1989?2029

We highlight three areas of significant progress in ecology since 1989 which are particularly relevant to New Zealand, and three major challenges for the next two decades. Progress: (1) The unusual life histories of New Zealand organisms, including extreme longevity and low reproductive rates, are now seen as efficient responses to the low-disturbance environment present before the arrival of large mammals, including humans. (2) Recent data show that long distance dispersal has been far more common than previously supposed, changing our image of New Zealand from a Gondwanan ark to the ?flypaper of the Pacific?. (3) Greatly improved techniques for pest control, and innovative species management, have stabilised numbers of many of the most charismatic of New Zealand?s threatened species. Problems: (1) Native species continue to decline, including many previously thought to be stable, and improved phylogenetics and new discoveries have added threatened species. (2) Despite increased emphasis on biosecurity, biological invasions are continuing, driven by increased trade and lags in naturalisation. (3) Conservation efforts risk being overwhelmed by the direct effects of increasing human population, resource use, invasions, and global climate change at a time when human food supplies and economies are coming under increasing pressure from environmental constraints. Conclusions: (1) We need improved ecological understanding and more management tools for invasive and threatened species, especially for species other than birds. (2) In these decades of rapid climate change and habitat conversion, there is an urgent need for more widespread and sustainable integration of native species into New Zealand?s rural and urban lowland landscapes.     

Cephaloziella tahora Bever. & Glenny,a new species of Cephaloziella (Jungermanniopsida,Cephaloziellaceae) from eastern Taranaki,New Zealand

Cephaloziella tahora, a new species of Cephaloziella is described and illustrated from a lowland forest habitat in eastern Taranaki in the North Island of New Zealand. It has similarities to six other New Zealand species of Cephaloziella, and appears closest in New Zealand to Cephaloziella aenigmatica R.M.Schust. It is defined by a unique combination of features and distinguished from C. aenigmatica and other New Zealand species by having entire, distant leaves that reach the dorsal stem mid-line, and have large conspicuous hemispherical and hemi-ellipsoidal papillae, underleaves on gemmiparous and gynoecial shoots, and by its dioecy. The addition brings the number of New Zealand species of Cephaloziella to 18, 12 of which are endemic to New Zealand.     

The effects of mice on stoats in southern beech forests

Introduced stoats (Mustela erminea) are important invasive predators in southern beech (Nothofagus sp.) forests in New Zealand. In these forests, one of their primary prey species – introduced house mice (Mus musculus), fluctuate dramatically between years, driven by the irregular heavy seed‐fall (masting) of the beech trees. We examined the effects of mice on stoats in this system by comparing the weights, age structure and population densities of stoats caught on two large islands in Fiordland, New Zealand – one that has mice (Resolution Island) and one that does not (Secretary Island). On Resolution Island, the stoat population showed a history of recruitment spikes and troughs linked to beech masting, whereas the Secretary Island population had more constant recruitment, indicating that rodents are probably the primary cause for the ‘boom and bust’ population cycle of stoats in beech forests. Resolutions Island stoats were 10% heavier on average than Secretary Island stoats, supporting the hypothesis that the availability of larger prey (mice verses wētā) leads to larger stoats. Beech masting years on this island were also correlated with a higher weight for stoats born in the year of the masting event. The detailed demographic information on the stoat populations of these two islands supports previously suggested interactions among mice, stoats and beech masting. These interactions may have important consequences for the endemic species that interact with fluctuating populations of mice and stoats.     

History of weta (Orthoptera: Anostostomatidae) translocation in New Zealand: lessons learned, islands as sanctuaries and the future

Establishing new populations by transferring founder individuals from source populations has been effective for managing the recovery of many threatened species including some weta (Orthoptera: Anostostomatidae) in New Zealand. These large-bodied flightless insects are ‘flagship species’ for insect conservation in New Zealand and many are rare or threatened. The declining abundance of most weta species, particularly giant weta, can be attributed to the introduction of mammalian predators, habitat destruction, and habitat modification by introduced mammalian browsers. New populations of some weta have been established in locations, particularly on islands, where these threats have been eliminated or severely reduced in order to reduce the risk of extinction. Some populations were established to provide food for endemic vertebrates, ecosystem restoration and ready access for the general public. We illustrate how methods for both transferring weta and monitoring them have become more sophisticated by using a series of case studies. Other transfers of weta not included in the case studies are also summarised. We conclude by re-iterating the importance of documenting the transfer and post-release monitoring for all insect transfers, both for biogeographical reasons and to provide information to improve future transfers.     

