SwePub
Sök i SwePub databas

  Utökad sökning

Träfflista för sökning "WFRF:(Ehrlén Johan) srt2:(2015-2019)"

Sökning: WFRF:(Ehrlén Johan) > (2015-2019)

  • Resultat 11-20 av 38
  • Föregående 1[2]34Nästa
Sortera/gruppera träfflistan
   
NumreringReferensOmslagsbildHitta
11.
  • Bolinder, Kristina, et al. (författare)
  • From near extinction to diversification by means of ashift in pollination mechanism in the gymnosperm relict Ephedra (Ephedraceae, Gnetales)
  • 2016
  • Ingår i: Botanical journal of the Linnean Society. - 0024-4074 .- 1095-8339. ; 180:4, s. 461-477
  • Tidskriftsartikel (refereegranskat)abstract
    • Pollination in gymnosperms is usually accomplished by means of wind, but some groups are insect-pollinated. We show that wind and insect pollination occur in the morphologically uniform genus Ephedra (Gnetales). Based on field experiments over several years, we demonstrate distinct differences between two Ephedra species that grow in sympatry in Greece in pollen dispersal and clump formation, insect visitations and embryo formation when insects are denied access to cones. Ephedra distachya, nested in the core clade of Ephedra, is anemophilous, which is probably the prevailing state in Ephedra. Ephedra foeminea, sister to the remaining species of the genus, is entomophilous and pollinated by a range of diurnal and nocturnal insects. The generalist entomophilous system of E.foeminea, with distinct but infrequent insect visitations, is in many respects similar to that reported for Gnetum and Welwitschia and appears ancestral in Gnetales. The Ephedra lineage is well documented already from the Early Cretaceous, but the diversity declined dramatically during the Late Cretaceous, possibly to near extinction around the Cretaceous-Palaeogene boundary. The clade imbalance between insect- and wind-pollinated lineages is larger than expected by chance and the shift in pollination mode may explain why Ephedra escaped extinction and began to diversify again.
  •  
12.
  • Bolinder, Kristina, 1987- (författare)
  • Pollen and pollination in Ephedra (Gnetales)
  • 2017
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Ephedra (Gnetales) is a gymnosperm genus with a long evolutionary history; the first dispersed pollen grains with affinity to the group are known already from the Permian. This thesis focuses on the evolutionary history of the group and different aspects of its pollination mechanisms. Despite the limited number of extant species of the genus (50-60), and a low morphological and genetic divergence among species, there is variation in pollination syndrome in the genus. The prevailing state in Ephedra, and most gymnosperms, is wind pollination. It is therefore surprising that one species, E. foeminea, is insect-pollinated. Together with co-workers I documented the pollination syndromes of E. foeminea and a sympatric species, E. distachya, based on long term field experiments in north-eastern Greece and aerodynamic investigations and calculations. Placing the results into an evolutionary framework reveals that the insect-pollinated species E. foeminea is sister to the remaining (mostly wind-pollinated) genus, and indicates that insect pollination is the ancestral state in the Gnetales. During the course of evolution of the group there has been a shift to wind pollination, which may have played a crucial role for the diversification of the crown group in the Paleogene. Pollination biology is often correlated with the morphology of the pollen such that pollen grains of anemophilous plants are small with a smooth surface, whereas pollen grains of entomophilous plants are larger with an ornamented surface and a covering of pollenkitt. The pollen morphology of Ephedra can be broadly divided into two types: an ancestral type with an unbranched pseudosulcus between each pair of plicae, and a derived type with a branched pseudosulcus between each pair of plicae. Further, the pollen morphology and ultrastructure of the pollen wall in Ephedra are to some degree correlated with the pollination syndrome and capability of long distance dispersal. Pollen of E. foeminea has a denser ultrastructure, as a result a higher settling velocity and is therefore capable of flying shorter distances than does pollen of the anemophilous E. distachya, and other investigated anemophilous species that show a more spacious ultrastructure of the pollen grain. These results can be useful in the reconstruction of the pollination mechanism of extinct taxa of the Ephedra-lineage in the future.
  •  
13.
  • Ehrlén, Johan, et al. (författare)
  • Predicting changes in the distribution and abundance of species under environmental change
  • 2015
  • Ingår i: Ecology Letters. - 1461-023X .- 1461-0248. ; 18:3, s. 303-314
  • Forskningsöversikt (refereegranskat)abstract
