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| 2. |
- Forsman, Anders, et al.
(författare)
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Trade-off between growth and energy storage in male Vipera berus (L.) under different prey densities
- 1991
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Ingår i: Functional Ecology. ; 5, s. 717-723
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Tidskriftsartikel (refereegranskat)abstract
- There are constraints on the rate of energy intake of foraging animals, and allocation of energy, for example, to growth therefore must be at the expense of allocation to other purposes, such as energy storage. Moreover, the relative amount of energy allocated to different kinds of activities is likely to depend upon food availability. We have compared the patterns of energy allocation between adders, Vipera berus (L.), in populations inhabiting two different island groups in the Baltic Sea. These adders primarily feed on field voles, Microtus agrestis (L.), which undergo great population density fluctuations. In order to survive periods of low food supply adders allocate some energy to storage, and they can be expected to increase the proportion of energy devoted to storage when food levels and rate of energy intake decrease. Individuals allocating much energy to storage have less energy available for growth, reproduction and maintenance, and one can expect a trade-off between growth and energy storage, especially during resource shortage. Since the size of energy reserves influences fasting endurance, while body size influences future reproductive success, the pattern of energy allo- cation between growth and storage might have important fitness consequences for these animals. We compared the size of energy reserves (body mass in relation to body length) and the growth rates of individual male adders from two localities with different densities of field voles. Relative body mass was similar to both adder populations, but individuals grew faster where vole density was higher. This suggests that the pattern of energy allocation changed with resource availability. We also investigated the relationships between rela- tive growth rate and relative mass within the two adder populations. We found a significant nega- tive relationship where prey density was low, and a negative but non-significant relationship where prey density was high, indicating a trade-off between growth and energy storage in male adders that changes with food availability.
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| 3. |
- Forsman, Anders
(författare)
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Variation in sexual size dimorphism and maximum body size among adder populations: effects of prey size
- 1991
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Ingår i: Journal of Animal Ecology. - : JSTOR. - 0021-8790 .- 1365-2656. ; 60:1, s. 253-267
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Tidskriftsartikel (refereegranskat)abstract
- (1) Geographic variation in maximum body size of male and female adders, Vipera berus, was documented over one mainland locality and six groups of islands in the Baltic Sea. Males varied more in body size among localities than females, although not significantly so. (2) Geographic variation in prey (field vole, Microtus agrestis) body size explained 68% and 40% of the variation in maximum body size of male and female adders, respectively. Body size of adders increased with body size of prey. (3) Adders were smaller on islands where there were three prey species than where there were two. It is suggested that selection for fasting endurance where there are few prey species and a high risk of starvation may have produced this pattern. (4) Growth rates of individual adders were faster where mean field vole body weight was large (47 g) than where it was small (26 g). Maximum body size of adders was large where growth rate was fast and vice versa. (5) Female adders were larger than males at all localities. Females also had faster growth rates than males. (6) The degree of sexual size dimorphism of adders varied among localities and was negatively correlated with size of males. There was no relationship between sexual dimorphism and size of females. (7) There was no significant relationship between sexual size dimorphism of adders and mean body size of field voles. Nor was there any relationship between sexual dimorphism and number of prey species or size distribution of field voles. (8) I argue that optimal body size for survival is locally determined by prey availability and size of prey items. However, due to the fecundity advantage of large size in females, female adders deviate from the optimum size for survival, and more so when this optimum size is small. Thus, local variation in properties of the food resource, e.g. prey size, can give rise to variation in sexual size dimorphism.
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| 5. |
- Sundberg, P, et al.
(författare)
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Homoplasy, character function and nemertean systematics
- 1994
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Ingår i: Journal of Zoology. - : Wiley. - 0952-8369 .- 1469-7998. ; 234:2, s. 253-263
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Tidskriftsartikel (refereegranskat)abstract
- We question recent claims that cladistic analysis is inapplicable in nemerteans (phylum Nemertea) due to a supposedly high degree of convergence. We further argue that terms like convergence and parallelism are historical sayings and only make sense in a phylogenetic context. Therefore, an approach aiming to produce phylogenetic hypotheses cannot be rejected on the grounds of a high degree of convergence before the actual hypothesis. Convergence is not an empirical observation, but a conclusion made after an analysis. We also discuss the view that knowledge of a character's function is a prerequisite for phylogenetic analysis and conclude that this is an invalid approach. Function, like any other way of sharpening our observations, helps in formulating non-phylogenetic hypotheses of homology, but the crucial test is congruence with other characters on a phylogeny.
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| 6. |
- Löfstedt, Christer, et al.