Population structure within an alpine archipelago: strong signature of past climate change in the New Zealand rock wren (Xenicus gilviventris)

Naturally subdivided populations such as those occupying high‐altitude habitat patches of the ‘alpine archipelago’ can provide significant insight into past biogeographical change and serve as useful models for predicting future responses to anthropogenic climate change. Among New Zealand's alpine taxa, phylogenetic studies support two major radiations: the first correlating with geological forces (Pliocene uplift) and the second with climatic processes (Pleistocene glaciations). The rock wren (Xenicus gilviventris) is a threatened alpine passerine belonging to the endemic New Zealand wren family (Acanthisittidae). Rock wren constitute a widespread, naturally fragmented population, occurring in patches of suitable habitat over c. 900 m in altitude throughout the length of the South Island, New Zealand. We investigated the relative role of historical geological versus climatic processes in shaping the genetic structure of rock wren (N = 134) throughout their range. Using microsatellites combined with nuclear and mtDNA sequence data, we identify a deep north–south divergence in rock wren (3.7 ± 0.5% at cytochrome b) consistent with the glacial refugia hypothesis whereby populations were restricted in isolated refugia during the Pleistocene c. 2 Ma. This is the first study of an alpine vertebrate to test and provide strong evidence for the glacial refugia hypothesis as an explanation for the low endemicity central zone known as the biotic ‘gap’ in the South Island of New Zealand.     

Socio-economic drivers of freshwater fish declines in a changing climate: a New Zealand perspective

New Zealand has a freshwater fish fauna characterized by high levels of national and local endemism and which is threatened by anthropogenic stressors including habitat destruction or deterioration, commercial harvest, pollution and interactions with invasive exotic species. Significant expansion of New Zealand's dairy production has recently created further deterioration of lowland water quality and greater pressure for water allocation in drier eastern regions of the South Island. New Zealand has large freshwater resources and its climate is predicted to experience less dramatic changes in mean annual temperature and precipitation than many other regions of the world as a result of anthropogenic climate change. Predicted changes in regional climate and further expansion of the dairy industry, however, will impose similar pressures on freshwater resources in northern New Zealand to those already acting to threaten freshwater biodiversity in the eastern South Island.     

Kenyan endemic bird species at home in novel ecosystem

Riparian thickets of East Africa harbor a large number of endemic animal and plant species, but also provide important ecosystem services for the human being settling along streams. This creates a conflicting situation between nature conservation and land‐use activities. Today, most of this former pristine vegetation is highly degraded and became replaced by the invasive exotic Lantana camara shrub species. In this study, we analyze the movement behavior and habitat use of a diverse range of riparian bird species and model the habitat availability of each of these species. We selected the following four riparian bird species: Bare‐eyed Thrush Turdus tephronotus, Rufous Chatterer Turdoides rubiginosus, Zanzibar Sombre Greenbul Andropadus importunus insularis, and the Kenyan endemic Hinde′s Babbler Turdoides hindei. We collected telemetric data of 14 individuals during a 2 months radio‐tracking campaign along the Nzeeu River in southeast Kenya. We found that (1) all four species had similar home‐range sizes, all geographically restricted and nearby the river; (2) all species mainly use dense thicket, in particular the invasive L. camara; (3) human settlements were avoided by the bird individuals observed; (4) the birds' movement, indicating foraging behavior, was comparatively slow within thickets, but significantly faster over open, agricultural areas; and (5) habitat suitability models underline the relevance of L. camara as suitable surrogate habitat for all understoreyed bird species, but also show that the clearance of thickets has led to a vanishing of large and interconnected thickets and thus might have negative effects on the population viability in the long run.     

