Publications by authors named "Ola Olsson"

23 Publications

  • Page 1 of 1

Agreement Between Clinical Examination and Magnetic Resonance Imaging in Acute Knee Trauma With Hemarthrosis.

Clin J Sport Med 2021 Jun 9. Epub 2021 Jun 9.

Department of Orthopaedics, NU-Hospital Group, Uddevalla/Trollhättan, Sweden; Department of Clinical Sciences Lund, Orthopaedics, Lund University, Lund, Sweden; and Department of Orthopaedics, Helsingborg Hospital, Helsingborg, Sweden.

Objective: Hemarthrosis after knee trauma often indicates serious joint injury. Few studies have evaluated agreement between clinical examination and findings from magnetic resonance imaging (MRI). We aimed to describe the agreement between acute clinical examination and subacute MRI findings after acute knee trauma with hemarthrosis and the importance of the subspecialty of the examiner.

Design: Longitudinal cohort study. Agreement with MRI findings was evaluated by logistic regression.

Setting: Helsingborg hospital.

Patients: Thousand one hundred forty-five consecutive patients with hemarthrosis after knee trauma.

Interventions: Clinical examination and MRI.

Main Outcome Measures: agreement between clinical examination and findings from MRI. We considered the radiologist's report as the gold standard.

Results: Median time (25th, 75th percentile) from injury to clinical examination was 2 (1, 7) days, and from injury to imaging was 8 (5, 15) days. The overall sensitivity and specificity of clinical examination versus MRI for major ligament injury or lateral patella dislocation (LPD) were 70% [95% confidence interval 67-73) and 66% (61-72), respectively. Orthopedic subspecialist knee had the highest agreement with anterior cruciate ligament rupture (adjusted odds ratios were 1.7 (95% confidence interval 1.2-2.3), 1.9 (1.2-3.0) and 5.9 (3.7-9.5) for orthopedic trainees, orthopedic subspecialists other, and orthopedic subspecialist knee, respectively]. For other ligament injuries and LPD, we did not find statistically significant differences.

Conclusions: Clinical diagnosis after acute knee injury is relatively unreliable versus MRI findings even when performed by orthopedic specialists. However, the agreement is improved when the examination is performed by an orthopedic knee subspecialist.
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http://dx.doi.org/10.1097/JSM.0000000000000950DOI Listing
June 2021

Acromioclavicular joint dislocations: incidence, injury profile, and patient characteristics from a prospective case series.

JSES Int 2020 Jun 8;4(2):246-250. Epub 2020 Apr 8.

Department of Orthopedics, Lund University, Helsingborg Hospital, Helsingborg, Sweden.

Background: Acromioclavicular joint (ACJ) dislocations are common but evidence regarding the epidemiology of these injuries is incomplete. This study aims to describe the incidence, injury mechanisms, distribution of classifications, risk factors, and patient characteristics for ACJ dislocations in a general population.

Methods: Inclusion was performed prospectively during a 4-year period with the following criteria; age 18-75 years, shoulder trauma within 2 weeks, a clinical suspicion of ACJ dislocation, and radiographs that excluded fracture. The injuries were classified according to the Rockwood system, and epidemiologic variables were obtained. Rockwood types 1-2 were defined as low-grade injuries and types 3-6 as high-grade. Age groups were defined with a young group (18-39 years), an intermediate group (40-59), and an old group (60-75).

Results: A total of 158 patients were included; 139 were male and the mean age was 39 years (range 18-74). There were 73 low-grade and 85 high-grade injuries. The incidence was 2.0 [95% confidence interval (CI) = 1.7-2.4] per 10,000 person-years, gradually decreasing with higher age, groupwise. The incidence rate ratio (IRR) for men vs. women was 7.6 (95% CI = 4.7-12.6) and IRR >1 was seen comparing younger age groups to older. Odds ratio calculations showed that risk factors for high-grade injury were older age and traffic accidents.

Conclusion: The incidence of ACJ dislocations was 2.0 per 10,000 person-years in a general population. Male gender and younger age group were risk factors for injury, whereas the risk for high-grade injuries were greater in older patients and after traffic accidents.
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http://dx.doi.org/10.1016/j.jseint.2020.01.009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7256880PMC
June 2020

Competition, seed dispersal and hunting: what drives germination and seedling survival in an Afrotropical forest?

AoB Plants 2019 Apr 28;11(2):plz018. Epub 2019 Mar 28.

Cross River State Forestry Commission, Calabar, Nigeria.

