| 1. |
- Conde-Padin, P., et al.
(författare)
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Revealing the mechanisms of sexual isolation in a case of sympatric and parallel ecological divergence
- 2008
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Ingår i: Biological Journal of the Linnean Society. - : Oxford University Press (OUP). - 0024-4066 .- 1095-8312. ; 94:3, s. 513-526
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Tidskriftsartikel (refereegranskat)abstract
- Two ecotypes of a marine intertidal snail (Littorina saxatilis), living at different microhabitats and shore levels, have evolved in sympatry and in parallel across the Galician rocky shore. These ecotypes differ in many traits (including size) due to differential adaptation. They meet, mate assortatively, and partially hybridize at the mid shore where the two microhabitats overlap. The partial sexual isolation observed is claimed to be a side-effect of the size differences between ecotypes combined with a size assortative mating found in most populations of this species. We investigated this hypothesis using three complementary experimental approaches. First, we investigated which of the different shell variables contributed most to the variation in individual sexual isolation in the field by using two new statistics developed for that purpose: (1) pair sexual isolation and (2) r(i), which is based on the Pearson correlation coefficient. We found that size is the most important trait explaining the sexual isolation and, in particular, the males appear to be the key sex contributing to sexual isolation. Second, we compared the size assortative mating between regions: exposed rocky shore populations from north-westwern Spain (showing incomplete reproductive isolation due to size assortative mating) and protected Spanish and Swedish populations (showing size assortative mating but not reproductive isolation between ecomorphs). Most of the variation in size assortative mating between localities was significantly explained by the within-population level of variation on size. Third, we performed a laboratory male choice experiment, which further suggested that the choice is made predominantly on the basis of size. These results confirm the mechanism proposed to explain the sexual isolation in the Galician hybrid zone and thus support this case as a putative example of parallel incipient speciation. (C) 2008 The Linnean Society of London.
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| 2. |
- Isaksson, Caroline, 1976, et al.
(författare)
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Sex and age differences in reflectance and biochemistry of carotenoid-based colour variation in the great tit Parus major
- 2008
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Ingår i: Biological Journal of the Linnean Society. - : Oxford University Press (OUP). - 0024-4066 .- 1095-8312. ; 95:4, s. 758-765
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Tidskriftsartikel (refereegranskat)abstract
- The plumage coloration in great tits (Parus major) is the subject of much behavioural and ecophysiological research, yet there is a lack of analyses of the natural colour variation and its mechanisms. We used reflectance spectrometry and high-performance liquid chromatography to explore individual, sexual and age-related variation in carotenoid coloration and pigmentation, paramount to the often presumed, but rarely substantiated, costs and 'honesty' of carotenoid displays. In adults, we found that sex was the strongest predictor of 'brightness' (higher in males) and of 'hue' (longer wavelength in females). There was no sex difference in 'carotenoid chroma' or carotenoid content of feathers which also was unrelated to adult age (1 or 2+ years) and condition. Similar patterns were revealed for nestlings. Regarding the biochemical 'signal content', 'carotenoid chroma', but not 'hue', was significantly related to the carotenoid content (lutein and zeaxanthin) of feathers. These results refute the previously assumed exaggeration of carotenoid pigmentation in male great tits, and question the condition-dependence of carotenoid coloration in this species. However, the sexual dimorphism in total reflectance or 'brightness', most likely due to melanins rather than carotenoids, may have implications for signalling or other adaptive explanations that need to be explored.
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| 3. |
- Jörgensen, Tove
(författare)
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The importance of phylogeny and ecology in microgeographical variation in the morphology of four Canarian species of Aeonium (Crassulaceae)
- 2002
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Ingår i: Biological Journal of the Linnean Society. - : Oxford University Press (OUP). - 0024-4066 .- 1095-8312. ; 76:4, s. 521-533
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Tidskriftsartikel (refereegranskat)abstract
- The relative importance of natural selection in the diversification of organisms. can be assessed indirectly using matrix correspondence. The present study determines the environmental and genetic correlates of microgeographical variation in the growth form, leaf form and flower morphology in populations of four Aeonium species from section Leuconium using partial regression methods. The phylogeny of the four species and the other 12 species in the section was deduced from amplified fragment length polymorphism (AFLP). Pubescence of floral organs and flower size correlate with the phylogeny while traits related to growth form, leaf form, flower construction and inflorescence size correlate with ecological factors. The variation in the latter four traits may therefore reflect selection by current ecological conditions while variation in pubescence and flower size may reflect historical events like neutral mutations, founder events and drift. Additionally, the morphological analyses revealed a large amount of variation in all traits within populations. This suggests a possible influence of microhabitat on the variation in morphology of Aeonium in the Canary Islands. (C) 2002 The Linnean Society of London, Biological Journal of the Linnean Society, 76, 521-533.
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| 4. |
- Lubin, Yael, et al.
