Behavioural differences underlie toxicity and predation variation in blooms of Prymnesium parvum

Much of the evolutionary ecology of toxic algal blooms (TABs) remains unclear, including the role of algal toxins in the adaptive ‘strategies’ of TAB-forming species. Most eukaryotic TABs are caused by mixotrophs that augment autotrophy with organic nutrient sources, including competing algae (intraguild predation). We leverage the standing diversity of TABs formed by the toxic, invasive mixotroph Prymnesium parvum to identify cell-level behaviours involved in toxin-assisted predation using direct observations as well as comparisons between genetically distinct low- and high-toxicity isolates. Our results suggest that P. parvum toxins are primarily delivered at close range and promote subsequent prey capture/consumption. Surprisingly, we find opposite chemotactic preferences for organic (prey-derived) and inorganic nutrients between differentially toxic isolates, respectively, suggesting behavioural integration of toxicity and phagotrophy. Variation in toxicity may, therefore, reflect broader phenotypic integration of key traits that ultimately contribute to the remarkable flexibility, diversity, and success of invasive populations.     

Macroalgae exhibit diverse responses to human disturbances on coral reefs

Scientists and managers rely on indicator taxa such as coral and macroalgal cover to evaluate the effects of human disturbance on coral reefs, often assuming a universally positive relationship between local human disturbance and macroalgae. Despite evidence that macroalgae respond to local stressors in diverse ways, there have been few efforts to evaluate relationships between specific macroalgae taxa and local human-driven disturbance. Using genus-level monitoring data from 1205 sites in the Indian and Pacific Oceans, we assess whether macroalgae percent cover correlates with local human disturbance while accounting for factors that could obscure or confound relationships. Assessing macroalgae at genus level revealed that no genera were positively correlated with all human disturbance metrics. Instead, we found relationships between the division or genera of algae and specific human disturbances that were not detectable when pooling taxa into a single functional category, which is common to many analyses. The convention to use percent cover of macroalgae as an indication of local human disturbance therefore likely obscures signatures of local anthropogenic threats to reefs. Our limited understanding of relationships between human disturbance, macroalgae taxa, and their responses to human disturbances impedes the ability to diagnose and respond appropriately to these threats.     

Protein network prediction and topological analysis in <Emphasis Type="Italic">Leishmania major</Emphasis> as a tool for drug target selection

Background  

Leishmaniasis is a virulent parasitic infection that causes a worldwide disease burden. Most treatments have toxic side-effects and efficacy has decreased due to the emergence of resistant strains. The outlook is worsened by the absence of promising drug targets for this disease. We have taken a computational approach to the detection of new drug targets, which may become an effective strategy for the discovery of new drugs for this tropical disease.     

A physical and genetic linkage map of the distal long arm of human chromosome 5.

By in situ hybridization of probes for three cloned genes and eight genetically-linked polymorphic DNA markers, we have prepared a physical map of the distal long arm of chromosome 5. These results, together with the localizations of 11 genes and the genetic linkage map reported previously by us and by other investigators, represent a map that spans 55 cM.     

Presence of Caulerpa racemosa (Forsskål) J. Agardh in Ceuta (Northern Africa, Gibraltar Area)

Caulerpa racemosa (Forsskål) J. Agardh has been recorded along the Mediterranean Sea since the 1920s, and since then has continually invaded its coasts moving westward towards the Atlantic. In recent years, authors have revealed the negative effect of the species on the Mediterranean’s benthic communities. Taking into account that the latest reference placed the species in Murcia (Southeastern Spain) in 2005, we now give evidence here of the presence of this invasive algae in Ceuta, a Spanish city located in the Strait of Gibraltar on the North Africa Coast. This is the first and westernmost recorded presence of the species in the area. Characteristics of the located patches are given.     

