Changes in Patch Features May Exacerbate or Compensate for the Effect of Habitat Loss on Forest Bird Populations

One and a half centuries after Darwin visited Chiloe Island, what he described as “…an island covered by one great forest…” has lost two-thirds of its forested areas. At this biodiversity hotspot, forest surface is becoming increasingly fragmented due to unregulated logging, clearing for pastures and replacement by exotic tree plantations. Decrease in patch size, increased isolation and “edge effects” can influence the persistence of forest species in remnant fragments. We assessed how these variables affect local density for six forest birds, chosen to include the most important seed dispersers (four species) and bird pollinators (two species, one of which acts also as seed disperser), plus the most common insectivore (Aphrastura spinicauda). Based on cue-count point surveys (8 points per fragment), we estimated bird densities for each species in 22 forest fragments of varying size, shape, isolation and internal-habitat structure (e.g. tree size and epiphyte cover). Bird densities varied with fragment connectivity (three species) and shape (three species), but none of the species was significantly affected by patch size. Satellite image analyses revealed that, from 1985 to 2008, forested area decreased by 8.8% and the remaining forest fragments became 16% smaller, 58–73% more isolated and 11–50% more regular. During that period, bird density estimates for the northern part of Chiloé (covering an area of 1214.75 km2) decreased for one species (elaenia), increased for another two (chucao and hummingbird) and did not vary for three (rayadito, thrust and blackbird). For the first three species, changes in patch features respectively exacerbated, balanced and overcame the effects of forest loss on bird population size (landscape-level abundance). Hence, changes in patch features can modulate the effect of habitat fragmentation on forest birds, suggesting that spatial planning (guided by spatially-explicit models) can be an effective tool to facilitate their conservation

Rats and Seabirds: Effects of Egg Size on Predation Risk and the Potential of Conditioned Taste Aversion as a Mitigation Method

Seabirds nesting on islands are threatened by invasive rodents, such as mice and rats, which may attack eggs, chicks and even adults. The low feasibility of rat eradications on many islands makes the development of alternate control plans necessary. We used a combination of field experiments on a Mediterranean island invaded by black rats (Rattus rattus) to evaluate (1) the predation risk posed to different-sized seabird eggs and (2), the potential of two deterrent methods (electronic and chemical) to reduce its impact. Rats were able to consume eggs of all sizes (12 to 68 g), but survival increased 13 times from the smallest to the largest eggs (which also had more resistant eggshells). Extrapolation to seabird eggs suggests that the smallest species (Hydrobates pelagicus) suffer the most severe predation risk, but even the largest (Larus michahellis) could suffer >60% mortality. Nest attack was not reduced by the deterrents. However, chemical deterrence (conditioned taste aversion by lithium chloride) slowed the increase in predation rate over time, which resulted in a three-fold increase in egg survival to predation as compared to both control and electronic deterrence. At the end of the experimental period, this effect was confirmed by a treatment swap, which showed that conferred protection remains at least 15 days after cessation of the treatment. Results indicate that small seabird species are likely to suffer severe rates of nest predation by rats and that conditioned taste aversion, but not electronic repellents, may represent a suitable method to protect colonies when eradication or control is not feasible or cost-effective. © 2013 Latorre et al.Funds were provided by the Environment and Nature Council of the Balearic Government (project DRAGORAT; Sa Dragonera Natural Park's research grants, IX Edition, 2007). ARL received funding support from the Spanish Scientific Research Council (JAEDoc program, co-funded by the European Social Fund). The Spanish Ministry of Science and Innovation also supported this work by the awarded project SEAGRAPE, ref. CGL2011-30249Peer Reviewe

Selective Pressure along a Latitudinal Gradient Affects Subindividual Variation in Plants

Individual plants produce repeated structures such as leaves, flowers or fruits, which, although belonging to the same genotype, are not phenotypically identical. Such subindividual variation reflects the potential of individual genotypes to vary with micro-environmental conditions. Furthermore, variation in organ traits imposes costs to foraging animals such as time, energy and increased predation risk. Therefore, animals that interact with plants may respond to this variation and affect plant fitness. Thus, phenotypic variation within an individual plant could be, in part, an adaptive trait. Here we investigated this idea and we found that subindividual variation of fruit size of Crataegus monogyna, in different populations throughout the latitudinal gradient in Europe, was explained at some extent by the selective pressures exerted by seed-dispersing birds. These findings support the hypothesis that within-individual variation in plants is an adaptive trait selected by interacting animals which may have important implications for plant evolution. © 2013 Sobral et al.This work was supported by the Spanish Ministry of Science and Education (project CGL2005-03826) and the European Commission (FEDER program). M.S. was the recipient of a María Barbeito fellowship (Galicia regional government, Spain) and a Fundación Pedro Barrié de la Maza grant. A.R.L. received financial support from the Spanish Research Council (JAEDoc program, partially funded by the European Social Fund) during the preparation of the manuscriptPeer Reviewe

Selective pressure along a latitudinal gradient affects subindividual variation in plants

