Berglund, A. 2000: Sex role reversal in a pipefish: female ornaments as amplifying handicaps. — Ann. Zool. Fennici 37: 1–13.
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Van Dongen, S. 2000: The heritability of fluctuating asymmetry: a Bayesian hierarchical model. — Ann. Zool. Fennici 37: 15–23.
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Pasternak, A. F., Mikheev, V. N. & Valtonen, E. T. 2000: Life history characteristics of Argulus foliaceus L. (Crustacea: Branchiura) populations in Central Finland. — Ann. Zool. Fennici 37: 25–35.
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Laakkonen, J. 2000: Microparasites of three species of shrews from Finnish Lapland. — Ann. Zool. Fennici 37: 37–41.
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Bukacinski, D. & Bukacinska, M. 2000: The impact of mass outbreaks of black flies (Simuliidae) on the parental behaviour and breeding output of colonial common gulls (Larus canus). — Ann. Zool. Fennici 37: 43–49.
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Merilä, J., Laurila, A. & Pahkala, M. 2000: Effects of ambient UV-B radiation on early development of the common frog (Rana temporaria) embryos in the subarctic. — Ann. Zool. Fennici 37: 51–58.
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Kojola, I. & Laitala, H.-M. 2000: Changes in the structure of an increasing brown bear population with distance from core areas: another example of presaturation female dispersal? — Ann. Zool. Fennici 37: 59–64.
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Berglund, A. 2000: Sex role reversal in a pipefish: female ornaments as amplifying handicaps. — Ann. Zool. Fennici 37: 1–13.
The reasons for sex role reversal in the pipefish Syngnathus typhle are reviewed. In this species, females compete for males, which are choosier than females. Before mating, females display a sexual ornament, a cross-wise striped pattern along their body sides. This ornament is here shown to be an amplifier that facilitates for males to tell females of different sizes apart (males prefer larger females). When students were asked to compare bar sizes, where bars differed in "ornamentation", accuracy in estimating size was highest with "heavy ornamented" as compared with "intermediate" or "not ornamented" bars. Moreover, bar size was more accurately judged with crosswise than with lengthwise striped bars, explaining why stripes run cross- rather than lengthwise in females. The ornament is probably costly (it reduces crypsis and may be socially provocative), and it is also attractive to males. Thus, the ornament is best described as an amplifying handicap.
Van Dongen, S. 2000: The heritability of fluctuating asymmetry: a Bayesian hierarchical model. — Ann. Zool. Fennici 37: 15–23.
The genetic architecture of fluctuating asymmetry (FA) as an estimate of developmental instability (DI) has received much attention in the recent literature. Although some studies report significant heritabilities of FA (h2FA) and DI, generally heritability estimates are low. Summarizing available estimates in a recently performed fixed effects meta-analysis has provoked a lot of discussion. One objection is that heritabilities in general are population and even trait specific, and that they are influenced by a number of stochastic processes. Summarizing available information by an average value has therefore only limited relevance. Meta-analyzes should in addition attempt to model the underlying stochasticity and mean values should be accompanied by a measure of variability (i.e., random effects model). In this paper, I explore and apply a Bayesian method, hierarchical modeling, to model between-population and between-trait heterogeneity in h2FA, taking estimation accuracy into account. The analysis confirms the low values of h2FA, with a 95% confidence interval ranging between 0.009 and 0.104. In addition, between-species and -population differences in heritabilities were much higher than between-trait heterogeneity, indicating that the weak genetic effects relative to environmental influences and sampling error affect different traits in a comparable way. Although at present it is difficult to analyze how different potential influential factors contribute to the variation in h2FA, Bayesian modeling can provide a valuable statistical tool to model the underlying stochasticity of genetic parameters in general.
Pasternak, A. F., Mikheev, V. N. & Valtonen, E. T. 2000: Life history characteristics of Argulus foliaceus L. (Crustacea: Branchiura) populations in Central Finland. — Ann. Zool. Fennici 37: 25–35.
Life history characteristics of a common fish ectoparasite Argulus foliaceus, poorly studied in the northern part of its range, were investigated. Field data on the seasonal occurrence, host preference, sex and size of Argulus foliaceus populations from interconnected lakes in Central Finland were analyzed together with experimental data on egg laying, hatching, and mating behaviour. Demographic characteristics of A. foliaceus from a commercial fish farm (high host density) with a water supply from the same lake system differed significantly from those of the lake population where the hosts are scarce. Extended periods of egg laying and hatching were documented in the lake population which possibly prevented the appearance of summer peaks in juveniles that were observed in the farm. The elevated activity of the males, which was most clearly observed in their high attachment/detachment rates, is suggested to result in lower survival and growth than in females. The flexibility, in both behaviour and life cycle strategy, allows A. foliaceus to utilize a broad spectrum of habitats of differing host abundance.
