| 1. |
- Chan, B. K. K., et al.
(författare)
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Setal morphology and cirral setation of thoracican barnacle cirri: adaptations and implications for thoracican evolution
- 2008
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Ingår i: Journal of Zoology. - : Wiley. - 0952-8369 .- 1469-7998. ; 275:3, s. 294-306
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Tidskriftsartikel (refereegranskat)abstract
- Thoracic cirripedes are sessile crustaceans that use six pairs of thoracic appendages (the cirri) to catch and handle food. We used scanning electron microscopy to examine the cirri, which include one to three pairs of maxillipeds in six species of thoracican barnacles, in search of correlations between cirral setation and feeding mode. The species studied comprise both pedunculate and sessile forms and represent a wide range of marine habitats as well as morphologies, viz., Ibla cumingi, Octolasmis warwickii, Capitulum mitella, Pollicipes polymerus, Tetraclita japonica japonica and Megabalanus volcano. Of the pedunculates, I. cumingi has the least complex setation pattern consisting of only serrulate types. This is consistent with its very simplified feeding mode and an apparent inability to discriminate between food items. Octolasmis warwickii is slightly more modified, while both P. polymerus and C. mitella have a more diversified setation. The balanomorphan species exhibit by far the most complex cirral setation. This is consistent with the several types of suspension feeding seen in these species, their ability to identify and sort captured food items and even to perform microfiltration in the mantle cavity using the setae on their three pairs of maxillipeds. Our results indicate that in thoracican barnacles, adaptations in feeding behaviour are associated with changes in the setation pattern of the cirri. In addition, the setal types and their distribution on the cirri are potential new characters in future morphology-based analyses of the phylogeny of the Cirripedia Thoracica.
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| 2. |
- Loman, Jon
(författare)
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Primary and secondary phenology. Does it pay a frog to breed early?
- 2009
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Ingår i: Journal of Zoology. - : Wiley. - 0952-8369 .- 1469-7998. ; 279:1, s. 64-70
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Tidskriftsartikel (refereegranskat)abstract
- This study examines the consequences of variation in the laying and hatching date for the time of metamorphosis in the common frog Rana temporaria. Field data are presented showing that eggs laid early tend to take longer to develop. Thus, the time advantage for early eggs is reduced at the time of hatching. There was an among-year variation in this phenomenon; it was not manifest in a phenologically late year. Also, field data revealed that mortality due to pond freezing is a real risk for early laid eggs. Finally, two experiments in tanks analyse the effects of hatching date variation for the time of metamorphosis. (1) When hatching was experimentally delayed by 7 or 11 days, this resulted in later metamorphosis, however, by only 2 and 5 days, respectively. (2a) When tadpoles from the same pond that naturally hatched at different times were compared, it was found that a hatching time difference of 6 days resulted in later metamorphosis by 2 days only. (2b) A comparison of tadpoles from two different ponds that hatched 11 days apart also resulted in only 2 days’ difference in metamorphosis. In this case, the later but faster developing tadpoles metamorphosed at a smaller size. I suggest that eggs from these two ponds differed genetically in the growth and development strategy. Despite the obvious risks, and the moderate gain in terms of early metamorphosis, frogs breed dangerously early in spring. Possible reasons for this are discussed. These include external selective forces that promote early metamorphosis (also at a high cost), within-pond competition among tadpoles with an advantage for early and large tadpoles and finally factors relating to mate choice at the breeding site.
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| 3. |
- Nilsson, Jan-Åke, et al.