Individual plants produce repeated structures such as leaves, flowers or fruits, which, although belonging to the same genotype, are not phenotypically identical. Such subindividual variation reflects the potential of individual genotypes to vary with micro-environmental conditions. Furthermore, variation in organ traits imposes costs to foraging animals such as time, energy and increased predation risk. Therefore, animals that interact with plants may respond to this variation and affect plant fitness. Thus, phenotypic variation within an individual plant could be, in part, an adaptive trait. Here we investigated this idea and we found that subindividual variation of fruit size of Crataegus monogyna, in different populations throughout the latitudinal gradient in Europe, was explained at some extent by the selective pressures exerted by seed-dispersing birds. These findings support the hypothesis that within-individual variation in plants is an adaptive trait selected by interacting animals which may have important implications for plant evolution.This work was supported by the Spanish Ministry of Science and Education (project CGL2005-03826) and the European Commission (FEDER program). M.S. was the recipient of a María Barbeito fellowship (Galicia regional government, Spain) and a Fundación Pedro Barrié de la Maza grant. A.R.L. received financial support from the Spanish Research Council (JAEDoc program, partially funded by the European Social Fund) during the preparation of the manuscriptS

Interactions between the Black Redstart (Phoenicurus ochruros) and St. Lucie Cherry (Prunus mahaleb) in rocky habitats

We investigated interactions between the Black Redstart (Phoenicurus ochruros) and the St. Lucie cherry (Prunus mahaleb) in two rocky areas in north west Spain. Black Redstarts are responsible for about 30 % of P. mahaleb fruit consumption in these areas (604 of a total of 1854 observations of birds feeding; 56 trees, 4 years). On average 14 % of food deliveries to nestlings comprised P. mahaleb fruits (total 8 nests, 3 years; range for individual nests 7-28 %) . The proportion of deliveries comprising fruits was higher during the second half of the nestling period than during the first half. Birds generally alighted on rock after leaving P. mahaleb plants (74 % of cases). Nine-month seed-survival experiments performed in the study area indicate significant variation among the three substrate types considered (grass, rock, rock-under-nest)Nous avons étudié les interactions entre le Rougequeue noir (Phoenicurus ochruros) et le Bois de Sainte Lucie (Prunus mahaleb) dans deux zones rocheuses du nord-ouest de l'Espagne. Les Rougequeues noirs sont responsables d'à peu près 30 % de la consommation des fruits de Prunus mahaleb dans ces zones (604 observations sur un total de 1 854 données d'oiseaux s'alimentant sur 56 arbres, en 4 ans). En moyenne, 14 % des apports de nourriture aux poussins comportaient des fruits de Prunus mahaleb (7 à 28 % pour 8 nids en 3 ans). La proportion des becquées incluant des fruits était plus élevée durant la seconde moitié de la période de nourrissage des poussins que durant la première. En général, les oiseaux se posaient dans les rochers après avoir quitté les pieds-porteurs de Prunus mahaleb (74 % des cas). Des expériences de neuf mois sur la survie des graines effectuées dans la zone d'étude ont montré des différences significatives entre les trois types de substrat considérés (herbes, rochers et rochers sous le nid)

Effects of insularity on insect leaf herbivory and chemical defences in a Mediterranean oak species

Aim Research on plant–herbivore interactions has shown that islands typically have low abundances and diversity of herbivores because of barriers to dispersal, isolation and reduced land area. Islands commonly have lower levels of herbivory relative to mainland regions, and, as a consequence, insular plants should exhibit lower levels of defences than their mainland counterparts. Despite these predictions, there are significant gaps in our understanding of insularity effects on plant–herbivore interactions. For instance, most work addressing the effects of insularity on plant–herbivore interactions have compared one or a few islands with a single mainland site. In addition, studies have measured herbivory or plant defences but not both, and the influence of abiotic factors has been neglected. Location Mediterranean Basin (from Spain to Greece). Taxon Quercus ilex L. Methods We conducted a large‐scale study to investigate whether insect leaf herbivory and plant chemical defences in holm oak (Quercus ilex L.) differ between insular versus mainland populations. We further investigated mechanisms by which insularity effects on herbivory may take place by assessing the influence of defences and climatic variables on herbivory. Results We found that insular populations exhibited lower herbivory and higher defences (condensed tannins) than their mainland counterparts. Our analyses, however, suggest that these concomitant patterns of insect herbivory and plant defences were seemingly unrelated as island versus mainland differences in defences did not account for the observed pattern in herbivory. Furthermore, climatic factors did not explain insularity effects on either herbivory or plant defences. Main conclusions Overall, this study provides one of the most robust assessments to date on insularity effects on herbivory and builds towards a better understanding of the ecology and evolution of plant–insect interactions in insular ecosystems.info:eu-repo/semantics/acceptedVersio

Effects of insularity on insect leaf herbivory and chemical defences in a Mediterranean oak species