(författare)
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Limited male dispersal in a social spider with extreme inbreeding
- 2009
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Ingår i: Biological Journal of the Linnean Society. - : Oxford University Press (OUP). - 0024-4066 .- 1095-8312. ; 97:2, s. 227-234
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Tidskriftsartikel (refereegranskat)abstract
- Cooperatively breeding animals commonly avoid incestuous mating through pre-mating dispersal. However, a few group-living organisms, including the social spiders, have low pre-mating dispersal, intra-colony mating, and inbreeding. This results in limited gene flow among colonies and sub-structured populations. The social spiders also exhibit female-biased sex ratios because survival benefits to large colonies favour high group productivity, which selects against 1 : 1 sex ratios. Although propagule dispersal of mated females may occasionally bring about limited gene flow, little is known about the role of male dispersal. We assessed the extent of male movement between colonies in natural populations both experimentally and by studying colony sex ratios over the mating season. We show that males frequently move to neighbouring colonies, whereas only 4% of incipient nests were visited by dispersing males. Neighbouring colonies are genetically similar and movement within colony clusters does not contribute to gene flow. Post-mating sex ratio bias was high early in the mating season due to protandry, and also in colonies at the end of the season, suggesting that males remain in the colony when mated females have dispersed. Thus, male dispersal is unlikely to facilitate gene flow between different matrilineages. This is consistent with models of non-Fisherian group-level selection for the maintenance of female biased sex ratios, which predict the elimination of male dispersal.
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| 5. |
- Malm, J U, et al.
(författare)
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Immigration history and gene dispersal: allozyme variation in Nordic populations of the red campion, Silene dioica (Caryophyllaceae)
- 2002
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Ingår i: Biological Journal of the Linnean Society. - : Oxford University Press (OUP). - 0024-4066 .- 1095-8312. ; 77:1, s. 23-34
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Tidskriftsartikel (refereegranskat)abstract
- Most of the Nordic region was ice-covered during the last (Weichselian) glaciation. During the postglacial period, plant and animal species recolonized the region from several directions and the geographic structuring of genetic variation within Nordic species may still contain a historic component that reflects patterns of postglacial immigration. The present investigation of 69 populations of Silene dioica represents the first large-scale allozyme study of a widespread herbaceous plant in the Nordic region. Although the frequencies of individual alleles showed a range of different geographic patterns, mapping of the axis scores from an ordination of variation at eight polymorphic loci revealed a division into two main geographic groups of populations. The broadly south-western and northeastern distributions of these two groups of populations suggest that immigration into the region may have involved both eastern and southern geographic sources. However, the geographic boundaries between the two groups of populations are diffuse, and the relatively low between-population component of genetic diversity (G(ST) = 16.4%) suggests a history of extensive gene dispersal by pollen. (C) 2002 The Linnean Society of London, Biological Journal of the Linnean Society, 2002, 77, 23-34.
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| 6. |
- Olofsson, Sofie, et al.
(författare)
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Genetic diversity and differentiation of allopolyploid Dactylorhiza (Orchidaceae) with particular focus on the Dactylorhiza majalis ssp traunsteineri/lapponica complex
- 2009
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Ingår i: Biological Journal of the Linnean Society. - : Oxford University Press (OUP). - 0024-4066 .- 1095-8312. ; 97:1, s. 52-67
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Tidskriftsartikel (refereegranskat)abstract
- Genetic differentiation of Dactylorhiza majalis ssp. traunsteineri from the Alps, Scandinavia, and Britain was studied and compared with other allotetraploid members of the systematically challenging genus Dactylorhiza. One-hundred and eleven populations from altogether 18 taxa were analysed for eight polymorphic plastid markers and two size-variable fragments from the nuclear internal transcribed spacer (ITS) region. In total, 60 plastid haplotypes and six ITS alleles were found among the 737 individuals analysed. No clear differentiation between populations of ssp. traunsteineri from the three regions was revealed. However, ssp. traunsteineri was genetically differentiated from Dactylorhiza baumanniana, Dactylorhiza elata, and D. majalis ssp. sphagnicola, although the majority of allotetraploid taxa remained inseparable. Judging from the degree of concerted evolution in ITS, D. majalis ssp. alpestris may be regarded as a relatively old allotetraploid, whereas ssp. baltica and ssp. purpurella may be considerably younger. Based on plastid data, the Alp region had the highest genetic diversity followed by Scandinavia and Britain. The geographic distribution of haplotypes provided support for possible refugial areas around the Alps and for several independent immigration routes into Scandinavia after the last ice age. (C) 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 52-67.
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| 7. |
- Pimentel, Carla, et al.
