| 1. |
- Dessborn, Lisa, 1976-, et al.
(författare)
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Pike predation affects breeding success and habitat selection of ducks
- 2011
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Ingår i: Freshwater Biology. - : Wiley: 12 months. - 0046-5070 .- 1365-2427. ; 56:3, s. 579-589
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Tidskriftsartikel (refereegranskat)abstract
- 1. Fish and ducks often belong to the same local food web, and several studies indicate that there is a general negative effect of fish on breeding ducks. This pattern has so far been addressed mainly within the framework of competition for common invertebrate prey, while predation by large fish as a force behind settlement and abundance patterns in ducks remains largely unknown. This is the first study to address the effect of fish predation on breeding ducks, isolated from that of competition, and the first experiment to explore the ability of ducks to identify and avoid lakes with high risk of fish predation. 2. We used a before-after control-impact design and 11 naturally fishless lakes. Waterfowl on the lakes were surveyed during the breeding season of 2005. Large adult pike (Esox lucius) were added to two lakes in early spring 2008, and waterfowl surveys were repeated on all 11 lakes. 3. Pike introduction did not affect the number of pairs on lakes during the nesting season in any of three focal duck species (mallard Anas platyrhynchos, teal Anas crecca, and goldeneye Bucephala clangula). During the brood-rearing season, however, there was a decrease in duck days in teal and goldeneye in lakes with pike, with similar trends observed in mallard. The number of goldeneye ducklings was also significantly lower in lakes with pike. We were unable to determine whether the response was attributable to direct pike predation or to broods leaving experimental lakes, but in either case, our study demonstrates high fitness costs for ducks breeding on lakes with pike. 4. The apparent inability of nesting ducks to detect pike and the clear fitness implications may influence the annual recruitment of ducks on a larger scale as pike are both common and widespread. Vegetation complexity and food abundance are likely to be of overriding importance when breeding ducks are choosing a nesting site. As pike have a strong influence on breeding birds, relying on vegetation and cues of food abundance, while ignoring indicators of predation risk from fish, could lead to lakes with pike acting as an ecological trap.
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| 2. |
- Elmberg, Johan, et al.
(författare)
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Within-season sequential density dependence regulates breeding success in mallards Anas platyrhynchos
- 2005
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Ingår i: Oikos. - 0030-1299 .- 1600-0706. ; 108, s. 582-590
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Tidskriftsartikel (refereegranskat)abstract
- Density dependence in vital rates is a key issue in population ecology but remains largely unexplored experimentally. We studied breeding success, lake use, and prey availability in wild mallards Anas platyrhynchos on small nemoral lakes in a replicated, two-year cross-over experiment in which pair density was increased. The number of wild mallards that settled on lakes prior to introductions of extra pairs did not differ between control and introduction years. Introductions led to a lake-level reduction in the number of broods observed. However, the number of stage 2/ (almost fledged) ducklings did not differ between treatments, nor did lake utilization by nonbreeding adults, broods and ducklings. Prey resource availability differed greatly among lakes, but it did not correlate with breeding success. Partialling out the possible effect of food competition from wild adult nonbreeding mallards did not change this conclusion. Our study demonstrates sequential density dependence in breeding success; introductions caused a decrease in brood number, but despite fewer broods a similar number of nearly fledged ducklings were produced. We suggest that predation and/or lake change of broods soon after hatching created these patterns. We conclude that using a single and late measure of breeding success such as fledged birds can mask regulatory processes. Implications of density dependence and its relation to individual reproductive success are understood better if breeding success is decomposed into nest success, duckling survival and fledgling survival.
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| 3. |
- Jönsson, K. Ingemar, 1959-, et al.
(författare)
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Environmental adaptations : radiation tolerance
- 2019
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Ingår i: Water bears. - : Springer. - 9783319957012 - 9783319957029 ; , s. 311-330
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Several studies in different species have documented that tardigrades are among the most radiation-tolerant animals on Earth, surviving doses of ionizing radiation on the order of kGy. Both low-LET and high-LET radiation have been used with no apparent differences in the tolerance of the animals. Tolerance to ionizing radiation in tardigrades also seems to be independent of whether the animal has entered a dry anhydrobiotic state or is hydrated with normal activity. However, when exposed to UV radiation, desiccated tardigrades show a higher tolerance than hydrated animals. Recent studies in several species have shown that tardigrade embryos have considerably lower tolerance to ionizing radiation compared to adults, and embryos in the early stage of development are clearly more sensitive to radiation than those in the late developmental stage. The molecular mechanisms behind radiation tolerance in tardigrades are still largely unclear, but available evidence suggests that mechanisms related to both the avoidance of DNA damage and the repair of damage are involved.
