Temporal response of the tiger salamander (<Emphasis Type="Italic">Ambystoma tigrinum</Emphasis>) to 3,000 years of climatic variation

Background  

Amphibians are sensitive indicators of environmental conditions and show measurable responses, such as changes in phenology, abundance and range limits to local changes in precipitation and temperature regimes. Amphibians offer unique opportunities to study the important ecological and evolutionary implications of responses in life history characteristics to climatic change. We analyzed a late-Holocene fossil record of the Tiger Salamander (Ambystoma tigrinum) for evidence of population-level changes in body size and paedomorphosis to climatic change over the last 3000 years.     

Age-dependent induction of immunity and subsequent survival costs in males and females of a temperate damselfly

Background  

To understand variation in resistance to parasites within host populations, researchers have examined conditions under which immunity is induced and/or is costly. Both host sex and age have been found to influence immune expression and subsequently are likely factors influencing the costs of resistance. The purpose of this study was to examine immune expression and associated survival costs for two age groups (newly emerged and sexually mature individuals) of the damselfly, Enallagma boreale Selys. Survival was assessed for experimentally challenged and control damselflies, housed initially at 22°C and then subjected to low temperatures (15°C) associated with reduced foraging activity and food deprivation. Experimental conditions emulated natural local variation in bouts of good weather followed by inclement weather (successions of days with hourly mean temperatures around 15°C and/or rainy weather).     

Richness of Colchic vegetation: comparison between refugia of south-western and East Asia

Background  

The Colchis is one of the species-rich refugia and a centre of biological diversity in western Eurasia. We analysed patterns of richness, endemism and invasions in relation to taxonomy (family membership), life form, certain habitats in the Colchis, and compared them to patterns found for Japan.     

The effect of environmental change on vascular plant and cryptogam communities from the Falkland Islands and the Maritime Antarctic

Background  

Antarctic terrestrial vegetation is subject to one of the most extreme climates on Earth. Currently, parts of Antarctica are one of the fastest warming regions on the planet. During 3 growing seasons, we investigated the effect of experimental warming on the diversity and abundance of coastal plant communities in the Maritime Antarctic region (cryptogams only) and the Falkland Islands (vascular plants only). We compared communities from the Falkland Islands (51°S, mean annual temperature 7.9°C), with those of Signy Island (60°S, -2.1°C) and Anchorage Island (67°S, -2.6°C), and experimental temperature manipulations at each of the three islands using Open Top Chambers (OTCs).     

Predictors for presence and abundance of small mammals in households of villages endemic for commensal rodent plague in Yunnan Province,China

Background  

Ninety-one rodent plague epidemics have occurred in Lianghe county, Yunnan Province, China, between 1990 and 2006. This study aimed to identify predictors for the presence and abundance of small mammals in households of villages endemic for rodent plague in Lianghe county.     

Diversity and abundance of photosynthetic sponges in temperate Western Australia

Background  

Photosynthetic sponges are important components of reef ecosystems around the world, but are poorly understood. It is often assumed that temperate regions have low diversity and abundance of photosynthetic sponges, but to date no studies have investigated this question. The aim of this study was to compare the percentages of photosynthetic sponges in temperate Western Australia (WA) with previously published data on tropical regions, and to determine the abundance and diversity of these associations in a range of temperate environments.     

Cross-taxon congruence and environmental conditions

Background  

Diversity patterns of different taxa typically covary in space, a phenomenon called cross-taxon congruence. This pattern has been explained by the effect of one taxon diversity on taxon diversity, shared biogeographic histories of different taxa, and/or common responses to environmental conditions. A meta-analysis of the association between environment and diversity patterns found that in 83 out of 85 studies, more than 60% of the spatial variability in species richness was related to variables representing energy, water or their interaction. The role of the environment determining taxa diversity patterns leads us to hypothesize that this would explain the observed cross-taxon congruence. However, recent analyses reported the persistence of cross-taxon congruence when environmental effect was statistically removed. Here we evaluate this hypothesis, analyzing the cross-taxon congruence between birds and mammals in the Brazilian Cerrado, and assess the environmental role on the spatial covariation in diversity patterns.     

