Geographical range,heat tolerance and invasion success in aquatic species

Species with broader geographical ranges are expected to be ecological generalists, while species with higher heat tolerances may be relatively competitive at more extreme and increasing temperatures. Thus, both traits are expected to relate to increased survival during transport to new regions of the globe, and once there, establishment and spread. Here, we explore these expectations using datasets of latitudinal range breadth and heat tolerance in freshwater and marine invertebrates and fishes. After accounting for the latitude and hemisphere of each species’ native range, we find that species introduced to freshwater systems have broader geographical ranges in comparison to native species. Moreover, introduced species are more heat tolerant than related native species collected from the same habitats. We further test for differences in range breadth and heat tolerance in relation to invasion success by comparing species that have established geographically restricted versus extensive introduced distributions. We find that geographical range size is positively related to invasion success in freshwater species only. However, heat tolerance is implicated as a trait correlated to widespread occurrence of introduced populations in both freshwater and marine systems. Our results emphasize the importance of formal risk assessments before moving heat tolerant species to novel locations.     

Compositional changes over space and time along an occurrence–abundance continuum: anthropogenic homogenization of the North American avifauna

Aim Changes in community attributes due to the influence of anthropogenic activities have been examined primarily using occurrence data with little consideration of associated changes in abundance. To determine how this influences our perception of biotic homogenization, we examined compositional patterns for avian assemblages over space and time along an occurrence–abundance continuum. Location The contiguous United States and southern Canada. Methods We examined avian assemblages at 951 Breeding Bird Survey (BBS) routes from 1970 to 2005 that contained a total of 443 species. We used five dissimilarity indices to estimate compositional patterns along an occurrence–abundance continuum of assemblage structure (from species occurrence to transformed abundance to raw abundance) for 396,925 unique combinations of BBS route pairs. We examined annual plots of dissimilarity by distance between BBS routes pairs to estimate spatial and temporal patterns for each index. Results Dissimilarity declined with increasing distance between route pairs for occurrence and transformed abundance, reaching an asymptote at approximately 2500 km. For raw abundance, dissimilarity peaked at intermediate distances (1000–2500 km) with no evidence of an asymptote. Avian assemblages became more similar over time at all points along the continuum. Occurrence and transformed abundance presented the weakest temporal trends, which were uniform or poorly delineated as a function of distance between routes. Raw abundance presented the strongest temporal trends, which declined in strength with increasing distance between routes. Main conclusions With the addition of abundance, there was a substantial and consistent pattern of degradation of β‐diversity for North American avifauna that differed considerably from that observed from occurrence data alone. The geographical expansion of a few species, which recently benefited from the direct and indirect consequences of anthropogenic activities, probably played a prominent role in these patterns. When broad‐scale expansions in occupancy are evident, minor gains in similarity based on species occurrence can mask more substantial gains in similarity based on local abundance. When abundance information is unavailable, its role can be estimated by how occupancy has responded geographically to anthropogenic activities and the expectations of the abundance–occupancy relationship. Our findings support previous work indicating that widespread and locally abundant species will tend to benefit more from anthropogenic activities, creating a possible synergism that enhances biotic homogenization.     

Phylogenetic beta diversity of native and alien species in European urban floras

Aim Human activities have weakened biogeographical barriers to dispersal, increasing the rate of introduction of alien plants. However, their impact on beta diversity and floristic homogenization is poorly understood. Our goal is to compare the phylogenetic beta diversity of native species with that of two groups of alien species, archaeophytes and neophytes (introduced before and after ad 1500, respectively), across European urban floras to explore how biological invasions affect phylogenetic turnover at a continental scale. Location Twenty European cities located in six countries between 49 and 53° N latitude in continental Europe and the British Isles. Methods To compare the phylogenetic beta diversity of native and alien species we use the average phylogenetic dissimilarity of individual floras from their group centroid in multivariate space. Differences in phylogenetic beta diversity among different species groups are then assessed using a randomization test for homogeneity of multivariate dispersions. Results Across European urban floras, and when contrasted with natives, archaeophytes are usually associated with lower levels of phylogenetic beta diversity while neophytes tend to increase phylogenetic differentiation. Main conclusions While archaeophytes tend to promote limited homogenization in phylogenetic beta diversity, because of their diverse geographical origin together with short residence times in the invaded regions, neophytes are not promoting biotic homogenization of urban floras across Europe. Therefore, in spite of the increasing rate of alien invasion, an intense phylogenetic homogenization of urban cities is not to be expected soon.     

