Nonresponse of native cottonwood trees to water additions during summer drought

Studies have demonstrated that some riparian trees may switch their reliance on surface soil water (unsaturated or vadose zone) to groundwater (saturated zone) sources during the growing season in association with changes in moisture availability. A closely related question is: How do these trees respond to pulse increases in water availability in previously dry zones? We tested the whole-tree physiological response of 6 natural Populus genotypes to water additions during the peak of summer drought in northern Utah, USA. We found clear evidence that trees were insensitive to water additions to the surface soil that were twice the magnitude of whole-tree transpiration rates. Our results suggest that some cottonwoods may have little immediate transpiration or leaf conductance response to pulse soil moisture increases. This lack of response may be related to a water-use strategy associated with regional climate patterns (i.e., genetic or environmental programming), cavitation recovery, or other physical determinants of water use such as depth to groundwater. Our data suggest that it is important to consider potential nonresponsiveness to changes in soil water availability when evaluating the impact of climate change on these important and productive ecosystems.     

Horizontal and vertical distribution of Dolichopodidae (Diptera) in a woodland ecosystem

The horizontal and vertical distribution of dolichopodid flies in a deciduous woodland ecosystem was investigated by means of white-water traps during a nearly 8-month period. Eighteen traps were installed along a light intensity/soil humidity gradient (three zones) and from 0 to 80cm high (six levels). Six environmental features were recorded on several occasions. The dolichopodid data were analysed by means of two multivariate techniques, detrended correspondence analysis (DCA) and two-way indicator species analysis (TWINSPAN). The DCA revealed four distinct species groups, which also proved to be clearly different on a broader ecological basis. The horizontal distributions in many species could be explained by the different environmental conditions in the zones. Although nearly all species were unequally distributed over the traps, their stratification patterns generally showed no significant correlation with the recorded biotic and abiotic features. It is therefore suggested that the observed vertical distributions are the results of a combination of specific and environmental characteristics.     

Physiological, Morphological, and Environmental Variation Among Geographically Isolated Cottonwood (Populus Deltoides) Populations in New Mexico

The ability of a plant population to respond and eventually adapt to environmental stress ultimately determines that population's survival. This becomes especially significant in environments where important plant resource levels have radically decreased. Southwestern riparian areas have numerous plant species that are experiencing radical changes in water availability due to construction of dams, and thus their ability to respond to such changes is critical. One such species likely to be greatly affected by these hydrological changes is Populus deltoides var. wislizenii (cottonwood) because it relies heavily on both groundwater and river surface volume as primary water sources. Both water sources have been extremely impacted by impoundments along southwestern rivers. To understand how New Mexico populations of cottonwood may respond to environmental changes, we quantified environmental differences and characterized physiological and morphological variation among 4 cottonwood populations. Significant differences among study sites in water availability were indicated by both soil and groundwater salinity. The northernmost site, at Abiquiu, had the highest salinity levels in both soil and groundwater, followed by Bernardo, while San Antonio and Corrales sites had the lowest soil salinity. As expected, variation in physiological and leaf morphological characters existed among and within the tree populations, most likely in response to environmental factors. Midday xylem pressure potentials indicated that Abiquiu individuals suffered the greatest water stress and they also had the highest transpiration levels. Because of high specific leaf weights and high photosynthetic levels, cottonwoods at Corrales may better mitigate lower water availability. Such physiological and morphological trait variability among populations is ecologically important and may be of use in present reclamation and conservation efforts in these areas.     

Variability among five riparian cottonwood ( Populus fremontii Wats.) populations: an examination of size, density, and spatial distribution

Various abiotic and biotic factors are known to affect tree size, including age, genetics, and environment. Knowledge of size variation within natural riparian tree populations has both ecological and restorative importance. We determined tree sizes, basal area densities, and spatial distributions of 5 Populus fremontii Wats. populations within the Rio Grande watershed in New Mexico. At each site 10 randomly spaced plots, perpendicular to the river and extending from the river to the end of the forest, were established. Diameter at breast height (DBH) and distance to the river were determined for 1803 trees within the 5 populations, and stand cover (measured as basal area [BA] per hectare) was determined for each population. Significant variation in tree size and basal area density existed among sites. Mean DBH per site ranged from 11.7 to 58.4 cm and differed significantly ( P P 2 ha -1 . Spatial distribution of trees in relation to the river also differed among sites. Mean distance from the river ranged from 50 to 353 m and differed significantly ( P P. fremontii populations may be influenced by differences in water availability across a site; trees farthest from water sources may experience greater water stress and, therefore, growth limitation. Increasing BA cover with increasing tree size indicated no real thinning of mature trees within a population. Recruitment and establishment of cottonwood seedlings and saplings was evident only at sites with newly formed floodplains. For these 5 populations tree size appeared to be affected by environmental factors.     

