Using individual‐condition measures to predict the long‐term importance of habitat extent for population persistence

Habitat loss and fragmentation are causing widespread population declines, but identifying how and when to intervene remains challenging. Predicting where extirpations are likely to occur and implementing management actions before losses result may be more cost‐effective than trying to reestablish lost populations. Early indicators of pressure on populations could be used to make such predictions. Previous work conducted in 2009 and 2010 identified that the presence of Eastern Yellow Robins (Eopsaltria australis) in 42 sites in a fragmented region of eastern Australia was unrelated to woodland extent within 500 m of a site, but the robins’ heterophil:lymphocyte (H:L) ratios (an indicator of chronic stress) were elevated at sites with low levels of surrounding woodland. We resurveyed these 42 sites in 2013 and 2014 for robin presence to determine whether the H:L ratios obtained in 2009 and 2010 predicted the locations of extirpations and whether the previous pattern in H:L ratios was an early sign that woodland extent would become an important predictor of occupancy. We also surveyed for robins at 43 additional sites to determine whether current occupancy could be better predicted by landscape context at a larger scale, relevant to dispersal movements. At the original 42 sites, H:L ratios and extirpations were not related, although only 4 extirpations were observed. Woodland extent within 500 m had become a strong predictor of occupancy. Taken together, these results provide mixed evidence as to whether patterns of individual condition can reveal habitat relationships that become evident as local shifts in occupancy occur but that are not revealed by a single snapshot of species distribution. Across all 85 sites, woodland extent at scales relevant to dispersal (5 km) was not related to occurrence. We recommend that conservation actions focus on regenerating areas of habitat large enough to support robin territories rather than increasing connectivity within the landscape.     

Toward quantification of the impact of 21st‐century deforestation on the extinction risk of terrestrial vertebrates

Conservation actions need to be prioritized, often taking into account species’ extinction risk. The International Union for Conservation of Nature (IUCN) Red List provides an accepted, objective framework for the assessment of extinction risk. Assessments based on data collected in the field are the best option, but the field data to base these on are often limited. Information collected through remote sensing can be used in place of field data to inform assessments. Forests are perhaps the best‐studied land‐cover type for use of remote‐sensing data. Using an open‐access 30‐m resolution map of tree cover and its change between 2000 and 2012, we assessed the extent of forest cover and loss within the distributions of 11,186 forest‐dependent amphibians, birds, and mammals worldwide. For 16 species, forest loss resulted in an elevated extinction risk under red‐list criterion A, owing to inferred rapid population declines. This number increased to 23 when data‐deficient species (i.e., those with insufficient information for evaluation) were included. Under red‐list criterion B2, 484 species (855 when data‐deficient species were included) were considered at elevated extinction risk, owing to restricted areas of occupancy resulting from little forest cover remaining within their ranges. The proportion of species of conservation concern would increase by 32.8% for amphibians, 15.1% for birds, and 24.7% for mammals if our suggested uplistings are accepted. Central America, the Northern Andes, Madagascar, the Eastern Arc forests in Africa, and the islands of Southeast Asia are hotspots for these species. Our results illustrate the utility of satellite imagery for global extinction‐risk assessment and measurement of progress toward international environmental agreement targets.     

Combining Measures of Dispersal to Identify Conservation Strategies in Fragmented Landscapes

