Ecological study of <Emphasis Type="Italic">Paracoccidioides brasiliensis</Emphasis> in soil: growth ability,conidia production and molecular detection

Background  

Paracoccidioides brasiliensis ecology is not completely understood, although several pieces of evidence point to the soil as its most probable habitat. The present study aimed to investigate the fungal growth, conidia production and molecular pathogen detection in different soil conditions.     

Incorporating asymmetric movement costs into measures of habitat connectivity to assess impacts of hydrologic alteration to stream fishes

Aim

Hydrologic alterations are widespread in freshwater ecosystems worldwide and often detrimentally impact fish populations. Habitat suitability models are commonly used to assess these impacts, but these models frequently rely upon observed fish–habitat relationships rather than more mechanistic underpinnings. The aim of this study was to demonstrate how to incorporate swim performance into a measure of habitat connectivity at a fine scale, providing a method for assessing the availability of suitable habitat for stream fishes.

Location

We applied this technique to an endangered species, the Western Silvery Minnow Hybognathus argyritis, in the Milk River of southern Alberta, Canada. The Milk River is an augmented system, where a diversion in nearby St. Mary River augments flow by a factor >3 × (from 1–5 m³/s to 15–20 m³/s).

Methods

We used laboratory measured swim performance of Western Silvery Minnow to develop a movement cost function that was used in conjunction with a habitat suitability model to assess habitat availability via a recently developed graph‐theoretic metric, equivalent connected area (ECA).

Results

Stream augmentation altered not only habitat suitability but also habitat connectivity for this species. During augmentation, suitable habitat area declined by 81.3%. Changes in habitat connectivity were site dependent. Movement costs between habitat patches were lower during augmentation due to current‐assisted dispersal and increased distance to patches during natural flows from dried streambeds. When movement costs were incorporated into ECA, ECA decreased by 78.0% during augmentation.

Main conclusions

With changing climate and increasing anthropogenic impacts on aquatic ecosystems, understanding how freshwater fishes relate to their habitat is critical for appropriate management. In many cases, such as the Western Silvery Minnow, mitigating habitat suitability may not be sufficient, as species are unable to reach suitable habitat. The incorporation of swim performance into habitat connectivity assessments, as carried out here, can be easily adapted to other species and situations and can improve the understanding of impacts to stream fishes and increase the effectiveness of mitigation efforts.     

A new allele of flower color gene <Emphasis Type="Italic">W1</Emphasis> encoding flavonoid 3'5'-hydroxylase is responsible for light purple flowers in wild soybean <Emphasis Type="Italic">Glycine soja</Emphasis>

Background  

Glycine soja is a wild relative of soybean that has purple flowers. No flower color variant of Glycine soja has been found in the natural habitat.     

Canopy height and competition explain species segregation in wet heathlands

Questions

What is the general pattern of species co‐occurrence in managed heathlands? Is the pattern consistent among functional groups? Is it ruled by species competition, or by contrasting environments at a fine scale? Does grazing pressure and herbivore species condition species interactions?

Location

Erica mackayana wet heaths, Galicia, NW Iberian Peninsula.

Methods

A null model approach was used to compare species co‐occurrence with generated random matrices from 54 10‐m transects. The C‐score was obtained from the multispecies presence/absence matrix for each transect of shrubs and graminoids recorded at 25‐cm intervals. Differences in canopy height were recorded to assess the importance of the environment compared to inter‐specific competition. Results were linked to different levels of grazing pressure and herbivore species.

Results

Species segregation was the main pattern for all species, but mainly among graminoid species compared to shrubs. Graminoids showed an even proportion of segregated pairs explained by different canopy heights and competition. These differences were mainly species environmental requirements of canopy height. Levels of grazing pressure enhanced species segregation in graminoids but had no effect on shrubs or the total species set.

Conclusions

Competition and canopy height affect the E. mackayana heathland composition, but differently for functional groups. A heterogeneous vegetation profile with shrub mats and open gaps created by light grazing promotes species co‐existence within mats and competition in gaps. I suggest this is an optimum structure for the habitat to be targeted through management.

