Climate-driven convergent evolution in riparian ecosystems on sky islands.

Climate-induced evolution will determine population persistence in a changing world. However, finding natural systems in which to study these responses has been a barrier to estimating the impact of global change on a broad scale. We propose that isolated sky islands (SI) and adjacent mountain chains (MC) are natural laboratories for studying long-term and contemporary climatic pressures on natural populations. We used greenhouse common garden trees to test whether populations on SI exposed to hot and dry climates since the end of the Pleistocene have phenotypically diverged from populations on MC, and if SI populations have converged in these traits. We show: (1) populations of Populus angustifolia from SI have diverged from MC, and converged across SI, in reproductive and productivity traits, (2) these traits (cloning and aboveground biomass, respectively) are significantly correlated, suggesting a genetic linkage between them, and (3) the trait variation is driven by both natural selection and genetic drift. These shifts represent potentially beneficial phenotypes for population persistence in a changing world. These results suggest that the SI-MC comparison is a natural laboratory, as well as a predictive framework, for studying long-term responses to climate change across the globe.

Treatment outcomes for keloid scar management in the pediatric burn population.

INTRODUCTION: Keloids scars are challenging problems facing many reconstructive surgeons and have proven to be resistant to many treatments. This is evident by the broad range of treatments available and implemented with inconsistent results. We reviewed our experience to better define the disorder and to evaluate the impact of specific treatment options as related to our patient population. METHODS: After obtaining Institutional Review Board approval, we examined the medical records of pediatric patients who were evaluated at our pediatric burn center between 2000 to 2008. All study subjects were identified as having keloid scars confirmed by clinical evaluation (raised scar extending beyond the margins of the original wound [1,2]). Treatments included excision and grafting [split thickness autograft (STAG) or full thickness autograft (FTAG)], excision and grafting with steroid injection, excision and primary closure, or excision and primary closure with steroid injection. Patients were included only if there was follow-up of 12 months or greater. RESULTS: One hundred and ten subjects with a diagnosis of a keloid scar were identified. Twenty-six were treated with excision and skin grafting and 8 were treated with a steroid and surgery regimen. Of the patients treated with surgery and steroids, the treatment varied from an intra-operative injection to post-operative injections at 6-week intervals. The number of injections was determined by the administering surgeon and varied from one to three. Clinical end points were determined by the administering surgeon and included: (1) no further improvement in scar maturation or (2) absence of improvement. Recurrence was defined as return of a raised scar consistent with a keloid scar. The recurrence rate was 87.5% for patients treated with surgery and steroids and 80.0% for surgery only. This difference was not statistically significant. CONCLUSIONS: Our data demonstrate that steroids do not significantly decrease recurrence in pediatric burn related keloids as compared to previously published series involving non-burn related keloids [3,5]. This further emphasizes that burn related keloids respond differently to conventional treatments that have proven successful in keloid scars from other mechanisms of injury. A consistent and effective treatment algorithm should be implemented in treating keloid scars from burn wounds.

A geographic mosaic of trophic interactions and selection: trees, aphids and birds.

Genetic variation in plants is known to influence arthropod assemblages and species interactions. However, these influences may be contingent upon local environmental conditions. Here, we examine how plant genotype-based trophic interactions and patterns of natural selection change across environments. Studying the cottonwood tree, Populus angustifolia, the galling aphid, Pemphigus betae and its avian predators, we used three common gardens across an environmental gradient to examine the effects of plant genotype on gall abundance, gall size, aphid fecundity and predation rate on galls. Three patterns emerged: (i) plant genotype explained variation in gall abundance and predation, (ii) G×E explained variation in aphid fecundity, and environment explained variation in gall abundance and gall size, (iii) natural selection on gall size changed from directional to stabilizing across environments.

Genetic structure of a foundation species: scaling community phenotypes from the individual to the region.

Understanding the local and regional patterns of species distributions has been a major goal of ecological and evolutionary research. The notion that these patterns can be understood through simple quantitative rules is attractive, but while numerous scaling laws exist (e.g., metabolic, fractals), we are aware of no studies that have placed individual traits and community structure together within a genetics based scaling framework. We document the potential for a genetic basis to the scaling of ecological communities, largely based upon our long-term studies of poplars (Populus spp.). The genetic structure and diversity of these foundation species affects riparian ecosystems and determines a much larger community of dependent organisms. Three examples illustrate these ideas. First, there is a strong genetic basis to phytochemistry and tree architecture (both above- and belowground), which can affect diverse organisms and ecosystem processes. Second, empirical studies in the wild show that the local patterns of genetics based community structure scale up to western North America. At multiple spatial scales the arthropod community phenotype is related to the genetic distance among plants that these arthropods depend upon for survival. Third, we suggest that the familiar species-area curve, in which species richness is a function of area, is also a function of genetic diversity. We find that arthropod species richness is closely correlated with the genetic marker diversity and trait variance suggesting a genetic component to these curves. Finally, we discuss how genetic variation can interact with environmental variation to affect community attributes across geographic scales along with conservation implications.

