Spectral regions in which aquatic insects see reflected polarized light

For diverse water insects (species of Hydrophilidae, Hadraenidae, Dytiscidae, Haliplidae and aquatic Heteroptera), the attractiveness of an artificial water surface was found to vary when the polarization of the reflected light, the property by which these insects identify water, was abolished in different regions of the spectrum. The sensitivity maxima of their reflection-polarization visual systems (max(POL)) thus determined were in various spectral regions, between < 360 nm (UV) and ca. 550 nm (yellow-green). Species with max(POL) at the short-wavelength end of the spectrum would be able to identify bodies of water by polarization regardless of whether the subsurface reflection was bright or dark; nevertheless, this group includes forms that avoid water with a bright subsurface because of the intensity of the reflected light. Species with max(POL) in the long-wavelength region fail to use certain bodies of water with a bright subsurface as habitats because the light they reflect at the longer wavelengths is insufficiently polarized. That the POL system of a species has a large max could affect habitat choice; on the other hand, it could also be that systems operating in the long-wavelength region were produced in the course of adaptation to the light conditions in or above the habitat.Abbreviations max(POL) spectral sensitivity maximum for polarization vision     

Spatial separation of fishes captured in passive gear in a turbid prairie lake

Synopsis Spatial separation of fishes in the littoral zone of a turbid prairie lake (Clear Lake, Iowa) was assessed with gill nets and fyke nets. Catch per unit of effort was used to determine differences among habitat types, sampling times within a 24 h period, and sampling months. Four of 10 species examined were significantly more numerous in one of the three habitats — nonvegetated, vegetated, or gravel-rock substrate. Black bullhead (Ictalurus melas) and bigmouth buffalo (Ictiobus cyprinellus) were most abundant in vegetated areas, yellow bass (Morone mississippiensis) in gravel-rock areas, and channel catfish (Ictalurus punctatus) in both non-vegetated and gravel-rock areas. Temporal patterns in habitat use were indicated for these four species, as well as yellow perch (Perca flavescens), white bass (Morone chrysops), common carp (Cyprinus carpio), walleye (Stizostedion vitreum vitreum), black crappie (Pomoxis nigromaculatus), white sucker (Catostomus commersoni). Journal Paper No. J-11039 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 2345. Financed by the U.S. Department of the Interior Office of Water Research and Technology and Iowa State University.     

A new genus and two new species of gobiid fishes (Perciformes) from the Chagos Archipelago,Central Indian Ocean

Synopsis A recent (1979) expedition to the Chagos Archipelago resulted in the collection of about 40 new taxa of fishes. A new genus,Trimmatom, and two new species,T. nanus andT. offucius, are described here. The new genus is characterized by having all pelvic-fin rays simple (unbranched), a scaleless body, no head pores, a wide gill opening extending anteroventrally to below the eye, and hypurals 1 and 2 fused to the complex formed by the fusion of the ural centrum and hypurals 3 and 4.T. nanuss andT. offucius are differentiated on the basis of fin ray counts and colour pattern.T. nanus is the smallest vertebrate yet to be described. Mature females with ovaries full of eggs are 8–10 mm in standard length.     

Crucial factors determining the spatio-temporal distribution patterns of threeAthalia sawflies feeding on common cruciferous plants

Three Athalia sawflies, A. japonica, A. rosae and A. infumata, feeding on cruciferous plants, coexist in Japan. However, it is not known what ecological strategies they use and what environmental factors are crucial to such strategies. I attempted to explain these questions by examining the relationship between the spatio-temporal distribution patterns of three Athalia sawflies and their habitats in three districts (Lowland, Intermediate and Mountain). The three sawflies have different spatio-temporal distribution patterns, though they usually used common cruciferous plants. A. japonica was abundant in spring and autumn but disappeared during summer in all the districts. In the Lowland, populations of A. rosae and A. infumata, like that of A. japonica, crashed in summer. However A. rosae occurred mainly in summer in the Intermediate and Mountain. Although A. infumata occurred in the same seasons as A. rosae in all districts, population levels of A. infumata were always lower than those of A. rosae. The crucial factors controlling their population patterns were the availability of host plants and temperature. Population crashes of A. rosae and A. infumata were due to food depletion, and those of A. japonica were due to heat stress. On the other hand, their population patterns may be interpreted as phenological synchronization with their original host plants, though they all existed on common cruciferous plants. The three sawflies may have evolved different strategies to escape from unfavorable habitat conditions. Such strategies are speculated to be summer diapause in A. japonica, long distance migration in A. rosae, and local dispersal in A. infumata.     

