Spatio-temporal species aggregations do not rule out interspecific competition in tree hollow spider assemblages: LAS AGREGACIONES ESPACIOTEMPORALES ENTRE ESPECIES NO DESCARTAN LA COMPETENCIA INTERESPECIFICA EN LOS ENSAMBLES DE ARANAS DE LAS OQUEDADES ARBOREAS

A community's biological diversity reflects coexistence between species. This often depends, to some extent, on whether there is competition for resources and how it is dealt with.The nature of old-growth tree hollows is confined and relatively isolated, which makes them ideal for investigating the competition phenomena between their inhabitants, such as Araneae.The existence of interspecific competition in the structuring of tree hollow spider assemblages in Mediterranean forests was inferred by spatial co-occurrence pattern analyses with null models at both the community and pairwise levels. The analysis included 36 spider species collected monthly with emergence traps for 1 year. The distribution of four ecological traits, body size and phenology on the resulting pattern type was discussed.The analyses showed spatial segregation at the community level and spatial aggregations between species with different traits predominated at the pairwise level. Hunting strategy and body size were the main differential traits to facilitate these aggregations. In addition, only the aggregations led by Amaurobius scopolii-Scotophaeus scutulatus and Eratigena atrica-Liocranum majus also showed an overlap during their main activity period.Community segregation and spatio-temporal aggregations of species with differential traits suggest that interspecific competition is a very likely structuring factor of tree hollow spider assemblages. Instead, segregations at the pairwise level seem to result from other factors, for example, habitat preferences. La diversidad biologica de una comunidad refleja la coexistencia entre especies. Esta depende a menudo de si hay competencia por los recursos.Las oquedades de los arboles anosos tienen una naturaleza confinada y relativamente aislada que las hace ideales para investigar la competencia entre sus habitantes, como el orden Araneae.La existencia de competencia interespecifica en la estructuracion de los ensambles de aranas de las oquedades arboreas en bosques mediterraneos se infirio mediante analisis de patrones de co-ocurrencia espaciales con modelos nulos a nivel de comunidad y de pares de especies. Los analisis incluyeron 36 especies colectadas mensualmente durante 1 ano con trampas de emergencia. Asimismo, se discutio la distribucion de cuatro rasgos ecologicos, tamano corporal y fenologia en los patrones resultantes.Los analisis mostraron una segregacion espacial a nivel de comunidad y una predominancia de agregaciones entre especies con diferentes rasgos a nivel de pares. La estrategia de caza y el tamano corporal fueron los principales rasgos diferenciales que facilitaban estas agregaciones. Ademas, solo las agregaciones formadas por Amaurobius scopolii-Scotophaeus scutulatus y Eratigena atrica-Liocranum majus se solapaban tambien temporalmente.La segregacion a nivel de comunidad y las agregaciones espaciotemporales de especies con rasgos diferentes sugieren que la competencia interespecifica es un factor muy probable de estructuracion de los ensambles de aranas de las oquedades arboreas. En cambio, las segregaciones a nivel de pares resultan de otros factores, como las preferencias del habitat. Abundance data reflects the reality of biological systems better than the presence/absence of data.Spatial species aggregations do not imply that interspecific competition is absent while spatial segregations do not mean that it is, considering species morphoecological traits and phenology.Interspecific competition most likely plays a role in the structuring of spider assemblages in tree hollows.image