基于GIS和Maxent模型的赤水河地区濒危植物桫椤生境适宜性评价

桫椤有"蕨类植物之王"赞誉,有"活化石"之称,曾是地球上最繁盛的植物,与恐龙同期。由于地质变迁和气候变化,目前只能在极少数的"避难所"才能寻其踪迹,而赤水河地区是当下桫椤种群较为集中分布的区域。所以,了解桫椤在赤水河地区的适生区分布,对于桫椤种质资源保护、桫椤种群的恢复重建具有重要意义。基于桫椤在赤水河流域的80个桫椤分布点位、20个样地信息和22个环境因子变量,借助ArcGIS运用Maxent模型软件预测了桫椤的潜在地理分布,综合环境因子变量贡献率、刀切法检验和土地利用现状变化对赤水河地区桫椤的生境适宜性进行评价分析,确定桫椤的生境适宜潜在地理分布区域和面积。研究表明：（1）Maxent模型的预测准确度极高,模型的预测结果为"极好";（2）最暖季的降水（39.65%）、温度日平均范围（18.21%）、温度季节性变化标准差（12.69%）和降水量季节性变异性系数（6.87%）是影响桫椤生长和分布的主导环境因子,累积贡献率达77.42%,可见桫椤在生长过程中对降水、温度的变化较为敏感;（3）模型预测高适生区主要集中在四川（泸州、宜宾、自贡）、重庆、贵州（遵义）,在空间上存在明显连续性,从高适生区到不适生区呈辐射状由中心向外围逐渐递减;虽桫椤高适生区面积高达49842 km²,但现状生境破碎化,人为干扰,人工植被较多等的影响会对桫椤种群造成不利影响。综上,赤水河地区桫椤适生生境面积大、连通性好,为本地区的桫椤提供了优质的生存环境,森林的人工抚育可促进桫椤种群的延续。     

Comparison of the extent of genetic variation of Vallisneria natans and its sympatric congener V. spinulosa in lakes of the middle-lower reaches of the Yangtze River

Vallisneria natans and Vallisneria spinulosa are two morphologically very similar and sympatrically dominant submerged macrophytes in lakes of the middle-lower reaches of the Yangtze River. Genetic variation was compared based on a total of 196 individuals from six V. natans populations and 201 individuals from seven V. spinulosa populations. Using eight ISSR primers, a total of 139 and 129 DNA fragments were generated with 121 being polymorphic in V. natans and 99 in V. spinulosa. The two species maintained higher genetic variation both at the species and population levels in comparison with other aquatic macrophytes. A higher level of genetic diversity among populations was found in V. natans than in V. spinulosa: the percentage of polymorphic loci (PPL) in V. natans was 52-62% vs. 38-47% in V. spinulosa; gene diversity (H) was 0.21 in V. natans vs. 0.17 in V. spinulosa.Both an analysis of molecular variance (AMOVA) and F-estimation (F_ST) showed that most of the total genetic variation resided within populations of both species (AMOVA: 85% and 80%; F_ST: 0.132 and 0.202), indicating low genetic differentiation between populations. Principal coordinates analysis (PCA) indicated evident gene flow between populations of both species. The outcrossing reproductive mode and pervasive gene flow might have played important roles in maintaining high genetic diversity and in shaping low population differentiation of the two Vallisneria species, while the extent of clonal growth might account for the different levels of population divergence between them.     

毛竹扩张对濒危植物桫椤根系形态可塑性的影响

为探讨毛竹(Phyllostachys heterocycla)向桫椤(Alsophila spinulosa)林扩张的根系形态可塑性变化,在赤水桫椤国家级自然保护区毛竹-桫椤混交林上分别设置受毛竹轻度、中度以及重度干扰的样地,用根钻法收集桫椤、毛竹根系并对其生物量密度、细根比根长、相邻同级侧根节点距等参数进行比对。结果表明:各干扰程度下桫椤根系生物量密度均远低于毛竹,且二者呈负相关;随着与毛竹的接近,桫椤根系生物量持续下降;各样地中毛竹细根比根长均高于桫椤;重度干扰下毛竹侧根节点距最小,侧根数目最多;且毛竹根系多分布于表层土壤。由此可见,桫椤根系逐渐趋向于分布在深层土壤,毛竹在向桫椤林扩张过程中可通过改变根系生物量密度、细根比根长、相邻同级侧根节点距等形态可塑性特征来占据优势。     

