Carnicer J., Stefanescu C., Vives-Ingla M., López C., Cortizas S., Wheat C., Vila R., Llusià J., Peñuelas J. (2019) Phenotypic biomarkers of climatic impacts on declining insect populations: A key role for decadal drought, thermal buffering and amplification effects and host plant dynamics. Journal of Animal Ecology. : 0-0.EnllaçDoi: 10.1111/1365-2656.12933
Widespread population declines have been reported for diverse Mediterranean butterflies over the last three decades, and have been significantly associated with increased global change impacts. The specific landscape and climatic drivers of these declines remain uncertain for most declining species. Here, we analyse whether plastic phenotypic traits of a model butterfly species (Pieris napi) perform as reliable biomarkers of vulnerability to extreme temperature impacts in natural populations, showing contrasting trends in thermally exposed and thermally buffered populations. We also examine whether improved descriptions of thermal exposure of insect populations can be achieved by combining multiple information sources (i.e., integrating measurements of habitat thermal buffering, habitat thermal amplification, host plant transpiration, and experimental assessments of thermal death time (TDT), thermal avoidance behaviour (TAB) and thermally induced trait plasticity). These integrative analyses are conducted in two demographically declining and two non-declining populations of P. napi. The results show that plastic phenotypic traits (butterfly body mass and wing size) are reliable biomarkers of population vulnerability to extreme thermal conditions. Butterfly wing size is strongly reduced only in thermally exposed populations during summer drought periods. Laboratory rearing of these populations documented reduced wing size due to significant negative effects of increased temperatures affecting larval growth. We conclude that these thermal biomarkers are indicative of the population vulnerability to increasing global warming impacts, showing contrasting trends in thermally exposed and buffered populations. Thermal effects in host plant microsites significantly differ between populations, with stressful thermal conditions only effectively ameliorated in mid-elevation populations. In lowland populations, we observe a sixfold reduction in vegetation thermal buffering effects, and larval growth occurs in these populations at significantly higher temperatures. Lowland populations show reduced host plant quality (C/N ratio), reduced leaf transpiration rates and complete above-ground plant senescence during the peak of summer drought. Amplified host plant temperatures are observed in open microsites, reaching thermal thresholds that can affect larval survival. Overall, our results suggest that butterfly population vulnerability to long-term drought periods is associated with multiple co-occurring and interrelated ecological factors, including limited vegetation thermal buffering effects at lowland sites, significant drought impacts on host plant transpiration and amplified leaf surface temperature, as well as reduced leaf quality linked to the seasonal advance of plant phenology. Our results also identify multiannual summer droughts affecting larval growing periods as a key driver of the recently reported butterfly population declines in the Mediterranean biome. © 2018 The Authors. Journal of Animal Ecology © 2018 British Ecological Society
Carnicer J., Sardans J., Stefanescu C., Ubach A., Bartons M., Asensio D., Penuelas J. (2014) Global biodiversity, stoichiometry and ecosystem function responses to human-induced C-N-P imbalances. Journal of Plant Physiology. : 0-0.EnllaçDoi: 10.1016/j.jplph.2014.07.022
Global change analyses usually consider biodiversity as a global asset that needs to be preserved. Biodiversity is frequently analysed mainly as a response variable affected by diverse environmental drivers. However, recent studies highlight that gradients of biodiversity are associated with gradual changes in the distribution of key dominant functional groups characterized by distinctive traits and stoichiometry, which in turn often define the rates of ecosystem processes and nutrient cycling. Moreover, pervasive links have been reported between biodiversity, food web structure, ecosystem function and species stoichiometry. Here we review current global stoichiometric gradients and how future distributional shifts in key functional groups may in turn influence basic ecosystem functions (production, nutrient cycling, decomposition) and therefore could exert a feedback effect on stoichiometric gradients. The C-N-P stoichiometry of most primary producers (phytoplankton, algae, plants) has been linked to functional trait continua (i.e. to major axes of phenotypic variation observed in inter-specific analyses of multiple traits). In contrast, the C-N-P stoichiometry of higher-level consumers remains less precisely quantified in many taxonomic groups. We show that significant links are observed between trait continua across trophic levels. In spite of recent advances, the future reciprocal feedbacks between key functional groups, biodiversity and ecosystem functions remain largely uncertain. The reported evidence, however, highlights the key role of stoichiometric traits and suggests the need of a progressive shift towards an ecosystemic and stoichiometric perspective in global biodiversity analyses.