Disentangling the contributions of different processes that influence plant recruitment, such as competition and seed dispersal, is important given the increased human-mediated changes in tropical forest ecosystems. Previous studies have shown that seedling communities in an Afrotropical rainforest in southeastern Nigeria are strongly affected by the loss of important seed-dispersing primates, including Cross River gorillas (), chimpanzee () and drill (). Here we study how germination and survival of tree seedlings are affected by competition and reduced seed dispersal in three contiguous forest reserves, in southeastern Nigeria, with similar mature tree species composition and structure. We use an experimental design aimed at manipulating the effect of competition among seedlings in three protected and three hunted sites within the reserves. We use a total of sixty 5 × 5 m plots of three types: plots cleared of all seedlings, plots selectively cleared of all primate-dispersed seedlings and control plots. All seedlings were identified, measured, assigned to dispersal mode and tagged, and after 1 year we evaluated survival, mortality and new recruits. We found that in hunted sites germination of abiotically dispersed species was over four times higher in cleared plots compared to control plots, whereas germination of primate-dispersed species was the same, which indicated that dispersal limitation was the dominant force in seedling recruitment in hunted sites. This was supported by the fact that the germination of all dispersal modes in the selectively cleared plots in protected sites was similar to the control plots in the same sites, but germination of abiotically dispersed species was significantly lower than in cleared plots in hunted sites. Competition among seedlings was mostly evident from the fact that 75 % more seedlings of primate-dispersed species germinated in cleared compared to control plots in protected sites. We conclude that inter-seedling competition may be irrelevant to seedling recruitment in hunted sites, where dispersal limitation appears to be a much stronger force shaping the seedling plant community, and thus hunting indirectly reverses the importance of competition and dispersal limitation in structuring seedling communities.
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http://dx.doi.org/10.1093/aobpla/plz018DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6475525PMC
April 2019

The gracilis tendon autograft is a safe choice for orthopedic reconstructive procedures: a consecutive case series studying the effects of tendon harvesting.

BMC Musculoskelet Disord 2019 Mar 30;20(1):138. Epub 2019 Mar 30.

Department of Orthopedics, Helsingborg Hospital, Helsingborg, Sweden.

Background: The gracilis tendon is commonly used as an autograft to reconstruct torn tendons or ligaments in many parts of the body. Little is known about the subjective and functional outcome after gracilis tendon harvest. The aim of this study was to evaluate the outcome of the donor leg in patients undergoing such surgery.

Methods: Patients with chronic acromioclavicular joint dislocations undergoing coracoclavicular ligament reconstructions using autogenous gracilis tendon grafts were eligible for this study. The graft harvesting procedure was carried out in a standard fashion using a tendon stripper. Knee injury and Osteoarthritis Outcome Score (KOOS) were collected preoperatively and after 12 months. The first 5 patients were included retrospectively and lacked preoperative data, for these patients age- and gender matched normative KOOS scores were used as baseline values. Isometric knee flexor strength in 60° and 90° degrees of flexion was measured at final follow up at a median of 26 (14-56) months postoperatively with the non-operated leg used as reference.

Results: Twenty four patients were eligible for the study and 2 were excluded. The 22 patients available for analysis had a mean age of 44 (22-62) years at the time of surgery and 4 were women. There was no statistically significant change in KOOS 12 months postoperatively compared to baseline values but the patients were weaker in knee flexion in the operated leg compared to the non-operated one.

Conclusions: Gracilis tendon harvesting results in a weakness of knee flexion but does not impair subjective knee function and is a procedure that can be recommended when an autogenous tendon graft is needed.
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http://dx.doi.org/10.1186/s12891-019-2520-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6441161PMC
March 2019

Estimating effects of arable land use intensity on farmland birds using joint species modeling.

Ecol Appl 2019 06 15;29(4):e01875. Epub 2019 Mar 15.

Department of Biology, Biodiversity Unit, Lund University, Sölvegatan 37, Lund, SE 223 62, Sweden.

