Density and structure of Saissetia oleae (Hemiptera: Coccidae) populations on citrus and olives: relative importance of the two annual generations

Saissetia oleae (Olivier) (Hemiptera: Coccidae) populations were studied and compared in citrus (Citrus spp.) and olive (Olea europaea L.) groves to determine the number of generations, crawler emergence periods and changes in population density during the year. Ten citrus and four olive groves were sampled regularly between March 2003 and December 2005 in eastern Spain, covering an area of 10,000 km2. Each sample consisted of 16 branches and 64 leaves. Saissetia oleae populations presented a similar trend in both crops during the three years of study. Populations peaked in July, when crawlers emerged after the egg-laying period, and decreased during several months due to mortality of first instars in summer. A second crawler emergence period, with lower numbers and more variability from year to year, occurred between October and March. Populations did not increase during this period, probably because most eggs and crawlers perished during the winter and also because females that gave rise to this fall-winter generation were half as big and fecund as spring females. No differences were found between the size of mature females that had developed on citrus and on olives during the spring. Considering this population pattern, the best seasonal period to apply pesticides to control S. oleae would be at the end of July, when populations are synchronous, all crawlers have already emerged, and first instars predominate.     

Geminivirus C2 protein might be the key player for geminiviral co-option of SCF-mediated ubiquitination

Viruses are obligate intracellular parasites, and need to create a suitable cell environment for viral propagation to complete their life cycle. In order to achieve this, viruses must usurp or interfere with the cellular machinery. Ubiquitination, a post-translational modification that controls numerous cellular processes, has proven to be a common target for viruses. Recently, geminivirus C2 protein has been shown to interact with the CSN complex and disrupt its activity over CULLIN1, interfering with the function of the CULLIN1-based SCF ubiquitin E3 ligases. Interestingly, over-expression of a given F-box protein may circumvent the general SCF malfunction caused by C2. This result raises the tantalizing idea that geminiviruses might be not only hampering, but also redirecting the activity of SCF complexes, thus co-opting the SCF-mediated ubiquitination pathway. We hypothesize that the mechanism of C2-facilitated co-option of SCF-mediated ubiquitination might not be exclusive for geminiviruses, but rather a common strategy for viruses.Key words: geminivirus, C2 protein, ubiquitination, SCF complex, CSN complex, F-box protein, pathogen co-option     

Recent trends in butterfly populations from north-east Spain and Andorra in the light of habitat and climate change

Although butterfly declines have been reported across Europe, no assessment based on detailed quantitative data has ever been made for any extensive area in the Mediterranean Basin. In 1994, a Butterfly Monitoring Scheme was launched in Catalonia (NE Spain), and in 2005 a similar, albeit much smaller, scheme started in the neighbouring Pyrenean country of Andorra. Here we provide a first thorough assessment of butterfly trends in both areas for the last 15 years. Several patterns emerged, above all a worrying decline of a substantial part of the fauna. It was also evident that habitat specialists are experiencing greater declines than habitat generalists, thereby butterfly communities becoming progressively dominated by common species. However, habitat indicators based on characteristic species also revealed that trends are actually associated with habitat types, grassland and scrub specialists declining strongly but woodland specialists showing a marginal increase. These differences are certainly related to profound landscape changes, mainly a dramatic reduction of semi-natural grasslands and open Mediterranean scrub, and a major increase in woodlands. The general effect of climatic warming on butterfly populations was investigated by using the temperature community index (CTI) approach. The thermal structure of butterfly communities remained very stable over time, except in one case where, contrary to the expectations, a significant negative trend in the CTI was noted. However, this surprising result can be explained by taking into account the above-reported pattern of butterfly communities becoming dominated by common species, characterized by low thermal indices in comparison with declining Mediterranean specialists.     

Pattern of expression of the podocalyxin gene in the mouse brain during development

We studied the expression pattern of the major renal protein Podocalyxin during the development of mouse brain using in situ hybridization. Podocalyxin mRNA was widely expressed at least from E14, the first age we studied, and expression remained high until adulthood. The highest levels of expression were postnatal. Podocalyxin expression was particularly elevated in the cortical plate, the hippocampus and cerebellum, and in several basal forebrain nuclei.     

Soil microbial carbon and nitrogen transformations at a glacial foreland on Anvers Island, Antarctic Peninsula

Microbial communities can play a critical role in soil development and succession at glacial forelands through their contribution to soil carbon (C) and nitrogen (N) cycling. Using a combination of molecular fingerprinting techniques and metabolic rate measurements, we examined the soil microbial community composition and key transformations in the C and N cycles at a glacial foreland on Anvers Island along the Antarctic Peninsula. Soils were sampled along transects representing a chronosequence of <1 to approximately 10?years since deglaciation. The soil microbial community was active adjacent to the receding edge of the glacier, where soil had been ice-free for <1?year. A survey of the microbial community composition identified typical soil bacterial species such as Arthrobacter and Sphingomonas, as well as known Antarctic heterotrophs, cyanobacteria and fungi. The soil C cycle over this zone was dominated by phototrophic microbial activity, while the N cycle was dominated by heterotrophic N₂-fixation and not cyanobacterial N₂-fixation as found at other recently deglaciated forelands. Other N transformations such as ammonia oxidation and denitrification appeared to be of limited relevance.     