Abstract: Understanding the way in which habitat fragmentation disrupts animal dispersal is key to identifying effective and efficient conservation strategies. To differentiate the potential effectiveness of 2 frequently used strategies for increasing the connectivity of populations in fragmented landscapes—corridors and stepping stones—we combined 3 complimentary methods: behavioral studies at habitat edges, mark‐recapture, and genetic analyses. Each of these methods addresses different steps in the dispersal process that a single intensive study could not address. We applied the 3 methods to the case study of Atrytonopsis new species 1, a rare butterfly endemic to a partially urbanized stretch of barrier islands in North Carolina (U.S.A.). Results of behavioral analyses showed the butterfly flew into urban and forested areas, but not over open beach; mark‐recapture showed that the butterfly dispersed successfully through short stretches of urban areas (<500 m); and genetic studies showed that longer stretches of forest (>5 km) were a dispersal barrier, but shorter stretches of urban areas (≤5 km) were not. Although results from all 3 methods indicated natural features in the landscape, not urbanization, were barriers to dispersal, when we combined the results we could determine where barriers might arise: forests restricted dispersal for the butterfly only when there were long stretches with no habitat. Therefore, urban areas have the potential to become a dispersal barrier if their extent increases, a finding that may have gone unnoticed if we had used a single approach. Protection of stepping stones should be sufficient to maintain connectivity for Atrytonopsis new species 1 at current levels of urbanization. Our research highlights how the use of complementary approaches for studying animal dispersal in fragmented landscapes can help identify conservation strategies.     

Estimating Extinction Risk with Metapopulation Models of Large‐Scale Fragmentation

Habitat loss is the principal threat to species. How much habitat remains—and how quickly it is shrinking—are implicitly included in the way the International Union for Conservation of Nature determines a species’ risk of extinction. Many endangered species have habitats that are also fragmented to different extents. Thus, ideally, fragmentation should be quantified in a standard way in risk assessments. Although mapping fragmentation from satellite imagery is easy, efficient techniques for relating maps of remaining habitat to extinction risk are few. Purely spatial metrics from landscape ecology are hard to interpret and do not address extinction directly. Spatially explicit metapopulation models link fragmentation to extinction risk, but standard models work only at small scales. Counterintuitively, these models predict that a species in a large, contiguous habitat will fare worse than one in 2 tiny patches. This occurs because although the species in the large, contiguous habitat has a low probability of extinction, recolonization cannot occur if there are no other patches to provide colonists for a rescue effect. For 4 ecologically comparable bird species of the North Central American highland forests, we devised metapopulation models with area‐weighted self‐colonization terms; this reflected repopulation of a patch from a remnant of individuals that survived an adverse event. Use of this term gives extra weight to a patch in its own rescue effect. Species assigned least risk status were comparable in long‐term extinction risk with those ranked as threatened. This finding suggests that fragmentation has had a substantial negative effect on them that is not accounted for in their Red List category. Estimación del Riesgo de Extinción Mediante Modelos Metapoblacionales de Fragmentación a Gran Escala     

Connecting science,policy, and implementation for landscape‐scale habitat connectivity

We examined the links between the science and policy of habitat corridors to better understand how corridors can be implemented effectively. As a case study, we focused on a suite of landscape‐scale connectivity plans in tropical and subtropical Asia (Malaysia, Singapore, and Bhutan). The process of corridor designation may be more efficient if the scientific determination of optimal corridor locations and arrangement is synchronized in time with political buy‐in and establishment of policies to create corridors. Land tenure and the intactness of existing habitat in the region are also important to consider because optimal connectivity strategies may be very different if there are few, versus many, political jurisdictions (including commercial and traditional land tenures) and intact versus degraded habitat between patches. Novel financing mechanisms for corridors include bed taxes, payments for ecosystem services, and strategic forest certifications. Gaps in knowledge of effective corridor design include an understanding of how corridors, particularly those managed by local communities, can be protected from degradation and unsustainable hunting. There is a critical need for quantitative, data‐driven models that can be used to prioritize potential corridors or multicorridor networks based on their relative contributions to long‐term metacommunity persistence.     

