The 'island syndrome' is an alternative state

Aim: In the half-century since publication of the Theory of Island Biology, ecologists have come to recognize the importance of predation as a decisive determinant of alternate states in many ecosystems. Island species are notorious for their vulnerability to introduced predators, yet the strength of island predator regimes has not been fully incorporated into our understanding of the forces that structure island consumer communities. Location: The Greater and Lesser Antilles. Taxon Birds and Anolis lizards. Methods: Field surveys of sclerophyll and rainforest sites on islands ranging in size from 3.5 km(2) Terre-de-Haut to 76,000 km(2) Hispaniola. Results: Evidence gathered in the 1970s and 1980s shows that Antillean anoles live at higher densities on fewer resources, grow more slowly, reproduce later and live longer than mainland counterparts in conformity with the 'island syndrome'. Data from this period show that Antillean bird communities display density overcompensation, community saturation, size-structured foraging guilds, low species diversity and low species packing, all traits consistent with the island syndrome and a regime of low predation and intense competition. Mainland species and communities display none of these features. Main conclusions: I propose that the island syndrome is an alternative state that distinguishes low-predation island communities from high-predation mainland counterparts. It follows that strong mainland predation regimes tend to prevent island species from colonizing. Conversely, invasion-resistant, size-structured island communities, despite low species diversity, prevent mainland species from colonizing islands. These predictions are experimentally testable with Anolis lizards and, if confirmed, could set island biogeography on a new course

Do Community-Managed Forests Work? A Biodiversity Perspective

Community-managed reserves (CMRs) comprise the fastest-growing category of protected areas throughout the tropics. CMRs represent a compromise between advocates of nature conservation and advocates of human development. We ask whether CMRs succeed in achieving the goals of either. A fixed reserve area can produce only a finite resource supply, whereas human populations exploiting them tend to expand rapidly while adopting high-impact technologies to satisfy rising aspirations. Intentions behind the establishment of CMRs may be admirable, but represent an ideal rarely achieved. People tied to the natural forest subsist on income levels that are among the lowest in the Amazon. Limits of sustainable harvesting are often low and rarely known prior to reserve creation or respected thereafter, and resource exhaustion predictably follows. Unintended consequences typically emerge, such as overhunting of the seed dispersers, pollinators, and other animals that provide services essential to perpetuating the forest. CMRs are a low priority for governments, so mostly operate without enforcement, a laxity that encourages illegal forest conversion. Finally, the pull of markets can alter the “business plan” of a reserve overnight, as inhabitants switch to new activities. The reality is that we live in a hyperdynamic world of accelerating change in which past assumptions must continually be re-evaluated

Do Community-Managed Forests Work? A Biodiversity Perspective

Community-managed reserves (CMRs) comprise the fastest-growing category of protected areas throughout the tropics. CMRs represent a compromise between advocates of nature conservation and advocates of human development. We ask whether CMRs succeed in achieving the goals of either. A fixed reserve area can produce only a finite resource supply, whereas human populations exploiting them tend to expand rapidly while adopting high-impact technologies to satisfy rising aspirations. Intentions behind the establishment of CMRs may be admirable, but represent an ideal rarely achieved. People tied to the natural forest subsist on income levels that are among the lowest in the Amazon. Limits of sustainable harvesting are often low and rarely known prior to reserve creation or respected thereafter, and resource exhaustion predictably follows. Unintended consequences typically emerge, such as overhunting of the seed dispersers, pollinators, and other animals that provide services essential to perpetuating the forest. CMRs are a low priority for governments, so mostly operate without enforcement, a laxity that encourages illegal forest conversion. Finally, the pull of markets can alter the “business plan” of a reserve overnight, as inhabitants switch to new activities. The reality is that we live in a hyperdynamic world of accelerating change in which past assumptions must continually be re-evaluated

Why do dolphins form mixed-species associations in the Azores ?

Mixed-species associations are temporary associations between individuals of different species that are often observed in birds, primates and cetaceans. They have been interpreted as a strategy to reduce predation risk, enhance foraging success and/or provide a social advantage. In the archipelago of the Azores, four species of dolphins are commonly involved in mixed-species associations: the common dolphin, Delphinus delphis, the bottlenose dolphin, Tursiops truncatus, the striped dolphin, Stenella coeruleoalba, and the spotted dolphin, Stenella frontalis. In order to understand the reasons why dolphins associate, we analysed field data collected since 1999 by research scientists and trained observers placed onboard fishing vessels. In total, 113 mixed-species groups were observed out of 5720 sightings. The temporal distribution, habitat (water depth, distance to the coast), behaviour (i.e. feeding, travelling, socializing), size and composition of mixed-species groups were compared with those of single-species groups. Results did not support the predation avoidance hypothesis and gave little support to the social advantage hypothesis. The foraging advantage hypothesis was the most convincing. However, the benefits of mixed-species associations appeared to depend on the species. Associations were likely to be opportunistic in the larger bottlenose dolphin, while there seemed to be some evolutionary constraints favouring associations in the rarer striped dolphin. Comparison with previous studies suggests that the formation of mixed-species groups depends on several environmental factors, and therefore may constitute an adaptive response