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| 4. |
- Jönsson, K. Ingemar, 1959-, et al.
(författare)
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The fate of the TARDIS offspring : no intergenerational effects of space exposure
- 2016
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Ingår i: Zoological Journal of the Linnean Society. - 0024-4082 .- 1096-3642. ; 178:4, s. 924-930
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Tidskriftsartikel (refereegranskat)abstract
- In September 2007 tardigrades became the first animal in history to survive the combined effect of exposure to space vacuum, cosmic radiation and ultraviolet radiation in low Earth orbit. The main results from this experiment were reported in 2008, but some of the results have remained unpublished. Here we report that descendant generations of space-exposed tardigrades of the species Milnesium tardigradum did not show reduced performance. This indicates that individual tardigrades that survived the exposure to environmental extremes in space, and were able to reproduce, did not transfer any damage to later generations. Repair of environmentally induced damage may therefore follow a ‘make or break’ rule, such that a damaged animal either fails to repair all damage and dies, or repairs damage successfully and leaves no mutations to descendants. We also report that two additional tardigrade species, Echiniscus testudo and Ramazzottius oberhaeuseri, showed high survival after exposure to space vacuum and cosmic radiation within the TARDIS experiment.
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| 5. |
- Söderquist, Pär
(författare)
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Large-scale releases of native species : the mallard as a predictive model system
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Human alteration of natural systems, and its consequences are of great concern and the impact on global ecosystems is one of the biggest threats that biodiversity stands before. Translocations of invasive species, as well as intraspecific contingents with non-native genotypes, whether they are deliberate or unintentional, are one such alteration and its consequences are continuously being assessed. The mallard (Anas platyrhynchos) is the most numerous and widespread duck in the world and a flagship in wetland conservation. It is also an important game species which is heavily restocked for hunting purposes, especially in Europe where over three million ducklings are released every year. Because of its hunted status, its abundance, and the number of released individuals, it can serve as a model species to study effects of releases, both for conservation and restocking for hunting, on wild populations. In this thesis the status of the mallard was assessed in the Nordic countries and the effects of releases on the wild populations were studied by mining historical ringing data, comparing morphology of present-day wild, farmed, and historical mallards, and analyzing phylogeography of wild and farmed mallards in Europe. The status of the mallard population in the Nordic countries are generally good, however, a joint effort of European countries is needed to monitor and manage the population. A significant difference between wild and farmed mallards concerning longevity, migration, bill morphology and genetic structure was also found, together with signs of cryptic introgression of farmed genotypes in the wild population with potential fitness reduction as a result. The effect is however limited by that only a fraction of released farmed mallards reach the breeding season due to low survival. A natural captive environment is crucial to keep individuals wild-like with high survival rates after release. However, with an introgression of potentially maladapted farmed genotypes leading to a reduction in fitness, a low survival of released mallards would favor the wild population. A legislative change regarding obligation to report numbers, provenance, and release sites of farmed mallard should be considered, together with practical solutions of ringing and genetic monitoring of released mallards.
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| 6. |
- Strong, Emily A., et al.
(författare)
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Seeking greener pastures : crop selection by Greylag Geese (Anser anser) during the moulting season
- 2021
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Ingår i: Ornis Fennica. - : Finnish Omithological Soc. - 0030-5685. ; 98:1, s. 16-32
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Tidskriftsartikel (refereegranskat)abstract
- Over the last 40 years, many goose populations have recovered from historic lows and are now more numerous than ever. At the same time, geese have shifted from natural foraging habitats to securing most of their nutritional demands from agricultural fields, leading to crop damage and conflict with agriculture. We studied field use by Greylag Geese (Anser anser) in the agricultural landscape surrounding a main breeding and moulting lake in Sweden. From 2012 to 2016, weekly roadside surveys were conducted from May to July. Data were collected on goose numbers, crop type and sward height in agricultural fields. Using a compositional analysis, we demonstrate that Greylag Geese show a strong selection for ley and pasture fields compared to other crop types (rank order: ley/pasture > oat > barley > wheat > other crops). This selection was consistent across years and between pre- and post-moult. Aside from ley and pasture, no other croptypes were selected for, as they were used less than expected given their availability. Irrespective of crop type, geese foraged predominantly on short (0–10 cm) swards. The strong selection for ley and pasture may have been driven by higher nutritional quality of short, managed grass swards relative to other available foods. This suggests that during the summer grass fields may be more vulnerable to damage compared to other crop types. Our study provides a deeper understanding of the ecology of Greylag Geese, which may be used to inform management strategies focused on mitigating crop damage and alleviating conflict.
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| 7. |
- Åkesson, Susanne, et al.
