Extinction patterns in the avifauna of the Hawaiian islands

Reduction of genetic diversity in 'Alalā (Hawaiian crow; Corvus hawaiiensis) between the late 1800s and the late 1900s

Genetic and genomic data are increasingly used to aid conservation management of endangered species by providing insights into evolutionary histories, factors associated with extinction risks, and potential for future adaptation. For the 'Alalā, or Hawaiian crow (Corvus hawaiiensis), genetic concerns include negative correlations between inbreeding and hatching success. However, it is unclear if low genetic diversity and inbreeding depression are consequences of a historical population bottleneck, or if 'Alalā had historically low genetic diversity that predated human influence, perhaps as a result of earlier declines or founding events. In this study, we applied a hybridization-based sequence capture to generate a genome-wide single nucleotide polymorphism (SNP) dataset for comparing historical specimens collected in the 1890s, when 'Alalā were more numerous, to samples taken between 1973 and 1998, when 'Alalā population densities were near the lowest documented levels in the wild, prior to all individuals being collected for captive rearing. We found low genome-wide diversity in both sample groups, however, the modern sample group (1973 to 1998 cohort) exhibited relatively fewer polymorphic alleles, a lower proportion of polymorphic loci, and lower observed heterozygosity, consistent with a population decline and potential bottleneck effects. These results combined with a current low population size highlight the importance of continued efforts by conservation managers to mitigate inbreeding and maintain founder representation to preserve what genetic diversity remains.

Undiscovered bird extinctions obscure the true magnitude of human-driven extinction waves

Birds are among the best-studied animal groups, but their prehistoric diversity is poorly known due to low fossilization potential. Hence, while many human-driven bird extinctions (i.e., extinctions caused directly by human activities such as hunting, as well as indirectly through human-associated impacts such as land use change, fire, and the introduction of invasive species) have been recorded, the true number is likely much larger. Here, by combining recorded extinctions with model estimates based on the completeness of the fossil record, we suggest that at least ~1300-1500 bird species (~12% of the total) have gone extinct since the Late Pleistocene, with 55% of these extinctions undiscovered (not yet discovered or left no trace). We estimate that the Pacific accounts for 61% of total bird extinctions. Bird extinction rate varied through time with an intense episode ~1300 CE, which likely represents the largest human-driven vertebrate extinction wave ever, and a rate 80 (60-95) times the background extinction rate. Thus, humans have already driven more than one in nine bird species to extinction, with likely severe, and potentially irreversible, ecological and evolutionary consequences.

Field evaluation of organic and synthetic insecticides against the hala scale, Thysanococcus pandani (Hemiptera: Halimococcidae), on Maui, Hawaii

The hala scale, Thysanococcus pandani Stickney, is an invasive insect that infests hala trees, Pandanus tectorius, and has recently arrived in the Hawaiian Islands of Maui, Oahu, and Molokai. Hala scale is native to Thailand, Indonesia, and Singapore and was accidentally introduced to Maui, with its first detection in Hana in 1995. The hala tree is a frequently planted ornamental plant throughout Hawaii's urban landscape and is also a native tree found in coastal areas of ecological suitability throughout the state. These trees are integral to native Hawaiian weaving traditions, as the leaves were used to make items such as sails, hats, or mats. The spread of T. pandani threatens the continuation of these practices, as the plant material may not be sufficient for weaving. Hala trees infested with T. pandani can have negative effects such as deformation, discoloration, and early tree death. Experimental field trials were set up to evaluate the efficacy of organic and chemical insecticides as potential treatments to mitigate the damage of T. pandani infestations. This was done on the Island of Maui, where T. pandani is widespread. These trees were artificially inoculated with T. pandani and evaluated throughout the trials for changes in plant height, canopy width, scale removal, and visual infestation ratings. The results of 2 repeated field trials indicated that flupyradifurone and buprofezin were effective treatments in the reduction of the hala scale infestation and improving visual aspects related to plant health.

