Bimodal transparency as an indicator for alternative states in South American lakes

1. The alternative state theory claims that shallow lakes may have either clear water, and be dominated by submerged macrophytes, or turbid water and be dominated by phytoplankton. Most evidence for this theory comes from studies in temperate or boreal regions of Europe. Because of differences in the strength of trophic interactions, such as in the pressure of zooplankton grazing on phytoplankton, this influential theory might not apply elsewhere. 2. Here, we test the theory for South American lakes, combining field data and Landsat satellite data. We studied the frequency distribution of primary producers and water transparency, looking for potential bimodality separating clear and turbid lakes. A bimodal distribution might be observed if there are indeed alternative states, although would not itself be sufficient evidence for the theory. Possible shifts between alternative states were analysed by comparing satellite data from 1987 to 2005. 3. In our field data, there was a bimodal pattern in phytoplankton abundance and possibly in the abundance of submerged macrophytes, but not in water transparency. Analyses of the larger satellite data set revealed bimodality in lake transparency in 2005, but less so in 1987. In 1987, the lakes were generally clearer, and the transition to higher turbidity was more gradual than in 2005. The stronger bimodality in the more recent data, and the overall lower transparency, could have been caused by an increase in fertiliser use and subsequent eutrophication but also by differences in hydrology. Further, 1987 was much wetter than 2005, which could have caused dilution of suspended particles, leading to clearer water. 4. While a bimodal distribution in the abundance of primary producers and water clarity is not decisive evidence for or against the theory of alternative states, our data clearly fail to refute it.     

Use of diploid male frequency data as an indicator of pollinator decline

Pollination deficits in agricultural and natural systems are suggestive of large reductions in pollinator populations. However, actual declines are difficult to demonstrate using census data. Here, we show census data to be misleading because many abundant pollinators exhibit high levels of production of sterile diploid males usually found only in small inbred hymenopteran populations; Euglossa imperialis exhibits high levels of diploid male production induced by low effective population sizes (Ne approximately 15), despite being the most abundant orchid bee in lowland tropical forests in Panama. We caution that although some pollinators appear abundant on the basis of census data, their long-term persistence may be highly tenuous based on genetic evidence. We propose the use of diploid male frequency data as a metric for assessing the sustainability of bee populations.     

Increased Drought Impacts on Temperate Rainforests from Southern South America: Results of a Process-Based,Dynamic Forest Model

Increased droughts due to regional shifts in temperature and rainfall regimes are likely to affect forests in temperate regions in the coming decades. To assess their consequences for forest dynamics, we need predictive tools that couple hydrologic processes, soil moisture dynamics and plant productivity. Here, we developed and tested a dynamic forest model that predicts the hydrologic balance of North Patagonian rainforests on Chiloé Island, in temperate South America (42°S). The model incorporates the dynamic linkages between changing rainfall regimes, soil moisture and individual tree growth. Declining rainfall, as predicted for the study area, should mean up to 50% less summer rain by year 2100. We analysed forest responses to increased drought using the model proposed focusing on changes in evapotranspiration, soil moisture and forest structure (above-ground biomass and basal area). We compared the responses of a young stand (YS, ca. 60 years-old) and an old-growth forest (OG, >500 years-old) in the same area. Based on detailed field measurements of water fluxes, the model provides a reliable account of the hydrologic balance of these evergreen, broad-leaved rainforests. We found higher evapotranspiration in OG than YS under current climate. Increasing drought predicted for this century can reduce evapotranspiration by 15% in the OG compared to current values. Drier climate will alter forest structure, leading to decreases in above ground biomass by 27% of the current value in OG. The model presented here can be used to assess the potential impacts of climate change on forest hydrology and other threats of global change on future forests such as fragmentation, introduction of exotic tree species, and changes in fire regimes. Our study expands the applicability of forest dynamics models in remote and hitherto overlooked regions of the world, such as southern temperate rainforests.     