    • Environmental changes are expected to alter both the distribution and the abundance of organisms. A disproportionate amount of past work has focused on distribution only, either documenting historical range shifts or predicting future occurrence patterns. However, simultaneous predictions of abundance and distribution across landscapes would be far more useful. To critically assess which approaches represent advances towards the goal of joint predictions of abundance and distribution, we review recent work on changing distributions and on effects of environmental drivers on single populations. Several methods have been used to predict changing distributions. Some of these can be easily modified to also predict abundance, but others cannot. In parallel, demographers have developed a much better understanding of how changing abiotic and biotic drivers will influence growth rate and abundance in single populations. However, this demographic work has rarely taken a landscape perspective and has largely ignored the effects of intraspecific density. We advocate a synthetic approach in which population models accounting for both density dependence and effects of environmental drivers are used to make integrated predictions of equilibrium abundance and distribution across entire landscapes. Such predictions would constitute an important step forward in assessing the ecological consequences of environmental changes.
  •  
14.
  • Ehrlén, Johan (författare)
  • Selection on flowering time in a life-cycle context
  • 2015
  • Ingår i: Oikos. - 0030-1299 .- 1600-0706. ; 124:1, s. 92-101
  • Tidskriftsartikel (refereegranskat)abstract
    • The main way in which plants can exert control over their local environment is by the timing of different events within their life cycles. Regarding timing of flowering as an integrated part of both the annual cycle and of the whole life cycle, rather than as an isolated event, has important implications for how we assess selection on timing of reproduction and interpret existing phenological patterns in perennial plants. I argue that: 1) we have little unequivocal evidence of pollinator-mediated selection on flowering time, but perhaps more evidence of antagonist-mediated selection; 2) much of selection on flowering time might occur before flowers have developed and after reproduction; 3) vital rates of non-flowering individuals can influence the strength and direction of selection on flowering time, and 4) differences in the direction of selection on flowering date between years might well correspond to consistent selection on the mechanisms determining flowering time. Overall, a life cycle perspective on timing of flowering is likely to facilitate the identification of selective agents and the understanding of the complex mechanisms underlying spatial and temporal variation in selection as well as to enable more accurate predictions of responses to environmental change.
  •  
15.
  • Elmhagen, Bodil, et al. (författare)
  • Interacting effects of change in climate, human population, land use, and water use on biodiversity and ecosystem services
  • 2015
  • Ingår i: Ecology & Society. - 1708-3087. ; 20:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Human population growth and resource use, mediated by changes in climate, land use, and water use, increasingly impact biodiversity and ecosystem services provision. However, impacts of these drivers on biodiversity and ecosystem services are rarely analyzed simultaneously and remain largely unknown. An emerging question is how science can improve the understanding of change in biodiversity and ecosystem service delivery and of potential feedback mechanisms of adaptive governance. We analyzed past and future change in drivers in south-central Sweden. We used the analysis to identify main research challenges and outline important research tasks. Since the 19th century, our study area has experienced substantial and interlinked changes; a 1.6 degrees C temperature increase, rapid population growth, urbanization, and massive changes in land use and water use. Considerable future changes are also projected until the mid-21st century. However, little is known about the impacts on biodiversity and ecosystem services so far, and this in turn hampers future projections of such effects. Therefore, we urge scientists to explore interdisciplinary approaches designed to investigate change in multiple drivers, underlying mechanisms, and interactions over time, including assessment and analysis of matching-scale data from several disciplines. Such a perspective is needed for science to contribute to adaptive governance by constantly improving the understanding of linked change complexities and their impacts.
  •  
16.
  • Fogelström, Elsa, et al. (författare)
  • Phenotypic but not genotypic selection for earlier flowering in a perennial herb
  • 2019
  • Ingår i: Journal of Ecology. - 0022-0477 .- 1365-2745. ; 107:6, s. 2650-2659
  • Tidskriftsartikel (refereegranskat)abstract
    • 1. Timing of reproduction affects the outcome of interactions between plants and their pollinators, grazers and seed predators, as well as with their local abiotic environment. In seasonal environments, phenotypic selection has often been shown to favour early flowering. Yet, we still know little about the agents driving selection in natural populations and whether observed phenotypic selection corresponds to genotypic selection – a prerequisite for evolutionary change.2. In this study, we experimentally assessed phenotypic and genotypic selection for flowering time in a natural population of the perennial herb Lathyrus vernus. We transplanted sibling individuals, obtained through controlled crosses, to their source population and found net phenotypic selection for earlier flowering in the field.3. Despite a higher susceptibility to roe deer grazing, early‐flowering plants had higher fruit set and more seeds per fruit than late‐flowering plants. We found no support for genotypic selection on flowering time, and heritability for first flowering day was very low.4. Synthesis: Our results suggest that commonly observed patterns of higher fitness in early‐flowering plants do not always correspond to selection on genotypic values and are thus not necessarily expected to result in evolutionary change even if the relationship between flowering time and fitness is causal. This finding should be important to understand how species phenology might respond to changing environmental conditions.
