Feeding ecology and ecomorphology of cichlid assemblages in a large Mesoamerican river delta

Fish assemblages in tropical lowland rivers are characterized by a high richness of species that feed on a diverse array of food resources. Although closely related species often have similar feeding ecology, species within the family Cichlidae display a broad spectrum of trophic niches, and resource partitioning has been inferred from studies conducted in Neotropical rivers. We investigated interspecific variation in food resource use and its relationship to morphological variation among cichlid fishes within the Pantanos de Centla Biosphere Reserve, a coastal area encompassing the delta of the Grijalva-Usumacinta River in Tabasco, Mexico. Most species consumed benthic crustaceans, aquatic insect larvae, and detritus, but some were more herbivorous, and one species was a specialized piscivore. Dietary niche overlap among species was higher than expected for one assemblage, and similar to random expectations for another, suggesting a lesser role for resource partitioning than has been shown for some cichlid assemblages, perhaps due to availability of abundant resources, even in low-water conditions. Canonical correspondence analysis revealed that greatest morphological differences am7ong species involved functional traits directly associated with resource use. Relationships between feeding ecology and morphology were similar to those described for other riverine cichlids. Strong ecomorphological relationships facilitate inferences about the ecology of cichlid species, including species that currently lack data from field studies. Knowledge of ecological relationships will be important for conservation in the Pantanos de Centla, an ecosystem of global significance for biodiversity and ecosystem services.     

Cystoopsis atractostei n. sp. (Nematoda: Cystoopsidae) from the subcutaneous tissue of the tropical gar,Atractosteus tropicus (Pisces), in Mexico

A new species of parasitic nematode, Cystoopsis atractostei (Trichinelloidea: Cystoopsidae), is described based on female specimens recovered from the subcutaneous tissue of the tropical gar, Atractosteus tropicus Gill (Lepisosteiformes: Lepisosteidae), from 2 localities (Canal Nueva Esperanza and Canal Tabasquillo) of the Pantanos de Centla Biological Reserve, State of Tabasco, southeastern Mexico, collected in April 2001. The total prevalence was 13%, and the mean intensity of infection was 1 nematode per fish. The new species differs from females of the only other adequately described congeneric species, C. acipenseris Wagner, 1867, mainly in possessing a bulbous inflation at the anterior end of the muscular esophagus, the vulva situated well posterior to the nerve ring, smooth cuticle, and in the shape of the posterior vesicular portion of the body (markedly transversely oval) in the largest specimens. Both species also differ in their host types (Lepisosteiformes vs. Acipenseriformes) and in geographical distribution (tropical southern Mexico vs. temperate zones of the Holarctic).     

Helminth parasites of the tropical gar, Atractosteus tropicus Gill, from Tabasco, Mexico

A total of 8 helminth species were recorded in an examination of 43 tropical gar, Atractosteus tropicus Gill, collected at the Pantanos de Centla Biosphere Reserve, Tabasco, Mexico. The parasite species included 1 adult trematode, 3 metacercariae, 1 cestode, 1 adult nematode, and 2 nematode larvae. Six of these 8 species were rare, with low prevalence (< 17%) and abundance (< 1.0 helminths per examined fish). The larvae of Contracaecum sp. were the most abundant in the sample, constituting 60% of the total helminths (64% prevalence, 3.8 +/- 5.2 abundance), followed by the cestode Proteocephalus singularis, constituting 18% of the worms (30.5% prevalence, 1.1 +/- 3.0 abundance). Species richness, individual parasite abundance, and diversity were low in the infracommunities. The recording of 3 specialist species in the tropical gar confirms that the helminth fauna of gar has an appreciable degree of specificity. This study indicates the importance of ecological determinants of richness in helminth communities of the tropical gar.     

