Riverine Habitats Research Articles

‘Where are the dead flies!’: perceptions of local communities towards the deployment of Tiny Targets to control tsetse in the Democratic Republic of the Congo

The National Programme for the control of human African trypanosomiasis in Democratic Republic of Congo includes a large-scale vector control operation using Tiny Targets. These are small panels of insecticide-impregnated...

Impacts of hydrological conditions on the activities of soil enzymes in temperate floodplain forest sites

Context The development and survival of floodplain forests are dependent on the occurrence of seasonal flooding that provides soil moisture and nutrient availability suitable for the development of soil microorganisms, which are the main sources of soil enzymes involved in the decomposition and mineralisation of soil organic matter. Aims We compared the soil enzyme activities of a floodplain forest in the Lower Vistula Valley, Poland, cut off for 80 years from the river by artificial embankment, and of two other floodplain forests located in close vicinity and subjected to seasonal flooding. We hypothesised that inhibiting the inflow of the river water to the floodplain forest will alter the soil water and mineral conditions, decreasing the activity of extracellular soil enzymes. Methods Enzyme activity, soil moisture content, and pH were monitored for 3 years in the upper soil level (0–30 cm). The activities of soil β-glucosidase, acid phosphatase, alkaline phosphatase, and nonspecific dehydrogenase were determined by spectrophotometry. Key results Inhibition of floods decreased soil moisture, the concentrations of carbon, nitrogen, and phosphorus, as well as the activity of soil enzymes. Conclusions Forest site and soil depth, but not season, had significant effects on soil chemical and biological features. Soil enzyme activities were significantly positively correlated with soil moisture and the levels of total and organic carbon, total nitrogen, and available phosphorus, as well as the carbon/nitrogen ratio. Implications This information is essential for the protection and restoration of riverine habitats destroyed by human activity.

Threats to Fish Biodiversity in Bangladesh Waters and Measures for Revival of Declining Population

Bangladesh is rich in fish biodiversity covering interconnected riverine, coastal and marine habitats. Many researchers reported different potentials and threats of biodiversity and suggested measures to minimize the threats. Revival story of hilsa and relevant fish population revealed hopes and ways of sustainable biodiversity management. We attempted to compile the fragmentary fish biodiversity information, described the revival story of hilsa and other important fish along with the threats and challenges of the fish biodiversity and suggested measures for the sustainable management of the fish biodiversity. Freshwater habitats are rich in biodiversity with 265 fresh water fish species. The Meghna River supports the highest 200 fish species as a single river. The marine habitat covers an area of 118,813 km2 that produces 0.66 million tons of fish annually and owned 475 species in 1971, but recent exploration suggests the existence of 394 species. However, the species diversities are increasingly facing threats from direct and indirect anthropogenic activities including juvenile catch, overexploitation, creating obstructions in the migratory routes, pollutions and climate change. Hilsa, the most important species also severely faced these threats and as a result, the production declined to below 0.20 million tons in 2002-2003. Joint efforts of all stakeholders through incentive based co-management led to the hilsa fishery revival, and its production reached 0.533 million tons in 2019. Along with the hilsa, other interdependent species, especially four important catfish species ( Pangasius pangasius, Sperata aor, Bagarius bagarius and Rita rita ) have also revived remarkably. Following the lessons learned from the revival of fishery, several management measures focusing on juvenile conservation, protection of broodstock, harmful gear elimination, optimum exploitation, pollution control, incentive-based co-management, habitat protection, restoration and rehabilitation are suggested to ensure maximum sustainable productions and biodiversity conservation focusing on vulnerable and threatened species and improved livelihoods resilience of fishers through good governance.

