Sobre la fundación de la sociedad en la hormiga Cataglyphis iberica (Emery, 1906) (Hymenoptera, Formicidae)

Colony founding in Cataglyphis iberica, a monogynous and polydomous ant species, has been studied. Nest population, worker size distribution and queeníworker dimorphism has been analyzed. Males and virgin females are found only in queenless nests. Virgin females have a relatively small fat content (36+8%) and after mating, they fly and go away from their original nest. Solitary mated queens are usually found in the field, but they never reach to found new societies in laboratory conditions. The contribution of these results to clarify the colony founding process, and the relationships between this process and polydomy phenomenon is discussed.Se ha estudiado el modo de fundación de la sociedad en la hormiga Cataglyphis iberica, especie monogínica y policálica. Se ha analizado la población de 10s nidos, la biometria de las obreras y el dimorfisme reina/obrera. Los sexuados se encuentran únicamente en 10s nidos sin reina de las colonias. Las hembras vírgenes tienen un contenido relativamente bajo en lípidos (36f 8%). Tras la cópula (siempre en el suelo: carrera nupcial) las hembras emprenden el vuelo y se alejan del nido madre. Se encuentran hembras solitarias y fecundadas por el campo, pero instaladas en el laboratorio mueren sin descendencia. Se discute la aportación de estos resultados en favor de 10s diversos tipos posibles de fundación, y su relación con la policalia

Socioeconomics explain tree diversity, abundance, and composition in the compact city of Barcelona, Spain

Altres ajuts: acords transformatius de la UABTrees are frequently unevenly distributed in urban areas, and their diversity, abundance, and composition vary spatially. Some studies have shown that the unequal distribution of urban trees can be associated with demographic and socioeconomic factors. However, most studies have been conducted in diffuse urban systems using remotely-sensed tree cover within single or aggregated land-use types. We examined if the relationship between tree diversity, abundance, composition, and socioeconomic factors varied across land-use types (parks, streets, zonal areas, and total) in the compact city of Barcelona, Spain. We calculated tree species richness and abundance across 73 neighborhoods using 229,962 geo-referenced records of individual trees sampled in 2021. Life expectancy positively explained tree richness and abundance across land-use types, reinforcing that access to urban green infrastructure promotes longer life spans. In contrast, income did not positively explain tree richness or abundance, indicating that tree distribution does not directly result in biodiversity and green space inequalities for disadvantaged groups in terms of income. Total tree composition across neighborhoods responded to socioeconomic gradients, evidencing that neighborhood appearances are socially stratified. Street tree abundance increased in densely populated neighborhoods, possibly because intense street tree plantings in these neighborhoods compensate for the lack of other green infrastructure. Urban tree planting, particularly in streets, can be an effective strategy to increase green spaces in compact cities to overcome the disparities resulting from the unequal distribution of urban vegetation. Long-term data on socioeconomic factors and urban tree distribution are necessary to determine how social stratification affects urban diversity

Edge influence on diversity of orchids in Andean cloud forests

Cloud forests harbor high levels of orchid diversity. However, due to the high fragmentation of these forests in the Andes, combined with the pressure for new agricultural land, orchid diversity is highly threatened. Despite this worrying scenario, few studies have assessed the effects of habitat loss specifically on orchid assemblages in the Andes. The aim of this study was to analyze the edge effect on orchids in cloud forest fragments of varying size. We measured forest structure, neighboring land cover and edge effect on orchid abundance, species richness and beta-diversity, by sampling assemblages along edge-to-interior transects in six different sized Andean (southwest Colombia) forest remnants. We recorded 11,127 stem-individuals of orchids in 141 species. Within the forest, edges sustained equal or more species than interior plots. Our results revealed neither patch metrics nor forest structure showed any significant association to orchid diversity at any scale. Nonetheless, from our observations in composition, the type of neighboring cover, particularly pastures, negatively influences interior species (richness and composition) in larger reserves. This might be due to the fact that some species found in interior plots tend to be confined, with sporadic appearances in regeneration forest and are very scarce or absent in pastures. Species richness differed significantly between matrix types. Our results suggest that (1) orchid diversity shows spatial variability in response to disturbances, but the response is independent from forest structure, patch size and patch geometry; (2) orchid communities are negatively affected by covers, and this pattern is reflected in reduced richness and high species turnover; (3) orchid richness edge effect across a pasture-interior gradient. Two forest management implications can be discerned from our results: (1) management strategies aiming to reduce edge effects may focus on improvement regeneration conditions around pasture lands; and (2) local scale management and conservation activities of natural forests in cloud forests will favor small reserves that harbor high levels of richness

És homogènia la recuperació, després del foc, de les comunitats de plantes i de formigues dels boscos de Catalunya?