Status Assessment of New Zealand's Naturally Uncommon Ecosystems

Abstract: Globally, ecosystems are under increasing anthropogenic pressure; thus, many are at risk of elimination. This situation has led the International Union for Conservation of Nature (IUCN) to propose a quantitative approach to ecosystem‐risk assessment. However, there is a need for their proposed criteria to be evaluated through practical examples spanning a diverse range of ecosystems and scales. We applied the IUCN's ecosystem red‐list criteria, which are based on changes in extent of ecosystems and reductions in ecosystem processes, to New Zealand's 72 naturally uncommon ecosystems. We aimed to test the applicability of the proposed criteria to ecosystems that are naturally uncommon (i.e., those that would naturally occur over a small area in the absence of human activity) and to provide information on the probability of ecosystem elimination so that conservation priorities might be set. We also tested the hypothesis that naturally uncommon ecosystems classified as threatened on the basis of IUCN Red List criteria contain more threatened plant species than those classified as nonthreatened. We identified 18 critically endangered, 17 endangered, and 10 vulnerable ecosystems. We estimated that naturally uncommon ecosystems contained 145 (85%) of mainland New Zealand's taxonomically distinct nationally critical, nationally endangered, and nationally vulnerable plant species, 66 (46%) of which were endemic to naturally uncommon ecosystems. We estimated there was a greater number of threatened plant species (per unit area) in critically endangered ecosystems than in ecosystems classified as nonthreatened. With their high levels of endemism and rapid and relatively well‐documented history of anthropogenic change, New Zealand's naturally uncommon ecosystems provide an excellent case‐study for the ongoing development of international criteria for threatened ecosystems. We suggest that interactions and synergies among decline in area, decline in function, and the scale of application of the criteria be used to improve the IUCN criteria for threatened ecosystems.     

Paying the Extinction Debt in Southern Wisconsin Forest Understories

Abstract: The lack of long‐term baseline data restricts the ability to measure changes in biological diversity directly and to determine its cause. This hampers conservation efforts and limits testing of basic tenets of ecology and conservation biology. We used a historical baseline survey to track shifts in the abundance and distribution of 296 native understory species across 82 sites over 55 years in the fragmented forests of southern Wisconsin. We resurveyed stands first surveyed in the early 1950s to evaluate the influence of patch size and surrounding land cover on shifts in native plant richness and heterogeneity and to evaluate changes in the relative importance of local site conditions versus the surrounding landscape context as drivers of community composition and structure. Larger forests and those with more surrounding forest cover lost fewer species, were more likely to recruit new species, and had lower rates of homogenization than smaller forests in more fragmented landscapes. Nearby urbanization further reduced both alpha and beta understory diversity. Similarly, understory composition depended strongly on local site conditions in the original survey but only weakly reflected the surrounding landscape composition. By 2005, however, the relative importance of these factors had reversed such that the surrounding landscape structure is now a much better predictor of understory composition than are local site conditions. Collectively, these results strongly support the idea that larger intact habitat patches and landscapes better sustain native species diversity and demonstrate that humans play an increasingly important role in driving patterns of native species diversity and community composition.     

A Multispecies Framework for Landscape Conservation Planning

Abstract: Rapidly changing landscapes have spurred the need for quantitative methods for conservation assessment and planning that encompass large spatial extents. We devised and tested a multispecies framework for conservation planning to complement single‐species assessments and ecosystem‐level approaches. Our framework consisted of 4 elements: sampling to effectively estimate population parameters, measuring how human activity affects landscapes at multiple scales, analyzing the relation between landscape characteristics and individual species occurrences, and evaluating and comparing the responses of multiple species to landscape modification. We applied the approach to a community of terrestrial birds across 25,000 km² with a range of intensities of human development. Human modification of land cover, road density, and other elements of the landscape, measured at multiple spatial extents, had large effects on occupancy of the 67 species studied. Forest composition within 1 km of points had a strong effect on occupancy of many species and a range of negative, intermediate, and positive associations. Road density within 1 km of points, percent evergreen forest within 300 m, and distance from patch edge were also strongly associated with occupancy for many species. We used the occupancy results to group species into 11 guilds that shared patterns of association with landscape characteristics. Our multispecies approach to conservation planning allowed us to quantify the trade‐offs of different scenarios of land‐cover change in terms of species occupancy.     