Selfish or altruistic? An analysis of alarm call function in wild capuchin monkeys, Cebus apella nigritus

Alarm calls facilitate some antipredatory benefits of group living but may endanger the caller by attracting the predator's attention. A number of hypotheses invoking kin selection and individual selection have been proposed to explain how such behaviour could evolve. This study tests eight hypotheses for alarm call evolution by examining the responses of tufted capuchin monkeys to models of felids, perched raptors and vipers. Specifically, this study examines: (1) differences between individuals in their propensity to call in response to different threat types, (2) whether there is an audience effect for alarm calling and (3) the response of conspecifics to alarms. Results indicate that the benefits likely to be afforded to the caller vary with stimulus type. Alarm calling in response to felids is most likely selfish, with calls apparently directed towards both the predator and potential conspecific mobbers. Alarm calling in response to vipers attracts additional mobbers as well, but also appears to be driven by kin selection in the case of males and parental care benefits in the case of females. Alarm responses to perched raptors are rare, but seem to be selfish, with callers benefiting by recruiting additional mobbers

Science for a wilder Anthropocene: synthesis and future directions for trophic rewilding research

Trophic rewilding is an ecological restoration strategy that uses species introductions to restore top-down trophic interactions and associated trophic cascades to promote self-regulating biodiverse ecosystems. Given the importance of large animals in trophic cascades and their widespread losses and resulting trophic downgrading, it often focuses on restoring functional megafaunas. Trophic rewilding is increasingly being implemented for conservation, but remains controversial. Here, we provide a synthesis of its current scientific basis, highlighting trophic cascades as the key conceptual framework, discussing the main lessons learned from ongoing rewilding projects, systematically reviewing the current literature, and highlighting unintentional rewilding and spontaneous wildlife comebacks as underused sources of information. Together, these lines of evidence show that trophic cascades may be restored via species reintroductions and ecological replacements. It is clear, however, that megafauna effects may be affected by poorly understood trophic complexity effects and interactions with landscape settings, human activities, and other factors. Unfortunately, empirical research on trophic rewilding is still rare, fragmented, and geographically biased, with the literature dominated by essays and opinion pieces. We highlight the need for applied programs to include hypothesis testing and science-based monitoring, and outline priorities for future research, notably assessing the role of trophic complexity, interplay with landscape settings, land use, and climate change, as well as developing the global scope for rewilding and tools to optimize benefits and reduce human–wildlife conflicts. Finally, we recommend developing a decision framework for species selection, building on functional and phylogenetic information and with attention to the potential contribution from synthetic biology

Concerted changes in tropical forest structure and dynamics: evidence from 50 South American long-term plots

Several widespread changes in the ecology of old-growth tropical forests have recently been documented for the late twentieth century, in particular an increase in stem turnover (pan-tropical), and an increase in above-ground biomass (neotropical). Whether these changes are synchronous and whether changes in growth are also occurring is not known. We analysed stand-level changes within 50 long-term. monitoring plots from across South America spanning 1971-2002. We show that: (i) basal area (BA: sum of the cross-sectional areas of all trees in a plot) increased significantly over time (by 0.10 +/- 0.04 m(2) ha(-1) yr(-1), mean +/- 95% CI); as did both (ii) stand-level BA growth rates (sum of the increments of BA of surviving trees and BA of new trees that recruited into a plot); and (iii) stand-level BA mortality rates (sum of the cross-sectional areas of all trees that died in a plot). Similar patterns were observed on a per-stem basis: (i) stem density (number of stems per hectare; 1 hectare is 10(4) m(2)) increased significantly over time (0.94 +/- 0.63 stems ha(-1) yr(-1)); as did both (ii) stem recruitment rates; and (iii) stem mortality rates. In relative terms, the pools of BA and stem density increased by 0.38 +/- 0.15% and 0.18 +/- 0.12% yr(-1), respectively. The fluxes into and out of these pools-stand-level BA growth, stand-level BA mortality, stem recruitment and stem mortality rates-increased, in relative terms, by an order of magnitude more. The gain terms (BA growth, stem recruitment) consistently exceeded the loss terms (BA loss, stem mortality) throughout the period, suggesting that whatever process is driving these changes was already acting before the plot network was established. Large long-term increases in stand-level BA growth and simultaneous increases in stand BA and stem density imply a continent-wide increase in resource availability which is increasing net primary productivity and altering forest dynamics. Continent-wide changes in incoming solar radiation, and increases in atmospheric concentrations of CO2 and air temperatures may have increased resource supply over recent decades, thus causing accelerated growth and increased dynamism across the world's largest tract of tropical forest

