Roff, D. 2003: Evolutionary quantitative genetics: Are we in danger of throwing out the baby with the bathwater? — Ann. Zool. Fennici 40: 315–320.
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Russell, S. T. 2003: Evolution of intrinsic post-zygotic reproductive isolation in fish. — Ann. Zool. Fennici 40: 321–329.
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Jönsson, K. I. & Järemo, J. 2003: A model on the evolution of cryptobiosis. — Ann. Zool. Fennici 40: 331–340.
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Copp, G. H. & Kovac, V. 2003: Sympatry between threespine Gasterosteus aculeatus and ninespine Pungitius pungitius sticklebacks in English lowland streams. — Ann. Zool. Fennici 40: 341–355.
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Weladji, R. B., Holand, Ø., Yoccoz, N. G. & Lenvik, D. 2003: Maternal age and offspring sex ratio variation in reindeer (Rangifer tarandus). — Ann. Zool. Fennici 40: 357–363.
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Rintala, J., Tiainen, J. & Pakkala, T. 2003: Population trends of the Finnish starling Sturnus vulgaris, 1952–1998, as inferred from annual ringing totals. — Ann. Zool. Fennici 40: 365–385.
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Russell, S. T. 2003: Evolution of intrinsic post-zygotic reproductive isolation in fish. — Ann. Zool. Fennici 40: 321–329.
The comparative approach is important in investigating the evolution of reproductive isolation. Yet this method has not been extended to teleost fish, the most diverse vertebrate lineage. Many experimental interspecific crosses have been performed in aquacultural research, and some of the resultant data is analysed in relation to mitochondrial cytochrome b divergence to investigate the evolution of intrinsic postzygotic isolation. Such isolation was found to increase gradually, suggesting that hybrid unfitness is usually due to the gradual accumulation of deleterious epistatic interactions among species. Hybrid sterility evolved more rapidly than inviability, although both forms of hybrid fitness are probably important in isolating natural populations. Because of general difficulties in characterising fish genetic sex-determination systems, and because of the plethora of systems potentially represented in any given cross, too few crosses are currently available to evaluate the generality of Haldane's rule in fish.
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Jönsson, K. I. & Järemo, J. 2003: A model on the evolution of cryptobiosis. — Ann. Zool. Fennici 40: 331–340. Back to the top
Copp, G. H. & Kovac, V. 2003: Sympatry between threespine Gasterosteus aculeatus and ninespine Pungitius pungitius sticklebacks in English lowland streams. — Ann. Zool. Fennici 40: 341–355. Back to the top
Weladji, R. B., Holand, Ø., Yoccoz, N. G. & Lenvik, D. 2003: Maternal age and offspring sex ratio variation in reindeer (Rangifer tarandus). — Ann. Zool. Fennici 40: 357–363. Back to the top
Rintala, J., Tiainen, J. & Pakkala, T. 2003: Population trends of the Finnish starling Sturnus vulgaris, 1952–1998, as inferred from annual ringing totals. — Ann. Zool. Fennici 40: 365–385.
Cryptobiosis is an ametabolic state of life entered by some lower organisms (among metazoans mainly rotifers, tardigrades and nematodes) in response to adverse environmental conditions. Despite a long recognition of cryptobiotic organisms, the evolutionary origin and life history consequences of this biological phenomenon have remained unexplored. We present one of the first theoretical models on the evolution of cryptobiosis, using a hypothetical population of marine tardigrades that migrates between open sea and the tidal zone as the model framework. Our model analyses the conditions under which investments into anhydrobiotic (cryptobiosis induced by desiccation) functions will evolve, and which factors affect the optimal level of such investments. In particular, we evaluate how the probability of being exposed to adverse conditions (getting stranded) and the consequences for survival of such exposure (getting desiccated) affects the option for cryptobiosis to evolve. The optimal level of investment into anhydrobiotic traits increases with increasing probability of being stranded as well as with increasing negative survival effects of being stranded. However, our analysis shows that the effect on survival of being stranded is a more important parameter than the probability of stranding for the evolution of anhydrobiosis. The existing, although limited, evidence from empirical studies seems to support some of these predictions.
The comparative biology of stream-dwelling threespine Gasterosteus aculeatus L. and ninespine Pungitius pungitius L. sticklebacks was examined in streams of eastern England. Threespine occurred throughout, but ninespine occurred < 50 km from stream source, varying from regular distribution to contagion. The species co-occurred more often than expected in macro and microhabitats, and dietary overlap occurred overall and within Callitriche beds. Threespine occurred infrequently and ninespine frequently in Apium beds, contrasting silt/detritus habitats. Threespine and ninespine microhabitat preferences differed in distance from bank, substratum composition, and amount of ligneous debris, and seems uninfluenced by bullhead Cottus gobio, which used faster flowing areas. Greater use of vegetation by ninespine is facilitated by a more stream-lined and small body, which imposes corporal space constraints on gonad size. To compensate, ninespine maintain a lower proportion of mature eggs, produce smaller batches more frequently than threespine and thus incur a lower annual investment to reproduction.
Different evolutionary hypotheses have been proposed to explain variation in offspring sex ratios among mammalian populations. The Trivers and Willard and local resource competition hypotheses, which are based on adaptive modification by maternal investment, are two opposing hypotheses commonly used for ungulates, but empirical patterns often do not fit either hypotheses' expectations. We investigated sex ratio variation in 1658 reindeer (Rangifer tarandus) calves in relation to their mothers' mass and age, while accounting for potential density-independent factors such as climate. The most parsimonious model included only the effect of maternal age, the proportion of males increasing with increasing maternal age. Similar models in terms of parsimony included (in addition to maternal age) the winter temperature or the North Atlantic Oscillation (NAO) index when the mothers were in utero, indicating that climatic conditions experienced by mothers in their year of birth, have the potential to influence variation in a cohort's offspring sex ratio. Thus, a combination of both density-dependent and density-independent factors may influence sex ratio variation in reindeer and perhaps in other ungulates. We suggest that, if an adaptive maternal strategy is present, it may be induced and/or inhibited by, or interact with other factors such as climate.
Finnish starling populations have declined, a phenomenon first noted towards the end of the 1970s. Here we use national ringing totals to estimate changes in the starling population. However, the numbers ringed depend not only on the population size but also on yearly variations in ringing activities. Thus, it was necessary to correct these totals based on the records of other ringed passerines. In this study, we used a Monte Carlo simulation based on time series regressions for the estimation of confidence of indices. The results suggest that the population size from the early 1970s to the 1990s was significantly smaller than in the 1950s and 1960s. It was concluded that (i) the population was fairly stable in the period 1952–1970, (ii) the population started a consistent decline around 1970, and (iii) the population declined by approximately 90% in the period 1970–1985.