A Hawaiian Tropical Dry Forest Regenerates: Natural Regeneration of Endangered Species under Biocultural Restoration

Tropical dry forests (TDFs) are among the most at-risk ecosystems globally. In Hawai‘i, more than 45% of TDF species are threatened or endangered. Despite decades of active TDF restoration, there remains limited information on the potential for long-term success, since there are few studies of natural regeneration. We assess natural regeneration of endangered plants at Ka‘ūpūlehu dryland forest, a Hawaiian biocultural restoration initiative. Drawing on 6 annual censuses we (1) assess rates and patterns of natural regeneration across species and as a function of rainfall and (2) identify bottlenecks. Our surveys document natural recruits of 11 of the 12 endangered species first outplanted 15–20 years ago. Higher annual rainfall increased the number of new recruits per year and growth, but decreased survival of larger recruits. The total number of natural recruits increased three-fold over the study period and varied across species. For nearly half of the species, we documented a second generation of recruits. Successes appear to be a function of time, including a changing microclimate and adaptive management practices. Remaining bottlenecks include lack of seed dispersal, and seed predation and herbivory by introduced species. The success at Ka‘ūpūlehu highlights the potential for TDF restoration and the value of a biocultural approach.

Assessing the relationship between species traits and extinction risk at a regional level: an analysis involving Brazilian terrestrial mammals

One of the various concerns of conservation biology is determining why certain species are more threatened than others. In this study, we aim to relate the national conservation status of Brazilian mammals with the taxonomic group to which they belong and with three of their intrinsic traits: body mass, diet, and litter size. We compiled a database containing the species, their status, and their attributes, and a multiple correspondence analysis was applied to identify relationships between traits and status. The two groups that presented the highest relative frequencies of threatened species were "ungulates" and Carnivora. Additionally, mammals with body mass of 10 kg or more and with carnivorous diet had a higher relative frequency of threatened taxa. We found not only a strong relationship between intrinsic traits and conservation status, but also among the traits themselves, which highlights the role of the "group" variable as one of the best predictors of the risk that a given species be threatened. We believe our study has a broad potential for the conservation of species at the regional level, especially regarding the species currently classified as Data Deficient, and for identifying which species are prone to becoming threatened.

Loss of functional diversity through anthropogenic extinctions of island birds is not offset by biotic invasions

Human impacts reshape ecological communities through the extinction and introduction of species. The combined impact of these factors depends on whether non-native species fill the functional roles of extinct species, thus buffering the loss of functional diversity. This question has been difficult to address, because comprehensive information about past extinctions and their traits is generally lacking. We combine detailed information about extinct, extant, and established alien birds to quantify historical changes in functional diversity across nine oceanic archipelagos. We found that alien species often equal or exceed the number of anthropogenic extinctions yet apparently perform a narrower set of functional roles as current island assemblages have undergone a substantial and ubiquitous net loss in functional diversity and increased functional similarity among assemblages. Our results reveal that the introduction of alien species has not prevented anthropogenic extinctions from reducing and homogenizing the functional diversity of native bird assemblages on oceanic archipelagos.

Characterizing the spatio-temporal threats, conservation hotspots and conservation gaps for the most extinction-prone bird family (Aves: Rallidae)

With thousands of vertebrate species now threatened with extinction, there is an urgent need to understand and mitigate the causes of wildlife collapse. Rails (Aves: Rallidae), being the most extinction-prone bird family globally, and with one-third of extant rail species now threatened or near threatened, are an emphatic case in point. Here, we undertook a global synthesis of the temporal and spatial threat patterns for Rallidae and determined conservation priorities and gaps. We found two key pathways in the threat pattern for rails. One follows the same trajectory as extinct rails, where island endemic and flightless rails are most threatened, mainly due to invasive predators. The second, created by the diversification of anthropogenic activities, involves continental rails, threatened mainly by agriculture, natural system modifications, and residential and commercial development. Indonesia, the USA, the United Kingdom, New Zealand and Cuba were the priority countries identified by our framework incorporating species' uniqueness and the level of endangerment, but also among the countries that lack conservation actions the most. Future efforts should predominantly target improvements in ecosystem protection and management, as well as ongoing research and monitoring. Forecasting the impacts of climate change on island endemic rails will be particularly valuable to protect rails.

