52 resultados para paper wasps


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It is thought that speciation in phytophagous insects is often due to colonization of novel host plants, because radiations of plant and insect lineages are typically asynchronous. Recent phylogenetic comparisons have supported this model of diversification for both insect herbivores and specialized pollinators. An exceptional case where contemporaneous plant insect diversification might be expected is the obligate mutualism between fig trees (Ficus species, Moraceae) and their pollinating wasps (Agaonidae, Hymenoptera). The ubiquity and ecological significance of this mutualism in tropical and subtropical ecosystems has long intrigued biologists, but the systematic challenge posed by >750 interacting species pairs has hindered progress toward understanding its evolutionary history. In particular, taxon sampling and analytical tools have been insufficient for large-scale co-phylogenetic analyses. Here, we sampled nearly 200 interacting pairs of fig and wasp species from across the globe. Two supermatrices were assembled: on average, wasps had sequences from 77% of six genes (5.6kb), figs had sequences from 60% of five genes (5.5 kb), and overall 850 new DNA sequences were generated for this study. We also developed a new analytical tool, Jane 2, for event-based phylogenetic reconciliation analysis of very large data sets. Separate Bayesian phylogenetic analyses for figs and fig wasps under relaxed molecular clock assumptions indicate Cretaceous diversification of crown groups and contemporaneous divergence for nearly half of all fig and pollinator lineages. Event-based co-phylogenetic analyses further support the co-diversification hypothesis. Biogeographic analyses indicate that the presentday distribution of fig and pollinator lineages is consistent with an Eurasian origin and subsequent dispersal, rather than with Gondwanan vicariance. Overall, our findings indicate that the fig-pollinator mutualism represents an extreme case among plant-insect interactions of coordinated dispersal and long-term co-diversification.

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We summarise the response of the EAA’s FRSC to Towards a Disclosure Framework for the Notes, a Discussion Paper (DP) issued jointly by EFRAG, ANC and FRC. While supportive of much of the DP, and in particular of the underlying aim to place disclosures on a sounder conceptual foundation, we identify two broad themes for further development. The first concerns the DP’s diagnosis of the problem, which is that the existing financial reporting is characterised by, on the one hand, disclosure overload and, on the other hand, an absence of a conceptual framework for organising and communicating disclosures. Our review of the literature suggests much greater support for the second of these two factors than for the first. The second broad theme is the purpose of the proposed DF, and the principles that are derived from this purpose. Here, we stress the need for the framework to better accommodate the context within which financial statement disclosures are used. In practice, this context is characterised by variation in information, incentives and enforcement, each of which has a considerable effect on the appropriate disclosure policy and practice in any given situation.