Skipper Richness (Hesperiidae) Along Elevational Gradients in Brazilian Atlantic Forest

Hesperiidae are claimed to be a group of elusive butterflies that need major effort for sampling, thus being frequently omitted from tropical butterfly surveys. As no studies have associated species richness patterns of butterflies with environmental gradients of high altitudes in Brazil, we surveyed Hesperiidae ensembles in Serra do Mar along elevational transects (900–1,800 m above sea level) on three mountains. Transects were sampled 11–12 times on each mountain to evaluate how local species richness is influenced by mountain region, vegetation type, and elevational zones. Patterns were also analyzed for the subfamilies, and after disregarding species that exhibit hilltopping behavior. Species richness was evaluated by the observed richness, Jacknife2 estimator and Chao 1 estimator standardized by sample coverage. Overall, 155 species were collected, but extrapolation algorithms suggest a regional richness of about 220 species. Species richness was far higher in forest than in early successional vegetation or grassland. Richness decreased with elevation, and was higher on Anhangava mountain compared with the two others. Patterns were similar between observed and extrapolated Jacknife2 richness, but vegetation type and mountain richness became altered using sample coverage standardization. Hilltopping species were more easily detected than species that do not show this behavior; however, their inclusion did neither affect estimated richness nor modify the shape of the species accumulation curve. This is the first contribution to systematically study highland butterflies in southern Brazil where all records above 1,200 m are altitudinal extensions of the known geographical ranges of skipper species in the region.     

Phytoplankton Growth and Microzooplankton Grazing in the Subtropical Northeast Atlantic

Dilution experiments were performed to estimate phytoplankton growth and microzooplankton grazing rates during two Lagrangian surveys in inner and eastern locations of the Eastern North Atlantic Subtropical Gyre province (NAST-E). Our design included two phytoplankton size fractions (0.2–5 µm and >5 µm) and five depths, allowing us to characterize differences in growth and grazing rates between size fractions and depths, as well as to estimate vertically integrated measurements. Phytoplankton growth rates were high (0.11–1.60 d⁻¹), especially in the case of the large fraction. Grazing rates were also high (0.15–1.29 d⁻¹), suggesting high turnover rates within the phytoplankton community. The integrated balances between phytoplankton growth and grazing losses were close to zero, although deviations were detected at several depths. Also, O₂ supersaturation was observed up to 110 m depth during both Lagrangian surveys. These results add up to increased evidence indicating an autotrophic metabolic balance in oceanic subtropical gyres.     

Diversity and Frequency of Clonal Traits Along Natural and Land-Use Gradients in Grasslands of the Swiss Alps

The frequency of clonal plants in different vegetation types is known to be influenced by environmental and land-use factors. However, the underlying behavior of individual clonal traits or clonal trait diversity has received little attention. Here, we assess for species- and trait-diverse grasslands of the Swiss Alps the relative importance of temperature, soil moisture, land use and species richness on the diversity and frequency of individual compared with all clonal traits. We further analyzed how cover-weighted data alters the relationships found with commonly used presence-absence data. We combined species compositional, land-use and environmental data from 236 28-m² grassland plots with clonal trait information for 527 species following the Clonal Growth Organ (CGO) classification. Test results are based on linear models, ANOVAs and ANCOVAs. The grassland sites were 84% dominated by clonal species. Drought-prone grasslands harbored the least clonal species. No increase in clonality was detected with decreasing temperature (= altitude). Mown or pastured grasslands had more clonal species than fallows. Certain sets of traits were correlated. Rhizomatous species especially reacted strongly to climatic and land-use gradients and had highest frequencies in cold, moist and disturbed sites. Clonal diversity was strongly dependent on species richness. Cover-weighted and presence-absence based estimates were largely similar. Overall, our data outlined that common clonal traits react differently to natural and land-use gradients as well as differently to the sum of clonal traits. Also, soil moisture was more decisive than temperature (= altitude) for the presence of clonal species. Lastly, the strong correlation between species-richness and clonal trait diversity needs to be accounted for when interpreting the functional role of clonal traits.     