The Orange River avifauna: abundance,richness and comparisons

Like many other southern African rivers, the avifaunal richness and abundance of the Orange River, southern Africa's longest, remains virtually unknown. Given that the Orange River runs through hyper-arid regions in its lower reaches, its linear oasis effect and its role as a reservoir for Red Data bird species is likely but has not been quantified. Two surveys either side of the border town of Noordoewer, in the rainy and dry seasons of 1996 and 1997 deter-mined that species richness was higher in riverine habitat (71 species) than in the surrounding Nama Karoo (46 species) confirming the linear oasis effect. Surveys revealed five Namibian Red Data species. Peregrine Falcons, Falco peregrinus, and African Fish Eagles, Haliaeetus vocifer, were relatively common while the endangered Cape Eagle Owl, Bubo capensis, occurred sporadically. Among wetland Red Data bird species, Black Storks, Ciconia nigra, occurred in less disturbed areas, and White-backed Night Herons, Gorsachius leuconotus, were an unexpected species at this locality. The overall species richness of 103 birds and a density of riparian birds of 31 -3 4 birds/10 km, makes the lower Orange River avifauna similar to the Cunene River but tenfold less abundant than Namibia's other perennial rivers. Despite the low diversity, the arid habitats of the lower Orange River support greater diversity than more easterly regions when all current surveys of richness and abundance from Lesotho to the mouth on the Namib coast are combined. This east-west trend may be explained by the slower flow and warmer water of the lower Orange River but natural turbidity and regulation may explain the generally low diversity and abundance indices. Major rivers in southern Africa appear to have been over-looked as wetland habitats, and further avifaunal surveys of all of them are recommended.     

Relationship Between Avifaunal Occupancy and Riparian Vegetation in the Central Great Basin (Nevada, U.S.A.)

In western North America, riparian vegetation is being lost in response to changes in land use and climate. We examined the relationship between obligate riparian species of songbirds and environmental and riparian habitat factors in three mountain ranges in the central Great Basin (Nevada, U.S.A.). We estimated patterns of occupancy, colonization, and local extinction for three species detected during the breeding seasons of 2001–2006: MacGillivray's Warbler ( Oporornis tolmiei ), Broad-tailed Hummingbird ( Selasphorus platycercus ), and Song Sparrow ( Melospiza melodia ). We used model selection and multimodel inference to identify functional relationships between the occupancy of each species and multiple habitat variables, including the structure and composition of riparian vegetation. Among all years and species, we observed considerable variation in estimates of detection probability. For MacGillivray's Warbler, annual occupancy rates were relatively constant. Occupancy rates for Broad-tailed Hummingbird and Song Sparrow increased during the first 3–4 years of our study and then decreased. Each species experienced its highest rate of local extinction during 2005. Different components of riparian vegetation were good predictors of occupancy, colonization, and local extinction for each species. Typically, elevation and latitude also were strong predictors. Establishing functional relationships between avifauna and vegetation is essential to predicting how land-cover change may affect the occupancy of riparian areas and other habitats for birds. The conservation of breeding birds in riparian areas in the central Great Basin is more likely to succeed if the quality of their understory habitat as well as the canopy is maintained and restored.     

Lizard assemblages in the Vizcaino Biosphere Reserve, Mexico

Lizard assemblages were surveyed in eight selected habitats in the Vizcaino Biosphere Reserve in Baja California Sur, Mexico. We compared the species composition and relative abundance among habitats, considering habitat characteristics, such as vegetation type, vegetation ground coverage, and soil types. Thirteen lizard species were recorded. The most abundant species in almost all habitats was Uta stansburiana, accounting for 59% of all observations. Cnemidophorus tigris was the second most abundant species, accounting for 12% of all observations. The richest habitat was the rocky lower elevations of the Sierra de San Francisco (nine species). However, the habitat with the highest diversity value was Scammon's dunes. Implications of our findings for lizard conservation in this biosphere reserve are discussed.     

Seasonal abundance and habitat use of bird species in and around Wondo Genet Forest,south‐central Ethiopia

