Browsing by Subject "PREDATORS"

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  • Terraube, Julien (2019)
    This Forum article synthesizes the current evidence on the links between predator-prey interactions, protected areas and spatial variations in Lyme disease risk in Fennoscandia. I suggest key research directions to better understand the role of protected areas in promoting the persistence of diverse predator guilds. Conserving predators could help reducing host populations and Lyme disease risk in northern Europe. There is an urgent need to find possible win-win solutions for biodiversity conservation and human health in ecosystems facing rapid global environmental change.
  • Poysa, Hannu; Lammi, Esa; Poysa, Silvo; Vaananen, Veli-Matti (2019)
    Interactions and dependence between species can transmit the effects of species declines within and between trophic levels, resulting in secondary endangerments and, in some cases, extinctions. Many mixed-species avian breeding aggregations commonly have a protector species whose aggressive nest defense is used by other species to defend their nests. Disappearance of the protector species may have population demographic consequences on the dependent species. Aggressive nest defense behavior of small colonial gulls, such as the black-headed gull (Chroicocephalus ridibundus), is used by many waterbird species to gain protection against predators. We used data from 15 local waterbird communities in Finland to study long-term changes and dynamics of breeding numbers of other waterbirds as a response to long-term changes and dynamics of black-headed gull colonies. We found that breeding numbers of many species tracked long-term changes in the size of black-headed gull colonies. This was true even after controlling for a common trend in the size of the black-headed gull colony and the breeding numbers of the other species. The trend-controlled positive temporal association with black-headed gull was relatively stronger in species that nest in similar habitats of a lake as the black-headed gull, and in species that have a more critical conservation status due to drastic population decline. Our results suggest that the overall decline of black-headed gull colonies has resulted in secondary endangerment of many other species in waterbird communities.
  • Mattila, Anniina L. K.; Jiggins, Chris D.; Opedal, Øystein H.; Montejo-Kovacevich, Gabriela; de Castro, Érika; McMillan, William O.; Bacquet, Caroline; Saastamoinen, Marjo (2021)
    Chemical defences against predators underlie the evolution of aposematic coloration and mimicry, which are classic examples of adaptive evolution. Surprisingly little is known about the roles of ecological and evolutionary processes maintaining defence variation, and how they may feedback to shape the evolutionary dynamics of species. Cyanogenic Heliconius butterflies exhibit diverse warning color patterns and mimicry, thus providing a useful framework for investigating these questions. We studied intraspecific variation in de novo biosynthesized cyanogenic toxicity and its potential ecological and evolutionary sources in wild populations of Heliconius erato along environmental gradients, in common-garden broods and with feeding treatments. Our results demonstrate substantial intraspecific variation, including detectable variation among broods reared in a common garden. The latter estimate suggests considerable evolutionary potential in this trait, although predicting the response to selection is likely complicated due to the observed skewed distribution of toxicity values and the signatures of maternal contributions to the inheritance of toxicity. Larval diet contributed little to toxicity variation. Furthermore, toxicity profiles were similar along steep rainfall and altitudinal gradients, providing little evidence for these factors explaining variation in biosynthesized toxicity in natural populations. In contrast, there were striking differences in the chemical profiles of H. erato from geographically distant populations, implying potential local adaptation in the acquisition mechanisms and levels of defensive compounds. The results highlight the extensive variation and potential for adaptive evolution in defense traits for aposematic and mimetic species, which may contribute to the high diversity often found in these systems.
  • Rigal, Francois; Cardoso, Pedro; Lobo, Jorge M.; Triantis, Kostas A.; Whittaker, Robert J.; Amorim, Isabel R.; Borges, Paulo A. V. (2018)
    Aim: Land-use change typically goes hand in hand with the introduction of exotic-species, which mingle with indigenous species to form novel assemblages. Here, we compare the functional structure of indigenous and exotic elements of ground-dwelling arthropod assemblages across four land-uses of varying management intensity. Location: Terceira Island (Azores, North Atlantic). Methods: We used pitfall traps to sample arthropods in 36 sites across the four land-uses and collated traits related to dispersal ability, body size and resource use. For both indigenous and exotic species, we examined the impact of land-uses on trait diversity and tested for the existence of non-random assembly processes using null models. We analysed differences in trait composition among land-uses for both indigenous and exotic species with multivariate analyses. We used point-biserial correlations to identity traits significantly correlated with specific land-uses for each element. Results: We recorded 86 indigenous and 116 exotic arthropod species. Under high-intensity land-use, both indigenous and exotic elements showed significant trait clustering. Trait composition strongly shifted across land-uses, with indigenous and exotic species being functionally dissimilar in all land-uses. Large-bodied herbivores dominated exotic elements in low-intensity land-uses, while small-bodied spiders dominated exotic elements in high-intensity land-uses. In contrast, with increasing land-use intensity, indigenous species changed from functionally diverse to being dominated by piercing and cutting herbivores. Main conclusions: Our study revealed two main findings: first, in high-intensity - land-uses, trait clustering characterized both indigenous and exotic elements; second, exotic species differed in their functional profile from indigenous species in all land-use types. Overall, our results provide new insights into the functional role of exotic species in a land-use context, suggesting that, in agricultural landscape, exotic species may contribute positively to the maintenance of some ecosystem functions.