Biological Correlates of Extinction Risk in Resident Philippine Avifauna

The majority of the world’s biodiversity occurs in the tropics, but human actions in these regions have precipitated an extinction crisis due to habitat degradation, overexploitation, and climate change. Understanding which ecological, biogeographical, and life-history traits predict extinction risk is critical for conserving species. The Philippines is a hotspot of biodiversity and endemism, but it is a region that also suffers from an extremely high level of deforestation, habitat degradation, and wildlife exploitation. We investigated the biological correlates of extinction risk based on the IUCN Red List threat status among resident Philippine birds using a broad range of ecological, biogeographical, and life history traits previously identified as correlates of extinction risk in birds. We found strong support across competing models for endemism, narrower elevational ranges, high forest dependency, and larger body size as correlates significantly associated with extinction risk. Additionally, we compared observed threat status with threat status fitted by our model, finding fourteen species that are not currently recognized by the IUCN Red List as threatened that may be more threatened than currently believed and therefore warrant heightened conservation focus, and predicted threat statuses for the four Philippine Data Deficient bird species. We also assessed species described in recent taxonomic splits that are recognized by BirdLife International, finding 12 species that have a fitted threat status more severe than their IUCN-designated ones. Our findings provide a framework for avian conservation efforts to identify birds with specific biological correlates that increase a species’ vulnerability to extinction both in the Philippine Archipelago and elsewhere on other tropical islands.

The island rule explains consistent patterns of body size evolution in terrestrial vertebrates

Island faunas can be characterized by gigantism in small animals and dwarfism in large animals, but the extent to which this so-called 'island rule' provides a general explanation for evolutionary trajectories on islands remains contentious. Here we use a phylogenetic meta-analysis to assess patterns and drivers of body size evolution across a global sample of paired island-mainland populations of terrestrial vertebrates. We show that 'island rule' effects are widespread in mammals, birds and reptiles, but less evident in amphibians, which mostly tend towards gigantism. We also found that the magnitude of insular dwarfism and gigantism is mediated by climate as well as island size and isolation, with more pronounced effects in smaller, more remote islands for mammals and reptiles. We conclude that the island rule is pervasive across vertebrates, but that the implications for body size evolution are nuanced and depend on an array of context-dependent ecological pressures and environmental conditions.

The spatial ecology of invasive feral cats Felis catus on San Cristóbal, Galápagos: first insights from GPS collars

The dangers posed by invasive species for endemic island wildlife are well recognised. Introduced domestic cats (Felis catus) represent a significant threat to several endemic species of the Galápagos archipelago—including hatchling marine iguanas (Amblyrhynchus cristatus) and potentially green turtles (Chelonia mydas)—yet little is known about their spatial ecology and habitat use on these islands. Here, we describe a pilot study using GPS collars to track the movements of three feral cats at a site of conservation interest on San Cristóbal Island. Based on 175 days of GPS data, we undertook spatial analyses to ascertain home ranges, and to investigate the overlap of ranges between the cats and potential prey species. Average home range was 1.27 km2 (1.12–1.46 km2), which—though small for feral cats—is in keeping with previous findings in Galápagos. We found the cats did use the habitat of a small marine iguana population but did not change their spatial habits before and after iguana hatchlings appeared. Changes over time in the daily movements of one cat indicated a possible response of the individual to the presence of hatchling green turtles (Chelonia mydas); though the data here are insufficient to show whether the cat was hunting these hatchlings. We recommend similar work be undertaken in areas with larger marine iguana populations, where hatchlings could represent a potentially important food source for invasive feral cats, as well as further work to determine the threat posed by cats to turtle hatchlings in Galápagos.

Unforeseen diversity of quails (Galliformes: Phasianidae: Coturnix) in oceanic islands provided by the fossil record of Macaronesia

The original bird fauna of most oceanic islands has been affected by recent extinction processes associated with human arrival and its subsequent impacts. In the volcanic Macaronesian archipelagos (Azores, Madeira, Selvagens, Canary Islands and Cape Verde), in the North Atlantic, the Late Quaternary fossil record indicates that there was formerly a higher avian diversity, including a high number of now extinct endemic species. This assemblage of extinct birds includes endemic insular quails (Galliformes: Phasianidae). In this study, we describe three newly discovered extinct species of quails, two of which inhabited the archipelago of Madeira (Coturnix lignorum sp. nov. from Madeira Island and Coturnix alabrevis sp. nov. from Porto Santo Island) and one from Cape Verde (Coturnix centensis sp. nov.). The fossil record also indicates the presence of additional species of extinct endemic quails on other Macaronesian islands. These birds plus the extinct Canary Island quail (Coturnix gomerae) indicate a high former endemic diversity of this genus in Macaronesia, a feature unique among oceanic archipelagos. Anatomical traits show that the new taxa were flightless ground dwellers, making them vulnerable to human interference, with their extinction being linked to human arrival and subsequent habitat alterations and the introduction of invasive species.