Patterns of Root Dynamics in Mangrove Forests Along Environmental Gradients in the Florida Coastal Everglades,USA

Patterns of mangrove vegetation in two distinct basins of Florida Coastal Everglades (FCE), Shark River estuary and Taylor River Slough, represent unique opportunities to test hypotheses that root dynamics respond to gradients of resources, regulators, and hydroperiod. We propose that soil total phosphorus (P) gradients in these two coastal basins of FCE cause specific patterns in belowground biomass allocation and net primary productivity that facilitate nutrient acquisition, but also minimize stress from regulators and hydroperiod in flooded soil conditions. Shark River basin has higher P and tidal hydrology with riverine mangroves, in contrast to scrub mangroves of Taylor basin with more permanent flooding and lower P across the coastal landscape. Belowground biomass (0–90 cm) of mangrove sites in Shark River and Taylor River basins ranged from 2317 to 4673 g m⁻², with the highest contribution (62–85%) of roots in the shallow root zone (0–45 cm) compared to the deeper root zone (45–90 cm). Total root productivity did not vary significantly among sites and ranged from 407 to 643 g m⁻² y⁻¹. Root production in the shallow root zone accounted for 57–78% of total production. Root turnover rates ranged from 0.04 to 0.60 y⁻¹ and consistently decreased as the root size class distribution increased from fine to coarse roots, indicating differences in root longevity. Fine root biomass was negatively correlated with soil P density and frequency of inundation, whereas fine root turnover decreased with increasing soil N:P ratios. Lower P availability in Taylor River basin relative to Shark River basin, along with higher regulator and hydroperiod stress, confirms our hypothesis that interactions of stress from resource limitation and long duration of hydroperiod account for higher fine root biomass along with lower fine root production and turnover. Because fine root production and organic matter accumulation are the primary processes controlling soil formation and accretion in scrub mangrove forests, root dynamics in the P-limited carbonate ecosystem of south Florida have a major controlling role as to how mangroves respond to future impacts of sea-level rise.     

Lentic Meadows and Riparian Functions Impaired After Horse and Cattle Grazing

Perennially and intermittently available water in lentic, spring-fed herbaceous meadows supports wetland plants that build and maintain absorbent soil organic matter, capture sediment, prevent erosion, and thereby sustain riparian ecosystems. Enhanced forage and available water attract a diversity of wildlife and grazing animals that can degrade riparian vegetation through prolonged overuse. We tested novel monitoring methods and adapted existing methods to obtain quantified vegetation data that have been consistently linked to riparian functionality and compared these data to ungulate species use. We quantified ungulate use with time-lapse cameras at 10 Nevada spring-fed herbaceous meadows where core greater sage-grouse (Centrocercus urophasianus) habitat, public land grazing allotments, and free-roaming horse (Equus caballus) herd management areas (Bureau of Land Management) or territories (U.S. Department of Agriculture Forest Service) overlapped. Free-roaming horses used most study sites over longer periods and grazed more intensely than cattle or domestic sheep. Native ungulate grazing intensity was comparatively negligible. Free-roaming horses selected spring-fed meadow sites on average 51 (±33 [SE]) times more than the surrounding rangelands, and cattle selected them 30 ± 23 times more. Within the wettest area of a site, study sites with longer duration of use and higher intensity of use had more soil alteration and bare ground. Riparian ecosystem degradation occurred where meadows had limited rest or recovery time from grazing during the growing season. At all sites we noted loss of riparian function, especially within the hydric areas with the highest potential to grow abundant cover of stabilizing wetland plant species. Transects for monitoring soil alteration and vegetation cover in this hydric location can provide a leading indicator of riparian recovery or degradation and help in adjusting free-roaming horse population levels or livestock management strategies. © 2021 The Wildlife Society.     

Growth and Grazing Mortality Rates of Phylogenetic Groups of Bacterioplankton in Coastal Marine Environments

Dilution culture experiments were conducted in western North Pacific coastal regions to determine growth and grazing mortality rates of bacterial phylogenetic groups (α-, β-, and γ-proteobacteria and the Cytophaga-Flavobacter cluster) detected by fluorescent in situ hybridization. Growth rates varied greatly (1.2- to 4.0-fold) among different groups, and they were related to environmental variables (chlorophyll a concentrations and temperature) in a group-specific fashion. Growth rates of α-proteobacteria, the most abundant group in all the samples examined, were generally lower than those of less abundant groups, including the Cytophaga-Flavobacter cluster and γ-proteobacteria. Grazing mortality rates and mean cell volumes varied little among different groups. These results provide insights into factors that affect distributions of different groups, but growth and grazing mortality alone did not fully explain bacterial community compositions at a broad phylogenetic level.     

