Total Bee Dependence on One Flower Species Despite Available Congeners of Similar Floral Shape

<div><p>Extreme specialization is a common phenomenon in antagonistic biotic interactions but it is quite rare in mutualistic ones. Indeed, bee specialization on a single flower species (monolecty) is a questioned fact. Here, we provide multiple lines of evidence on true monolecty in a solitary bee (<i>Flavipanurgus venustus</i>, Andrenidae), which is consistent across space (18 sites in SW Iberian Peninsula) and time (three years) despite the presence of closely related congeneric plant species whose flowers are morphologically similar. The host flower (<i>Cistus crispus</i>, Cistaceae) is in turn a supergeneralist, visited by at least 85 insect species. We uncover ultraviolet light reflectance as a distinctive visual cue of the host flower, which can be a key mechanism because bee specialization has an innate basis to recognize specific signals. Moreover, we hypothesized that a total dependence on an ephemeral resource (i.e. one flower species) must lead to spatiotemporal matching with it. Accordingly, we prove that the bee’s flight phenology is synchronized with the blooming period of the host flower, and that the densities of bee populations mirror the local densities of the host flower. This case supports the ‘predictable plethora’ hypothesis, that is, that host-specialization in bees is fostered by plant species providing predictably abundant floral resources. Our findings, along with available phylogenetic information on the genus <i>Cistus</i>, suggest the importance of historical processes and cognitive constraints as drivers of specialization in bee-plant interactions.</p></div

Hohenberg-Kohn-Sham density functional theory

The emergence of a family of computational methods, known under the label ‘density functional theory∈dex theory! density functional ' or ‘DFT', revolutionalized the field of computer modelling of complex molecular systems. Many computational schemes belonging to the DFT family are currently in use. Some of them are designed to be universal (nonempirical) whereas other to treat specific systems and/or properties (empirical). This review starts with the introduction of the formal elements underlying all these methods: Hohenberg-Kohn theorems∈dex theorem! Hohenberg-Kohn, reference system∈dex reference system of noninteracting electrons∈dex reference system! noninteracting electrons, exchange-correlation energy∈dex energy functional! exchange-correlation functional∈dex functional, and the Kohn-Sham equations∈dex equation! Kohn-Sham. The main roads to approximate the exchange-correlation-energy functional based on: local density approximation∈dex approximation! local density (LDA), generalized gradient approximation∈dex approximation! generalized gradient (GGA), meta-GGA∈dex energy functional! exchange-correlation! meta-GGA, and adiabatic connection∈dex adiabatic connection formula (hybrid functionals∈dex energy functional! exchange-correlation! hybrid ), are outlined. The performance of these approximations in describing molecular properties of relevance to intermolecular interaction∈dex interactions! intermolecular s and their interactions with environment in condensed phase (ionization potential∈dex potential! ionization s, electron∈dex electron affinities∈dex electron! affinity, electric moments∈dex electric moment, polarizabilities∈dex polarizability ) is reviewed. Developments concerning new methods situated within the general Hohenberg-Kohn-Sham framework or closely related to it are overviewed in the last sectio