A comparison of riparian condition and aquatic invertebrate community indices in central Nevada

The importance of maintaining healthy riparian communities to sustain natural stream processes and function is well documented. Land management agencies in the West are currently developing methods to assess and monitor riparian community condition to adapt land use practices that would better protect rangeland ecosystems. To determine whether these methods also provide an indication of abiotic and biotic stream condition, we compared the classification system of riparian communities developed by the U.S. Forest Service (USFS) to physical parameters of stream condition and to aquatic invertebrate community assemblages. Thirty-three sites in 19 different streams of the Toiyabe Range in central Nevada were measured for water quality, substrate characteristics, and fish abundance and diversity. We sampled aquatic invertebrates and calculated community indices based on environmental tolerance levels, taxonomic diversity, and abundance of sensitive taxa. USFS personnel classified these sites by dominant riparian plant community type (meadow, willow, or aspen) and ecological status (low, moderate, or high) using plant abundance data, rooting depth, and soil infiltration to determine similarities to potential natural communities. Riparian condition indices as well as community diversity were significantly correlated to proportions of fine and small-diameter substrate in streambeds. Accumulation of silt was significantly related to plant community type, with meadow sites expressing highest proportions. Further examinations indicated that 2 of 6 invertebrate community indices were significantly related to ecological status, with highest diversity levels occurring mainly in willow- and aspen-dominated sites in moderate ecological condition. Nevertheless, we show that several other environmental variables, including substrate characteristics, dissolved oxygen, water temperature, and species richness of fish communities, were more strongly and consistently related to invertebrate assemblage patterns. Our results demonstrate that information on aquatic invertebrates and stream condition could augment the existing riparian classification system and provide useful monitoring tools to more thoroughly examine ecosystem health in rangelands.     

Distribution of the meadow lizard in Europe and its realized ecological niche model

One of the most interesting but elusive members of the European herpetofauna is the meadow lizard (Darevskia praticola). It is a small, ground dwelling, predominantly forest living lacertid, for which many ecological and biological data are still missing. Moreover, at least for the western part of the species range (south-eastern Europe) its distribution and environmental associations are insufficiently known, likely due to difficulties in detection even with intensive field sampling. Here, we complemented the available literature records with our personal observations and explored the effects of environmental factors shaping the species ecological niche and distribution in Europe using the ecological niche modelling approach from Maxent software. The new records of the meadow lizard fill a gap in its known distribution. The most suitable habitats are in central and eastern Serbia, south-western Romania, and central, southern and south-western Bulgaria. Mean temperature of the coldest quarter, vegetation and slope had the strongest effect in defining the meadow lizard’s ecological niche. Niche suitability increased with the increase in forest cover and slope, while the temperature showed a bell-shaped response with a rather narrow tolerance range for temperature. Contrary to expectations, precipitation seemed to have no contribution to the species occurrence. Ecological niche model performance increased with a higher resolution of predictor variables despite the lower number of available occurrence records, although the slope variable had a greater predictive power when calculated at a lower resolution. Interestingly, high resolution vegetation variables (30 m) were able to show some level of habitat fragmentation, which likely resulted from deforestation. Overall, our results epitomize the effects of limited sampling on the biogeography inference of elusive species while having significant repercussions on conservation priorities and management of the species.     

Evidence for a geographical gradient selection in the distribution of breeding Podicipedidae and Rallidae in the south-western Mediterranean

ABSTRACT

Knowledge of factors influencing waterbird distribution is a crucial step that would help wetland managers to target their conservation efforts. In this work, we used a 2-year survey in 25 wetlands distributed throughout Morocco to model Podicipedidae and Rallidae spatial distribution and to assess the relevance of a set of environmental and anthropogenic factors in predicting site occupancy, by means of generalised linear mixed models (GLMM). In Podicipedidae, little grebes and great crested grebes were the most commonly detected species, while in Rallidae the most common species was the common moorhen. Geographical location (measured mainly as distance to the coastline and elevation) was the major predictor of the occurrence probability of breeding Podicipedidae and Rallidae species in Morocco. Statistical analyses also provide evidence that there exists a geographical selection gradient in wetland occupancy. Indeed, Podicipedidae species (great crested grebes and black-necked grebes) tend to use continental mountain wetlands, while Rallidae (purple swamphens and Eurasian coots) tend instead to use coastal wetlands. However, none of the considered environmental and anthropogenic factors explained the distribution patterns of the red-knobbed coot. The pursuit of the investigations, while considering other explanatory factors such as water quality (limnological data), diet, predation and conservation status, is of great importance for understanding basic, large-scale geographical distribution patterns of Moroccan waterbird populations.     