Future Coastal Population Growth and Exposure to Sea-Level Rise and Coastal Flooding - A Global Assessment

Coastal zones are exposed to a range of coastal hazards including sea-level rise with its related effects. At the same time, they are more densely populated than the hinterland and exhibit higher rates of population growth and urbanisation. As this trend is expected to continue into the future, we investigate how coastal populations will be affected by such impacts at global and regional scales by the years 2030 and 2060. Starting from baseline population estimates for the year 2000, we assess future population change in the low-elevation coastal zone and trends in exposure to 100-year coastal floods based on four different sea-level and socio-economic scenarios. Our method accounts for differential growth of coastal areas against the land-locked hinterland and for trends of urbanisation and expansive urban growth, as currently observed, but does not explicitly consider possible displacement or out-migration due to factors such as sea-level rise. We combine spatially explicit estimates of the baseline population with demographic data in order to derive scenario-driven projections of coastal population development. Our scenarios show that the number of people living in the low-elevation coastal zone, as well as the number of people exposed to flooding from 1-in-100 year storm surge events, is highest in Asia. China, India, Bangladesh, Indonesia and Viet Nam are estimated to have the highest total coastal population exposure in the baseline year and this ranking is expected to remain largely unchanged in the future. However, Africa is expected to experience the highest rates of population growth and urbanisation in the coastal zone, particularly in Egypt and sub-Saharan countries in Western and Eastern Africa. The results highlight countries and regions with a high degree of exposure to coastal flooding and help identifying regions where policies and adaptive planning for building resilient coastal communities are not only desirable but essential. Furthermore, we identify needs for further research and scope for improvement in this kind of scenario-based exposure analysis.     

Flooding and Plant Growth

This Special Issue is based on the 7th Conference of the InternationalSociety for Plant Anaerobiosis (ISPA), held in Nijmegen, TheNetherlands, 12–16 June 2001. The papers describe andanalyse many of the responses that plants display when subjectedto waterlogging of the soil or deeper submergence. These responsesmay be injurious or adaptive, and are discussed at various levelsof organizational complexity ranging from ecosystem processes,through individual plants to single cells. The research incorporatesmolecular biology and genetics, cell physiology, biochemistry,hormone physiology, whole plant physiology, plant demographyand ecology. The study of the damage to young rice plants causedby submergence, especially as experienced in the rainfed lowlandsof Asia, is comprehensively addressed. This work integratesvarious specialized approaches ranging from agronomy to moleculargenetics, and demonstrates how plant biology can be harnessedto improve stress tolerance in an important crop species whilesimultaneously improving basic understanding of tolerance mechanismsand plant processes.     

Decadal Changes in the World's Coastal Latitudinal Temperature Gradients

Most of the world''s living marine resources inhabit coastal environments, where average thermal conditions change predictably with latitude. These coastal latitudinal temperature gradients (CLTG) coincide with important ecological clines,e.g., in marine species diversity or adaptive genetic variations, but how tightly thermal and ecological gradients are linked remains unclear. A first step is to consistently characterize the world''s CLTGs. We extracted coastal cells from a global 1°×1° dataset of weekly sea surface temperatures (SST, 1982–2012) to quantify spatial and temporal variability of the world''s 11 major CLTGs. Gradient strength, i.e., the slope of the linear mean-SST/latitude relationship, varied 3-fold between the steepest (North-American Atlantic and Asian Pacific gradients: −0.91°C and −0.68°C lat⁻¹, respectively) and weakest CLTGs (African Indian Ocean and the South- and North-American Pacific gradients: −0.28, −0.29, −0.32°C lat⁻¹, respectively). Analyzing CLTG strength by year revealed that seven gradients have weakened by 3–10% over the past three decades due to increased warming at high compared to low latitudes. Almost the entire South-American Pacific gradient (6–47°S), however, has considerably cooled over the study period (−0.3 to −1.7°C, 31 years), and the substantial weakening of the North-American Atlantic gradient (−10%) was due to warming at high latitudes (42–60°N, +0.8 to +1.6°C,31 years) and significant mid-latitude cooling (Florida to Cape Hatteras 26–35°N, −0.5 to −2.2°C, 31 years). Average SST trends rarely resulted from uniform shifts throughout the year; instead individual seasonal warming or cooling patterns elicited the observed changes in annual means. This is consistent with our finding of increased seasonality (i.e., summer-winter SST amplitude) in three quarters of all coastal cells (331 of 433). Our study highlights the regionally variable footprint of global climate change, while emphasizing ecological implications of changing CLTGs, which are likely driving observed spatial and temporal clines in coastal marine life.     

