Mixed‐source reintroductions lead to outbreeding depression in second‐generation descendents of a native North American fish

Reintroductions are commonly employed to preserve intraspecific biodiversity in fragmented landscapes. However, reintroduced populations are frequently smaller and more geographically isolated than native populations. Mixing genetically, divergent sources are often proposed to attenuate potentially low genetic diversity in reintroduced populations that may result from small effective population sizes. However, a possible negative tradeoff for mixing sources is outbreeding depression in hybrid offspring. We examined the consequences of mixed‐source reintroductions on several fitness surrogates at nine slimy sculpin (Cottus cognatus) reintroduction sites in south‐east Minnesota. We inferred the relative fitness of each crosstype in the reintroduced populations by comparing their growth rate, length, weight, body condition and persistence in reintroduced populations. Pure strain descendents from a single source population persisted in a greater proportion than expected in the reintroduced populations, whereas all other crosstypes occurred in a lesser proportion. Length, weight and growth rate were lower for second‐generation intra‐population hybrid descendents than for pure strain and first‐generation hybrids. In the predominant pure strain, young‐of the‐year size was significantly greater than any other crosstype. Our results suggested that differences in fitness surrogates among crosstypes were consistent with disrupted co‐adapted gene complexes associated with beneficial adaptations in these reintroduced populations. Future reintroductions may be improved by evaluating the potential for local adaptation in source populations or by avoiding the use of mixed sources by default when information on local adaptations or other genetic characteristics is lacking.     

How river structure and biological traits influence gene flow: a population genetic study of two stream invertebrates with differing dispersal abilities

1. Determined by landscape structure as well as dispersal‐related traits of species, connectivity influences various key aspects of population biology, ranging from population persistence to genetic structure and diversity. Here, we investigated differences in small‐scale connectivity in terms of gene flow between populations of two ecologically important invertebrates with contrasting dispersal‐related traits: an amphipod (Gammarus fossarum) with a purely aquatic life cycle and a mayfly (Baetis rhodani) with a terrestrial adult stage. 2. We used highly polymorphic markers to estimate genetic differentiation between populations of both species within a Swiss pre‐alpine catchment and compared these results to the broader‐scale genetic structure within the Rhine drainage. Landscape genetic approaches were used to test for correlations of genetic and geographical structures and in‐stream barrier effects. 3. We found overall very weak genetic structure in populations of B. rhodani. In contrast, G. fossarum showed strong genetic differentiation, even at spatial scales of a few kilometres, and a clear pattern of isolation by distance. Genetic diversity decreased from downstream towards upstream populations of G. fossarum, suggesting asymmetric gene flow. Correlation of genetic structure with landscape topography was more pronounced in the amphipod. Our study also indicates that G. fossarum might be capable of dispersing overland in headwater regions and of crossing small in‐stream barriers. 4. We speculate that differences in dispersal capacity but also habitat specialisation and potentially the extent of local adaptation could be responsible for the differences in genetic differentiation found between the two species. These results highlight the importance of taking into account dispersal‐related traits when planning management and conservation strategies.     

Abundance and distribution within a guild of benthic stream fishes: local processes and regional patterns

1. Spatial patterns at regional and local scales were examined for evidence that species interactions can influence distribution and abundance within a guild of benthic fishes in upland streams of Oklahoma, U.S.A. Three groups of community patterns were examined: the species–area relationship, species–habitat associations, and interspecific associations.
2. The species–area relationship for riffle habitats was compared to a null species–area model based on random placement. The observed species–area curve was steeper resulting in less species per unit area in small streams than predicted by the null model.
3. Small, species-poor streams had summed fish densities at least as high as larger, species-rich streams, suggesting density compensation.
4. Several significant patterns of negative covariation were found among species at the regional scale, before and after statistically accounting for effects due to measured habitat variables.
5. For two of these negatively covarying taxa ( Cottus carolinae and Etheostoma spectabile ), the influence of each species on the distribution of the other was evaluated experimentally in field enclosures varying in depth and current velocity. The sculpin C . carolinae caused a shift in habitat use by the darter E . spectabile , but no reciprocal shift was found.
6. These results indicate an agreement between local and regional patterns of distribution for C . carolinae and E . spectabile and suggest that biotic interactions can influence regional patterns of distribution for species within this guild.     