Declines in European farmland birds over past decades have been attributed to the combined effects of agricultural intensification and abandonment. Consequently, aspirations to stop declines should focus attention on reversing these changes through voluntary or policy-driven interventions. The design of such interventions should ideally be informed by scientific knowledge of which aspects of the transformation of agricultural landscapes have contributed to the farmland bird declines. Declines may be associated with loss of natural habitats or the intensification and homogenization of land use management on production land, and furthermore, these changes may interact. Here, we applied an orthogonal design exploiting spatial variation in land use in a major agricultural region of Sweden to seek evidence for benefits to farmland birds of reversing some of the intensifications on and among arable fields and whether effects are modified by the availability of seminatural habitats (pastures and field borders) in the landscape. We accounted for the potentially confounding effect of interactions between species by using a joint species distribution model explicitly controlling for additional variation and covariation among species. We found that interventions aimed specifically at land in production could provide benefits to farmland birds. Landscapes with a higher proportion leys or fallows and/or with a more diverse set of crops held higher abundances of most farmland birds. However, effects were only apparent in landscapes with low availability of seminatural habitats and were sometimes even negative in landscapes with high amounts of such habitats, demonstrating context dependence. Even if we found little evidence of interactions between species, the joint modeling approach provided several benefits. It allowed information to be shared between species making analyses robust to uncertainty due to low abundances and provided direct information about the mean and variability in effects of studied predictors among species. We also found that care needs to be taken regarding prior and distributional assumptions as the importance of species interactions might otherwise be overstated. We conclude that this approach is well suited for evaluating agricultural policies by providing evidence for or against certain interventions or to be linked to policy scenarios of land use change.
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http://dx.doi.org/10.1002/eap.1875DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6850359PMC
June 2019

Climate warming and land-use changes drive broad-scale floristic changes in Southern Sweden.

Glob Chang Biol 2018 06 16;24(6):2607-2621. Epub 2018 Jan 16.

Biodiversity Unit, Department of Biology, Lund University, Lund, Sweden.

Land-use changes, pollution and climate warming during the 20th century have caused changes in biodiversity across the world. However, in many cases, the environmental drivers are poorly understood. To identify and rank the drivers currently causing broad-scale floristic changes in N Europe, we analysed data from two vascular plant surveys of 200 randomly selected 2.5 × 2.5 km grid-squares in Scania, southernmost Sweden, conducted 1989-2006 and 2008-2015, respectively, and related the change in frequency (performance) of the species to a wide range of species-specific plant traits. We chose traits representing all plausible drivers of recent floristic changes: climatic change (northern distribution limit, flowering time), land-use change (light requirement, response to grazing/mowing, response to soil disturbance), drainage (water requirement), acidification (pH optimum), nitrogen deposition and eutrophication (N requirement, N fixation ability, carnivory, parasitism, mycorrhizal associations), pollinator decline (mode of reproduction) and changes in CO levels (photosynthetic pathway). Our results suggest that climate warming and changes in land-use were the main drivers of changes in the flora during the last decades. Climate warming appeared as the most influential driver, with northern distribution limit explaining 30%-60% of the variance in the GLMM models. However, the relative importance of the drivers differed among habitat types, with grassland species being affected the most by cessation of grazing/mowing and species of ruderal habitats by on-going concentration of both agriculture and human population to the most productive soils. For wetland species, only pH optimum was significantly related to species performance, possibly an effect of the increasing humification of acidic water bodies. An observed relative decline of mycorrhizal species may possibly be explained by decreasing nitrogen deposition resulting in less competition for phosphorus. We found no effect of shortage or decline of pollinating lepidopterans and bees.
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http://dx.doi.org/10.1111/gcb.14031DOI Listing
June 2018

Comparison and analysis of reoperations in two different treatment protocols for trochanteric hip fractures - postoperative technical complications with dynamic hip screw, intramedullary nail and Medoff sliding plate.

BMC Musculoskelet Disord 2017 Aug 24;18(1):364. Epub 2017 Aug 24.

Department of Orthopedics, Helsingborg Hospital, S-251 87, Helsingborg, Sweden.

Background: In treatment of unstable trochanteric fractures dynamic hip screw and Medoff sliding plate devices are designed to allow secondary fracture impaction, whereas intramedullary nails aim to maintain fracture alignment. Different treatment protocols are used by two similar Swedish regional emergency care hospitals. Dynamic hip screw is used for fractures considered as stable within the respective treatment protocol, whereas one treatment protocol (Medoff sliding plate/dynamic hip screw) uses biaxial Medoff sliding plate for unstable pertrochanteric fractures and uniaxial Medoff sliding plate for subtrochanteric fractures, the second (intramedullary nail/dynamic hip screw) uses intramedullary nail for subtrochanteric fractures and for pertrochanteric fractures with intertrochanteric comminution or subtrochanteric extension. All orthopedic surgeries are registered in a regional database.

Methods: All consecutive trochanteric fracture operations during 2011-2012 (n = 856) and subsequent technical reoperations (n = 40) were derived from the database. Reoperations were analysed and classified into the categories adjustment (percutaneous removal of the locking screw of the Medoff sliding plate or the intramedullary nail, followed by fracture healing) or minor, intermediate (reosteosynthesis) or major (hip joint replacement, Girdlestone or persistent nonunion) technical complications.

