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Povzetek: Survival and cause-specific mortality rates are vital for evidence-based population forecasting and conservation, particularly for large carnivores, whose populations are often vulnerable to human-caused mortalities. It is therefore important to know the relationship between anthropogenic and natural mortality causes to evaluate whether they are additive or compensatory. Further, the relation between survival and environmental covariates could reveal whether specific landscape characteristics influence demographic performance. We used telemetry data on 681 Eurasian lynx (Lynx lynx), a model apex predator with large spatial requirements, that were tracked across their European distribution. Through time-to-event analyses, we sought to determine the variables associated with differences in their survival. Illegal killing was the main cause of mortality (33.8%), and mortality rates were similar in protected and hunted populations (8.6% and 7.0% per year, respectively). Survival varied greatly across populations (70–95% per year). Across all study sites, higher hunting and anthropogenic mortality rates were partially compensated by lower rates of other mortality causes but not by natural mortality alone. Variation in survival depended on sex (female survival was 1.5 times greater than male survival) and seasonality (highest risk during hunting season and winter), and lower survival rates were correlated with higher human modification of landscapes at both coarse (home range composition) and fine (habitat use within home range) scales. Some variation in survival was driven by unobserved factors, which, given the high rates of human-caused mortalities, including illegal killing, are of foremost concern. Due to the low natural mortality rates in protected and hunted populations, we conclude that anthropogenic causes of mortality are likely close to additive, such that maintaining or increasing refuge habitat with little human disturbance is critical to lynx conservation.
Ključne besede: cause-specific mortality, compensatory mortality, Eurasian lynx, large carnivore, Lynx lynx, survival
Objavljeno v DiRROS: 23.04.2025; Ogledov: 288; Prenosov: 112
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Povzetek: The four-eyed fir bark beetle Polygraphus proximus Blandford, 1894 (Coleoptera, Curculionidae: Scolytinae) is an invasive species that originates from the Far East. Since early 2000s, it became known as an aggressive pest causing massive dieback of Siberian fir (Abies sibirica Ledeb.) in Siberia and, to some extent, in the European part of Russia. Here, we report the first record of P. proximus in Sverdlovsk Region (the Middle Urals, Russia). In summer 2023, A. sibirica trees colonized by the pest were discovered on the territory of the “Olenyi Ruchyi” Natural Park. The dendrochronological analysis of the cores of fir trees killed by the beetle indicated that the majority (72%) of these trees died in 2021–2022, while the earliest tree death occured already in 2007 and 2009, meaning that the pest was present in the Natural Park for at least two decades. Mycological analysis of bark and wood samples of infested trees revealed the fungus colonies assigned to Grosmannia aoshimae (Ohtaka, Masuya & Yamaoka) Masuya & Yamaoka. Associated with P. proximus, this Far Eastern fungus species has spread with the beetle to Siberia and the Urals, contributing to tree mortality. Siberian fir is present on 69% of the forested area in the “Olenyi Ruchyi”. The colonization of fir trees by P. proximus recorded in the park in 2023 alarms about the high risk of the pest outbreak in the coming years, which may lead to subsequent tree death over a huge territory of the park affecting its ecological, cultural, and recreational values. To prevent the dramatic impact, it is highly urgent to take all the necessary measures to suppress the distribution and combat this alien pest.