New microsatellite markers for the bush rat,Rattus fuscipes greyii: characterization and cross‐species amplification

We describe here 16 new microsatellite markers for the bush rat, Rattus fuscipes greyii, and characterize their cross‐species amplification within the Australian Rattus and at a greater level of divergence in Rattus rattus and Rattus norvegicus. Within R. f. greyii, all of the loci are highly polymorphic, with six to 24 alleles per locus across the species range and expected heterozygosity ranging from 0.48 to 0.90 per locus within a sample of 24 rats from a large population on Kangaroo Island. Cross‐species amplification rates were approximately 87% within the Australian Rattus and approximately 50% within R. rattus and R. norvegicus. These loci are highly polymorphic with a high success rate of cross‐species amplification, making them potentially useful for a wide range of genetic studies.     

Asexual life history by quadriflagellate swarmers of Ulva spinulosa (Ulvales, Ulvophyceae)

This is the first report of a Ulva species reproducing asexually solely by quadriflagellate swarmers. Ulva spinulosa Okamura et Segawa specimens were collected from Ukibuchi on the Pacific coast of Kochi Prefecture, southern Japan. Quadriflagellate swarmers were released from these specimens. The swarmers showed negative phototaxis before settlement. Thalli cultured from these swarmers also released quadriflagellate swarmers in culture. Microspectrophotometric studies demonstrated equivalent DNA in nuclei of vegetative cells in thalli of U. spinulosa and in sporo‐phytes of the other Ulva species with sexual life history (U. fasciata Delile). Furthermore, the quadriflagellate swarmers of U. spinulosa had the same DNA value, demonstrating that the quadriflagellate swarmers are produced without meiosis.     

Isolation and characterization of microsatellite loci in the Caribbean gorgonian Pseudopterogorgia elisabethae

We report on the isolation and characterization of five polymorphic microsatellites in the gorgonian Pseudopterogorgia elisabethae from genomic DNA‐enriched libraries. Forty‐four microsatellites were screened from the libraries with the oligonucleotide probe (CA)₁₂. Five of the screened microsatellites were polymorphic. The levels of polymorphism found in 50 genotyped individuals from a single population suggest that microsatellites are useful tools for the study of genetic variation in gorgonians. These are the first microsatellite loci reported from any gorgonian species.     

Characterization of novel microsatellite loci for red clover (Trifolium pratense L.) from enriched genomic libraries

Twenty‐seven polymorphic microsatellite markers were isolated from red clover (Trifolium pratense). Allelic variability and cross‐species amplification were assessed on 24 red clover and eight white clover (Trifolium repens) genotypes. The number of alleles detected in red clover ranged from two to 25. Observed and expected heterozygosities were high with average values of 0.71 and 0.88, respectively. Five of the 27 loci were also successfully amplified from white clover, where two to 13 alleles were detected. These highly polymorphic microsatellite loci provide powerful tools for population genetic studies as well as for marker‐assisted selection in this important forage legume species.     

Isolation and characterization of trinucleotide microsatellites in African malaria mosquito Anopheles funestus

We developed microsatellite markers for an important African malaria mosquito Anopheles funestus Giles. The microsatellite‐enriched genomic library was constructed and screened with single‐strand oligonucleotides [(CCT)₁₇, (AAT)₁₇, (CAG)₁₇ and (GA)₂₅] as probes. Among the 47 pairs of polymerase chain reaction primers screened, 31 produced successful and consistent amplification. Although only a few A. funestus individuals from one geographical location were used to screen microsatellite marker polymorphism, 27 markers were found polymorphic and four markers monomorphic. Most polymorphic markers are trinucleotide markers. Isolation of polymorphic microsatellite markers provide useful tools for A. funestus population genetic studies and genome mapping.     

Isolation and characterization of polymorphic microsatellite loci for the study of paternity and population structure in the little penguin Eudyptula minor

We isolated and characterized eight novel microsatellite loci in the little penguin Eudyptula minor, using nonradioactive polymerase chain reaction‐based techniques to screen GA and GAAA repeats from enriched genomic DNA libraries. All eight loci were polymorphic and seven were variable in our main study population (mean H_E = 0.613, mean N_A = 7.14). Cross‐amplification using a microsatellite primer developed in Spheniscus demersus (African penguin) yielded one additional polymorphic locus. This locus combined with six of the little penguin loci is suitable for paternity assignment in little penguins (exclusion probability for seven unlinked loci = 0.993).     