The world's richest tadpole communities show functional redundancy and low functional diversity: ecological data on Madagascar's stream-dwelling amphibian larvae

Background  

Functional diversity illustrates the range of ecological functions in a community. It allows revealing the appearance of functional redundancy in communities and processes of community assembly. Functional redundancy illustrates the overlap in ecological functions of community members which may be an indicator of community resilience. We evaluated patterns of species richness, functional diversity and functional redundancy on tadpole communities in rainforest streams in Madagascar. This habitat harbours the world's most species-rich stream tadpole communities which are due to their occurrence in primary habitat of particular interest for functional diversity studies.     

Flower strip networks offer promising long term effects on pollinator species richness in intensively cultivated agricultural areas

Background

Intensively cultivated agricultural landscapes often suffer from substantial pollinator losses, which may be leading to decreasing pollination services for crops and wild flowering plants. Conservation measures that are easy to implement and accepted by farmers are needed to halt a further loss of pollinators in large areas under intensive agricultural management. Here we report the results of a replicated long-term study involving networks of mostly perennial flower strips covering 10% of a conventionally managed agricultural landscape in southwestern Germany.

Results

We demonstrate the considerable success of these measures for wild bee and butterfly species richness over an observation period of 5 years. Overall species richness of bees and butterflies but also the numbers of specialist bee species clearly increased in the ecological enhancement areas as compared to the control areas without ecological enhancement measures. A three to five-fold increase in species richness was found after more than 2 years of enhancement of the areas with flower strips. Oligolectic bee species increased significantly only after the third year.

Conclusions

In our long-term field experiment we used a large variety of seed mixtures and temporal variation in seeding time, ensured continuity of the flower-strips by using perennial seed mixtures and distributed the measures over c. 10% of the landscape. This led to an increase in pollinator abundance, suggesting that these measures may be instrumental for the successful support of pollinators. These measures may ensure the availability of a network of diverse habitats and foraging resources for pollinators throughout the year, as well as nesting sites for many species. The measures are applied in-field and are suitable for application in areas under intensive agriculture. We propose that flower strip networks should be implemented much more in the upcoming CAP (common agricultural policy) reform in the European Union and promoted more by advisory services for farmers.

     

Flow regime shapes seasonal patterns of fish species richness and abundance in main and branch channels of a rice irrigation system

Current modernization of an irrigation system degrades fish habitats in quantity and quality and is a significant concern for biodiversity conservation and management of ecosystem services in rice farming landscapes. Irrigation systems consist of various types of channels, whose hydrological and hydraulic heterogeneities can contribute to the coexistence of diverse fish species in this flooded habitat. We compared seasonal patterns of fish species richness and abundance between main and branch channels which have different functions in an irrigation system with different flow temporality and magnitude: the main channels (mean width 425 cm and mean discharge 0.467 m³/s in irrigation period) and the branch channels (176 cm and 0.115 m³/s, respectively). The branch channels are small and temporary, but densities of fish species richness and abundance were not smaller than the main channels during the irrigation period. Further, clear positive hysteretic loops in species richness and abundance with discharge were found in the branch channels, which indicates that fish species richness and abundance gradually increased with discharge during this hydroperiod. Water velocity strongly constrained species richness and abundance in the main channels but not in the branch channels partially because of slow-flow patches at microhabitat scale with a larger vegetation coverage. We also found that the main channels provided deeper habitats in the non-irrigation period and contributed to maintain fish species richness and abundance. Therefore, managing both the main and branch channels as an indispensable, interconnected channel network can be a key for fish habitat conservation in an irrigation system.     

