Diet composition of an invasive population of Lithobates catesbeianus (American Bullfrog) from Argentina

The American bullfrog Lithobates catesbeianus has been introduced around the world, with invasive populations reported from almost all South American countries. A population of this species was introduced in the Calingasta department of San Juan province, which is an arid environment in western Argentina. This work provides information on the dietary composition of an invasive population of L. catesbeianus, and compares the degree of dietary overlap between adults and juveniles. Stomach contents of 169 bullfrogs (82 adults and 87 juveniles) were analysed. Adults consumed 40 prey taxa and Hymenoptera (Insecta) was the most numerous prey item (41.8%), followed by Araneae (13.6%) and Aeglidae (13.4%). Juveniles consumed 29 prey taxa and Hymenoptera constituted the highest percentage in prey number (77.2%). The trophic overlap niche index at the same level shows a value of 0.64 overlap in dietary community between adults and juveniles of this bullfrog. Aeglidae was volumetrically the most important trophic item (25.4%), followed by Anura (25.02%). Our results showed that cannibalism in bullfrogs is more common than the consumption of native anurans, coinciding with that reported in other populations of introduced bullfrogs. The high similarity in the diets of both size classes and the association between the size of the predator and prey suggest that the impact caused by bullfrogs throughout their ontogeny is high and probably has an impact on their prey. Freshwater crabs are the main items in the diet of Lithobates catesbeianus in other introduced populations and are usually the most conspicuous at our study site. The crabs in freshwater ecosystems are part of the lowest trophic level in the food chain. The major threats to the southern region’s freshwater crabs include deforestation, farming and exotic species. Lithobates catesbeianus has a generalist diet and high overlap between adults and juveniles.     

Non-invasive genetic study and population monitoring of the brown bear (Ursus arctos) (Mammalia: Ursidae) in Kastoria region – Greece

The brown bear (Ursus arctos) in Greece is considered endangered but little is known about the genetic status and the exact size of local populations. Non-invasive genetic sampling was used in this study to investigate the genetic diversity and genetic structure of the brown bear population in the Kastoria region (northwest Macedonia, Greece) and to estimate its population size. Estimation of demographic parameters was based on innovative, well-evaluated methods that can provide estimates from a single sampling session. DNA was extracted from hairs, scat and blood samples and subsequent amplification of 10 microsatellite loci allowed the identification of a minimum number of 75 living bears in the study area while the mark–recapture-based analysis resulted in a point estimation of 219 individuals. Relatively high diversity values, lack of heterozygosity deficiency as well as estimated effective population size, support the Kastoria bear population having good conservation status.     

浅析河南省城市化的制约因素及对策

从人口流动机制、产业基础、基础设施建设、相关制度安排等方面,探讨了制约河南省城市化水平提高的不利因素,并对其的改进对策和措施进行了论述。     

Natural history of the marsupial Thylamys macrurus (Mammalia,Didelphidae) in fragments of savannah in southwestern Brazil

The objective of this study was to furnish information on the natural history of the Neotropical marsupial Thylamys macrurus in the southern Cerrado of Brazil. A range expansion of the species was observed to the northeast of the Mato Grosso do Sul state, Brazil. Specimens were surveyed in fragments of savannah (40–600 ha) during dry and wet seasons in 2003 and 2004 with live‐trap grids and pitfall lines. With an effort of 9767 trap nights and 2200 pitfall nights, we obtained 102 captures and 49 recaptures of T. macrurus. The data analyzed (57 males and 40 females) showed that males are more abundant in the dry season and females in the wet season. Young were recorded mostly during the wet season. Thylamys macrurus was scansorial, using the floor and the understorey. Sexual dimorphism was recorded, with males being larger than females. Information on ectoparasites is supplied.     

种群细胞增生中迁移方程的研究进展

介绍了近年来国际上种群细胞增生中的迁移方程的研究进展,主要阐述了这类迁移方程解的构造性理论及应用等研究成果。     

井冈山区常绿阔叶林更新的发展动态分析

本文从常绿阔叶林更新苗的分析和生态因子的研究入手,并通过对更新苗种群和区系特征的分析,初步揭示了在井冈山区,恢复和发展以热带—亚热带区系植物为主要类成分的常绿阔叶林的可能性。     

有限总体U-统计量正态逼近的非一致性界限(Ⅱ)(英文)

本文建立了有限总体U-统计量正态逼近的非一致性界限。本文分成两部分。在部分(Ⅰ),我们对有限总体抽样的部分和建立了一个类似的结果和六个引理(见本刊1989,Vol.19,No.1,PP.25-37)。在这一部分,即部分(Ⅱ),我们将完成关于有限总体U-统计量的这一定理的证明。     

内蒙古民族人口发展模型

对内蒙古的蒙古族、汉族以及达斡尔族、鄂温克族和鄂伦春族人口发展模型、发展特点和蒙古族、汉族人口未来发展预测模型进行了研究和探讨。     

带泵浦的光双稳系统的激光阈值条件

本文将光学双稳性的强迫振动模型加以推广,研究了带泵浦的光学双稳系统(OBP)在粒子数反转条件下的稳态运转,包括自持振荡和带入射信号系统的光放大过程。首先给出了无入射驱动系统的一般激光条件。进而揭示并讨论了带入射信号系统光放大输出的增益阈值及其变化规律,同时发现了系统失谐与光放大条件和频率牵引效应的关系。