Patterns of variation in levels of hsp70 in natural rocky shore populations from microscales to mesoscales

An important step in connecting the organismal response to thermalstress to patterns of community structure is determining atwhat scale discernable levels of variation are manifested. Thetemperature signal to which organisms may potentially respondvaries at many spatial scales including microhabitat, tidalheight, site and latitude. A number of studies have taken physiologicalassessment of the heat shock response (HSR) into the intertidalboth as a tool for examining the HSR in nature and for examiningthe utility of HSR molecules as population or community levelindicators. Most commonly, immunodetection of the total poolof the Hsp70 family of isoforms is used. Here we present dataon levels of Hsp70 in intertidal organisms from microhabitatto the mesoscale. Our data and previously published work showthat Hsp70 levels vary at all scales examined, similar to otherphysical and biological variables of interest. This demonstratesboth the potential utility of Hsp70 detection as a moleculartool for field biologists and to the care that must be takenin assessing scale of variation when looking for potential bioindicatormolecules.     

Seasonal associations with urban light pollution for nocturnally migrating bird populations

The spatial extent and intensity of artificial light at night (ALAN) has increased worldwide through the growth of urban environments. There is evidence that nocturnally migrating birds are attracted to ALAN, and there is evidence that nocturnally migrating bird populations are more likely to occur in urban areas during migration, especially in the autumn. Here, we test if urban sources of ALAN are responsible, at least in part, for these observed urban associations. We use weekly estimates of diurnal occurrence and relative abundance for 40 nocturnally migrating bird species that breed in forested environments in North America to assess how associations with distance to urban areas and ALAN are defined across the annual cycle. Migratory bird populations presented stronger than expected associations with shorter distances to urban areas during migration, and stronger than expected association with higher levels of ALAN outside and especially within urban areas during migration. These patterns were more pronounced during autumn migration, especially within urban areas. Outside of the two migration periods, migratory bird populations presented stronger than expected associations with longer distances to urban areas, especially during the nonbreeding season, and weaker than expected associations with the highest levels of ALAN outside and especially within urban areas. These findings suggest that ALAN is associated with higher levels of diurnal abundance along the boundaries and within the interior of urban areas during migration, especially in the autumn when juveniles are undertaking their first migration journey. These findings support the conclusion that urban sources of ALAN can broadly effect migratory behavior, emphasizing the need to better understand the implications of ALAN for migratory bird populations.     

Global change and the distributional dynamics of migratory bird populations wintering in Central America

Understanding the susceptibility of highly mobile taxa such as migratory birds to global change requires information on geographic patterns of occurrence across the annual cycle. Neotropical migrants that breed in North America and winter in Central America occur in high concentrations on their non‐breeding grounds where they spend the majority of the year and where habitat loss has been associated with population declines. Here, we use eBird data to model weekly patterns of abundance and occurrence for 21 forest passerine species that winter in Central America. We estimate species’ distributional dynamics across the annual cycle, which we use to determine how species are currently associated with public protected areas and projected changes in climate and land‐use. The effects of global change on the non‐breeding grounds is characterized by decreasing precipitation, especially during the summer, and the conversion of forest to cropland, grassland, or peri‐urban. The effects of global change on the breeding grounds are characterized by increasing winter precipitation, higher temperatures, and the conversion of forest to peri‐urban. During spring and autumn migration, species are projected to encounter higher temperatures, forests that have been converted to peri‐urban, and increased precipitation during spring migration. Based on current distributional dynamics, susceptibility to global change is characterized by the loss of forested habitats on the non‐breeding grounds, warming temperatures during migration and on the breeding grounds, and declining summer rainfall on the non‐breeding grounds. Public protected areas with low and medium protection status are more prevalent on the non‐breeding grounds, suggesting that management opportunities currently exist to mitigate near‐term non‐breeding habitat losses. These efforts would affect more individuals of more species during a longer period of the annual cycle, which may create additional opportunities for species to respond to changes in habitat or phenology that are likely to develop under climate change.     

