| 1. |
- Diaz, JA, et al.
(författare)
-
Reproductive investment of a lacertid lizard in fragmented habitat
- 2005
-
Ingår i: Conservation Biology. - : Wiley. - 0888-8892 .- 1523-1739. ; 19:5, s. 1578-1585
-
Tidskriftsartikel (refereegranskat)abstract
- We studied the effect of habitat fragmentation on female reproductive investment in a widespread lacertid lizard (Psammodromus algirus) in a mixed-forest archipelago of deciduous and evergreen oak woods in northern Spain. We captured gravid females in fragments (<= 10 ha) and forests (>= 200 ha) and brought them to the laboratory, where they laid their eggs. We incubated the eggs and released the first cohort of juveniles into the wild to monitor their survival. Females from fragments produced a smaller clutch mass and laid fewer eggs (relative to mean egg mass) than females of similar body size from forests. Lizards did not trade larger clutches for larger offspring, however, because females from fragments did not lay larger eggs (relative to their number) than females from forests. Among the first cohort of juveniles, larger egg mass and body size increased the probability of recapture the next year Thus, fragmentation decreased the relative fecundity of lizards without increasing the quality of their offspring. Reduced energy availability, increased predation risk, and demographic stochasticity could decrease the fitness of lizards in fragmented habitats, which could contribute to the regional scarcity of this species in agricultural areas sprinkled with small patches of otherwise suitable forest. Our results show that predictable reduction of reproductive output with decreasing size of habitat patches can be added to the already known processes that cause inverse density dependence at low population numbers.
|
|
| 2. |
- Larsson, Mattias, et al.
(författare)
-
Pheromones for monitoring rare and threatened insects: exploiting a pheromone-kairomone system to estimate prey and predator abundance
- 2009
-
Ingår i: Conservation Biology. - : Wiley. - 0888-8892 .- 1523-1739. ; 23:6, s. 1516-1525
-
Tidskriftsartikel (refereegranskat)abstract
- Pheromone-based monitoring is a promising new method for assessing the conservation status of many threatened insect species. We examined the versatility and usefulness of pheromone-based monitoring by integrating a pheromone–kairomone trapping system and pitfall trapping system in the monitoring of two saproxylic beetles, the hermit beetle Osmoderma eremita (Coleoptera: Scarabaeidae) and its predator Elater ferrugineus (Coleoptera: Elateridae), which live inside hollow trees. We performed mark–recapture studies of both species with unbaited pitfall traps in oak hollows combined with pheromone-baited funnel traps suspended from oak branches to intercept dispersing individuals. For O. eremita, the integrated trapping system showed that the population in the study sites may be considerably higher than estimates based on extrapolation from pitfall trapping alone (approximately 3400 vs. 1100 or 1800 individuals, respectively). Recaptures between odor-baited funnel traps showed that males and females had similar dispersal rates, but estimating the number of dispersing individuals was problematic due to declining recapture probability between subsequent capture events. Our conservative estimate, assuming a linear decrease in capture probability, suggested that around 1900 individuals, or at least half of the O. eremita population, may perform flights from their natal host trees, representing higher dispersal rates than previous estimates. E. ferrugineus was rarely caught in pitfall traps. One hundred thirty-nine individuals, likely almost exclusively females, were caught in odor-baited funnel traps with approximately 4% recapture probability. If recapture probability over consecutive capture events follows that of O. eremita, this would correspond to a total population size of 2500–3000 individuals of the predator; similar to its supposed prey O. eremita. Our results demonstrate that pheromone-based monitoring is a valuable tool in the study of species or life-history stages that would otherwise be inaccessible.
|
|
| 3. |
- Olsson, Ola
(författare)
-
Genetic origin and success of reintroduced white storks
- 2007
-
Ingår i: Conservation Biology. - : Wiley. - 0888-8892 .- 1523-1739. ; 21:5, s. 1196-1206
-
Tidskriftsartikel (refereegranskat)abstract
- 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 bow 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 Aftican 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.
|
|
| 4. |
- Pahkala, Maarit, et al.
