Browsing by Subject "Dispersal"

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  • Lehtonen, Topi K.; Babic, Natarsha L.; Piepponen, Timo; Valkeeniemi, Otso; Borshagovski, Anna-Maria; Kaitala, Arja (2021)
    Animals often disperse from one habitat to another to access mates or suitable breeding sites. The costs and benefits of such movements depend, in part, on the dispersing individuals' phenotypes, including their sex and age. Here we investigated dispersal and road-related mortality in larvae of a bioluminescent beetle, the European common glow-worm, Lampyris noctiluca, in relation to habitat, sex and proximity of pupation. We expected these variables to be relevant to larval dispersal because adult females are wingless, whereas adult males fly when searching for glowing females. We found that dispersing glow-worm larvae were almost exclusively females and close to pupation. The larvae were often found on a road, where they were able to move at relatively high speeds, with a tendency to uphill orientation. However, each passing vehicle caused a high mortality risk, and we found large numbers of larvae run over by cars, especially close to covered, forest-like habitat patches. In contrast, adult females in the same area were most often found glowing in more open rocky and grassy habitats. These findings demonstrate an underappreciated ecological strategy, sex-biased dispersal at larval phase, motivated by different habitat needs of larvae and wingless adult females. The results are also consistent with roads being an ecological trap, facilitating dispersal and presumably females' signal visibility but causing severe larval mortality just before the reproductive stage. Hence, in addition to the previously recognised threats of urbanisation, even low traffic volumes have a high potential to negatively affect especially females of this iconic beetle. Significance statement Animals sometimes need to move from one habitat to another to find mating partners or breeding sites. We found this need to result in strongly female-biased larval dispersal in the European common glow-worm, a beetle known for the glow of wingless females that attract flying males to mate. Female larvae moving between habitats often used a road or trail but perished in high numbers when run over by cars. Hence, roads are likely to be ecological traps for the female glow-worm larvae, attracting them during dispersal, but causing grave mortality. The sex-biased larval dispersal, demonstrated in this study, is a poorly known ecological strategy that was found to be very risky in a human-modified landscape.
  • DiLeo, Michelle F.; Husby, Arild; Saastamoinen, Marjo (2018)
    There is now clear evidence that species across a broad range of taxa harbor extensive heritable variation in dispersal. While studies suggest that this variation can facilitate demographic outcomes such as range expansion and invasions, few have considered the consequences of intraspecific variation in dispersal for the maintenance and distribution of genetic variation across fragmented landscapes. Here, we examine how landscape characteristics and individual variation in dispersal combine to predict genetic structure using genomic and spatial data from the Glanville fritillary butterfly. We used linear and latent factor mixed models to identify the landscape features that best predict spatial sorting of alleles in the dispersal-related gene phosphoglucose isomerase (Pgi). We next used structural equation modeling to test if variation in Pgi mediated gene flow as measured by F-st at putatively neutral loci. In a year when the population was recovering following a large decline, individuals with a genotype associated with greater dispersal ability were found at significantly higher frequencies in populations isolated by water and forest, and these populations showed lower levels of genetic differentiation at neutral loci. These relationships disappeared in the next year when metapopulation density was high, suggesting that the effects of individual variation are context dependent. Together our results highlight that (1) more complex aspects of landscape structure beyond just the configuration of habitat can be important for maintaining spatial variation in dispersal traits and (2) that individual variation in dispersal plays a key role in maintaining genetic variation across fragmented landscapes.
  • Gyllenberg, Mats; Kisdi, Eva; Weigang, Helene C. (2016)
    Empirical studies of dispersal indicate that decisions to immigrate are patch-type dependent; yet theoretical models usually ignore this fact. Here, we investigate the evolution of patch-type dependent immigration of a population inhabiting and dispersing in a heterogeneous landscape, which is structured by patches of low and high reward. We model the decision to immigrate in detail from a mechanistic underpinning. With the methods of adaptive dynamics, we derive both analytical and numerical results for the evolution of immigration when life-history traits are patch-type dependent. The model exhibits evolutionary branching in a wide parameter range and the subsequent coevolution can lead to a stable coexistence of a generalist, settling in patches of any type, and a specialist that only immigrates into patches of high reward. We find that individuals always settle in the patches of high reward, in which survival until maturation, relative fecundity and emigration probability are high. We investigate how the probability to immigrate into patches of low reward changes with model parameters. For example, we show that immigration into patches of low reward increases when the emigration probability in these patches increases. Further, immigration into patches of low reward decreases when the patches of high reward become less safe during the dispersal season. (C) 2016 Elsevier Ltd. All rights reserved.