(författare)
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Latitudinal gradients and the shaping of life-history traits in a gregarious caterpillar
- 2010
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Ingår i: Biological Journal of the Linnean Society. - : Oxford University Press (OUP). - 0024-4066 .- 1095-8312. ; 100:1, s. 224-236
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Tidskriftsartikel (refereegranskat)abstract
- The present study aimed to investigate how the impact of several factors linked to geography would shape life-history traits in a gregarious species, using the pine processionary moth (PPM) Thaumetopoea pityocampa as a model system. PPM has a wide geographical distribution over the Mediterranean Basin, and it is a strictly gregarious species throughout larval development, where the total reproductive output of each female forms a colony. We reviewed both published and unpublished data on PPM from all over its distribution in the Mediterranean Basin and extracted data on fecundity, egg size, egg parasitoid mortality, flight period, and development time. These life-history traits were then related to location, expressed as latitude and altitude, local average temperatures, and host tree species. We found that PPM fecundity increaseed with latitude, concomitant with an increase in the length of development and an earlier onset of adult flight. These results are the opposite of that found in other Lepidoptera species with a wide geographical distribution, as well as in insects in general. We propose that a large colony size in PPM is important at higher latitudes because this confers an advantage for thermoregulation and tent building in areas where larvae have to face harsher conditions during the winter, thus shifting the optimal trade-off between the number and size of eggs with latitude. However, host tree species also affected the relationship between egg number and size and the optimal outcome of these traits is likely a compromise between different selection pressures. (C) 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 224-236.
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| 8. |
- Rao, G Y, et al.
(författare)
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Patterns of inbreeding depression in a population of Brassica cretica (Brassicaceae): evidence from family-level analyses
- 2002
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Ingår i: Biological Journal of the Linnean Society. - : Oxford University Press (OUP). - 0024-4066 .- 1095-8312. ; 76:3, s. 317-325
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Tidskriftsartikel (refereegranskat)abstract
- In this investigation, we have collected family-structured data from a partly self-compatible, outcrossing population of Brassica cretica to estimate and compare the effects of one-generation selfing on different types of characters. Inbreeding not only depressed characters that should be positively correlated with fitness irrespective of habitat, e.g. germinability, leaf number and inflorescence size, but also resulted in later flowering, smaller and more asymmetric flowers, and an increased production of basal branches. Population-level estimates of inbreeding depression were similar in magnitude to estimates reported in other wild plant species. There was a tendency for direct components of fitness to exhibit a stronger response to inbreeding than other characters, but only when the differences between selfed and outbred offspring were measured in standard deviation units. Family-level estimates of inbreeding depression were weakly correlated across characters. Given these and other observations, we hypothesize that the genetic basis of inbreeding depression varies across the life cycle and that changes in local inbreeding will lead to shifts in the mean phenotypes of B. cretica populations. However, judging from data on current levels of population divergence, quite large changes in inbreeding will be required to influence large-scale patterns of variation in this species. (C) 2002 The Linnean Society of London.
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| 9. |
- Secondi, Jean, et al.
(författare)
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Species-specific song convergence in a moving hybrid zone between two passerines
- 2003
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Ingår i: Biological Journal of the Linnean Society. - : Oxford University Press (OUP). - 0024-4066 .- 1095-8312. ; 80:3, s. 507-517
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Tidskriftsartikel (refereegranskat)abstract
- Moving hybrid zones are receiving increasing attention. However, so far little is known about the proximate mechanisms underlying these movements. Signalling behaviour, by individuals engaged in interspecific sexual and aggressive interactions, may play a crucial role. In this study, we investigated song variation within a moving hybrid zone between two warblers, Hippolais polyglotta and H. icterina. In these species, song is involved in interspecific territoriality and, probably, in mixed pairings. We showed that allopatric populations of the two species are clearly acoustically differentiated. However, interspecific differences faded out in sympatry as a result of an overall pattern of convergence. Unexpectedly, the two species converged for different song parameters, namely temporal parameters for H. icterina and syntax for H. polyglotta. Hybridization and interspecific competition could explain convergence in H. icterina. Instead, in H. polyglotta we suggest that local adaptation to habitat and interspecific learning might contribute to convergence. We particularly stress that cross-species learning, by maintaining high levels of interspecific interactions, may influence the movement of the zone. (C) 2003 The Linnean Society of London.
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| 10. |
- Van Rossum, F, et al.
(författare)
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Structure of allozyme variation in Nordic Silene nutans (Caryophyllaceae): population size, geographical position and immigration history
- 2004
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Ingår i: Biological Journal of the Linnean Society. - : Oxford University Press (OUP). - 0024-4066 .- 1095-8312. ; 81:3, s. 357-371
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Tidskriftsartikel (refereegranskat)abstract
- We investigated allozyme variation in 34 populations of the perennial herb Silene nutans from Sweden and northern Finland, areas that were ice-covered during the last (Weichselian) glaciation. The present geographical structure of genetic variation in S. nutans in Sweden and northern Finland appears to have been mainly shaped by ancient historical processes. Patterns of variation in allele frequencies suggest two major postglacial immigration routes into Sweden, with populations entering the area from both the south and the east and forming a contact zone with admixed populations in central Sweden. While estimates of within-population genetic diversity and allelic richness are significantly correlated with present population size and geographical position (latitude), population size is not correlated with latitude. Low genetic diversity in the northern populations is more likely to have resulted from ancient stochastic events during the process of immigration than from recent population fragmentation. F-IS values are high and increase with latitude. Evidence of recent bottlenecks was detected in several southern Swedish populations: these can be interpreted in terms of population fragmentation as a result of anthropogenic disturbance. Soil pH is uncorrelated with population size and position. (C) 2004 The Linnean Society of London,
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