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1.
For both Mullus barbatus and M. surmuletus , the relationship between sagitta area (O), sulcus acusticus area (S) throughout postlarval growth was characterized by their negative allometric growth. The adjusted mean S: O ratio differed between the two species. This may be associated with the difference in size and shape of the sagittae, a difference in somatic growth, and differences in food and spatial niches. The inner ear of Mullus cannot be considered as specialized and the interaction of stimuli detected by the sensory barbels and the inner ear together could be a compensatory mechanism that helps in the food search.  相似文献   
2.
Disturbances and ecosystem recovery from disturbance both involve numerous processes that operate on multiple spatial and temporal scales. Few studies have investigated how gradients of disturbance intensity and ecosystem responses are distributed across multiple spatial resolutions and also how this relationship changes through time during recovery. We investigated how cover of non-native species and soil-aggregate stability (a measure of vulnerability to erosion by water) in surface and subsurface soils varied spatially during grazing by burros and cattle and whether patterns in these variables changed after grazer removal from Mojave National Preserve, California, USA. We compared distance from water and number of ungulate defecations — metrics of longer-term and recent grazing intensity, respectively, — as predictors of our response variables. We used information-theoretic analyses to compare hierarchical linear models that accounted for important covariates and allowed for interannual variation in the disturbance–response relationship at local and landscape scales. Soil stability was greater under perennial vegetation than in bare interspaces, and surface soil stability decreased with increasing numbers of ungulate defecations. Stability of surface samples was more affected by time since removal of grazers than was stability of subsurface samples, and subsurface soil stability in bare spaces was not related to grazing intensity, time since removal, or any of our other predictors. In the high rainfall year (2003) after cattle had been removed for 1–2 years, cover of all non-native plants averaged nine times higher than in the low-rainfall year (2002). Given the heterogeneity in distribution of large-herbivore impacts that we observed at several resolutions, hierarchical analyses provided a more complete understanding of the spatial and temporal complexities of disturbance and recovery processes in arid ecosystems.  相似文献   
3.
The feeding habits of two sympatric species pairs of demersal fish ( Mullus barbatus-Mullus surmuletus, Serranus cabrilla-Serranus hepatus ) which occupy the shallow coastal area (25–30 m) in Iraklion Bay were investigated from samples collected on a monthly basis (August 1990 to August 1992). Stomach content analyses revealed that all of them were carnivores, feeding mainly on benthic invertebrates, and that each species consumed a narrow range of prey species with no significant dietary overlap. The morphology of their feeding apparatus was compared to examine the effect of any morphological differences on food selection and resource partitioning between the fish species. The species could be distinguished on the basis of the size of their mouth gape, the number of gill rakers and the length of their intestine. This study shows that each species pair follows a different strategy segregating along food niche dimensions. In particular, M. barbatus and M. surmuletus segregate their feeding niche consuming different prey taxa with similar sizes whereas S. cabrilla and S. hepatus differ considerably with respect to the degree to which prey species contribute to their diets coupled with differences in mean prey sizes.  相似文献   
4.
Bearded vulture populations in the Western Palearctic have experienced a severe decline during the last two centuries that has led to the near extinction of the species in Europe. In this study we analyse the sequence variation at the mitochondrial control region throughout the species range to infer its recent evolutionary history and to evaluate the current genetic status of the species. This study became possible through the extensive use of museum specimens to study populations now extinct. Phylogenetic analysis revealed the existence of two divergent mitochondrial lineages, lineage A occurring mainly in Western European populations and lineage B in African, Eastern European and Central Asian populations. The relative frequencies of haplotypes belonging to each lineage in the different populations show a steep East-West clinal distribution with maximal mixture of the two lineages in the Alps and Greece populations. A genealogical signature for population growth was found for lineage B, but not for lineage A; futhermore the Clade B haplotypes in western populations and clade A haplo-types in eastern populations are recently derived, as revealed by their peripheral location in median-joining haplotype networks. This phylogeographical pattern suggests allopatric differentiation of the two lineages in separate Mediterranean and African or Asian glacial refugia, followed by range expansion from the latter leading to two secondary contact suture zones in Central Europe and North Africa. High levels of among-population differentiation were observed, although these were not correlated with geographical distance. Due to the marked genetic structure, extinction of Central European populations in the last century re-sulted in the loss of a major portion of the genetic diversity of the species. We also found direct evidence for the effect of drift altering the genetic composition of the remnant Pyrenean population after the demographic bottleneck of the last century. Our results argue for the management of the species as a single population, given the apparent ecological exchangeability of extant stocks, and support the ongoing reintroduction of mixed ancestry birds in the Alps and planned reintroductions in Southern Spain.  相似文献   
5.