Ključne besede: Xylophagous species, alien pest, fir forest stands, tree mortality, Grosmannia aoshimae
Objavljeno v DiRROS: 20.02.2025; Ogledov: 263; Prenosov: 161
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Povzetek: A mass mortality event is devastating the populations of the endemic bivalve Pinna nobilis in the Mediterranean Sea from early autumn 2016. A newly described Haplosporidian endoparasite (Haplosporidium pinnae) is the most probable cause of this ecological catastrophe placing one of the largest bivalves of the world on the brink of extinction. As a pivotal step towards Pinna nobilis conservation, this contribution combines scientists and citizens’ data to address the fast- and vast-dispersion and prevalence outbreaks of the pathogen. Therefore, the potential role of currents on parasite expansion was addressed by means of drift simulations of virtual particles in a high-resolution regional currents model. A generalized additive model was implemented to test if environmental factors could modulate the infection of Pinna nobilis populations. The results strongly suggest that the parasite has probably dispersed regionally by surface currents, and that the disease expression seems to be closely related to temperatures above 13.5 °C and to a salinity range between 36.5–39.7 psu. The most likely spread of the disease along the Mediterranean basin associated with scattered survival spots and very few survivors (potentially resistant individuals), point to a challenging scenario for conservation of the emblematic Pinna nobilis, which will require fast and strategic management measures and should make use of the essential role citizen science projects can play.
Ključne besede: mass mortality, endoparasites
Objavljeno v DiRROS: 24.07.2024; Ogledov: 489; Prenosov: 344
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Povzetek: Tree mortality is a key driver of forest dynamics and its occurrence is projected to increase in the future due to climate change. Despite recent advances in our understanding of the physiological mechanisms leading to death, we still lack robust indicators of mortality risk that could be applied at the individual tree scale. Here, we build on a previous contribution exploring the differences in growth level between trees that died and survived a given mortality event to assess whether changes in temporal autocorrelation, variance, and synchrony in time-series of annual radial growth data can be used as early warning signals of mortality risk. Taking advantage of a unique global ring-width database of 3065 dead trees and 4389 living trees growing together at 198 sites (belonging to 36 gymnosperm and angiosperm species), we analyzed temporal changes in autocorrelation, variance, and synchrony before tree death (diachronic analysis), and also compared these metrics between trees that died and trees that survived a given mortality event (synchronic analysis). Changes in autocorrelation were a poor indicator of mortality risk. However, we found a gradual increase in interannual growth variability and a decrease in growth synchrony in the last %20 years before mortality of gymnosperms, irrespective of the cause of mortality. These changes could be associated with drought-induced alterations in carbon economy and allocation patterns. In angiosperms, we did not find any consistent changes in any metric. Such lack of any signal might be explained by the relatively high capacity of angiosperms to recover after a stress-induced growth decline. Our analysis provides a robust method for estimating early-warning signals of tree mortality based on annual growth data. In addition to the frequently reported decrease in growth rates, an increase in inter-annual growth variability and a decrease in growth synchrony may be powerful predictors of gymnosperm mortality risk, but not necessarily so for angiosperms.
Ključne besede: tree mortality, ring-width, forest, growth, resilience indicators, drought, biotic agents, variance
Objavljeno v DiRROS: 20.07.2022; Ogledov: 1307; Prenosov: 849
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Povzetek: Reliable data and methods for assessing changes in wildlife population size over time are necessary for management and conservation. For most species, assessing abundance is an expensive and labor-intensive task that is not affordable on a frequent basis. We present a novel approach to reconstructing brown bear population dynamics in Slovenia in the period 1998-2019, based on the combination of two CMR non-invasive genetic estimates (in 2007 and 2015) and long-term mortality records, to show how the latter can help the study of population dynamics in combination with point-in-time estimates. The spring (i.e. including newborn cubs) population size estimate was 383 (CI: 336-432) bears in 1998 and 971 (CI: 825-1161) bears in 2019. In this period, the average annual population growth rate was 4.5 %. The predicted population size differed by just 7 % from the non-invasive genetic size estimate after eight years, suggesting that the method is reliable. It can predict the evolution of the population size under different management scenarios and provide information on key parameters, e.g. background mortality and the sex- and age-structure of the population. Our approach can be used for several other wildlife species, but it requires reliable mortality data over time.
Ključne besede: genetic estimates of population size, mortality records, population monitoring, population size, predictive modelling, brown bear
Objavljeno v DiRROS: 28.03.2021; Ogledov: 5080; Prenosov: 2849
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