Condition and brightness of structural blue‐green: motmot tail‐racket brightness is related to speed of feather growth in males,but not in females

Coloration plays an important role in sexual and social communication, and in many avian species both males and females maintain elaborate colours. Recent research has provided strong support for the hypothesis that elaborate female traits can be maintained by sexual or social selection; however, most research on female ornamentation has focused on pigment‐based colours, and less is known about how structural colours are maintained. Both sexes of the turquoise‐browed motmot (Eumomota superciliosa) have a blue‐green racket‐tipped tail, and it remains unknown if tail coloration serves as a sexual or social signal in one or both sexes. Here, we describe sexual dichromatism in the blue‐green portion of the tail racket, and we test for a relationship between coloration and condition, as indicated by growth bars. Tail colour of both sexes has a similar spectral shape, and there is significant, although moderate, sexual dichromatism: males are brighter than females, and males have marginally greater blue‐green saturation than females. The length of feather grown per day is positively related to overall feather brightness, but this relationship is only present in males. The relationship between male coloration and condition suggests that tail colour has the potential to convey information about individual quality during mate choice or contest competition. The lack of a similar relationship in females suggests that female tail colour does not convey the same condition‐dependent information that we suggest may be reflected by male colour. Female tail colour may therefore reflect other aspects of condition, be involved in other (non‐condition‐dependent) forms of communication, or be expressed as a non‐functional byproduct of genetic correlation between the sexes. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 673–681.     

Advances in endophenotyping schizophrenia

The search for the genetic architecture of schizophrenia has employed multiple, often converging strategies. One such strategy entails the use of tracing the heritability and neurobiology of endophenotypes. Endophenotypes are quantifiable traits not visible to the eye, which are thought to reflect an intermediate place on the path from genes to disorder. Endophenotype abnormalities in domains such as neurophysiology or neurocognition occur in schizophrenia patients as well as their clinically “unaffected” relatives, and reflect polymorphisms in the DNA of schizophrenia spectrum subjects which create vulnerability to developing schizophrenia. By identifying the single nucleotide polymorphisms (SNPs) associated with endophenotypes in schizophrenia, psychiatric neuroscientists can select new strong inference based molecular targets for the treatment of schizophrenia.     

Postfire carbon balance in boreal bogs of Alberta, Canada

Boreal peatland ecosystems occupy about 3.5 million km² of the earth's land surface and store between 250 and 455 Pg of carbon (C) as peat. While northern hemisphere boreal peatlands have functioned as net sinks for atmospheric C since the most recent deglaciation, natural and anthropogenic disturbances, and most importantly wildfire, may compromise peatland C sinks. To examine the effects of fire on local and regional C sink strength, we focused on a 12 000 km² region near Wabasca, AB, Canada, where ombrotrophic Sphagnum‐dominated bogs cover 2280 km² that burn with a fire return interval of 123±26 years. We characterized annual C accumulation along a chronosequence of 10 bog sites, spanning 1–102 years‐since‐fire (in 2002). Immediately after fire, bogs represent a net C source of 8.9±8.4 mol m⁻² yr⁻¹. At about 13 years after fire, bogs switch from net C sources to net C sinks, mainly because of recovery of the moss and shrub layers. Subsequently, black spruce biomass accumulation contributes to the net C sink, with fine root biomass accumulation peaking at 34 years after fire and aboveground biomass and coarse root accumulation peaking at 74 years after fire. The overall C sink strength peaks at 18.4 mol C m⁻² yr⁻¹ at 75 years after fire. As the tree biomass accumulation rate declines, the net C sink decreases to about 10 mol C m⁻² yr⁻¹ at 100 years‐since‐fire. We estimate that across the Wabasca study region, bogs currently represent a C sink of 14.7±5.1 Gmol yr⁻¹. A decrease in the fire return interval to 61 years with no change in air temperature would convert the region's bogs to a net C source. An increase in nonwinter air temperature of 2 °C would decrease the regional C sink to 6.8±2.3 Gmol yr⁻¹. Under scenarios of predicted climate change, the current C sink status of Alberta bogs is likely to diminish to the point where these peatlands become net sources of atmospheric CO₂‐C.     

