The role of genetic diversity in the evolution and maintenance of environmentally-cued, male alternative reproductive tactics.

BACKGROUND: Alternative reproductive tactics (ARTs) are taxonomically pervasive strategies adopted by individuals to maximize reproductive success within populations. Even for conditionally-dependent traits, consensus postulates most ARTs involve both genetic and environmental interactions (GEIs), but to date, quantifying genetic variation underlying the threshold disposing an individual to switch phenotypes in response to an environmental cue has been a difficult undertaking. Our study aims to investigate the origins and maintenance of ARTs within environmentally disparate populations of the microscopic bulb mite, Rhizoglyphus robini, that express 'fighter' and 'scrambler' male morphs mediated by a complex combination of environmental and genetic factors. RESULTS: Using never-before-published individual genetic profiling, we found all individuals across populations are highly inbred with the exception of scrambler males in stressed environments. In fact within the poor environment, scrambler males and females showed no significant difference in genetic differentiation (Fst) compared to all other comparisons, and although fighters were highly divergent from the rest of the population in both poor or rich environments (e.g., Fst, STRUCTURE), fighters demonstrated approximately three times less genetic divergence from the population in poor environments. AMOVA analyses further corroborated significant genetic differentiation across subpopulations, between morphs and sexes, and among subpopulations within each environment. CONCLUSION: Our study provides new insights into the origin of ARTs in the bulb mite, highlighting the importance of GEIs: genetic correlations, epistatic interactions, and sex-specific inbreeding depression across environmental stressors. Asymmetric reproductive output, coupled with the purging of highly inbred individuals during environmental oscillations, also facilitates genetic variation within populations, despite evidence for strong directional selection. This cryptic genetic variation also conceivably facilitates stable population persistence even in the face of spatially or temporally unstable environmental challenges. Ultimately, understanding the genetic context that maintains thresholds, even for conditionally-dependent ARTs, will enhance our understanding of within population variation and our ability to predict responses to selection.

Congenital corneal anesthesia in children with the VACTERL association.

PURPOSE: To describe ocular manifestations in patients with the VACTERL (vertebral, anal, cardiovascular, tracheoesophageal, renal, and limb defects) association. METHOD: We reviewed the medical records of patients with the VACTERL association who had undergone treatment for amblyopia at the orthoptic department. RESULTS: A striking similarity was found in three unrelated children, who, in addition to clinical manifestations of VACTERL association, showed total corneal anesthesia of one or both eyes that had resulted in recurrent corneal erosions, keratitis, and permanent corneal opacities. Other ocular manifestations included nonparalytic strabismus, anisometropia, and amblyopia. CONCLUSION: Congenital corneal anesthesia may be part of the VACTERL association.

Vitreous haemorrhage and other ocular complications of a persistent hyaloid artery.

PURPOSE: To report ocular complications of a persistent hyaloid artery. METHODS: We studied eight patients with persistent hyaloid artery. RESULTS: Seven patients showed strabismus and very low visual acuity (< or = 0.12) of one eye. Despite correction of refractive errors, cataract surgery and occlusion therapy for amblyopia, visual acuity had not improved in these cases. Four patients showed nystagmus. Four had progression of unilateral cataract. In two cases, a 24-year-old women and a 4-months-old boy, a vitreous haemorrhage had occurred due to rupture of a hyaloid artery, in the woman's case probably due to a spontaneous posterior vitreous detachment. CONCLUSION: A persistent hyaloid artery may be associated with strabismus, cataract, amblyopia and nystagmus. Despite amblyopia treatment, the prognosis of visual acuity of the involved eye is unfavourable. A persistent hyaloid artery may cause vitreous haemorrhage.