| 1. |
- Pertoldi, Cino, et al.
(författare)
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Scaling of the mean and variance of population dynamics under fluctuating regimes
- 2014
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Ingår i: Theory in Biosciences. - : Springer Science and Business Media LLC. - 1431-7613 .- 1611-7530. ; 133:3-4, s. 165-173
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Tidskriftsartikel (refereegranskat)abstract
- Theoretical ecologists have long sought to understand how the persistence of populations depends on the interactions between exogenous (biotic and abiotic) and endogenous (e.g., demographic and genetic) drivers of population dynamics. Recent work focuses on the autocorrelation structure of environmental perturbations and its effects on the persistence of populations. Accurate estimation of extinction times and especially determination of the mechanisms affecting extinction times is important for biodiversity conservation. Here we examine the interaction between environmental fluctuations and the scaling effect of the mean population size with its variance. We investigate how interactions between environmental and demographic stochasticity can affect the mean time to extinction, change optimal patch size dynamics, and how it can alter the often-assumed linear relationship between the census size and the effective population size. The importance of the correlation between environmental and demographic variation depends on the relative importance of the two types of variation. We found the correlation to be important when the two types of variation were approximately equal; however, the importance of the correlation diminishes as one source of variation dominates. The implications of these findings are discussed from a conservation and eco-evolutionary point of view.
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| 2. |
- Bach, Lars, et al.
(författare)
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Kin competition and the evolution of dispersal in an individual-based model
- 2006
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Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800. ; 192:3-4, s. 658-666
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Tidskriftsartikel (refereegranskat)abstract
- The evolution of dispersal was investigated in an adaptive individual-based metapopulation model, which allowed for demographic and environmental stochasticity. The individual dispersal behaviour was determined by a one-locus genotype subjected to simple inheritance and mutation. Dispersal behaviour could therefore evolve through the genotype–phenotype mapping and the selection regimes stemming from various ecological scenarios. Due to the individual-based design kin competition emerges per default rather than being approximated through an expected average level of relatedness. By decoupling reproduction and competition in the discrete life cycle dispersal was allowed to occur either before or after local competition. Hence, the degree to which dispersal relaxed competition among siblings was investigated directly with respect to the effect on the evolved dispersal rate. We found a pronounced difference in the evolved level of dispersal for certain combinations of local extinction and dispersal cost. However, when either of these two evolutionary forces (local fluctuation in fitness or dispersal cost) predominates, the effect of kin selection seems to be overshadowed. The island and the stepping stone structures gave somewhat similar patterns of adaptive response suggesting some robustness to spatial effects, although, as expected, the effect was less pronounced with nearest neighbour dispersal in the stepping stone model. The results demonstrate under different stochastic and spatial scenarios how the evolution of dispersal alleviates kin competition when it originates from the population renewal process as an emergent property. Moreover, predictions are suggested that may be addressed by selection experiments.
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| 3. |
- Kristensen, T N, et al.
(författare)
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The increase of fluctuating asymmetry in a monoclonal strain of collembolans after chemical exposure - discussing a new method for estimating the environmental variance
- 2004
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Ingår i: Ecological Indicators. - : Elsevier BV. - 1872-7034 .- 1470-160X. ; 4:1, s. 73-81
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Tidskriftsartikel (refereegranskat)abstract
- The increasing demand for detecting and quantifying the negative effects on natural habitats caused by anthropogenic activity has led to the development of impact assessment tools. Here, we propose a monitoring method based on the concept of developmental instability (DI) estimated from fluctuating asymmetry (FA) in bilateral morphological traits in a monoclonal strain. The use of monoclonal populations conveys certain advantages over sexual populations when interpreting fluctuating asymmetry results. This is because the inherent problems of genetic heterogeneity are circumvented. Our investigation demonstrates in practice, how an estimate of the environmental component of the phenotypic variance in a population can be achieved. This estimate can be used to eliminate samples where the presence of macro environmental variance has influenced the estimated level of fluctuating asymmetry significantly. Avoiding the confounding effect due to the presence of genetic variance and controlling the environmental variance component enable a more accurate estimate of the possible detrimental effects of the putative stressing agents. We used a clonal strain of the springtail Folsomia candida exposed to three different contaminants; tributyltin, nonylphenol and bis(2-ethylhexyl)-phthalate (DEPH), in order to test the general applicability of the proposed method. The results show that the method is efficient in discriminating between environments exposed to chemical stress and control environments. However, establishing an actual dose-response relationship was only possible for one of the contaminants, nonylphenol.
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| 4. |
- Pertoldi, C, et al.
(författare)
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The consequences of the variance-mean rescaling effect on effective population size
- 2007
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 116:5, s. 769-774
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Tidskriftsartikel (refereegranskat)abstract
- The effective population size (N-e), and the ratio between N-e and census population size (N) are often used as measures of population viability. We show that using the harmonic mean of population sizes over time - a common proxy for N-e- has some important evolutionary consequences and implications for conservation management. This stems from the fact that there is no unambiguous relationship between the arithmetic and harmonic means for populations fluctuating in size. As long as the variance of population size increases moderately with increasing arithmetic mean population size, the harmonic mean also increases. However, if the variance of population size increases more rapidly, which existing data often suggest, then the harmonic mean may actually decrease with increasing arithmetic mean. Thus maximizing N may not maximize N-e,N- but could instead lower the adaptive potential and hence limit the evolutionary response to environmental change. Large census size has the clear advantage of lowering demographic stochasticity, and hence extinction risk, and under certain conditions large census size also minimizes the loss of genetic variation. Consequently, maximising census size has served as a useful dogma in ecology, genetics and conservation. Nonetheless, due to the intricate relationships among N-e, population viability and the properties of population fluctuations, we suggest that this dogma should be taken only as a rule of thumb.
