Abstract: Temperature, food quantity and quality play important roles in insect growth and survival, influencing population dynamics as well as interactions with other community members. However, the interaction between temperature and diet and its ecological consequences have been poorly documented. Toxorhynchites are well-known biocontrol agents for container-inhabiting mosquito larvae. We found that Toxorhynchites haemorrhoidalis larvae (Diptera: Culicidae) inhabiting water-filled rosettes of tank bromeliads catch and eat prey of both aquatic (mosquito larvae) and terrestrial origin (ants), using distinct predatory methods. They carried out frontal attacks on ants, but ambushed mosquito larvae. In choice tests, T. haemorrhoidalis favored terrestrial prey. Temperature had a significant effect on predator development and survival through its interaction with diet, but did not alter the preference for ants. T. haemorrhoidalis larvae emerged quickly when fed only mosquito larvae, whereas all individuals died before pupation when fed only ants. We conclude that behavioral factors (i.e., attraction to ants that disturb the surface of the water) overtake physiological factors (i.e., the adverse outcome of elevated temperature and an ant-based diet) in determining a predator's response to temperature:diet interactions. Finally, because T. haemorrhoidalis larvae preferentially feed on terrestrial insects in tank bromeliads, mosquito larvae may indirectly benefit from predation release. © 2015 Association for Tropical Biology and Conservation Inc.

Abstract: The duration of the dry seasons in south-eastern Amazonia is expected to increase. Little is known of how freshwater assemblages respond to drought in the humid rainforests and of the extent to which they resist the absence of rainfall before the collapse of the system. We manipulated rainshelters over tank-forming bromeliads (i.e. the interlocking leaf axils of these plants form wells that collect rainwater) to simulate an exceptionally long dry period (49 days, compared with a 10-year mean ± SD annual maximum number of 17 ± 5.3 days without rainfall at the study site) and then a rewetting period. By sampling weekly over 3 months, we followed the dynamics of the representation of abundance-weighted traits in invertebrate assemblages in these treatment plants and in a control group. The functional structure of assemblages was drought resistant until the water volume in the bromeliad pools dropped by 90%, when there was a sudden shift in the functional trait structure due to the loss of most populations except the drought-resistant culicids. Traits related to life history, body size and preferred food showed significant responses to drought. There was a convergence in the functional traits of species surviving in dry plants, strengthening the idea that environmental filtering, rather than stochasticity, determines the functional trajectory of aquatic assemblages during drought. At the end of the dry period, samples of the detritus potentially containing drought-resistant eggs/cysts (and eventually live larvae) were taken from the dry plants and rewetted in the laboratory, allowing us to distinguish resistant species from those requiring recolonisation via subsequent oviposition by adults from elsewhere. Patches of water-filled bromeliads persisting in the area provided the most important pool of colonists, and communities returned to the pre-disturbance state within 1-2 weeks of rewetting. Our results suggest that the functional trait structure of invertebrate assemblages in bromeliads could remain stable under scenarios of precipitation change that would triple the duration of current dry periods at a local scale. Future experiments should evaluate how environmental factors might alter the tipping point between resistance to drought and a collapse in ecosystem processes. © 2015 John Wiley & Sons Ltd.

Abstract: The survey of plant and animal populations is central to undertaking field ecology. However, detection is imperfect, so the absence of a species cannot be determined with certainty. Methods developed to account for imperfect detectability during surveys do not yet account for stochastic variation in detectability over time or space. When each survey entails a fixed cost that is not spent searching (e.g., time required to travel to the site), stochastic detection rates result in a trade-off between the number of surveys and the length of each survey when surveying a single site. We present a model that addresses this trade-off and use it to determine the number of surveys that: 1) maximizes the expected probability of detection over the entire survey period; and 2) is most likely to achieve a minimally-acceptable probability of detection. We illustrate the applicability of our approach using three practical examples (minimum survey effort protocols, number of frog surveys per season, and number of quadrats per site to detect a plant species) and test our model's predictions using data from experimental plant surveys. We find that when maximizing the expected probability of detection, the optimal survey design is most sensitive to the coefficient of variation in the rate of detection and the ratio of the search budget to the travel cost. When maximizing the likelihood of achieving a particular probability of detection, the optimal survey design is most sensitive to the required probability of detection, the expected number of detections if the budget were spent only on searching, and the expected number of detections that are missed due to travel costs. We find that accounting for stochasticity in detection rates is likely to be particularly important for designing surveys when detection rates are low. Our model provides a framework to do this. © 2014 Moore et al.

Abstract: Geomorphic landscape features have been suggested as indicators of forest diversity. However, their explanatory power has not yet been explicitly tested at a regional scale in tropical rainforest. We used forest inventories conducted according to a stratified sampling design (3,132 plots in 111 transects at 33 sites) and holistic multi-scale geomorphological mapping derived from a Shuttle Radar Topography Mission digital elevation model to describe and explain spatial patterns in floristic composition across French Guiana (80,000 km2). We measured and identified 123,906 trees with DBH ≥20 cm and used constrained and unconstrained ordinations to analyze variations in the abundance of 221 taxa and 51 families. Variance partitioning and variograms were used to detect spatial patterns in species composition, compare the explanatory power of spatial and environmental factors, and select the variables that best explain forest composition. Strong floristic patterns corresponded to a major latitudinal gradient and significant sub-regional floristic structure. Geomorphological landscapes shaped by historic climate fluctuations and major geological events successfully captured these patterns and explained the variation in abundance of 80 taxa, corresponding to 65 % of the inventoried trees. Our findings suggest that long-term forest dynamics are under substantial “geomorphographic control”. A geomorphological perspective on landscapes that incorporates current and past environmental filters and historical biogeographical processes could thus be used more systematically in tropical regions for regional planning and forest conservation. © 2014, Springer Science+Business Media Dordrecht.

Abstract: Electroactive biofilms were formed from French Guiana mangrove sediments for the analysis of bacterial communities' composition. The electrochemical monitoring of three biofilm generations revealed that the bacterial selection occurring at the anode, supposedly leading microbial electrochemical systems (MESs) to be more efficient, was not the only parameter to be taken into account so as to get the best electrical performance (maximum current density). Indeed, first biofilm generations produced a stable current density reaching about 18A/m2 while second and third generations produced current densities of about 10A/m2. MES bacterial consortia were characterized thanks to molecular biology techniques: DGGE and MiSeq® sequencing (Illumina®). High-throughput sequencing data statistical analysis confirmed preliminary DGGE data analysis, showing strong similarities between electroactive biofilms of second and third generations, but also revealing both selection and stabilization of the biofilms. © 2015 Elsevier B.V.