Columnar Hosts Research Articles

Specialization and performance trade‐offs across hosts in cactophilic Drosophila species

1. We assessed the host‐related niche breadth for D. koepferae and D. buzzatii, a pair of sibling cactophilic species with contrasting backgrounds of host use. We tested for the ‘Jack of all trades‐ Master of none’ scenario predicting a more evident exhibition in D. buzzatii rather than in the supposedly specialist D. koepferae.2. Additionally, using laboratory strains of both species selected for tolerance to extremely high concentrations of a columnar cacti's secondary metabolites, we tested whether adaptation to a high‐demanding host involved the loss of performance capabilities in other hosts.3. D. buzzatii was more affected by the artificial host shifts than D. koepferae which presented an overall better performance when rearing in novel columnar hosts.4. Artificially selected strains of D. buzzatii performed poorer in both novel and native natural hosts compared with control strain indicating that adaptation carried associated costs regarding the potential to exploit other cacti. Conversely, artificial evolution of the D. koepferae's strains did not translate into decreased performance in other hosts.5. D. buzzatii complied better with the predictions of the Jack of all trades‐Master of none hypothesis.6. Host specialization is a dynamic feature in the repleta group and a major driver of diversification in its evolutionary history. As the group presents an Opuntia breeder as the ancestral condition, D. buzzatii would represent not only a plesiomorphic state of host use but also the ancestral ecological strategy of specialization.

Self-Assembled Benzophenone Bis-urea Macrocycles Facilitate Selective Oxidations by Singlet Oxygen

This manuscript investigates how incorporation of benzophenone, a well-known triplet sensitizer, within a bis-urea macrocycle, which self-assembles into a columnar host, influences its photophysical properties and affects the reactivity of bound guest molecules. We further report the generation of a remarkably stable organic radical. As expected, UV irradiation of the host suspended in oxygenated solvents efficiently generates singlet oxygen similar to the parent benzophenone. In addition, this host can bind guests such as 2-methyl-2-butene and cumene to form stable solid host-guest complexes. Subsequent UV irradiation of these complexes facilitated the selective oxidation of 2-methyl-2-butene into the allylic alcohol, 3-methyl-2-buten-1-ol, at 90% selectivity as well as the selective reaction of cumene to the tertiary alcohol, α,α'-dimethyl benzyl alcohol, at 63% selectivity. However, these products usually arise through radical pathways and are not observed in the presence of benzophenone in solution. In contrast, typical reactions with benzophenone result in the formation of the reactive singlet oxygen that reacts with alkenes to form endoperoxides, diooxetanes, or hydroperoxides, which are not observed in our system. Our results suggest that the confinement, the formation of a stable radical species, and the singlet oxygen photoproduction are responsible for the selective oxidation processes. A greater understanding of the mechanism of this selective oxidation could lead to development of greener oxidants.

Formation of chiral 2 1-helical columnar host system with phenylacetylene unit by using (1 R,2 S)-2-amino-1,2-diphenylethanol

A tunable supramolecular phenylacetylene host system with a chiral channel-like cavity is developed by using (1 R,2 S)-2-amino-1,2-diphenylethanol. This host system possesses a chiral 2 1-helical columnar structure; chiral cavities are constructed by the self-assembly of the 2 1-helical column, and guest molecules are included by varying the packing of this column.

Tuning Mechanism in a Two-Component Columnar Host System Composed of 1,2-Diphenylethylenediamine and 1,1‘-Binaphthyl-2,2‘-dicarboxylic Acid

In a two-component columnar host system composed of racemic (rac)-1,2-diphenylethylenediamine and rac-1,1'-binaphthyl-2,2'-dicarboxylic acid, a cavity tuning mechanism resulted from changes in the structure of the columns using a specific combination of the following four molecules: (1R,2R)-1, (1S,2S)-1, (R)-2, and (S)-2.

Multiple molecular response columnar host system composed of rac-2-amino-1,2-diphenylethanol and 1-fluorenecarboxylic acid

By using racemic (rac)-2-amino-1,2-diphenylethanol and achiral fluorescent 1-fluorenecarboxylic acid, a two-component columnar host system with multiple molecular response (guest-dependent spontaneous resolution and fluorescence) properties in the solid state was created.

π-共役型光学活性21-helical columnarホストシステムの創製

π-共役型光学活性21-helical columnarホストシステムの創製

Developmental Time and Thorax Length Differences Between the Cactophilic Species Drosophila Buzzatii and D. Koepferae Reared in Different Natural Hosts

Drosophila buzzatii and Drosophila koepferae are two cactophilic sibling species whose ranges partially overlap in Northwestern and Western Argentina. Both species can utilize the decaying tissues of both Opuntia and columnar cacti as breeding sites. Though D. buzzatii and D. koepferae are not differentially attracted to Opuntia and columnar hosts, the composition of the communities of flies emerging from natural substrates of both cacti differed significantly in a natural population. The objective of this paper is to analyze whether intra and/or interspecific competition affects development time and thorax length in D. buzzatii and D. koepferae when both species are reared in single and mixed species culture and fed with semi-natural media prepared with fermenting materials of Opuntia sulphurea(tuna) and Trichocereus terschekii(cardon). Our results showed that both traits differ significantly between flies raised in different hosts and that differences between D. koepferae and D. buzzatii species for both thorax length and development time depend on the type of culture (mixed vs. single species). In addition, the host by type of culture interaction was significant. We also observed thorax length differences between Drosophila species and type of culture. Our present data suggest that the effect of intra and interspecific competition varied between the two traits investigated and between species. However, competition alone cannot explain the differential pattern of resource utilization shown by D. buzzatii and D. koepferae in the natural population studied.