Manipulating social information to promote frugivory by birds on a Hawaiian Island

Animals across a range of taxa use social information when foraging. Fruit-eating vertebrates are no exception and use social information to find fruit, which may ultimately affect plant populations via seed dispersal. In many systems, mutualistic relationships between fruiting plants and frugivores are critical to maintain ecosystem functioning, especially in the tropics. On the island of O'ahu, Hawaii, USA, all native, fruit-eating birds are extinct and several plant species are experiencing reduced recruitment likely due to a lack of seed dispersal. Over the years, numerous bird species, many of which are frugivorous, have been introduced to the island. Yet, introduced birds may not recognize native fruits as a resource and social information may be needed for introduced frugivores to target and feed on native fruits. We investigated whether social information, in the form of broadcasted bird vocalizations, of introduced birds could increase visitations and more importantly frugivory on focal fruiting plants. We also tested whether the visitation rates of introduced bird species to focal plants were influenced by conspecific and/or heterospecific vocalizations. We conducted 80 playback experiments at native and introduced fruiting plants, and compared responses to silent control periods. Four times as many frugivores were detected and 10 times more frugivory events were recorded at plants with broadcasted vocalizations compared to control periods. The Japanese White-eye (Zosterops japonicus) exhibited the strongest response to both conspecific and heterospecific playbacks. White-eyes also consumed the most fruit from the widest array of plant species during trials. Introduced birds that use social information and readily identify novel resources may more effectively colonize new areas. We suggest that the White-eye's use of social information may help to support their robust population on O'ahu. Ecosystems throughout the world are affected by the loss of mutualistic relationships, many of which provide valuable ecological services. As humans continue to modify environments, novel conservation approaches may be required to maintain important ecological functions. The use of social information to facilitate frugivory may not only be important in Hawaii, but in other tropical systems where key frugivorous species are lost or abundances have been reduced.

Non-native insects dominate daytime pollination in a high-elevation Hawaiian dryland ecosystem

PREMISE OF THE STUDY

Over one-third of the native flowering plant species in the Hawaiian Islands are listed as federally threatened or endangered. Lack of sufficient pollination could contribute to reductions in populations, reproduction, and genetic diversity among these species but has been little studied.

METHODS

We used systematic observations and manual flower treatments to quantify flower visitation and outcrossing dependency of eight native (including four endangered) plant species in a dryland ecosystem in Hawaii: Argemone glauca, Bidens menziesii, Dubautia linearis, Haplostachys haplostachya, Sida fallax, Silene lanceolata, Stenogyne angustifolia, and Tetramolopium arenarium.

KEY RESULTS

During 576.36 h of flower observations, only insects visited the flowers. Out of all recorded flower visits, 85% were performed by non-native species, particularly the honeybee (Apis mellifera) and flies in the family Syrphidae. Some plant species received little visitation (e.g., S. angustifolia received one visit in 120 h of observation), whereas others were visited by a wide diversity of insects. The endangered plant species were visited by fewer visitor taxa than were the common native plant species. For six of the focal plant species, bagging of flowers to exclude pollinators resulted in significant reductions in seed set.

CONCLUSIONS

The flower visitor community in this system, although heavily dominated by non-native insects, appears to be facilitating pollination for multiple plant species. Non-native insects may thus be sustaining biotic interactions otherwise threatened with disruption in this island ecosystem. This may be particularly important for the studied endangered plant species, which exhibit fewer partners than the more common plant species.

Invasive predators and global biodiversity loss

Invasive species threaten biodiversity globally, and invasive mammalian predators are particularly damaging, having contributed to considerable species decline and extinction. We provide a global metaanalysis of these impacts and reveal their full extent. Invasive predators are implicated in 87 bird, 45 mammal, and 10 reptile species extinctions-58% of these groups' contemporary extinctions worldwide. These figures are likely underestimated because 23 critically endangered species that we assessed are classed as "possibly extinct." Invasive mammalian predators endanger a further 596 species at risk of extinction, with cats, rodents, dogs, and pigs threatening the most species overall. Species most at risk from predators have high evolutionary distinctiveness and inhabit insular environments. Invasive mammalian predators are therefore important drivers of irreversible loss of phylogenetic diversity worldwide. That most impacted species are insular indicates that management of invasive predators on islands should be a global conservation priority. Understanding and mitigating the impact of invasive mammalian predators is essential for reducing the rate of global biodiversity loss.

