Priority effects among young‐of‐the‐year fish: reduced growth of bluegill sunfish (Lepomis macrochirus) caused by yellow perch (Perca flavescens)?

1. When available, Daphnia spp. are often preferred by age‐0 yellow perch and bluegill sunfish because of energetic profitability. We hypothesised that predation by age‐0 yellow perch could lead to a midsummer decline (MSD) of Daphnia spp. and that priority effects may favour yellow perch because they hatch before bluegill, allowing them to capitalise on Daphnia spp. prior to bluegill emergence. 2. Data were collected from 2004 to 2010 in Pelican Lake, Nebraska, U.S.A. The lake experienced a prolonged MSD in all but 1 year (2005), generally occurring within the first 2 weeks of June except in 2008 and 2010 when it occurred at the end of June. MSD timing is not solely related to seasonal patterns of age‐0 yellow perch consumption. Nevertheless, when Daphnia spp. biomass was low during 2004 and 2006–2010 (<4 mg wet weight L^?1), predation by age‐0 yellow perch seems to have suppressed Daphnia spp. biomass (i.e. <1.0 mg wet weight L^?1). The exception was 2005 when age‐0 yellow perch were absent. 3. Growth of age‐0 bluegill was significantly faster in 2005, when Daphnia spp. were available in greater densities (>4 mg wet weight L^?1) compared with the other years (<0.2 mg wet weight L^?1). 4. We conclude that age‐0 yellow perch are capable of reducing Daphnia biomass prior to the arrival of age‐0 bluegill, ultimately slowing bluegill growth. Thus, priority effects favour age‐0 yellow perch when competing with age‐0 bluegill for Daphnia. However, these effects may be minimised if there is a shorter time between hatching of the two species, higher Daphnia spp. densities or lower age‐0 yellow perch densities.     

Track analysis of the Mexican species of Buprestidae (Coleoptera): testing the complex nature of the Mexican Transition Zone

Aim  We analysed the geographical distributions of species of Buprestidae (Coleoptera) in Mexico by means of a panbiogeographical analysis, in order to identify their main distributional patterns and test the complex nature of the Mexican Transition Zone, located between the Nearctic and Neotropical regions.
Location  Mexico.
Methods  The geographical distributions of 228 species belonging to 33 genera of Buprestidae were analysed. Localities of the buprestid species were represented on maps and their individual tracks were drawn. Based on a comparison of the individual tracks, generalized tracks were detected and mapped. Nodes were identified as the areas where generalized tracks converged.
Results  Thirteen generalized tracks were obtained: one was restricted to the Mexican Transition Zone and five to the Neotropical region (Antillean and Mesoamerican dominions), a further two occurred in both the Nearctic region (Continental Nearctic dominion) and the Mexican Transition Zone, and a further five in both the Neotropical region (Mesoamerican dominion) and the Mexican Transition Zone. Seven nodes were identified at the intersections of the generalized tracks – in the Mesoamerican dominion (Mexican Pacific Coast, Mexican Gulf and Chiapas biogeographical provinces) and the Mexican Transition Zone (Trans-Mexican Volcanic Belt, Balsas Basin and Sierra Madre Oriental biogeographical provinces).
Main conclusions  We conclude that the geographical distribution of Buprestidae is mainly Neotropical, corresponding to the Mesoamerican dominion and the Antillean dominion of the Neotropical region, and the Mexican Transition Zone. Most of the generalized tracks and nodes correspond to the Mexican Transition Zone, thus confirming its complex nature. We suggest that the nodes we have identified could be particularly important areas to choose for conservation prioritization.     

Integrating the spatial proximity effect into the assessment of changes in ecosystem services for biodiversity conservation

The assessment of the value of ecosystem services is a valuable tool for biodiversity conservation that can facilitate better environmental policy decision-making and land management, and can help land managers develop interventions to compensate for biodiversity loss at the patch level. Previous studies have suggested that it is appropriate to assess the value of biodiversity for conservation planning by considering both the condition of the landscape and the spatial configuration of adjacent land uses that can be reflected as a proximity effect. This research examines the influence of spatial proximity on biodiversity conservation from the ecosystem service perspective based on the assumption that the variation in the proximity effect caused by land cover change has positive or negative impacts on ecological services. Three factors related to the spatial characteristics of the landscape were considered in this approach: the relative artificiality of the land cover types, the distance decay effect of patches and the impact of one land cover type on others. The proximity effect change (PE_C) parameter reflected the relationship between the spatial proximity effect and biodiversity conservation. The results of a quantitative and spatial comparative analysis of the proposed method and the conventional method in Yingkou for the periods of 2000–2005 and 2005–2010 showed that the former can account for the temporal and spatial changes in ecosystem services for biodiversity conservation that were caused by patch-level changes as well as the interaction between the altered and adjacent patches from a spatial perspective. The metric can also identify the most critical areas for biodiversity protection and inform the efficient allocation of limited land resources for nature conservation to maximize the benefit to biodiversity by guiding the process of land-use change, particularly urbanization and agriculture. Future studies should focus on the other important factors that are applicable to the assessment of the value of biodiversity conservation in socio-ecological systems, where society and nature are mutually capable of fulfilling their roles.     