Es presenten les principals conclusions de diversos estudis amb l'objectiu d'avaluar la resiliència dels boscos de Catalunya després d'un incendi. Es mostra que hi ha un ventall ampli de respostes, que inclou boscos amb una alta resiliència al foc i que recuperen ràpidament l'espècie o espècies arbòries dominants, però també altres boscos en què l'espècie dominant abans del foc no es recupera i són substituïts per altres formacions boscoses o arbustives. La substitució de les espècies dominants i estructuradores del bosc comporta que tota la comunitat de plantes i de formigues que hi viuen tinguin menor resiliència al foc que les dels boscos que mantenen les mateixes espècies dominants d'abans del foc. Aquests resultats impliquen repensar algunes idees sobre les possibles conseqüències dels focs sobre la biodiversitat i quins han de ser els objectius de la gestió de determinades zones cremades.¿Es homogénea la recuperación, tras el incendio, de las comunidades de plantas y de hormigas de los bosques de Cataluña? Se presentan las principales conclusiones de diversos estudios con el objetivo de evaluar la resiliencia de los bosques de Cataluña después de un incendio. Se muestra que existe un amplio abanico de respuestas, que incluye bosques con una alta resiliencia al fuego y que recuperan rápidamente la especie o especies arbóreas dominantes, pero también otros bosques donde la especie dominante no se recupera y son sustituidos por otras formaciones boscosas o arbustivas. La sustitución de estas especies dominantes y estructurantes del bosque supone que toda la comunidad de plantas y de hormigas que viven tengan menor resiliencia al fuego que las de los bosques que mantienen las mismas especies dominantes antes del fuego. Estos resultados implican replantear algunas ideas sobre las posibles consecuencias de los fuegos sobre la biodiversidad y cuáles deben ser los objetivos de gestión de determinadas zonas quemadas.Is homogeneous the postfire recovery of plant and ant communities in Catalan forests? We presents the main conclusions of different studies to analyze the forest resilience in Catalonia after fire. It shows how there is a sufficiently broad range of responses, which include forests with high resilience to fire and quickly recover the species or dominant tree species, but also other forests where before fire, the dominant species are not recovered and then, are replaced by other types of woodland and shrubs. In these cases, the replacement of dominant species and forest structure means that the whole community of plants and ants that live in these forests have less resilience to fire than forests that maintain the same dominant species before fire. These results imply think about the possible consequences of fires on biodiversity and also what should be the objectives of management of certain areas burned

Estrategias alternativas en el ciclo de vida de tres hormigas mediterráneas

Se ha estudiado el ciclo biológico de tres especies de hormigas mediterráneas, y se han constatado importantes diferencias entre ellas. Cataglyphis cursor hibema sin descendencia y completa un ciclo de nidada entre los meses de abril y septiembre. Aphaenogaster senilis hibema sin nidada y produce pupas durante un amplio periodo de tiempo, desde abril hasta octubre, aunque los valores mtiximos (que coinciden con el pico de actividad exterior) se dan en primavera y principio de verano. Ambas especies fundan la sociedad por fisión colonial, por lo que la descendencia obrera es la que condiciona decisivamente el ciclo de vida de las colonias. En cambio, Camponotus cruentatus funda la sociedad de manera independiente, por lo que debe producir un elevado número de sexuados que contrarresten la elevada mortalidad que tiene lugar durante el apareamiento. Su ciclo difiere de los anteriores en que hay una importante producción primaveral de sexuados y de obreras, que se solapan en el tiempo en el interior de los nidos. Las variaciones en los ciclos de vida de las tres especies se discuten en relación con la actividad estacional y las características ecológicas de cada una de ellas.Colony life cycles of three mediterranean ants have been analyzed, and important differences have been found among them. Cataglyphis cursor does not keep brood during the winter, and rears new individuals from egg to adult in only one activity period, from April to September. Aphaenogaster senilis spends the winter with brood, and produces new workers during a long period of the year, from April to October. Both species produce a small number of alates because they form new colonies by fission. Therefore, worker brood is the decisive factor that determines colony life cycles of both species. Camponotus cruentatus has an independent mode of colony founding, in which colonies produce a high number of alates in order to override the extremely high mortality of colony-founding queens during mating. Its colony cycle differs from the others in that there is a high spring production of alates and workers, which overlap into the nests. Variations in colony life cycles of these species in relationship with their seasonal activity pattem and their ecological features are discussed

