The cost and impact of compulsivity: A research perspective.

Compulsivity is the defining feature of various psychiatric disorders including Obsessive Compulsive Related Disorders (OCRDs), and other compulsive, impulsive, and addictive disorders. These disorders are disabling, chronic conditions with an early onset and high rates of comorbidity, misdiagnoses, and delay in treatment onset. Disorders of compulsivity are responsible for considerable socioeconomic burden to society. We review the costs and impacts of compulsivity. In order to facilitate earlier diagnosis and targeted treatments, we examine the overlapping mechanisms that underlie compulsivity. We reconceptualize psychiatric disorders based on core features of compulsivity, highlight challenges in harmonizing research in children and adults, describe newer research methodologies, and point to future directions that can impact the costs and impact of disorders of compulsivity.

The effects of above- and belowground mutualisms on orchid speciation and coexistence.

Both pollination by animals and mycorrhizal symbioses with fungi are believed to have been important for the diversification of flowering plants. However, the mechanisms by which these above- and belowground mutualisms affect plant speciation and coexistence remain obscure. We provide evidence that shifts in pollination traits are important for both speciation and coexistence in a diverse group of orchids, whereas shifts in fungal partner are important for coexistence but not for speciation. Phylogenetic analyses show that recently diverged orchid species tend either to use different pollinator species or to place pollen on different body parts of the same species, consistent with the role of pollination-mode shifts in speciation. Field experiments provide support for the hypothesis that colonization of new geographical areas requires adaptation to new pollinator species, whereas co-occurring orchid species share pollinator species by placing pollen on different body parts. In contrast to pollinators, fungal partners are conserved between closely related orchid species, and orchids recruit the same fungal species even when transplanted to different areas. However, co-occurring orchid species tend to use different fungal partners, consistent with their expected role in reducing competition for nutrients. Our results demonstrate that the two dominant mutualisms in terrestrial ecosystems can play major but contrasting roles in plant community assembly and speciation.

Flies and flowers in Darwin's race.

The idea of coevolution originated with Darwin's proposal that long-proboscid pollinators and long-tubed flowers might be engaged in reciprocal selection, but this has not been demonstrated. Here we test key aspects of Darwin's hypothesis of reciprocal selection in an experiment with naturally interacting populations of extremely long-proboscid flies (Moegistorhynchus longirostris: Nemestinidae) and long-tubed irises (Lapeirousia anceps: Iridaceae). We show that the benefit derived by both the fly (volume of nectar consumed) and the plant (number pollen grains received) depends on the relative length of their interacting organs. Each trait is shown to act both as agent and target in directional reciprocal selection, potentially leading to a race. This understanding of how fitness in both species varies in relation to the balance of their armament allows us to make tentative predictions about the nature of selection across multiple communities. We find that in each community a core group of long-tubed plant species might together be involved in diffuse coevolution with the fly. In poorly matched populations, the imbalance in armament is too great to allow reciprocal selection to act, and these species might instead experience one-sided selection that leads to convergence with the core species. Reciprocal selection drives the evolution of the community, then, additional species become attached to the network of interacting mutualists by convergence.

Pollinators underestimated: a molecular phylogeny reveals widespread floral convergence in oil-secreting orchids (sub-tribe Coryciinae) of the Cape of South Africa.

The oil-secreting orchids of southern Africa belong to the sub-tribe Coryciinae within Diseae. A phylogeny of Diseae is inferred using sequence data from all genera in the tribe, with an emphasis on resolving generic classifications within Coryciinae. Nuclear (ITS) and plastid (trnLF and matK) gene region sequences were analysed for 79 ingroup taxa and three outgroup taxa. Coryciinae is confirmed to be diphyletic, with Disperis and Coryciinae sensu stricto (s.s.) forming separate monophyletic clades. The current genera Corycium and Pterygodium are not monophyletic according to our analysis and we propose a subdivision of Coryciinae s.s. into 10 monophyletic clades including three monotypic groups. Previous generic classifications of Coryciinae s.s. have been hampered by convergent evolution of floral parts, a consequence of few pollinator species and limited pollinia attachment sites in the oil-bee pollination system common to this group.

Deception above, deception below: linking pollination and mycorrhizal biology of orchids.

Several key characteristics of the species-rich orchid family are due to its symbiotic relationships with pollinators and mycorrhizal fungi. The majority of species are insect pollinated and show strong adaptations for outcrossing, such as pollination by food- and sexual-deception, and all orchids are reliant on mycorrhizal fungi for successful seedling establishment. Recent studies of orchid pollination biology have shed light on the barriers to reproductive isolation important to diversification in different groups of deceptive orchids. Molecular identification of orchid mycorrhizal fungi has revealed high fungal specificity in orchids that obtain organic nutrients from fungi as adults. Both pollinator and fungal specificity have been proposed as drivers of orchid diversification. Recent findings in orchid pollination and mycorrhizal biology are reviewed and it is shown that both associations are likely to affect orchid distribution and population structure. Integrating studies of these symbioses will shed light on the unparalleled diversification of the orchid family.