An assessment of river habitat quality as an indicator of conservation status. A case study in the Northwest of Spain

There are several methodologies for the characterization and evaluation of river habitats. The scientific community has made a great effort in designing the best indexes for this purpose, and they have also been tested in different countries and rivers. Nevertheless, there has not been a transfer of that knowledge to land managers of these spaces or, at least, to those who design improvement and restoration measures. The aim of our research was the assessment of the Riparian Forest Quality Index (QBR), the “Riparian Quality Index” (RQI) and the “Fluvial Habitat Index” (IHF) as indicators of the ecological status of fluvial habitats and their application in restoration projects. The main results of this study were that the IHF index could be used as a support resource and as a monitoring tool to assess the habitat heterogeneity before and after any action is taken. However, when we evaluated the QBR and RQI indexes, the best results were with the first one. The total QBR suggests the urgency level of restoration in the section that is evaluated, and each of its sub-indexes identifies which element of the river is affected. Therefore, it will be a useful tool in decision making for the conservation of these characteristic spaces, especially for engineers who, as a result of their experience in biological and ecological processes, are involved in the design and building of ecosystems, particularly in rivers and on their banks.     

Fluctuating asymmetry as an indicator of stress: Implications for conservation biology

Extinction can be attributed broadly to environmental or genetic stress. The ability to detect such stresses before they seriously affect a population can enhance the effectiveness of conservation programs. Recent studies have shown that within-individual morphological variability may provide a valuable early indicator of environmental and genetic stress.     

Variability of the level of thermoresistance as an indicator of the functional status of a cell

Effect of acclimating temperature on the thermoresistance of isolated ciliated gill epithelium of Anodonta anatina was studied. One strip of gills from each mussel was used to determine the initial level of thermoresistance (survival time at 40 degrees C). Other strips were kept at 24 degrees C until their death, and their thermoresistance and fluorescence after Ethidium bromide staining were determined at different time intervals. After a short exposure at 24 degrees C the mean level of thermoresistance of the epithelium increased. The individual shift in the value and direction of cell thermoresistance in different mussels negatively correlated with its initial level. It resulted in narrowing the extent of individual variability of the level of thermoresistance. The prolongation of exposure at 24 degrees C decreased the mean level of thermoresistance, disturbed the negative correlation, and increased the variability of thermoresistance level. The value of cell fluorescence remained constant within 48 h. The increase in fluorescence was observed 12 h after reducing the mean thermoresistance level. Hence, the dynamics of variability in the thermoresistance level is a most sensitive indication of the cell functional state.     

The role of immigrants in the assembly of the South American rainforest tree flora

The Amazon lowland rainforest flora is conventionally viewed as comprising lineages that evolved in biogeographic isolation after the split of west Gondwana (ca. 100 Myr ago). Recent molecular phylogenies, however, identify immigrant lineages that arrived in South America during its period of oceanic isolation (ca. 100-3 Myr ago). Long-distance sweepstakes dispersal across oceans played an important and possibly predominant role. Stepping-stone migration from Africa and North America through hypothesized Late Cretaceous and Tertiary island chains may have facilitated immigration. An analysis of inventory plot data suggests that immigrant lineages comprise ca. 20% of both the species and individuals of an Amazon tree community in Ecuador. This is more than an order of magnitude higher than previous estimates. We also present data on the community-level similarity between South American and palaeotropical rainforests, and suggest that most taxonomic similarity derives from trans-oceanic dispersal, rather than a shared Gondwanan history.     

Sensitivity to reward loss as an indicator of animal emotion and welfare

The scientific study of animal emotion is an important emerging discipline in subjects ranging from neuroscience to animal welfare research. In the absence of direct measures of conscious emotion, indirect behavioural and physiological measures are used. However, these may have significant limitations (e.g. indicating emotional arousal but not valence (positivity versus negativity)). A new approach, taking its impetus from human studies, proposes that biases in information processing, and underlying mechanisms relating to the evaluation of reward gains and losses, may reliably reflect emotional valence in animals. In general, people are more sensitive to reward losses than gains, but people in a negative affective state (e.g. depression) are particularly sensitive to losses. This may underlie broader findings such as an enhanced attention to, and memory of, negative events in depressed individuals. Here we show that rats in unenriched housing, who typically exhibit indicators of poorer welfare and a more negative affective state than those in enriched housing, display a prolonged response to a decrease in anticipated food reward, indicating enhanced sensitivity to reward loss. Sensitivity to reward reduction may thus be a valuable new indicator of animal emotion and welfare.     