Convex-hull mass estimates of the dodo (Raphus cucullatus): application of a CT-based mass estimation technique

The external appearance of the dodo (Raphus cucullatus, Linnaeus, 1758) has been a source of considerable intrigue, as contemporaneous accounts or depictions are rare. The body mass of the dodo has been particularly contentious, with the flightless pigeon alternatively reconstructed as slim or fat depending upon the skeletal metric used as the basis for mass prediction. Resolving this dichotomy and obtaining a reliable estimate for mass is essential before future analyses regarding dodo life history, physiology or biomechanics can be conducted. Previous mass estimates of the dodo have relied upon predictive equations based upon hind limb dimensions of extant pigeons. Yet the hind limb proportions of dodo have been found to differ considerably from those of their modern relatives, particularly with regards to midshaft diameter. Therefore, application of predictive equations to unusually robust fossil skeletal elements may bias mass estimates. We present a whole-body computed tomography (CT) -based mass estimation technique for application to the dodo. We generate 3D volumetric renders of the articulated skeletons of 20 species of extant pigeons, and wrap minimum-fit ‘convex hulls’ around their bony extremities. Convex hull volume is subsequently regressed against mass to generate predictive models based upon whole skeletons. Our best-performing predictive model is characterized by high correlation coefficients and low mean squared error (a = − 2.31, b = 0.90, r² = 0.97, MSE = 0.0046). When applied to articulated composite skeletons of the dodo (National Museums Scotland, NMS.Z.1993.13; Natural History Museum, NHMUK A.9040 and S/1988.50.1), we estimate eviscerated body masses of 8–10.8 kg. When accounting for missing soft tissues, this may equate to live masses of 10.6–14.3 kg. Mass predictions presented here overlap at the lower end of those previously published, and support recent suggestions of a relatively slim dodo. CT-based reconstructions provide a means of objectively estimating mass and body segment properties of extinct species using whole articulated skeletons.

The potential for biodiversity offsetting to fund effective invasive species control

Compensating for biodiversity losses in 1 location by conserving or restoring biodiversity elsewhere (i.e., biodiversity offsetting) is being used increasingly to compensate for biodiversity losses resulting from development. We considered whether a form of biodiversity offsetting, enhancement offsetting (i.e., enhancing the quality of degraded natural habitats through intensive ecological management), can realistically secure additional funding to control biological invaders at a scale and duration that results in enhanced biodiversity outcomes. We suggest that biodiversity offsetting has the potential to enhance biodiversity values through funding of invasive species control, but it needs to meet 7 key conditions: be technically possible to reduce invasive species to levels that enhance native biodiversity; be affordable; be sufficiently large to compensate for the impact; be adaptable to accommodate new strategic and tactical developments while not compromising biodiversity outcomes; acknowledge uncertainties associated with managing pests; be based on an explicit risk assessment that identifies the cost of not achieving target outcomes; and include financial mechanisms to provide for in-perpetuity funding. The challenge then for conservation practitioners, advocates, and policy makers is to develop frameworks that allow for durable and effective partnerships with developers to realize the full potential of enhancement offsets, which will require a shift away from traditional preservation-focused approaches to biodiversity management.

Reassembling a lost lowland carabid beetle assemblage (Coleoptera) from Kauai, Hawaiian Islands

A late Holocene but prehistoric carabid beetle fauna from the lowland Makauwahi Cave, Kauai, is characterised. Seven extinct species – Blackburnia burneyi, B. cryptipes, B. godzilla, B. menehune, B. mothra, B. ovata and B. rugosa, spp. nov. (tribe Platynini) – represent the first Hawaiian insect species to be newly described from subfossil specimens. Four extant Blackburnia spp. – B. aterrima (Sharp), B. bryophila Liebherr, B. pavida (Sharp), and B. posticata (Sharp) – and three extant species of tribe Bembidiini – Bembidion ignicola Blackburn, B. pacificum Sharp and Tachys oahuensis Blackburn – are also represented. All subfossil fragments are disarticulated, with physical dimensions and cladistic analysis used to associate the major somites – head, prothorax and elytra – for description of the new species. The seven new Makauwahi Cave species support recognition of a lowland area of endemism adjoining Haupu, a low-stature 700 m elevation ridgeline in southern Kauai. Four of the extinct Blackburnia are adelphotaxa to extant species currently found at higher elevations in Kauai. Addition of these lowland specialists to the phylogenetic hypothesis undercuts applicability of the taxon cycle for interpreting evolutionary history of these taxa. Two of the extinct species are Kauai representatives in clades that subsequently colonised younger Hawaiian Islands, enhancing support for the progressive biogeographic colonisation of the archipelago by this lineage. And three of the extinct Blackburnia species comprised larger beetles than those of any extant Kauai Blackburnia, consistent with the evolution of island gigantism in the lowland habitats of Kauai.