The habitat use and seasonal migratory pattern of birds in Ethiopia is less explored as compared to diversity studies. To this end, this study aimed at investigating the patterns of distribution related to seasonality and the effect of habitat characteristics (elevation, slope, and average vegetation height) on habitat use of birds of Wondo Genet Forest Patch. A stratified random sampling design was used to assess the avian fauna across the four dominant habitat types found in the study area: natural forest, wooded grassland, grassland, and agroforestry land. A point transect count was employed to investigate avian species richness and abundance per habitat type per season. Ancillary data, such as elevation above sea level, latitude and longitude, average vegetation height, and percent slope inclination, were recorded with a GPS and clinometers per plot. A total of 33 migratory bird species were recorded from the area, of which 20 species were northern (Palearctic) migrants while 13 were inter‐African migrants. There was a significant difference in the mean abundance of migratory bird species between dry and wet seasons (t = 2.13, p = .038, df = 44). The variation in mean abundance per plot between the dry and wet seasons in the grassland habitat was significant (t = 2.35, p = .051, df = 7). In most habitat types during both dry and wet seasons, omnivore birds were the most abundant. While slope was a good predictor for bird species abundance in the dry season, altitude and average vegetation height accounted more in the wet season. The patch of forest and its surrounding is an important bird area for migratory, endemic, and global threatened species. Hence, it is conservation priority area, and the study suggests that conservation coupled with ecotourism development is needed for its sustainability.     

Occupancy and demographics of red river hog Potamochoerus porcus on Tiwai Island,Sierra Leone

The red river hog (Potamochoerus porcus, Linnaeus) is a species of Suidae with populations ranging from western to central Africa. Little is known about the population status of red river hog, and few studies have investigated habitat characteristics associated with their occupancy which is critical in determining possible reasons behind suspected population declines. We used camera traps and site occupancy models to examine the effects of habitat covariates on occupancy of red river hog on Tiwai Island and in surrounding forests of Sierra Leone during two field seasons, 2008–2011. We also estimated group size and composition and growth patterns of juveniles. In both sampling periods, understory vegetation strongly influenced red river hog occupancy with greatest association with riparian and swamp vegetation types. Red river hogs seemed to avoid habitats of high human impact such as farmbush and secondary growth forests. Average group size was 2.46 ± 0.28 (SE) hogs per group. Growth patterns of juveniles suggested the majority of piglets were born during the middle of dry season (January–February). Our research suggests landscape use by red river hog is influenced by presence of riparian habitats with dense vegetation.     

新疆卡拉麦里山有蹄类野生动物自然保护区啮齿动物群落多样性及其与环境因子的关系

啮齿动物的群落结构受生态环境特征影响,并能反映环境变化规律。为探讨啮齿动物群落多样性及其与环境因子间的关系,利用铗捕法获得了新疆卡拉麦里山有蹄类野生动物自然保护区9种生境类型的环境因子及啮齿动物群落结构数据。2019-2020年春、夏季,共布设样地291块,有效铗日55269个,调查总面积176.875 km²,记录了啮齿类分布的12个环境因子。捕获啮齿动物419只,分属1目4科10属12种,优势种为三趾跳鼠（Dipus sagitta）和五趾跳鼠（Allactaga sibirica）,分别占捕获总个体数的34.13%和27.68%。分析结果显示,卡山自然保护区啮齿类捕获率最高的生境类型为沙漠（2.18%）;捕获鼠种的主要分布型为耐旱型（98.09%）。12个环境因子在9个生境类型中均呈极显著差异（P<0.01）,说明该保护区啮齿动物分布的生境异质性高。冗余分析表明,海拔高度、植被种类、灌木盖度和灌木高度是决定啮齿动物群落结构最主要的4个环境因子,其中植被种数与啮齿类群落多样性呈正相关,随着植被种数数值的增加,除优势度指数外,其它多样性指数随之增加。     

Forest cover and heterogeneous pastures shape the diversity of predatory rove beetles in tropical riparian habitats

In tropical landscapes, forest remnants have been reduced to narrow strips of vegetation along rivers and streams surrounded by agricultural land that affects biodiversity, depending on the habitat and landscape characteristics. To assess the effect of riparian forest loss on the diversity of Staphylininae predatory rove beetles, we considered two habitat conditions (river sites with riparian vegetation and sites with heterogeneous pastures) within two micro-basin types (with >70% and <40% forest cover) in a tropical montane cloud forest landscape, Mexico. Beetles were collected using baited pitfall traps during the rainy season of 2014. No differences were found between micro-basin types and, although species richness (⁰D) was similar between habitat conditions, when the diversity of common (¹D) and dominant (²D) species was considered, sites with heterogeneous pastures were almost twice as diverse as those with riparian vegetation. All diversity measurements were greater in sites with heterogeneous pastures of either micro-basin type. Air temperature and canopy cover were the environmental variables that best explained the variation in beetle species composition. The greatest environmental differences related to species composition were detected between habitat conditions and were more evident in sites with heterogeneous pastures and low forest cover in the surroundings. The results suggest that replacing riparian vegetation with heterogeneous pastures, within micro-basins that lost between 30% and 60% of their forest cover, does not significantly reduce the diversity of predatory rove beetle but rather modifies the beetle composition. Effective formulation of management strategies to mitigate the impact of land use modification therefore requires an understanding of the interaction between vegetation remnants and landscape characteristics.     