Effects of Recent Environmental Change on Accuracy of Inferences of Extinction Status

Correctly classifying a species as extinct or extant is of critical importance if current rates of biodiversity loss are to be accurately quantified. Observing an extinction event is rare, so in many cases extinction status is inferred using methods based on the analysis of records of historic sighting events. The accuracy of such methods is difficult to test. However, results of recent experiments with microcosm communities suggest that the rate at which a population declines to extinction, potentially driven by varying environmental conditions, may alter one's ability accurately to infer extinction status. We tested how the rate of population decline, driven by historic environmental change, alters the accuracy of 6 commonly applied sighting‐based methods used to infer extinction. We used data from small‐scale experimental communities and recorded wild population extirpations. We assessed how accuracy of the different methods was affected by rate of population decline, search effort, and number of sighting events recorded. Rate of population decline and historic population size of the species affected the accuracy of inferred extinction dates; however, faster declines produced more accurate inferred dates of extinction, but only when population sizes were higher. Optimal linear estimation (OLE) offered the most reliable and robust estimates, though no single method performed best in all situations, and it may be appropriate to use a different method if information regarding historic search efforts is available. OLE provided the most accurate estimates of extinction when the number of sighting events used was >10, and future use of this method should take this into account. Data from experimental populations provide added insight into testing techniques to discern wild extirpation events. Care should be taken designing such experiments so that they mirror closely the abundance dynamics of populations affected by real‐world extirpation events. Efectos del Cambio Ambiental Reciente sobre la Precisión de las Inferencias sobre el Estado de Extinción     

Facilitating climate‐change‐induced range shifts across continental land‐use barriers

Climate changes impose requirements for many species to shift their ranges to remain within environmentally tolerable areas, but near‐continuous regions of intense human land use stretching across continental extents diminish dispersal prospects for many species. We reviewed the impact of habitat loss and fragmentation on species’ abilities to track changing climates and existing plans to facilitate species dispersal in response to climate change through regions of intensive land uses, drawing on examples from North America and elsewhere. We identified an emerging analytical framework that accounts for variation in species' dispersal capacities relative to both the pace of climate change and habitat availability. Habitat loss and fragmentation hinder climate change tracking, particularly for specialists, by impeding both propagule dispersal and population growth. This framework can be used to identify prospective modern‐era climatic refugia, where the pace of climate change has been slower than surrounding areas, that are defined relative to individual species' needs. The framework also underscores the importance of identifying and managing dispersal pathways or corridors through semi‐continental land use barriers that can benefit many species simultaneously. These emerging strategies to facilitate range shifts must account for uncertainties around population adaptation to local environmental conditions. Accounting for uncertainties in climate change and dispersal capabilities among species and expanding biological monitoring programs within an adaptive management paradigm are vital strategies that will improve species' capacities to track rapidly shifting climatic conditions across landscapes dominated by intensive human land use.     

Effect of Rotational Shepherding on Demographic and Genetic Connectivity of Calcareous Grassland Plants

Response to habitat fragmentation may not be generalized among species, in particular for plant communities with a variety of dispersal traits. Calcareous grasslands are one of the most species‐rich habitats in Central Europe, but abandonment of traditional management has caused a dramatic decline of calcareous grassland species. In the Southern Franconian Alb in Germany, reintroduction of rotational shepherding in previously abandoned grasslands has restored species diversity, and it has been suggested that sheep support seed dispersal among grasslands. We tested the effect of rotational shepherding on demographic and genetic connectivity of calcareous grassland specialist plants and whether the response of plant populations to shepherding was limited to species dispersed by animals (zoochory). Specifically, we tested competing dispersal models and source and focal patch properties to explain landscape connectivity with patch‐occupancy data of 31 species. We fitted the same connectivity models to patch occupancy and nuclear microsatellite data for the herb Dianthus carthusianorum (Carthusian pink). For 27 species, patch connectivity was explained by dispersal by rotational shepherding regardless of adaptations to zoochory, whereas population size (16% species) and patch area (0% species) of source patches were not important predictors of patch occupancy in most species. [Correction made after online publication, February 25, 2014: Population size and patch area percentages were mistakenly inverted, and have now been fixed.] Microsite diversity of focal patches significantly increased the model variance explained by patch occupancy in 90% of the species. For D. carthusianorum, patch connectivity through rotational shepherding explained both patch occupancy and population genetic diversity. Our results suggest shepherding provides dispersal for multiple plant species regardless of their dispersal adaptations and thus offers a useful approach to restore plant diversity in fragmented calcareous grasslands. Efectos del Pastoreo Rotacional sobre la Conectividad Genética y Demográfica de Plantas de Pastizales Calcáreos     