Fifteen forms of biodiversity trend in the Anthropocene

Humans are transforming the biosphere in unprecedented ways, raising the important question of how these impacts are changing biodiversity. Here we argue that our understanding of biodiversity trends in the Anthropocene, and our ability to protect the natural world, is impeded by a failure to consider different types of biodiversity measured at different spatial scales. We propose that ecologists should recognize and assess 15 distinct categories of biodiversity trend. We summarize what is known about each of these 15 categories, identify major gaps in our current knowledge, and recommend the next steps required for better understanding of trends in biodiversity.

Imperfect replacement of native species by non-native species as pollinators of endemic Hawaiian plants

Native plant species that have lost their mutualist partners may require non-native pollinators or seed dispersers to maintain reproduction. When natives are highly specialized, however, it appears doubtful that introduced generalists will partner effectively with them. We used visitation observations and pollination treatments (experimental manipulations of pollen transfer) to examine relationships between the introduced, generalist Japanese White-eye (Zosterops japonicus) and 3 endemic Hawaiian plant species (Clermontia parviflora, C. montis-loa, and C. hawaiiensis). These plants are characterized by curved, tubular flowers, apparently adapted for pollination by curve-billed Hawaiian honeycreepers. Z. japonicus were responsible for over 80% of visits to flowers of the small-flowered C. parviflora and the midsize-flowered C. montis-loa. Z. japonicus-visited flowers set significantly more seed than did bagged flowers. Z. japonicus also demonstrated the potential to act as an occasional Clermontia seed disperser, although ground-based frugivory by non-native mammals likely dominates seed dispersal. The large-flowered C. hawaiiensis received no visitation by any birds during observations. Unmanipulated and bagged C. hawaiiensis flowers set similar numbers of seeds. Direct examination of Z. japonicus and Clermontia morphologies suggests a mismatch between Z. japonicus bill morphology and C. hawaiiensis flower morphology. In combination, our results suggest that Z. japonicus has established an effective pollination relationship with C. parviflora and C. montis-loa and that the large flowers of C. hawaiiensis preclude effective visitation by Z. japonicus.

Magnitude and variation of prehistoric bird extinctions in the Pacific

The largest extinction event in the Holocene occurred on Pacific islands, where Late Quaternary fossils reveal the loss of thousands of bird populations following human colonization of the region. However, gaps in the fossil record mean that considerable uncertainty surrounds the magnitude and pattern of these extinctions. We use a Bayesian mark-recapture approach to model gaps in the fossil record and to quantify losses of nonpasserine landbirds on 41 Pacific islands. Two-thirds of the populations on these islands went extinct in the period between first human arrival and European contact, with extinction rates linked to island and species characteristics that increased susceptibility to hunting and habitat destruction. We calculate that human colonization of remote Pacific islands caused the global extinction of close to 1,000 species of nonpasserine landbird alone; nonpasserine seabird and passerine extinctions will add to this total.

Reconstructing past species assemblages reveals the changing patterns and drivers of extinction through time

Predicting future species extinctions from patterns of past extinctions or current threat status relies on the assumption that the taxonomic and biological selectivity of extinction is consistent through time. If the driving forces of extinction change through time, this assumption may be unrealistic. Testing the consistency of extinction patterns between the past and the present has been difficult, because the phylogenetically explicit methods used to model present-day extinction risk typically cannot be applied to the data from the fossil record. However, the detailed historical and fossil records of the New Zealand avifauna provide a unique opportunity to reconstruct a complete, large faunal assemblage for different periods in the past. Using the first complete phylogeny of all known native New Zealand bird species, both extant and extinct, we show how the taxonomic and phylogenetic selectivity of extinction, and biological correlates of extinction, change from the pre-human period through Polynesian and European occupation, to the present. These changes can be explained both by changes in primary threatening processes, and by the operation of extinction filter effects. The variable patterns of extinction through time may confound attempts to identify risk factors that apply across time periods, and to infer future species declines from past extinction patterns and current threat status.