Community heritability measures the evolutionary consequences of indirect genetic effects on community structure.

The evolutionary analysis of community organization is considered a major frontier in biology. Nevertheless, current explanations for community structure exclude the effects of genes and selection at levels above the individual. Here, we demonstrate a genetic basis for community structure, arising from the fitness consequences of genetic interactions among species (i.e., interspecific indirect genetic effects or IIGEs). Using simulated and natural communities of arthropods inhabiting North American cottonwoods (Populus), we show that when species comprising ecological communities are summarized using a multivariate statistical method, nonmetric multidimensional scaling (NMDS), the resulting univariate scores can be analyzed using standard techniques for estimating the heritability of quantitative traits. Our estimates of the broad-sense heritability of arthropod communities on known genotypes of cottonwood trees in common gardens explained 56-63% of the total variation in community phenotype. To justify and help interpret our empirical approach, we modeled synthetic communities in which the number, intensity, and fitness consequences of the genetic interactions among species comprising the community were explicitly known. Results from the model suggest that our empirical estimates of broad-sense community heritability arise from heritable variation in a host tree trait and the fitness consequences of IGEs that extend from tree trait to arthropods. When arthropod traits are heritable, interspecific IGEs cause species interactions to change, and community evolution occurs. Our results have implications for establishing the genetic foundations of communities and ecosystems.

A genetic similarity rule determines arthropod community structure.

We define a genetic similarity rule that predicts how genetic variation in a dominant plant affects the structure of an arthropod community. This rule applies to hybridizing cottonwood species where plant genetic variation determines plant-animal interactions and structures a dependent community of leaf-modifying arthropods. Because the associated arthropod community is expected to respond to important plant traits, we also tested whether plant chemical composition is one potential intermediate link between plant genes and arthropod community composition. Two lines of evidence support our genetic similarity rule. First, in a common garden experiment we found that trees with similar genetic compositions had similar chemical compositions and similar arthropod compositions. Second, in a wild population, we found a similar relationship between genetic similarity in cottonwoods and the dependent arthropod community. Field data demonstrate that the relationship between genes and arthropods was also significant when the hybrids were analysed alone, i.e. the pattern is not dependent upon the inclusion of both parental species. Because plant-animal interactions and natural hybridization are common to diverse plant taxa, we suggest that a genetic similarity rule is potentially applicable, and may be extended, to other systems and ecological processes. For example, plants with similar genetic compositions may exhibit similar litter decomposition rates. A corollary to this genetic similarity rule predicts that in systems with low plant genetic variability, the environment will be a stronger factor structuring the dependent community. Our findings argue that the genetic composition of a dominant plant can structure higher order ecological processes, thus placing community and ecosystem ecology within a genetic and evolutionary framework. A genetic similarity rule also has important conservation implications because the loss of genetic diversity in one species, especially dominant or keystone species that define many communities, may cascade to negatively affect the rest of the dependent community.

Spinotrapezius muscle microcirculatory function: effects of surgical exteriorization.

Intravital microscopy facilitates insights into muscle microcirculatory structural and functional control, provided that surgical exteriorization does not impact vascular function. We utilized a novel combination of phosphorescence quenching, microvascular oxygen pressure (microvascular PO(2)), and microsphere (blood flow) techniques to evaluate static and dynamic behavior within the exposed intact (I) and exteriorized (EX) rat spinotrapezius muscle. I and EX muscles were studied under control, metabolic blockade with 2,4-dinitrophenol (DNP), and electrically stimulated conditions with 1-Hz contractions, and across switches from 21 to 100% and 10% inspired O(2). Surgical preparation did not alter spinotrapezius muscle blood flow in either I or EX muscle. DNP elevated muscle blood flow approximately 120% (P < 0.05) in both I and EX muscles (P > 0.05 between I and EX). Contractions reduced microvascular PO(2) from 30.4 +/- 4.3 to 21.8 +/- 4.8 mmHg in I muscle and from 33.2 +/- 3.0 to 25.9 +/- 2.8 mmHg in EX muscles with no difference between I and EX. In each O(2) condition, there was no difference (each P > 0.05) in microvascular PO(2) between I and EX muscles (21% O(2): I = 37 +/- 1; EX = 36 +/- 1; 100%: I = 62 +/- 5; EX = 51 +/- 9; 10%: I = 20 +/- 1; EX = 17 +/- 2 mmHg). Similarly, the dynamic behavior of microvascular PO(2) to altered inspired O(2) was unaffected by the EX procedure [half-time (t(1/2)) to 100% O(2): I = 23 +/- 5; EX = 23 +/- 4; t(1/2) to 10%: I = 14 +/- 2; EX = 16 +/- 2 s, both P > 0.05]. These results demonstrate that the spinotrapezius muscle can be EX without significant alteration of microvascular integrity and responsiveness under the conditions assessed.