The oligolecty status of a specialist bee of South American Prosopis (Fabaceae) supported by pollen analysis and floral visitation methods

Despite the nest pollen provisions in Western Argentina are composed only of Prosopis, the fact that the ground-nesting bee Eremapis parvula visits several floral hosts suggested that it is a generalist bee species. In the South American Dry Chaco forest, seven nest aggregations of E. parvula were found during three different spring periods. From 34 to 73 species of floral hosts were recorded around each nest aggregation. However, all nest pollen samples were composed of Prosopis pollen alone, as previously found in nests from Western Argentina. Thus, pollen analysis proved that E. parvula is a specialist bee of Prosopis. The “monolecty” and “narrow oligolecty” pollen specialization categories cannot be differentiated using pollen analysis alone. For this reason, a complementary floral visitation method was used. As several Prosopis species have been reported in floral records, the narrow oligolecty category for E. parvula is supported here. Considering that this exomalopsine is a multivoltine bee, and that flowers of some of the more than seven Prosopis species are always available during spring, synchronization between them in rainy periods is highly probable. Thus, it is unlikely that E. parvula has to forage on alternative pollen hosts.     

Mg2+ as an indicator of nutritional status in marine bacteria

Cells maintain an osmotic pressure essential for growth and division, using organic compatible solutes and inorganic ions. Mg²⁺, which is the most abundant divalent cation in living cells, has not been considered an osmotically important solute. Here we show that under carbon limitation or dormancy native marine bacterial communities have a high cellular concentration of Mg²⁺ (370–940 m) and a low cellular concentration of Na⁺ (50–170 m). With input of organic carbon, the average cellular concentration of Mg²⁺ decreased 6–12-fold, whereas that of Na⁺ increased ca 3–4-fold. The concentration of chlorine, which was in the range of 330–1200 m and was the only inorganic counterion of quantitative significance, balanced and followed changes in the concentration of Mg²⁺+Na⁺. In an osmotically stable environment, like seawater, any major shift in bacterial osmolyte composition should be related to shifts in growth conditions, and replacing organic compatible solutes with inorganic solutes is presumably a favorable strategy when growing in carbon-limited condition. A high concentration of Mg²⁺ in cells may also serve to protect and stabilize macromolecules during periods of non-growth and dormancy. Our results suggest that Mg²⁺ has a major role as osmolyte in marine bacteria, and that the [Mg²⁺]/[Na⁺] ratio is related to its physiological condition and nutritional status. Bacterial degradation is a main sink for dissolved organic carbon in the ocean, and understanding the mechanisms limiting bacterial activity is therefore essential for understanding the oceanic C-cycle. The [Mg²⁺]/[Na⁺]-ratio in cells may provide a physiological proxy for the transitions between C-limited and mineral nutrient-limited bacterial growth in the ocean''s surface layer.     

Behaviour of birds after release from capture as an indicator of territorial status

Territorial Nuthatches which are captured and released within their territory generally start to call within a few seconds after release. Birds released outside of their territory and non-territorial individuals rarely call. This behavioural rule is found in both males and females throughout the year, and was tested experimentally by moving birds from the site of capture and releasing them elsewhere. Birds captured and released near the border of the territory show a higher tendency towards weak or undetermined responses. The generality of the behaviour makes it useful for detecting changes in territorial status of known individuals, or predicting status of unknown individuals. Some hypotheses are presented to explain the functional significance of calling after release.     