  • Selonen, Vesa; Remm, Jaanus; Hanski, Ilpo K.; Henttonen, Heikki; Huitu, Otso; Jokinen, Maarit; Korpimäki, Erkki; Makela, Antero; Sulkava, Risto; Wistbacka, Ralf (2019)
    Climatic conditions, trophic links between species and dispersal may induce spatial synchrony in population fluctuations. Spatial synchrony increases the extinction risk of populations and, thus, it is important to understand how synchrony-inducing mechanisms affect populations already threatened by habitat loss and climate change. For many species, it is unclear how population fluctuations vary over time and space, and what factors potentially drive this variation. In this study, we focus on factors determining population fluctuations and spatial synchrony in the Siberian flying squirrel, Pteromys volans, using long-term monitoring data from 16 Finnish populations located 2-400 km apart. We found an indication of synchronous population dynamics on a large scale in flying squirrels. However, the synchrony was not found to be clearly related to distance between study sites because the populations seemed to be strongly affected by small-scale local factors. The regularity of population fluctuations varied over time. The fluctuations were linked to changes in winter precipitation, which has previously been linked to the reproductive success of flying squirrels. Food abundance (tree mast) and predator abundance were not related to population fluctuations in this study. We conclude that spatial synchrony was not unequivocally related to distance in flying squirrels, as has been observed in earlier studies for more abundant rodent species. Our study also emphasises the role of climate in population fluctuations and the synchrony of the species.
  • Seppä, Perttu; Bonelli, Mariaelena; Dupont, Simon; Hakala, Sanja Maria; Bagnères, Anne-Geneviève; Lorenzi, M. Cristina (2020)
    Simple Summary The co-evolution of hosts and parasites depends on their ability to adapt to each other's defense and counter-defense mechanisms. The strength of selection on those mechanisms may vary among populations, resulting in a geographical mosaic of co-evolution. The boreo-montane paper wasp Polistes biglumis and its parasite Polistes atrimandibularis exemplify this type of co-evolutionary system. Here, we used genetic markers to examine the genetic population structures of these wasps in the western Alps. We found that both host and parasite populations displayed similar levels of genetic variation. In the host species, populations located near to each other were genetically similar; in both the host and the parasite species populations farther apart were significantly different. Thus, apparent dispersal barriers (i.e., high mountains) did not seem to restrict gene flow across populations as expected. Furthermore, there were no major differences in gene flow between the two species, perhaps because P. atrimandibularis parasitizes both alpine and lowland host species and annually migrates between alpine and lowland populations. The presence of strong gene flow in a system where local populations experience variable levels of selection pressure challenges the classical hypothesis that restricted gene flow is required for local adaptations to evolve. The co-evolutionary pathways followed by hosts and parasites strongly depend on the adaptive potential of antagonists and its underlying genetic architecture. Geographically structured populations of interacting species often experience local differences in the strength of reciprocal selection pressures, which can result in a geographic mosaic of co-evolution. One example of such a system is the boreo-montane social wasp Polistes biglumis and its social parasite Polistes atrimandibularis, which have evolved local defense and counter-defense mechanisms to match their antagonist. In this work, we study spatial genetic structure of P. biglumis and P. atrimandibularis populations at local and regional scales in the Alps, by using nuclear markers (DNA microsatellites, AFLP) and mitochondrial sequences. Both the host and the parasite populations harbored similar amounts of genetic variation. Host populations were not genetically structured at the local scale, but geographic regions were significantly differentiated from each other in both the host and the parasite in all markers. The net dispersal inferred from genetic differentiation was similar in the host and the parasite, which may be due to the annual migration pattern of the parasites between alpine and lowland populations. Thus, the apparent dispersal barriers (i.e., high mountains) do not restrict gene flow as expected and there are no important gene flow differences between the species, which contradict the hypothesis that restricted gene flow is required for local adaptations to evolve.
  • Cucchi, Thomas; Barnett, Ross; Martinkova, Natalia; Renaud, Sabrina; Renvoise, Elodie; Evin, Allowen; Sheridan, Alison; Mainland, Ingrid; Wickham-Jones, Caroline; Tougard, Christelle; Quere, Jean Pierre; Pascal, Michel; Pascal, Marine; Heckel, Gerald; O'Higgins, Paul; Searle, Jeremy B.; Dobney, Keith M. (2014)