The development of an Early Ordovician hard ground community in response to rapid sea-floor calcite precipitation

The Kanosh Shale (Upper Arenig, Lower Ordovician) of west-central Utah. USA. contains abundant carbonate hardgrounds and one of the earliest diverse hardground communities. The hardgrounds were formed through a combination of processes including the development of early digenetic nodules in clay sediments which were exhumed and concentrated as lags by storms. These cobble deposits. together with plentiful biogenic metrical. were cemented by inorganically precipitated calcite on the sea floor. forming intraformational conglomerate hardgrounds. Echinoderms may have -played a critical role in the development of hardground faunas since their disarticulated calcite ossicles were rapidly cemented by syntaxial overgrowths. forming additional cobbles and hardgrounds. The echinoderms thus may have taphonomically facilitated the development of some of the hard substrates they required. A significant portion of the hardground cements may have been derived from the early dissolution of aragonitic mollusk shells. Kanosh hardground species include the earliest bryozoans recorded on hardgrounds and large numbers of stemmed echinoderms. primarily rhipidocystid cocrinoids. Bryozoans and echinoderms covered nearly equal areas of the hardground surfaces. and there was a distinct polarization between species which preferred the upper. exposed portions of the hardgrounds and others which were most common on undercut. overhang surfaces. The Kanosh Shale hardground fossils combine elements of Late Cambrian assemblages and Middle Ordovician faunas, thus confirming predicted trends in hardground community evolution. especially the replacement of cocrinoids by bryozoans and. to a lesser extent, by other stemmed echinoderms, especially crinoids. The Kanosh community marks the transition from the Cambrian Fauna to The Paleozoic Fauna in The hardground ecosystem. *Carbonate hardgrounds, aragonite dissolution, calcite cement, Echinodermara, Trepostomata, Nicholsonclla. Dianulites. Porifpra. taphonomic facilitation, Utah. Pogonip Group, Kanosh Shale. Ordovician.     

Global assessment of coral bleaching and required rates of adaptation under climate change

Elevated ocean temperatures can cause coral bleaching, the loss of colour from reef‐building corals because of a breakdown of the symbiosis with the dinoflagellate Symbiodinium. Recent studies have warned that global climate change could increase the frequency of coral bleaching and threaten the long‐term viability of coral reefs. These assertions are based on projecting the coarse output from atmosphere–ocean general circulation models (GCMs) to the local conditions around representative coral reefs. Here, we conduct the first comprehensive global assessment of coral bleaching under climate change by adapting the NOAA Coral Reef Watch bleaching prediction method to the output of a low‐ and high‐climate sensitivity GCM. First, we develop and test algorithms for predicting mass coral bleaching with GCM‐resolution sea surface temperatures for thousands of coral reefs, using a global coral reef map and 1985–2002 bleaching prediction data. We then use the algorithms to determine the frequency of coral bleaching and required thermal adaptation by corals and their endosymbionts under two different emissions scenarios. The results indicate that bleaching could become an annual or biannual event for the vast majority of the world's coral reefs in the next 30–50 years without an increase in thermal tolerance of 0.2–1.0°C per decade. The geographic variability in required thermal adaptation found in each model and emissions scenario suggests that coral reefs in some regions, like Micronesia and western Polynesia, may be particularly vulnerable to climate change. Advances in modelling and monitoring will refine the forecast for individual reefs, but this assessment concludes that the global prognosis is unlikely to change without an accelerated effort to stabilize atmospheric greenhouse gas concentrations.     

Sixteen new simple sequence repeat markers from Brassica juncea expressed sequences and their cross‐species amplification

The availability of expressed sequence data derived from gene discovery programs enables mining for simple sequence repeats (SSR), providing useful genetic markers for crop improvement. These markers are inexpensive, require minimal labour to produce and can frequently be associated with functionally annotated genes. This study presents the development and characterization of 16 expressed sequence tags (EST)‐SSR markers from Brassica juncea and their cross‐amplification across Brassica species. Sixteen primer pairs were assessed for polymorphism in all genomes of the diploid and amphidiploid Brassica species. The markers show reliable amplification, considerable polymorphism and high transferability across species, demonstrating the utility of EST‐SSRs for genetic analysis of brassicas.     

Dispersal of Yearling Pronghorns in Western South Dakota

Abstract: We captured and radiocollared 57 pronghorn (Antilocapra americana) fawns in western South Dakota, USA, during May 2002–2003 and radiotracked them through 15 months of age, by which time all surviving individuals had established a permanent home range. We classified 56% (n = 19) of fawns as dispersers and 44% (n = 15) as residents. Eighty-four percent (n = 16) of dispersers departed natal home ranges in late October and occupied winter home ranges for 102–209 days before dispersing to permanent home ranges during April 2003 and 2004. Dispersal distances from natal ranges to permanent home ranges varied from 6.2–267.0 km. Winter home-range sizes for all individual pronghorns varied from 39.4–509.6 km. Permanent home-range size for all individuals varied from 15.5–166.1 km². Mean 95% permanent home-range size differed (P = 0.06) between residents (x̄ = 97.3 ± 15.1 km²) and dispersers (x̄ = 48.6 ± 16.0 km²), but was similar (P = 0.97) among sexes. Mean dispersal distance from natal to permanent home ranges was similar (P = 0.35) for males (x̄ = 54.2 ± 21.0 km) and females (x̄ = 26.3 ± 19.9 km). We suggest that habitat quality (i.e., patchiness) and pronghorn density, in part, stimulated dispersal. We hypothesize that as habitat patch size decreases, home range sizes and distance traveled during predispersal and dispersal movements by pronghorns will increase.