(författare)
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Causes and consequences of egg mass variation between and within blue tit clutches
- 1993
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Ingår i: Journal of Zoology. - : Wiley. - 1469-7998 .- 0952-8369. ; 230:3, s. 469-481
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Tidskriftsartikel (refereegranskat)abstract
- Causes of egg‐size variation between and within clutches were studied in clutches of the blue tit (Parus caeruleus L.). We measured the mass of each egg in the laying sequence in unmanipulated clutches, in clutches of parents experimentally supplied with extra food before egg‐laying, and in clutches of parents supplemented with extra food after the start of egg‐laying. Hatchlings were weighed at an age of two days and their mass was found to be positively related to egg mass. No general trend of decreasing or increasing egg mass was found within the laying sequence. Females provided with extra food before egg‐laying laid clutches with significantly less variation in egg mass than did control females. The reason for this was that the first‐laid egg of unmanipulated females was lighter than the rest of the eggs in the clutch. This pattern disappeared in clutches of females receiving extra food. Thus, the reduction in egg mass variation among clutches of foodsupplemented females depended on an ability of these females, in contrast to control females, to lay a first egg of the same mass as the rest of the clutch. Eggs laid after the initiation of incubation were significantly heavier than equivalent eggs in those clutches where incubation started after clutch completion. The difference was small, however, and the adaptive significance of the finding is questionable. We argue that intra‐clutch variation in egg mass is connected with greater fitness consequences than in inter‐clutch variation. Furthermore, our results indicate that energetical constraints on the laying female are more important as a cause of the observed intra‐clutch variation in egg mass than are adaptive responses to the environment.
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| 4. |
- Weber, Thomas, et al.
(författare)
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Flight feather shaft structure of two warbler species with different moult schedules: a study using high-resolution X-ray imaging
- 2010
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Ingår i: Journal of Zoology. - : Wiley. - 0952-8369 .- 1469-7998. ; 280:2, s. 163-170
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Tidskriftsartikel (refereegranskat)abstract
- Plumage constitutes a significant component of the somatic investment of birds. A detailed investigation of feathers and moult can help to uncover trade-offs involved in somatic investment decisions, the sources of some of the costs birds have to pay and the potential fitness consequences. We used micro-computed tomography imaging to study the second moment of area, a structural parameter that is one determinant of bending stiffness and the cortex volume of flight feather shafts of two sister taxa, the willow warbler Phylloscopus trochilus, a migratory species with two annual moults, and the chiffchaff Phylloscopus collybita, a migrant with one annual post-nuptial moult. Juvenile and adult willow warbler and chiffchaff feathers, all grown on the breeding grounds, are structurally very similar to each other. Willow warbler feathers grown during moult on the wintering grounds, however, have a significantly higher second moment of area and a significantly larger cortex volume than all the other feather types. We discuss the possibility that the seasonal variability of willow warbler feathers may be an adaptive structural reflection of a moult-migration strategy that has allowed this species to occupy large breeding and wintering ranges.
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| 5. |
- Wojcik, J. M., et al.
(författare)
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Post-bottleneck mtDNA diversity in a free-living population of European bison: implications for conservation
- 2009
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Ingår i: Journal of Zoology. - : Wiley. - 0952-8369 .- 1469-7998. ; 277:1, s. 81-87
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Tidskriftsartikel (refereegranskat)abstract
- A free-living population of European bison Bison bonasus in the Bialowieza Primeval Forest originated from only seven founder animals after a severe bottleneck that occurred at the beginning of the 20th century. Consequently, the contemporary population of the species is characterized by low genetic diversity. We studied a total of 195 individuals (127 males and 68 females). A 1429 bp fragment of mitochondrial DNA (mtDNA) including the D-loop region was analyzed in 87 individuals and revealed only three distinct haplotypes. Nucleotide (pi) and haplotype (H-d) diversity values were estimated for the European bison and were compared with pi and H-d estimated from three individuals of American bison Bison bison. Very low diversity values were found in the European bison in comparison with the diversity values found in the American bison. The low mtDNA variability in the European bison is in concordance with theoretical expectations for a species that has undergone a severe and recent bottleneck. A management strategy for the preservation of the rare and very rare haplotypes present in the Bialowieza population of the European bison is discussed. Furthermore, all 195 individuals were investigated for heteroplasmy involving these three haplotypes, in order to detect a possible association between heteroplasmy and the incidence of males affected by posthitis, a disease that affects the male reproductive organs, leading to necrotic lesions. Heteroplasmy was found in 15 females, in 17 males affected by posthitis and in 11 non-affected males, and no significant association was found.