Intraspecific variability in functional traits matters : case study of Scots pine

Although intraspecific trait variability is an important component of species ecological plasticity and niche breadth, its implications for community and functional ecology have not been thoroughly explored. We characterized the intraspecific functional trait variability of Scots pine (Pinus sylvestris) in Catalonia (NE Spain) in order to (1) compare it to the interspecific trait variability of trees in the same region, (2) explore the relationships among functional traits and the relationships between them and stand and climatic variables, and (3) study the role of functional trait variability as a determinant of radial growth. We considered five traits: wood density (WD), maximum tree height (H max), leaf nitrogen content (Nmass), specific leaf area (SLA), and leaf biomass-to-sapwood area ratio (B L:A S). A unique dataset was obtained from the Ecological and Forest Inventory of Catalonia (IEFC), including data from 406 plots. Intraspecific trait variation was substantial for all traits, with coefficients of variation ranging between 8% for WD and 24% for B L:A S. In some cases, correlations among functional traits differed from those reported across species (e.g., H max and WD were positively related, whereas SLA and Nmass were uncorrelated). Overall, our model accounted for 47% of the spatial variability in Scots pine radial growth. Our study emphasizes the hierarchy of factors that determine intraspecific variations in functional traits in Scots pine and their strong association with spatial variability in radial growth. We claim that intraspecific trait variation is an important determinant of responses of plants to changes in climate and other environmental factors, and should be included in predictive models of vegetation dynamics

Regeneration patterns in Mexican pine-oak forests

Altres ajuts: ICREA AcademiaBackground: Global change is causing an increase in the incidence of natural and anthropogenic disturbances on forests, which frequently interact synergistically and promote changes in forest structure, composition and functioning. In this study we evaluate the regeneration of Pinaceae and Fagaceae species in pure and mixed stands in Mexico to determine if current regeneration patterns are indicative of changes in the relative dominance of these two tree families, as observed in other temperate regions. We also identify the environmental factors that determine the regeneration patterns of Pinaceae and Fagaceae species in these forests. Results: We use data from two consecutive surveys of the National Inventory of Forests and Soils of Mexico (INFyS), obtained in 2004-2009 and 2009-2014. Our results show that the spatial patterns of regeneration are affected by forest structure, by climate, by the type and intensity of disturbances and by land tenure. Importantly, the presence and abundance of Fagaceae regeneration is generally higher than that of Pinaceae, and tends to be favoured (relative to Pinaceae) under warmer climates and by the presence of wildfires. Conclusions: The higher regeneration of Fagaceae relative to Pinaceae under warmer and fire-prone conditions could have important impacts on the composition and functioning of Mexican temperate forests under ongoing climate change, as well as affect their resilience to future disturbances

Pollinators show flower colour preferences but flowers with similar colours do not attract similar pollinators

Background and aims: colour is one of the main floral traits used by pollinators to locate flowers. Although pollinators show innate colour preferences, the view that the colour of a flower may be considered an important predictor of its main pollinators is highly controversial because flower choice is highly context-dependent, and initial innate preferences may be overridden by subsequent associative learning. Our objective is to establish whether there is a relationship between flower colour and pollinator composition in natural communities. - Methods: we measured the flower reflectance spectrum and pollinator composition in four plant communities (85 plant species represented by 109 populations, and 32 305 plant-pollinator interactions in total). Pollinators were divided into six taxonomic groups: bees, ants, wasps, coleopterans, dipterans and lepidopterans. - Key results: we found consistent associations between pollinator groups and certain colours. These associations matched innate preferences experimentally established for several pollinators and predictions of the pollination syndrome theory. However, flowers with similar colours did not attract similar pollinator assemblages. - Conclusions: the explanation for this paradoxical result is that most flower species are pollination generalists. We conclude that although pollinator colour preferences seem to condition plant-pollinator interactions, the selective force behind these preferences has not been strong enough to mediate the appearance and maintenance of tight colour-based plant-pollinator associations

Identificación de los anillos anuales de crecimiento de la encina (Quercus ilex. L.)