Results: The relative risk of intermediate or major technical complications was 4.2 (1.2-14) times higher in unstable pertrochanteric fractures and 4.6 (1.1-19) times higher in subtrochanteric fractures with treatment protocol: intramedullary nail/dynamic hip screw, compared to treatment protocol: Medoff sliding plate/dynamic hip screw. Overall rates of intermediate and major technical complications in unstable pertrochanteric and subtrochanteric fractures were with biaxial Medoff sliding plate 0.68%, with uniaxial Medoff sliding plate 1.4%, with dynamic hip screw 3.4% and with intramedullary nail 7.2%.

Conclusions: The treatment protocol based on use of biaxial Medoff sliding plate for unstable pertrochanteric and uniaxial Medoff sliding plate for subtrochanteric fractures reduced the risk of severe technical complications compared to using the treatment protocol based on dynamic hip screw and intramedullary nail.
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http://dx.doi.org/10.1186/s12891-017-1723-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5571618PMC
August 2017

Early prediction of physical activity level 1 year after stroke: a longitudinal cohort study.

BMJ Open 2017 Aug 4;7(8):e016369. Epub 2017 Aug 4.

Department of Clinical Neuroscience, Institute of Neuroscience and Physiology, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden.

Objective: To investigate which variables present prior and early after stroke may have an impact on the level of physical activity (PA) 1 year poststroke.

Design: Prospective longitudinal cohort and logistic regression analysis.

Setting: Stroke Unit at Sahlgrenska University Hospital, Gothenburg, Sweden.

Participants: 117 individuals as part of the Stroke Arm Longitudinal Study (SALGOT) admitted to the stroke unit during a period of 18 months were consecutively recruited. The inclusion criteria were: first-time stroke, impaired upper extremity function, admitted to the stroke unit within 3 days since onset, local residency and ≥18 years old. The exclusion criteria were: upper extremity condition or severe multi-impairment prior to stroke, short life expectancy and non-Swedish speaking. 77 participants followed up at 1 year poststroke were included in the analysis.

Primary Outcome: PA level 1 year after stroke was assessed using a 6-level Saltin-Grimby Scale, which was first dichotomised into mostly inactive or mostly active and second into low or moderate/high level of PA.

Results: Being mostly inactive 1 year after stroke could be predicted by age at stroke onset (OR 1.07, 95% CI 1.00 to 1.13, p=0.041), functional dependency at discharge (OR 7.01, 95% CI 1.73 to 28.43, p=0.006) and prestroke PA (OR 7.46, 95% CI 1.51 to 36.82, p=0.014). Having a low level of PA 1 year after stroke could be predicted by age at stroke onset (OR 1.13, 95% CI 1.06 to 1.21, p<0.001) and functional dependency at discharge (OR 3.62, 95% CI 1.09 to 12.04, p=0.036).

Conclusions: Previous low level of PA, older age and functional dependency all provided value in predicting low PA 1 year after stroke. These results indicate that age and simple clinical evaluations early after stroke may be useful to help clinicians identify persons at risk of being insufficiently active after stroke. Further research is needed to clarify if these findings may apply to the large population of stroke survivors.

Trial Registration Number: ClinicalTrials.gov (NCT01115348).
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http://dx.doi.org/10.1136/bmjopen-2017-016369DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5634455PMC
August 2017

Body Temperature Regulation in Hot Environments.

PLoS One 2016 22;11(8):e0161481. Epub 2016 Aug 22.

Department of Biology, Lund University, SE-223 62, Lund, Sweden.

Organisms in hot environments will not be able to passively dissipate metabolically generated heat. Instead, they have to revert to evaporative cooling, a process that is energetically expensive and promotes excessive water loss. To alleviate these costs, birds in captivity let their body temperature increase, thereby entering a state of hyperthermia. Here we explore the use of hyperthermia in wild birds captured during the hot and dry season in central Nigeria. We found pronounced hyperthermia in several species with the highest body temperatures close to predicted lethal levels. Furthermore, birds let their body temperature increase in direct relation to ambient temperatures, increasing body temperature by 0.22°C for each degree of increased ambient temperature. Thus to offset the costs of thermoregulation in ambient temperatures above the upper critical temperature, birds are willing to let their body temperatures increase by up to 5°C above normal temperatures. This flexibility in body temperature may be an important mechanism for birds to adjust to predicted increasing ambient temperatures in the future.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0161481PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4993450PMC
August 2017

More Efficient Virtual Shadow Maps for Many Lights.

