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The Colorado potato beetle (CPB), a serious pest of potato, is currently spreading north in Europe. We investigated the risk of CPB establishment in Finland and control methods for the case when beetle life history characters change due to global warming or as an adaptation to colder climate. Analysis with a spatially explicit simulation model supported the current management policy in Finland (efficient eradication and one year field quarantine) but changes in CPB viability, such as decreased winter mortality or increased number of offspring would render them inefficient. Longer quarantine times would be needed to effectively prevent the CPB establishment and spread. As an option we investigated Bt-potato cultivation integrated to other control methods and found that it was already efficient when used as a sole strategy but its benefits may be reduced by the adaptability of the Colorado potato beetle.
Fluctuating asymmetry (FA) as a measure of environmental stress was studied in polar bear (Ursus maritimus) skulls from East Greenland (n = 300, collected 1892–2004) and Svalbard (n = 391, collected 1950–2004). Nine metric traits in skull and lower jaw were measured. FA levels of each trait were compared between sex/age groups (subadults, adult females, adult males), periods (≤ 1960, ≥ 1960), and localities (East Greenland, Svalbard). The period ≤ 1960 was chosen to represent a period prior to the appearance of organohalogen pollution in the Arctic. Results indicated that Svalbard bears generally had a higher level of FA than those of East Greenland. Overall, no substantial evidence of a linkage between FA and organohalogens was found. Instead, indications were of subpopulations with declining levels of FA over time, suggesting the existence of positive population level effects powerful enough to overrule the influence of stress caused by global warming, pollution, and overharvesting.
We present an example of background statistics in studies of fluctuating asymmetry (FA); calculations of asymmetry, measurement error (ME), and repeatability. Nine bilateral metric traits in skulls and lower jaws of 691 East Greenland and Svalbard polar bears (Ursus maritimus) were measured twice, and examined for asymmetry. The skulls were collected in the period 1892–2004. In this study, 2.0% of the FA data were identified and treated as outliers, which is less than in comparable studies. FA for each trait amounted to 0.1%–3% of the average size of the corresponding trait. The magnitude of FA generally increased with trait size. For every trait measured, ME was found to be smaller than FA. The repeatability of the traits was inversely proportional to ME. Five of the nine traits had a repeatability of 90% or more, which is similar to what has been reported in other studies.
The termination of agricultural production in intensively managed fields leads to the succession of weed communities and to changes in the vegetation cover and food supply for animals. We studied a population of the common vole on a regularly managed alfalfa field in southern Moravia (Czech Republic) during two and a half consecutive years. When the field was set aside, the vegetation cover transformed significantly and we studied the same vole population for the next three years. Multi-annual variation in population size disappeared; maximal abundances decreased, and mean body size tended to be lower in the weed-filled habitat. We observed conspicuous seasonal patterns in the proportion of breeding females, sex ratio and in litter size variation; however these patterns did not depend on the field management regime. The set-aside field had a strong effect on vole population dynamics; however, other well-designed studies are needed to distinguish between the possible causal processes (immigration, natality or survival) of the observed changes.
Partial filial cannibalism by parental males in fish has been regarded as an adaptive behaviour that compensates for the toll that parental care exacts on their body condition, which is supported by empirical evidence. Here we report that parental males of a nest breeding fish enhance their initial body condition and sustain growth through partial filial cannibalism. Males of the long-snout clingfish (Diademichthys lineatus) use scarcely available empty shells as nests, which limit the number of breeding males. Males continuously breed up to 4 months, during which they hardly leave the nests. Soon after breeding starts, all care-giving males exclusively and frequently consume some of their own eggs. In contrast to previous reports on fish cannibalism, almost all care-giving males grew and enhanced their initial body condition from the early days of care, where males with larger and better-conditioned bodies cannibalised more eggs. Male—male fights for nests were frequently observed: males with larger and more robust bodies won and sometimes took over breeding nests, and it is likely that defeated males could not breed unless they occupy a nest again. These observations indicate that in this fish, partial filial cannibalism produces cannibals of large and robust bodies, and may be advantageous to care-giving males in defending nests against rival males. We suggest that the ability to defend a nest will ensure a longer care-period, and thus, a higher reproductive output. This is the first documented evidence that filial cannibalism enhances the initial body condition of cannibals.
The correct use and interpretation of statistical measures is often challenging for fieldoriented ecologists. One such basic measure is the odds ratio (OR), which enables the comparison of two proportions. Odds ratio is the pivotal concept in the simple analyses of proportions in two-way contingency tables, as well as in complex logit model approaches. Here, we clarify the use and interpretation of the odds ratio in ecological research. We show that the odds ratio is both a statistical and an ecological solution to quantifying the direction and magnitude of discrepancy between proportions. To enhance comparison of suppressing (with OR below one) and promoting (with OR above one) factors, we propose that the odds ratio should always be reported as a value above one, together with an exponent (1 or -1) to denote the direction of the effect. The odds ratio supports powerful ecological interpretations in the comparison of proportions and thus should become a standard concept in ecological papers.
We counted droppings of ungulates and hare on transects in order to assess (1) seasonal changes in detectability and disappearance of pellet groups, (2) whether the detectability varies according to the forest type, and (3) the degree of misidentification between pellets of roe deer (Capreolus capreolus) and red deer (Cervus elaphus). The summer decrease in detectability of pellet groups was the most important factor for all species but European bison (Bison bonasus). Detectability did not significantly depend on forest type. In summer, decay reduced significantly the dropping density of red deer, roe deer, wild boar (Sus scrofa) and European hare (Lepus europaeus) but not those of bison and moose (Alces alces). Misidentification of roe and red deer droppings did not influence much density estimates of red deer but resulted in an important overestimation of roe deer in areas were roe deer were much less common than red deer.