Research and in situ conservation of owl monkeys enhances environmental law enforcement at the Colombian-Peruvian border

This study reports on impacts of illegal trade in owl monkeys (Aotus nancymaae, A. vociferans) for the biomedical research market in the Colombian-Peruvian Amazonian border. Through freedom of information requests and interviews with hunters we found that 912 owl monkeys, including A. nancymaae captured in Peru, were trapped over a 3-month period in 2012 to supply a malaria research facility based in Leticia, Colombia, which had trapping permits for the use of only 800 A. vociferans annually yet experimentation took place using A. nancymaae. High levels of extraction in Peru have had population-level impacts with significantly lower densities of Aotus spp. (3-24individuals/km2) compared to Colombian sites with low hunting pressure (26-44individuals/km2). Post-experimental release of this species in Colombian territory has created a new distribution whose status and impacts on resident populations of A. vociferans remain unknown. The trapping method has also had environmental impact, with loss of over 65,000 trees (including sleeping sites), annually. As Aotus species are registered under the Convention of International Trade in Endangered Species of Wild Fauna and Flora (CITES) Appendix II, international trade requires official permission and evidence that extraction does not impact wild populations. However, no official records exist and CITES legislation has failed, due principally to a lack of appropriate monitoring by national authorities responsible for compliance. Of further concern is that we had previously documented and reported the illegal trade to the appropriate governmental authorities yet still no action was taken-as demonstrated by the continuing trade in 2013. Enforcement eventually occurred when a non-governmental organization initiated legal action against organizations responsible. A successful second instance ruling by the Colombian State's Council in 2013 revoked trapping permits. Using the trade in owl monkeys as a case study we consider implementation, compliance, and enforcement of CITES in the border area to identify mechanisms to improve enforcement of environmental legislation. Am. J. Primatol. 76:658-669, 2014. © 2014 Wiley Periodicals, Inc

Widespread forest vertebrate extinctions induced by a mega hydroelectric dam in lowland Amazonia

Mega hydropower projects in tropical forests pose a major emergent threat to terrestrial and freshwater biodiversity worldwide. Despite the unprecedented number of existing, underconstruction and planned hydroelectric dams in lowland tropical forests, long-term effects on biodiversity have yet to be evaluated. We examine how medium and large-bodied assemblages of terrestrial and arboreal vertebrates (including 35 mammal, bird and tortoise species) responded to the drastic 26-year post-isolation history of archipelagic alteration in landscape structure and habitat quality in a major hydroelectric reservoir of Central Amazonia. The Balbina Hydroelectric Dam inundated 3,129 km2 of primary forests, simultaneously isolating 3,546 land-bridge islands. We conducted intensive biodiversity surveys at 37 of those islands and three adjacent continuous forests using a combination of four survey techniques, and detected strong forest habitat area effects in explaining patterns of vertebrate extinction. Beyond clear area effects, edge-mediated surface fire disturbance was the most important additional driver of species loss, particularly in islands smaller than 10 ha. Based on species-area models, we predict that only 0.7% of all islands now harbor a species-rich vertebrate assemblage consisting of ≥80% of all species. We highlight the colossal erosion in vertebrate diversity driven by a man-made dam and show that the biodiversity impacts of mega dams in lowland tropical forest regions have been severely overlooked. The geopolitical strategy to deploy many more large hydropower infrastructure projects in regions like lowland Amazonia should be urgently reassessed, and we strongly advise that long-term biodiversity impacts should be explicitly included in pre-approval environmental impact assessments

Palm fruit colours are linked with the broad-scale distribution and diversification of primate colour vision systems

A long-standing hypothesis in ecology and evolution is that trichromatic colour vision (the ability to distinguish red from green) in frugivorous primates has evolved as an adaptation to detect conspicuous (reddish) fruits. This could provide a competitive advantage over dichromatic frugivores which cannot distinguish reddish colours from a background of green foliage. Using an unprecedented global data set, we test this hypothesis by combining colour vision, distribution and phylogenetic data for >400 primate species with fruit colour data for >1700 palm species, i.e. keystone fruit resources for tropical frugivores. Structural equation models reveal that species richness of trichromatic primates increases with the proportion of palm species that have conspicuous fruits, especially in subtropical African forests. In contrast, species richness of trichromats in Asia and the Americas is not positively associated with conspicuous palm fruit colours. Macroevolutionary analyses further indicate rapid and synchronous radiations of trichromats and conspicuous palms on the African mainland starting 10 million years ago. These results suggest that the distribution and diversification of African trichromatic primates is strongly linked to the relative availability of conspicuous (vs. cryptic) palm fruits, and that interactions between primates and palms are impacted by the co- evolutionary dynamics of primate colour vision systems and palm fruit colours