Phylogeographic patterns of decapod crustaceans at the Atlantic-Mediterranean transition

Comparative multispecies studies allow contrasting the effect of past and present oceanographic processes on phylogeographic patterns. In the present study, a fragment of the COI gene was analyzed in seven decapod crustacean species from five families and with different bathymetric distributions. A total of 769 individuals were sampled along the Atlantic-Mediterranean transition area in order to test the effect of three putative barriers to gene flow: Strait of Gibraltar, Almeria-Oran Front and Ibiza Channel. A significant effect of the Strait of Gibraltar was found in the crabs Liocarcinus depurator and Macropipus tuberculatus. The Ibiza Channel had a significant effect for L. depurator. However, the Almeria-Oran front was not found to have a significant effect on any of the studied species. Higher levels of population structure were found in shallow-water species, although the number of species sampled should be increased to obtain a conclusive pattern. The haplotypes within the different species coalesced at times that could be related with past climatic events occurring before, during and after the last glacial maximum. Given the large diversity of phylogeographic patterns obtained within decapods, it is concluded that both historical and contemporary processes (marine current patterns, bathymetry and life-history traits) shape the phylogeographic patterns of these crustaceans.     

Autophagy modulates dynamics of connexins at the plasma membrane in a ubiquitin-dependent manner

Different pathways contribute to the turnover of connexins, the main structural components of gap junctions (GJs). The cellular pool of connexins targeted to each pathway and the functional consequences of degradation through these degradative pathways are unknown. In this work, we focused on the contribution of macroautophagy to connexin degradation. Using pharmacological and genetic blockage of macroautophagy both in vitro and in vivo, we found that the cellular pool targeted by this autophagic system is primarily the one organized into GJs. Interruption of connexins' macroautophagy resulted in their retention at the plasma membrane in the form of functional GJs and subsequent increased GJ-mediated intercellular diffusion. Up-regulation of macroautophagy alone is not sufficient to induce connexin internalization and degradation. To better understand what factors determine the autophagic degradation of GJ connexins, we analyzed the changes undergone by the fraction of plasma membrane connexin 43 targeted for macroautophagy and the sequence of events that trigger this process. We found that Nedd4-mediated ubiquitinylation of the connexin molecule is required to recruit the adaptor protein Eps15 to the GJ and to initiate the autophagy-dependent internalization and degradation of connexin 43. This study reveals a novel regulatory role for macroautophagy in GJ function that is directly dependent on the ubiquitinylation of plasma membrane connexins.     

A new look at computation of the complexity index in mangroves: do disturbed forests have clues to analyze canopy height patchiness?

This paper proposes some guidelines to compute complexity index in those mangroves where either seasonal or strong disturbances have occurred. We surveyed 31 mangrove localities in Buenaventura Bay, Central Pacific Coast of Colombia, where structural parameters were measured within a 0.1 ha plot. Also, most likely disturbances were noted for each plot. Complexity index was calculated in its classical form using the arithmetic mean of the three tallest trees(maximal mean) and alternatively using: a) the total mean: the height average of all trees recorded in each plot; and b) the mode: the most frequent tree height class (10 cm intervals) within each plot. Afterwards, we compared the three computations and discussed there liability of each one according to the current state by plot. In addition, all structural parameters were sorted in two diameter at breast height (dbh) cohorts (2.5–10 cm and ≥ 10 cm) to figure out which contributes more to the forest structure. We conclude the following: (a) The mean of the three tallest trees is not a good estimator of forest development when seasonal or strong disturbances occur since complexity index based in it always overestimates forest structure. (b) Seasonal disturbances and recruitment produce mosaic forests. The best estimator of this condition is the mean height which encompasses both central tendency and variability. (c) The modal height is also helpful to establish the dominant cohort when forests show two or more storied-canopies, or intermediate cohorts are missing. It also applies when a new stock of recruits is entering in a mature forest (the modal or maximal heights can be used interchangeably in this case). (d) Maximal height is the best estimator for uniformly developed forests with closed canopies and/or a single dominant tall-cohort. (e) If one is not confident about which height type to include to compute the complexity index, we recommend to sort out structure data by dbh-cohorts and calculate indices for both of them. This will show which cohort is contributing most to forest complexity. Finally, we suggest to exclude non-mangrove species from the complexity index computation since they mostly do not contribute significantly to forest basal area. This revised version was published online in July 2006 with corrections to the Cover Date.