Aim Research on plant–herbivore interactions has shown that islands typically have low abundances and diversity of herbivores because of barriers to dispersal, isolation and reduced land area. Islands commonly have lower levels of herbivory relative to mainland regions, and, as a consequence, insular plants should exhibit lower levels of defences than their mainland counterparts. Despite these predictions, there are significant gaps in our understanding of insularity effects on plant–herbivore interactions. For instance, most work addressing the effects of insularity on plant–herbivore interactions have compared one or a few islands with a single mainland site. In addition, studies have measured herbivory or plant defences but not both, and the influence of abiotic factors has been neglected. Location Mediterranean Basin (from Spain to Greece). Taxon Quercus ilex L. Methods We conducted a large‐scale study to investigate whether insect leaf herbivory and plant chemical defences in holm oak (Quercus ilex L.) differ between insular versus mainland populations. We further investigated mechanisms by which insularity effects on herbivory may take place by assessing the influence of defences and climatic variables on herbivory. Results We found that insular populations exhibited lower herbivory and higher defences (condensed tannins) than their mainland counterparts. Our analyses, however, suggest that these concomitant patterns of insect herbivory and plant defences were seemingly unrelated as island versus mainland differences in defences did not account for the observed pattern in herbivory. Furthermore, climatic factors did not explain insularity effects on either herbivory or plant defences. Main conclusions Overall, this study provides one of the most robust assessments to date on insularity effects on herbivory and builds towards a better understanding of the ecology and evolution of plant–insect interactions in insular ecosystems.info:eu-repo/semantics/acceptedVersio

Water sports could contribute to the translocation of ranaviruses

[EN] Ranaviruses have been identified as the cause of explosive disease outbreaks in amphibians worldwide and can be transmitted between hosts both via direct and indirect contact, in which humans might contribute to the translocation of contaminated material. The aim of this study was to evaluate the possible role of water sports in the human translocation of ranavirus, Batrachochytrium dendrobatidis (Bd), and B. salamandrivorans (Bsal). A total of 234 boats were sampled during the spring Spanish Canoe Championship which took place in Pontillón de Castro, a reservoir with a history of ranavirosis, in May 2017. Boats were tested for the presence of ranavirus and Batrachochytrium spp. DNA, using quantitative real-time polymerase chain reaction techniques (qPCR). A total of 22 swabs (22/234, 9.40%) yielded qPCR-positive results for Ranavirus DNA while Bd or Bsal were not detected in any of the samples. We provide the first evidence that human-related water sports could be a source of ranavirus contamination, providing justification for public disinfecting stations in key areas where human traffic from water sports is high.SITis study was partially funded by the Principado de Asturias, PCTI 2018–2020 (GRUPIN: IDI2018-000237) and FEDER. We thank Benjamin Rabanal from the Laboratorio de Técnicas Instrumentales, University of León, for Batrachochytrium spp. PCR analysis, and Frank Pasmans’ Lab for kindly providing Bd and Bsal DNA controls

Challenges in confirming eradication success of invasive red-eared sliders

12 páginas, 4 figuras, 3 tablasConfirming eradication success can be notoriously difficult and costly, especially when the species is still present but remains undetected, due to very low population densities and imperfect detection methods. There has been a lack of research on appropriate guidelines and estimation procedures for declaring eradication success for programs aimed at eradicating alien reptiles. Here we develop quantitative rules for confirmation monitoring in eradication campaigns of the red-eared slider turtle (Trachemys scripta elegans). We used a database of slider trapping data from control and eradication campaigns conducted in localities across the Iberian Peninsula and southern France to construct models for inferring appropriate trapping efforts for confirming slider turtle eradication. Basking traps were slightly more efficient than net traps in capturing sliders, although trapping was an inefficient monitoring method given the low capture probabilities estimated. The results of our spatially-explicit eradication scenarios revealed the importance of habitat configuration in declaring eradication success. Declaration of eradication success is contingent on the thresholds set to minimise false positives (i.e., falsely declaring eradication successful), but in any scenario large trapping efforts were required to confirm eradication. Given the low estimated capture probabilities, alternative methods such as eDNA and visual surveys should be considered for monitoring sliders. We suggest that if the costs associated with the impact of alien sliders can be adequately estimated, then eradication can be confirmed by rules minimising both false positive and negative error rates. Otherwise., rules minimising false positive errors would be more appropriate.This research was conducted thanks to the Department of Economic Development, Jobs, Transport and Resources Invasive Plants and Animals Research Project When to stop: Defining rules for surveillance of red-eared slider turtles (Victoria State Government, Australia).Peer reviewe

Are Nested Networks More Robust to Disturbance? A Test Using Epiphyte-Tree, Comensalistic Networks

Recent research on ecological networks suggests that mutualistic networks are more nested than antagonistic ones and, as a result, they are more robust against chains of extinctions caused by disturbances. We evaluate whether mutualistic networks are more nested than comensalistic and antagonistic networks, and whether highly nested, host-epiphyte comensalistic networks fit the prediction of high robustness against disturbance. A review of 59 networks including mutualistic, antagonistic and comensalistic relationships showed that comensalistic networks are significantly more nested than antagonistic and mutualistic networks, which did not differ between themselves. Epiphyte-host networks from old-growth forests differed from those from disturbed forest in several topological parameters based on both qualitative and quantitative matrices. Network robustness increased with network size, but the slope of this relationship varied with nestedness and connectance. Our results indicate that interaction networks show complex responses to disturbances, which influence their topology and indirectly affect their robustness against species extinctions