Landscape diversity vs. population resilience of a wetland species near the limits of its range (the root vole Microtus oeconomus in Poland) – Implications for species conservation

Loss of connectivity between habitat patches is particularly important for small, environmentally specialized species with short migratory capacity. Taking the root vole as an example, we studied whether variation in the landscape (its geomorphological evolution) may affect the genetic differentiation exhibited by a wetland species, and thus the resilience of its population. We did so by testing the genetic differentiation at 9 sites located in two areas in the peripheral zone of the root vole’s range limit in Poland (the Sandomierz Basin and Western Polesie), and confronted the results with the differing origins and geomorphological characteristics of the hydrogenic environments in those two areas. Based on the analyses of 12 microsatellite loci (N = 118) and the 908 bp of cytochrome b sequences (N = 107), higher genetic variability was found in individuals from Western Polesie than from the Sandomierz Basin. Geomorphological analysis conducted with the use of DTM, satellite images, geological maps and cartographic fieldwork showed that the habitats optimal for the root vole are configured differently in the two areas considered, occurring mainly in river valleys and in isolated wetlands of lake-land plains, respectively. Simultaneous analysis of both the spatial configuration and connectivity of habitats, and the voles’ evolutionary directions and genetic parameters, supports the conclusion that the linear character of highly fragmented riverine habitats, additionally inundated during episodic flooding, is less favorable for the gene dispersal of small mammals than extensive marshy wetlands, even despite locally occurring barriers. These findings indicate that the genesis and geomorphological evolution of the landscape may influence the ecological changes taking place there, including habitat reduction and fragmentation. They may therefore be important for the persistence/resilience of particular species and therefore should be taken into account in conservation management of hydrogenic habitat areas, especially those close to the range limit of species with demanding habitat requirements.

Life at the borderline: Responses of Ganges river dolphins to dry‐season flow regulation of river and canal habitats by the Farakka barrage

Abstract Modification of river flows by dams and barrages has fragmented riverine habitats and threatened the survival of Indian subcontinental river dolphins. In this study, habitat use by endangered Ganges river dolphins in response to dry‐season operations (December‐March) of the Farakka barrage on the Ganga River, located about 20 km upstream of the India–Bangladesh border, was assessed. Ten surveys were conducted in: (i) the Ganga River below the barrage, where rapid changes in water levels were expected owing to barrage operations; (ii) the Farakka feeder canal with stable water levels; and (iii) the Hooghly River downstream of the canal. Dolphin distribution, water depth, fishing boat count and temperature were recorded in all surveys and the data were analysed in a dynamic occupancy modelling framework. Temporal trends in river discharge, primary productivity and fish availability were also estimated to explain river dolphin responses. Occupancy and colonization by dolphins increased in all stretches by spring/March, correlated with rising water temperature and increased fishing intensity, which was related to upstream migration of hilsa fish. In the Ganga River, dolphin occupancy in deep river pools remained stable, but resulted in increased overlap with fisheries as river flow declined. The feeder canal, with stable flows, witnessed increased colonization by dolphins, but also greater risk of bycatch in fishing nets. The canal that appeared as a hydrological refuge thus became an ‘ecological trap’. The findings highlight the need for integration of flow maintenance and fishery regulations in the monitoring and management of canals as effective refuges for riverine species. We advocate the inclusion of ecological flow criteria and fishery regulations to reduce dolphin bycatch mortality, in the context of establishing river dolphin conservation plans and transboundary water‐sharing guidelines. The revision of the India–Bangladesh water‐sharing treaty in 2026 could incorporate the above considerations.

An assessment of marine, estuarine, and riverine habitat vulnerability to climate change in the Northeast U.S.

Climate change is impacting the function and distribution of habitats used by marine, coastal, and diadromous species. These impacts often exacerbate the anthropogenic stressors that habitats face, particularly in the coastal environment. We conducted a climate vulnerability assessment of 52 marine, estuarine, and riverine habitats in the Northeast U.S. to develop an ecosystem-scale understanding of the impact of climate change on these habitats. The trait-based assessment considers the overall vulnerability of a habitat to climate change to be a function of two main components, sensitivity and exposure, and relies on a process of expert elicitation. The climate vulnerability ranks ranged from low to very high, with living habitats identified as the most vulnerable. Over half of the habitats examined in this study are expected to be impacted negatively by climate change, while four habitats are expected to have positive effects. Coastal habitats were also identified as highly vulnerable, in part due to the influence of non-climate anthropogenic stressors. The results of this assessment provide regional managers and scientists with a tool to inform habitat conservation, restoration, and research priorities, fisheries and protected species management, and coastal and ocean planning.