     

Rates of evolution in stress-related genes are associated with habitat preference in two <Emphasis Type="Italic">Cardamine</Emphasis> lineages

Background  

Elucidating the selective and neutral forces underlying molecular evolution is fundamental to understanding the genetic basis of adaptation. Plants have evolved a suite of adaptive responses to cope with variable environmental conditions, but relatively little is known about which genes are involved in such responses. Here we studied molecular evolution on a genome-wide scale in two species of Cardamine with distinct habitat preferences: C. resedifolia, found at high altitudes, and C. impatiens, found at low altitudes. Our analyses focussed on genes that are involved in stress responses to two factors that differentiate the high- and low-altitude habitats, namely temperature and irradiation.     

Comparative phylogeography of two co‐distributed but ecologically distinct rainbowfishes of far‐northern Australia

Aim

To test the influence of historical and contemporary environment in shaping the genetic diversity of freshwater fauna we contrast genetic structure in two co‐distributed, but ecologically distinct, rainbowfish; a habitat generalist (Melanotaenia splendida) and a habitat specialist (M. trifasciata).

Location

Fishes were sampled from far northern Australia (Queensland and Northern Territory).

Methods

We used sequence data from one mitochondrial gene and one nuclear gene to investigate patterns of genetic diversity in M. splendida and M. trifasciata to determine how differences in habitat preference and historical changes in drainage boundaries affected patterns of connectivity.

Results

Melanotaenia splendida showed high levels of genetic diversity and little population structure across its range. In contrast, M. trifasciata showed high levels of population structure. Whereas phylogeographic patterns differed, both species showed a strong relationship between geographical distance and genetic differentiation between populations. Melanotaenia splendida showed a shallower relationship with geographical distance, and genetic differentiation was best explained by stream length and a lower scaled ocean distance (11.98 times coast length). For M. trifasciata, genetic differentiation was best explained by overwater distance between catchments and ocean distance scaled at 1.16 × 10⁶ times coast length.

Main conclusions

Connectivity of freshwater populations inhabiting regions periodically interconnected during glacial periods appears to have been affected by ecological differences between species. Species‐specific differences are epitomized here by the contrast between co‐distributed congeners with different habitat requirements: for the habitat generalist, M. splendida, there was evidence for greater historical genetic connectivity with oceans as a weaker barrier to gene exchange in contrast with the habitat specialist, M. trifasciata.     

Segregation in space and time explains the coexistence of two sympatric sub‐Antarctic petrels

Biological communities are shaped by competition between and within species. Competition is often reduced by inter‐ and intraspecific specialization on resources, such as differencet foraging areas or time, allowing similar species to coexist and potentially contributing to reproductive isolation. Here, we examine the simultaneous role of temporal and spatial foraging segregation within and between two sympatric sister species of seabirds, Northern Macronectes halli and Southern Macronectes giganteus Giant Petrels. These species show marked sexual size dimorphism and allochrony (with earlier breeding by Northern Giant Petrels) but this is the first study to test for differences in foraging behaviours and areas across the entire breeding season both between the two species and between the sexes. We tracked males and females of both species in all breeding stages at Bird Island, South Georgia, to test how foraging distribution, behaviour and habitat use vary between and within species in biological time (incubation, brood‐guard or post‐brood stages) and in absolute time (calendar date). Within each breeding stage, both species took trips of comparable duration to similar areas, but due to breeding allochrony they segregated temporally. Northern Giant Petrels had a somewhat smaller foraging range than Southern Giant Petrels, reflecting their greater exploitation of local carrion and probably contributing to their recent higher population growth. Within species, segregation was spatial, with females generally taking longer, more pelagic trips than males, although both sexes of both species showed unexpectedly plastic foraging behaviour. There was little evidence of interspecific differences in habitat use. Thus, in giant petrels, temporal segregation reduces interspecific competition and sexual segregation reduces intraspecific competition. These results demonstrate how both specialization and dynamic changes in foraging strategies at different scales underpin resource division within a community.     

