Deleterious effects by mosquitofish (Gambusia affinis) on the endangered fire salamander (Salamandra infraimmaculata)

Invasive fishes, via competition and predation, may be an important factor in endangering populations of amphibians and other aquatic fauna. The mosquitofish, Gambusia affinis , commonly stocked into amphibian breeding sites for mosquito control worldwide, has recently been found in some breeding sites of the endangered fire salamander Salamandra infraimmaculata in northern Israel. A comparison of Salamandra larvae in natural pools varying in Gambusia densities suggested that Gambusia negatively affects Salamandra by causing damage to its appendages, in particular, its tailfin (as manifested in a smaller tail:body ratio). Comparison of the same pool before and after mosquitofish introduction suggested strong negative effects on larval performance and number of emerging metamorphs. To explicitly test the hypothesis that Gambusia negatively affects Salamandra larval development, growth and survival, we conducted a replicated outdoor mesocosm experiment. In this experiment, we also tested how habitat structural complexity, in the form of radiating cords simulating artificial vegetation, might mediate damage caused by Gambusia . We used a two-by-two factorial design: the presence or absence of increased structural complexity crossed with the presence or absence of mosquitofish. After a short period, mosquitofish strongly reduced larval wet weight and survival, and increased body damage in the form of a reduced larval tail:body ratio and partially missing gills and limbs. No Salamandra larvae exposed to mosquitofish survived to metamorphosis in either habitat type. We conclude that Gambusia strongly and negatively affects Salamandra larvae and that the introduction of Gambusia into sites containing Salamandra is inconsistent with the goal of preserving this endangered urodele.     

Rampant drift in artificially fragmented populations of the endangered tidewater goby (Eucyclogobius newberryi)

Habitat fragmentation and its genetic consequences are a critically important issue in evaluating the evolutionary penalties of human habitat modification. Here, we examine the genetic structure and diversity in naturally subdivided and artificially fragmented populations of the endangered tidewater goby (Eucyclogobius newberryi), a small fish restricted to discrete coastal lagoons and estuaries in California, USA. We use five naturally fragmented coastal populations from a 300‐ km spatial scale as a standard to assess migration and drift relative to eight artificially fragmented bay populations from a 30‐ km spatial scale. Using nine microsatellite loci in 621 individuals, and a 522‐base fragment of mitochondrial DNA control region from 103 individuals, we found striking differences in the relative influences of migration and drift on genetic variation at these two scales. Overall, the artificially fragmented populations exhibited a consistent pattern of higher genetic differentiation and significantly lower genetic diversity relative to the naturally fragmented populations. Thus, even in a species characterized by habitat isolation and subdivision, further artificial fragmentation appears to result in substantial population genetic consequences and may not be sustainable.     

鹅掌楸贵州烂木山居群的微卫星遗传多样性及空间遗传结构

濒危植物鹅掌楸(Liriodendron chinense)目前仅零散分布于我国亚热带及越南北部地区, 残存居群生境片断化较为严重。研究濒危植物片断化居群的遗传多样性及小尺度空间遗传结构(spatial genetic structure)有助于了解物种的生态进化过程以及制定相关的保育策略。本研究采用13对微卫星引物, 对鹅掌楸的1个片断化居群进行了遗传多样性及空间遗传结构的研究, 旨在揭示生境片断化条件下鹅掌楸的遗传多样性及基因流状况。研究结果表明: 鹅掌楸烂木山居群内不同生境斑块及不同年龄阶段植株的遗传多样性水平差异不显著(P>0.05), 居群内存在寨内和山林2个遗传分化明显的亚居群。烂木山居群个体在200 m以内呈现显著的空间遗传结构, 而2个亚居群内的个体仅在20 m的距离范围内存在微弱或不显著的空间遗传结构。鹅掌楸的空间遗传结构强度较低(Sp = 0.0090), 且寨内亚居群的空间遗传结构强度(Sp = 0.0067)要高于山林亚居群(Sp = 0.0053)。鹅掌楸以异交为主, 种子较轻且具翅, 借助风力传播, 在一定程度上降低了空间遗传结构的强度。此外, 居群内个体密度及生境特征也对鹅掌楸的空间遗传结构产生了一定影响。该居群出现显著的杂合子缺失, 近交系数(F_IS)为0.099 (P < 0.01), 表明生境片断化的遗传效应正逐渐显现。因此, 对鹅掌楸的就地保护应注意维护与强化生境的连续性, 促进基因交流。迁地保护时, 取样距离应不小于20 m, 以涵盖足够多的遗传变异。     