  •  
17.
  • Graae, Bente J., et al. (författare)
  • Stay or go - how topographic complexity influences alpine plant population and community responses to climate change
  • 2018
  • Ingår i: Perspectives in plant ecology, evolution and systematics. - 1433-8319 .- 1618-0437. ; 30, s. 41-50
  • Tidskriftsartikel (refereegranskat)abstract
    • In the face of climate change, populations have two survival options - they can remain in situ and tolerate the new climatic conditions (stay), or they can move to track their climatic niches (go). For sessile and small-stature organisms like alpine plants, staying requires broad climatic tolerances, realized niche shifts due to changing biotic interactions, acclimation through plasticity, or rapid genetic adaptation. Going, in contrast, requires good dispersal and colonization capacities. Neither the magnitude of climate change experienced locally nor the capacities required for staying/going in response to climate change are constant across landscapes, and both aspects may be strongly affected by local microclimatic variation associated with topographic complexity. We combine ideas from population and community ecology to discuss the effects of topographic complexity in the landscape on the immediate stay or go opportunities of local populations and communities, and on the selective pressures that may have shaped the stay or go capacities of the species occupying contrasting landscapes. We demonstrate, using example landscapes of different topographical complexity, how species' thermal niches could be distributed across these landscapes, and how these, in turn, may affect many population and community ecological processes that are related to adaptation or dispersal. Focusing on treeless alpine or Arctic landscapes, where temperature is expected to be a strong determinant, our theorethical framework leads to the hypothesis that populations and communities of topographically complex (rough and patchy) landscapes should be both more resistant and more resilient to climate change than those of topographically simple (flat and homogeneous) landscapes. Our theorethical framework further points to how meta-community dynamics such as mass effects in topographically complex landscapes and extinction lags in simple landscapes, may mask and delay the long-term outcomes of these landscape differences under rapidly changing climates.
  •  
18.
  • Greiser, Caroline, et al. (författare)
  • Monthly microclimate models in a managed boreal forest landscape
  • 2018
  • Ingår i: Agricultural and Forest Meteorology. - 0168-1923 .- 1873-2240. ; 250-251, s. 147-158
  • Tidskriftsartikel (refereegranskat)abstract
    • The majority of microclimate studies have been done in topographically complex landscapes to quantify and predict how near-ground temperatures vary as a function of terrain properties. However, in forests understory temperatures can be strongly influenced also by vegetation. We quantified the relative influence of vegetation features and physiography (topography and moisture-related variables) on understory temperatures in managed boreal forests in central Sweden. We used a multivariate regression approach to relate near-ground temperature of 203 loggers over the snow-free seasons in an area of ∼16,000 km2 to remotely sensed and on-site measured variables of forest structure and physiography. We produced climate grids of monthly minimum and maximum temperatures at 25 m resolution by using only remotely sensed and mapped predictors. The quality and predictions of the models containing only remotely sensed predictors (MAP models) were compared with the models containing also on-site measured predictors (OS models). Our data suggest that during the warm season, where landscape microclimate variability is largest, canopy cover and basal area were the most important microclimatic drivers for both minimum and maximum temperatures, while physiographic drivers (mainly elevation) dominated maximum temperatures during autumn and early winter. The MAP models were able to reproduce findings from the OS models but tended to underestimate high and overestimate low temperatures. Including important microclimatic drivers, particularly soil moisture, that are yet lacking in a mapped form should improve the microclimate maps. Because of the dynamic nature of managed forests, continuous updates of mapped forest structure parameters are needed to accurately predict temperatures. Our results suggest that forest management (e.g. stand size, structure and composition) and conservation may play a key role in amplifying or impeding the effects of climate-forcing factors on near-ground temperature and may locally modify the impact of global warming.
  •  
19.
  • Hylander, Kristoffer, et al. (författare)
  • Microrefugia : Not for everyone
  • 2015
  • Ingår i: Ambio. - 0044-7447 .- 1654-7209. ; 44, s. s60-S68
  • Tidskriftsartikel (refereegranskat)abstract