Carnicer J., Stefanescu C., Vila R., Dincǎ V., Font X., Peñuelas J. (2013) A unified framework for diversity gradients: The adaptive trait continuum. Global Ecology and Biogeography. 22: 6-18.EnllaçDoi: 10.1111/j.1466-8238.2012.00762.x
Aim Adaptive trait continua are axes of covariation observed in multivariate trait data for a given taxonomic group. These continua quantify and summarize life-history variation at the inter-specific level in multi-specific assemblages. Here we examine whether trait continua can provide a useful framework to link life-history variation with demographic and evolutionary processes in species richness gradients. Taking an altitudinal species richness gradient for Mediterranean butterflies as a study case, we examined a suite of traits (larval diet breadth, adult phenology, dispersal capacity and wing length) and species-specific habitat measures (temperature and aridity breadth). We tested whether traits and species-specific habitat measures tend to co-vary, whether they are phylogenetically conserved, and whether they are able to explain species distributions and spatial genetic variation in a large number of butterfly assemblages. Location Catalonia, Spain. Methods We formulated predictions associated with species richness gradients and adaptive trait continua. We applied principal components analyses (PCAs), structural equation modelling and phylogenetic generalized least squares models. Results We found that traits and species-specific habitat measures covaried along a main PCA axis, ranging from multivoltine trophic generalists with high dispersal capacity to univoltine (i.e. one generation per year), trophic specialist species with low dispersal capacity. This trait continuum was closely associated with the observed distributions along the altitudinal gradient and predicted inter-specific differences in patterns of spatial genetic variability (FST and genetic distances), population responses to the impacts of global change and local turnover dynamics. Main conclusions The adaptive trait continuum of Mediterranean butterflies provides an integrative and mechanistic framework to: (1) analyse geographical gradients in species richness, (2) explain inter-specific differences in population abundances, spatial distributions and demographic trends, (3) explain inter-specific differences in patterns of genetic variation (FST and genetic distances), and (4) study specialist-generalist life-history transitions frequently involved in butterfly diversification processes. © 2012 Blackwell Publishing Ltd.
Carnicer J., Brotons L., Stefanescu C., Peñuelas J. (2012) Biogeography of species richness gradients: Linking adaptive traits, demography and diversification. Biological Reviews. 87: 457-479.EnllaçDoi: 10.1111/j.1469-185X.2011.00210.x
Here we review how adaptive traits contribute to the emergence and maintenance of species richness gradients through their influence on demographic and diversification processes. We start by reviewing how demographic dynamics change along species richness gradients. Empirical studies show that geographical clines in population parameters and measures of demographic variability are frequent along latitudinal and altitudinal gradients. Demographic variability often increases at the extremes of regional species richness gradients and contributes to shape these gradients. Available studies suggest that adaptive traits significantly influence demographic dynamics, and set the limits of species distributions. Traits related to thermal tolerance, resource use, phenology and dispersal seem to play a significant role. For many traits affecting demography and/or diversification processes, complex mechanistic approaches linking genotype, phenotype and fitness are becoming progressively available. In several taxa, species can be distributed along adaptive trait continuums, i.e. a main axis accounting for the bulk of inter-specific variation in some correlated adaptive traits. It is shown that adaptive trait continuums can provide useful mechanistic frameworks to explain demographic dynamics and diversification in species richness gradients. Finally, we review the existence of sequences of adaptive traits in phylogenies, the interactions of adaptive traits and community context, the clinal variation of traits across geographical gradients, and the role of adaptive traits in determining the history of dispersal and diversification of clades. Overall, we show that the study of demographic and evolutionary mechanisms that shape species richness gradients clearly requires the explicit consideration of adaptive traits. To conclude, future research lines and trends in the field are briefly outlined. © 2011 The Authors. Biological Reviews © 2011 Cambridge Philosophical Society.
Peñuelas J, Filella I, Estiarte M, Ogaya R, Llusià J, Sardans J, Jump A, Curiel J, Carnicer J, Rutishauser T, Rico L, Keenan T, Garbulsky M, Coll M, Diaz de Quijano M, Seco R, Rivas-Ubach A, Silva J, Boada M, Stefanescu C, Lloret F, Terradas J (2011) Llebot E. (ed). Impactes, vulnerabilitat i retroalimentacions climàtiques als ecosistemes terrestres catalans. Segon informe sobre el canvi climàtic a Catalunya. Institut d'Estudis Catalans i Generalitat de Catalunya. Barcelona, pp. 373-407.
