Undesirable side-effects of water hyacinth control in a shallow tropical reservoir

1. Based on a comprehensive data set collected monthly during 8 years (1997–2004), we evaluated the effects of mechanical removal of Eichhornia crassipes on the limnological characteristics and algal biomass of a polymictic shallow tropical reservoir. 2. Interrupted time series analyses indicated that the limnological responses to macrophyte removal can be classified as an ‘abrupt permanent impact’ implying that the overall mean of the time‐series shifted promptly after intervention. These analyses indicated a significant increase for pH, total phosphorus, total phytoplankton and cyanobacterial biomass, and a decrease in water transparency and CO₂ concentrations in the surface water; also, the increase in water stability, increase of bottom soluble reactive phosphorus (SRP) and decrease in bottom oxygen levels. 3. Cyclic anoxic periods previously observed during springs and summers were replaced by a persistent period of anoxic conditions in the sediment overlying water. Anoxic conditions were suitable for SRP release from sediments. Heavy cyanobacterial blooms became more persistent, maximum biomass (4229 mm³ L⁻¹) was 30 times larger, the blooms frequently reached 2 m and sometimes the bottom of the reservoir, contrasting to the preremoval period in which it reached at most 1 m deep. 4. The long‐term P dynamics in the system, initially driven by allochthonous nutrient loadings were replaced by internal ecological processes. Water hyacinth removal markedly accelerated the process of eutrophication due to internal feedback mechanisms, leading to a switch to a more turbid state. Biological feedback mechanisms were driven by cyanobacterial blooms by enhancing water stability, oxygen anoxia at the bottom and by increasing suitable conditions for P internal loading. These data support the hypothesis of the role of cyanobacterial blooms as an important factor impairing water quality and driving the ecosystem towards a stable degraded state. 5. These findings have important implications for the restoration of shallow stratifying eutrophic lakes, as the alternative degraded state is most likely to occur when compared with their non‐stratifying counterparts. Moreover, feedback mechanisms in tropical and subtropical shallow lakes seem to be stronger than in temperate ones, as stratification events are more likely to occur over the year, intensifying system resilience to restorative strategies.     

Genotypic and phenotypic diversity in Colletotrichum acutatum, a cosmopolitan pathogen causing anthracnose on a wide range of hosts

Colletotrichum acutatum causes anthracnose on a wide range of hosts including woody and herbaceous crops, ornamentals, fruits and conifers. Almond, citrus, lupin, olive and strawberry are some of the crops in which C. acutatum diseases are economically important. With the application of molecular markers and diagnostic PCR over the last 10–15 years, C. acutatum was identified as a major pathogen on a number of hosts instead of or along with C. gloeosporioides . C. acutatum displays high levels of genotypic and phenotypic diversity. The global populations of this cosmopolitan pathogen fit into at least eight distinct molecular groups, A1–A8, which show some degree of correlation with the morphological characteristics and varying patterns of host association and geographical distribution. The pathogen has complex epidemiology, exhibiting pathogenic and non-pathogenic lifestyles on target hosts, non-target crops and weeds. C. acutatum populations also show pathogenic variability and cross-infection potential in relation to a number of hosts. Molecular genetic tools are being developed to investigate the pathogenicity mechanisms of this key pathogen. This article mainly focuses on the global population diversity in C. acutatum , pathogen epidemiology and diagnosis, host colonization processes, and the development of tools for the identification and analysis of genes associated with pathogenicity. Background information on the pathogen origin, host range, disease symptoms and disease management strategies is also provided.     

Sexual cannibalism in scorpions: fact or fiction?