Palaeoshoreline reconstruction and underwater archaeological potential of Liman Tepe: A long-occupied coastal prehistoric settlement in western Anatolia, Turkey

Rising post-glacial sea levels had a major influence on the prehistoric settlement of the Aegean coastal zone. At Liman Tepe, an important Chalcolithic-Bronze Age coastal settlement on the south coast of the Bay of Izmir, archaeological evidence suggests a Neolithic (ca. 9600-5500 BCE) presence, but no settlement has been discovered on land. Sea levels during the Neolithic period were between 6 and >20 m below present and there is high potential for discovery of submerged prehistoric sites. Marine sediment coring and geophysical investigations (bathymetry, sub-bottom seismic profiling; >600 line-km) were conducted over a 4-km2 inshore area to assess the underwater archaeological potential. Multi-proxy sediment analysis (sedimentary facies, micropalaeontology, micro-XRF geochemistry) was conducted on 20 cores to reconstruct the relative sea level (RSL) history and coastal palaeogeography. Palaeoshoreline positions were estimated by back-stripping of the decompacted sediment thickness from a digital bathymetric model (DBM).The DBM reveals a drowned middle Holocene coastal plain with well-preserved relict river channels, palaeoshorelines and coastal headlands. The inshore stratigraphy consists of shoreface, foreshore and lagoonal deposits overlying terrestrial clay and palaeosols, defining a marine transgressive surface (MTS). The MTS records the inundation of the coastal plain prior to ca. 4000 BCE (transgressive systems tract; TST) and is marked in cores by an increasing abundance of foraminifera and a rise in Ca/Ti. During the Early Neolithic (ca. 6700 BCE), the shoreline was >500 m seaward (RSL ∼ −14 to −16 m) and Karantina Island was a broad coastal headland with a sheltered western embayment. By the Middle Chalcolithic (ca. 4800 BCE), the coastline had transgressed ∼800 m inland of the present shoreline and the Liman Tepe headland was separated from the mainland by a shallow coastal wetland. The maximum transgression (∼1 km inland at ca. 4000 BCE) was followed by a shift to a high-stand systems tract (HST) and rapid coastline progradation by barrier accretion and lagoon development. Palaeogeographic maps identify areas with high underwater archaeological potential: 1) palaeoriver channels and lowland riverine habitats formed during the TST, prior to 4000 BCE, 2) submerged palaeoshorelines and coastal promontories (water depths 10–14 mbsl) with high potential for Neolithic sites, and 3) protected coastal embayments and lagoons representing possible prehistoric anchorage sites.

Diversity and activity of bird fauna in ephemeral river-created habitats in Amazonia

ABSTRACT Seasonal changes in runoff and inundation create river-habitats that are considered key to the diversity of Amazonian bird species. However, studies on avifauna in different riverine habitats remain scarce. We used camera traps to survey the avifauna in river-created habitats along 39 km of river in the eastern Brazilian Amazon. We examined the number of bird species detected and species composition in islands and margin banks, evaluated species–area relationships in these two habitats, and examined if the most abundant bird species have differences in activity pattern between habitats. Cameras recorded 21 bird species from 13 families (Accipitridae, Ardeidae, Bucconidae, Caprimulgidae, Cathartidae, Columbidae, Cracidae, Hirundinidae, Icteridae, Scolopacidae, Thraupidae, Threskiornithidae, and Tyrannidae). Species composition did not differ between habitat types but we found a discernible area effect, explaining as much as 84% on the number of species detected across island sites. Overlaps of activity pattern of bird species were high between habitat types, but differences in activity peaks were found for Molothrus oryzivorus and Pitangus sulphuratus while examining islands and margin banks. River-created habitats are relevant to Amazonian bird diversity and studies on these habitats must be increased to better understand their value across the Amazon.