Stefanescu C., Carnicer J., Peñuelas J. (2011) Determinants of species richness in generalist and specialist Mediterranean butterflies: The negative synergistic forces of climate and habitat change. Ecography. 34: 353-363.EnllaçDoi: 10.1111/j.1600-0587.2010.06264.x
Although it is well established that butterfly richness is affected by climate and human factors (e.g. habitat disturbance and degradation) at different spatial scales, the drivers behind these changes vary greatly according to the geographical region and the ecology of the species concerned. It is essential that this variation be understood if trends in diversity are to be predicted with any degree of confidence under a scenario of global change. Here we examine patterns of butterfly species richness among groups differing in degree of habitat specialization, diet breadth and mobility in the north-west Mediterranean Basin, a European hotspot for this taxon. We analyze a large number of butterfly communities and take into consideration the main potential drivers, that include climatic, geographic and resource variables, landscape structure and human environmental impact at different spatial scales. Our study shows that both climatic and anthropogenic factors play an important role in determining butterfly species richness in the north-west Mediterranean Basin, but that their relative impact differs between specialist and generalist groups. At lower altitudes, water availability, a product of the interplay between temperature and rainfall, and negative effects of temperature appear as the most determinant factors. Maximum diversity was observed at mid-altitudes, which reveals the importance from a conservation point of view of Mediterranean mountain ranges. The results suggest serious population declines in specialist species restricted to mountain areas as a result of climate warming in combination with habitat loss caused by the abandonment of grazing and mowing. They also suggest negative trends for generalist species due to an increase in aridity in combination with an increase in intensification of human land use in lowland areas. Such synergies are expected to lead to rapid declines in Mediterranean butterfly populations in the coming years, thereby posing a severe threat for the conservation of European biodiversity. © 2011 The Authors. Ecography © 2011 Ecography.
Peñuelas J, Filella I, Estiarte M, Ogaya R, Llusià J, Sardans J, Jump A, Curiel J, Carnicer J, Rutishauser T, Rico L, Keenan T, Garbulsky M, Coll M, Díaz de Quijano M, Seco R, Rivas-Ubach A, Silva J, Boada M, Stefanescu C, Lloret F, Terradas J (2010) Impactes, vulnerabilitat i retroalimentacions climàtiques als ecosistemes terrestres catalans. A: Llebot E. (ed). Segon informe sobre el canvi climàtic a Catalunya. Institut d'Estudis Catalans i Generalitat de Catalunya. pp. 373-407.
Peñuelas J, Filella I, Estiarte M, Ogaya R, Llusiè J, Sardans J, Jump A, Garbulsky M, Coll M, Díaz de Quijano M, Seco R, Blanch JS, Owen S, Curiel J, Carnicer J, Boada M, Stefanescu C, Lloret F, TerradasJ (2009) Constatacions biològiques del canvi climàtic a Catalunya. A “Aigua i canvi climàtic: Diagnosi dels impactes previstos a Catalunya” Generalitat de Catalunya, Departament de Medi Ambient i Habitatge, Agencia Catalana de l’Aigua, www.gencat.cat/aca .
Stefanescu C., Peñuelas J., Filella I. (2009) Rapid changes in butterfly communities following the abandonment of grasslands: A case study. Insect Conservation and Diversity. 2: 261-269.EnllaçDoi: 10.1111/j.1752-4598.2009.00063.x
1. Abandonment of grasslands is a major threat for the conservation of biodiversity in Europe. The response of butterflies towards secondary succession has been studied in northern temperate grasslands, but always by comparing sites at different stages. 2. Here, we present a trajectory study based on the monitoring of butterflies from a series of abandoned grasslands in northeast Spain. One additional meadow was traditionally managed for the whole 8-year sampling period and provided a useful control. Both general changes at the community level and species population trends were documented through standardised transect counts. 3. The increase in turf height was neither accompanied by an increase in butterfly diversity nor by consistent trends in body size, dispersal ability and host-plant specialization. However, there was a significant decrease in habitat specialization, consistent with the hypothesis that richness in generalist herbivores is more dependent on biomass production than on plant richness. The number of generations decreased, in line with the hypothesis that species living in habitats subjected to greater disturbance need higher reproductive rates. 4. Butterfly communities underwent substantial changes, as indicated by composition similarity and species population trends. Grassland specialists were forced to disperse from the abandoned meadows and search for refugial habitats, allowing the establishment of new populations in the contiguous managed meadow. 5. Our study shows that grassland abandonment had immediate strong effects on butterflies, acting as an excellent indicator of habitat change. It also points out to the substitution of grassland specialists by common butterflies, less important for conservation purposes. © 2009 The Royal Entomological Society.
Peñuelas J, Filella I, Estiarte M, Ogaya R, Llusià J, Sardans J, Jump A, Garbulsky M, Carrillo B, Stefanescu C, Lloret F, Terradas J (2008) El canvi climàtic altera i alterarà la vida als ecosistemes terrestres Catalans. L'Atzavara 16: 13-28.
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