Sap flow as an indicator of transpiration and the water status of young apricot trees

The relationship between water loss via transpiration and stem sap flow in young apricot trees was studied under different environmental conditions and different levels of soil water status. The experiment was carried out in a greenhouse over a 2-week period (November 2–14, 1997) using three-year-old apricot trees (Prunus armeniaca cv. Búlida) growing in pots. Diurnal courses of leaf water potential, leaf conductance and leaf turgor potential also were recorded throughout the experiment. Data from four days of different enviromental conditions and soil water availability have been selected for analysis. On each of the selected days the leaf water potential and the mean transpiration rates were well correlated. The slope of the linear regression of this correlation, taken to indicate the total hydraulic resistance of the tree, confirmed an increasing hydraulic resistance under drought conditions. When the trees were not drought stressed the diurnal courses of sap flow and transpiration were very similar. However, when the trees were droughted, measured of sap flow slightly underestimated actual transpiration. Our heat-pulse measurements suggest the amount of readily available water stored in the stem and leaf tissues of young apricot trees is sufficient to sustain the peak transpiration rates for about 1 hour. This revised version was published online in June 2006 with corrections to the Cover Date.     

A re-valuation of the Araphidineae/Centrales index as an indicator of lake trophic status

SUMMARY. Comparisons of pre- and post-settlement diatom assemblages from the sediment of twenty-five Minnesota lakes reveals that Stephanodiscus hantzschii percentages are more consistent indicators of human disturbance than the Araphidineae/Centrales (A/C) index. In a set of eighty surface sediment samples from lakes whose water chemistry is known, S. hantzschii , a centric diatom, is abundant as a microfossil in lakes with total phosphorus > 15 μg I⁻¹ and alkalinity > 1.5 m-equiv. I⁻¹. High Araphidineae/Centrales indices are characteristic of lakes with only moderate total phosphorus levels and very low alkalinities.     

Serum extracellular superoxide dismutase activity as an indicator of zinc status in humans

The present study focused on whether serum extracellular superoxide dimutase (EC-SOD) activity can be used as a functional indicator of marginal zinc deficiency in humans. Subjects in this study were 444 healthy adults over 30 yr of age living a normal rural life in Kyunggi province, Korea. The mean dietary zinc intake of subjects obtained from one 24-h recall was 6.41 ± 4.35 mg and the average serum zinc concentration of the subjects was 11.06 ± 2.44 (μmol/L. Subjects were divided into three groups by serum zinc concentrations: adequate (serum zinc >10.7 (μmol/L), low (serum zinc 9.0–10.7 μmol/L), and very low (serum zinc <9.0 μmol/L) groups. A total of 50 subjects were selected from the three groups for analysis of EC-SOD activities. The EC-SOD activity of subjects increased with increasing serum zinc concentrations, and the activities of the three groups were significantly different as indicated by the Kruskal-Wallis test (p = 0.0239). Also, serum EC-SOD activities were significantly correlated with serum zinc concentrations (r = 0.289,p = 0.04). Serum EC-SOD activities, however, were not significantly correlated to the dietary zinc intakes. In conclusion, these results show that EC-SOD activities are decreased in subjects with low serum zinc concentrations and suggest that EC-SOD activity may be a functional indicator of zinc nutritional status in humans.     

Urea concentration in collared peccary milk as an indicator of protein nutritional status

Milk urea nitrogen (UN) concentration was examined as a possible index to protein-energy intake in female collared peccaries (Tayassu tajacu). Captive adults were bred and assigned to one of four experimental diets through gestation and lactation. Females fed a high protein diet produced milk with UN concentrations exceeding those of low-protein-fed females. A low energy intake tended to elevate UN concentrations in milk.     

Habitat associations of imperilled fishes after conservation intervention in the Cape Fold Ecoregion,South Africa

The aim of this study was to examine the habitat associations of a native cyprinid community of the recovering Rondegat River in the Cape Fold Ecoregion of South Africa as part of a long-term native fish abundance monitoring project. Relative abundance data were extracted from underwater video camera footage across the longitudinal gradient of the river in three sampling instances. Using multivariate methods the authors assessed community composition with respect to habitat, its overlap with a protected area and species-specific abiotic predictors of relative abundance. Distance from the uppermost site in the river was the most significant predictor of species abundance, indicating spatial segregation and varying overlap between species. The protected status of sites in the upper reaches, vegetated substrates and the size of individual sites were the most impactful on the relative abundance of the endangered fiery redfin Pseudobarbus phlegethon. The results of this study indicate that underwater video monitoring is an effective and low-cost approach that can inform conservation recommendations. Reducing agricultural runoff and sedimentation in the lower reaches may be useful further interventions to maintain key habitats of submerged vegetation.     