Estimating species pools for a single ecological assemblage

Background

The species pool concept was formulated over the past several decades and has since played an important role in explaining multi-scale ecological patterns. Previous statistical methods were developed to identify species pools based on broad-scale species range maps or community similarity computed from data collected from many areas. No statistical method is available for estimating species pools for a single local community (sampling area size may be very small as ≤ 1 km²). In this study, based on limited local abundance information, we developed a simple method to estimate the area size and richness of a species pool for a local ecological community. The method involves two steps. In the first step, parameters from a truncated negative trinomial model characterizing the distributional aggregation of all species (i.e., non-random species distribution) in the local community were estimated. In the second step, we assume that the unseen species in the local community are most likely the rare species, only found in the remaining part of the species pool, and vice versa, if the remaining portion of the pool was surveyed and was contrasted with the sampled area. Therefore, we can estimate the area size of the pool, as long as an abundance threshold for defining rare species is given. Since the size of the pool is dependent on the rarity threshold, to unanimously determine the pool size, we developed an optimal method to delineate the rarity threshold based on the balance of the changing rates of species absence probabilities in the sampled and unsampled areas of the pool.

Results

For a 50 ha (0.5 km²) forest plot in the Barro Colorado Island of central Panama, our model predicted that the local, if not regional, species pool for the 0.5 km² forest plot was nearly the entire island. Accordingly, tree species richness in this pool was estimated as around 360. When the sampling size was smaller, the upper bound of the 95% confidence interval could reach 418, which was very close to the flora record of tree richness for the island. A numerical test further demonstrated the power and reliability of the proposed method, as the true values of area size and species richness for the hypothetical species pool have been well covered by the 95% confidence intervals of the true values.

Conclusions

Our method fills the knowledge gap on estimating species pools for a single local ecological assemblage with little information. The method is statistically robust and independent of sampling size, as proved by both empirical and numerical tests.

     

Species-specific interference exerted by the shrub <Emphasis Type="Italic">Cistus clusii</Emphasis> Dunal in a semi-arid Mediterranean gypsum plant community

Background

The gypsovag shrub Cistus clusii is locally dominant in semi-arid gypsum plant communities of North-Eastern Spain. This species commonly grows in species-poor patches even though it has nurse potential, suggesting interference on neighbouring species. Other Cistus species exert a chemically mediated interference on plant communities, suggesting that it might be a common phenomenon in this genus. This study aimed investigating whether C. clusii exerts chemically mediated interference on neighbouring species in gypsum plant communities. We tested in a greenhouse whether aqueous extracts from C. clusii leaves (L), roots (R) and a mixture of both (RL) affected germination, seedling survival, and growth of nine native species of gypsum communities, including C. clusii itself. We further assessed in the field richness and abundance of plants under the canopy of C. clusii compared to Gypsophila struthium (shrub with a similar architecture having a nurse role) and in open patches. Finally, we specifically assessed in the field the influence of C. clusii on the presence of the species tested in the greenhouse experiment.

Results

Aqueous extracts from C. clusii (R and RL) negatively affected either germination or survival in four of nine species. In the field, richness and abundance of plants were lower under the canopy of C. clusii than under G. struthium, but higher than in open patches. Specifically, five of nine species were less frequent than expected under the canopy of C. clusii.

Conclusions

Cistus clusii shows species-specific interference with neighbouring species in the community, which may be at least partially attributable to its phytotoxic activity. To our knowledge, this is the first report of species-specific interference by C. clusii.

     

Environmental DNA sequencing primers for eutardigrades and bdelloid rotifers

Background  

The time it takes to isolate individuals from environmental samples and then extract DNA from each individual is one of the problems with generating molecular data from meiofauna such as eutardigrades and bdelloid rotifers. The lack of consistent morphological information and the extreme abundance of these classes makes morphological identification of rare, or even common cryptic taxa a large and unwieldy task. This limits the ability to perform large-scale surveys of the diversity of these organisms.     

Inter-annual variation in prevalence and intensity of mite parasitism relates to appearance and expression of damselfly resistance

Background  

Insects can resist parasites using the costly process of melanotic encapsulation. This form of physiological resistance has been studied under laboratory conditions, but the abiotic and biotic factors affecting resistance in natural insect populations are not well understood. Mite parasitism of damselflies was studied in a temperate damselfly population over seven seasons to determine if melanotic encapsulation of mite feeding tubes was related to degree of parasitism, host sex, host size, emergence timing, duration of the emergence period, and average daily air temperature.     