山地景观遗传学研究文献综述

山地生态系统是生物多样性分布与保护的热点。山地景观遗传学（Mountain Landscape Genetics）研究在山地景观尺度上野生生物的种群遗传格局及其驱动机制和影响因素,是景观遗传学（Landscape Genetics）的重要分支。山地景观遗传学研究对于深入理解物种的空间遗传结构、形成过程、物种形成与分化机制具有重要意义与价值,同时可以为珍稀濒危物种和山地生物多样性的有效保护与管理提供科学指导。为了更好地掌握目前山地景观遗传学的发展趋势与重点研究问题,为未来生物多样性与山地生态系统的保护管理提供科学参考,基于对Web of Science核心数据库和中国知网数据库的系统检索,全面汇总分析了1999-2020年山地景观遗传学领域发表的192篇英文文献与31篇中文文献。结果显示,该领域自2008年起迅速发展,截至2020年共有46个国家的研究机构发表了山地景观遗传相关研究,研究热点地区包括北美洲的落基山脉、内华达山脉、阿巴拉契亚山脉,欧洲的阿尔卑斯山脉、比利牛斯山脉,以及亚洲的喜马拉雅-横断山脉。研究对象类群涵盖真菌、植物、节肢动物、脊椎动物,其中脊椎动物是研究发表最多的类群,占发表文献总数的62.0%;脊椎动物中,又以对哺乳类（占脊椎动物发表文献总数的52.9%）与两栖类（23.5%）的研究最多。目前主要的研究方向包括：（1）识别山地景观中的基因流路径或阻碍;（2）量化山地景观特征对种群遗传结构时空变化的影响。中国是发表山地景观遗传学文章数量最多的亚洲国家,近十年来相关研究发展迅速,研究类群以植物（占在中国发表文献总数的62.3%）与脊椎动物（35.8%）为主,对脊椎动物的研究中以两栖动物为最多（占所有脊椎动物发文数量的52.6%）,研究区域主要集中在喜马拉雅-横断山脉与秦岭。本文进一步对目前山地景观遗传学研究中存在的空缺及未来重点关注问题提出建议。     

Habitat richness affects home range size in the red fox Vulpes vulpes

The spatial behaviour of the red fox Vulpes vulpes shows a great flexibility (Voigt and Macdonald, 1984). Home range size varies from 10 to over 5000 ha (Macdonald, 1987; Voigt, 1987). In carnivores, variations in home range size, weighed for body mass (Gittleman and Harvey, 1982), are largely related to differences in habitat productivity, but the intraspecific local variation in home range size can be only partially explained by differences in productivity. Macdonald (1981, 1983) suggested that home range size and configuration were determined in the red fox by the dispersion of food-rich patches. More recently, it has been found that

1.

(a) where humans are intolerant to the fox, resting sites are often located peripherally in home ranges (Meia and Weber, 1993);     

Comparing movement of four butterfly species in experimental grassland strips

In contrast to many studies on the habitat quality of road verges for butterflies in relation to management regimes, little is known about whether road verges also function as corridors linking fragmented grassland habitats. We experimentally compared movements of four model species, two small blues and two medium browns, with one habitat specialist and one habitat generalist in each size and phylogenetic category. A total of 425 individual butterflies were caught and translocated to an experimental arena with three 2 × 30 m grassland strips that approximated road verges; one with adult feeding resources, one sheltered from the wind, and one without food and shelter. Movements in grassland strips were compared to movements in continuous grassland habitat. Results indicated that (1) individuals did not use the low-quality strip, (2) only specialists used strips but not in the same way according to their size and phylogenic category, and (3) strip use could not be predicted from habitat selection. This finding supports the idea that corridors of intermediate quality are the most efficient to promote dispersal rates in fragmented landscapes. Road verges cover 250,000 ha in Sweden, which is nearly the total amount of seminatural grasslands. Our results suggest that, to benefit butterfly dispersal among grassland patches, road verges should be managed to create a more favourable microclimate (e.g. sheltered from wind, high temperatures).     

