Invasive Signal Crayfish in the UK: Survey Methods to Inform Evidence-based Management

With invasive crayfish becoming increasingly widespread, evidence-based management is crucial to protect freshwater ecosystems. Knowledge of the structure and function of invasive crayfish populations allows for an effective evaluation of management efforts. Recent methodological developments have enabled the first truly quantitative studies of UK invasive crayfish populations in the field. This was achieved by the ‘triple drawdown’ (TDD) survey approach. In this article, we explore current survey approaches and their limitations, and we introduce the TDD method with its implications for crayfish survey, policy development and management

Prevalence and perspectives of illegal trade in cacti and succulent plants in the collector community

Although illegal wildlife trade (IWT) represents a serious threat to biodiversity, research into the prevalence of illegal plant collection and trade remains scarce. Because cacti and succulents are heavily threatened by overcollection for often illegal, international ornamental trade, we surveyed 441 members of the cacti and succulent hobbyist collector community with a mixed quantitative and qualitative approach. We sought to understand collector perspectives on the Convention on the International Trade in Endangered Species of Wild Flora and Fauna (CITES) and on the threats IWT poses to cactus and succulent conservation. Most respondents (74% of 401 respondents) stated that illegal collection in cacti and succulents represents a “very serious problem” and that the problem of wild plant collection is increasing (72% of 319 respondents). Most forms of illegal collection and trade were seen as very unacceptable by respondents. Self-reported noncompliance with CITES rules was uncommon (11.2% of 418 respondents); it remains a persistent problem in parts of the cacti and succulent hobbyist community. People engaging in rule breaking, such as transporting plants without required CITES documents, generally did so knowingly. Although 60.6% of 381 respondents regarded CITES as a very important tool for conservation, sentiment toward CITES and its efficacy in helping species conservation was mixed. Collectors in our survey saw themselves as potentially playing important roles in cactus and succulent conservation, but this potential resource remains largely untapped. Our results suggest the need for enhanced consultation with stakeholders in CITES decision-making. For challenging subjects like IWT, developing evidence-based responses demands deep interdisciplinary engagement, including assessing the conservation impact of species listings on CITES appendices

The ‘Pritchard Trap’: a novel quantitative survey method for crayfish

1. As crayfish invasions continue to threaten native freshwater biota, a detailed understanding of crayfish distribution and population structure becomes imperative. Nonetheless, most current survey methods provide inadequate demographic data. The quantitative ‘Triple Drawdown’ (TDD) dewatering method has highlighted the importance of such data, yet practical constraints prevent its large-scale application. 2. Here, we introduce the ‘Pritchard Trap’, a novel passive sampling method that reliably generates quantitative crayfish population data while requiring substantially lower sampling effort than TDDs. This quadrat-style sampler was extensively tested in headwater streams of North Yorkshire, England, along an invasion gradient for signal crayfish (Pacifastacus leniusculus) from well-established sites to mixed populations of signal crayfish and native white-clawed crayfish (Austropotamobius pallipes). 3. The Pritchard Trap was trialled over several time intervals to determine the minimum required trap deployment time. TDDs at the same sites allowed for a robust evaluation of Pritchard Trap sampling accuracy in representing crayfish densities and population structure. 4. The Pritchard Trap successfully sampled both invasive and native crayfish (8–42 mm carapace length). A minimum passive deployment time of 4 days was required. At low crayfish densities (0.5 individuals m−2), increased trapping effort was necessary to achieve accurate population density and size class distribution estimates. The Pritchard Trap required substantially less sampling effort (working hours) and resources than the TDD, whilst also posing less risk to non-target species. 5. The Pritchard Trap, for the first time, affords logistically simple, truly quantitative investigations of crayfish population demographics for headwater systems. It could be integrated into crayfish research and management, for example to explore density-dependent ecological impacts of invasive crayfish and their management responses or to monitor populations and recruitment in native crayfish conservation initiatives

Elevational species richness gradients in a hyperdiverse insect taxon: a global meta-study on geometrid moths