Hydraulic Properties of the Riffle Crest and Applications for Stream Ecosystem Management

AbstractRiffle crests are important hydraulic controls in riffle‐pool‐dominated streams, influencing pool hydraulics and water quality that collectively control lotic habitat for many organisms. We define a simple stream depth measurement, the riffle crest thalweg (RCT), describe measurement methods and utility, and suggest that RCT depth is a better independent variable than streamflow (Q) for many instream flow and habitat assessment applications. Using RCT depth as an independent variable, rather than streamflow, reduces the need for gauging or streamflow measurements in many management applications. Unlike streamflow, RCT depth varies directly with fundamental elements of riverine habitat such as channel morphology and bed roughness. We also suggest that relationships between RCT depth and streamflow (RCT‐Q curves) can be used to evaluate the risk of streamflow alteration at ungauged sites. We describe three case studies to demonstrate the utility of RCT depth and RCT‐Q rating curves in stream ecosystem management: (1) evaluating the effect of a top‐down flow prescription on modeled salmonid habitat, (2) estimating the risk from the incremental reduction of RCT depth on habitat and ecological responses, and (3) identifying relationships between RCT depth and dissolved oxygen in ungauged streams. An easy‐to‐measure, inexpensive, and ecologically sensitive metric, RCT depth holds promise as a useful tool in stream ecosystem management.

Japanese Hops (Humulus japonicus) Control and Management Strategies in Large River Floodplains

AbstractJapanese hops (Humulus japonicus) is an invasive vine that establishes in open areas in riverine habitats and suppresses tree regeneration and native vegetation. This study evaluated the use of herbicides and tree plantings to control and manage Japanese hops on five Mississippi River islands over a four-year period. Herbicide treatments included a preemergent (sulfometuron methyl), a postemergent (glyphosate), and a combination of both. Tree plantings used containerized and bareroot American sycamore (Platanus occidentalis) and eastern cottonwood (Populus deltoides) trees. Japanese hops biomass was significantly lower in all herbicide treatments in 2012 and 2015, but the preemergent treatment was less effective than other treatments in 2012 and 2014. After two years, average survivorship of containerized trees was 20%–42%, whereas bareroot seedlings had near 100% mortality. Results indicate that postemergent treatments are effective for short-term control, but large floods reestablish Japanese hops in treated areas. Reforestation, if combined with herbicide treatments and active management, may be a promising approach in large river floodplains that experience frequent flooding, but low tree survivorship presents challenges to reforestation.

Myxozoan parasites vary in river herring according to life history stage and habitat.

Anadromous river herring have declined in many parts of their range, leading to fisheries management efforts to help repopulate this species by improving connectivity of rivers and restoring populations by fish transfers. With data lacking on parasites in these species, this study sought to better understand myxozoans across various life stages and habitats in river herring populations in New Jersey, USA. We compared fish from riverine habitats during early-life growth and adults returning to spawn, marine-phase fish, and landlocked Alewife populations. Three myxozoan species were identified in young-of-the-year (YOY) anadromous river herring, including Kudoa clupeidae in the skeletal musculature, Myxobolus mauriensis in the rib cartilage, and an uncharacterized coelozoic myxozoan within the lumen of mesonephric tubules. In YOY river herring, Blueback Herring were 2 times more likely to be infected by K. clupeidae than Alewife (p = 0.019) and in the Maurice River, fish were 4 times more likely to be infected with M. mauriensis than fish from Great Egg Harbor River (p = 0.000) and 11 times more likely than the Delaware River (p = 0.001). Spawning adult river herring were infected with a previously undescribed myxozoan parasite infecting the kidney. Sequencing the 18S rDNA indicated this species is closely related to Ortholinea species. Myxobolus mauriensis and the Ortholinea-like species were absent from marine-phase river herring indicating that infections were linked to river environments occurring during early-life growth and spawning, respectively. No myxozoans were present in landlocked Alewife, showing that similar infections occurring in rivers were absent in lake environments in the region.

Development of a Multilayer Deep Neural Network Model for Predicting Hourly River Water Temperature From Meteorological Data