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| 6. |
- Brochet, Anne-Laure, et al.
(författare)
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Is diet segregation between dabbling ducks due to food partitioning? : a review of seasonal patterns in the Western Palearctic
- 2012
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Ingår i: Journal of Zoology. - 0952-8369 .- 1469-7998. ; 286:3, s. 171-178
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Tidskriftsartikel (refereegranskat)abstract
- Within the paradigm of resource-limited competition-structured communities, dabbling ducks (Anas spp.) have been used as a textbook example of how morphological differences, notably bill lamellar density and body length, may allow sympatric species to partition food and hence coexist. We reviewed all accessible diet studies from the Western Palearctic for three closely related dabbling duck species, mallard (Anas platyrhynchos), pintail (A.?acuta) and teal (A.?crecca), and present a comprehensive list of the food items (invertebrates, seeds, vegetative parts of plants) ingested. To assess the circumannual perspective of niche separation, we evaluated size distribution of ingested seeds among seasons and duck species. There was a significant difference among duck species in mean size and mass of ingested seeds, as well as in diet composition, with the largest seeds consumed by the largest species (mallard) with the coarsest bill filter apparatus (lamellae), and the smallest seeds by the smallest species (teal) with the finest bill lamellae. However, no effect of season was found, suggesting consistent diet segregation among species throughout the annual cycle of ducks and over large geographical areas. We argue that the patterns of food size separation between the three species are compatible with the idea of coexistence under interspecific competition.
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| 7. |
- Brochet, Anne-Laure, et al.
(författare)
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Is diet segregation between dabbling ducks due to food partitioning? : a review of seasonal patterns in the Western Palearctic
- 2012
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Ingår i: Journal of Zoology. - : Wiley-Blackwell. - 0952-8369 .- 1469-7998. ; 286:3, s. 171-178
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Tidskriftsartikel (refereegranskat)abstract
- Within the paradigm of resource-limited competition-structured communities, dabbling ducks (Anas spp.) have been used as a textbook example of how morphological differences, notably bill lamellar density and body length, may allow sympatric species to partition food and hence coexist. We reviewed all accessible diet studies from the Western Palearctic for three closely related dabbling duck species, mallard (Anas platyrhynchos), pintail (A.?acuta) and teal (A.?crecca), and present a comprehensive list of the food items (invertebrates, seeds, vegetative parts of plants) ingested. To assess the circumannual perspective of niche separation, we evaluated size distribution of ingested seeds among seasons and duck species. There was a significant difference among duck species in mean size and mass of ingested seeds, as well as in diet composition, with the largest seeds consumed by the largest species (mallard) with the coarsest bill filter apparatus (lamellae), and the smallest seeds by the smallest species (teal)with the finest bill lamellae. However, no effect of season was found, suggesting consistent diet segregation among species throughout the annual cycle of ducks and over large geographical areas. We argue that the patterns of food size separation between the three species are compatible with the idea of coexistence under interspecific competition.
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| 8. |
- Faurby, Sören, et al.