(författare)
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Autumn migratory orientation and route choice in early and late dunlins Calidris alpina captured at a stopover site in Alaska
- 2021
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Ingår i: Biology open. - : The Company of Biologists Ltd. - 2046-6390. ; 10:4, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the migratory orientation of early and late captured dunlins, Calidris alpina, by recording their migratory activity in circular orientation cages during autumn at a staging site in southwest Alaska and performed route simulations to the wintering areas. Two races of dunlins breeding in Alaska have different wintering grounds in North America (Pacific Northwest), and East Asia. Dunlins caught early in autumn (presumably Calidris alpina pacifica) oriented towards their wintering areas (east-southeast; ESE) supporting the idea that they migrate nonstop over the Gulf of Alaska to the Pacific Northwest. We found no difference in orientation between adult and juveniles, nor between fat and lean birds or under clear and overcast skies demonstrating that age, energetic status and cloud cover did not affect the dunlins' migratory orientation. Later in autumn, we recorded orientation responses towards south-southwest suggesting arrival of the northern subspecies Calidris alpina arcticola at our site. Route simulations revealed multiple compass mechanisms were compatible with the initial direction of early dunlins wintering in the Pacific Northwest, and for late dunlins migrating to East Asia. Future high-resolution tracking would reveal routes, stopover use including local movements and possible course shifts during migration from Alaska to wintering sites on both sides of the north Pacific Ocean.
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| 8. |
- Massa, Edoardo, et al.
(författare)
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Tardigrades of Kristianstads Vattenrike biosphere reserve with description of four new species from Sweden
- 2021
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Ingår i: Scientific Reports. - 2045-2322. ; 11:1, s. 1-19
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Tidskriftsartikel (refereegranskat)abstract
- Kristianstads Vattenrike Biosphere Reserve [KVBR] is a UNESCO designated area of Sweden possessing high biological value. Although several studies on tardigrades inhabiting Sweden havebeen performed, the KVBR area has been neglected. The current study investigates the tardigrade fauna of five areas of the biosphere reserve and includes 34 samples of different substrates analysed quantitatively and qualitatively. In total, 33 species of tardigrades were found in the samples, including 22 new records for the Skåne region, 15 new records for Sweden, and four species new to science. Mesobiotus emiliae sp. nov., Xerobiotus gretae sp. nov., Itaquascon magnussoni sp. nov., and Thulinius gustavi sp. nov. were described with an integrative approach (when possible) using morphological characters (light, electron scanning, and confocal laser scanning microscopies) and molecular markers (ITS2, 18S, 28S, cox1). A new protocol to increase morphological data was developed recovering mounted specimens within old slides for SEM analysis. Emended diagnoses for the genus Itaquascon and the transfer of Platicrista itaquasconoide to the genus Meplitumen are proposed. This study enriches the knowledge of the tardigrade biodiversity both within the KVBR and in Sweden and contributes to the rapidly increasing number of tardigrade species reported worldwide. The 33 species identified in the KVBR area represents 28% of all water bear species found in Sweden so far. The restricted study areas and limited number of samples collected suggests that the KVBR is very rich of tardigrades.
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| 9. |
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| 10. |
- Arzel, Céline, et al.
(författare)
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Does foraging in Teal Anas crecca depend on season and disturbance by predators?
- 2006
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Ingår i: Integrating science and duck management. ; , s. 131-
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Konferensbidrag (refereegranskat)abstract
- To ensure wise management of migratory species it is crucial to know their energy requirements throughout their biological cycle, especially during periods like spring migration, that might affect future breeding success. Surprisingly, this period has seldom been studied. To start filling this gap for dabbling ducks and especially Eurasian Teal Anas crecca, we studied their foraging time and foraging methods along their Western European flyway from wintering to breeding grounds. Differences in foraging activity between sexes, species, years, seasons, sites and diel patterns were checked, as well as potential effects of disturbances by potential predators. Ducks of both sexes presented a fairly constant nocturnal foraging along the flyway, whereas diurnal foraging increased at periods of high requirements (spring, breeding, moulting). Ducks might thus not only be income breeders, but also income migrators (relying on the food they encounter along their flyway to fuel their travel). Moreover, Teal foraging depth increased along the flyway when disturbance due to potential predators decreased. This probably reflects their diet switch (from granivorous to carnivorous). The decrease in predator pressure probably makes it possible for teals to use riskiest behaviors (greater depths associated to eyes underwater and less prevention of predators).We thus highlight the need for adequate management of staging wetlands all along the flyway, since ducks have to fulfill high energy requirements there. Water level control may be useful to provide more shallow foraging habitats in which they can use less risky foraging techniques at times when nutrient needs increases and predation risk is relatively high.
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