Admixture mapping of male nuptial colour and body shape in a recently formed hybrid population of threespine stickleback

Despite recent progress, we still know relatively little about the genetic architecture that underlies adaptation to divergent environments. Determining whether the genetic architecture of phenotypic adaptation follows any predictable patterns requires data from a wide variety of species. However, in many organisms, genetic studies are hindered by the inability to perform genetic crosses in the laboratory or by long generation times. Admixture mapping is an approach that circumvents these issues by taking advantage of hybridization that occurs between populations or species in the wild. Here, we demonstrate the utility of admixture mapping in a naturally occurring hybrid population of threespine sticklebacks (Gasterosteus aculeatus) from Enos Lake, British Columbia. Until recently, this lake contained two species of sticklebacks adapted to divergent habitats within the lake. This benthic–limnetic species pair diverged in a number of phenotypes, including male nuptial coloration and body shape, which were previously shown to contribute to reproductive isolation between them. However, recent ecological disturbance has contributed to extensive hybridization between the species, and there is now a single, admixed population within Enos Lake. We collected over 500 males from Enos Lake and found that most had intermediate nuptial colour and body shape. By genotyping males with nuptial colour at the two extremes of the phenotypic distribution, we identified seven genomic regions on three chromosomes associated with divergence in male nuptial colour. These genomic regions are also associated with variation in body shape, suggesting that tight linkage and/or pleiotropy facilitated adaptation to divergent environments in benthic–limnetic species pairs.     

Comparison of Two Techniques for Surveying Headwater Stream Amphibians

Abstract: We compared rubble-rousing versus light-touch stream amphibian survey techniques in multiple 1-m plots across 10 streams in southwest Washington, USA. Specifically, we wanted to determine if light-touch surveys provide unbiased estimates of abundance (i.e., provide counts correlated with rubble-rousing counts) and which method would provide more cost-effective presence or absence information. Rubble-rousing, a common technique for surveying stream-associated amphibians in the Pacific Northwest, took 12 times as long as light-touch to apply. Abundance estimates and standard errors for rubble-rousing were consistently higher than those for light-touch for all life stages for the coastal tailed frog (Ascaphus truei) and Columbia torrent salamander (Rhyacotriton kezeri). Except for eggs, light-touch detected all life stages found during rubble-rousing. For frogs, only some rubble-rousing abundance estimates, mostly involving second-year larvae, were highly correlated with their light-touch counterparts, whereas for salamanders, similar comparisons generated high correlations across most life stages. Correlations between methods were consistently greater for salamanders than for frogs. However the smaller tailed frog sample sizes and the cryptozoic nature of some life stages may have contributed to this pattern. Depending on the degree to which researchers can tolerate false-negative error rates, light-touch may prove less costly than rubble-rousing for detecting species presence. For the cost of obtaining one rubble-rousing sample, many light-touch samples can be used across a range of habitats for detecting species patchily distributed.     

Invasion of the shelter snatchers: behavioural plasticity in invasive red swamp crayfish,Procambarus clarkii

1. In many freshwater systems, competition for shelter plays an important role in determining the persistence of both native and alien species. The red swamp crayfish, Procambarus clarkii, is currently invading the native habitat of the signal crayfish, Pacifastacus leniusculus, in southern Oregon, and interspecific competition for shelter may be driving the species replacement in this region. 2. We designed a 2 × 3 factorial mesocosm experiment, with shelter density and species combination as factors, to investigate shelter occupancy and resource competition. Contrary to our predictions, the two crayfish species are equal competitors for shelter. Further, the invasive P. clarkii modified its shelter occupancy behaviour in the presence of the native P. leniusculus and has broader microhabitat preferences. 3. Specifically, we found that P. clarkii alters shelter occupancy and space use patterns when the two species occurred together, such that shelter use was identical between P. clarkii and P. leniusculus in mixed‐species treatments. In such treatments, both species increased their use of shelters when shelter density increased. When P. clarkii was alone, however, individuals did not alter shelter use as a function of shelter density, whereas P. leniusculus exhibited similar density‐dependent behaviour in both mixed‐ and single‐species treatments. 4. In a complementary field survey, we employed an ‘epicentre‐based’ design to sample two field sites. We observed patterns of microhabitat use and breadth for each species similar to those in our mesocosm experiment: the invasive P. clarkii was more abundant across different habitats and used a broader range of microhabitats than the native P. leniusculus. As such, we found that P. clarkii was more abundant across both field sites than the P. leniusculus, occupying microhabitats within and beyond the preferred range of P. leniusculus. Both field sites were affected by urban development and agriculture. 5. The use of microhabitats by both species was similar in the laboratory and the field. This study confirms that P. clarkii individuals can, and do, successfully occupy microhabitats preferred by P. leniusculus in the Willamette Valley. The results from our study may be relevant to other freshwater systems inhabited by P. clarkii and contribute to the understanding of ‘niche opportunity’, a concept which defines the environmental conditions that promote biological invasions.