Rediscovery of Nebela ansata (Amoebozoa: Arcellinida) in eastern North America: biogeographical implications

Aim The question whether free‐living protists are generally cosmopolitan is currently a matter of debate. In this study we investigate the geographical distribution of a distinctive testate amoeba species, Nebela ansata, and use our data to assess the potential for highly restricted distribution patterns in some protist species. Location Global. Methods We analysed (1) 3400 testate amoeba publications from North America and other continents, (2) unpublished slides of the Penard Collection of the Natural History Museum, London, UK, and (3) 104 Sphagnum samples from eastern North America. Non‐metric multidimensional scaling (NMDS) was used to visualize the similarities in testate amoeba community composition among 1012 North American samples, including two communities that contained N. ansata. Results We rediscovered N. ansata at a site in New Jersey located close to its type locality, and in Nova Scotia. We also report the existence of an apparently unpublished museum specimen originally collected from New Jersey. Our extensive literature survey confirmed the presence of this species only in the temperate part of eastern North America. The NMDS revealed that communities with N. ansata were less similar to each other than to communities from other parts of North America, suggesting that favourable habitats for N. ansata occur in other Sphagnum‐dominated peatlands, a habitat type that has been extensively sampled in North America and elsewhere. Main conclusions These data provide an unusually convincing case of a free‐living microorganism with a very limited distribution range in the temperate part of eastern North America. The remarkably restricted distribution of N. ansata highlights the extent of our ignorance about the natural history of free‐living microorganisms, and raises questions about the lack of attention to microbial diversity in conservation biology.     

Are there Atlantic salmon in the River Tambre?

Genetic variability and assignment analyses demonstrate that the 60 returning adult salmon to the Tambre River in 2005 were not the product of an incipient wild population, but the result of straying from a neighbouring river.     

CHROMOSOMAL REPATTERNING AND LINKAGE GROUP CONSERVATION IN MOSQUITO KARYOTYPIC EVOLUTION

Chromosome number and morphology in mosquitoes is remarkably uniform: virtually all mosquitoes have a diploid chromosome number of six (2N = 6), and their chromosomes are invariably metacentric or submetacentric. Numerical changes obviously have not been important in mosquito chromosomal evolution, and because of the morphological similarity of their chromosomes, it appears that structural changes have played little or no role in mosquito karyotypic evolution. The goal of the present study was to identify the types and relative numbers of chromosomal changes in mosquito evolution and to extend the comparison where possible to the higher diptera. To do this, we compared the enzyme linkage maps of six species of Aedes to each other and to enzyme maps of seven other mosquito species and to Drosophila melanogaster. Our results indicate that Aedes chromosomes have been modified by inversions, most which were paracentric, and by translocations, most which were Robertsonian. Intrageneric comparison of Aedes enzyme maps also revealed groups of linked enzyme loci whose integrity has been maintained throughout Aedes evolution (conserved linkages/syntenies). Intergeneric comparisons of Aedes enzyme maps with those of species in the genera Culex, Anopheles, and Toxorhynchites disclosed conserved associations of enzyme loci between mosquito genera. These findings lead us to postulate that the ancestral mosquito karyotype consisted of six chromosomal elements which, other than being combined in different ways in various mosquito groups, have remained essentially intact during mosquito evolution. Furthermore, the identification of groups of linked enzyme loci common to mosquitoes and to D. melanogaster indicates that linkage group conservation may characterize the karyotypic evolution of all dipteran insects.     

Imprints of glacial history and current environment on correlations between endemic plant and invertebrate species richness

Aim We evaluate how closely diversity patterns of endemic species of vascular plants, beetles, butterflies, molluscs and spiders are correlated with each other, and to what extent similar environmental requirements or survival in common glacial refugia and comparable dispersal limitations account for their existing congruence. Location Austria. Methods We calculated pairwise correlations among species numbers of the five taxonomic groups in 1405 cells of a 3′ × 5′ raster (c. 35 km²) using the raw data as well as the residuals of regression models that accounted for: (1) environmental variables, (2) environmental variables and the occurrence of potential refugia during the Last Glacial Maximum, or (3) environmental variables, refugia and spatial filters. Results Pairwise cross‐taxonomic group Spearman’s rank correlations in the raw data were significantly positive in most cases, but only moderate (0.3 < ρ < 0.5) to weak (ρ < 0.3) throughout. Correlations were closest between plants and beetles, plants and butterflies, and plants and snails, respectively, whereas the distribution of endemic spiders was largely uncorrelated with those of the other groups. Environmental variables explained only a moderate proportion of the variance in endemic richness patterns, and the response of individual groups to environmental gradients was only partly consistent. The inclusion of refugium locations and the spatial filters increased the goodness of model fit for all five taxonomic groups. Moreover, removing the effects of environmental conditions reduced congruence in endemic richness patterns to a lesser extent than did filtering the influence of refugium locations and spatial autocorrelation, except for spiders, which are probably the least dispersal‐limited of the five groups. Main conclusions The moderate to weak congruence of endemic richness patterns clearly limits the usefulness of a surrogacy approach for designating areas for the protection of regional endemics. On the other hand, our results suggest that dispersal limitations still shape the distributions of many endemic plant, snail, beetle and butterfly species, even at the regional scale; that is, survival in shared refugia and subsequent restricted spread retain a detectable signal in existing correlations. Concentrating conservation efforts on well‐known Pleistocene refugia hence appears to be a reasonable first step towards a strategy for protecting regional endemics of at least the less mobile invertebrate groups.