| 1. |
- Bensch, Staffan, et al.
(författare)
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Temporal dynamics and diversity of avian malaria parasites in a single host species
- 2007
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Ingår i: Journal of Animal Ecology. - : Wiley. - 1365-2656 .- 0021-8790. ; 76:1, s. 112-122
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Tidskriftsartikel (refereegranskat)abstract
- We have used molecular methods to unravel a remarkable diversity of parasite lineages in a long-term population study of great reed warblers Acrocephalus arundinaceus that was not foreseen from traditional microscopic examination of blood smears. This diversity includes eight Haemoproteus and 10 Plasmodium lineages of which most probably represent good biological species.Contrary to expectation, the relative frequency of parasite lineages seemed not to change over the 17-year study period and we found no effects of the parasites on a male secondary sexual ornament (song repertoire size) and two measures of fitness (adult survival and production of recruited offspring).We discuss whether the absence of fitness consequences of the parasites might relate to the fact that we have studied the host at the breeding sites in Europe, whereas the transmission seems to take place at the wintering sites in Africa, where the naive birds encounter the parasites for the first time and the resulting primary infections likely make them sicker than during the chronic phase of the infection.The prevalence of the three most common lineages appeared to fluctuate in parallel with a periodicity of approximately 3-4 years. Theoretical models based on intrinsic interactions between parasite antigen and host immune genes cannot explain such dynamics, suggesting that knowledge of extrinsic parameters such as vector distribution and alternative hosts are required to understand these patterns.
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| 2. |
- Saether, BE, et al.
(författare)
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Time to extinction in relation to mating system and type of density regulation in populations with two sexes
- 2004
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Ingår i: Journal of Animal Ecology. - : Wiley. - 1365-2656 .- 0021-8790. ; 73:5, s. 925-934
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Tidskriftsartikel (refereegranskat)abstract
- 1. Population viability models usually consider only the female segment of the population. However, random variation in sex ratio as well as the mating system may also affect variation in fitness among females. Here we develop population models incorporating demographic stochasticity in both sexes. Furthermore, we consider the effects on the estimated time to extinction and whether density regulation acts only on females or on total population size. 2. We applied these models to two populations of polygynous great reed warblers Acrocephalus arundinaceus L. with differences in population trends to investigate the importance of considering sex in population viability models. 3. Demographic stochasticity was larger in a polygynous than in a monogamous mating system. 4. The estimated time to extinction was considerably shorter for a monogamous than for a polygynous mating system, particularly if density regulation acted only on females than rather on the total population. 5. This study demonstrates that structure of mating system must be included when making population viability analysis based on counts of total population sizes. It is especially important to model the specific effects of density regulation on the two sexes.
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| 3. |
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| 4. |
- Bensch, Staffan
(författare)
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Female mating status and reproductive success in the great reed warbler: Is there a potential cost of polygyny that requires compensation?
- 1996
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Ingår i: Journal of Animal Ecology. - 1365-2656. ; 65:3, s. 283-296
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Tidskriftsartikel (refereegranskat)abstract
- 1. Using data from a 9-year study of the great reed warbler Acrocephalus arundinaceus L. carried out in Sweden, I tested the main assumption of the polygyny threshold model (that there is a cost of polygyny) and the main prediction (that this cost is compensated for). The main question was whether a female that chose a mated male (secondary females) experienced the same fitness as a female that at the same time chose an unmated male (primary females). The study includes a total of 192 breeding seasons of 104 individual females of which 40% settled with already mated males. 2. Eight potential correlates of fitness were examined; namely, clutch size, hatching success, hedging success, survival until breeding age, nest survival, mass of fledglings, mass of feeding females and annual survival rate of breeding females. I started each analysis by controlling for four potential confounding variables (year, study site, female age and breeding date). Then I compared the average fitness measure of primary and secondary females. 3. The only detected potential component cost of polygyny was a higher mortality among nestlings if a non-primary position within the harem was retained until hatching. This was supported by a natural experiment. Females that initially chose mated males but which achieved a primary position after failure of the originally primary female's nest enjoyed an increased fledging success, probably because of more male assistance. 4. The number of recruits, controlling for settling dates, for the two categories of females were almost identical (primary females 0 . 53 recruits per year, secondary females 0 . 51 recruits per year). Since secondary and primary females showed similar rates of survival until next breeding season the fitness of the two strategies appears to be equal. These findings strongly suggest that polygyny in the great reed warbler is best explained by the compensation models such as the polygyny threshold model.
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| 5. |
- Ferraguti, Martina, et al.
(författare)
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Ecological determinants of avian malaria infections : An integrative analysis at landscape, mosquito and vertebrate community levels
- 2018
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Ingår i: Journal of Animal Ecology. - : Wiley. - 0021-8790. ; 87:3, s. 727-740
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Tidskriftsartikel (refereegranskat)abstract
- Vector and host communities, as well as habitat characteristics, may have important but different impacts on the prevalence, richness and evenness of vector-borne parasites. We investigated the relative importance of (1) the mosquito community composition, (2) the vertebrate community composition and (3) landscape characteristics on the prevalence, richness and evenness of avian Plasmodium. We hypothesized that parasite prevalence will be more affected by vector-related parameters, while host parameters should be also important to explain Plasmodium richness and evenness. We sampled 2,588 wild house sparrows (Passer domesticus) and 340,829 mosquitoes, and we performed vertebrate censuses at 45 localities in the Southwest of Spain. These localities included urban, rural and natural landscapes that were characterized by several habitat variables. Twelve Plasmodium lineages were identified in house sparrows corresponding to three major clades. Variation partitioning showed that landscape characteristics explained the highest fraction of variation in all response variables (21.0%-44.8%). Plasmodium prevalence was in addition explained by vector-related variables (5.4%) and its interaction with landscape (10.2%). Parasite richness and evenness were mostly explained by vertebrate community-related variables. The structuring role of landscape characteristics in vector and host communities was a key factor in determining parasite prevalence, richness and evenness, although the role of each factor differed according to the parasite parameters studied. These results show that the biotic and abiotic contexts are important to explain the transmission dynamics of mosquito-borne pathogens in the wild.
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