Rapid changes in fish utilization of mangrove habitat in Western Madagascar

Fish use of a mangrove habitat was studied in a small mangrove forest on the West coast of Madagascar. A sand bar near the inlet retains water in parts of the channel (pools) at low tide. Fishes in four of these pools were examined daily at all phases of the tidal cycle for 3 weeks using underwater visual census. During week 1, fishes were diverse and abundant in all pools: the dominant species were cardinalfish (related to Apogon lateralis); monos, Monodactylus argenteus; black spotted snappers, Lutjanus ehrenbergi; double bar bream, Acanthopagrus bifasciatus; emperors, Lethrinus lentjan and L. sp., surgeon fish, Acanthurus nigricauda; red-lined sweetlips, Plectorhinchus plagiodesmis; and butterflyfish, Chaetodon kleini. Some species were more abundant in shaded pools; others in more open pools. During week 2 a dramatic difference was noted: the only fishes found were schools of cardinalfish and one moray eel. This week had neap tides, with high tides in the morning and low tides in the afternoon. As the week progressed and during week 3 (spring tides), fishes slowly repopulated the habitat and diversity increased. Monos, absent in week 2, now had increasing numbers of small individuals. While large emperors were scarce, small individuals appeared. The larger butterflyfish and surgeonfish seen in week 1 were replaced by small ones during week 3. Species that had been rare in week 1 were more abundant, including pipefish and small barracudas. While species richness increased during week 3, the community was strikingly different from that seen 2 weeks earlier. Only Pool 1, closest to the entrance, recovered its original species richness. Abundance was much lower than in week 1. Our snapshot study apparently captured a time when older juveniles left the mangrove forest and smaller fishes recruited into it. Utilization of this habitat will likely vary throughout the year depending on the reproductive cycle of the different species whose juveniles utilize it. Longer studies are needed to learn about cycles in fish use of the mangroves.     

Differences in root architecture influence attraction of fishes to mangroves: A field experiment mimicking roots of different length, orientation, and complexity

Benthic structure plays an important role as shelter and feeding habitat for demersal fauna. While many studies have investigated the relationship between structural complexity of aquatic vegetation and the number of species or abundance of motile organisms, little is known of the attractiveness of submerged mangrove roots. We tested the importance of various root attributes in attracting fish species in a field experiment using different artificial mangrove units (AMUs) with PVC pipes mimicking roots to exclude interaction with other environmental and biotic factors. We manipulated length, vertical orientation, and three-dimensional structural complexity of root mimics in the AMUs to explore their effects on the fish community variables: fish abundance, number of species and community composition. Pipe length and three-dimensional structure did not have an effect on fish community variables. Vertical pipe orientation had a significant effect and AMUs with standing pipes showed higher total fish abundances and number of species than AMUs with hanging pipes. Also community composition differed greatly between AMUs with standing versus hanging pipes. At species level, demersal fish species mainly occupied AMUs with standing pipes and occurred only at very low abundances when hanging pipes dominated in the AMUs; in contrast, the semi-pelagic swimmer Sphyraena barracuda showed a trend of higher abundance in AMUs with mainly hanging pipes. When analyzed across all AMUs, fish abundances of demersal as well as semi-pelagic species decreased significantly with increasing interspatial pipe distance among AMUs, suggesting that distance to refuge may be the underlying mechanism for the observed patterns. The above findings are important in the context of the worldwide degradation of mangroves, because human alteration to mangrove vegetation affects its structure and thus composition and size of fish communities.     

稀有鮈鲫对不同生境的选择性偏好

对不同生境的识别和选择性偏好是保障鱼类生存和繁衍的重要能力之一。以稀有鮈鲫（Gobiocypris rarus）为研究对象,使用沙、水草和石块在观测水缸中进行多种排列组合以构建不同的生境类型,基于在各区域的停留时长和中线跨越次数两项参数,测试稀有鮈鲫对不同生境类型的偏好以及营养状态、生境组成物数量、环境照度对该行为影响。结果表明,稀有鮈鲫对不同的生境类型具有明显的选择性偏好,对仅水草生境偏好程度最高,对仅石块生境的偏好程度最低。该偏好行为在24 h的禁食后变化不显著（P > 0.05）,但生境组成物数量和环境照度对该行为具有显著影响（P < 0.05）,其偏好程度随水草数量和照度的增加而增加,在包含8棵水草及1 000 lx的照度下最高。