Variations on a theme: diversification of cuticular hydrocarbons in a clade of cactophilic Drosophila

<p>Abstract</p> <p>Background</p> <p>We characterized variation and chemical composition of epicuticular hydrocarbons (CHCs) in the seven species of the <it>Drosophila buzzatii </it>cluster with gas chromatography/mass spectrometry. Despite the critical role of CHCs in providing resistance to desiccation and involvement in communication, such as courtship behavior, mating, and aggregation, few studies have investigated how CHC profiles evolve within and between species in a phylogenetic context. We analyzed quantitative differences in CHC profiles in populations of the <it>D. buzzatii </it>species cluster in order to assess the concordance of CHC differentiation with species divergence.</p> <p>Results</p> <p>Thirty-six CHC components were scored in single fly extracts with carbon chain lengths ranging from C₂₉to C₃₉, including methyl-branched alkanes, <it>n</it>-alkenes, and alkadienes. Multivariate analysis of variance revealed that CHC amounts were significantly different among all species and canonical discriminant function (CDF) analysis resolved all species into distinct, non-overlapping groups. Significant intraspecific variation was found in different populations of <it>D. serido </it>suggesting that this taxon is comprised of at least two species. We summarized CHC variation using CDF analysis and mapped the first five CHC canonical variates (CVs) onto an independently derived <it>period </it>(<it>per</it>) gene + chromosome inversion + mtDNA COI gene for each sex. We found that the COI sequences were not phylogenetically informative due to introgression between some species, so only <it>per </it>+ inversion data were used. Positive phylogenetic signal was observed mainly for CV1 when parsimony methods and the test for serial independence (TFSI) were used. These results changed when no outgroup species were included in the analysis and phylogenetic signal was then observed for female CV3 and/or CV4 and male CV4 and CV5. Finally, removal of divergent populations of <it>D. serido </it>significantly increased the amount of phylogenetic signal as up to four out of five CVs then displayed positive phylogenetic signal.</p> <p>Conclusions</p> <p>CHCs were conserved among species while quantitative differences in CHC profiles between populations and species were statistically significant. Most CHCs were species-, population-, and sex-specific. Mapping CHCs onto an independently derived phylogeny revealed that a significant portion of CHC variation was explained by species' systematic affinities indicating phylogenetic conservatism in the evolution of these hydrocarbon arrays, presumptive waterproofing compounds and courtship signals as in many other drosophilid species.</p

Labile evolution of display traits in bowerbirds indicates reduced effects of phylogenetic constraint

Bowerbirds (Ptilonorhynchidae) have among the most exaggerated sets of display traits known, including bowers, decorated display courts and bright plumage, that differ greatly in form and degree of elaboration among species. Mapping bower and plumage traits on an independently derived phylogeny constructed from mitochondrial cytochrome b sequences revealed large differences in display traits between closely related species and convergences in both morphological and behavioural traits. Plumage characters showed no effect of phylogenetic inertia, although bowers exhibited some constraint at the more fundamental level of design, but above which they appeared free of constraint. Bowers and plumage characters, therefore, are poor indicators of phylogenetic relationship in this group. Testing Gilliard's (1969) transferral hypothesis indicated some support for the idea that the focus of display has shifted from bird to bower in avenue-building species, but not in maypole-builders or in bowerbirds as a whole

Difficulty concentrating in generalized anxiety disorder: An evaluation of incremental utility and relationship to worry

Difficulty concentrating is one of the most common diagnostic criteria across DSM-5 categories, especially within the emotional (mood- and anxiety-related) disorders. A substantial literature has characterized cognitive functioning in emotional disorders using objective (behavioral) computerized cognitive tasks. However, diagnoses are typically formed on the basis of subjective (self-reported; clinician-rated) assessments of symptoms, and little is known about difficulty concentrating as a symptom. These questions are particularly important for generalized anxiety disorder (GAD), which has long been the subject of nosological debates, and for which several theoretical models that suggest a central role for cognitive impairments (including difficulty concentrating) in the maintenance of psychopathology have been proposed. The present study evaluated the incremental utility of difficulty concentrating and its relationship to worry and other symptoms in 175 GAD-diagnosed adults. Clinician-assessed difficulty concentrating incrementally predicted clinician-rated GAD, anxiety, and depression severity even after other GAD symptoms were controlled. Consistent with theoretical models of GAD that propose a direct relationship between worry and cognitive impairment, difficulty concentrating mediated the relationship between trait worry and clinical severity. These findings suggest that difficulty concentrating has value as a diagnostic criterion and is a potential mechanism by which worry increases distress and impairment

Worry alters speed-accuracy tradeoffs but does not impair sustained attention

Worry has been experimentally linked to a range of cognitive consequences, including impairments in working memory, inhibition, and cognitive control. However, findings are mixed, and the effects of worry on other phenomenologically-relevant constructs, such as sustained attention, have received less attention. Potential confounds such as speed-accuracy tradeoffs have also received little attention, as have psychometric and related design considerations, and potential moderators beyond trait worry. The present study investigated the effects of experimentally-induced worry versus a neutral control condition on speed-accuracy tradeoff-corrected performance on a validated measure of sustained attention (88 participants; within-subjects). Moderation by trait worry and trait mindfulness was probed in confirmatory and exploratory analyses, respectively. Worry led to faster and less accurate responding relative to the neutral comparison condition. There was no main effect of condition or trait worry on sustained attention after accounting for speed-accuracy tradeoffs. In exploratory analyses, higher trait mindfulness was robustly related to better post-worry performance, including after controlling for trait worry, general distress, and post-neutral performance, and correction for multiple comparisons. Follow-up analyses exploring dissociable mindfulness facets found a robust relationship between present-moment attention and post-worry performance. Future research should experimentally manipulate mindfulness facets to probe causality and inform treatment development

Neural Mechanisms of Mindful Disengagement from Worry

Uncontrollable worry is a hallmark of generalized anxiety disorder and a transdiagnostic feature of psychopathology. Mindfulness-based strategies show promise for treating worry, but neural mechanisms of mindful disengagement remain incompletely characterized. We recruited 40 participants with clinically significant worry to undergo fMRI while engaging in real-time, idiographic worry and instructed disengagement using two mindfulness strategies (focused attention; acceptance) and one comparison strategy (suppression). Hypotheses were preregistered and partially supported. All disengagement strategies downregulated default mode and upregulated frontoparietal and salience networks. Focused attention was most effective for promoting disengagement and elicited decreased activity in cognitive control and sensorimotor regions. Successful disengagement was associated with increased activity in rostrolateral prefrontal cortex and functional connectivity between posterior cingulate and primary somatosensory cortex. Findings support the role of cognitive control and somatosensory networks in disengagement from worry and suggest common and distinct mechanisms of disengagement, with focused attention a particularly promising strategy