Limited Effects of Large‐Scale Riparian Restoration on Seed Banks in Agriculture

I examined the effect of riparian forest restoration on plant abundance and diversity, including weed species, on agricultural lands along the Sacramento River in California (United States). Riparian forest restoration on the Sacramento River is occurring on a large‐scale, with a goal of restoring approximately 80,000 ha over 160 km of the river. In multiuse habitats, such as the Sacramento River, effects of adjoining habitat types and movement of species across these habitats can have important management implications in terms of landscape‐scale patterns of species distributions. Increased numbers of pest animals and weeds on agricultural lands associated with restored habitats could have negative economic impacts, and in turn affect support for restoration of natural areas. In order to determine the distribution and abundance of weeds associated with large‐scale restoration, I collected seed bank soil samples on orchards between 0 and 5.6 km from adjacent restored riparian, remnant riparian, and agricultural habitats. I determined the abundance, species richness, and dispersal mode of plant species in the seed bank and analyzed these variables in terms of adjacent habitat type and age of restored habitat. I found that agricultural weed species had higher densities at the edge of restored riparian habitat and that native plants had higher densities adjacent to remnant riparian habitat. Weed seed abundance increased significantly on walnut farms adjacent to restored habitat with time since restored. I supply strong empirical evidence that large areas of natural and restored habitats do not lead to a greater penetration of weed species into agricultural areas, but rather that weed penetration is both temporally and spatially limited.     

伊洛河河岸带生态系统草本植物功能群划分

植物功能群是对环境有相同响应和对主要生态系统过程有相似作用的组合。伊洛河是黄河中游南岸的一条重要水系,其河岸带生态系统不同生境类型中草本植物优势种变化明显,能较好地反映出植被与环境的动态关系。根据调查结果,结合出现次数和重要值,选取27种优势种进行种间联结及相关性分析。以$2检验为基础,结合联结系数AC和共同出现百分率PC来测定草本层优势种间的联结性,根据优势种间的联结性及其在不同生境中的变化异同,以优势种为主体划分伊洛河河岸带生态系统中草本植物功能群。结果表明,对27种草本植物优势种共划分了5组功能群:"广布型"、"湿生型"、"中旱生型"、"农田逃逸型"和"入侵型"。表明以优势种为主体对伊洛河河岸带生态系统草本植物进行功能群划分可行性高,有较强的代表性。同一功能群物种间表现出显著正联结性,一起出现在同一生境下的几率较大,在长期的生长演化过程中,能够适应相似的资源环境且对干扰有相似的响应。伊洛河河岸带生态系统由于长期的自然和人为干扰,加上外来物种的入侵,河岸带生态系统的生物多样性和生态安全面临着严峻的挑战。     

Aquatic insects (Insecta: Plecoptera, Ephemeroptera, Odonata, and Trichoptera) of the rivers in the Berezinskii Biosphere Reserve

The fauna of aquatic insects was studied in the rivers of the Berezinskii Biosphere Reserve. A total of 108 species of 4 orders were found: Plecoptera (10 species), Ephemeroptera (24), Odonata (25), and Trichoptera (49). The aquatic fauna is abundant and includes some species rare in Belarus and Europe.     