The dynamics of coexistence: habitat sharing versus segregation patterns among three sympatric montane vipers

Contact zones of closely related and ecologically similar species constitute rare opportunities to study the evolutionary consequences of past speciation processes. They represent natural laboratories in which strong competition could lead to the exclusion of one species, or the various species may switch into distinct ecological niches. Alternatively, if reproductive isolation has not yet been achieved, they may hybridize. We elucidate the degree of taxon integrity by comparing genetics and habitat use of three similar‐sized congeneric viper species, Vipera ammodytes, Vipera aspis, and Vipera berus, of Nadiza Valley in western Slovenia. No hybridization was detected for either mitochondrial or nuclear genomes. Similarly, external intermediacy by a single prestudy viper (probably V. ammodytes × V. aspis) indicates that hybridization occasionally occurs, but should be very rare. Populations of the three related viperids are partially allopatric in Nadiza Valley, but they also coexist in a narrow contact zone in the montane grassland along the south‐exposed slope of Mount Stol (1673 m a.s.l.). Here, the three species that occupy areas in or near patches of rocky microhabitats (e.g. stone piles, slides, and walls) live in syntopy. However, fine‐scale measurements of structural components show partial habitat segregation, in which V. berus becomes more dominant at elevations above 1400 m and occupies mostly the mountain ridge and north‐exposed slopes of Mount Stol, V. aspis occurs below 1300 m and is the only species to inhabit stoneless patches of grass and bushes around 1000 m and lower, and V. ammodytes occurs at all elevations up to 1500 m, but is restricted to a rocky microhabitat. We suggest that a high degree of microstructure divergence, slightly different environmental niches, and a generally favourable habitat for all three viper species, keep the pressure for mis‐mating and hybridization low, although mechanisms such as reduced hybrid inferiority and temporal mating segregation cannot yet be excluded.     

Human appropriation of net primary production as driver of change in landscape-scale vertebrate richness

Aim

Land use is the most pervasive driver of biodiversity loss. Predicting its impact on species richness (SR) is often based on indicators of habitat loss. However, the degradation of habitats, especially through land-use intensification, also affects species. Here, we evaluate whether an integrative metric of land-use intensity, the human appropriation of net primary production, is correlated with the decline of SR in used landscapes across the globe.

Location

Global.

Time period

Present.

Major taxa studied

Birds, mammals and amphibians.

Methods

Based on species range maps (spatial resolution: 20 km × 20 km) and an area-of-habitat approach, we calibrated a “species–energy model” by correlating the SR of three groups of vertebrates with net primary production and biogeographical covariables in “wilderness” areas (i.e., those where available energy is assumed to be still at pristine levels). We used this model to project the difference between pristine SR and the SR corresponding to the energy remaining in used landscapes (i.e., SR loss expected owing to human energy extraction outside wilderness areas). We validated the projected species loss by comparison with the realized and impending loss reconstructed from habitat conversion and documented by national Red Lists.

Results

Species–energy models largely explained landscape-scale variation of mapped SR in wilderness areas (adjusted R²-values: 0.79–0.93). Model-based projections of SR loss were lower, on average, than reconstructed and documented ones, but the spatial patterns were correlated significantly, with stronger correlation in mammals (Pearson's r = 0.68) than in amphibians (r = 0.60) and birds (r = 0.57).

Main conclusions

Our results suggest that the human appropriation of net primary production is a useful indicator of heterotrophic species loss in used landscapes, hence we recommend its inclusion in models based on species–area relationships to improve predictions of land-use-driven biodiversity loss.     

High climate velocity and population fragmentation may constrain climate‐driven range shift of the key habitat former Fucus vesiculosus

Aim

The Baltic Sea forms a unique regional sea with its salinity gradient ranging from marine to nearly freshwater conditions. It is one of the most environmentally impacted brackish seas worldwide, and the low biodiversity makes it particularly sensitive to anthropogenic pressures including climate change. We applied a novel combination of models to predict the fate of one of the dominant foundation species in the Baltic Sea, the bladder wrack Fucus vesiculosus.

Location

The Baltic Sea.

Methods

We used a species distribution model to predict climate change‐induced displacement of F. vesiculosus and combined these projections with a biophysical model of dispersal and connectivity to explore whether the dispersal rate of locally adapted genotypes may match estimated climate velocities to recolonize the receding salinity gradient. In addition, we used a population dynamic model to assess possible effects of habitat fragmentation.

Results

The species distribution model showed that the habitat of F. vesiculosus is expected to dramatically shrink, mainly caused by the predicted reduction of salinity. In addition, the dispersal rate of locally adapted genotypes may not keep pace with estimated climate velocities rendering the recolonization of the receding salinity gradient more difficult. A simplistic model of population dynamics also indicated that the risk of local extinction may increase due to future habitat fragmentation.