The problem of estimating recent genetic connectivity in a changing world

Accurate understanding of population connectivity is important to conservation because dispersal can play an important role in population dynamics, microevolution, and assessments of extirpation risk and population rescue. Genetic methods are increasingly used to infer population connectivity because advances in technology have made them more advantageous (e.g., cost effective) relative to ecological methods. Given the reductions in wildlife population connectivity since the Industrial Revolution and more recent drastic reductions from habitat loss, it is important to know the accuracy of and biases in genetic connectivity estimators when connectivity has declined recently. Using simulated data, we investigated the accuracy and bias of 2 common estimators of migration (movement of individuals among populations) rate. We focused on the timing of the connectivity change and the magnitude of that change on the estimates of migration by using a coalescent‐based method (Migrate‐n) and a disequilibrium‐based method (BayesAss). Contrary to expectations, when historically high connectivity had declined recently: (i) both methods over‐estimated recent migration rates; (ii) the coalescent‐based method (Migrate‐n) provided better estimates of recent migration rate than the disequilibrium‐based method (BayesAss); (iii) the coalescent‐based method did not accurately reflect long‐term genetic connectivity. Overall, our results highlight the problems with comparing coalescent and disequilibrium estimates to make inferences about the effects of recent landscape change on genetic connectivity among populations. We found that contrasting these 2 estimates to make inferences about genetic‐connectivity changes over time could lead to inaccurate conclusions.     

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. Remplazo Imperfecto de Especies Nativas por Especies No‐Nativas como Polinizadores de Plantas Endémicas de Hawaii     

Meta‐Analysis of the Effects of Human Disturbance on Seed Dispersal by Animals

Animal‐mediated seed dispersal is important for sustaining biological diversity in forest ecosystems, particularly in the tropics. Forest fragmentation, hunting, and selective logging modify forests in myriad ways and their effects on animal‐mediated seed dispersal have been examined in many case studies. However, the overall effects of different types of human disturbance on animal‐mediated seed dispersal are still unknown. We identified 35 articles that provided 83 comparisons of animal‐mediated seed dispersal between disturbed and undisturbed forests; all comparisons except one were conducted in tropical or subtropical ecosystems. We assessed the effects of forest fragmentation, hunting, and selective logging on seed dispersal of fleshy‐fruited tree species. We carried out a meta‐analysis to test whether forest fragmentation, hunting, and selective logging affected 3 components of animal‐mediated seed dispersal: frugivore visitation rate, number of seeds removed, and distance of seed dispersal. Forest fragmentation, hunting, and selective logging did not affect visitation rate and were marginally associated with a reduction in seed‐dispersal distance. Hunting and selective logging, but not fragmentation, were associated with a large reduction in the number of seeds removed. Fewer seeds of large‐seeded than of small‐seeded tree species were removed in hunted or selectively logged forests. A plausible explanation for the consistently negative effects of hunting and selective logging on large‐seeded plant species is that large frugivores, as the predominant seed dispersers for large‐seeded plant species, are the first animals to be extirpated from hunted or logged forests. The reduction in forest area after fragmentation appeared to have weaker effects on frugivore communities and animal‐mediated seed dispersal than hunting and selective logging. The differential effects of hunting and selective logging on large‐ and small‐seeded tree species underpinned case studies that showed disrupted plant‐frugivore interactions could trigger a homogenization of seed traits in tree communities in hunted or logged tropical forests. Meta Análisis de los Efectos de la Perturbación Humana sobre la Dispersión de Semillas por Animales     

Applying network theory to prioritize multispecies habitat networks that are robust to climate and land‐use change