(författare)
-
Lethal and Sublethal Effects of UV-B/pH Synergism on Common Frog Embryos
- 2002
-
Ingår i: Conservation Biology. - : Wiley. - 0888-8892 .- 1523-1739. ; 16:4, s. 1063-1073
-
Tidskriftsartikel (refereegranskat)abstract
- Although the negative effects of ultraviolet-B ( UV-B) radiation on the development of many amphibian species have been demonstrated, some speciessuch as the common frog ( Rana temporaria)seem to be tolerant of UV-B radiation. The amount of UV-B radiation received is likely to vary among populations of the same species, but little is known about geographic variation in UV-B tolerance. Similarly, although UV-B radiation can have synergistic effects with other stressors, no studies have focused on geographic variation of these effects on amphibians. We investigated the synergistic effects of UV-B radiation and low pH on hatchability and early development of R. temporaria embryos in a factorial laboratory experiment with animals originating from southern and northern Sweden. Newly fertilized eggs were exposed to three different UV-B treatments (no UV-B [control, 1.254 k/J/m 2[normal and 1.584 k/J/m 2[26 enhanced) and two pH treatments (4.5 [low and 7.6 [neutral). Ultraviolet-B radiation in combination with low pH lead to markedly (approximately 50) reduced survival rates and increased (approximately 30) frequency of developmental anomalies in the northern but not in the southern population. The UV-B- exposed embryos hatched at smaller size in the southern population, whereas low pH reduced hatchling size in both populations. In both populations and pH treatments, embryos in the normal UV-B treatment developed significantly faster than embryos in the enhanced or control UV-B treatments. No interaction between pH and UV-B on developmental rates or hatchling size was detected. The results demonstratecontrary to earlier beliefthat R. temporaria embryos are not insensitive to increased levels of UV-B radiation. The lethal effects of UV-B radiation may, however, become manifested only in combination with other stressors, such as low pH, and the effects of this synergism may differ among different populations of the same species.
|
|
| 5. |
- Peterson, Garry, 1969-
(författare)
-
A Cross-National Analysis of How Economic Inequality Predicts Biodiversity Loss
- 2009
-
Ingår i: Conservation Biology. - : Wiley. - 0888-8892 .- 1523-1739. ; 23:5, s. 1304-1313
-
Tidskriftsartikel (refereegranskat)abstract
- We used socioeconomic models that included economic inequality to predict biodiversity loss, measured as the proportion of threatened plant and vertebrate species, across 50 countries. Our main goal was to evaluate whether economic inequality, measured as the Gini index of income distribution, improved the explanatory power of our statistical models. We compared four models that included the following: only population density, economic footprint (i.e., the size of the economy relative to the country area), economic footprint and income inequality (Gini index), and an index of environmental governance. We also tested the environmental Kuznets curve hypothesis, but it was not supported by the data. Statistical comparisons of the models revealed that the model including both economic footprint and inequality was the best predictor of threatened species. It significantly outperformed population density alone and the environmental governance model according to the Akaike information criterion. Inequality was a significant predictor of biodiversity loss and significantly improved the fit of our models. These results confirm that socioeconomic inequality is an important factor to consider when predicting rates of anthropogenic biodiversity loss.
|
|
| 6. |
- Berglund, Håkan, et al.
(författare)
-
Quantifying habitat requirements of tree-living species in fragmented boreal forests with Bayesian methods
- 2009
-
Ingår i: Conservation Biology. - : Wiley. - 0888-8892 .- 1523-1739. ; 23:5, s. 1127-1137
-
Tidskriftsartikel (refereegranskat)abstract
- Quantitative conservation objectives require detailed consideration of the habitat requirements of target species. Tree-living bryophytes, lichens, and fungi are a critical and declining biodiversity component of boreal forests. To understand their requirements, Bayesian methods were used to analyze the relationships between the occurrence of individual species and habitat factors at the tree and the stand scale in a naturally fragmented boreal forest landscape. The importance of unexplained between-stand variation in occurrence of species was estimated, and the ability of derived models to predict species' occurrence was tested. The occurrence of species was affected by quality of individual trees. Furthermore, the relationships between occurrence of species at the tree level and size and shape of stands indicated edge effects, implying that some species were restricted to interior habitats of large, regular stands. Yet for the habitat factors studied, requirements of many species appeared similar. Species occurrence also varied between stands; most of the seemingly suitable trees in some stands were unoccupied. The models captured most variation in species occurrence at tree level. They also successfully accounted for between-stand variation in species occurrence, thus providing realistic simulations of stand-level occupancy of species. Important unexplained between-stand variation in species occurrence warns against a simplified view that only local habitat factors influence species' occurrence. Apparently, similar stands will host populations of different sizes due to historical, spatial, and stochastic factors. Thus, habitat suitability cannot be assessed simply by population sizes, and stands lacking a species may still provide suitable habitat and merit protection.
|
|
| 7. |
- Berglund, H., et al.
