How sea level change mediates genetic divergence in coastal species across regions with varying tectonic and sediment processes.

Plate tectonics and sediment processes control regional continental shelf topography. We examine the genetic consequences of how glacial-associated sea level change interacted with variable nearshore topography since the last glaciation. We reconstructed the size and distribution of areas suitable for tidal estuary formation from the last glacial maximum, ~20 thousand years ago, to present from San Francisco, California, USA (~38°N) to Reforma, Sinaloa, Mexico (~25°N). We assessed range-wide genetic structure and diversity of three codistributed tidal estuarine fishes (California Killifish, Shadow Goby, Longjaw Mudsucker) along ~4,600 km using mitochondrial control region and cytB sequence, and 16-20 microsatellite loci from a total of 524 individuals. Results show that glacial-associated sea level change limited estuarine habitat to few, widely separated refugia at glacial lowstand, and present-day genetic clades were sourced from specific refugia. Habitat increased during postglacial sea level rise and refugial populations admixed in newly formed habitats. Continental shelves with active tectonics and/or low sediment supply were steep and hosted fewer, smaller refugia with more genetically differentiated populations than on broader shelves. Approximate Bayesian computation favoured the refuge-recolonization scenarios from habitat models over isolation by distance and seaway alternatives, indicating isolation at lowstand is a major diversification mechanism among these estuarine (and perhaps other) coastal species. Because sea level change is a global phenomenon, we suggest this top-down physical control of extirpation-isolation-recolonization may be an important driver of genetic diversification in coastal taxa inhabiting other topographically complex coasts globally during the Mid- to Late Pleistocene and deeper timescales.

Sea-level driven glacial-age refugia and post-glacial mixing on subtropical coasts, a palaeohabitat and genetic study.

Using a novel combination of palaeohabitat modelling and genetic mixture analyses, we identify and assess a sea-level-driven recolonization process following the Last Glacial Maximum (LGM). Our palaeohabitat modelling reveals dramatic changes in estuarine habitat distribution along the coast of California (USA) and Baja California (Mexico). At the LGM (approx. 20 kya), when sea level was approximately 130 m lower, the palaeo-shoreline was too steep for tidal estuarine habitat formation, eliminating this habitat type from regions where it is currently most abundant, and limiting such estuaries to a northern and a southern refugium separated by 1000 km. We assess the recolonization of estuaries formed during post-LGM sea-level rise through examination of refugium-associated alleles and approximate Bayesian computation in three species of estuarine fishes. Results reveal sourcing of modern populations from both refugia, which admix in the newly formed habitat between the refuges. We infer a dramatic peak in habitat area between 15 and 10 kya with subsequent decline. Overall, this approach revealed a previously undocumented dynamic and integrated relationship between sea-level change, coastal processes and population genetics. These results extend glacial refugial dynamics to unglaciated subtropical coasts and have significant implications for biotic response to predicted sea-level rise.

A Relative Resistance Ratio for Evaluation of Mexican Rice Borer (Lepidoptera: Crambidae) Susceptibility Among Sugarcane Cultivars.

The Mexican rice borer, Eoreuma loftini (Dyar), is a major pest of sugarcane (hybrids of Saccharum spp.) in Louisiana and Texas. Resistance to E. loftini was evaluated in 51 commercial and experimental cultivars of sugarcane, energycane (hybrids of Saccharum spp.), and sorghum [Sorghum bicolor (L.) Moench and hybrids of Sorghum spp.] in four replicated small plot field experiments from 2009 to 2012. A relative resistance ratio was developed to compare levels of susceptibility among cultivars based on the percentage of bored internodes and survival to adulthood. This index was able to separate cultivars into five resistance categories and provides a new method for comparing levels of resistance among cultivars. E. loftini pest pressure in 2009 was among the highest recorded with injury ranging from 55 to 88% bored internodes. Commercial sugarcane cultivar HoCP 85-845 was identified as resistant in three of four experiments, whereas HoCP 04-838 was identified as susceptible in all experiments. Of the five sugarcane cultivars in commercial production in the Rio Grande Valley of Texas, only TCP 87-3388 was categorized as resistant. Of the cultivars with potential for bioenergy production, all of the energycane cultivars demonstrated higher levels of resistance than high-biomass and sweet sorghum cultivars. Continued evaluation of cultivar resistance to E. loftini is important to development of effective integrated pest management strategies for this pest.

Accuracy of central venous pressure monitoring in the intraabdominal inferior vena cava: a canine study.

STUDY OBJECTIVE: To test the hypotheses that in multiple pathophysiologic settings (1) end-expiratory central venous pressure measurements in the intraabdominal inferior vena cava accurately reflect those in the superior vena cava and (2) mean central venous pressure monitoring is as reliable in the inferior vena cava as it is in the superior vena cava. DESIGN: Simultaneous inferior vena caval and superior vena caval pressures were measured during five ventilatory phases: apnea, end-expiratory mechanical ventilation, maximal inspiratory mechanical ventilation, end-expiratory spontaneous ventilation, and maximal inspiratory spontaneous ventilation. Measurements were repeated after progressive intravascular volume depletion. SUBJECTS: Eight puppies. MEASUREMENTS AND RESULTS: Simultaneous inferior vena caval and superior vena caval end-expiratory pressures did not differ significantly (mean differences 0 to 0.1 mm Hg) and the limits of agreement of these measurements were within 2 mm Hg. Differences between mean maximal inspiratory pressures in the inferior vena cava and superior vena cava during mechanical and spontaneous ventilation were -0.7 and 3.6 mm Hg, respectively (p less than 0.01), and the limits of agreement extended beyond 2 mm Hg. Furthermore, mean maximal inspiratory pressures in the superior vena cava differed from end-expiratory pressures in the superior vena cava (1.1 and -3.6 mm Hg, p less than 0.01), whereas those in the inferior vena cava did not differ from end-expiratory superior vena caval pressures. CONCLUSIONS: Under the experimental conditions studied (1) end-expiratory intraabdominal inferior vena caval pressures accurately reflected end-expiratory superior vena caval pressures and (2) mean central venous pressure monitoring was as reliable in the inferior vena cava as in the superior vena cava.

Effect of intralipid on the neonatal pulmonary bed: an echographic study.

The effect of Intralipid infusion on pulmonary vascular resistance was studied prospectively by serial echocardiography on 13 occasions in six low birth weight infants. After 90 minutes of Intralipid infusion, the ratio of right ventricular preejection period to ejection time (RVPEP/ET) rose from 0.232 +/- 0.025 (mean +/- SD) to 0.285 +/- 0.035 (P = 0.0001). Of the 13 infusions studied, six (43%) resulted in RVPEP/ET values suggestive of pulmonary hypertension. Six LBW infants were observed over the same time period without Intralipid infusion, and RVPEP/ET did not change (0.209 +/- 0.035 vs 0.194 +/- 0.024). The increase in RVPEP/ET with Intralipid administration could not be explained by differences in preload or contractility, and most likely reflects an increase in pulmonary vascular tone. Caution in the use of Intralipid is recommended in infants who would be at particular risk from increased pulmonary vascular resistance.