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Birds in some species produce two broods in a season to maximize reproductive success, but in species such as the northern house wren (Troglodytes aedon), not all individuals produce a second brood even if they have enough time to do so. We investigated whether variation in individual quality, in addition to time-of-season, explains some of the variation in the likelihood of producing a second brood. We examined the effects of individual age, body condition, and territory quality, and estimated the repeatability of producing a second brood using breeding records from a long-term dataset. We also cross-fostered eggs between earlier-nesting females (presumed high quality) and later-nesting females (presumed low quality) to delay or advance the natural nesting date, exposing an effect of quality if present. There was little evidence that the individual traits measured affected the production of a second brood. Cross-fostered, delayed females did not differ from the control in their likelihood of producing a second brood, but advanced females were more likely to produce a second brood compared with the control. However, the production of a second brood was significantly repeatable, and this repeatability was substantially higher after accounting for variation in timing of the first brood. This suggests that individual characteristics, in addition to time-of-season, have a substantial effect on the likelihood of producing a second brood, but that further studies are needed to identify the specific traits responsible for this effect. 

Birds in some species produce two broods in a season to maximize reproductive success, but in species such as the northern house wren (Troglodytes aedon) not all individuals produce a second brood even if they have enough time to do so. We investigated whether variation in individual quality, in addition to time-of-season, explains some of the variation in the likelihood of producing a second brood. We examined the effects of individual age, body condition, and territory quality, and estimated the repeatability of producing a second brood using breeding records from a long-term dataset. We also cross-fostered eggs between earlier-nesting females (presumed high quality) and later-nesting females (presumed low quality) to delay or advance the natural nesting date, exposing an effect of quality if present. There was little evidence that the individual traits measured affected the production of a second brood. Cross-fostered, delayed females did not differ from the control in their likelihood of producing a second brood, but advanced females were more likely to produce a second brood compared with the control. However, the production of a second brood was significantly repeatable, and this repeatability was substantially higher after accounting for variation in timing of the first brood. This suggests that individual characteristics, in addition to time-of-season, have a substantial effect on the likelihood of producing a second brood, but that further studies are needed to identify the specific traits responsible for this effect. 

Nonsymmetrical oxygen-bridged binuclear copper centers have been proposed and modeled as intermediates and transition states in several C─H oxidation pathways, leading to the postulation that structural dissymmetry enhances the reactivity of the bridging oxygen. However, experimentally characterizing the structure and reactivity of these transient species is remarkably challenging. Here, we report the high-pressure synthesis of a metastable nonsymmetrical dicopper-μ-oxo compound with exceptional reactivity toward the mono-oxygenation of aliphatic C─H bonds. The nonequivalent coordination environment of copper stabilizes localized mixed valency and greatly enhances the hydrogen atom abstraction activity of the bridging oxygen, enabling room-temperature hydroxylation of methane under pressure. These findings highlight the role of dissymmetry in the reactivity of binuclear copper centers and demonstrate precise control of molecular structures by mechanical means. 

Abstract In this work, we investigate trion dynamics occurring at the heterojunction between organometallic molecules and a monolayer transition metal dichalcogenide (TMD) with transient electronic sum frequency generation (tr‐ESFG) spectroscopy. By pumping at 2.4 eV with laser pulses, we have observed an ultrafast hole transfer, succeeded by the emergence of charge‐transfer trions. This observation is facilitated by the cancellation of ground state bleach and stimulated emission signals due to their opposite phases, making tr‐ESFG especially sensitive to the trion formation dynamics. The presence of charge‐transfer trion at molecular functionalized TMD monolayers suggests the potential for engineering the local electronic structures and dynamics of specific locations on TMDs and offers a potential for transferring unique electronic attributes of TMD to the molecular layers. 

One of the most fundamental goals of modern biology is to achieve a deep understanding of the origin and maintenance of biodiversity. It has been observed that in some mixed-species animal societies, there appears to be a drive towards some degree of phenotypic trait matching, such as similar coloration or patterning. Here we build on these observations and hypothesize that selection in mixed-species animal societies, such as mixed-species bird flocks, may drive diversification, potentially leading to speciation. We review evidence for possible convergent evolution and even outright mimicry in flocks from southwestern China, where we have observed several cases in which species and subspecies differ from their closest relatives in traits that match particular flock types. However, understanding whether this is phenotypic matching driven by convergence, and whether this divergence has promoted biodiversity, requires testing multiple facets of this hypothesis. We propose a series of steps that can be used to tease apart alternative hypotheses to build our understanding of the potential role of convergence in diversification in participants of mixed-species societies. Even if our social convergence/divergence hypothesis is not supported, the testing at each step should help highlight alternative processes that may affect mixed-species flocks, trait evolution and possible convergence. This article is part of the theme issue ‘Mixed-species groups and aggregations: shaping ecological and behavioural patterns and processes’.