AIMS: We aim to document elevational richness patterns of geometrid moths in a globally replicated, multi-gradient setting, and to test general hypotheses on environmental and spatial effects (i.e. productivity, temperature, precipitation, area, mid-domain effect and human habitat disturbance) on these richness patterns. LOCATION: Twenty-six elevational gradients world-wide (latitudes 28° S to 51° N). METHODS: We compiled field datasets on elevational gradients for geometrid moths, a lepidopteran family, and documented richness patterns across each gradient while accounting for local undersampling of richness. Environmental and spatial predictor variables as well as habitat disturbance were used to test various hypotheses. Our analyses comprised two pathways: univariate correlations within gradients, and multivariate modelling on pooled data after correcting for overall variation in richness among different gradients. RESULTS: The majority of gradients showed midpeak patterns of richness, irrespective of climate and geographical location. The exclusion of human-affected sampling plots did not change these patterns. Support for univariate main drivers of richness was generally low, although there was idiosyncratic support for particular predictors on single gradients. Multivariate models, in agreement with univariate results, provided the strongest support for an effect of area-integrated productivity, or alternatively for an elevational area effect. Temperature and the mid-domain effect received support as weaker, modulating covariates, while precipitation-related variables had no explanatory potential. MAIN CONCLUSIONS: Despite the predicted decreasing diversity–temperature relationship in ectotherms, geometrid moths are similar to ants and salamanders as well as small mammals and ferns in having predominantly their highest diversity at mid-elevations. As in those comparative analyses, single or clear sets of drivers are elusive, but both productivity and area appear to be influential. More comparative elevational studies for various insect taxa are necessary for a more comprehensive understanding of elevational diversity and productivity

Anterior Thalamic High Frequency Band Activity Is Coupled with Theta Oscillations at Rest

Cross-frequency coupling (CFC) between slow and fast brain rhythms, in the form of phase–amplitude coupling (PAC), is proposed to enable the coordination of neural oscillatory activity required for cognitive processing. PAC has been identified in the neocortex and mesial temporal regions, varying according to the cognitive task being performed and also at rest. PAC has also been observed in the anterior thalamic nucleus (ATN) during memory processing. The thalamus is active during the resting state and has been proposed to be involved in switching between task-free cognitive states such as rest, in which attention is internally-focused, and externally-focused cognitive states, in which an individual engages with environmental stimuli. It is unknown whether PAC is an ongoing phenomenon during the resting state in the ATN, which is modulated during different cognitive states, or whether it only arises during the performance of specific tasks. We analyzed electrophysiological recordings of ATN activity during rest from seven patients who received thalamic electrodes implanted for treatment of pharmacoresistant focal epilepsy. PAC was identified between theta (4–6 Hz) phase and high frequency band (80–150 Hz) amplitude during rest in all seven patients, which diminished during engagement in tasks involving an external focus of attention. The findings are consistent with the proposal that theta–gamma coupling in the ATN is an ongoing phenomenon, which is modulated by task performance

Optimal perceived timing: integrating sensory information with dynamically updated expectations

The environment has a temporal structure, and knowing when a stimulus will appear translates into increased perceptual performance. Here we investigated how the human brain exploits temporal regularity in stimulus sequences for perception. We find that the timing of stimuli that occasionally deviate from a regularly paced sequence is perceptually distorted. Stimuli presented earlier than expected are perceptually delayed, whereas stimuli presented on time and later than expected are perceptually accelerated. This result suggests that the brain regularizes slightly deviant stimuli with an asymmetry that leads to the perceptual acceleration of expected stimuli. We present a Bayesian model for the combination of dynamically-updated expectations, in the form of a priori probability of encountering future stimuli, with incoming sensory information. The asymmetries in the results are accounted for by the asymmetries in the distributions involved in the computational process

Consequences of pond management for chironomid assemblages and diversity in English farmland ponds