Water temperature is a vital attribute of physical riverine habitat and one of the focal objectives of river engineering and management. However, in most rivers, there are not enough water temperature measurements to characterize thermal regimes and evaluate its effect on ecosystem functions such as fish migration. To aid in river restoration, machine learning-based algorithms were developed to predict hourly river water temperature. We trained, validated, and tested single-layer and multilayer linear regression (LR) and deep neural network (DNN) algorithms to predict water temperature in the Los Angeles River in southern CA, United States. For the single-layer models, we considered air temperature as the predictive feature, and for the multilayer models, relative humidity, wind speed, and barometric pressure were included in addition to air temperature as the considered features. We trained the LR and DNN algorithms on Google’s TensorFlow model using Keras artificial neural network library on Python. Results showed that multilayer predictions performed better compared to single-layer models by producing mean absolute errors (MAEs), that were 20% smaller (1.05°C), on average, compared to the single-layer models (1.3°C). The multilayer DNN algorithm outperformed the other model where the model’s coefficient of determination was 26 and 12% higher compared to the single-layer LR (the base model) and multilayer LR model, respectively. The multilayer machine learning algorithms, under proper data preparation protocols, may be considered useful tools for predicting water temperatures in sampled and unsampled rivers for current conditions and future estimations affected by different stressors such as climate and land-use change. River temperature predictions from the developed models provide valuable information for evaluating sustainability of river ecosystems and biota.

Viviparity and habitat restrictions may influence the evolution of male reproductive genes in tsetse fly (Glossina) species

BackgroundGlossina species (tsetse flies), the sole vectors of African trypanosomes, maintained along their long evolutionary history a unique reproductive strategy, adenotrophic viviparity. Viviparity reduces their reproductive rate and, as such, imposes strong selective pressures on males for reproductive success. These species live in sub-Saharan Africa, where the distributions of the main sub-genera Fusca, Morsitans, and Palpalis are restricted to forest, savannah, and riverine habitats, respectively. Here we aim at identifying the evolutionary patterns of the male reproductive genes of six species belonging to these three main sub-genera. We then interpreted the different patterns we found across the species in the light of viviparity and the specific habitat restrictions, which are known to shape reproductive behavior.ResultsWe used a comparative genomic approach to build consensus evolutionary trees that portray the selective pressure acting on the male reproductive genes in these lineages. Such trees reflect the long and divergent demographic history that led to an allopatric distribution of the Fusca, Morsitans, and Palpalis species groups. A dataset of over 1700 male reproductive genes remained conserved over the long evolutionary time scale (estimated at 26.7 million years) across the genomes of the six species. We suggest that this conservation may result from strong functional selective pressure on the male imposed by viviparity. It is noteworthy that more than half of these conserved genes are novel sequences that are unique to the Glossina genus and are candidates for selection in the different lineages.ConclusionsTsetse flies represent a model to interpret the evolution and differentiation of male reproductive biology under different, but complementary, perspectives. In the light of viviparity, we must take into account that these genes are constrained by a post-fertilization arena for genomic conflicts created by viviparity and absent in ovipositing species. This constraint implies a continuous antagonistic co-evolution between the parental genomes, thus accelerating inter-population post-zygotic isolation and, ultimately, favoring speciation. Ecological restrictions that affect reproductive behavior may further shape such antagonistic co-evolution.

Tracking microeukaryotic footprint in a peri-urban watershed, China through machine-learning approaches

Microeukaryotes play a significant role in biogeochemical cycling and can serve as bioindicators of water quality in freshwater ecosystems. However, there is a knowledge gap on how freshwater microeukaryotic communities are assembled, especially that how terrestrial microeukaryotes influence freshwater microeukaryotic assemblages. Here, we used a combination of 18S rRNA gene amplicon sequencing and community-based microbial source tracking (MST) approaches (i.e., SourceTracker and FEAST) to assess the contribution of microeukaryotes from surrounding environments (i.e., soils, river sediments, swine wastewater, influents and effluents of decentralized wastewater treatment plants) to planktonic microeukaryotes in the main channel, tributaries and reservoir of a peri-urban watershed, China in wet and dry seasons. The results indicated that SAR (~ 49% of the total communities), Opithokonta (~ 34%), Archaeplastida (~ 9%), and Amoebozoa (~ 2%) were dominant taxa in the watershed. The community-based MST analysis revealed that sewage effluents (7.96 – 21.84%), influents (2.23 – 13.97%), and river sediments (2.56 – 11.71%) were the major exogenous sources of riverine microeukaryotes. At the spatial scale, the downstream of the watershed (i.e., main channel and tributaries) received higher proportions of exogenous microeukaryotic OTUs compared to the upstream reservoirs, while at the seasonal scale, the sewage effluents and influents contributed higher exogenous microeukaryotes to river water in wet season than in dry season. Moreover, the swine and domestic wastewater led to the presence of Apicomplexa in wet season only, implying rainfall runoff may enhance the spread of parasitic microeukaryotes. Taken together, our study provides novel insights into the immigration patterns of microeukaryotes and their dominant supergroups between terrestrial and riverine habitats.

