Seven microsatellite loci from 176 female specimens of the oligolectic desert bee, Macrotera portalis, were analyzed to detect population subdivision among eight geographically distinct localities (17 to 342 km apart) across southwestern New Mexico and southeastern Arizona. In spite of the absence of obvious geographic barriers to gene flow, genie and genotypic frequencies revealed significant genetic heterogeneity among localities. F statistics revealed a high level of inbreeding within populations (F i s = 0.3241, P < 0.001), as well as substantial differentiation among localities (F s t = 0.2037, P < 0.001). A significant correlation was detected between distance among populations and the level of gene flow. Various factors may contribute to the low level of gene flow observed among populations, including narrow host-plant specificity, specificity in soil composition, habitat specificity, and the existence of large-headed, flightless males that mate within the nests. Five microsatellites from 192 male and female Macrotera portalis (Timberlake) reared from nests were analyzed in order to estimate intra-nest relatedness. Relatedness among female nestmates was significantly greater than zero for two of seven nests. Our results have implications for understanding patterns of bee diversity.
Abstract Meiotic drive occurs when a selfish element increases its transmission frequency above the Mendelian ratio by hijacking the asymmetric divisions of female meiosis. Meiotic drive causes genomic conflict and potentially has a major impact on genome evolution, but only a few drive loci of large effect have been described. New methods to reliably detect meiotic drive are therefore needed, particularly for discovering moderate-strength drivers that are likely to be more prevalent in natural populations than strong drivers. Here we report an efficient method that uses sequencing of large pools of backcross (BC1) progeny to test for deviations from Mendelian segregation genome-wide of single-nucleotide polymorphisms (SNPs) that distinguish the parental strains. We show that meiotic drive can be detected by a characteristic pattern of decay in distortion of SNP frequencies, caused by recombination unlinking the driver from distal loci. We further show that control crosses allow allele-frequency distortion caused by meiotic drive to be distinguished from distortion resulting from developmental effects. We used this approach to test whether chromosomes with extreme telomere-length differences segregate at Mendelian ratios, as telomeric regions are a potential hotspot for meiotic drive due to their roles in meiotic segregation and multiple observations of high rates of telomere sequence evolution. Using four different pairings of long and short telomere strains, we find no evidence that extreme telomere-length variation causes meiotic drive in Drosophila. However, we identify one candidate meiotic driver in a centromere-linked region that shows an ~8% increase in transmission frequency, corresponding to a ~54:46 segregation ratio. Our results show that candidate meiotic drivers of moderate strength can be readily detected and localized in pools of F1 progeny.
Objective
To assess the gastric contents before cesarean section using antral cross-sectional area(CSA)measured by ultrasonography.
Methods
One hundred and seventy-seven American Society of Anesthesiologists physical status I-III patients, aged 20-44 yr, undergoing cesarean section, were enrolled in this study.The antral CSA in the semi-recumbent and right lateral decubitus positions was measured through the ultrasound images of the antrum in the sagittal plane below xiphoid before anesthesia and qualitatively graded.Qualitative grade 0 was considered as the gold standard, and the receiver operating characteristic(ROC)curve of CSA in assessing the preoperative gastric contents was plotted.
Results
The critical value of ROC curve of CSA in the semi-recumbent position was 6.025 cm2.The critical value of ROC curve of CSA in the right lateral decubitus position was 9.095 cm2.
Conclusion
CSA<6.025 cm2 measured by ultrasonography in the semi-recumbent position or CSA<9.095 cm2 measured by ultrasonography in the right lateral decubitus position can confirm that the gastric emptying state is achieved before cesarean section.
Key words:
Cesarean section; Gastrointestinal contents; Ultrasonography; Antral cross-sectional area
We performed a phylogenetic analysis of the species, species groups, and subgenera within the predominantly eusocial lineage of Lasioglossum (the Hemihalictus series) based on three protein coding genes: mitochondrial cytochrome oxidase I, nuclear elongation factor 1alpha and long-wavelength rhodopsin. The entire data set consisted of 3421 aligned nucleotide sites, 854 of which were parsimony informative. Analyses by equal weights parsimony, maximum likelihood, and Bayesian methods yielded good resolution among the 53 taxa/populations, with strong bootstrap support and high posterior probabilities for most nodes. There was no significant incongruence among genes, and parsimony, maximum likelihood, and Bayesian methods yielded congruent results. We mapped social behavior onto the resulting tree for 42 of the taxa/populations to infer the likely history of social evolution within Lasioglossum. Our results indicate that eusociality had a single origin within Lasioglossum. Within the predominantly eusocial clade, however, there have been multiple (six) reversals from eusociality to solitary nesting, social polymorphism, or social parasitism, suggesting that these reversals may be more common in primitively eusocial Hymenoptera than previously anticipated. Our results support the view that eusociality is hard to evolve but easily lost. This conclusion is potentially important for understanding the early evolution of the advanced eusocial insects, such as ants, termites, and corbiculate bees.
Hybrid incompatibilities (HIs) cause reproductive isolation between species and thus contribute to speciation. Several HI genes encode adaptively evolving proteins that localize to or interact with heterochromatin, suggesting that HIs may result from co-evolution with rapidly evolving heterochromatic DNA. Little is known, however, about the intraspecific function of these HI genes, the specific sequences they interact with, or the evolutionary forces that drive their divergence. The genes Hmr and Lhr genetically interact to cause hybrid lethality between Drosophila melanogaster and D. simulans, yet mutations in both genes are viable. Here, we report that Hmr and Lhr encode proteins that form a heterochromatic complex with Heterochromatin Protein 1 (HP1a). Using RNA-Seq analyses we discovered that Hmr and Lhr are required to repress transcripts from satellite DNAs and many families of transposable elements (TEs). By comparing Hmr and Lhr function between D. melanogaster and D. simulans we identify several satellite DNAs and TEs that are differentially regulated between the species. Hmr and Lhr mutations also cause massive overexpression of telomeric TEs and significant telomere lengthening. Hmr and Lhr therefore regulate three types of heterochromatic sequences that are responsible for the significant differences in genome size and structure between D. melanogaster and D. simulans and have high potential to cause genetic conflicts with host fitness. We further find that many TEs are overexpressed in hybrids but that those specifically mis-expressed in lethal hybrids do not closely correlate with Hmr function. Our results therefore argue that adaptive divergence of heterochromatin proteins in response to repetitive DNAs is an important underlying force driving the evolution of hybrid incompatibility genes, but that hybrid lethality likely results from novel epistatic genetic interactions that are distinct to the hybrid background.
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