谢寅峰  杨万红  杨阳  蔡贤雷  周坚 《生态学报》2007,27(12):5193-5201
为了探讨外源一氧化氮对酸胁迫下植物生理响应的调节作用,以髯毛箬竹为试验材料,以硝普钠(SNP)为一氧化氮供体,研究了一氧化氮对模拟酸雨胁迫下叶片叶绿素相对含量、光合作用日变化以及叶绿素荧光特性等的影响。结果表明:(1)外源一氧化氮(50~450mg/LSNP)预处理可不同程度地缓解pH3.0酸雨胁迫下叶绿素含量的下降,其中以450mg/LSNP处理效果最明显;(2)酸雨胁迫下,箬竹叶片光合“午休”现象加重,日均净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)和气孔限制值(Ls)均明显降低,而细胞间隙CO2浓度(Ci)增大,经过外源SNP预处理后Pn、Gs、Tr和Ls不同程度增加,而Ci有所降低,以450mg/LSNP预处理的效果最好;(3)酸雨胁迫下,箬竹叶片的最大荧光(胁)、PSⅡ最大光化学效率(Fv/Fm)、有效光化学效率(Fv’/Fm’)、最大荧光产额(Fm’)、稳态荧光产额(Fs’)、光化学淬灭系数(qP)、非光化学淬灭系数(NPQ)、PSⅡ实际光化学效率(qbPSⅡ)及表观光合电子传递速率(ETR)均降低,而暗适应下最小荧光(F0)、光适应下最小荧光产额(F’0)则升高;经450mg/LSNP预处理后,上述荧光参数在胁迫下的变化均受到不同程度的抑制。可见,一氧化氮预处理能够不同程度地缓解酸雨胁迫下非气孔因素引起的箬竹叶片光合速率的下降以及对光合系统的破坏作用,提高胁迫下光合能力。光化学效率的提高和过剩光能的非光合耗散的增强可能是一氧化氮缓解胁迫对光合机构破坏的机制之一。  相似文献   
6.
The red harvester ant, Pogonomyrmex barbatus, is a monogynous, polyandrous species: each ant colony is founded by a single queen that has mated with one or more males. To study levels of polyandry within a colony, as well as relationships among colonies, we developed 10 polymorphic microsatellite loci for P. barbatus. With the number of alleles per locus ranging from 3 to 39, and expected heterozygosities of 0.58–0.95, these markers promise to be useful in the study of colony and population genetic structure.  相似文献   
7.
The genetic differentiation of striped red mullet (Mullus surmuletus) and red mullet (Mullus barbatus) was investigated in 6 Mediterranean populations of each species by means of restriction fragment length polymorphism analysis of mitochondrial DNA. Three segments amplified by polymerase chain reaction (control region, COI, and 12S–16S ribosomal RNA) were digested with 20 restriction endonucleases, revealing 71 haplotypes for M. surmuletus and 30 for M. barbatus. For the two species nucleotide diversity was equally distributed within and among populations, leading to N ST values of 0.545 and 0.500 for M. surmuletus and M. barbatus, respectively. However, intrapopulation and interpopulation genetic structuring appeared to be much higher for M. surmuletus than for M. barbatus (1.88% vs. 0.46% of mean intrapopulation nucleotide diversity; 1.94% vs. 0.47% of mean interpopulation nucleotide diversity; 0.055% vs. 0.002% of net interpopulation divergence). Furthermore, 81.69% of the haplotypes observed for M. surmuletus were unique, whereas 70.29% of M. barbatus individuals were grouped in 3 common haplotypes. Given that fishing pressure and population sizes are similar for both species, this differentiation could be attributed to differences in biological parameters and life histories between the two species, coupled with oceanographic conditions prevailing in the studied area. Received July 25, 2000; accepted December 29, 2000  相似文献   
8.
彭东  王亚丽  杨旭  肖宁 《动物学杂志》2021,56(6):882-890
洞鳅属(Troglonectes Zhang, Zhao & Tang 2016)鱼类为中国特有的小型洞穴淡水鱼类,主要分布在贵州和广西喀斯特地区的地下河流中。2018至2019年在贵州省荔波县境内进行洞穴生物多样性调查时采集到4号洞鳅属标本,经过形态比较,与弱须洞鳅(Troglonectes barbatus)相似;基于线粒体16S rRNA和Cyt b重建的系统发育树及遗传距离分析显示,4号洞鳅属标本与来自模式产地的弱须洞鳅高度支持聚为一支;利用Kimura双参数模型计算基于16S rRNA和Cyt b的遗传距离,这些标本与弱须洞鳅之间的遗传距离分别为0.4%和0.2%,小于洞鳅属物种之间的遗传距离(16S rRNA遗传距离为2.4%,Cyt b遗传距离为6.1%)。本次研究使用16S rRNA和Cyt b分子标记研究洞鳅属部分物种的系统发育关系和遗传距离。综合形态和分子系统发育分析结果,确定采集自贵州省荔波县小七孔景区的4号标本为隶属于鲤形目条鳅科洞鳅属的弱须洞鳅,系贵州省洞穴鱼类新记录种。  相似文献   
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