(författare)
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Variation in anhydrobiotic survival of two eutardigrade morphospecies : a story of cryptic species and their dispersal
- 2008
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Ingår i: Journal of Zoology. - 0952-8369 .- 1469-7998. ; 275:2, s. 139-145
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Tidskriftsartikel (refereegranskat)abstract
- Studies of geographic variation in anhydrobiotic tolerance may increase our understanding of the population dynamics of terrestrial meiofauna and the relative importance of local adaptation and microhabitat niche separation. Although anhydrobiosis in tardigrades has been studied extensively, few studies have dealt with intraspecific variation in survival and none of these included genetic data to validate the intraspecific nature of the comparisons. Such data are necessary when working with meiofauna as cryptic species are common. We analysed the anhydrobiotic survival and genetic variation in cytochrome oxidase subunit I of two eutardigrades (Richtersius coronifer and Ramazzottius oberhaeuseri) from Italy and Sweden to detect possible local adaptation. Survival was analysed as a multidimensional contingency table and showed that anhydrobiotic survival was higher in Sweden for Ra. oberhaeuseri whereas no significant geographic variation was found for Ri. coronifer. Our genetic analysis indicated the coexistence of two cryptic species of Ra. oberhaeuseri in Italy, only one of which was found in Sweden. It could not be determined whether the variation in Ramazzottius is intra- or interspecific due to the presence of these cryptic species. We suggest that geographic variation in anhydrobiotic survival may be a general phenomenon in tardigrades but further research is necessary to determine the degree of intraspecific variation. The genetic analysis showed indications of long-term isolation of the individual populations of Ri. coronifer but recent dispersal in one of the cryptic species of Ramazzottius. We found higher survival in Ra. oberhaeuseri than in Ri. coronifer. These results indicate a possible coupling between anhydrobiotic survival and dispersal rate.
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| 9. |
- Faurby, Sören, et al.
(författare)
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Variation in anhydrobiotic survival of two eutardigrade morphospecies : a story of cryptic species and their dispersal
- 2008
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Ingår i: Journal of Zoology. - : Wiley-Blackwell. - 0952-8369 .- 1469-7998. ; 275:2, s. 139-145
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Tidskriftsartikel (refereegranskat)abstract
- Studies of geographic variation in anhydrobiotic tolerance may increase our understanding of the population dynamics of terrestrial meiofauna and the relative importance of local adaptation and microhabitat niche separation. Although anhydrobiosis in tardigrades has been studied extensively, few studies have dealt with intraspecific variation in survival and none of these included genetic data to validate the intraspecific nature of the comparisons. Such data are necessary when working with meiofauna as cryptic species are common. We analysed the anhydrobiotic survival and genetic variation in cytochrome oxidase subunit I of two eutardigrades (Richtersius coronifer and Ramazzottius oberhaeuseri) from Italy and Sweden to detect possible local adaptation. Survival was analysed as a multidimensional contingency table and showed that anhydrobiotic survival was higher in Sweden for Ra. oberhaeuseri whereas no significant geographic variation was found for Ri. coronifer. Our genetic analysis indicated the coexistence of two cryptic species of Ra. oberhaeuseri in Italy, only one of which was found in Sweden. It could not be determined whether the variation in Ramazzottius is intra- or interspecific due to the presence of these cryptic species. We suggest that geographic variation in anhydrobiotic survival may be a general phenomenon in tardigrades but further research is necessary to determine the degree of intraspecific variation. The genetic analysis showed indications of long-term isolation of the individual populations of Ri. coronifer but recent dispersal in one of the cryptic species of Ramazzottius. We found higher survival in Ra. oberhaeuseri than in Ri. coronifer. These results indicate a possible coupling between anhydrobiotic survival and dispersal rate.
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| 10. |
- Angerbjörn, Anders
(författare)
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Reproduction of Mountain Hares (Lepus-Timidus) in Relation to Density and Physical Condition
- 1986
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Ingår i: Journal of Zoology. - : Wiley. - 0952-8369 .- 1469-7998. ; 208:4, s. 559-568
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Tidskriftsartikel (refereegranskat)abstract
- Population estimates of Mountain hares were done on three islands off the west coast of Sweden. Three different relative measures of hare reproduction were negatively related to density. Most of this relationship was accounted for through a positive correlation with body condition. However, there was no significant density trend in litter size or number of litters. The start of the reproductive season each year was related to mean air temperature during spring, so when spring was early so was conception.
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