A classification of aquatic plant communities within the Nothern Rocky Mountains

A synecological study of aquatic macrophyte plant communities was conducted across northern Idaho and western Montana during the summers of 1997, 1998, and 1999. A total of 111 natural and man-made water bodies were sampled based on a stratification of environmental variables thought to influence plant species distribution (i.e., elevation, landform, geology, and water body size). Plant species foliar cover data were used to develop a hierarchical, floristic-based community type classification with TWINSPAN and DECORANA software. Six planmergent (conspicuous portion of vegetative plant body on the water surface) and 24 submergent (vegetative plant body found primarily underwater) community types were identified. Multivariate analysis indicated that all community types displayed significant differences in plant species composition, and the Sorensons floristic similarity between communities averaged 10% for planmergent and 8% for submergent types. Canonical correspondence analysis was used to inspect relationships between abiotic factors and plant species abundance. Results of this analysis indicated some relationships between species distributions and abiotic factors; however, chance introduction of plant species to water bodies is a process considered to be equally important to the presence of the community types described.     

Potential geographic distribution niche modeling based on bioclimatic variables of three species of Temnomastax Rehn and Rehn, 1942 (Orthoptera: Eumastacidae)

Predictive modeling of geographic distribution based on ecological niche has become an important tool in ecology. It uses previous information about distribution of species and environmental variations associated with this distribution, restricting to the models the closest prediction of the ecological niche. The eumastacid grasshoppers are distributed mainly in the Neotropical region, and Temnomastacinae is the subfamily with the largest geographic distribution. Little is known about the biology of Eumastacidae, the only data available reporting the association between some grasshopper species and plants of several families. In the Cerrado only Temnomastax is recorded, which has a wide distribution in the central region of Brazil. The aim of this work was to determine the potential geographic distribution of three species of Temnomastax occurring in the Cerrado biome. We used 446 records of occurrence obtained in specialised literature, inventories, museums and photographs, from the following species: Temnomastax hamus, Temnomastax ricardoi and Temnomastax tigris. The niche modeling was generated with the bioclimatic model DOMAIN through DIVA-GIS. The potential geographic distribution of T. hamus is the largest among all Temnomastax species. Temnomastax ricardoi has its potential distribution in the central-north of Mato Grosso do Sul, in regions surrounding the type locality, while T. tigris. exhibits a restricted potential distribution along the carbonate arc of the Corumbá Formation, which outcrops in the region of Serra da Bodoquena and Corumbá, entering the eastern portion of Bolivia.     

Disentangling prey-handling efficiency of larval newts through multivariate prey trait analysis

Multivariate prey trait analysis is a functional approach to understand predator–prey relationships. In the present study, six prey macroinvertebrate ecological traits were used to identify several key factors in the handling efficiency of seven predatory larval newt species. The results revealed a remarkable similarity in the feeding behaviour among species, suggesting a foraging behaviour convergence among species in the prey-handling efficiency of larval newts. Nevertheless, larvae of some newt species showed clear preferences for particular categories of ecological trait; for example, Lissotriton vulgaris tended to feed on macroinvertebrate taxa with random trajectory, and Calotriton asper fed on macroinvertebrate taxa with high agility. In contrast, Mesotriton alpestris showed a clear ability to feed on prey with movable accessories (cases/tubes) and patterned concealment. This study shows how multivariate approaches can complement traditional diet analyses, and the method has wide applicability across life-stages and species.     

Emersion behaviour and foraging ecology of the common Chilean clingfish Sicyases sanguineus (Pisces: Gobiesocidae)

The present study is the first to correlate information on emersion behaviour and foraging ecology of Sicyases sanguineus, a common clingfish of the Chilean coast. Individuals smaller than 15 cm in total length were frequently found at the highest points in the inter-tidal zone and consumed inter-tidal animals and seaweeds. Fish larger than 23 cm were infrequently observed emersed in the lower inter-tidal zone, but were collected sub-tidally by divers. These large clingfish ate mainly benthic animals occurring in the low inter-tidal and sub-tidal zones. Size-dependent factors, dessication and wave impact restrict the area of action of S. sanguineus to certain areas of the rocky inter-tidal and shallow sub-tidal zone. However, the fish can be locally very abundant, consuming a great diversity of prey items including both direct primary space users and mobile animals able to affect community structure through grazing. We argue, therefore, that S. sanguineus may be important in structuring communities in some areas of the rocky inter-tidal and shallow subtidal zones of Central Chile.     