Fibrin gel limits intra-abdominal adhesion formation.

Autologous fibrin gel (FG) has recently been reported efficacious in hepatic injury; the effects of fibrin compounds on intra-abdominal adhesion formation is controversial. This study evaluated intra-abdominal adhesion formation in a rabbit devascularization model. Seventeen New Zealand rabbits were anesthetized and laparotomy was done. The uterine horns were abraded to punctate bleeding followed by bilateral uterine devascularization. Treatment consisted of 10 cc saline control (c) or FG applied to the uterine horns. Peritoneal lavage was done at 15 minutes for red blood cell (RBC) analysis. Autopsy was performed at 1 week. Adhesions were graded from grade 0 (no adhesions) to grade III (dense adhesions). Adhesion grading revealed no difference in average adhesion grade between FG and C with small bowel (1.0 +/- 1.3 vs 0.5 +/- 1.0); bladder (2.1 +/- 1.1 vs 2.4 +/- 1.2); or uterus (1.2 +/- vs 2.0 +/- 1.2). Adhesion grade was significantly less in FG compared to C for the colon and the abdominal incision (0.4 +/- 0.5 vs 1.7 +/- 1.1 and 1.2 +/- 1.1 vs 3.0 +/- 1.2; P less than 0.05 by t-test). There were no differences in lavage RBC count between FG and C (13.1 x 106 +/- 4.1 x 10(6) vs 8.7 x 106 +/- 3.2 x 10(6)). Fibrin gel significantly decreased incisional and colonic adhesions and reduced other abdominal adhesion formation by a nonhemostatic dependent mechanism.

Development of a selection index to improve market value of cultured Atlantic salmon (Salmo salar).

Genetic parameters were estimated on growth and development traits using analyses of variance and covariance of 42 full-sib families from a select line, 39 full-sib families from a control line of the same strain, and 37 full-sib families from another unselected strain. The traits included percent 1+ smolts, percent sexually immature fish after 1 year in seawater (nongrilse), and fork length measured at intervals throughout the production cycle. The number of fish sampled per family was 30 of 300-1500 for all freshwater traits and 15-60, i.e., all individuals present, for all seawater traits. Heritability estimates of freshwater traits had a broad range (0.15-0.61), but estimates were lower for seawater traits (0.06-0.29). There was a general reduction in heritability estimates for traits measured at increasing ages both in freshwater and seawater. These reductions may in part represent declines of maternal and common environmental effects that inflate heritability estimated from full-sib families. The genetic correlations indicated positive associations between freshwater and seawater growth parameters. However, the correlations decreased with increasing intervals between measurements. A selection index was developed using the estimates of the genetic and phenotypic parameters for three economically important traits: percent 1 + smolts, percent nongrilse, and harvest length. The seawater traits, percent nongrilse, and fork length at 17 months (harvest length) were the most important in the index.

Growth response of loblolly pine (Pinus taeda L.) seedlings to ozone fumigation.

Twenty-two week-old Pinus taeda L. (loblolly pine) seedlings of 30 open-pollinated and five full-sib families, representing a wide range in geographic origin, were grown in charcoal-filtered (CF) air or CF-air supplemented with 160 or 320 nl liter(-1) ozone for 8 h day(-1), 4 days week(-1), for 9 weeks. Visible foliar injury (banded chlorosis, tip burn and premature senescence) was apparent in many families after 3 weeks in 320 nl liter(-1) and 6 weeks in 160 nl liter(-1) ozone. Decreases in relative height and root collar diameter growth rates, total dry weight, root dry weight, shoot dry weight, and root/shoot ratios were evident after 9 weeks of treatment with both 160 and 320 nl liter(-1) ozone. For relative height growth rates, family differences in response to ozone were observed. By the study's end, net photosynthesis rates were 15% less for the 320 nl liter(-1) ozone treatment as compared to the CF-air treatment. Total soluble sugar and total starch content of roots were not changed after 9 weeks of ozone exposure.

Considerations of a method of analyzing diallel crosses of atlantic salmon.

Inferences derived from a proposed mixed model analysis of a diallel cross involving four stocks of Atlantic salmon (Salmo salar) are illustrated with growth data on weight and length. Variation between stocks was more apparent when samples represented dams as opposed to sires, thus stressing the relative importance of maternal effects. However, the ranking of stocks was not altered when either the means of sire sources or the means of dam sources were considered. No heterotic effects were found for the growth traits studied.