The maintenance of phenotypic divergence through sexual selection: An experimental study in barn swallows Hirundo rustica.

Previous studies have shown that sexual signals can rapidly diverge among closely related species. However, we lack experimental studies to demonstrate that differences in trait-associated reproductive performance maintain sexual trait differences between closely related populations, in support for a role of sexual selection in speciation. Populations of Northern Hemisphere distributed barn swallows Hirundo rustica are closely related, yet differ in two plumage-based traits: ventral color and length of the outermost tail feathers (streamers). Here we provide experimental evidence that manipulations of these traits result in different reproductive consequences in two subspecies of barn swallow: (H. r. erythrogaster in North America and H. r. transitiva in the East Mediterranean). Experimental results in Colorado, USA, demonstrate that males with (1) darkened ventral coloration and (2) shortened streamers gained paternity between two successive reproductive bouts. In contrast, exaggeration of both traits improved reproductive performance within H. r. transitiva in Israel: males with a combination treatment of darkened ventral coloration and elongated streamers gained paternity between two successive reproductive bouts. Collectively, these experimental results fill an important gap in our understanding for how divergent sexual selection maintains phenotype differentiation in closely related populations, an important aspect of the speciation process.

Variation in access to community rehabilitation services and length of stay in hospital following a hip fracture: a cross-sectional study.

OBJECTIVES: To assess variation in access to and use of community rehabilitation services for patients with a hip fracture, and whether this affects length of stay in hospital. DESIGN: Cross-sectional study using administrative patient-level data from Hospital Episode Statistics (HES) and organisational survey data. SETTING: A regional health economy in South West England served by four acute National Health Service (NHS) hospital trusts and six former Primary Care Trusts (PCTs). POPULATION: 1230 hip fracture patients treated in an acute hospital between 1 April 2011 and 29 February 2012. MAIN OUTCOMES: Information about access to community rehabilitation services for each acute hospital and PCT, reported by organisational survey. Rates of patients transferred from acute hospital to community rehabilitation hospitals (CRH) across eight groups with varying access; determined by acute hospital and PCT. Median lengths of stay in the acute hospital, and in the acute hospital plus CRH combined. Associations between the rate of transfer to a CRH and median lengths of stay assessed using Spearman's rank correlation coefficient (rs). RESULTS: Access to community rehabilitation services varied, including the number of CRH inpatient beds, formal access criteria and waiting times. In one PCT, no home-based rehabilitation service was available. The percentage of patients transferred to a CRH ranged from 2.1% to 54.7%. A higher transfer rate was associated with a shorter median length of stay in the acute hospital (rs=-0.8; p=0.01), but a longer median combined length of stay in the acute hospital and CRH (rs=+0.7; p=0.04). CONCLUSIONS: Within one geographical area, there was wide variation in availability and use of community rehabilitation services for patients discharged from an acute hospital following a hip fracture. Reliance on transfers to community rehabilitation hospitals was associated with a longer length of stay in the NHS.