Habitat selection and population trends in terrestrial bird species of Robinson Crusoe Island: habitat generalists versus forest specialists

Habitat loss and degradation on oceanic islands are key processes leading to population decline of endemic birds and facilitating the establishment of invasive bird species. In this study, carried out in the Robinson Crusoe Island, we assessed density and habitat selection of terrestrial bird species, including juan fernandez firecrown and juan fernandez tit-tyrant, two endemics, as well as green-backed firecrown and austral thrush, which apparently originate from the mainland. Results show that perturbed habitats contained a low density of the endemic species whereas the mainland species were significantly more abundant in perturbed scrub habitats. Bird species show different habitat selection patterns, with endemics selecting for native forest and mainland species selecting for perturbed habitats, or using them at random. Bird species experienced temporal trends in their overall population sizes, with the endemic tit-tyrant suffering a significant decline in its population size of about 63% between 1994 and 2009. Only mainland species exhibited temporal changes in habitat use, significantly reducing their densities in the preferred scrub habitats, possibly as a response to decreased habitat quality. Thrushes apparently were able to compensate the population decrease in one non native habitat type by using native forests, a habitat giving them the opportunity of preying on nests of endemic species. We conclude that endemic bird species behave as specialists whereas the mainland species must be treated as invasive generalists on Robinson Crusoe Island.     

Conservation genetic management of a critically endangered New Zealand endemic bird: minimizing inbreeding in the Black Stilt Himantopus novaezelandiae

For threatened species with small captive populations, it is advisable to incorporate conservation management strategies that minimize inbreeding in an effort to avoid inbreeding depression. Using multilocus microsatellite genotype data, we found a significant negative relationship between genetic relatedness (inbreeding) and reproductive success (fitness) in a captive population of the critically endangered Black Stilt or KakīHimantopus novaezelandiae. In an effort to avoid inbreeding depression in this iconic New Zealand endemic, we recommend re‐pairing closely related captive birds with less related individuals and pairing new captive birds with distantly related individuals.     

Polytrichum commune Hedw. and Polytrichadelphus magellanicus (Hedw.) Mitt. used as decorative material on New Zealand Maori cloaks

Abstract

Confirmation of the occurrence of the moss Ptychomnion densifolium on the main islands of New Zealand is provided and the features which separate it from the more common P. aciculare are outlined. A brief account of the history of P. densifolium in New Zealand is given and its morphology there is discussed. A key to the two species in New Zealand is provided and habitat differences between them outlined. New Zealand material differs from type locality (Tristan d' Acunha) material in having longer and more twisted acumens, and in this respect is similar to New Zealand material of P. aciculare. New Zealand populations of P. densifolium are recognisable in having stem leaves reflexed from an oblong sheathing base, and well developed basal leaf plications. It is a relatively widespread species in New Zealand, occurring in mostly upper elevation, open sites.     

Abundance-age-area relationships in an insular plant community

Two processes are thought to generate positive relationships between species richness and island area. The areaper se hypothesis states that larger islands maintain larger populations, which are less susceptible to extinction. The habitat hypothesis states that larger islands contain more habitats, and therefore a greater number of habitat specialists. However, the importance of each mechanism is debated. I tested the areaper se and habitat hypotheses by comparing relationships between plant abundance, age and island area in five shrub species on islands off the coast of British Columbia, Canada. Results showed that two shrub species increased in both abundance and age with island area. The remaining three species showed no differences in abundance and age with island area. Conifer abundances increased with island area, which generated differences in habitat availability. Smaller islands were dominated by open habitat, while larger islands contained both open and forested habitats. Changes in habitat availability with island area could explain patterns in plant abundance and age. The two species that increased in abundance with island area were commonly found in conifer forest on the mainland, and their distributions were consistent with the distribution forest habitat. Positive relationships between plant age and island area in these two species may result from lower survivorship in the open habitat, which dominated small islands. The three species that showed no relationship between abundance and island area are commonly found in open habitat on the mainland, and their island distributions paralleled the availability of open habitat on islands. Similar plant ages on different sized islands may result from their occurrence in open habitat on both large and small islands. Overall results support the habitat hypothesis and indicate that species distributions result from the interaction between habitat affinities and changes in habitat availability with island area.     