IEEE Trans Vis Comput Graph 2015 Jun;21(6):701-13

Recently, several algorithms have been introduced that enable real-time performance for many lights in applications such as games. In this paper, we explore the use of hardware-supported virtual cube-map shadows to efficiently implement high-quality shadows from hundreds of light sources in real time and within a bounded memory footprint. In addition, we explore the utility of ray tracing for shadows from many lights and present a hybrid algorithm combining ray tracing with cube maps to exploit their respective strengths. Our solution supports real-time performance with hundreds of lights in fully dynamic high-detail scenes.
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http://dx.doi.org/10.1109/TVCG.2015.2418772DOI Listing
June 2015

A model for habitat selection and species distribution derived from central place foraging theory.

Oecologia 2014 Jun 3;175(2):537-48. Epub 2014 Apr 3.

Biodiversity Unit, Department of Biology, Lund University, Ecology Building, 223 62, Lund, Sweden,

We have developed a habitat selection model based on central place foraging theory. An individual's decision to include a patch in its habitat depends on the marginal fitness contribution of that patch, which is characterized by its quality and distance to the central place. The essence of the model we have developed is a fitness isocline which is a function of patch quality and travel time to the patch. It has two parameters: the maximum travel distance to a patch of infinite quality and a coefficient that appropriately scales quality by travel time. Patches falling below the isocline will have positive marginal fitness values and should be included in the habitat. The maximum travel distance depends on the availability and quality of patches, as well as on the forager's life history, whereas the scaling parameter mostly depends on life history properties. Using the model, we derived a landscape quality metric (which can be thought of as a connectivity measure) that sums the values of available habitat in the landscape around a central place. We then fitted the two parameters to foraging data on breeding white storks (Ciconia ciconia) and estimated landscape quality, which correlated strongly with reproductive success. Landscape quality was then calculated for a larger region where re-introduction of the species is currently going on in order to demonstrate how this model can also be regarded as a species distribution model. In conclusion, we have built a general habitat selection model for central place foragers and a novel way of estimating landscape quality based on a behaviorally scaled connectivity metric.
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http://dx.doi.org/10.1007/s00442-014-2931-9DOI Listing
June 2014

Is population structure in the European white stork determined by flyway permeability rather than translocation history?

Ecol Evol 2013 Dec 7;3(15):4881-95. Epub 2013 Nov 7.

Centre for Research and Conservation - Royal Zoological Society of Antwerp Koningen Astridplein 26, 2018, Antwerp, Belgium.

European white stork are long considered to diverge to eastern and western migration pools as a result of independent overwintering flyways. In relatively recent times, the western and northern distribution has been subject to dramatic population declines and country-specific extirpations. A number of independent reintroduction programs were started in the mid 1950s to bring storks back to historical ranges. Founder individuals were sourced opportunistically from the Eastern and Western European distributions and Algeria, leading to significant artificial mixing between eastern and western flyways. Here we use mitochondrial and microsatellite DNA to test the contention that prior to translocation, eastern and western flyways were genetically distinct. The data show a surprising lack of structure at any spatial or temporal scale suggesting that even though birds were moved between flyways, there is evidence of natural mixing prior to the onset of translocation activities. Overall a high retention of genetic diversity, high N ef , and an apparent absence of recent genetic bottleneck associated with early 20th century declines suggest that the species is well equipped to respond to future environmental pressures.
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http://dx.doi.org/10.1002/ece3.845DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3892355PMC
December 2013

Phosphorus and carbon availability regulate structural composition and complexity of AM fungal mycelium.

Mycorrhiza 2014 Aug 18;24(6):443-51. Epub 2014 Jan 18.

Department of Biology, Lund University, Sölvegatan 37, 223 62, Lund, Sweden.

The regulation of the structural composition and complexity of the mycelium of arbuscular mycorrhizal (AM) fungi is not well understood due to their obligate biotrophic nature. The aim of this study was to investigate the structure of extraradical mycelium at high and low availability of carbon (C) to the roots and phosphorus (P) to the fungus. We used monoxenic cultures of the AM fungus Rhizophagus irregularis (formerly Glomus intraradices) with transformed carrot roots as the host in a cultivation system including a root-free compartment into which the extraradical mycelium could grow. We found that high C availability increased hyphal length and spore production and anastomosis formation within individual mycelia. High P availability increased the formation of branched absorbing structures and reduced spore production and the overall length of runner hyphae. The complexity of the mycelium, as indicated by its fractal dimensions, increased with both high C and P availability. The results indicate that low P availability induces a growth pattern that reflects foraging for both P and C. Low C availability to AM roots could still support the explorative development of the mycelium when P availability was low. These findings help us to better understand the development of AM fungi in ecosystems with high P input and/or when plants are subjected to shading, grazing or any management practice that reduces the photosynthetic ability of the plant.
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http://dx.doi.org/10.1007/s00572-014-0557-8DOI Listing
August 2014

Bushmeat hunting changes regeneration of African rainforests.

