Mismatch between the timing of oviposition and the seasonal optimum. The stochastic phenology of Mediterranean acorn weevils

1. The timing of reproduction is predicted to match the period of maximum food availability. In this sense, the case of many phytophagous insects in temperate regions is very illustrative, as their larvae usually depend on a resource only available for a limited period of time each year. 2. For 3 years the interactions between the weevil Curculio elephas and the Mediterranean Holm oak Quercus ilex were studied. Weevil larvae grow within the acorns, feeding on the cotyledons. The timing of oviposition will determine food availability for the larvae, as acorns stop growing once they are attacked. 3. Acorn temporal growing patterns did not change between years and food availability for larvae was at its highest in October, when temperature was still suitable for larval development. However, oviposition phenology did change between years. In 2002 females oviposited later, larvae grew within larger acorns, and their body mass was significantly higher than in 2003 or 2004, when females oviposited into early acorns. 4. Thus, weevils do not always adjust oviposition to the best possible feeding conditions for their offspring. Rather, they seem to maximise their own lifetime fitness, ovipositing as soon as they emerge in late summer. Emergence, in turn, depends strongly on stochastic events such as summer storms in the Mediterranean region. 5. Under a climate change perspective, the trend towards higher August rainfall recorded in our study area may alter oviposition phenology, with the subsequent cascade effects on weevil body size and fitness     

Chromosomal studies in species of Salvia (Lamiaceae) from Argentina

Meiotic and mitotic chromosomes of 13 species of Salvia from Argentina were studied. Most of our data are new counts but some, mainly from cultivated species, confirm previous reports or represent numbers which are different from those cited previously. Only Salvia gilliesii Benth. and the introduced species S. coccinea Juss., S. farinacea Benth., S. involucrata Cav. and S. microphylla Kunth are diploids. S. cardiophylla Benth., S. procurrens Benth. , S. splendens Roem. & Schult. and S. uliginosa Benth. are tetraploids; S. stachydifolia Benth. is hexaploid; and S. guaranitica A. St.-Hil., S. pallida Benth. and S. rypara Briq. are octoploids. The basic number most frequently found is x  = 11, but two species, S. procurrens and S. uliginosa , have x  = 13. S. farinacea has x  = 10 but this species is a widespread cultivated plant, not native in this area. Seven of the studied species showed one to three B chromosomes. We discuss some systematic and evolutionary aspects of the genus in the light of the cytogenetic data, the relationships between geographical distribution and chromosome numbers in relation to levels of ploidy and basic chromosome numbers, and make comparisons with some of the different taxonomic sections.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 141 , 483–490.     

On Space As A Capacity

This article is about space and social relationships. More precisely, it is about the space of and in social relationships. It is also about the efficacy of social relationships in segregating their own contexts of meaning and value. The article also addresses the question of how agency comes about. This 'coming about' of agency, its swelling and appearance in a structure of meaning, is what I call 'capacity'. Social relationships have 'capacity'. That is, they have both spaciousness and potency. They accomplish things, and accomplish things 'somewhere'. In this respect, space (or the capacity of social relationships) is something very different from idioms that we have come to think of as forms of space, like landscape or place. This article is also, therefore, a critique of the way in which some anthropologists have recently theorized landscape and place. My argument is based on an ethnographic account of the dimensions through which people construct urban space in the Chilean city of Antofagasta.     

THE INTER-SERTOLI CELL TIGHT JUNCTIONS IN GERM CELL-FREE SEMINIFEROUS TUBULES FROM PRENATALLY IRRADIATED RATS: A FREEZE-FRACTURE STUDY

The tight junctions between Sertoli cells were examined by freeze-fracture in 3-month-old prenatally irradiated rats, whose seminiferous tubules are devoid of germ cells. The replicas from irradiated tubules show elaborate interdigitations of the lateral membranes of Sertoli cells and very extensive tight junctions. These junctions are characterized by a great number of continuous parallel or complex interweaving strands of intramembranous particles, preferentially associated with E fracture faces. The presence of highly cross-linked tight junctional strands is compatible with an epithelium deprived of germ cells, with a reduced need for flexibility. Anomalous ectoplasmic specializations, consisting of groups of cisternae arranged perpendicularly to the lateral surface, are found in the irradiated tubules. These structures may be involved in a storage mechanism of redundant lateral membrane resulting from the elimination of germ cells. Typical gap junctions, intercalated between the tight junctional strands, are larger and more frequently found in treated animals than in controls. These findings indicate that a very tight permeability barrier seems to be established in the irradiated testis even in the absence of germ cells. Thus, the formation and maintenance of Sertoli tight junctions do not appear to be directly dependent on the presence of germ cells. Nevertheless, the alterations detected in the tight junction architecture and in the ectoplasmic specializations indicate that maturing germ cells probably contribute to the functional organization of the blood—testis barrier in the normal testis.     

Changes in fish assemblages in catchments in north‐eastern Spain: biodiversity,conservation status and introduced species

1. North‐eastern Spain is a hot spot for the introduction of alien fish species, and its native fish fauna is one of the most endangered worldwide. We used an extensive data set from 2002 to 2003 and historical information from the area to characterize fish diversity and establish conservation priorities in river catchments. 2. Diversity indices were used to characterize fish diversity at the basin scale. An index of conservation status was applied for each species, which considers the occurrence, abundance and endemicity of each taxon. We used indirect ordination methods to test the relationship among basin features and to identify those variables most correlated with each other. To identify physical, biotic and environmental characteristics that seem to make a basin particularly susceptible to invasion, we performed a step‐wise multiple regression to examine the relationship between the number of native, translocated and introduced fish species (including the original native species richness of each basin), and landscape variables. 3. Over a period of approximately 50 years, the mean range size of native fish species has decreased by 60%. The greatest decline occurred in Gasterosteus gymnurus, Anguilla anguilla and Salaria fluviatilis, for which species over 75% of the original distribution area has been lost. The species with the highest conservation index were Gasterosteus gymnurus and Salaria fluviatilis. 4. Basin area and the catchment type explained 70% of variation in native species richness, whereas the number of dams and basin area accounted for more than 80% of variation in the number of introduced species. 5. The original native species richness and the number of introduced species at basin scale were not related, and thus there was no evidence of “biotic resistance” to invasion. The restoration of natural hydrologic processes and the development of specific management tools to protect native species, such as the prioritization of areas for fish conservation and the eradication of local populations of exotic species, are required to restore native fish fauna in these catchments.