A mechanistic model of connector hubs, modularity, and cognition

The human brain network is modular--comprised of communities of tightly interconnected nodes. This network contains local hubs, which have many connections within their own communities, and connector hubs, which have connections diversely distributed across communities. A mechanistic understanding of these hubs and how they support cognition has not been demonstrated. Here, we leveraged individual differences in hub connectivity and cognition. We show that a model of hub connectivity accurately predicts the cognitive performance of 476 individuals in four distinct tasks. Moreover, there is a general optimal network structure for cognitive performance--individuals with diversely connected hubs and consequent modular brain networks exhibit increased cognitive performance, regardless of the task. Critically, we find evidence consistent with a mechanistic model in which connector hubs tune the connectivity of their neighbors to be more modular while allowing for task appropriate information integration across communities, which increases global modularity and cognitive performance

Predation by a Marsh Harrier (Circus aeruginosus) on Yellow-legged Gull (Larus michahellis) nests

Es descriu la predació que va realitzar una femella adulta d'arpella en tres nius de gavià argentat al delta de l'Ebre. L'observació es va fer el 4 d'abril de 2002 en un dels dics que separen dos escalfadors de les salines de la Trinitat, a la Punta de la Banya. En aquesta zona els gavians nidifiquen de manera dispersa entre els matolls de salicòrnia. Durant quaranta minuts d'observació l'arpella va recórrer una distància de 700 metres i va baixar tres cops a terra. En cada lloc on va baixar es va localitzar un niu de gavià. Tant el primer niu com el tercer contenien un ou cadascun i van ser predats per l'arpella. Tots dos ous es trobaven en la fase inicial de desenvolupament de l'embrió. El segon niu contenia dos ous, però no van ser predats, tot i que un d'ells va resultar esquerdat. Malgrat que fins a sis gavians van intentar repel·lir l'acció de l'arpella, aquesta va predar amb èxit dos dels tres nius que va localitzar en aquest breu període de temps

An anomaly in the number of secondary feathers in the Reed Bunting (Emberiza schoeniclus)

L'1.02.92 es va capturar un repicatalons a Canal Vell, Deltebre (Tarragona) que tenia una secundària extra a l'ala dreta. Aquesta ploma estava molt desgastada i sobresortia entre la cinquena i sisena secundària. L'explicació més probable de la presència d'aquesta ploma és que es tractava d'una ploma "fora de lloc" produïda durant el desenvolupament juvenil sense la punta de la beina de la ploma de la següent generació en la base del calamus

Intraspecific variation in digit reduction in Testudo : the case of the Hermann's tortoise

Phalangeal reduction is a common and widespread phenomenon among tortoises that has been associated with the adaptation to terrestrial life. While reduced manual digit 1 appears characteristic in almost all Testudo species, it is uncertain why the metacarpal I and distal carpal of the same digit are completely missing in some individuals of Hermann's tortoise (Testudo hermanni hermanni). To clarify this issue, we investigated the number of manual claws in six populations of Hermann's tortoise (one from the Ebro Delta in the Iberian Peninsula and five from Minorca Island), their age, sex, genetic lineage, and the substrate type that they inhabit. The number of claws was ascertained based on direct counts (n > 1500 individuals) and by X-rays (n = 32 individuals), obtaining three different phalangeal formulae: (1-2-2-2-1, D-2-2-2-1, 0-2-2-2-1). Thus, claw counts through both methodologies (direct count and X-ray) further confirm that the observed claws serve as a good proxy to assess the actual number of digits. Our results show no loss of phalanges, metacarpal and carpal bones in digit 1 associated with age, sex, or substrate, contrary to some previous authors who hypothesized a relationship between this loss and sexual dimorphism. Therefore, variations in the number of manual digits and the loss of metacarpal I and distal carpal in digit 1 in Hermann's tortoise are related to population and genetic lineage. More detailed comparisons with other Testudo hermanni populations from elsewhere in Europe would be required to understand the evolutionary significance concerning the intrapopulation variability in the number of digits remaining

Synthesis of the knowledge about Gull-billed Tern Gelochelidon nilotica diet in the Mediterranean area

This work analyses diet composition and trophic diversity of the Gull-billed Tern in 11 colonies in the Mediterranean basin based on published papers and original data from the Ebro Delta (NE Spain). Spearman correlation and correspondence analysis were used to assess the relationship between diet characteristics (trophic diversity and composition) and geographic localization of colonies. Insects were predominant in the diet of the Gullbilled Tern in the Ebro Delta (77.6%), as well as for most of the populations studied (mean of 59.4 % by population). Within insects, coleopterans and orthopterans were the most consumed. For the populations preferring aquatic prey (two localities), crustaceans were the most consumed prey. Vertebrates were less abundant in number (median of 8.5 % by population) and within this group, amphibians were predominant. We did not find any similarity in the diet depending on the geographic proximity of the populations nor any relationship between latitude of population and trophic diversity (reciprocal of index of Simpson 1/H). Finally, in the Mediterranean basin the diet of the Gullbilled Tern is basically formed by insects caught in terrestrial habitatsCe travail analyse le régime alimentaire de la Sterne hansel dans 11 colonies localisées en région Méditerranéenne à partir de travaux publiés et de données originales du delta de l’Èbre (NE Espagne). Nous avons utilisé le coefficient de corrélation de Spearman et l’analyse factorielle des correspondances pour déterminer s’il y a des relations entre le régime alimentaire (diversité trophique et composition) et la localisation géographique des colonies. Les insectes constituent la proie prédominante dans le régime alimentaire de la Sterne hansel du delta de l’Èbre (77,6 %) ainsi que dans la plupart des colonies (moyenne de 59,4 % par colonie). Parmi les insectes, les Coléoptères et les Orthoptères sont les plus consommés. Dans les populations où les proies aquatiques abondent (deux colonies), les crustacés sont les proies prédominantes. Les vertébrés sont numériquement peu abondants (médiane 8,5 % par colonie), les amphibiens étant les plus nombreux dans ce groupe. Les colonies les plus proches ne présentent pas une plus grande similarité dans le régime alimentaire et on ne trouve pas de relation entre la latitude des colonies et leur diversité trophique (inverse de l’indice de Simpson 1/H). Finalement, en région Méditerranéenne, le régime alimentaire de la Sterne hansel est constitué principalement d’insectes capturés dans les milieux terrestre