Females of several scorpion species are currently deemed to be sexual cannibals, but this reputation is, however, largely built on anecdotal evidence from the older literature. Theoretical models predict that given the low rates of female-male encounter, males should allow themselves to be cannibalized after sperm transfer. The present paper examines the information available for a number of species to determine (a) whether sexual cannibalism is as widespread as previously suggested, and (b) whether it is likely to involve male self-sacrifice. Information on three scorpions currently regarded as sexual cannibals is presented: the bothriurids Bothriurus bonariensis (C.L. Koch) and Urophonius jheringii Pocock, and the buthid Leiurus quinquestriatus (Hemprich & Ehrenberg). No post-mating cannibalism was ever observed in these species, nor in another 19 representatives of four families. In L. quinquestriatus only two cases of cannibalism of the male by the female occurred, both in the beginning of courtship and after long periods of food deprivation. We suggest that if sexual cannibalism occurs in scorpions, it is most likely to be of an 'economic' type, where females perceive males as prey rather than mates, and not a 'self-sacrificial', post-mating cannibalism enhancing the fitness of the offspring of the male.     

Mutational analysis of the <Emphasis Type="Italic">GLA</Emphasis> gene in Mexican families with Fabry disease

Fabry disease (FD) is a lysosomal storage disorder, which develops due to a deficiency in the hydrolytic enzyme, α-galactosidase A (α-Gal A). Alpha-Gal A hydrolyzes glycosphingolipid globotriaosylceramide (Gb3), and an α-Gal A deficiency leads to Gb3 accumulation in tissues and cells in the body. This pathology is likely to involve multiple systems, but it is generally considered to affect primarily vascular endothelium. In this study, we investigated mutations in the GLA gene, which encodes α-Gal A, in Mexican families with FD. We included seven probands with FD that carried known mutations. We analysed pedigrees of the probands, and performed molecular screening in 65 relatives with the potential of carrying a GLA mutation. Five mutations (P40S, IVS4 ⁺⁴, G328V, R363H, R404del) were detected in seven unrelated Mexican families with the classic FD phenotype. Of the 65 relatives examined, 42 (64.6%) had a GLA gene mutation. In summary, among seven Mexican probands with FD, 65 relatives were at risk of carrying a known GLA mutation, and molecular screening identified 42 individuals with the mutation. Thus, our findings showed that it is important to perform molecular analysis in families with FD to detect mutations and to provide accurate diagnoses for individuals that could be affected.     

Isolation and characterization of microsatellite markers from Musa balbisiana

This is the first report of targeted development of B genome microsatellite markers in Musa. A total of 44 sequences with microsatellites were isolated from an enriched library of Musa balbisiana cv. ‘Tani’ (BB genome). Of these, 25 were polymorphic when screened on 14 diverse diploid and triploid Musa accessions. The number of alleles detected by each marker ranged between one and seven. All 25 microsatellite markers generated amplification products in all species and genome complements. These new microsatellite markers fill an important gap for diversity assessment and linkage mapping studies in plantain (AAB) and cooking banana (ABB).     

Haematozoa infections in a Great Tit Parus major population in Central Portugal: relationships with breeding effort and health

Blood parasites may act as modulators of their hosts' ecology, life histories and fitness. We studied the prevalence of Plasmodium sp., Haemoproteus sp. and Leucocytozoon sp. and their effects on morphological, biochemical and haematological variables and on breeding effort of Great Tits Parus major . Total prevalence (percentage of individuals infected by any parasite) ranged from 7.7% to 61.1%. There was an overall positive association in prevalence between the three haematozoan parasites. No effect of sex or age on infection status was observed. Negative impacts of infection on physiological condition depended largely on year and/or season and included effects on body condition index, plasma protein and haemoglobin index. There were also indications that parasite infection increased immune response and stress levels and activated antioxidant defence mechanisms. Males with higher fledging success had a higher probability of Haemoproteus infection, and females laying heavier eggs had a higher probability of Plasmodium infection. However, clutch size was negatively associated with the probability of infection by Leucocytozoon and Haemoproteus . Surprisingly, males raising second broods had a lower prevalence of both Haemoproteus and Leucocytozoon . Only 5.7% of first-brood nestlings were infected, but those in infected nestboxes had a lower heterophil/lymphocyte ratio. This study confirms the pathogenicity of blood parasites to the host by demonstrating negative effects of infection on both physiology and breeding performance.     