Designing connected landscapes is among the most widespread strategies for achieving biodiversity conservation targets. The challenge lies in simultaneously satisfying the connectivity needs of multiple species at multiple spatial scales under uncertain climate and land‐use change. To evaluate the contribution of remnant habitat fragments to the connectivity of regional habitat networks, we developed a method to integrate uncertainty in climate and land‐use change projections with the latest developments in network‐connectivity research and spatial, multipurpose conservation prioritization. We used land‐use change simulations to explore robustness of species’ habitat networks to alternative development scenarios. We applied our method to 14 vertebrate focal species of periurban Montreal, Canada. Accounting for connectivity in spatial prioritization strongly modified conservation priorities and the modified priorities were robust to uncertain climate change. Setting conservation priorities based on habitat quality and connectivity maintained a large proportion of the region's connectivity, despite anticipated habitat loss due to climate and land‐use change. The application of connectivity criteria alongside habitat‐quality criteria for protected‐area design was efficient with respect to the amount of area that needs protection and did not necessarily amplify trade‐offs among conservation criteria. Our approach and results are being applied in and around Montreal and are well suited to the design of ecological networks and green infrastructure for the conservation of biodiversity and ecosystem services in other regions, in particular regions around large cities, where connectivity is critically low.     

Relation between extinction and assisted colonization of plants in the arctic‐alpine and boreal regions

Assisted colonization of vascular plants is considered by many ecologists an important tool to preserve biodiversity threatened by climate change. I argue that assisted colonization may have negative consequences in arctic‐alpine and boreal regions. The observed slow movement of plants toward the north has been an argument for assisted colonization. However, these range shifts may be slow because for many plants microclimatic warming (ignored by advocates of assisted colonization) has been smaller than macroclimatic warming. Arctic‐alpine and boreal plants may have limited possibilities to disperse farther north or to higher elevations. I suggest that arctic‐alpine species are more likely to be driven to extinction because of competitive exclusion by southern species than by increasing temperatures. If so, the future existence of arctic‐alpine and boreal flora may depend on delaying or preventing the migration of plants toward the north to allow northern species to evolve to survive in a warmer climate. In the arctic‐alpine region, preventing the dispersal of trees and shrubs may be the most important method to mitigate the negative effects of climate change. The purported conservation benefits of assisted colonization should not be used to promote the migration of invasive species by forestry.     

Taxonomic and Geographic Patterns of Decline for Threatened and Endangered Species in the United States

Abstract: Species listed under the U.S. Endangered Species Act (i.e., listed species) have declined to the point that the probability of their extinction is high. The decline of these species, however, may manifest itself in different ways, including reductions in geographic range, number of populations, or overall abundance. Understanding the pattern of decline can help managers assess extinction probability and define recovery objectives. Although quantitative data on changes in geographic range, number of populations, and abundance usually do not exist for listed species, more often qualitative data can be obtained. We used qualitative data in recovery plans for federally listed species to determine whether each listed species declined in range size, number of populations, or abundance relative to historical levels. We calculated the proportion of listed species in each state (or equivalent) that declined in each of those ways. Nearly all listed species declined in abundance, and range size or number of populations declined in approximately 80% of species for which those data were available. Patterns of decline, however, differed taxonomically and geographically. Declines in range were more common among vertebrates than plants, whereas population extirpations were more common among plants. Invertebrates had high incidence of range and population declines. Narrowly distributed plants and invertebrates may be subject to acute threats that may result in population extirpations, whereas vertebrates may be affected by chronic threats that reduce the extent and size of populations. Additionally, in the eastern United States and U.S. coastal areas, where the level of land conversion is high, a greater percentage of species’ ranges declined and more populations were extirpated than in other areas. Species in the Southwest, especially plants, had fewer range and population declines than other areas. Such relations may help in the selection of species’ recovery criteria.     