  • Buechley, Evan R.; Santangeli, Andrea; Girardello, Marco; Neate-Clegg, Montague H.C.; Oleyar, Dave; McClure, Christopher J.W.; Şekercioğlu, Çagan H. (2019)
    Abstract Aim Raptors serve critical ecological functions, are particularly extinction-prone and are often used as environmental indicators and flagship species. Yet, there is no global framework to prioritize research and conservation actions on them. We identify for the first time the factors driving extinction risk and scientific attention on raptors and develop a novel research and conservation priority index (RCPI) to identify global research and conservation priorities. Location Global. Methods We use random forest models based on ecological traits and extrinsic data to identify the drivers of risk and scientific attention in all raptors. We then map global research and conservation priorities. Lastly, we model where priorities fall relative to country-level human social indicators. Results Raptors with small geographic ranges, scavengers, forest-dependent species and those with slow life histories are particularly extinction-prone. Research is extremely biased towards a small fraction of raptor species: 10 species (1.8% of all raptors) account for one-third of all research, while one-fifth of species have no publications. Species with small geographic ranges and those inhabiting less developed countries are greatly understudied. Regions of Latin America, Africa and Southeast Asia are identified as particularly high priority for raptor research and conservation. These priorities are highly concentrated in developing countries, indicating a global mismatch between priorities and capacity for research and conservation. Main conclusions A redistribution of scientific attention and conservation efforts towards developing tropical countries and the least-studied, extinction-prone species is critical to conserve raptors and their ecological functions worldwide. We identify clear taxonomic and geographic research and conservation priorities for all raptors, and our methodology can be applied across other taxa to prioritize scientific investment.
  • Alexandridis, Nikolaos; Marion, Glenn; Chaplin-Kramer, Rebecca; Dainese, Matteo; Ekroos, Johan; Grab, Heather; Jonsson, Mattias; Karp, Daniel S.; Meyer, Carsten; O'Rourke, Megan E.; Pontarp, Mikael; Poveda, Katja; Seppelt, Ralf; Smith, Henrik G.; Martin, Emily A.; Clough, Yann (2021)
    Natural control of invertebrate crop pests has the potential to complement or replace conventional insecticide based practices, but its mainstream application is hampered by predictive unreliability across agroecosystems. Inconsistent responses of natural pest control to changes in landscape characteristics have been attributed to ecological complexity and system-specific conditions. Here, we review agroecological models and their potential to provide predictions of natural pest control across agricultural landscapes. Existing models have used a multitude of techniques to represent specific crop-pest-enemy systems at various spatiotemporal scales, but less wealthy regions of the world are underrepresented. A realistic representation of natural pest control across systems appears to be hindered by a practical trade-off between generality and realism. Nonetheless, observations of context-sensitive, trait-mediated responses of natural pest control to land-use gradients indicate the potential of ecological models that explicitly represent the underlying mechanisms. We conclude that modelling natural pest control across agroecosystems should exploit existing mechanistic techniques towards a framework of contextually bound generalizations. Observed similarities in causal relationships can inform the functional grouping of diverse agroecosystems worldwide and the development of the respective models based on general, but context-sensitive, ecological mechanisms. The combined use of qualitative and quantitative techniques should allow the flexible integration of empirical evidence and ecological theory for robust predictions of natural pest control across a wide range of agroecological contexts and levels of knowledge availability. We highlight challenges and promising directions towards developing such a general modelling framework.
  • Hedlund, Johanna; Ehrnsten, Eva; Hayward, Christina; Lehmann, Philipp; Hayward, Alex (2020)
    Tropical America is currently experiencing the establishment of a new apex insect predator, the Paleotropical dragonfly Hemianax ephippiger (Odonata: Aeshnidae). H. ephippiger is migratory and is suggested to have colonised the eastern Neotropics by chance Trans-Atlantic displacement. We report the discovery of H. ephippiger at three new locations in the Caribbean, the islands of Bonaire, Isla de Coche (Venezuela), and Martinique, and we review its reported distribution across the Neotropics. We discuss the establishment of H. ephippiger as a new apex insect predator in the Americas, both in terms of ecological implications and the possible provision of ecosystem services. We also provide an additional new species record for Bonaire, Pantala hymenaea (Odonata: Libellulidae).
  • Kahilainen, K. K.; Thomas, S. M.; Harrod, C.; Hayden, B.; Eloranta, A. P. (2019)
    The trophic ecology of piscivorous Arctic charr (Salvelinus alpinus (L.); charr) in the food webs of large subarctic lakes is not well understood. We assessed charr diets, parasites, growth, maturity, and stable isotope ratios in Fennoscandian subarctic lakes dominated by monomorphic or polymorphic whitefish (Coregonus lavaretus (L.)) populations. Charr density was low in all lakes, except in profundal habitats. Charr shifted to piscivory at small size (16-25 cm total length) and consumed a range of prey-fish sizes (2-25 cm). Cannibalism was observed in a few individuals from one monomorphic whitefish lake. Charr matured at 37-51 cm (5-8 years old), grew to 52-74 cm maximum observed length and 47-83 cm asymptotic length. Charr increased total area of convex hull and core stable isotopic diversity area of the fish community by 51-98% and 44-51% in monomorphic whitefish lakes, but only 8-11% and 7-10% in polymorphic whitefish lakes. The difference was due to increasing food-chain length in monomorphic whitefish lakes, whereas reliance on littoral carbon did not change. Charr were the top piscivores in monomorphic whitefish lakes, but played a less important role in polymorphic whitefish lakes, which contained a more diverse predator fauna.