Las caracteristicas de la madera de encina (Quercus ilex L.) hacen de muy difícil interpretación el patrón de crecimiento anual de esta especie. Con el fin de intentar encontrar un método práctico y, al mismo tiempo, fiable para la identificación de los anillos anuales de crecimiento de la encina, se han seguido dos aproximaciones: el estudio de discos enteros de troncos y el de testigos de madera recogidos con barrena Pressler. La utilización de discos plantea dos problemas: por una parte se destruyen los individuos muestreados y, por otra, con ninguno de los métodos de preparación de la madera (pulido o corte transversal) se aprecian de manera clara los vasos conductores, que son la caracteristica más clara para identificar los distintos anillos. Los testigos de madera tienen la ventaja de que su manipulación es sencilla y que aseguran la supervivencia de los árboles muestreados. Sin embargo, en los tradicionales testigos de 5 mm de diámetro, la presencia de radios medulares que atraviesan la muestra impide la delimitación de los anillos de crecimiento. Este problema se soluciona con la utilización de testigos de madera de 12 mm de diámetro que, una vez cortados, perrmiten mostrar claramente el patrón de vasos. A partir de los datos obtenidos con muestras de encina de edad conocida pertenecientes a rebrotes muestreados en zonas cortadas o quemadas, se constata que la diferencia entre el número de años y el número de anillos identificados en los testigos de madera es, como máximo, de dos o tres. Esto hace que el método propuesto pueda ser utilizado de manera fiable en el estudio de la edad y del crecimiento de esta especie.The growth pattem of the holm oak (Quercus ilex L.) is difficult to interpret due to varied features of its wood. In order to find a practical as well as reliable method for interpreting annual tree-rings of the holm oak, two approaches have been tried: the study of basal disks and the study of 5 mm-diarneter, and 12 mm-diameter cores taken with a Pressler borer. We do not recommend the use of disks because the sampled individuals are destroyed during collection, and because with none of the methods used for treating wood (polishing and cutting) is it possible to show the vessels, which are the clearest form of identifying different tree-rings. Cores are easily manipulated and allow the survival of sampled trees; nevertheless, the traditional 5 mm-diameter cores are not adequate because holm oak wood is crossed by many wood rays, which prevent the definition of tree-ring limits. This problem has been solved using 12 mm-diameter which, after cutting, clearly show the vessel pattem. By means of dated samples of holm oak wood it has been possible to establish that the number of annual growth rings and the number of years differ in fewer than two or three units. The high correlation between both variables makes the propossed method highly efficient for interpreting age and growth patterns of the holm oak

Changing patterns of fire occurrence in proximity to forest edges, roads and rivers between NW Amazonian countries

Tropical forests in NW Amazonia are highly threatened by the expansion of the agricultural frontier and subsequent deforestation. Fire is used, both directly and indirectly, in Brazilian Amazonia to propagate deforestation and increase forest accessibility. Forest fragmentation, a measure of forest degradation, is also attributed to fire occurrence in the tropics. However, outside the Brazilian Legal Amazonia the role of fire in increasing accessibility and forest fragmentation is less explored. In this study, we compared fire regimes in five countries that share this tropical biome in the most north-westerly part of the Amazon Basin (Venezuela, Colombia, Ecuador, Peru and Brazil). We analysed spatial differences in the timing of peak fire activity and in relation to proximity to roads and rivers using 12 years of MODIS active fire detections. We also distinguished patterns of fire in relation to forest fragmentation by analysing fire distance to the forest edge as a measure of fragmentation for each country. We found significant hemispheric differences in peak fire occurrence with the highest number of fires in the south in 2005 vs. 2007 in the north. Despite this, both hemispheres are equally affected by fire. We also found difference in peak fire occurrence by country. Fire peaked in February in Colombia and Venezuela, whereas it peaked in September in Brazil and Peru, and finally Ecuador presented two fire peaks in January and October. We confirmed the relationship between fires and forest fragmentation for all countries and also found significant differences in the distance between the fire and the forest edge for each country. Fires were associated with roads and rivers in most countries. These results can inform land use planning at the regional, national and subnational scales to minimize the contribution of road expansion and subsequent access to the Amazonian natural resources to fire occurrence and the associated deforestation and carbon emissions