    • Microrefugia are sites that support populations of species when their ranges contract during unfavorable climate episodes. Here, we review and discuss two aspects relevant for microrefugia. First, distributions of different species are influenced by different climatic variables. Second, climatic variables differ in the degree of local decoupling from the regional climate. Based on this, we suggest that only species limited by climatic conditions decoupled from the regional climate can benefit from microrefugia. We argue that this restriction has received little attention in spite of its importance for microrefugia as a mechanism for species resilience (the survival of unfavorable episodes and subsequent range expansion). Presence of microrefugia will depend on both the responses of individual species to local climatic variation and how climate-forcing factors shape the correlation between local and regional climate across space and time.
  •  
20.
  • Inouye, Brian D., et al. (författare)
  • Phenology as a process rather than an event : from individual reaction norms to community metrics
  • 2019
  • Ingår i: Ecological Monographs. - 0012-9615 .- 1557-7015. ; 89:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Measures of the seasonal timing of biological events are key to addressing questions about how phenology evolves, modifies species interactions, and mediates biological responses to climate change. Phenology is often characterized in terms of discrete events, such as a date of first flowering or arrival of first migrants. We discuss how phenological events that are typically measured at the population or species level arise from distributions of phenological events across seasons, and from norms of reaction of these phenological events across environments. We argue that individual variation in phenological distributions and reaction norms has important implications for how we should collect, analyze, and interpret phenological information. Regarding phenology as a reaction norm rather than one year's specific values implies that selection acts on the phenologies that an individual expresses over its lifetime. To understand how climate change is likely to influence phenology, we need to consider not only plastic responses along the reaction norm but changes in the reaction norm itself. We show that when individuals vary in their reaction norms, correlations between reaction norm elevation and slope make first events particularly poor estimators of population sensitivity to climate change, and variation in slopes can obscure the pattern of selection on phenology. We also show that knowing the shape of the distribution of phenological events across the season is important for predicting biologically important phenological mismatches with climate change. Last, because phenological events are parts of a continuous developmental process, we suggest that the approach of measuring phenology by recording developmental stages of individuals in a population at a single point in time should be used more widely. We conclude that failure to account for phenological distributions and reaction norms may lead to overinterpretation of metrics based on single events, such as commonly recorded first event dates, and may confound meta-analyses that use a range of metrics. Rather than prescribing a single universal approach to studying phenology, we point out limitations of inferences based on single metrics and encourage work that considers the multivariate nature of phenology and more tightly links data collection and analyses with biological hypotheses.
  •  
Skapa referenser, mejla, bekava och länka
  • Resultat 11-20 av 38
  • Föregående 1[2]34Nästa
Typ av publikation
tidskriftsartikel (31)
doktorsavhandling (6)
forskningsöversikt (1)
Typ av innehåll
refereegranskat (32)
övrigt vetenskapligt (6)
Författare/redaktör
Ehrlén, Johan (32)
Wiklund, Christer (10)
Gotthard, Karl (7)
Ehrlén, Johan, Profe ... (6)
Dahlgren, Johan P (6)
Hylander, Kristoffer (4)
visa fler...
Meineri, Eric (2)
Luoto, Miska (2)
Morris, William F. (2)
Hambäck, Peter A. (2)
Olofsson, Martin (2)
Gotthard, Karl, Doce ... (1)
Humphreys, Aelys M. (1)
Cousins, Sara A. O. (1)
Plue, Jan (1)
Boyd, Emily (1)
Borgström, Sara (1)
Angerbjörn, Anders (1)
Jaramillo, Fernando (1)
Hedlund, Johanna (1)
Ågren, Jon (1)
Andersson, Petter (1)
Lyon, Steve W. (1)
Lindborg, Regina (1)
Destouni, Georgia (1)
Winder, Monika, Prof ... (1)
Armbruster, W. Scott (1)
Leimar, Olof (1)
Hedenäs, Lars (1)
Vandvik, Vigdis (1)
Dalen, Love (1)
Rydin, Catarina (1)
Alexandersson, Ronny (1)
Nykvist, Björn (1)
Bengtsson, Karin (1)
Klanderud, Kari (1)
Elmhagen, Bodil (1)
Marteinsdottir, Bryn ... (1)
Karlsson, Bengt (1)
Bruun, Hans Henrik (1)
Ejrnaes, Rasmus (1)
Graae, Bente J (1)
Speed, James D. M. (1)
Brathen, Kari Anne (1)
Milbau, Ann (1)
Birks, Hilary H. (1)
Bisang, Irene (1)
Lehtilä, Kari (1)
Eiserhardt, Wolf L. (1)
Birks, H. John B. (1)
visa färre...
Lärosäte
Stockholms universitet (38)
Uppsala universitet (5)
Kungliga Tekniska Högskolan (1)
Södertörns högskola (1)
Naturhistoriska riksmuseet (1)
Sveriges Lantbruksuniversitet (1)
Språk
Engelska (38)
Forskningsämne (UKÄ/SCB)
Naturvetenskap (38)

År

Kungliga biblioteket hanterar dina personuppgifter i enlighet med EU:s dataskyddsförordning (2018), GDPR. Läs mer om hur det funkar här.
Så här hanterar KB dina uppgifter vid användning av denna tjänst.

 
pil uppåt Stäng

Kopiera och spara länken för att återkomma till aktuell vy