Laakkonen, J. 2000: Microparasites of three species of shrews from Finnish Lapland. — Ann. Zool. Fennici 37: 37–41.
Forty-five common shrews, Sorex araneus, caught in 1997; and 48 S. araneus, 21 masked shrews, Sorex caecutiens, and 25 pygmy shrews Sorex minutus trapped in 1998 at Kilpisjärvi in northern Finland were examined for microparasites. Bartonella sp. was found in blood smears of S. araneus both in 1997 (prevalence 15%) and 1998 (10%) but no blood parasites were found in S. caecutiens or S. minutus. This is the first report of blood parasites of shrews from Finland. A fungal parasite, Pneumocystis carinii, was also observed in S. araneus both in 1997 (prevalence 31%) and in 1998 (58%). In contrast to previous reports, 20% of S. minutus had cyst forms of P. carinii in the lungs but none of the S. caecutiens were infected. Results of this study and related studies from elsewhere indicate that the blood parasite communities of Sorex shrews are less diverse than those found in small rodents. In this study the prevalence of Bartonella was highest in the most abundant host species in the shrew community.
Bukacinski, D. & Bukacinska, M. 2000: The impact of mass outbreaks of black flies (Simuliidae) on the parental behaviour and breeding output of colonial common gulls (Larus canus). — Ann. Zool. Fennici 37: 43–49.
Studies in colonies of common gulls in Poland show that black fly outbreaks can affect breeding success in colonial waterbirds. During massive black fly outbreaks, many pairs of common gulls deserted their nests, both during the incubation period and after hatching. Remaining pairs exhibited less parental care, spent less time at territories and when present, often wheeled above their nests instead of incubating, brooding, or feeding their chicks. Increased absence of adults resulted in increased nest predation by crows and magpies and frequent starvation of broods. Mortality of chicks and adults caused by physical harassment and probably direct loss of blood and body fluids from biting flies was also observed. During black fly outbreak years, loss of clutches and broods increased by 40% to 60%. Low breeding success during outbreak years may limit recruitment of young birds to the colony resulting in long-term population decreases.
Merilä, J., Laurila, A. & Pahkala, M. 2000: Effects of ambient UV-B radiation on early development of the common frog (Rana temporaria) embryos in the subarctic. — Ann. Zool. Fennici 37: 51–58.
Several recent field experiments have demonstrated that ambient ultraviolet-B radiation (UV-B; 280–315 nm) may cause severe mortality of amphibian embryos. We investigated the effects of ambient UV-B on early embryonic performance of the common frog (Rana temporaria) in subarctic Finland (ca. 69°03´N, 20°50´E), where levels of UV-B radiation during the egg laying period are roughly twice as high as those in southern Fennoscandia. We found no evidence for decreased embryonic mortality, decreased frequency of developmental anomalies or improved growth performance of embryos shielded from UV-B as compared with embryos exposed to ambient levels of UV-B. Our results concur with the results of earlier studies with this species conducted in more southern populations, and suggest that current UV-B levels alone are not likely to pose significant threat for the well being of subarctic common frog populations.
Kojola, I. & Laitala, H.-M. 2000: Changes in the structure of an increasing brown bear population with distance from core areas: another example of presaturation female dispersal? — Ann. Zool. Fennici 37: 59–64.
In stable and declining brown bear (Ursus arctos) populations, female dispersal is uncommon and female dispersal distances are short while in increasing populations the distance is not necessarily dependent on sex. The number of brown bears has strongly increased in Finland during recent decades, and the species has recently colonized the central and southern parts of the country. We examined changes in the sex ratio of hunter-killed bears and, from observational data, the proportion of cubs, litter size and proportion of cubs and litter size and proportion of adult males with distance from the Finnish-Russian border. Our results provided evidence that indicated the presence of male-biased dispersal, while no sex difference was noted in dispersal distance, thereby supporting the hypothesis of presaturation female dispersal in an expanding bear population. Small litters in the most peripheral area may result from recent dispersal by females that had not yet attained prime breeding age in the new area.