Conservation status of New Zealand frogs, 2009

Abstract

A reappraisal of the conservation status of the New Zealand frog fauna is presented using the 2008 version of the New Zealand Threat Classification System. Of New Zealand's four extant endemic species, three are judged to be ‘Threatened’ (Leiopelma hamiltoni being ‘Nationally Critical’, and L. pakeka and L. archeyi being ‘Nationally Vulnerable’) and one ‘At Risk’ (L. hochstetteri ‘Declining’). Three Leiopelma species are listed as extinct—they are known from bone deposits in caves throughout the country until some time in the last 1000 years. Three introduced and naturalised Litoria species are abundant in New Zealand although two (L. aurea and L. raniformis) are threatened in their country of origin (Australia). An additional unidentified frog taxon from northern Great Barrier Island is listed as ‘Data Deficient’.     

Taxonomic and conservation status of a newly discovered giant landsnail from Mount Augustus,New Zealand

The Rhytidae (Mollusca; Gastropoda; Pulmonata) are a group of large carnivorous land snails distributed in the southern hemisphere, with a particularly rich fauna in New Zealand. The endemic genus Powelliphanta consists of at least 10 species and many more recognised subspecies, most of which are restricted to the western margin of South Island, New Zealand. Powelliphanta taxa tend to have restricted ecological and spatial ranges among the mountains of this region, with some species being limited to lowland forest and others to habitats at or above the treeline. Among recent discoveries is a population of snails occupying habitat on and around a peak called Mt Augustus, which is situated at the edge of a large and economically important coalfield. Since recognition of the potential biological significance of the Mt Augustus snails in 2004, almost all of their habitat has been destroyed by opencast mining revealing a direct conflict between economic and biodiversity prioritisation. Our analysis of mtDNA sequence data indicate Powelliphanta “Augustus” is a distinctive evolutionary lineage, more closely related to a nearby lowland species Powelliphanta lignaria than the spatial and ecological neighbour Powelliphanta patrickensis. Powelliphanta “Augustus” appears to be a specialised local endemic species. Despite a growing international awareness of the importance of biodiversity conservation, the demand for foreign earnings continues to take priority over the protection of our biota.     

Can increased niche opportunities and release from enemies explain the success of introduced Yellowhammer populations in New Zealand?

Some introduced species succeed spectacularly, becoming far more abundant in their introduced than in their native range. 'Increased niche opportunities' and 'release from enemy regulation' are two hypotheses that have been advanced to explain the enhanced performance of introduced species in their new environments. Using an introduced bird species, the Yellowhammer Emberiza citrinella , which was first released in New Zealand in 1862, as a model, we tested some predictions based on these hypotheses. By quantifying habitat availability and quality, and measuring nest predation rates, we investigated whether increased niche opportunities or release from nest predation could explain the higher density of the Yellowhammer in New Zealand farmland, compared to farmland in their native Britain. Yellowhammer territory densities were over three times higher in New Zealand (0.40 territories per ha) than in comparable British farmland (0.12 territories per ha), and Yellowhammer densities remained significantly higher in New Zealand, after accounting for differences in habitat availability. The density and diversity of invertebrates, a key food resource for nestling Yellowhammers, was significantly lower in New Zealand than in Britain. Hence, these aspects of niche availability and quality cannot explain the higher density of Yellowhammers in New Zealand. Nest predation rates in New Zealand were similar to those in Britain, suggesting that release from nest predation also could not account for the higher density of Yellowhammers in New Zealand. Differences in winter survival, due to differences in winter food supply or the severity of the winter climate, along with release from other types of 'enemy' regulation are possible alternative explanations.