Impact of biodiversity-climate futures on primary production and metabolism in a model benthic estuarine system

Background  

Understanding the effects of anthropogenically-driven changes in global temperature, atmospheric carbon dioxide and biodiversity on the functionality of marine ecosystems is crucial for predicting and managing the associated impacts. Coastal ecosystems are important sources of carbon (primary production) to shelf waters and play a vital role in global nutrient cycling. These systems are especially vulnerable to the effects of human activities and will be the first areas impacted by rising sea levels. Within these coastal ecosystems, microalgal assemblages (microphytobenthos: MPB) are vital for autochthonous carbon fixation. The level of in situ production by MPB mediates the net carbon cycling of transitional ecosystems between net heterotrophic or autotrophic metabolism. In this study, we examine the interactive effects of elevated atmospheric CO₂ concentrations (370, 600, and 1000 ppmv), temperature (6°C, 12°C, and 18°C) and invertebrate biodiversity on MPB biomass in experimental systems. We assembled communities of three common grazing invertebrates (Hydrobia ulvae, Corophium volutator and Hediste diversicolor) in monoculture and in all possible multispecies combinations. This experimental design specifically addresses interactions between the selected climate change variables and any ecological consequences caused by changes in species composition or richness.     

Within-host competitive exclusion among species of the anther smut pathogen

Background  

Host individuals represent an arena in which pathogens compete for resources and transmission opportunities, with major implications for the evolution of virulence and the structure of populations. Studies to date have focused on competitive interactions within pathogen species, and the level of antagonism tends to increase with the genetic distance between competitors. Anther-smut fungi, in the genus Microbotryum, have emerged as a tractable model for within-host competition. Here, using two pathogen species that are frequently found in sympatry, we investigated whether the antagonism seen among genotypes of the same species cascades up to influence competition among pathogen species.     

Impacts of feral horses on a desert environment

Background  

Free-ranging horses (Equus caballus) in North America are considered to be feral animals since they are descendents of non-native domestic horses introduced to the continent. We conducted a study in a southern California desert to understand how feral horse movements and horse feces impacted this arid ecosystem. We evaluated five parameters susceptible to horse trampling: soil strength, vegetation cover, percent of nonnative vegetation, plant species diversity, and macroinvertebrate abundance. We also tested whether or not plant cover and species diversity were affected by the presence of horse feces.     

Spurious and functional correlates of the isotopic composition of a generalist across a tropical rainforest landscape

Background  

The isotopic composition of generalist consumers may be expected to vary in space as a consequence of spatial heterogeneity in isotope ratios, the abundance of resources, and competition. We aim to account for the spatial variation in the carbon and nitrogen isotopic composition of a generalized predatory species across a 500 ha. tropical rain forest landscape. We test competing models to account for relative influence of resources and competitors to the carbon and nitrogen isotopic enrichment of gypsy ants (Aphaenogaster araneoides), taking into account site-specific differences in baseline isotope ratios.     

A specialist-generalist classification of the arable flora and its response to changes in agricultural practices

Background  

Theory in ecology points out the potential link between the degree of specialisation of organisms and their responses to disturbances and suggests that this could be a key element for understanding the assembly of communities. We evaluated this question for the arable weed flora as this group has scarcely been the focus of ecological studies so far and because weeds are restricted to habitats characterised by very high degrees of disturbance. As such, weeds offer a case study to ask how specialization relates to abundance and distribution of species in relation to the varying disturbance regimes occurring in arable crops.     

Model-supported estimation of mortality rates in Baltic cod (<Emphasis Type="Italic">Gadus morhua callarias</Emphasis> L.) larvae: the varying impact of 'critical periods'

Background  

Changes in the survival-rate during the larval phase may strongly influence the recruitment level in marine fish species. During the larval phase different 'critical periods' are discussed, e.g. the hatching period and the first-feeding period. No such information was available for the Baltic cod stock, a commercially important stock showing reproduction failure during the last years. We calculated field-based mortality rates for larval Baltic cod during these phases using basin-wide abundance estimates from two consecutive surveys. Survey information was corrected by three dimensional hydrodynamic model runs.