Genomic Determination of Reproductive Mode in Facultatively Parthenogenetic Opiliones.

Sexual reproduction may pose myriad short-term costs to females. Despite these costs, sexual reproduction is near ubiquitous. Facultative parthenogenesis is theorized to mitigate some of the costs of sex, as individuals can participate in occasional sex to limit costs while obtaining many benefits. However, most theoretical models assume sexual reproduction is fixed following mating, with no possibility of clutches of mixed reproductive ontogeny. Therefore, we asked: if coercive males are present at high frequency in a population of facultative parthenogens, will their clutches be solely sexually produced, or will there be evidence of sexually and asexually-produced offspring? How will their offspring production compare to conspecifics in low-frequency male populations? We addressed our questions by collecting females and egg clutches of the facultatively parthenogenetic Opiliones species Leiobunum manubriatum and L. globosum. In L. manubriatum, females from populations with few males were not significantly more fecund than females from populations with higher male relative frequency, despite the potential release of the former from sexual conflict. We used 3 genotyping methods along with a custom set of DNA capture probes to reveal that offspring of L. manubriatum from these high male populations were primarily produced via asexual reproduction. This is surprising because sex ratios in these southern populations approach equality, increasing the probability for females to encounter mates and produce offspring sexually. We additionally found evidence for reproductive polymorphisms within populations. Rapid and accurate SNP genotyping data will continue to allow us to address broader evolutionary questions regarding the role of facultative reproductive modes in the maintenance of sex.

Magnetic Resonance Imaging in Acute Ischemic Stroke Patients with Mild Symptoms: An Opportunity to Standardize Intravenous Thrombolysis.

BACKGROUND: Patients presenting with mild stroke symptoms are excluded inconsistently from intravenous (IV) thrombolysis. We aimed to compare acute magnetic resonance imaging findings in patients with mild symptoms to those with more severe deficits to identify clinically mild patients who might benefit from IV thrombolysis. METHODS: We retrospectively studied consecutive stroke patients presenting with perfusion deficit who underwent time-of-flight magnetic resonance angiography within 24 hours of time last seen normal. Two raters measured the lesion volumes on diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) with mismatch (MM) calculated as PWI minus DWI. Occlusion site was categorized as "proximal," "distal," or "magnetic resonance angiography-negative" by consensus review. Stroke with mild symptoms was defined as admit National Institutes of Health Stroke Scale score of 4 or less. Values were reported as n (%). RESULTS: Ninety-one patients were included; 56 (61.5%) with nonmild and 35 (38.5%) with mild symptoms. After stratifying for occlusion site, there were no differences in PWI and MM lesion volumes for the nonmild versus mild patients (P = .34-.98 and P = .54-1, respectively). Furthermore, there was a trend for thrombolyzed mild stroke patients (88%, n = 7 of 8) to more likely have a favorable clinical outcome (discharge modified Rankin score ≤ 2) versus untreated patients (70%, n = 16 of 23). CONCLUSIONS: When present, conspicuous vessel occlusions in clinically mild stroke patients are concomitant with similar perfusion deficit and MM volumes in more clinically severe stroke patients. Coupled with a trend toward better outcomes in mild stroke patients who were treated with IV tissue plasminogen activator (t-PA), this could indicate that advanced imaging may be used in standardizing the way these patients are selected for IV t-PA therapy.