Intraspecific interactions affect the spatial pattern of a dominant shrub in a semiarid shrubland: A prospective approach

Dispersal, physical conditions and biotic interactions contribute to determine the spatial distribution of individuals in plant populations. Much of what we know has been learned from studies that retrospectively posit mechanisms presumed to have generated the observed spatial patterns. Here we present a prospective approach. We start by measuring spatial demographic effects and evaluate if they can generate observed spatial patterns. We evaluated the influence of interactions among conspecifics on vital rates, demography and spatial distribution of Croton aff. wagneri, a dominant shrub in dry Andean ecosystems. Recruitment, survival and growth varied in relation with distance to conspecifics neighbours and with their summed cover. We built a spatial individual-based model and simulated its population dynamics in 30 × 30 m plots for a 30-year period. We compared the predicted spatial pattern from these demographic models with that observed among plants in 16 independent plots with the same area. Simulated populations mimicked observed spatial patterns, although in plots at high elevations the simulated populations did not reproduce the observed inhibition at small scales. Observed and simulated patterns indicated differences between elevations in maximum aggregation and location of the distances with higher aggregation. We discuss how consideration of critical seed and juvenile stages and interspecific interactions could further improve our understanding of spatial pattern and recommend that these factors be considered in future models.     

ALLELOPATHY AS AN EMERGENT,EXPLOITABLE PUBLIC GOOD IN THE BLOOM‐FORMING MICROALGA PRYMNESIUM PARVUM

Many microbes cooperatively secrete extracellular products that favorably modify their environment. Consistent with social evolution theory, structured habitats play a role in maintaining these traits in microbial model systems, by localizing the benefits and separating strains that invest in these products from ‘cheater’ strains that benefit without paying the cost. It is thus surprising that many unicellular, well‐mixed microalgal populations invest in extracellular toxins that confer ecological benefits upon the entire population, for example, by eliminating nutrient competitors (allelopathy). Here we test the hypotheses that microalgal exotoxins are (1) exploitable public goods that benefit all cells, regardless of investment, or (2) nonexploitable private goods involved in cell‐level functions. We test these hypotheses with high‐toxicity (TOX+) and low‐toxicity (TOX?) strains of the damaging, mixotrophic microalga Prymnesium parvum and two common competitors: green algae and diatoms. TOX+ actually benefits from dense populations of competing green algae, which can also be prey for P. parvum, yielding a relative fitness advantage over coexisting TOX?. However, with nonprey competitors (diatoms), TOX? increases in frequency over TOX+, despite benefiting from the exclusion of diatoms by TOX+. An evolutionary unstable, ecologically devastating public good may emerge from traits selected at lower levels expressed in novel environments.     

The sandfly fauna,anthropophily and the seasonal activities of Pintomyia spinicrassa (Diptera: Psychodidae: Phlebotominae) in a focus of cutaneous leishmaniasis in northeastern Colombia

This study was conducted to identify the sandfly fauna and the anthropophilic species in a coffee-growing area of Villanueva, Norte de Santander, Colombia, a focus of American cutaneous leishmaniasis, and to analyse the relationship between the most frequent species and rainfall, relative humidity and temperature, with the aim of contributing to epidemiological surveillance in the area. Sandfly collections were performed fortnightly between February 2006-September 2007 using automatic light traps, Shannon traps, protected human bait and aspiration in resting places. A total of 7,051 sandflies belonging to 12 species were captured. Pintomyia spinicrassa (95.7%) predominated. Pintomyia oresbia and Lutzomyia sp. of Pichinde were found in the state of Norte de Santander for the first time. Pi. spinicrassa, Pintomyia nuneztovari, Micropygomyia venezuelensis, Lutzomyia (Helcocyrtomyia) scorzai and Lu. (Helcocyrtomyia) sp. were captured on the protected human bait. A significant association between Pi. spinicrassa abundance and the total rainfall and the average temperature and humidity 10 days before the collection was observed. The dominance of Pi. spinicrassa, a recognised vector of Leishmania braziliensis, especially during the dry periods, indicates that the risk of parasite transmission may increase.