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Stochastic resonance is widely applied to detect weak signal in a strong noise background because it can enhance the signal-to-noise ratio (SNR). A weak single frequency signal detection method based on under-sampling stochastic resonance is proposed to solve the problem that traditional stochastic resonance can be only applied to deal with small parameter signals. Stochastic resonance is successfully expanded into the applications of the large parameter signals on the basis of scale-transformation and retrieve technology in the under-sampling stochastic resonance. Moreover, the algorithm overcomes the limit that signal frequency must be more than 50 times of the sampling frequency in the second sample algorithm. The model of weak signal detection based on under-sampling stochastic resonance is put forward. Finally, detecting the weak single frequency signal under SNR = -27 dB background by the method proposed in this paper is simulated. The result proves the validity of the method. The sampling frequency in the method is much less than that in the traditional methods and this is helpful to apply stochastic resonance in improving the performance of the Costas loop. [ABSTRACT FROM AUTHOR]

A new Gekko (subgenus Japonigekko) species, Gekkoalpinus sp. nov. , is described from the Jinsha River Basin in southwestern China, between the border of Mangkang County, Xizang Autonomous Region and Batang County, Sichuan Province, according to the integrative taxonomic results combining molecular data and morphological characters obtained from the type series comprising 11 specimens. Our molecular phylogeny inferred from the mitochondrial 16S and ND2 gene fragments indicated that this new species is most closely related to Gekkojinjiangensis , but a considerable amount of genetic divergence exists between them ( p -distance: 3.6%-4.1% ( 16S ) and 7.1%-9.1% ( ND2 )). The new species can be distinguished from its congeners via a combination of series morphological characters. The discovery of this new species marks the highest altitudinal range (2400 to 2542 m a.s.l.) recorded for the subgenus Japonigekko and also represents a new provincial record for the genus in Xizang Autonomous Region., Competing Interests: The authors have declared that no competing interests exist., (Shun Ma, Sheng-Chao Shi, Cheng Shen, Li-Ming Chang, Jian-Ping Jiang.)

Confused geographical structure of a population and mitonuclear discordance are shaped by a combination of rapid changes in population demographics and shifts in ecology. In this study, we generated a time-calibrated phylogeny of Scutiger boulengeri , an endemic Xizang alpine toad occurring in mountain streams on the Qinghai-Xizang (Tibet) Plateau (QTP). Based on three mitochondrial DNA (mtDNA) genes, eight clades were assigned to three deeply divergent lineages. Analysis of nuclear DNA (nuDNA) genes revealed three distinct clusters without geographic structure, indicating significantly high rates of gene flow. Coalescent theory framework analysis (approximate Bayesian computation model DIYABC and Migrate-N) suggested that divergence of the main intraspecific clusters was the result of hybridization after secondary contact in the Holocene around 0.59 million years ago (Ma). The ratio of mtDNA F ST (fixation index) to nuDNA F ST was 2.3, thus failing to show male-biased dispersal. Geographic cline analysis showed that a wide hybrid zone was initially established in southwestern China, without significant reproductive isolation but with strong introgression in S . boulengeri , suggesting high hybrid fitness. Furthermore, mtDNA genes exhibited isolation by distance (IBD) while nuDNA genes exhibited significant isolation by environment (IBE). Results suggested that mitonuclear discordance may have initially been caused by geographic isolation, followed by precipitation-mediated hybridization, producing a wide hybrid zone and geographic structure confusion of nuDNA genes in S . boulengeri . This study indicated that complicated historical processes may have led to specific genetic patterns, with a specific climate factor facilitating gene flow in the system.

A new species of the genus Megophrys from Zhejiang Province, China is described. Molecular phylogenetic analyses supported the new taxon as an independent clade nested into the Megophrys clade and sister to M. lishuiensis . The new species could be distinguished from its congeners by a combination of the following morphological characteristics: (1) small size (SVL 31.0-36.3 mm in male and 41.6 mm in female); (2) vomerine ridge present and vomerine teeth absent; (3) tongue not notched behind; (4) a small horn-like tubercle at the edge of each upper eyelid; (5) tympanum distinctly visible, rounded; (6) two metacarpal tubercles in hand; (7) relative finger lengths: II < I < IV < III; (8) toes with rudimentary webbing at bases; (9) heels overlapping when thighs are positioned at right angles to the body; (10) tibiotarsal articulation reaching tympanum to eye when leg stretched forward; (11) an internal single subgular vocal sac in male; (12) in breeding male, the nuptial pads with black nuptial spines on the dorsal bases of the first and second fingers., (Bin Wang, Yan-Qing Wu, Jun-Wei Peng, Sheng-Chao Shi, Ning-Ning Lu, Jun Wu.)