Cryptic species are prevalent among mammals, and identifying morphological methods or measurements that can effectively distinguish cryptic species has high significance in taxonomy. Three of the white-bellied rats, Niviventer confucianus, N. fulvescens and N. huang (Rodentia: Muridae), have such similar morphological characteristics that taxonomists have not been able to effectively identify them according to their morphologies. Recent studies have determined that the N. fulvescens species complex contains multiple species, indicating that previous morphological comparisons were potentially based on inaccurate species identifications, leading to false conclusions. To clarify whether the morphological differences among these three species can be used for identification, a variety of morphological methods and measurements were combined with molecular species identification to ensure accurate identifications prior to comparing morphological characteristics. The results showed that: (1) only N. confucianus has a white tail tip, distinguishing this species from the other two species but not N. fulvescens from N. huang; and (2) the tail length of N. fulvescens and ear length of N. confucianus are greater than those of the other species. Traditional morphological methods cannot differentiate these species well, with the discrimination rate reaching more than 90%; therefore, they can only be used as auxiliary methods for morphological identification. Additionally: (3) the geometric morphological results of the four skull views can be combined to distinguish the three species, among which the discrimination rate of lateral view of mandible reaches 98%, making it effective for differentiating these species; and (4) the phallic morphologies of the three species differed significantly in the presence of a dorsal groove, thickness of the distal baculum, and the positional relationship between the distal and proximal baccula; thus, this approach can completely distinguish these species. This study examines the applicability of various morphological measurements for the identification of highly morphologically similar species, provides a reference for distinguishing cryptic species produced by convergent evolution or incomplete differentiation by morphology, and suggests that phallic morphology should be the primary characteristic for differentiating such species in the future.
ABSTRACT Although most shorebirds exhibit deferred migration and deferred breeding during their first summer, Dunlins (Calidris alpina) migrate to breeding areas and breed during their first summer. First‐year and adult Dunlins should, therefore, have similar fueling and molt patterns if energetic and physiological constraints are responsible for deferred migration. From 2006 to 2008, we examined the age structure of Dunlins during the nonbreeding season at Chongming Dongtan, an estuarine wetland in the Yangtze River estuary in east China, and examined the effects of date, age, and molt status on fuel deposition during migration and during the winter. The Dunlin population at Chongming Dongtan was composed primarily of first‐year birds. Most adults and first‐year birds arrived together in late August. Regression analyses indicated that age, date, and molt status affected fuel deposition (as indicated by body mass) of Dunlins. Adults had significantly greater fuel deposits than first‐year Dunlins near the end of northward migration (May: adults 70.8 ± 6.4 g, first‐year 63.8 ± 8.0 g) and at the start of southward migration (September: adults 50.2 ± 6.1 g, first‐year 47.2 ± 4.9 g). Adults also had significantly higher fuel deposition rates than first‐year Dunlins during northward migration. Nonetheless, first‐year Dunlins migrate and breed in their first summer. Thus, other factors, such as migration distance and body size, may be more important in determining if first‐year shorebirds defer migration during their first spring and summer. During boreal spring and autumn, first‐year Dunlins in active body molt had greater body mass than those that had not initiated body molt or those in suspended molt, and premigratory fuel deposits for northward migration were greatest after prealternate molt was completed. These results suggest that body molt requires additional fuel deposits and imposes a constraint on fuel deposition for migratory flights. 相似文献
The field dependence of relaxation times of the C-1 carbon of glycogen was studied in vitro by natural-abundance 13C NMR. T1 is strongly field dependent, while T2 does not change significantly with magnetic field. T1 and T2 were also measured for rat hepatic glycogen enriched with [1-13C]glucose in vivo at 4.7 T, and similar relaxation times were observed as those obtained in vitro at the same field. The in vitro values of T1 were 65 +/- 5 ms at 2.1 T, 142 +/- 10 ms at 4.7 T, and 300 +/- 10 ms at 8.4 T, while T2 values were 6.7 +/- 1 ms at 2.1 T, 9.4 +/- 1 ms at 4.7 T, and 9.5 +/- 1 ms at 8.4 T. Calculations based on the rigid-rotor nearest-neighbor model give qualitatively good agreement with the T1 field dependence with a best-fit correlation time of 6.4 X 10(-9) s, which is significantly smaller than tau M, the estimated overall correlation time for the glycogen molecule (ca. 10(-5) s). A more accurate fit of T1 data using a modified Lipari and Szabo approach indicates that internal fast motions dominate the T1 relaxation in glycogen. On the other hand, the T2 relaxation is dominated by the overall correlation time tau M while the internal motions are almost but not completely unrestricted. 相似文献