(författare)
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Behavioural and electrophysiological activity of unsaturated analogues of the pheromone tetradecyl acetate in the small ermine moth Yponomeuta rorellus
- 1990
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Ingår i: Physiological Entomology. - : Wiley. - 0307-6962 .- 1365-3032. ; 15:1, s. 47-54
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Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT In field‐trapping experiments the unsaturated analogues (E)‐6‐, (E)‐12‐, and (Z)‐12‐tetradecenyl acetate were as attractive to male Yponomeuta rorellus Latr. as the native pheromone component tetradecyl acetate. All four analogues attracted more males than virgin females did, whereas (Z)‐6‐, (E)‐11‐, (Z)‐10‐ and (Z)‐11‐tetradecenyl acetate were essentially non‐attractive. Addition of 1–30% of (Z)‐11‐tetradecenyl acetate to the pheromone tetradecyl acetate reduced the attraction to less than 2%. Flight tunnel experiments with Y. rorellus confirmed the activity of the (E)‐6‐ and (E)‐12‐tetradecenyl acetates and demonstrated the activity of (E)‐7‐tetradecenyl acetate as well. These analogues elicited orientation behaviour, upwind flight and landing at the odour source as frequently as the native pheromone did. Single sensillum recordings from male Y. rorellus showed two types of cells in most sensilla. A large spike amplitude cell was stimulated by tetradecyl acetate and the unsaturated analogues (E)‐11‐, (E)‐6‐ and (E)‐12‐tetradecenyl acetate, and to a lower extent by the (Z)‐6‐, (Z)‐11‐ and (Z)‐12‐isomers. A cell with medium spike amplitude was stimulated by (Z)‐9‐tetradecenyl and (Z)‐11‐hexadecenyl acetate. Some sensilla contained a third cell firing with a small spike amplitude which was activated by (Z)‐11‐tetradecenol. Thus the tetradecyl acetate receptor was stimulated not only by the behaviourally active analogues, but also by behavioural antagonists. The interaction of (E)‐11‐tetra‐decenyl acetate and tetradecyl acetate with the same antennal receptor cell was also demonstrated in Y.cagnagellus. Electrophysiological discrimination between behavioural attractants and antagonists and the role of behavioural antagonists in the interspecific relations between Y.rorellus and sympatric closely related species are discussed.
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| 7. |
- Löfstedt, Christer
(författare)
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Moth pheromone genetics and evolution
- 1993
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Ingår i: Philosophical Transactions of the Royal Society B: Biological Sciences. - : The Royal Society. - 1471-2970. ; 340:1292, s. 167-177
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Tidskriftsartikel (refereegranskat)abstract
- Argues that there is no reason to dismiss species recognition as a possible cause of evolutionary change in moth sex pheromones. Selection for species recognition cannot explain all of the diversity in sex pheromones and the data supporting this contention are weak, but the alternative causes suggested, invoking mate choice between conspecifics as the mechanism of sexual selection, has no empirical support. Finding and analysing genes responsible for mate choice is important to corroborate any theory of sexual selection and speciation, and genetic dissection of moth pheromone communication has provided important progress. Mendelian genes controlling differences in mate choice and in the production of mate recognition signals have been found. -from Author
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| 8. |
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| 9. |
- Tóth, Miklos, et al.
(författare)
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Attraction of male turnip moths Agrotis segetum (Lepidoptera : Noctuidae) to sex pheromone components and their mixtures at 11 sites in Europe, Asia, and Africa
- 1992
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Ingår i: Journal of Chemical Ecology. - 0098-0331. ; 18:8, s. 1337-1347
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Tidskriftsartikel (refereegranskat)abstract
- Selected combinations of (Z)-5-decenyl, (Z)-7-dodecenyl, and (Z)-9-tetradecenyl acetates, the pheromone components of the turnip moth AgrotisSegetum were tested for field attractancy at six, two, and three sites in Europe, Asia, and Africa, respectively. At all of the sites in Eurasia and in northern Africa the ternary mixture of the acetates captured most males, while at the sites south of the Sahara in Africa, (Z)-5-decenyl acetate alone was responsible for attraction. Differences in male attraction among the populations studied confirm the existence of significant population variation in the pheromone of A. segetum. Interpretation of the present results together with earlier studies suggests that this variation is more or less continuous in Eurasia and north Africa, while a clearly distinct pheromone type is present in the areas south of the Sahara desert.
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| 10. |
- Svensson, Mikael
(författare)
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Morphological variation in the palaeonemertean Tubulanus annulatus (Montagu, 1804)
- 1993
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Ingår i: Hydrobiologia. - 0018-8158 .- 1573-5117. ; 266, s. 239-246
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Tidskriftsartikel (refereegranskat)abstract
- Previous studies on the palaeonemertean Tubulanus annulatus have hinted on possible geographic variation, or even a species complex. This study describes the variation in morphology, focusing on the characters that have been supposed to vary geographically. Specimens from the Swedish west coast (Tjärnö and Kristineberg), Scottish west coast (Millport), and the Mediterranean (Naples and Split) were included in the study. It is concluded that the pattern of variation in the studied characters do not correspond to geography and most of the character states previously thought to vary geographically are in fact found within one and the same population.
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