Conserved community structure and simultaneous divergence events in the fig wasps associated with Ficus benjamina in Australia and China

Localised patterns of species diversity can be influenced by many factors, including regional species pools, biogeographic features and interspecific interactions. Despite recognition of these issues, we still know surprisingly little about how invertebrate biodiversity is structured across geographic scales. In particular, there have been few studies of how insect communities vary geographically while using the same plant host. We compared the composition (species, genera) and functional structure (guilds) of the chalcid wasp communities associated with the widespread fig tree, Ficus benjamina, towards the northern (Hainan province, China) and southern (Queensland, Australia) edges of its natural range. Sequence data were generated for nuclear and mtDNA markers and used to delimit species, and Bayesian divergence analyses were used to test patterns of community cohesion through evolutionary time. Both communities host at least 14 fig wasp species, but no species are shared across continents. Community composition is similar at the genus level, with six genera shared although some differ in species diversity between China and Australia; a further three genera occur in only China or Australia. Community functional structure remains very similar in terms of numbers of species in each ecological guild despite community composition differing a little (genera) or a lot (species), depending on taxonomic level. Bayesian clustering analyses favour a single community divergence event across continents over multiple events for different ecological guilds. Molecular dating estimates of lineage splits between nearest inter-continental species pairs are broadly consistent with a scenario of synchronous community divergence from a shared "ancestral community". Fig wasp community structure and genus-level composition are largely conserved in a wide geographic comparison between China and Australia. Moreover, dating analyses suggest that the functional community structure has remained stable for long periods during historic range expansions. This suggests that ecological interactions between species may play a persistent role in shaping these communities, in contrast to findings in some comparable temperate systems

Paleodistributions and Comparative Molecular Phylogeography of Leafcutter Ants (Atta spp.) Provide New Insight into the Origins of Amazonian Diversity

The evolutionary basis for high species diversity in tropical regions of the world remains unresolved. Much research has focused on the biogeography of speciation in the Amazon Basin, which harbors the greatest diversity of terrestrial life. The leading hypotheses on allopatric diversification of Amazonian taxa are the Pleistocene refugia, marine incursion, and riverine barrier hypotheses. Recent advances in the fields of phylogeography and species-distribution modeling permit a modern re-evaluation of these hypotheses. Our approach combines comparative, molecular phylogeographic analyses using mitochondrial DNA sequence data with paleodistribution modeling of species ranges at the last glacial maximum (LGM) to test these hypotheses for three co-distributed species of leafcutter ants (Atta spp.). The cumulative results of all tests reject every prediction of the riverine barrier hypothesis, but are unable to reject several predictions of the Pleistocene refugia and marine incursion hypotheses. Coalescent dating analyses suggest that population structure formed recently (Pleistocene-Pliocene), but are unable to reject the possibility that Miocene events may be responsible for structuring populations in two of the three species examined. The available data therefore suggest that either marine incursions in the Miocene or climate changes during the Pleistocene—or both—have shaped the population structure of the three species examined. Our results also reconceptualize the traditional Pleistocene refugia hypothesis, and offer a novel framework for future research into the area

A cross-cultural investigation of cognitions and depressive symptoms in adolescents

Adolescents (N=2,272) from Hong Kong and the United States provided information regarding their depressive symptoms, cognitions (self-efficacy, negative cognitive errors, and hopelessness), and stressful events between 2 surveys 6 months apart. Depressive symptoms and hopelessness were higher, and self-efficacy and negative cognitive errors were lower in Hong Kong than in the United Stales. Cognitions were associated with concurrent depressive symptoms and predicted depressive symptoms 6 months later in both cultures. The 'reverse' model was also supported with more variance predicted by depressive symptoms to later cognitions than from cognitions to depressive symptoms. There was some support for the hypothesis that self-efficacy is less salient in collective compared with individualistic cultures. These findings extend cognitive theories of depression to a non-Western culture

Associations between Social Support from Family, Friends, and Teachers and depressive Symptoms in Adolescents

Accepted: 17 June 2017Approximately 20% of adolescents develop depressive symptoms. Family, friends, and teachers are crucial sources of social support for adolescents, but it is unclear whether social support impacts adolescents directly (principle-effect model) or by moderating the effect of stress (stress-buffer model) and whether each source of social support remains meaningful when their influence is studied simultaneously. To help fill this gap, we followed 1452 Australian students (average age at enrollment = 13.1, SD = 0.5; range: 11-16 years; 51.9% female) for 5 years. Based on our findings, each source of support is negatively related to depressive symptoms one year later when studied independently but when combined, only family and teacher support predicted depressive symptoms. Family support in all grades and teacher support in grade 8 to 10 but not in grade 11 directly impacted adolescent depressive symptoms 1 year later. Family support in grades 8 and 11 also buffered against the negative impact of stress on depressive symptoms one year later. Based on the unexpected findings, the most important limitations seem to be that the used instruments do not allow for a separation of different groups of friends (e.g., classmates, same-gender peers, romantic partners), types of social support, and stress. In addition, the high, nonrandom attrition rate with adolescents reporting less social support, more stressful events, a higher frequency of depressive symptoms, and/or being of Torres Strait Islander or Aboriginal background limits the generalizability of our findings. Summarized, our findings demonstrate that adolescents facing stress might benefit more from family support compared to their peers without stressful life events and that friends may have a weaker presence in adolescent lives than expected.Patrick Pössel, Shelby M. Burton, Bridget Cauley, Michael G. Sawyer, Susan H. Spence, Jeanie Sheffiel