(författare)
-
Verifying an Extinction Debt among Lichens and Fungi in Northern Swedish Boreal Forests
- 2005
-
Ingår i: Conservation Biology. - : John Wiley & Sons. - 0888-8892 .- 1523-1739. ; 19:2, s. 338-348
-
Tidskriftsartikel (refereegranskat)abstract
- Destruction and fragmentation of natural habitats results in small species populations that face increased risk of extinction. A time delay may be involved in the regional extinction of species, and the number of species that eventually may go extinct in the future is called the “extinction debt.” In boreal Sweden, we examined whether the number of epiphytic crustose lichens and wood-inhabiting fungi in old-growth forest remnants diverges from species richness levels in forest patches that have been naturally isolated for millennia. An excess of species in forest remnants could indicate the presence of an extinction debt. Observed species richness in 32 old-growth forest remnants (also called woodland key habitats [WKHs]) was compared with predicted species richness. To predict species richness we used regression models based on data from 46 isolated old-growth forest patches in a forest-wetland matrix. The reference landscape is ancient and assumed to reflect the conditions of insular floras in dynamic equilibrium. Stand factors constituted predictive variables in the models. The observed number of lichen species was higher than expected (i.e., an extinction debt among lichens may exist). By contrast, there was no significant difference between observed and expected species richness among wood-inhabiting fungi. The species richness of wood-inhabiting fungi has adjusted to the changes in forest and landscape structure more rapidly than the species richness of lichens. Differences in substrate dynamics between epiphytes on living trees and species growing on decaying logs might explain the difference between species groups. The results also indicate that population densities of red-listed species were low, which may result in continuing extinctions of red-listed species. The importance of WKHs might be overvalued because species may be lost if conservation efforts consider only protection and preservation of WKHs.
|
|
| 8. |
- Berglund, Håkan, et al.
(författare)
-
Verifying an extinction debt in north Swedish boreal forests
- 2005
-
Ingår i: Conservation biology. - : Wiley. - 0888-8892 .- 1523-1739. ; 19:2, s. 338-348
-
Tidskriftsartikel (refereegranskat)abstract
- Destruction and fragmentation of natural habitats results in small species populations that face increased risk of extinction. A time delay may be involved in the regional extinction of species, and the number of species that eventually may go extinct in the future is called the "extinction debt." In boreal Sweden, we examined whether the number of epiphytic crustose lichens and wood-inhabiting fungi in old-growth forest remnants diverges from species richness levels in forest patches that have been naturally isolated for millennia. An excess of species in forest remnants could indicate the presence of an extinction debt. Observed species richness in 32 old-growth forest remnants (also called woodland key habitats [WKHs]) was compared with predicted species richness. To predict species richness we used regression models based on data from 46 isolated old-growth forest patches in a forest-wetland matrix. The reference landscape is ancient and assumed to reflect the conditions of insular floras in dynamic equilibrium. Stand factors constituted predictive variables in the models. The observed number of lichen species was higher than expected (i.e., an extinction debt among lichens may exist). By contrast, there was no significant difference between observed and expected species richness among wood-inhabiting fungi. The species richness of wood-inhabiting fungi has adjusted to the changes in forest and landscape structure more rapidly than the species richness of lichens. Differences in substrate dynamics between epiphytes on living trees and species growing on decaying logs might explain the difference between species groups. The results also indicate that population densities of red-listed species were low, which may result in continuing extinctions of red-listed species. The importance of WKHs might be overvalued because species may be lost if conservation efforts consider only protection and preservation of WKHs.
|
|
| 9. |
- Cassel, Anna, et al.
(författare)
-
Effects of population size and food stress on fitness-related characters in the scarce heath, a rare butterfly in Western Europe
- 2001
-
Ingår i: Conservation Biology. - : Blackwell Science Publishing. - 0888-8892 .- 1523-1739. ; 15:6, s. 1667-1673
-
Tidskriftsartikel (refereegranskat)abstract
- Abstract: Knowledge about the effects of inbreeding in natural populations is scarce, especially in invertebrates. We analyzed to what extent fitness-related traits in the scarce heath ( Coenonympha hero), a butterfly, are affected by population size and isolation and whether differences in food quality influence these effects. We categorized nine populations as either large or small and isolated. Full-sib groups of offspring from 27 females were followed under seminatural conditions. Because of increased zygote mortality, egg hatchability was significantly lower in the small and isolated populations than in the large ones. Population category had no effect on larval weight under optimal conditions, but weight was significantly lower in the small-isolated category with low food quality. The effects of inbreeding can thus be hidden when conditions are benign but can appear under stress. Survival also differed significantly between population categories, and larval developmental time tended to be longer in the small-isolated category, irrespective of food conditions. We suggest that the differences in fitness between offspring from large and small isolated populations are at least partly due to inbreeding. This adds a further threat to a species that is already suffering from decreasing population sizes and increasing isolation among populations.
|
|
| 10. |
|
|