Main conclusions

Results point to a significant risk of locally adapted genotypes being unable to shift their ranges sufficiently fast considering the restricted dispersal and long generation time. The worst scenario is that F. vesiculosus may disappear from large parts of the Baltic Sea before the end of this century with large effects on the biodiversity and ecosystem functioning. We finally discuss how to reduce this risk through conservation actions, including assisted colonization and assisted evolution.     

Vegetation change in acidic dry grasslands in Moravia (Czech Republic) over three decades: Slow decrease in habitat quality after grazing cessation

Aims

Shallow soils on acidic bedrock in dry areas of Central Europe support dry grasslands and heathlands that were formerly used as extensive pastures. These habitats are of high conservation value, but their abandonment in the 20th century triggered slow natural succession that poses a threat to specialized plant species. We asked how this vegetation and its plant diversity have changed over the past three decades and whether protected areas have positively affected habitat quality.

Location

Southwestern and central Moravia, Czech Republic.

Methods

In 2018–2019, we resurveyed 94 vegetation plots first sampled in 1986–1991 at 47 acidic dry grassland and heathland sites. We compared the number of all vascular plant species, Red List species and alien species per plot using parametric and non-parametric tests, life-form spectra using the chi-square test, species composition using detrended correspondence analysis, and indicator values using a permutation test. We also compared these changes between sites within and outside protected areas.

Results

Vegetation changes over the past three decades have been relatively small. However, we detected a decrease in total species richness, the number of Red List species and the number of characteristic species of dry grasslands. Neophytes were infrequent, while archaeophytes increased slightly. The competitive tall grass Arrhenatherum elatius, annual species and young woody plants increased in abundance or newly established at many sites. Indicator values did not change except for a slight increase in nutrient values. These negative trends occurred both within and outside protected areas but were more pronounced outside.

Conclusions

Formerly grazed acidic dry grasslands and heathlands in Moravia are slowly losing habitat specialists, including threatened plant species, and are increasingly dominated by Arrhenatherum elatius. Conservation management, especially cutting in protected areas, slows down the negative trends of decline in plant diversity and habitat quality but is insufficient to halt these processes completely.     

Association of <Emphasis Type="Italic">Bordetella</Emphasis> dermonecrotic toxin with the extracellular matrix

Background  

Bordetella dermonecrotic toxin (DNT) causes the turbinate atrophy in swine atrophic rhinitis, caused by a Bordetella bronchiseptica infection of pigs, by inhibiting osteoblastic differentiation. The toxin is not actively secreted from the bacteria, and is presumed to be present in only small amounts in infected areas. How such small amounts can affect target tissues is unknown.     

Coexistence of protected avian predators: does a recovering population of White-tailed Eagle threaten to exclude other avian predators?

The processes of competition and predation determine the degree to which species can coexist; the importance of competition in particular has been emphasized at high trophic levels. Competition exclusion will occur when habitat overlap between sympatric species is high. In this study, we investigated nesting habitat overlap between internationally protected diurnal tree-nesting avian predators of central Europe, namely, White-tailed Eagle (Haliaeetus albicilla), Lesser Spotted Eagle (Aquila pomarina), Black Stork (Ciconia nigra), and Osprey (Pandion haliaetus). We found significantly different nesting habitats among the study species and suggest that this could be a consequence of the resource-based segregation, but not a consequence of asymmetrical interspecific competition. The results also show that habitat of the recovering populations of White-tailed Eagle overlapped with the habitat used by the Lesser Spotted Eagle, Black Stork, and Osprey to varying extents with a niche overlap values being below the competition exclusion threshold. Nevertheless, we suggest that competition by White-tailed Eagle at a population level may limit Osprey, though not Lesser Spotted Eagle or Black Stork.     

Female-driven mechanisms,ejaculate size and quality contribute to the lower fertility of <Emphasis Type="Italic">sex-ratio</Emphasis> distorter males in <Emphasis Type="Italic">Drosophila simulans</Emphasis>

Background  

Sex-ratio meiotic drive refers to the preferential transmission of the X chromosome by XY males. The loss of Y-bearing sperm is caused by an X-linked distorter and results in female-biased progeny. The fertility of sex-ratio (SR) males expressing the distorter is usually strongly reduced compared to wild-type males, especially when they are in competition. The aim of this study was to identify the post-copulatory mechanisms that lower the fertility of SR males in Drosophila simulans. Parameters contributing to male fertility were measured in single and double mating conditions.     

