Müllerian mimicry among bees and wasps: a review of current knowledge and future avenues of research.

Many bees and stinging wasps, or aculeates, exhibit striking colour patterns or conspicuous coloration, such as black and yellow stripes. Such coloration is often interpreted as an aposematic signal advertising aculeate defences: the venomous sting. Aposematism can lead to Müllerian mimicry, the convergence of signals among different species unpalatable to predators. Müllerian mimicry has been extensively studied, notably on Neotropical butterflies and poison frogs. However, although a very high number of aculeate species harbour putative aposematic signals, aculeates are under-represented in mimicry studies. Here, we review the literature on mimicry rings that include bee and stinging wasp species. We report over a hundred described mimicry rings, involving a thousand species that belong to 19 aculeate families. These mimicry rings are found all throughout the world. Most importantly, we identify remaining knowledge gaps and unanswered questions related to the study of Müllerian mimicry in aculeates. Some of these questions are specific to aculeate models, such as the impact of sociality and of sexual dimorphism in defence levels on mimicry dynamics. Our review shows that aculeates may be one of the most diverse groups of organisms engaging in Müllerian mimicry and that the diversity of aculeate Müllerian mimetic interactions is currently under-explored. Thus, aculeates represent a new and major model system to study the evolution of Müllerian mimicry. Finally, aculeates are important pollinators and the global decline of pollinating insects raises considerable concern. In this context, a better understanding of the impact of Müllerian mimicry on aculeate communities may help design strategies for pollinator conservation, thereby providing future directions for evolutionary research.

Desulfonative Suzuki-Miyaura Coupling of Sulfonyl Fluorides.

Sulfonyl fluorides have emerged as powerful "click" electrophiles to access sulfonylated derivatives. Yet, they are relatively inert towards C-C bond forming transformations, notably under transition-metal catalysis. Here, we describe conditions under which aryl sulfonyl fluorides act as electrophiles for the Pd-catalyzed Suzuki-Miyaura cross-coupling. This desulfonative cross-coupling occurs selectively in the absence of base and, unusually, even in the presence of strong acids. Divergent one-step syntheses of two analogues of bioactive compounds showcase the expanded reactivity of sulfonyl fluorides to encompass both S-Nu and C-C bond formation. Mechanistic experiments and DFT calculations suggest oxidative addition occurs at the C-S bond followed by desulfonation to form a Pd-F intermediate that facilitates transmetalation.

Composition and organization of highly speciose Empidoidea (Diptera) communities in tropical montane forests of northern Thailand.

This study is based on more than 25,000 specimens of the superfamily Empidoidea (Diptera) collected throughout a full year on a 2000 m elevational habitat succession gradient along a 21 km transect on Doi Inthanon, the highest mountain in Thailand. The samples were sorted to 58 genera and 458 morphospecies (Empididae, 73; Hybotidae, 203; Dolichopodidae, 179; Brachystomatidae, 3).                                                                                                                          The data were used to prepare the first thorough taxon-focussed description of how diversity of a major group of Diptera is structured in tropical forest biotopes. We found significant spatial (elevation / habitat) and temporal (seasonal) variations in richness (α-diversity) and abundance at family-level. α-Diversity of the four families was maximal in damp evergreen forests at higher elevation (1500-2500 m), but Dolichopodidae also had a major subsidiary peak in lowland dry evergreen forest at 500-1000 m. Genus-, tribe- and subfamily level α-diversity / elevation profiles were varied, indicating that overall family-level richness is a composite of many taxa that contribute low, high or mid-elevation specialisms. We provide a detailed analysis of these specialisms for each of the 58 genera. Adult phenology was correlated with the monsoon and had three characteristic phases: (i) pre-monsoon commencement during the latter part of the hot dry season, (ii) a 'flush' of maximal richness during the early-monsoon, and (iii) a secondary richness maximum associated with the late-monsoon. Maximum α-diversity occurred in phases (i) and (ii) but communities in phase (iii) had characteristically low evenness in which a few abundant species were dominant. Cluster analysis and ordination resolved three well-founded communities with different species-abundance distributions, high levels of species-level specialism and habitat-fidelity associated with moist hill evergreen forest (MHE) at >2000 m; mid elevation evergreen forests (EM) at 1000-2000 m and dry lowland forest (DL) at 1000 m. The three forest types with which these communities are associated are widespread and typical of northern Thailand and the diversity characteristics of each habitat are likely scalable to larger geographic areas. The transition from lowland DL through to upper montane MHE communities was generally characterised by increasing abundance, lower evenness (higher dominance), slower temporal turnover of community composition (relaxation of seasonality), longer periods of adult flight activity and rare species contributing less to species richness. Oriental biogeographic influences are strong at lower elevations but Palaearctic influences are increasingly important at higher elevations. The mixing of Oriental and Palaearctic elements in MHE forests is thought to explain the greater phylogenetic complexity at higher elevation (as measured by taxonomic distinctness).

Suzuki-Miyaura Coupling of (Hetero)Aryl Sulfones: Complementary Reactivity Enables Iterative Polyaryl Synthesis.

Ideal organic syntheses involve the rapid construction of C-C bonds, with minimal use of functional group interconversions. The Suzuki-Miyaura cross-coupling (SMC) is a powerful way to form biaryl linkages, but the relatively similar reactivity of electrophilic partners makes iterative syntheses involving more than two sequential coupling events difficult to achieve without additional manipulations. Here we introduce (hetero)aryl sulfones as electrophilic coupling partners for the SMC reaction, which display an intermediate reactivity between those of typical aryl (pseudo)halides and nitroarenes. The new complementary reactivity allows for rapid sequential cross-coupling of arenes bearing chloride, sulfone and nitro leaving groups, affording non-symmetric ter- and quateraryls in only 2 or 3 steps, respectively. The SMC reactivity of (hetero)aryl sulfones is demonstrated in over 30 examples. Mechanistic experiments and DFT calculations are consistent with oxidative addition into the sulfone C-S bond as the turnover-limiting step. The further development of electrophilic cross-coupling partners with complementary reactivity may open new possibilities for divergent iterative synthesis starting from small pools of polyfunctionalized arenes.

Native iron reduces CO2 to intermediates and end-products of the acetyl-CoA pathway.

Autotrophic theories for the origin of life propose that CO2 was the carbon source for primordial biosynthesis. Among the six known CO2 fixation pathways in nature, the acetyl-CoA (AcCoA; or Wood-Ljungdahl) pathway is the most ancient, and relies on transition metals for catalysis. Modern microbes that use the AcCoA pathway typically fix CO2 with electrons from H2, which requires complex flavin-based electron bifurcation. This presents a paradox: how could primitive metabolic systems have fixed CO2 before the origin of proteins? Here, we show that native transition metals (Fe0, Ni0 and Co0) selectively reduce CO2 to acetate and pyruvate-the intermediates and end-products of the AcCoA pathway-in near millimolar concentrations in water over hours to days using 1-40 bar CO2 and at temperatures from 30 to 100 °C. Geochemical CO2 fixation from native metals could have supplied critical C2 and C3 metabolites before the emergence of enzymes.