Feeding ecology and population delineation of south‐eastern Atlantic and south‐western Indian Ocean humpback whales using stable isotope analysis     

Shaena Montanari  Francine Kershaw  Howard C. Rosenbaum 《水产资源保护:海洋与淡水生态系统》2020,30(3):486-496

1. Population delineation is vital for effectively managing and protecting populations of all at‐risk species. Population boundaries of Southern Hemisphere humpback whales on their breeding and feeding grounds have not been fully resolved. A number of methods have been used to delineate breeding stocks of Southern Hemisphere humpbacks, but ecological characteristics determined via stable isotope analysis provide valuable information to contrast other data sources.
2. In this study, stable isotope analysis is used to investigate potential separation of humpback whale populations on Southern Hemisphere feeding grounds as evidenced by carbon and nitrogen isotope values in their skin as proxies of diet.
3. One hundred samples of whale skin obtained from biopsies in sampling localities off the coasts of Gabon, Mayotte (Mozambique Channel), and Madagascar were analysed for carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotope ratios. The results showed a statistically significant difference in the mean δ¹⁵N values for whales between the populations from Gabon and Madagascar (7.0 ± 0.1‰ and 7.6 ± 0.1‰), and Gabon and Mayotte (7.6 ± 0.1‰ and 7.2 ± 0.1‰), indicating that these breeding stocks are potentially visiting different areas of the feeding grounds outside of the breeding season.
4. The results from this study indicate that at least some breeding stocks may show fidelity to separate feeding areas and do not widely mix with individuals from other breeding stocks while feeding.

  相似文献   

Observation of Interference Between Two Bose Condensates     

MR Andrews  CG Townsend  H Miesner  DS Durfee  DM Kurn  W Ketterle 《Science (New York, N.Y.)》1997,275(5300):637-641

Interference between two freely expanding Bose-Einstein condensates has been observed. Two condensates separated by approximately 40 micrometers were created by evaporatively cooling sodium atoms in a double-well potential formed by magnetic and optical forces. High-contrast matter-wave interference fringes with a period of approximately 15 micrometers were observed after switching off the potential and letting the condensates expand for 40 milliseconds and overlap. This demonstrates that Bose condensed atoms are "laser-like"; that is, they are coherent and show long-range correlations. These results have direct implications for the atom laser and the Josephson effect for atoms.  相似文献   

Effects of Monomer Structure on Their Organization and Polymerization in a Smectic Liquid Crystal     

CA Guymon  EN Hoggan  NA Clark  TP Rieker  DM Walba  CN Bowman 《Science (New York, N.Y.)》1997,275(5296):57-59

Photopolymerizable diacrylate monomers dissolved in fluid-layer smectic A and smectic C liquid crystal (LC) hosts exhibited significant spatial segregation and orientation that depend strongly on monomer structure. Small, flexible monomers such as 1,6-hexanediol diacrylate (HDDA) oriented parallel to the smectic layers and intercalated, whereas rod-shaped mesogen-like monomers such as 1,4-di-(4-(6-acryloyloxyhexyloxy)benzoyloxy)-2-methylbenzene (C6M) oriented normal to the smectic layers and collected within them. Such spatial segregation caused by the smectic layering dramatically enhanced photopolymerization rates; for HDDA, termination rates were reduced, whereas for C6M, both the termination and propagation rates were increased. These polymerization precursor structures suggest novel materials-design paradigms for gel LCs and nanophase-separated polymer systems.  相似文献   

Role of Gene Interactions in Hybrid Speciation: Evidence from Ancient and Experimental Hybrids   总被引：6，自引：0，他引：6  

LH Rieseberg  B Sinervo  CR Linder  MC Ungerer  DM Arias 《Science (New York, N.Y.)》1996,272(5262):741-745

The origin of a new diploid species by means of hybridization requires the successful merger of differentiated parental species' genomes. To study this process, the genomic composition of three experimentally synthesized hybrid lineages was compared with that of an ancient hybrid species. The genomic composition of the synthesized and ancient hybrids was concordant (rs = 0.68, P < 0.0001), indicating that selection to a large extent governs hybrid species formation. Further, nonrandom rates of introgression and significant associations among unlinked markers in each of the three synthesized hybrid lineages imply that interactions between coadapted parental species' genes constrain the genomic composition of hybrid species.  相似文献   

Designing and evaluating risk-based surveillance systems: potential unwarranted effects of applying adjusted risk estimates     

Willeberg P  Nielsen LR  Salman M 《Preventive veterinary medicine》2012,105(3):185-194

Risk-based surveillance systems reveal occurrence of disease or infection in a sample of population units, which are selected on the basis of risk factors for the condition under study. The purpose of such systems for supporting practical animal disease policy formulations and management decisions are: A: to detect an emerging disease or infection, if it becomes introduced into a population; or B: to substantiate freedom from a condition in a population; or C: to detect cases and estimate the prevalence of an endemic condition in a population. In risk-based surveillance these aims should be met with prudent use of resources while maintaining acceptable system performance. High-risk category units are selected for testing by identification of the presence of specific high-risk factor(s), while disregarding other factors that might also influence the risk. On this basis we argue that the most applicable risk estimate for use in designing and evaluating a risk-based surveillance system would be a crude (unadjusted) relative risk, odds ratio or apparent prevalence. Risk estimates found in the published literature, however, are often the results of multivariable analyses implicitly adjusting the estimates for confounding from other risk factors. We describe some potential unintentional effects when using adjusted risk estimates in evaluating the efficacy and sensitivity of risk-based surveillance systems (SSe). In two examples, we quantify and compare the efficacy and SSe using adjusted and crude risk estimates. The examples use Danish surveillance data from previously published studies to evaluate systems aimed at risk-based detection of new cases of an endemic infection, i.e. Salmonella in dairy cattle herds (Example 1), and for substantiating the absence of a specific infection, i.e. Trichinella in the national slaughter pig population (Example 2), respectively.  相似文献