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| 5. |
- Schou, M. F., et al.
(författare)
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Metabolic and functional characterization of effects of developmental temperature in Drosophila melanogaster
- 2017
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Ingår i: American Journal of Physiology-Regulatory Integrative and Comparative Physiology. - : American Physiological Society. - 0363-6119 .- 1522-1490. ; 312:2
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Tidskriftsartikel (refereegranskat)abstract
- The ability of ectotherms to respond to changes in their thermal environment through plastic mechanisms is central to their adaptive capability. However, we still lack knowledge on the physiological and functional responses by which ectotherms acclimate to temperatures during development, and in particular, how physiological stress at extreme temperatures may counteract beneficial acclimation responses at benign temperatures. We exposed Drosophila melanogaster to 10 developmental temperatures covering their entire permissible temperature range. We obtained metabolic profiles and reaction norms for several functional traits: egg-to-adult viability, developmental time, and heat and cold tolerance. Females were more heat tolerant than males, whereas no sexual dimorphism was found in cold tolerance. A group of metabolites, mainly free amino acids, had linear reaction norms. Several energy-carrying molecules, as well as some sugars, showed distinct inverted U-shaped norms of reaction across the thermal range, resulting in a positive correlation between metabolite intensities and egg-to-adult viability. At extreme temperatures, low levels of these metabolites were interpreted as a response characteristic of costs of homeostatic perturbations. Our results provide novel insights into a range of metabolites reported to be central for the acclimation response and suggest several new candidate metabolites. Low and high temperatures result in different adaptive physiological responses, but they also have commonalities likely to be a result of the failure to compensate for the physiological stress. We suggest that the regulation of metabolites that are tightly connected to the performance curve is important for the ability of ectotherms to cope with variation in temperature.
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| 6. |
- Thirstrup, J. P., et al.
(författare)
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Population viability analysis on domestic horse breeds (Equus caballus)
- 2009
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Ingår i: Journal of Animal Science. - : Oxford University Press (OUP). - 1525-3163 .- 0021-8812. ; 87:11, s. 3525-3535
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we performed a population viability analysis on 3 domestic horse breeds (Equus caballus) of Danish origin, namely, the Frederiksborg, the Knabstrupper, and the Jutland breeds. Because of their small population sizes, these breeds are considered endangered. The Vortex software simulation package was used for the population viability analysis. First, we investigated the future viability of these breeds based on present demographic and environmental parameters. Second, a sensitivity analysis revealed the most important variables for the viability of these breeds. Third, we examined management scenarios in which one of the studbooks was closed. According to the Vortex analysis, 2 of the breeds (Knabstrupper and Jutland) will persist for the next 200 yr, whereas the smaller breed (Frederiksborg) could become extinct within 40 yr. The sensitivity analyses indicated that the variables concerning reproduction of the mares had the greatest impact, with the number of mares actively breeding being the most influential on the population forecasts. The results suggest that closing the Knabstrupper studbooks can be done only if increasing the number of mares actively breeding counteracts the loss of genetic variation attributable to such a management strategy. It is recommended, based on these results, that the number of Frederiksborg and Knabstrupper mares actively breeding must be increased to approximately 30% in the 2 breeds that are presently using only 13%, while leaving the third (Frederiksborg) at its present 30% level. Monitoring of the breeds in the future, however, may be exploited to adjust the breeding strategies. We suggest that the large amount of data required by Vortex makes it very useful for analyzing domestic animals because of the comprehensive data material often available. The results of this analysis accord with other studies on the Prezwalski horse, indicating robustness in the parameter sensitivity for horses.
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| 7. |
- Wallace, Megan A., et al.
(författare)
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The discovery, distribution, and diversity of DNA viruses associated with Drosophila melanogaster in Europe
- 2021
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Ingår i: Virus Evolution. - : Oxford University Press (OUP). - 2057-1577. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- Drosophila melanogaster is an important model for antiviral immunity in arthropods, but very few DNA viruses have been described from the family Drosophilidae. This deficiency limits our opportunity to use natural host-pathogen combinations in experimental studies, and may bias our understanding of the Drosophila virome. Here, we report fourteen DNA viruses detected in a metagenomic analysis of 6668 pool-sequenced Drosophila, sampled from forty-seven European locations between 2014 and 2016. These include three new nudiviruses, a new and divergent entomopoxvirus, a virus related to Leptopilina boulardi filamentous virus, and a virus related to Musca domestica salivary gland hypertrophy virus. We also find an endogenous genomic copy of galbut virus, a double-stranded RNA partitivirus, segregating at very low frequency. Remarkably, we find that Drosophila Vesanto virus, a small DNA virus previously described as a bidnavirus, may be composed of up to twelve segments and thus represent a new lineage of segmented DNA viruses. Two of the DNA viruses, Drosophila Kallithea nudivirus and Drosophila Vesanto virus are relatively common, found in 2 per cent or more of wild flies. The others are rare, with many likely to be represented by a single infected fly. We find that virus prevalence in Europe reflects the prevalence seen in publicly available datasets, with Drosophila Kallithea nudivirus and Drosophila Vesanto virus the only ones commonly detectable in public data from wild-caught flies and large population cages, and the other viruses being rare or absent. These analyses suggest that DNA viruses are at lower prevalence than RNA viruses in D.melanogaster, and may be less likely to persist in laboratory cultures. Our findings go some way to redressing an earlier bias toward RNA virus studies in Drosophila, and lay the foundation needed to harness the power of Drosophila as a model system for the study of DNA viruses.
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