Proc Biol Sci 2013 May 20;280(1759):20130246. Epub 2013 Mar 20.

Department of Biology, Biodiversity unit, Lund University, Ecology Building, Lund 22362, Sweden.

To assess ecological consequences of bushmeat hunting in African lowland rainforests, we compared paired sites, with high and low hunting pressure, in three areas of southeastern Nigeria. In hunted sites, populations of important seed dispersers-both small and large primates (including the Cross River gorilla, Gorilla gorilla diehli)-were drastically reduced. Large rodents were more abundant in hunted sites, even though they are hunted. Hunted and protected sites had similar mature tree communities dominated by primate-dispersed species. In protected sites, seedling communities were similar in composition to the mature trees, but in hunted sites species with other dispersal modes dominated among seedlings. Seedlings emerging 1 year after clearing of all vegetation in experimental plots showed a similar pattern to the standing seedlings. This study thus verifies the transforming effects of bushmeat hunting on plant communities of tropical forests and is one of the first studies to do so for the African continent.
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http://dx.doi.org/10.1098/rspb.2013.0246DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3619513PMC
May 2013

Assessing habitat quality of farm-dwelling house sparrows in different agricultural landscapes.

Oecologia 2012 Apr 29;168(4):959-66. Epub 2011 Oct 29.

Biodiversity Section, Department of Biology, Lund University, Ecology Building, 223 62, Lund, Sweden.

Having historically been abundant throughout Europe, the house sparrow (Passer domesticus) has in recent decades suffered severe population declines in many urban and rural areas. The decline in rural environments is believed to be caused by agricultural intensification, which has resulted in landscape simplification. We used giving-up densities (GUDs) of house sparrows feeding in artificial food patches placed in farmlands of southern Sweden to determine habitat quality during the breeding season at two different spatial scales: the landscape and the patch scale. At the landscape scale, GUDs were lower on farms in homogeneous landscapes dominated by crop production compared to more heterogeneous landscapes with mixed farming or animal husbandry. At the patch level, feeding patches with a higher predation risk (caused by fitting a wall to the patch to obstruct vigilance) had higher GUDs. In addition, GUDs were positively related to population size, which strongly implies that GUDs reflect habitat quality. However, the increase followed different patterns in homogeneous and heterogeneous landscapes, indicating differing population limiting mechanisms in these two environments. We found no effect of the interaction between patch type and landscape type, suggesting that predation risk was similar in both landscape types. Thus, our study suggests that simplified landscapes constitute a poorer feeding environment for house sparrows during breeding, that the population-regulating mechanisms in the landscapes differ, but that predation risk is the same across the landscape types.
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http://dx.doi.org/10.1007/s00442-011-2169-8DOI Listing
April 2012

Effects of season, water and predation risk on patch use by birds on the African savannah.

Oecologia 2010 Nov 24;164(3):637-45. Epub 2010 Sep 24.

AP Leventis Ornithological Research Institute, Jos, Nigeria.

Birds from semi-arid regions may suffer dehydration during hot, dry seasons with low food availability. During this period, both energetic costs and water requirements for thermoregulation increase, limiting the scope of activity. For granivorous birds feeding on dry seeds, this is a major challenge and availability of water may affect the value of food. Water availability could (1) increase the value of a food patch when the surrounding environment is poor, due to an increase in the marginal value of energy, and (2) increase the value of the entire environment to the forager when environmental quality increases, due to an increase in the marginal value of time. We aimed to test this by measuring giving-up densities (GUDs, remaining food densities after foraging) of granivorous birds in the presence or absence of filled water pots, at different seasons differing in background food and water availability. We predicted that GUDs will increase with water provision during the dry season with moderate food, but in the early wet season with low food and water availability, GUDs will decrease with water provision. Later in the wet season, our experimental addition of water should have no effect. During seasons with low water availability but differing in food availability, results confirmed our predictions. However, when water became more abundant as the wet season progressed, birds still foraged more intensely during days with added water. In all seasons, birds fed more intensely in cover than in exposed areas, suggesting that predation risk rather than heat influenced microhabitat selection.
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http://dx.doi.org/10.1007/s00442-010-1781-3DOI Listing
November 2010

The Hansson Twin Hook is adequate for fixation of trochanteric fractures: 2 fixation failures in a series of 157 prospectively followed patients.

Acta Orthop 2008 Oct;79(5):602-8

Department of Orthopedics, Helsingborg Hospital, Helsingborg, Sweden.

Background And Purpose: The Hansson Twin Hook (HTH) is an alternative to the lag screw in the treatment of trochanteric fractures. In osteoporotic bone, mechanical tests have indicated that the HTH has better fixation properties than the lag screw. We evaluated the fixation stability of the HTH in a large series of elderly patients with trochanteric fractures. Many surgeons were involved in assessment of whether the device was user-friendly.