Synechococcus as an indicator of trophic status in the Cochin backwaters,west coast of India

Eutrophication is a major problem in coastal water bodies. Information about the trophic status of water bodies will enable proper management of coastal ecosystems. In this regard, biological organisms which are sensitive to environmental changes can serve as indicators of ecosystem trophic status. In this study, seasonal and spatial variations of picophytoplankton (PP; <3 μm size) community structure was assessed in the Cochin backwaters (CB) with respect to the prevailing environmental conditions during three seasons, post-monsoon (PM-I; October 2011 and PM-II; November 2012), pre-monsoon (PrM; May 2012) and monsoon (MON; August 2012). CB, along the west coast of India, receives continuous load of nutrients throughout the year through anthropogenic wastes. Trophic status index (TRIX) scores showed that CB is highly eutrophic with a high phytoplankton biomass. Synechococcus was the dominant PP observed in the study area. Seasonal and spatial salinity variations influenced the PP distribution, especially Synechococcus where PE-rich Synechococcus (SYN-PE) were dominant in higher saline (>30) and PC-rich Synechococcus (SYN-PC) in lower saline (<30) waters. SYN-PC showed a significant positive relation with chlorophyll a suggesting that this group contributes substantially to the total phytoplankton biomass. TRIX scores and SYN-PC: SYN-PE abundance ratio were negatively correlated with salinity suggesting an influence of the tidal amplitude. SYN-PC correlated positively and SYN-PE negatively with TRIX scores suggesting that these groups occupy contrasting ecological niches. These findings imply that PP distribution pattern can serve as an indicator of the trophic status of coastal water bodies.     

Spatial distribution of insect indicator taxa as a basis for peat bog conservation planning

Peat bogs are highly endangered ecosystems worldwide. In the Western Balkans, they represent fragmented habitat patches, where insect diversity and implications for the habitat loss are poorly known. Carabid beetles and ants, widely used environmental indicators, were sampled by pitfall trapping in the largest and oldest Croatian peat bog and at its edges. We found that tyrphobiontic—bog specialist—species were absent in both taxonomic groups, which is likely due to biogeographical limitation for dispersal of these species into this region. With this study, tyrphophilous—typical of bogs—species have been recognised as environmental indicators in the Western Balkans peat bogs. Assemblages of both taxa were strongly affected by specific conditions in the peat bog – high soil moisture and Sphagnum moss dominance, showing that edges are more favourable habitats for both taxa. Overall, carabid beetle activity density was significantly higher at the edge than at the peat bog, while species richness increased for both taxa at the edge, but not significantly. Spatial distribution of tyrphophilous species differed between studied taxa, with ants being more abundant in the peat bog, and carabid beetles at the edge. Additionally, some stenotopic and globally endangered species preferred edges. Occurrence of tyrphophilous and globally endangered species highlights the great conservation value of peat bog habitats in the Western Balkans. However, successional changes in vegetation are changing hydrological conditions of the peat bog. Here we suggest active conservation measures to preserve these unique soil invertebrate zoocoenoses.     

Ancient DNA reveals Holocene loss of genetic diversity in a South American rodent

Understanding how animal populations have evolved in response to palaeoenvironmental conditions is essential for predicting the impact of future environmental change on current biodiversity. Analyses of ancient DNA provide a unique opportunity to track population responses to prehistoric environments. We explored the effects of palaeoenvironmental change on the colonial tuco-tuco (Ctenomys sociabilis), a highly endemic species of Patagonian rodent that is currently listed as threatened by the IUCN. By combining surveys of modern genetic variation from throughout this species' current geographic range with analyses of DNA samples from fossil material dating back to 10,000 ybp, we demonstrate a striking decline in genetic diversity that is concordant with environmental events in the study region. Our results highlight the importance of non-anthropogenic factors in loss of diversity, including reductions in smaller mammals such as rodents.