Benthic Diatom Communities Along pH and TP Gradients in Hungarian and Swedish Streams

Benthic diatoms are widely used in Europe to assess ecological status of running waters. The aim of this study was to develop models to predict average pH and total phosphorus (TP) for European stream monitoring using combined diatom data-sets from Hungary and Sweden. As first step, the relationship between the measured environmental variables and the distribution of the taxa was checked by classification by using cluster-analysis and CCA. Diatom data separated clearly along the main hydrogeochemical parameters (e.g. alkalinity, pH). Concerning nutrients, TP was the most determinant factor. Predictive value of the TP model (r = 0.96) is high only for the Hungarian data and the pH model (r = 0.97) can be used in both phycogeographical regions.     

Patterns of Clonal Growth Modes Along a Chronosequence of Post-Coppice Forest Regeneration in Beech Forests of Central Italy

Forest coppicing leads to changes in composition of the herbaceous understory through soil disturbance and alteration of the light regime. While the role of seed dispersal traits at the start of succession after coppicing has been extensively studied, the role of persistence traits such as clonal growth and bud banks is not yet sufficiently understood. To gain better understanding of this role, we studied the patterns of clonal growth organs and related clonal traits of species in a series of coppiced beech forests of the Central Apennines (Marches region, Italy) in various stages of recovery after the last coppicing event. We conducted stratified random sampling and established a chronosequence of recovery stages based on stand age (reflecting the number of years since the last coppicing). The beech stands were classified into three age groups (Post-logged, Recovering, and Old-coppice stands) according to the characteristic stages of beech coppice dynamics. Clonal growth organs and the corresponding clonal traits of plants in the forest understory vegetation were assessed with the help of a CLO-PLA1 database. We found no significant change in the proportion of clonal species along the studied chronosequence. In contrast, most of the traits and about the half of the clonal growth organs showed correlation with stand age or preference for a certain habitat (i.e., stage of regeneration). Clonal and bud bank traits proved to play an important role in the persistence of species subjected to forest coppicing cycles in the studied area.     

Species Richness of Nonvolant Small Mammals Along Elevational Gradients in Northwestern Argentina

The Nevados del Aconquija (5500 m) and Cumbres Calchaquíes (4600 m) are isolated mountain ranges that contain at least three physiognomic units in their eastern slopes: Neotropical rainforests, Andean grasslands and High Andean Steppes. Despite phytogeographical similarities, the two ranges differ in the amount and spatial distribution of rainfall over the elevation gradient. We studied terrestrial small mammals by direct trapping in two altitudinal transects on the eastern slope of the two mountain ranges. We recorded the changes in richness and species composition, as well as the relationships between species and microhabitats at each altitudinal level. The results show a similar structure of the small mammal assemblage in the two ranges. The largest differences, in terms of species composition, were registered at lower elevation forests, and faunal affinities increased with elevation to the point of finding identical species composition at the top of the mountains. Species richness showed a clear curvilinear pattern with a peak at the upper limit of the forests. Our findings suggest that total rainfall has an important influence on the composition and abundance of small mammal species but apparently not on the species richness along the elevation gradient. The highest values of species richness were observed at the sites where a contact between two different physiognomic units exists. These results indicate that habitat heterogeneity plays an important role in allowing the juxtaposition of small terrestrial mammal assemblages of the highlands and lowlands at a given point, contributing significantly to the considerable diversity of species observed in intermediate altitudinal sites.
     

Effects of Burning and Grazing on a Coastal California Grassland

We tested the effects of fall burning and protection from livestock grazing as management to enhance native grasses on a coastal grassland in central California. Plants from the Mediterranean, introduced beginning in the late 1700s, have invaded and now dominate most of California's grasslands. Coastal grasslands are generally less degraded than those inland and have higher potential for restoration and conservation. Productivity of the experimental plots varied annually and declined over the course of the study because of rainfall patterns. Foliar cover of the native Danthonia californica (California oatgrass) increased more under grazing than grazing exclusion and did not respond to burning. Two other natives, Nassella pulchra (purple needlegrass) and Nassella lepida (foothill needlegrass), responded variably to treatments. The response of N. pulchra differed from that reported on more inland sites in California. Restoring these grasslands is complicated by differing responses of target species to protection from grazing and burning. The current practice of managing to enhance single species of native plants (e.g., N. pulchra) may be detrimental to other equally important native species.     