Patients And Methods: In a prospective bicentric study, 55 surgeons used the HTH and a standard plate in 157 consecutive patients with trochanteric fractures, 83% of which were unstable. The mean age of the patients was 83 (43-98) years. They were followed regularly clinically and radiographically for at least 4 months, with a radiographic file search at 2 years.

Results: Technical errors occurred intraoperatively in 7 cases. The reduction of the fracture was inaccurate in these patients; thus, the HTH had not been placed centrally in the femoral head. One of these errors was immediately and easily corrected without interference with the standard plate, and caused no further problems. 2 of the remaining 6 intraoperative errors developed into failures of fixation during the 2-year period.

Interpretation: The HTH gives adequate fixation in the bone of elderly patients with trochanteric fractures and has a low failure rate. It is also easy to use.
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http://dx.doi.org/10.1080/17453670810016605DOI Listing
October 2008

A guide to central place effects in foraging.

Theor Popul Biol 2008 Aug 30;74(1):22-33. Epub 2008 Apr 30.

Department of Animal Ecology, Lund University, Sweden.

We develop a general patch-use model of central place foraging, which subsumes and extends several previous models. The model produces a catalog of central place effects predicting how distance from a central place influences the costs and benefits of foraging, load-size, quitting harvest rates, and giving-up densities. In the model, we separate between costs that are load-size dependent, i.e. a direct effect of the size of the load, and load-size independent effects, such as correlations between distance and patch qualities. We also distinguish between predictions of between- and within-environment comparisons. Foraging costs, giving-up densities and quitting harvest rates should almost always increase with distance with these effects amplified by increases in metabolic costs, predation risk and load-costs. With respect to load-size: when comparing foraging in patches within an environment, we should often expect smaller loads to be taken from distant patches (negative distance-load correlation). However, when comparing between environments, there should be a positive correlation between average distance and load-size.
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http://dx.doi.org/10.1016/j.tpb.2008.04.005DOI Listing
August 2008

Genetic origin and success of reintroduced white storks.

Authors:
Ola Olsson

Conserv Biol 2007 Oct;21(5):1196-206

Department of Animal Ecology, Lund University, Ecology Building, SE-223 62 Lund, Sweden.

After their local extinction in 1954, White Storks (Ciconia ciconia) were reintroduced to Sweden in 1989. The founder population for the reintroduced birds originated in North Africa, rather than from the closest breeding population in northeastern Europe (defined here as native). A number of wild storks have immigrated spontaneously, and a few others of native origin have been acquired for captive breeding. Over the 17 years, 103 of the 241 breeding events by free storks have been by pairs in which at least one parent had some native ancestry. The pedigree for all birds is known, and from this I calculated the proportion of native ancestry for each individual, the inbreeding coefficient, and the kinship between parents. I analyzed how these genetic factors, together with rainfall during breeding, supplementary feeding, and management of the storks (whether parents were born or raised in captivity or free), affected brood size. I also analyzed whether storks with native ancestry had a higher likelihood of migrating. Together with weather and supplementary feeding during the breeding period, genetic origin strongly affected breeding performance. Pairs with entirely native ancestry had on average twice as many chicks as those of entirely African ancestry. Inbreeding and kinship between parents, or management of the parents, did not influence breeding performance significantly. Reproductive success of the African storks in Sweden is so low that they cannot form a sustainable population. In addition, birds with some native ancestry were more likely to migrate from Sweden than those with entirely African ancestry. The difference in performance between native and African storks may be due either to local adaptations or to the bottleneck that the African founding population went through during captive breeding. Overall, my results imply that use of a correct source population for reintroduction programs may be of greater consequence for the program's success than other genetic considerations or management of individuals.
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http://dx.doi.org/10.1111/j.1523-1739.2007.00763.xDOI Listing
October 2007

Information and its use by animals in evolutionary ecology.

Trends Ecol Evol 2005 Apr 25;20(4):187-93. Epub 2005 Jan 25.

Centre for Ecology and Conservation, University of Exeter in Cornwall, Tremough Campus, Penryn, UK, TR10 9EZ.