Depositional patterns of slowly plugging neck cutoffs from core analysis and estimates of bedload transport, White River, Arkansas

AbstractMeander cutoffs and oxbow lakes are very common features of fluvial landscapes that add complexity and diversity to floodplain alluvial architecture and riverine habitats. Following initial cutoff, sediment accumulates within the entrance and exit of the original bend forming plugs that eventually disconnect the abandoned bend from the main channel. While studies have examined the sedimentology of these plugs once they have fully disconnected from the abandoned bend, fewer studies have detailed the sedimentological processes occurring during the early stages following cutoff initiation. Furthermore, recent studies have highlighted the importance that planform geometry plays in the evolution of neck cutoffs. This study examines the spatial depositional patterns of two neck cutoffs on the White River in central Arkansas, USA, that remain hydrologically connected to the main channel, providing a unique opportunity to research sedimentological processes before disconnection of the abandoned bend. Sediment cores were collected in key locations of each cutoff, including the entrance and exit of the abandoned bends, abandoned bend apices, and newly developed cutoff bars in the downstream channel. The cores were logged and interpreted and grain‐size analyses were performed. In addition to sediment cores, repeat high‐resolution multibeam echo sounding surveys were conducted roughly four hours apart to estimate bedload transport rates and patterns of bedload routing through each cutoff. Results from this research are different from previous studies. Sediment core results show a pattern of deposition typically associated with lower diversion angle chute cutoffs instead of higher diversion angle neck cutoffs. Previous research has indicated that plugging of abandoned bends drives disconnection from the active channel; however, this research shows that disconnection is more associated with the prevention of sediment from being delivered to the abandoned bends due to flow being pulled away from the abandoned bends and the evolving channel morphology.

Redescription of Sartoriana trilobata (Alcock, 1909) (Crustacea: Decapoda: Brachyura: Gecarcinucidae) from Assam, Northeast India, with notes on the morphology of male gonopods.

Sartoriana trilobata is a species of freshwater crab which occurs exclusively in some areas of Northeast India. Being a riverine crab, it is occasionally found in beels or other riverine wetland habitats formed by monsoon floods in the Brahmaputra basin.The earlier descriptions of this species were mostly incomplete which lacked information on the morphology of the male gonopods.Therefore including the male gonopods, all the morphological features of Sartoriana trilobata are redescribed and illustrated. This species differs considerably from its only congener i.e., Sartoriana spinigera through suits of carapace, chelipeds, gonopods dissimilarities.

Characterisation of breeding habitat of Grizzled Giant Squirrel Ratufa macroura (Mammalia: Sciuridae) in Chinnar Wildlife Sanctuary, Western Ghats, India

The Grizzled Giant Squirrel (GGS) Ratufa macroura (Pennant, 1769) is a ‘Near Threatened’ and endemic giant squirrel distributed in southern India and Sri Lanka. In India, the species is distributed in more than 10 locations between Cauvery Wildlife Sanctuary in Karnataka in the north and Srivilliputhur Grizzled Squirrel Wildlife Sanctuary in Tamil Nadu in the south. A study was conducted in the riparian habitats of Chinnar Wildlife Sanctuary in Kerala to understand the habitat characteristics, including the drey site use of GGS. The vegetation of the GGS habitat was studied using the quadrat method, and the dreys were counted using the transects. A total of 95 species of trees were identified from the riverine vegetation, and the GGS used 36 species of trees for drey construction. Most of the dreys were found on Mangifera indica, Terminalia arjuna, Ficus microcarpa, Diospyros ebenum, and Pongamia pinnata. However, the GGS may prefer trees such as Mitragyna parviflora, Diospyros ebenum, Ficus microcarpa, Albizia procera, Acacia nilotica, and Acacia leucophloea for drey construction. The study also highlights the usage of large trees with extensive crown by the GGS for various activities such as feeding, resting, moving, and nesting, thus signifying the necessity for protecting the remaining riverine habitat at Chinnar Wildlife Sanctuary to ensure the long-term conservation of GGS. We recommend an urgent restoration by restocking with already existing, native tree species of the riverine habitat due to the extremely poor regeneration of trees in the riverine habitat that support the only population of the GGS in Kerala.