Distribution and abundance of birds in the White Mountains, California

This paper quantifies the distribution and abundance of birds in the White Mountains, Inyo and Mono counties, California, during spring-summer 1989-91, to establish a baseline for monitoring the area's avifauna. Overall 58 species were encountered in the single-leaf pinyon-Utah juniper ( Pinus monophylla-Juniperus osteosperma ) zone, and 61 species in the bristlecone-limber pine ( P. longaeva-P. flexilis ) zone. The bristlecone-limber pine zone had a significantly greater overall bird abundance relative to the pinyon-juniper. Both zones were characterized by few very abundant species, a few moderately abundant species, and numerous rare species. The Black-throated Gray Warbler (scientific names in tables), Gray Flycatcher, and Pinyon Jay were the most abundant species in the pinyon-juniper whereas the Clark's Nutcracker, Mountain Chickadee, and Cassin's Finch were the most abundant species in the bristlecone-limber pine. There were few ecological or taxonomic replacements of species between zones, with the differences in distribution and abundance related primarily to the interaction between elevation and vegetation. Significant inter-year variation in abundance was found for about 20 species in each zone—more species showed declining rather than increasing trends. The Mountain Chickadee and White-breasted Nuthatch declined, whereas the Gray Flycatcher and Rock Wren increased across years in both zones. Reasons for declines in some species might be the severe drought that continued throughout this study.     

Experimental manipulations of precipitation seasonality: effects on oak ( Quercus ) seedling demography and physiology

Predicted changes in regional precipitation patterns and soil moisture caused by anthropogenic trace gas emissions may affect the distribution and abundance of woody plants in arid and semiarid regions. To test the response of woody plants to potential changes in precipitation regimes, we manipulated summer and winter precipitation on plots that contained seedlings of Quercus emoryi Torr. (Emory oak), the dominant tree in oak savannas of the southwestern United States. Throughout the growing season, we monitored seedling survival and physiology (predawn leaf water potential, midday instantaneous gas exchange, and leaf carbon isotope discrimination). Seedling survival and physiological performance differed little between treatments, which embodied 50% changes to quantities of summer and winter precipitation, and encompassed a continuum of precipitation from 359 mm · year -1 to 846 mm · year -1 . However, survival and physiological performance of seedlings were negatively impacted by seasonal environmental conditions common to all treatments, especially during the annual pre-'monsoon' drought. Seedling predawn leaf water potentials, net CO 2 assimilation, and stomatal conductance indicate that growing conditions for Q. emoryi seedlings at this site are generally restricted to periods with adequate soil moisture (i.e., April and August). Results contrast with an assumption implicit to the ""two-layer"" soil water resource partitioning hypothesis that woody plants in all life history stages are more dependent upon winter than summer precipitation. In fact, summer precipitation appears more important than winter precipitation for Q. emoryi seedling recruitment and growth.     

Population dynamics of the bark-dwelling spider Eustala perfida Mello-Leitão, 1947 (Araneidae)

Population dynamics of spiders may vary according to biotic and abiotic factors. We studied the phenology of the bark-dwelling spider Eustala perfida over a two-year period and investigated how temperature, precipitation, and prey availability were associated with the population of this species. The population of E. perfida presented a well-defined fluctuation, with one reproductive cycle per year. The recruitment of spiders occurred in summer, followed by successive phenological peaks at all stages of development. The species is protogynic, and the population of adult males peaks in the cold/dry season, indicating a winter mature phenological pattern. The diet of E. perfida is composed mainly of medium-sized homopterans, complemented by small dipterans and hymenopterans. We found that the higher abundance of spiders occurred two months after the highest values of precipitation and temperature, and three months after the higher abundance of potential prey items. These results indicate that spiders require time to respond to changes in environmental conditions. The species’ natural history and the structure of the trunks in which it lives may also affect the number of individuals in a particular area and over time.     

A revision of the genus Stenognatha Felder (Lepidoptera: Arctiidae: Pericopinae)

The acarine faunas of supralittoral tidal debris and lichens were examined on a number of shores; differences in the faunas were attributed to different environmental factors within the two habitats. The Acari may be divided into three ecologically defined groups: (a) maritime species which are confined to the seashore, especially the supralittoral, but may venture into the upper littoral zone; (b) non-maritime species which frequent the seashore, but usually occur inland in soils, leaf litter, and/or vegetation; and (c) nomadic species which migrate freely and regularly between the littoral and supralittoral zones. On the Isles of Scilly some maritime species are absent, and are replaced by non-maritime forms. Freeliving Acari are generally preadapted to the supralittoral zone, and no specializations have been noted among the fauna.     