气候变化背景下秦岭地区羚牛生境脆弱性评估及适应性保护对策

脆弱性是指物种受气候变化影响的程度,开展脆弱性评估工作有助于人类认识气候变化对野生动物的影响,为制定野生动物适应气候变化的保护对策提供科学依据。采用最大熵模型评估气候变化背景下秦岭地区羚牛(Budorcas taxicolor bedfordi)生境脆弱性。结果表明：(1)当前秦岭地区羚牛适宜生境总面积为6473 km²,到2050s年,预测秦岭地区羚牛适宜生境总面积为4217 km²,减少34.85%,羚牛适宜生境将向更高海拔地区转移,转移约210 m;(2)已建保护区覆盖49.82%当前羚牛适宜生境,尚有3248 km²的适宜生境处于保护区之外;到2050s年,保护区覆盖了43.87%适宜生境,尚有2367 km²的适宜生境未被保护;(3)到2050s年,当前分布在太白县、佛坪县、洋县和宁陕县等地区的3490 km²羚牛适宜生境将会成为生境脆弱区域,丧失53.92%;(4)分布在秦岭核心区域的2983 km²当前和2050s年保持不变适宜生境,将成为羚...     

Ecology of spawning humpback chub, Gila cypha, in the Little Colorado River near Grand Canyon, Arizona

The morphologically unique and endangered humpback chub, Gila cypha, is found in canyon-bound reaches of the Colorado River and its tributaries. Now limited to six isolated reproducing populations, this species is believed to have been once distributed over a large portion of the mainstem river. Because the species inhabits remote canyon areas, little is known about its spawning ecology. The largest remaining population occurs in the lower Little Colorado River (LCR) near Grand Canyon, where we conducted a three-year study of spawning ecology during spring (March-June) 1993–1995. We analyzed seasonal patterns of movement, population density, relative condition, spawning scores, and frequency of ripe condition and fin abrasions and compared these data with seasonal discharge and water temperature to determine spawning phenology and ecology. Spawning commenced in late March, peaked in mid-April, and waned in mid-May. A high proportion of males remained ripe over this period, whereas ripe females were relatively abundant only in April. Increased densities of adult fish in March-April and rapid declines in May-June coupled with recaptures of 18.4% of these adults in the Colorado River suggest that a portion of the population migrated from the Colorado River into the LCR to spawn and then returned. Ripe males aggregated in areas of complex habitat structure with high angular variation in bottom profiles (matrix of large boulders, travertine masses combined with chutes, runs and eddies, 0.5–2.0 m deep) and were associated with deposits of clean gravel. Ripe females appeared to move to these male aggregations to spawn. Near-spawning (including gravid) females and non-spawning fish used similar habitats and were segregated but close (< 50 m) to habitats occupied by aggregations of ripe males. Abrasions on anal and lower caudal fins of males and females suggest that spawning involves contact with gravel substrates, where semi-adhesive eggs are deposited and fertilized. The findings of this study should aid recovery efforts for humpback chub by identifying spawning habitat within the historic distributional range where additional spawning stocks could be established.     