Effect of water availability on leaf water isotopic enrichment in beech seedlings shows limitations of current fractionation models

Current models of leaf water enrichment predict that the differences between isotopic enrichment of water at the site of evaporation (Δ_e) and mean lamina leaf water enrichment (Δ_L) depend on transpiration rates ( E ), modulated by the scaled effective length ( L ) of water isotope movement in the leaf. However, variations in leaf parameters in response to changing environmental conditions might cause changes in the water path and thus L . We measured the diel course of Δ_L for ¹⁸O and ²H in beech seedlings under well-watered and water-limited conditions. We applied evaporative enrichment models of increasing complexity to predict Δ_e and Δ_L, and estimated L from model fits. Water-limited plants showed moderate drought stress, with lower stomatal conductance, E and stem water potential than the control. Despite having double E , the divergence between Δ_e and Δ_L was lower in well-watered than in water-limited plants, and thus, L should have changed to counteract differences in E . Indeed, L was about threefold higher in water-limited plants, regardless of the models used. We conclude that L changes with plant water status far beyond the variations explained by water content and other measured variables, thus limiting the use of current evaporative models under changing environmental conditions.     

High European sauropod dinosaur diversity during Jurassic–Cretaceous transition in Riodeva (Teruel, Spain)

Abstract:  Up to now, more than 40 dinosaur sites have been found in the latest Jurassic – earliest Cretaceous sedimentary outcrops (Villar del Arzobispo Formation) of Riodeva (Iberian Range, Spain). Those already excavated, as well as other findings, provide a large and diverse number of sauropod remains, suggesting a great diversity for this group in the Iberian Peninsula during this time. Vertebrae and ischial remains from Riodevan site RD-13 are assigned to Turiasaurus riodevensis (a species described in RD-10, Barrihonda site), which is part of the Turiasauria clade. This is the first time that a taxon is attributed to Turiasaurus genus out of its type site. A Neosauropod caudal vertebra from the RD-11 site has been classified as Diplodocinae indet., supporting the previous attribution on an ilion also found in Riodeva (CPT-1074) referring to the Diplodocidae clade. New remains from the RD-28, RD-41 and RD-43 sites, of the same age, among which there are caudal vertebrae, are assigned to Macronaria. New sauropod footprints from the Villar del Arzobispo Formation complete the extraordinary sauropod record coming to light in the area. The inclusion of other sauropods from different contemporaneous exposures in Teruel within the Turiasauria clade adds new evidence of a great diversity of sauropods in Iberia during the Jurassic–Cretaceous transition. Turiasauria distribution contributes to the understanding of European and global palaeobiogeography.     

Relationship between floral tube length and nectar robbing in Duranta erecta L. (Verbenaceae)

Although nectar robbing is a common phenomenon in plant species with tubular flowers or flowers with nectar spurs, the potential effect of this illegitimate interaction on plant reproductive success has not received the deserved attention. In the present study, we analysed the functional relationship between flower morphology and nectar robbing, and examined the reproductive consequences of the interaction in a population of Duranta erecta (Verbenaceae) on the island of Cuba. The results show that nectar robbing is conducted by the carpenter bees Xylocopa cubaecola and affects up to 44% of flowers in the studied population. However, not all the flowers have the same probability of being robbed. The chance of flowers being robbed increases with flower length and flower diameter. Moreover, nectar robbing significantly decreases the chance that flowers will set fruit. Also, the impact of nectar robbing on the probability of flowers to set fruits is dependent on the plant. We suggest that nectar robbing may represent an opposite selective force that balances the selection for longer corollas often imposed by pollinators specializing in visiting tubular flowers. Such a relationship with nectar robbers would have obvious implications for the evolution of tubular or closed flowers. This preliminary finding deserves further research in light of the ecological and evolutionary consequences of nectar robbing in tubular flowers.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 392–398.