Land use modifies Odonata diversity in streams of the Brazilian Cerrado

The presence of riparian vegetation provides microclimatic regulation of stream conditions [e.g. luminosity (lux), air temperature (°C) and relative humidity (%)], which varies naturally throughout the day. These variables explain the diurnal behaviour patterns of ectotherms such as Odonata in natural areas. However, human land uses (e.g. pastures) modify the abiotic conditions of riparian environments, favouring the presence of disturbance-tolerant species. In this context, we assess relationships between riparian land use (control streams-natural areas and pasture), abiotic conditions habitat integrity index (in control and pastures streams), (air temperature, luminosity and humidity in control streams), and Odonata diversity (between pasture and control streams and throughout the time of day) in Brazilian savannah (Cerrado) streams. First, the control streams had higher habitat integrity index than pasture. Higher abundance and difference in composition of Odonata species were observed in streams surrounded by pasture relative to natural areas. The conversion of natural areas to pasture near streams was also accompanied by an increase in overall body size of Odonata species. Odonata species richness and abundance in natural areas varied throughout the day, but peaked around 12:00 h, coinciding with changes in air temperature and luminosity. Our study highlights that changes in the physical characteristics of streams through conversion of natural habitats to pasture will change environmental conditions and act as a filter on the distribution and persistence of Odonata species in Cerrado streams.     

Evaluating the use of Myotis daubentonii as an ecological indicator in Mediterranean riparian habitats

In recent years, interest and concern regarding biodiversity conservation have grown remarkably not only among conservationists but also amongst a wider public beyond scientific institutions. The monitoring of fauna and flora over long periods of time has been satisfactorily proven to be a viable tool for quantifying how environmental changes affect natural communities. Some bat species are regarded as good bioindicators, mainly due to their longevity and high sensitivity to environmental changes. Myotis daubentonii is one of the species most closely associated with riparian habitats in the north-east Iberian Peninsula, and is used as an ecological indicator in specific monitoring programs such as the Waterway Survey (United Kingdom) and the QuiroRius (Spain). Nonetheless, there is still great controversy as to whether M. daubentonii is a good biological indicator or not. While some authors accept it as a bioindicator, others point to the studies carried out in the U.K., Poland, Switzerland and Germany that show a remarkable increase in the numbers of this bat when pollution increases in canalized rivers, which suggest that it is in fact a generalist species.Due to the lack of information regarding habitat-quality requirements in Daubenton’s bats in the Mediterranean region and the species’ potential as a bioindicator in riparian habitats, we aimed to 1) examine how QuiroRius data match other well-established biological indicators (IBMWP for invertebrates and QBR for riparian forests); 2) analyse how environmental variables at both local and landscape scales affect the presence of M. daubentonii; and 3) describe how environmental traits influence the relative abundance of M. daubentonii.A total of 104 streams below 1000 m a.s.l. were simultaneously sampled using bat, macroinvertebrate and vegetation bioindicators. Despite having similar conservation aims, these three bioindicators did not provide consistent images of overall ecosystem quality and thus a multidisciplinary approach is necessary for a full analysis of the health of these riparian ecosystems. M. daubentonii were found more frequently in wide rivers with well-structured native riparian forests; on the other hand, landscape composition at broader scales and altitude had no influence on bat presence/abundance.Thus, we suggest that QuiroRius could be used as a complementary bioindicator for analysing riparian forest quality but cannot be used alone as a tool for evaluating correctly overall riparian ecosystem health. Both relative abundance and/or presence/absence could be used as bioindicator surrogates given that the effect of microhabitat environmental predictors had similar impact on both these measures.     

Impacts of an invasive willow (Salix × rubens) on riparian bird assemblages in south‐eastern Australia

We explored how a woody plant invader affected riparian bird assemblages. We surveyed 15 200‐m‐long transects in riparian zones in a much‐changed landscape of eastern Victoria, Australia. Abundance, species‐richness, foraging‐guild richness and composition of birds were compared in transects in three habitat types: (i) riparian zones dominated by the invasive willow Salix × rubens; (ii) riparian zones lined with native woody species; and (iii) riparian zones cleared of almost all woody vegetation. We also measured abundance and richness of arthropods and habitat structure to explore further the effects of food resources and habitat on the avifauna. We observed 67 bird species from 14 foraging guilds. Native riparian transects had more birds, bird species and foraging guilds than willow‐invaded or cleared transects. Habitat complexity increased from cleared to willow‐invaded to native riparian transects, as did abundance of native and woodland‐dependent birds. Native shrub and trees species had more foliage and branch‐associated arthropods than did willows, consistent with a greater abundance and variety of foraging guilds of birds dependent on this resource. Willow spread into cleared areas is unlikely to facilitate greatly native bird abundance and diversity even though habitat complexity is increased. Willow invasion into the native riparian zone, by decreasing food resources and altering habitat, is likely to reduce native bird biodiversity and further disrupt connectivity of the riparian zone.     

