Relaciones culturales filipino-persas (I): las Rubaiyat de Manuel Bernabé

Life history trade-offs are a key notion in evolutionary biology, notably for understanding how selection shapes the diversity of traits among species. Despite the frequent study of such trade-offs, few studies synchronously investigate the effects of multiple factors, such as niche specialization and adaptation to harsh environments. We compared reproduction (fecundity and egg quality) in two sympatric couples (one habitat generalist and one specialist) of congeneric wolf spider species, in both Arctic and temperate habitats. We found that specialist species at both latitudes invested more in clutch size than did generalist species. We interpret this result as an optimization of clutch production. In the Arctic, the specialist was able to invest in fecundity with increasing body size at a much higher rate than the generalist species. In the temperate habitat, both species showed similar strategies: they increased quantity and quality of offspring relative to body size at the same rate. These results are consistent with the hypothesis that Arctic species must develop distinct strategies in order not to overlap each other’s ecological niches as a consequence of limited food resources or niche space. We emphasize the need to test the role of plasticity and environmentally mediated effects of competition on arthropod fitness

Influence of individual density and habitat availability on long-distance dispersal in a salt-marsh spider

International audienceDispersal is a key process in metapopulation dynamics and metacommunity assembly as it may be affected by a variety of factors acting at different spatial scales. While dispersal is known to evolve in response to landscape-related selection pressures, local dynamics are merely driven by conditional responses, for instance by habitat quality and density. Local and regional factors are thus expected to impact dispersal, either synergistically or antagonistically. Moreover, such responses do not need to coincide among all life stages because different life stages are expected to incur different costs, either intrinsically due to for instance differences in size or extrinsically because of demographic changes. Our general objective is consequently to test for the likely opposite effects of main factors acting on dispersal, i.e. local density and habitat configuration, at different life-stages in a salt marsh inhabiting spider Pardosa purbeckensis (F.O.P.-Cambridge 1895). Using a combination of both field and laboratory experiments on pre-dispersal behaviour, we demonstrate a significant negative density-dependence for natal dispersal, but no alike effect at the adult stage. No effects of the local habitat structure were detected. Therefore, good mother body condition could be interpreted by juveniles during the phase of maternal care as suitable living conditions, decreasing emigration rate. Although dispersal is known to have a genetic basis, local factors eventually overrule this source of variation

Chronic exposure to soil salinity in terrestrial species: Does plasticity and underlying physiology differ among specialized ground-dwelling spiders?

International audienceIn salt marshes, the alternation of low and high tides entails rapid shifts of submersion and aerial exposure for terrestrial communities. In these intertidal environments, terrestrial species have to deal with an osmotic loss in body water content and an increase in sodium chloride concentration when salt load increases. In salt marshes, spiders represent an abundant arthropod group, whose physiological ecology in response to variations of soil salinity must be further investigated. In this study, we compared the effect of salinity on the survival and physiology of three species of Lycosidae; two salt marsh species (Arctosa fulvolineata and Pardosa purbeckensis) and one forest species (P. saltans). Spiders were individually exposed at three salinity conditions (0‰, 35‰ and 70‰) and survival, changes in body water content, hemolymph ions (Na+, Ca2+, Mg2+, K+; ICP-MS technique) and metabolites (mainly amino acids, polyols, sugars; LC and GC techniques) were assessed. The survival of the forest species P. saltans was very quickly hampered at moderate and high salinities. In this spider, variations of hemolymph ions and metabolites revealed a quick loss of physiological homeostasis and a rapid salt-induced dehydration of the specimens. Conversely, high survival durations were measured in the two salt-marsh spiders, and more particularly in A. fulvolineata. In both P. purbeckensis and A. fulvolineata, the proportion of Na+, Ca2+, Mg2+, K+ remained constant at the three experimental conditions. Accumulation of hemolymph Na+ and amino acids (mainly glutamine and proline) demonstrated stronger osmoregulatory capacities in these salt-marsh resident spiders. To conclude, even if phylogenetically close (belonging to the same, monophyletic, family), we found different physiological capacities to cope with salt load among the three tested spider species. Nevertheless, physiological responses to salinity were highly consistent with the realized ecological niches of the spiders. © 2016 Elsevier Ltd

Habitat specialization and climate affect arthropod fitness: a comparison of generalist vs. specialist spider species in Arctic and temperate biomes

Life history trade-offs are a key notion in evolutionary biology, notably for understanding how selection shapes the diversity of traits among species. Despite the frequent study of such trade-offs, few studies synchronously investigate the effects of multiple factors, such as niche specialization and adaptation to harsh environments. We compared reproduction (fecundity and egg quality) in two sympatric couples (one habitat generalist and one specialist) of congeneric wolf spider species, in both Arctic and temperate habitats. We found that specialist species at both latitudes invested more in clutch size than did generalist species. We interpret this result as an optimization of clutch production. In the Arctic, the specialist was able to invest in fecundity with increasing body size at a much higher rate than the generalist species. In the temperate habitat, both species showed similar strategies: they increased quantity and quality of offspring relative to body size at the same rate. These results are consistent with the hypothesis that Arctic species must develop distinct strategies in order not to overlap each other's ecological niches as a consequence of limited food resources or niche space. We emphasize the need to test the role of plasticity and environmentally mediated effects of competition on arthropod fitness

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data_Ameline_etal_2017_BJL

Elevational variation of body size and reproductive traits in high-latitude wolf spiders (Araneae Lycosidae)

International audienceEnvironmental gradients can help us comprehend the range of adaptations or plasticity that a given species can exhibit in response to climatic change. In this study, we assessed the response in female body size, clutch size and egg volume to elevational gradients in closely related wolf spiders. We measured these traits in Pardosa glacialis, P. hyperborea, P. furcifera and P. palustris, collected along elevational gradients across six sites in Arctic and sub-Arctic regions (four sites in Greenland, one in Iceland and one in the Faroe Islands), although not all species were found at all sites. Body size and reproductive traits did not vary with elevation in a consistent manner among species although smaller species were more sensitive to the gradients. The positive relationship between body size and clutch size was most pronounced in the larger species, indicating that larger species are better able to translate favourable environmental conditions into a larger reproductive output. Our study illustrates that elevational gradients may not fully capture spatial variation in environmental conditions experienced by high-latitude wolf spider species