Behaviors and Strategies of Bacterial Navigation in Chemical and Nonchemical Gradients

Navigation of cells to the optimal environmental condition is critical for their survival and growth. Escherichia coli cells, for example, can detect various chemicals and move up or down those chemical gradients (i.e., chemotaxis). Using the same signaling machinery, they can also sense other external factors such as pH and temperature and navigate from both sides toward some intermediate levels of those stimuli. This mode of precision sensing is more sophisticated than the (unidirectional) chemotaxis strategy and requires distinctive molecular mechanisms to encode and track the preferred external conditions. To systematically study these different bacterial taxis behaviors, we develop a continuum model that incorporates microscopic signaling events in single cells into macroscopic population dynamics. A simple theoretical result is obtained for the steady state cell distribution in general. In particular, we find the cell distribution is controlled by the intracellular sensory dynamics as well as the dependence of the cells'' speed on external factors. The model is verified by available experimental data in various taxis behaviors (including bacterial chemotaxis, pH taxis, and thermotaxis), and it also leads to predictions that can be tested by future experiments. Our analysis help reveal the key conditions/mechanisms for bacterial precision-sensing behaviors and directly connects the cellular taxis performances with the underlying molecular parameters. It provides a unified framework to study bacterial navigation in complex environments with chemical and non-chemical stimuli.     

Imprints of Natural Selection Along Environmental Gradients in Phenology-Related Genes of Quercus petraea

We explored single nucleotide polymorphism (SNP) variation in candidate genes for bud burst from Quercus petraea populations sampled along gradients of latitude and altitude in Western Europe. SNP diversity was monitored for 106 candidate genes, in 758 individuals from 32 natural populations. We investigated whether SNP variation reflected the clinal pattern of bud burst observed in common garden experiments. We used different methods to detect imprints of natural selection (F_ST outlier, clinal variation at allelic frequencies, association tests) and compared the results obtained for the two gradients. F_ST outlier SNPs were found in 15 genes, 5 of which were common to both gradients. The type of selection differed between the two gradients (directional or balancing) for 3 of these 5. Clinal variations were observed for six SNPs, and one cline was conserved across both gradients. Association tests between the phenotypic or breeding values of trees and SNP genotypes identified 14 significant associations, involving 12 genes. The results of outlier detection on the basis of population differentiation or clinal variation were not very consistent with the results of association tests. The discrepancies between these approaches may reflect the different hierarchical levels of selection considered (inter- and intrapopulation selection). Finally, we obtained evidence for convergent selection (similar for gradients) and clinal variation for a few genes, suggesting that comparisons between parallel gradients could be used to screen for major candidate genes responding to natural selection in trees.     

Coastal Fish Assemblages Reflect Geological and Oceanographic Gradients Within An Australian Zootone

Distributions of mobile animals have been shown to be heavily influenced by habitat and climate. We address the historical and contemporary context of fish habitats within a major zootone: the Recherche Archipelago, southern western Australia. Baited remote underwater video systems were set in nine habitat types within three regions to determine the species diversity and relative abundance of bony fishes, sharks and rays. Constrained ordinations and multivariate prediction and regression trees were used to examine the effects of gradients in longitude, depth, distance from islands and coast, and epibenthic habitat on fish assemblage composition. A total of 90 species from 43 families were recorded from a wide range of functional groups. Ordination accounted for 19% of the variation in the assemblage composition when constrained by spatial and epibenthic covariates, and identified redundancy in the use of distance from the nearest emergent island as a predictor. A spatial hierarchy of fourteen fish assemblages was identified using multivariate prediction and regression trees, with the primary split between assemblages on macroalgal reefs, and those on bare or sandy habitats supporting seagrass beds. The characterisation of indicator species for assemblages within the hierarchy revealed important faunal break in fish assemblages at 122.30 East at Cape Le Grand and subtle niche partitioning amongst species within the labrids and monacanthids. For example, some species of monacanthids were habitat specialists and predominantly found on seagrass (Acanthaluteres vittiger, Scobinichthys granulatus), reef (Meuschenia galii, Meuschenia hippocrepis) or sand habitats (Nelusetta ayraudi). Predatory fish that consume molluscs, crustaceans and cephalopods were dominant with evidence of habitat generalisation in reef species to cope with local disturbances by wave action. Niche separation within major genera, and a sub-regional faunal break, indicate future zootone mapping should recognise both cross-shelf and longshore environmental gradients.