Distribution of endemic and alien plants along Mediterranean rivers: A useful tool to identify areas in need of protection?

The main aim was to obtain information about the more critical sectors of Mediterranean-type rivers, especially in the islands where the percentage of endemic species is high, even in riparian habitats. Our hypothesis was that endemic and alien species, considered important in defining conservation priorities along rivers, have different patterns of distribution and their coexistence indicates human impacts on fluvial systems, which can cause natural habitat loss. Generalized Additive Models were used to model the distribution patterns of endemic and alien species along the longitudinal gradient. They showed that endemic species were linked to the most natural areas in the middle and upper sections of the rivers, whereas the distribution of aliens in middle and lower sections can be regarded as a consequence of human impact. This finding underlined the presence in the middle sections of the rivers of areas with important floristic features that are also affected by alien species. What currently seems a situation of equilibrium turns out to call for careful control, first and foremost, by maintaining riparian vegetation. Our results highlighted the utility of our method for rapidly obtaining information about the criticalities of rivers in Mediterranean biodiversity hotspots.     

Thresholds of riparian forest use by terrestrial mammals in a fragmented Amazonian deforestation frontier

Species persistence in fragmented landscapes is intimately related to the quality, structure, and context of remaining habitat remnants. Riparian vegetation is legally protected within private landholdings in Brazil, so we quantitatively assessed occupancy patterns of terrestrial mammals in these remnants, examining under which circumstances different species effectively use them. We selected 38 riparian forest patches and five comparable riparian sites within continuous forest, at which we installed four to five camera-traps per site (199 camera-trap stations). Terrestrial mammal assemblages were sampled for 60 days per station during the dry seasons of 2013 and 2014. We modelled species occupancy and detection probabilities within riparian forest remnants, and examined the effects of patch size, habitat quality, and landscape structure on occupancy probabilities. We then scaled-up modelled occupancies to all 1915 riparian patches throughout the study region to identify which remnants retain the greatest potential to work as habitat for terrestrial vertebrates. Of the ten species for which occupancy was modelled, six responded to forest quality (remnant degradation, cattle intrusion, palm aggregations, and understorey density) or structure (remnant width, isolation, length, and area of the patch from which it originates). Patch suitability was lower considering habitat quality than landscape structure, and virtually all riparian remnants were unsuitable to maintain a high occupancy probability for all species that responded to forest patch quality or structure. Beyond safeguarding legal compliance concerning riparian remnant amount, ensuring terrestrial vertebrate persistence in fragmented landscapes will require curbing the drivers of forest degradation within private landholdings.     

Seasonal use by birds of stream-side riparian habitat in coniferous forest of northcentral British Columbia

To determine use of riparian habitats by birds in the northern coniferous forest of British Columbia, we censused birds and vegetation along 500 m transects placed parallel and perpendicular to three second-order streams. Censuses were conducted during spring, summer, autumn, and winter to investigate how use of riparian habitat changed seasonally. Stream-side riparian zones were characterized by a dense understorey of deciduous vegetation not found in the upslope forest. Nine bird species preferred the riparian understorey for breeding, six preferred it only during migration. Neotropical migrants (16 of 46 species) were more closely associated with stream-sides than year-round residents (11 species). Some breeding birds (five species) were significantly negatively associated with riparian habitats. The density of riparian birds declined with distance upstream but did not decline up to 250 m away from the stream. The more extensive riparian areas downstream supported a greater density of birds in all seasons compared to upstream areas, but more species only in spring and autumn. Species that nested in non-riparian areas in summer used riparian habitat in autumn, making riparian corridors in the northern coniferous forest important during migration. Maintaining both riparian and upslope habitats is necessary to preserve species diversity al the landscape level.