Vegetation survey of the Khomas Hochland in central-western Namibia: syntaxonomical descriptions

Background: The Great Escarpment of southern Africa takes the form of an extended mountainous highland in central-western Namibia, commonly referred to as the ‘Khomas Hochland’. It is regarded as an area of high botanical diversity. Yet only few localised studies on the vegetation composition are available. The Khomas Hochland is formed on the southern part of the Damara Orogen and dominated by metamorphosed sediments. Climatically it forms a transition between the hot desert of the Namib and the slightly cooler hot steppe in the inland.Objectives: To classify and provide syntaxonomical descriptions of the vegetation of the Khomas Hochland.Methods: A dataset comprising 1151 relevés and 914 species was compiled from various surveys, mostly collected under, and to the standards of, the umbrella project ‘Vegetation Survey of Namibia’. For first classifications, the data set was reduced to a synusial set consisting of trees, shrubs, dwarf shrubs and grasses only.Results: The classification resulted in four major landscape units, being the Pre-Namib and Escarpment zone, the Khomas Hochland proper, riverine habitats as well as surrounding lowlands. The classification was further refined using Cocktail procedures to produce 30 associations, one with four sub-associations. These are described in this paper.Conclusion: A classification of synoptic data grouped the associations into five orders and one undefined cluster of associations on specialised desert habitats. Four of these orders correspond to the habitat types identified in the first classification. The fifth order, the Senegalio hereroensis–Tarchonanthoetalia camphorathi, represents high mountains of the central Khomas Hochland, which link biogeographically to the grassland biome in South Africa.

Comparing diversification rates in lakes, rivers, and the sea.

The diversity of species inhabiting freshwater relative to marine habitats is striking, given that freshwater habitats encompass <1% of Earth's water. The most commonly proposed explanation for this pattern is that freshwater habitats are more fragmented than marine habitats, allowing more opportunities for allopatric speciation and thus increased diversification rates in freshwater. However, speciation may be generally faster in sympatry than in allopatry, as illustrated by lacustrine radiations such as African cichlids. Such differences between rivers and lakes may be important to consider when comparing diversification broadly among freshwater and marine groups. Here I compared diversification rates of teleost fishes in marine, riverine and lacustrine habitats. I found that lakes had faster speciation and net diversification rates than other aquatic habitats. However, most freshwater diversity arose in rivers. Surprisingly, riverine and marine habitats had similar rates of net diversification on average. Biogeographic models suggest that lacustrine habitats are evolutionarily unstable, explaining the dearth of lacustrine species in spite of their rapid diversification. Collectively, these results suggest that strong diversification rate differences are unlikely to explain the freshwater paradox. Instead, this pattern may be attributable to the comparable amount of time spent in riverine and marine habitats over the 200-million-year history of teleosts.

Listen But Do Not Touch: Using a Smartphone Acoustic Device to Investigate Bat Activity, with Implications for Community-Based Monitoring

The monitoring of bats across the world is mostly conducted using invasive mist-netting, whereby vertical nets are placed to capture bats mid-flight. Many studies have demonstrated how this approach causes sampling bias, is labor-intensive and increases the risk of white-nose syndrome fungus, Pseudogymnoascus destructans, transmission among bats. Increasingly, acoustic devices are being employed to collect data on bat activity and richness. Community-based monitoring is an important data collection source for bat monitoring programs in countries such as the UK (National Bat Monitoring Program), whereby walking bat transects are conducted using bat detectors. Since the launch of smartphone devices to record and auto-identify bat echolocation calls, the quality of data collection that community members can collect has increased significantly, however, this approach is seldom used to generate data in scientific studies. In our study, we have showcased how our study design paired with state of the art acoustic monitoring devices, can be applied to community-based monitoring of bats across the world. Through employing smartphone acoustic devices, we have determined how primary and secondary vegetation cover are predictors of bat species occurrence and identified the importance of riverine and deciduous swamp habitats for rare bat species in southwestern Ontario.