Natural history and ecological niche modelling of coastal Atyphella Olliff Larvae (Lampyridae: Luciolinae) in Vanuatu

ABSTRACT

The genus Atyphella Olliff includes several coastal species with larvae that were collected on coastal rock within the intertidal zone. Recent fieldwork in Vanuatu has expanded the distribution of these insects and begun to provide insight into how they are able to survive in such a unique environment. An ecological niche model is produced using Maxent to predict additional locations of coastal Atyphella in the South Pacific. Larval instars for the two species of Atyphella in Vanuatu are estimated using protergum shield width measurements. Additionally, submersion tests were performed on larvae to determine survivability in saltwater and freshwater environments. These data provide evidence for previously unknown aspects of their natural history that strongly suggest the species are multivoltine and spend a large portion of their larval stage in the intertidal zone.     

Classification and ordination of Coleogyne communities in southern Nevada

Woody plant community composition was analyzed throughout the range of Coleogyne ramosissima in the Spring and Sheep Mountain ranges of southern Nevada. The lower Coleogyne elevational boundary was analyzed in detail in Lucky Strike Canyon, on the eastern edge of the Spring Mountains. TWINSPAN (2-way indicator species analysis) identified 4 primary species and stand groups from the 2 mountain ranges (extensive survey). Analysis of DECORANA (detrended correspondence analysis) results indicated that elevation and soil depth were the environmental factors most significantly associated with distribution of species and stand groups in the extensive survey. Elevation was the only significant physical factor associated with distribution of species and stand groups in the intensive survey. Five vegetation zones form the 2 mountain ranges were identified based on their dominant species in 15 extensive transects. Coleogyne were subdivided into pure stands and upper and lower ecotones for further investigation of species distribution and environmental factors. Selected environmental factors appear to play an important role in structuring the Mojave Desert vegetation zones in southern Nevada.     

Hybridization between a rare and introduced Oenothera along the north Pacific Coast

Interspecific hybridization has increasingly become regarded as a serious threat to the genetic integrity and persistence of rare plants. Oenothera glazioviana (Onagraceae) is a horticultural species that has escaped cultivation and now threatens the narrow Pacific coastal endemic O. wolfii with hybridization. Reports of morphologically intermediate and ecologically aggressive forms prompted this investigation into the extent of hybridization over the range of O. wolfii . In particular, this study identifies populations of pure and hybrid origins. We used multivariate methods to characterize the morphological variation of Oregon and northern California coastal Oenothera populations. Putatively pure O. wolfii and O. glazioviana individuals do not overlap in many floral characteristics. We found morphologies ranging between the 2 species in northern California populations, however, supporting the inference of hybridization. Remote O. wolfii populations in Oregon were smaller in almost all characters, and discriminant analysis was able to distinguish the rare species from both hybrids and O. glazioviana . However, 5 of 10 O. wolfii populations overlapped significantly with hybrid populations for individual traits and composite morphology, and trait values outside the range of O. wolfii were discovered in 2 populations previously considered to be pure. We also discuss the morphological evidence in light of these species’ chromosomal complexes and environmental factors.     

Infestation levels of Culex (Phytotelmatomyia) mosquitoes inhabiting water-filled Eryngium pandanifolium (Apiaceae) under different sunlight condition

Water accumulations in vegetal structures, known as phytotelmata, serve as aquatic habitats for many insects, including mosquitoes. Among them, Culex (Phytotelmatomyia) is composed by a few species that are highly specialized and poorly known. The objective of this study was to evaluate the association between sunlight conditions and the abundance of immature stages of Culex (Phytotelmatomyia) species in the axils of Eryngium pandanifolium. A forest patch with a dense population of E. pandanifolium in the Lower Delta of the Paraná River (Entre Ríos province, Argentina) was sampled twice a month between December and May. A total of 880 plants were inspected in 220 sample zones defined by a combination of location within the patch and sunlight condition. All individuals collected (n = 521) belonged to Culex (Phytotelmatomyia) hepperi (56%), Culex (Phytotelmatomyia) castroi (40%), and Culex (Phytotelmatomyia) renatoi (4%). According to generalized linear models, the habitat availability (i.e. water presence) was positively associated with sun exposure, but not with the location within the patch. Mosquito presence and abundance were positively related only to water volume. Coexistence of C. hepperi and C. castroi was more frequent than would be expected by chance. Further studies to understand the effects of sunlight and plant architecture on water dynamics are needed.