破碎景观建立保护区面积-数量模式界定

由于生境丧失日益严重,很难找到一片未被破坏的生境建立自然保护区,因而在设计保护区时,必须处理生境丧失带来的影响。在一个已经遭受过生境丧失的景观上,选取一片正方形的区域,并调整区域的面积以保证其中未被破坏生境的面积为一个固定常数,探讨将未被破坏的生境建设成大量小保护区还是少量大保护区。结果表明:(1)随机的生境丧失下,生境丧失比例越高,少量大保护区模式的优势越明显。(2)即使生境丧失比例恒定,被破坏生境的空间分布形式也有重要影响——被破坏生境的空间聚集程度越高,大量小保护区模式的优势越明显。(3)增加扩散率或降低扩散死亡率可导致从少量大保护区更有利于物种到大量小保护区更有利的转变,且被破坏生境的聚集程度越高,转变的程度越高。以上结论为自然保护区设计提供了理论依据。     

Biodiversity and the Heterogeneous Disturbance Regime on Military Training Lands

Disproportionately large numbers of threatened and endangered species and unusually high biodiversity occur on active and former military training areas. Although this may seem paradoxical given the apparently destructive nature of military training, an evaluation of the nature and extent of the disturbances is enlightening. Military training frequently produces heterogeneous landscapes. Large portions of military training areas remain virtually untouched, favoring disturbance‐averse species; other portions are heavily disturbed, favoring disturbance‐dependent species. The rich habitat mosaics include the two extremes as well as the continua of disturbance and succession between them, thus providing suitable habitat for a very large number of species with widely varying habitat requirements. To explain the phenomenon, a heterogeneous disturbance hypothesis is proposed which suggests that biodiversity is maximized where multiple kinds, frequencies, severities, periodicities, sizes, shapes, and/or durations of disturbance occur concomitantly on a landscape in a spatially and temporally distributed fashion. The enhanced biodiversity occurring on active and former military training areas illustrates the need for restoration ecologists to restore or maintain an appropriate heterogeneous disturbance regime when attempting to restore ecosystem function and biodiversity.     

Relation of desert pupfish abundance to selected environmental variables in natural and manmade habitats in the Salton Sea basin

Synopsis We assessed the relation between abundance of desert pupfish, Cyprinodon macularius, and selected biological and physicochemical variables in natural and manmade habitats within the Salton Sea Basin. Field sampling in a natural tributary, Salt Creek, and three agricultural drains captured eight species including pupfish (1.1% of the total catch), the only native species encountered. According to Bray–Curtis resemblance functions, fish species assemblages differed mostly between Salt Creek and the drains (i.e., the three drains had relatively similar species assemblages). Pupfish numbers and environmental variables varied among sites and sample periods. Canonical correlation showed that pupfish abundance was positively correlated with abundance of western mosquitofish, Gambusia affinis, and negatively correlated with abundance of porthole livebearers, Poeciliopsis gracilis, tilapias (Sarotherodon mossambica and Tilapia zillii), longjaw mudsuckers, Gillichthys mirabilis, and mollies (Poecilia latipinnaandPoecilia mexicana). In addition, pupfish abundance was positively correlated with cover, pH, and salinity, and negatively correlated with sediment factor (a measure of sediment grain size) and dissolved oxygen. Pupfish abundance was generally highest in habitats where water quality extremes (especially high pH and salinity, and low dissolved oxygen) seemingly limited the occurrence of nonnative fishes. This study also documented evidence of predation by mudsuckers on pupfish. These findings support the contention of many resource managers that pupfish populations are adversely influenced by ecological interactions with nonnative fishes.     

A possible case of hantavirus infection in a Borneo orangutan and its conservation implication

Background Natural infection of hantavirus in orangutans has never been reported. Methods Enzyme‐linked immunosorbent assays (ELISA), Indirect immunofluorescence assay (IFA), and RT‐PCR were used to diagnosis a suspected case in a pet orangutan in southern Taiwan. Results Although the RT‐PCR result was negative, the high IgG titer in the beginning and its dramatic drop after treatments suggested a recent Seoul‐type hantavirus infection. Conclusions Hantavirus transmission and its potential damage to wild orangutans should not be overlooked.