Seed dispersal by a captive corvid: the role of the 'Alalā (Corvus hawaiiensis) in shaping Hawai'i's plant communities

Species loss can lead to cascading effects on communities, including the disruption of ecological processes such as seed dispersal. The endangered 'Alalā (Corvus hawaiiensis), the largest remaining species of native Hawaiian forest bird, was once common in mesic and dry forests on the Big Island of Hawai'i, but today it exists solely in captivity. Prior to its extinction in the wild, the 'Alalā may have helped to establish and maintain native Hawaiian forest communities by dispersing seeds of a wide variety of native plants. In the absence of 'Alalā, the structure and composition of Hawai'i's forests may be changing, and some large-fruited plants may be dispersal limited, persisting primarily as ecological anachronisms. We fed captive 'Alalā a variety of native fruits, documented behaviors relating to seed dispersal, and measured the germination success of seeds that passed through the gut of 'Alalā relative to the germination success of seeds in control groups. 'Alalā ate and carried 14 native fruits and provided germination benefits to several species by ingesting their seeds. Our results suggest that some plants rely heavily on 'Alalā for these services. In captivity, juvenile birds displayed seed dispersal behaviors more often than adult birds for most fruiting plants in our study. We introduced captive 'Alalā to two large-fruited, dry-forest plants, not previously recorded as 'Alalā food resources, but which may once have been part of their natural diet. The seed dispersal behavior that 'Alalā displayed toward these species supports the inclusion of dry and mesic forests in 'Alalā habitat restoration plans and adds weight to the idea that plant dispersal limitation may contribute to the rarity of these plants. Our study provides evidence that 'Alalā have the capacity to play a vital role in maintaining the diversity of fruiting plants in native Hawaiian forests through seed dispersal and enhanced seed germination, thus adding greater urgency to efforts to restore 'Alalā to their former range.

Impacts of biological invasions: what's what and the way forward

Study of the impacts of biological invasions, a pervasive component of global change, has generated remarkable understanding of the mechanisms and consequences of the spread of introduced populations. The growing field of invasion science, poised at a crossroads where ecology, social sciences, resource management, and public perception meet, is increasingly exposed to critical scrutiny from several perspectives. Although the rate of biological invasions, elucidation of their consequences, and knowledge about mitigation are growing rapidly, the very need for invasion science is disputed. Here, we highlight recent progress in understanding invasion impacts and management, and discuss the challenges that the discipline faces in its science and interactions with society.

Increased energy promotes size-based niche availability in marine mollusks

Variation in chemical energy, that is food availability, is posited to cause variation in body size. However, examinations of the relationship are rare and primarily limited to amniotes and zooplankton. Moreover, the relationship between body size and chemical energy may be impacted by phylogenetic history, clade-specific ecology, and heterogeneity of chemical energy in space and time. Considerable work remains to both document patterns in body size over gradients in food availability and understanding the processes potentially generating them. Here, we examine the functional relationship between body size and chemical energy availability over a broad assortment of marine mollusks varying in habitat and mobility. We demonstrate that chemical energy availability is likely driving body size patterns across habitats. We find that lower food availability decreases size-based niche availability by setting hard constraints on maximum size and potentially on minimum size depending on clade-specific ecology. Conversely, higher food availability promotes greater niche availability and potentially promotes evolutionary innovation with regard to size. We posit based on these findings and previous work that increases in chemical energy are important to the diversification of Metazoans through size-mediated niche processes.

Ancient DNA of the extinct lava shearwater (Puffinus olsoni) from the Canary Islands reveals incipient differentiation within the P. puffinus complex

BACKGROUND

The loss of species during the Holocene was, dramatically more important on islands than on continents. Seabirds from islands are very vulnerable to human-induced alterations such as habitat destruction, hunting and exotic predators. For example, in the genus Puffinus (family Procellariidae) the extinction of at least five species has been recorded during the Holocene, two of them coming from the Canary Islands.

METHODOLOGY/PRINCIPAL FINDINGS

We used bones of the two extinct Canary shearwaters (P. olsoni and P. holeae) to obtain genetic data, for use in providing insights into the differentiation process within the genus Puffinus. Although mitochondrial DNA (mtDNA) cytochrome b sequences were successfully retrieved from four Holocene specimens of the extinct Lava shearwater (P. olsoni) from Fuerteventura (Canary Islands), the P. holeae specimens yielded no DNA. Only one haplotype was detected in P. olsoni, suggesting a low genetic diversity within this species.

CONCLUSIONS

The phylogenetic analyses based on the DNA data reveal that: (i) the "Puffinus puffinus complex", an assemblage of species defined using osteological characteristics (P. puffinus, P. olsoni, P. mauretanicus, P. yelkouan and probably P. holeae), shows unresolved phylogenetic relationships; (ii) despite the differences in body size and proportions, P. olsoni and the extant P. puffinus are sister species. Several hypotheses can be considered to explain the incipient differentiation between P. olsoni and P. puffinus.