Lack of habitat segregation and no interspecific territoriality in three syntopic cryptic species of the golden‐spectacled warblers Phylloscopus (Seicercus) burkii complex

It is widely accepted that exploitative competition prevents the coexistence of any two or more closely‐related species unless differences exists in their ecological niches and resource use. In sibling bird species, exploitative competition is reduced mainly by spatial segregation of competing species. Spatial segregation can be achieved in two basic ways: by using different habitats or microhabitats that each species is predominately exploiting, or by interspecific territoriality. To our knowledge, either habitat segregation or interspecific territoriality or both have been found in all dyads and groups of sympartic sibling bird species studied so far. In this study, we investigated the coexistence of three cryptic sibling species of the golden‐spectacled warblers Phylloscopus burkii complex in Hunan Province, China: Ph. tephrocephalus, Ph. omeiensis and Ph. valentini. We analyzed their habitat preferences, and spatial interrelations between the species. In order to analyze either presence or absence of interspecific territoriality, we additionally performed con‐ and heterospecific playback experiments. Contrary to expectations, we found no evidences for either habitat segregation or interspecific territoriality in these three species.     

Gene expression following induction of regeneration in <Emphasis Type="Italic">Drosophila</Emphasis> wing imaginal discs. Expression profile of regenerating wing discs

Background  

Regeneration is the ability of an organism to rebuild a body part that has been damaged or amputated, and can be studied at the molecular level using model organisms. Drosophila imaginal discs, which are the larval primordia of adult cuticular structures, are capable of undergoing regenerative growth after transplantation and in vivo culture into the adult abdomen.     

The ecology of nasal colonization of Streptococcus pneumoniae, Haemophilus influenzae and Staphylococcus aureus: the role of competition and interactions with host's immune response

Background  

The first step in invasive disease caused by the normally commensal bacteria Streptococcus pneumoniae, Staphylococcus aureus and Haemophilus influenzae is their colonization of the nasal passages. For any population to colonize a new habitat it is necessary for it to be able to compete with the existing organisms and evade predation. In the case of colonization of these species the competition is between strains of the same and different species of bacteria and the predation is mediated by the host's immune response. Here, we use a neonatal rat model to explore these elements of the ecology of nasal colonization by these occasionally invasive bacteria.     

Characterization of <Emphasis Type="Italic">Mycobacterium tuberculosis</Emphasis> Beijing isolates from the Mediterranean area

Background  

The Beijing lineage of Mycobacterium tuberculosis is causing concern due to its global distribution and its involvement in severe outbreaks. Studies focused on this lineage are mainly restricted to geographical settings where its prevalence is high, whereas those in other areas are scarce. In this study, we analyze Beijing isolates in the Mediterranean area, where this lineage is not prevalent and is mainly associated with immigrant cases.     

Depth and temperature drive patterns of spatial overlap among fish thermal guilds in lakes across Ontario,Canada

Aim

The spatial distribution of ectotherms is strongly dependent on the temperature of their environments. In temperate lakes, fishes with different thermal optima can become spatially segregated during summer stratification. This habitat partitioning, or niche complementarity, may play a role in the coexistence of trophically similar species; however, the extent of partitioning is dependent on the resources available within each habitat. Although habitat partitioning of fish thermal guilds has been studied in individual lakes, broad-scale patterns of spatial overlap and segregation are not yet understood. In this study, we explore the patterns and drivers of spatial overlap among thermal guilds (cold-, cool-, and warm-water) at a broad scale.

Location

Ontario, Canada.

Methods

We built a multivariate regression tree to explore patterns and environmental drivers of spatial overlap in freshwater fishes across three thermal guilds from 438 lakes.

Results

We identified five clusters of lakes exhibiting different patterns of spatial overlap among the three thermal guilds. Temperature (growing degree days) and maximum lake depth were strong drivers of the spatial overlap patterns.

Main Conclusions

These findings provide a better understanding of broad-scale patterns of spatial overlap and allow us to predict how spatial overlap, and ultimately species interactions and competition, may change under a warming climate.