Ponds represent a large potential resource for biodiversity in agricultural areas of lowland Europe though many are lost through natural succession towards damp woodland depressions (terrestrialisation). Managing ponds back towards their former open-water state may result in dramatic increases of biodiversity, even on heavily farmed land. Here, evidence is presented of the effects of terrestrialised farmland pond restoration on chironomid assemblages. Chironomid pupal exuviae were collected from three terrestrialised ponds on intensively-farmed land in North Norfolk, Eastern England. Two of the ponds had trees, scrub and sediment removed, while the third pond remained undisturbed as a control. Pupal exuviae collection resumed after the restoration period. In addition, nine unmanaged farm ponds and two formerly restored ponds were sampled. Nearby, another five restored ponds were also sampled for chironomid pupal exuviae. Water data revealed alkalinity, conductivity and phosphorus decreased while pH and dissolved oxygen increased after pond restoration. Chironomid species diversity, similarity and species compositional change were compared pre- and post-restoration. Assessments were made of chironomid species associated with colonisation of restored ponds as well as ponds without such management. After scrub and sediment removal the earliest colonisation of the ponds was by mud-eating species with rapid colonisation traits such as parthenogenesis, multiple generations in one year and tolerance of low oxygen conditions. Subsequent plant growth due to the opening up of the canopy led to consequent improved oxygenation and habitat structure. Other chironomid species dependent on these conditions were then able to compete with the early colonisers. Restoration also made a significant improvement in the number of chironomid species, as assessed by rarefaction curves

Revisiting hydro-ecological impacts of climate change on a restored floodplain wetland via hydrological/hydraulic modelling and the UK Climate Projections 2018 scenarios

The hydro-ecological impacts of 40 UK Climate Projections 2018 scenarios on a restored lowland England river floodplain are assessed using a MIKE SHE / MIKE 11 model. Annual precipitation declines for 60% of scenarios (range: -26%–21%, with small, <5%, declines for the central probability level). Potential evapotranspiration increases for all probability levels except the most extreme, very unlikely, 10% level (range: -4%–43%, central probability 9%–20%) Mean, peak and low river discharges are reduced for all but the extreme 90% probability level. Reduced frequency of bankfull discharge dominates (at least halved for the central probability level). Floodplain inundation declines for over 97% of 320 scenario-events. Winter water table levels still intercept the surface, while mean and summer low levels are reduced. Declines in mean summer floodplain water table levels for the central probability level (0.22 m and 0.28 m for the 2050s and 2080s, respectively) are twice as large as those in the more dynamic riparian area. Declines reach 0.39 m for some 10% probability level scenarios. Simulated hydrological changes differ subtly from a previous assessment using earlier UK climate projections. A soil aeration stress index demonstrates that, under baseline conditions, prolonged high winter floodplain water tables drive long periods of low root-zone oxygen, in turn favouring vegetation communities adapted to waterlogged conditions. Climate change reduces aeration stress and the extent of appropriate conditions for these plant communities in favour of communities less tolerant of wet conditions

Spectral fingerprints or spectral tilt? Evidence for distinct oscillatory signatures of memory formation

Decreases in low-frequency power (2-30 Hz) alongside high-frequency power increases (>40 Hz) have been demonstrated to predict successful memory formation. Parsimoniously, this change in the frequency spectrum can be explained by one factor, a change in the tilt of the power spectrum (from steep to flat) indicating engaged brain regions. A competing view is that the change in the power spectrum contains several distinct brain oscillatory fingerprints, each serving different computations. Here, we contrast these two theories in a parallel magnetoencephalography (MEG)-intracranial electroencephalography (iEEG) study in which healthy participants and epilepsy patients, respectively, studied either familiar verbal material or unfamiliar faces. We investigated whether modulations in specific frequency bands can be dissociated in time and space and by experimental manipulation. Both MEG and iEEG data show that decreases in alpha/beta power specifically predicted the encoding of words but not faces, whereas increases in gamma power and decreases in theta power predicted memory formation irrespective of material. Critically, these different oscillatory signatures of memory encoding were evident in different brain regions. Moreover, high-frequency gamma power increases occurred significantly earlier compared to low-frequency theta power decreases. These results show that simple "spectral tilt" cannot explain common oscillatory changes and demonstrate that brain oscillations in different frequency bands serve different functions for memory encoding