Current constraints and future directions in estimating coextinction

Coextinction is a poorly quantified phenomenon, but results of recent modeling suggest high losses to global biodiversity through the loss of dependent species when hosts go extinct. There are critical gaps in coextinction theory, and we outline these in a framework to direct future research toward more accurate estimates of coextinction rates. Specifically, the most critical priorities include acquisition of more accurate host data, including the threat status of host species; acquisition of data on the use of hosts by dependent species across a wide array of localities, habitats, and breadth of both hosts and dependents; development of models that incorporate correlates of nonrandom host and dependent extinctions, such as phylogeny and traits that increase extinction-proneness; and determination of whether dependents are being lost before their hosts and adjusting models accordingly. Without synergistic development of better empirical data and more realistic models to estimate the number of cothreatened species and coextinction rates, the contribution of coextinction to global declines in biodiversity will remain unknown and unmanaged.

Consistent ecological selectivity through time in Pacific Island avian extinctions

Understanding the ecological mechanisms that lead to extinction is a central goal of conservation. Can understanding ancient avian extinctions help to predict extinction risk in modern birds? I used classification trees trained on both paleoecological and historical data from islands across the Pacific to determine the ecological traits associated with extinction risk. Intrinsic traits, including endemism, large body size, and certain feeding guilds, were tightly linked with avian extinction over the past 3500 years. Species ecology and phylogeny were better predictors of extinction risk through time than extrinsic or abiotic factors. Although human impacts on birds and their habitats have changed over time, modern endangered birds share many of the same ecological characteristics as victims of previous extinction waves. My use of detailed predictions of extinction risk to identify species potentially in need of conservation attention demonstrates the utility of paleoecological knowledge for modern conservation biology.

Multiple ecological pathways to extinction in mammals

As human population and resource demands continue to grow, biodiversity conservation has never been more critical. About one-quarter of all mammals are in danger of extinction, and more than half of all mammal populations are in decline. A major priority for conservation science is to understand the ecological traits that predict extinction risk and the interactions among those predictors that make certain species more vulnerable than others. Here, using a new database of nearly 4,500 mammal species, we use decision-tree models to quantify the multiple interacting factors associated with extinction risk. We show that the correlates of extinction risk vary widely across mammals and that there are unique pathways to extinction for species with different lifestyles and combinations of traits. We find that risk is relative and that all kinds of mammals, across all body sizes, can be at risk depending on their specific ecologies. Our results increase the understanding of extinction processes, generate simple rules of thumb that identify species at greatest risk, and highlight the potential of decision-tree analyses to inform conservation efforts.

Molecular biogeography and diversification of the endemic terrestrial fauna of the Hawaiian Islands

Oceanic islands have played a central role in biogeography and evolutionary biology. Here, we review molecular studies of the endemic terrestrial fauna of the Hawaiian archipelago. For some groups, monophyly and presumed single origin of the Hawaiian radiations have been confirmed (achatinelline tree snails, drepanidine honeycreepers, drosophilid flies, Havaika spiders, Hylaeus bees, Laupala crickets). Other radiations are derived from multiple colonizations (Tetragnatha and Theridion spiders, succineid snails, possibly Dicranomyia crane flies, Porzana rails). The geographic origins of many invertebrate groups remain obscure, largely because of inadequate sampling of possible source regions. Those of vertebrates are better known, probably because few lineages have radiated, diversity is far lower and morphological taxonomy permits identification of probable source regions. Most birds, and the bat, have New World origins. Within the archipelago, most radiations follow, to some degree, a progression rule pattern, speciating as they colonize newer from older islands sequentially, although speciation often also occurs within islands. Most invertebrates are single-island endemics. However, among multi-island species studied, complex patterns of diversification are exhibited, reflecting heightened dispersal potential (succineids, Dicranomyia). Instances of Hawaiian taxa colonizing other regions are being discovered (Scaptomyza flies, succineids). Taxonomy has also been elucidated by molecular studies (Achatinella snails, drosophilids). While molecular studies on Hawaiian fauna have burgeoned since the mid-1990s, much remains unknown. Yet the Hawaiian fauna is in peril: more than 70 per cent of the birds and possibly 90 per cent of the snails are extinct. Conservation is imperative if this unique fauna is to continue shedding light on profound evolutionary and biogeographic questions.