Phylogeography and Limited Genetic Connectivity in the Endangered Boring Giant Clam across the Coral Triangle

Abstract: The Coral Triangle is the global center of marine biodiversity; however, its coral reefs are critically threatened. Because of the bipartite life history of many marine species with sedentary adults and dispersive pelagic larvae, designing effective marine protected areas requires an understanding of patterns of larval dispersal and connectivity among geographically discrete populations. We used mtDNA sequence data to examine patterns of genetic connectivity in the boring giant clam (Tridacna crocea) in an effort to guide conservation efforts within the Coral Triangle. We collected an approximately 485 base pair fragment of mtDNA cytochrome c oxidase 1 (CO1) from 414 individuals at 26 sites across Indonesia. Genetic structure was strong between regions (φ_ST=0.549, p < 0.00001) with 3 strongly supported clades: one restricted to western Sumatra, another distributed across central Indonesia, and a third limited to eastern Indonesia and Papua. Even within the single largest clade, small but significant genetic structure was documented (φ_ST=0.069, p < 0.00001), which indicates limited gene flow within and among phylogeographic regions. Significant patterns of isolation by distance indicated an average dispersal distance of only 25–50 km, which is far below dispersal predictions of 406–708 km derived from estimates of passive dispersal over 10 days via surface currents. The strong regional genetic structure we found indicates potent limits to genetic and demographic connectivity for this species throughout the Coral Triangle and provides a regional context for conservation planning. The recovery of 3 distinct evolutionarily significant units within a well‐studied taxonomic group suggests that biodiversity in this region may be significantly underestimated and that Tridacna taxa may be more endangered than currently recognized.     

Spatial,socio‐economic,and ecological implications of incorporating minimum size constraints in marine protected area network design

Marine protected areas (MPAs) are the cornerstone of most marine conservation strategies, but the effectiveness of each one partly depends on its size and distance to other MPAs in a network. Despite this, current recommendations on ideal MPA size and spacing vary widely, and data are lacking on how these constraints might influence the overall spatial characteristics, socio‐economic impacts, and connectivity of the resultant MPA networks. To address this problem, we tested the impact of applying different MPA size constraints in English waters. We used the Marxan spatial prioritization software to identify a network of MPAs that met conservation feature targets, whilst minimizing impacts on fisheries; modified the Marxan outputs with the MinPatch software to ensure each MPA met a minimum size; and used existing data on the dispersal distances of a range of species found in English waters to investigate the likely impacts of such spatial constraints on the region's biodiversity. Increasing MPA size had little effect on total network area or the location of priority areas, but as MPA size increased, fishing opportunity cost to stakeholders increased. In addition, as MPA size increased, the number of closely connected sets of MPAs in networks and the average distance between neighboring MPAs decreased, which consequently increased the proportion of the planning region that was isolated from all MPAs. These results suggest networks containing large MPAs would be more viable for the majority of the region's species that have small dispersal distances, but dispersal between MPA sets and spill‐over of individuals into unprotected areas would be reduced. These findings highlight the importance of testing the impact of applying different MPA size constraints because there are clear trade‐offs that result from the interaction of size, number, and distribution of MPAs in a network.     

Effects of Native and Non‐Native Vertebrate Mutualists on Plants

Abstract: Extinctions can leave species without mutualist partners and thus potentially reduce their fitness. In cases where non‐native species function as mutualists, mutualism disruption associated with species’ extinction may be mitigated. To assess the effectiveness of mutualist species with different origins, we conducted a meta‐analysis in which we compared the effectiveness of pollination and seed‐dispersal functions of native and non‐native vertebrates. We used data from 40 studies in which a total of 34 non‐native vertebrate mutualists in 20 geographic locations were examined. For each plant species, opportunistic non‐native vertebrate pollinators were generally less effective mutualists than native pollinators. When native mutualists had been extirpated, however, plant seed set and seedling performance appeared elevated in the presence of non‐native mutualists, although non‐native mutualists had a negative overall effect on seed germination. These results suggest native mutualists may not be easily replaced. In some systems researchers propose taxon substitution or the deliberate introduction of non‐native vertebrate mutualists to reestablish mutualist functions such as pollination and seed dispersal and to rescue native species from extinction. Our results also suggest that in places where all native mutualists are extinct, careful taxon substitution may benefit native plants at some life stages.