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- Nilsson-Örtman, Viktor, 1984-, et al.
(author)
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Using taxonomic revision data to estimate the global species richness and characteristics of undescribed species of diving beetles (Coleoptera: Dytiscidae)
- 2010
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In: Biodiversity Informatics. - Kansas : University of Kansas. - 1546-9735. ; 7:1, s. 1-16
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Journal article (peer-reviewed)abstract
- Many methods used for estimating species richness are either difficult to use on poorly known taxa or require input data that are laborious and expensive to collect. In this paper we apply a method which takes advantage of the carefully conducted tests of how the described diversity compares to real species richness that are inherent in taxonomic revisions. We analyze the quantitative outcome from such revisions with respect to body size, zoogeographical region and phylogenetic relationship. The best fitting model is used to predict the diversity of unrevised groups if these would have been subject to as rigorous species level hypothesis-testing as the revised groups. The sensitivity of the predictive model to single observations is estimated by bootstrapping over resampled subsets of the original data. The Dytiscidae is with its 4080 described species (end of May 2009) the most diverse group of aquatic beetles and have a world-wide distribution. Extensive taxonomic work has been carried out on the family but still the number of described species increases exponentially in most zoogeographical regions making many commonly used methods of estimation difficult to apply. We provide independent species richness estimates of subsamples for which species richness estimates can be reached through extrapolation and compare these to the species richness estimates obtained through the method using revision data. We estimate there to be 5405 species of dytiscids, a 1.32-fold increase over the present number of described species. The undescribed diversity is likely to be biased towards species with small body size from tropical regions outside of Africa.
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| 2. |
- Nilsson-Örtman, Viktor, 1984-, et al.
(author)
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Latitudinal patterns of phenology and age-specific thermal performance across six Coenagrion damselfly species
- 2013
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In: Ecological Monographs. - : Ecological society of America. - 0012-9615 .- 1557-7015. ; 83:4, s. 491-510
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Journal article (peer-reviewed)abstract
- Using a combination of computer simulations and laboratory experiments we test if the thermal sensitivity of growth rates change during ontogeny in damselfly larvae and if these changes can be predicted based on the natural progression of average temperature or thermal variability in the field. The laboratory experiment included replicated species from Southern, Central, and Northern Europe. Although annual fluctuations in temperature represent a key characteristic of temperate environments, few studies of thermal performance have considered the ecological importance of the studied traits within a seasonal context. Instead, thermal performance is assumed to remain constant throughout ontogeny and to reflect selection acting over the whole life cycle. The laboratory experiment revealed considerable variation among species in the strength and direction of ontogenetic performance shifts. In four species from Southern and Central Europe, reaction norms were steepest during early ontogeny, becoming less steep during later ontogenetic stages (indicative of low-temperature acclimation). In one Northern European species, the slope of reaction norms did not change during ontogeny. In the other North European species, reaction norms became steeper during ontogeny (indicative of high-temperature acclimation). We had expected high-latitude species to show strong low-temperature acclimation responses, because they have a short flight season and inhabit a strongly seasonal environment. Instead, we found the reversed pattern: Low-latitude species displayed strong low-temperature acclimation responses, and high-latitude species displayed weak, or even reversed, acclimation responses to low temperatures. These findings suggest that low-temperature acclimation may be less beneficial and possibly more costly in habitats with rapid seasonal transitions in average temperature. We conclude that thermal performance traits are more dynamic than typically assumed and caution against using results from single ontogenetic stages to predict species' responses to changing environmental conditions.
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| 3. |
- Nilsson-Örtman, Viktor, 1984-, et al.
(author)
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Latitudinally structured variation in the temperature dependence of damselfly growth rates
- 2013
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In: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 16:1, s. 64-71
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Journal article (peer-reviewed)abstract
- The Metabolic Theory of Ecology predicts that the slope of the rate-temperature relationship, E, remains consistent across traits and organisms, acting as a major determinant of large-scale ecological patterns. Although E has recently been shown to vary systematically, we have a poor understanding of its ecological significance. To address this question, we conducted a common-garden experiment involving six damselfly species differing in distribution, estimating E at the level of full-sib families. Each species was sampled throughout its latitudinal range, allowing us to characterise variation in E along a latitudinal gradient spanning 3600 km. We show that E differs among populations and increases with latitude. E was right-skewness across species, but this was largely an artefact of the latitudinal trend. Increased seasonality towards higher latitude may contribute to the latitudinal trend in E. We conclude that E should be seen as a trait involved in local adaptation.
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| 4. |
- Nilsson-Örtman, Viktor, 1984-
(author)
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Thermal adaptation along a latitudinal gradient in damselflies
- 2012
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Doctoral thesis (other academic/artistic)abstract
- Understanding how temperature affects biological systems is a central question in ecology and evolutionary biology. Anthropogenic climate change adds urgency to this topic, as the demise or success of species under climate change is expected to depend on how temperature affects important aspects of organismal performance, such as growth, development, survival and reproduction. Rates of biological processes generally increase with increasing temperature up to some maximal temperature. Variation in the slope of the initial, rising phase has attracted considerable interest and forms the focus of this thesis. I explore variation in growth rate-temperature relationships over several levels of biological organization, both between and within species, over individuals’ lifetime, depending on the ecological context and in relation to important life history characteristics such as generation length and winter dormancy. Specifically, I examine how a clade of temperate damselflies have adapted to their thermal environment along a 3,600 km long latitudinal transect spanning from Southern Spain to Northern Sweden. For each of six species, I sampled populations from close to the northern and southern range margin, as well from the center of the latitudinal range. I reared larvae in the laboratory at several temperatures in order to measure indiviudal growth rates. Very few studies of thermal adaptation have employed such an extensive sampling approach, and my finding reveal variation in temperature responses at several levels of organization. My main finding was that temperature responses became steeper with increasing latitude, both between species but also between latitudinal populations of the same species. Additional genetic studies revealed that this trend was maintained despite strong gene flow. I highlight the need to use more refined characterizations of latitudinal temperature clines in order to explain these findings. I also show that species differ in their ability to acclimate to novel conditions during ontogeny, and propose that this may reflect a cost-benefit trade-off driven by whether seasonal transitions occur rapidly or gradually during ontogeny. I also carried out a microcosm experiment, where two of the six species were reared either separately or together, to determine the interacting effects of temperature and competition on larval growth rates and population size structure. The results revealed that the effects of competition can be strong enough to completely overcome the rate-depressing effects of low temperatures. I also found that competition had stronger effects on the amount of variation in growth rates than on the average value. In summary, my thesis offers several novel insights into how temperature affects biological systems, from individuals to populations and across species’ ranges. I also show how it is possible to refine our hypotheses about thermal adaptation by considering the interacting effects of ecology, life history and environmental variation.
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