Information is a crucial currency for animals from both a behavioural and evolutionary perspective. Adaptive behaviour relies upon accurate estimation of relevant ecological parameters; the better informed an individual, the better it can develop and adjust its behaviour to meet the demands of a variable world. Here, we focus on the burgeoning interest in the impact of ecological uncertainty on adaptation, and the means by which it can be reduced by gathering information, from both 'passive' and 'responsive' sources. Our overview demonstrates the value of adopting an explicitly informational approach, and highlights the components that one needs to develop useful approaches to studying information use by animals. We propose a quantitative framework, based on statistical decision theory, for analysing animal information use in evolutionary ecology. Our purpose is to promote an integrative approach to studying information use by animals, which is itself integral to adaptive animal behaviour and organismal biology.
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http://dx.doi.org/10.1016/j.tree.2005.01.010DOI Listing
April 2005

Geography, biogeography, and why some countries are rich and others are poor.

Proc Natl Acad Sci U S A 2004 Mar 25;101(10):3715-20. Epub 2004 Feb 25.

Department of Economics, Göteborg University, Box 640, 40530 Göteborg, Sweden.

The most important event in human economic history before the industrial revolution was the Neolithic transition from a nomadic hunter-gatherer lifestyle to sedentary agriculture, beginning approximately 10,000 years ago. The transition made possible the human population explosion, the rise of non-food-producing specialists, and the acceleration of technological progress that led eventually to the industrial revolution. But the transition occurred at different times in different regions of the world, with big consequences for the present-day economic conditions of populations indigenous to each region. In this article, we show that differences in biogeographic initial conditions and in geography largely account for the different timings of the Neolithic transition and, thereby, ultimately help account for the 100-fold differences among the prosperity of nations today. The effects of biogeography and geography on the wealth of nations are partly mediated by the quality of present-day institutions but also are partly independent of institutional quality.
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http://dx.doi.org/10.1073/pnas.0305531101DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC376185PMC
March 2004

Does information sharing promote group foraging?

Proc Biol Sci 2003 Jun;270(1520):1137-41

Department of Natural Sciences, University of Skövde, PO Box 408, SE-541 28 Skövde, Sweden.

Individuals may join groups for several reasons, one of which is the possibility of sharing information about the quality of a foraging area. Sharing information in a patch-foraging scenario gives each group member an opportunity to make a more accurate estimate of the quality of the patch. In this paper we present a mathematical model in which we study the effect of group size on patch-leaving policy and per capita intake rate. In the model, group members share information equally in a random search for food. Food is distributed in patches according to a negative binomial distribution. A prediction from our model is that, the larger the group, the earlier each group member should leave the current patch. We also find that the benefit from enhanced exchange of information does not exceed the cost of sharing food with group members. The per capita intake rate decreases as the group size increases. Therefore, animals should only form groups when other factors outweigh the costs, which is easiest to achieve when the travelling time is short.
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http://dx.doi.org/10.1098/rspb.2003.2352DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1691354PMC
June 2003

Variability of patch type preferences in relation to resource availability and breeding success in a bird.

Oecologia 2001 May 1;127(3):435-443. Epub 2001 May 1.

Department of Ecology, Animal Ecology, Lund University, Ecology Building, 223-62, Lund, Sweden.

This paper investigates how variability in partial foraging preferences for patch types can be used as a behavioral indicator of the energetic value of that patch type, and of overall food availability in the territory. The species studied was the lesser spotted woodpecker (Dendrocopos minor) and the patch types it uses are four groups of tree species (oak Quercus robur, birch Betula pendula, B. pubescens, alder Alnus glutinosa, and lime Tilia cordata), in which it feeds upon wood-living insect larvae. We partition the variation in foraging preferences into three scales. Firstly, within territories, the foraging preference for a tree species group was positively related to the prey density in that species group. That is, the preferences measure the patch types' energetic profitabilities. This result should be general in cases like the present, where the costs of using different alternatives do not differ substantially. It may therefore be the preferred behavioral indicator in determining the relative benefits associated with different alternatives. Secondly, between the seven years of study, much of the variation in tree species group preferences was attributable to measured fluctuations in the density of one important prey species (Argyresthia goedarthella, Argyresthidae, Lepidoptera), which occurred in some years on birch, in others on alder, and in one year was virtually absent. Thus, in concordance with the previous result, the values of these tree species groups fluctuated between years according to prey density. Thirdly, between territories, we found that the preference for one tree species, lime, was higher in areas where it was more abundant. We attribute this to the fact that the density (per patch) of at least one important prey species (Stenostola dubia, Cerambycidae, Coleoptera) on lime increased with the abundance of its host tree species in the territory. That is, the overall food availability was higher in territories where lime was more common. Hence, the preference for lime estimates overall food availability. This conclusion is strengthened by two additional facts: the preference for lime correlates positively (1) with the average giving-up density of food, which has previously been shown to estimate overall food availability in the territories, and (2) with reproductive success, at least during the early stages of reproduction.
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http://dx.doi.org/10.1007/s004420000596DOI Listing
May 2001