Going with the flow: the role of ocean circulation in global marine ecosystems under a changing climate

Ocean warming, acidification, deoxygenation and reduced productivity are widely considered to be the major stressors to ocean ecosystems induced by emissions of CO₂. However, an overlooked stressor is the change in ocean circulation in response to climate change. Strong changes in the intensity and position of the western boundary currents have already been observed, and the consequences of such changes for ecosystems are beginning to emerge. In this study, we address climatically induced changes in ocean circulation on a global scale but relevant to propagule dispersal for species inhabiting global shelf ecosystems, using a high‐resolution global ocean model run under the IPCC RCP 8.5 scenario. The ¼ degree model resolution allows improved regional realism of the ocean circulation beyond that of available CMIP5‐class models. We use a Lagrangian approach forced by modelled ocean circulation to simulate the circulation pathways that disperse planktonic life stages. Based on trajectory backtracking, we identify present‐day coastal retention, dominant flow and dispersal range for coastal regions at the global scale. Projecting into the future, we identify areas of the strongest projected circulation change and present regional examples with the most significant modifications in their dominant pathways. Climatically induced changes in ocean circulation should be considered as an additional stressor of marine ecosystems in a similar way to ocean warming or acidification.     

Navigating north: how body mass and winds shape avian flight behaviours across a North American migratory flyway

The migratory patterns of birds have been the focus of ecologists for millennia. What behavioural traits underlie these remarkably consistent movements? Addressing this question is central to advancing our understanding of migratory flight strategies and requires the integration of information across levels of biological organisation, e.g. species to communities. Here, we combine species‐specific observations from the eBird citizen‐science database with observations aggregated from weather surveillance radars during spring migration in central North America. Our results confirm a core prediction of migration theory at an unprecedented national scale: body mass predicts variation in flight strategies across latitudes, with larger‐bodied species flying faster and compensating more for wind drift. We also find evidence that migrants travelling northward earlier in the spring increasingly compensate for wind drift at higher latitudes. This integration of information across biological scales provides new insight into patterns and determinants of broad‐scale flight strategies of migratory birds.     

Field response of rice paddy crop to Azospirillum inoculation: physiology of rhizosphere bacterial communities and the genetic diversity of endophytic bacteria in different parts of the plants

The response of rice plants to the application of inoculant containing two Azospirillum brasilense strains was studied under field conditions. The experiment was performed as three treatments with four replicates in randomized complete blocks arranged as plots of 60 m² in an area on a Vertic Argiudol soil type in the province of Entre Ríos, Argentina. The bacterial rhizosphere community and also the diazotrophic isolates obtained from control and inoculated rice plants were analyzed in relation to their physiology and biological nitrogen fixation (BNF). The MPN of diazotrophs in the rhizosphere varied during the ontogenic cycle. The patterns of distribution of the microbial physiological activities obtained by principal component analysis of community-level physiological profiles (CLPP) showed differences in the utilization of carbon sources by the rhizosphere communities among treatments. Although the analyses of DGGE 16S and nifH profiles have not indicated that the inoculation influenced the genetic diversity of bacterial communities among treatments, they revealed that the banding profiles were altered in different parts of the rice plant by each Azospirillum inoculation treatment. These observations suggest that physiological responses of plant tissues to the inoculation may have occurred. According to agronomic parameters of each treatment, the Azospirillum inoculation increased aerial biomass at the tillering and grain-filling stages. Although the N content accumulated in rice plants increased by 16 and 50 kg ha^?1, the BNF contribution could not be estimated under our experimental conditions by the ¹⁵N balance technique. Based on this field inoculation experiment to rice plants, it is noteworthy that our data suggest that due to Azospirillum inoculation the increase of total N accumulated in rice plants could be a tool to help farmers to improve production and maintain high input of plant residues, providing more organic matter to the soil and guaranteeing sustainability of the system.