New microsatellite loci for the European bushcricket,Ephippiger ephippiger (Orthoptera: Tettigoniidae)

Ephippiger ephippiger is a model organism for studies of sexual selection and phylogeography but little is known about fine‐scale population structure. Available microsatellite loci have null allele problems so we used an enrichment technique to isolate 21 new microsatellite loci for E. ephippiger. We present primer pairs for 10 polymorphic loci (3–11 alleles per locus). Observed heterozygosities at polymorphic loci ranged from 0.118 to 0.787, but several were significantly lower than expected.     

PERMANENT GENETIC RESOURCES: A set of 12 microsatellite loci for genetic studies of Leishmania braziliensis

Twelve microsatellite loci of Leishmania braziliensis were examined, nine of which were developed in this work. Fifty‐six Leishmania braziliensis were genotyped with these microsatellite loci. The 12 loci studied were polymorphic with the number of alleles ranging from five to 19, with a mean of 9.7 ± 4.1 and the observed heterozygosity averaging 0.425 ± 0.202. The important heterozygote deficits we observed (F_IS = 0.41, P value = 0.004) appear incompatible with the heterozygote excess expected in clonal diploids. This last result could revive the clonality/sexuality debate regarding Leishmania. This work validates the potential use of these microsatellites for population genetics analysis.     

Isolation and variability of polymorphic microsatellite loci in Aedes aegypti,the vector of dengue viruses

We isolated five microsatellite sequences from an enriched‐(CAA)_n library of 5000 recombinant clones in Aedes aegypti. Two polymorphic microsatellites from our library and four from other sequence databases were tested: we investigated their polymorphism and Mendelian inheritance in mosquito populations. Our results indicate that trinucleotide repeat markers could be used to differentiate Ae. aegypti populations, making them valuable tools for the study of population genetic structure.     

Isolation of polymorphic DNA microsatellites in the common sole Solea vulgaris

A microsatellite‐enriched genomic library was obtained from the common sole, Solea vulgaris, and seven polymorphic dinucleotide markers were successfully optimized. These markers showed levels of expected heterozygosity ranging from 0.55 to 0.83 and allele number ranging from eight to 12. Three of these markers were also found to successfully amplify in the closely related Solea senegalensis and can be employed to define population genetic structure of the two Solea species and for inferring stock origins.     

Development and characterization of six new microsatellite markers for the silver‐ or gold‐lipped pearl oyster,Pinctada maxima (Pteriidae)

Six di‐, tri‐ and tetranucleotide microsatellite loci were developed for the silver‐ or gold‐lipped pearl oyster Pinctada maxima using a linker‐ligated, magnetic bead enrichment protocol. Based on a minimum of 134 Indonesian pearl oyster samples, number of alleles and observed heterozygosity at each locus ranged from six to 17 alleles and from 0.172 to 0.813 (mean = 0.448), respectively. Mean polymorphic information content for the six loci was 0.562. These loci should be very useful in DNA parentage analyses and population differentiation of P. maxima in Australia and Indonesia.     

Low genetic diversity and local adaptive divergence of Dracaena cambodiana (Liliaceae) populations associated with historical population bottlenecks and natural selection: an endangered long‐lived tree endemic to Hainan Island,China

Historical population bottlenecks and natural selection have important effects on the current genetic diversity and structure of long‐lived trees. Dracaena cambodiana is an endangered, long‐lived tree endemic to Hainan Island, China. Our field investigations showed that only 10 populations remain on Hainan Island and that almost all have been seriously isolated and grow in distinct habitats. A considerable amount of genetic variation at the species level, but little variation at the population level, and a high level of genetic differentiation among the populations with limited gene flow in D. cambodiana were detected using inter‐simple sequence repeat (ISSR) and random amplified polymorphic DNA (RAPD) analyses. No significant correlation was found between genetic diversity and actual population size, as the genetic diversities were similar regardless of population size. The Mantel test revealed that there was no correlation between genetic and geographic distances among the 10 populations. The UPGMA, PCoA and Bayesian analyses showed that local adaptive divergence has occurred among the D. cambodiana populations, which was further supported by habitat‐private fragments. We suggest that the current genetic diversity and population differentiation of D. cambodiana resulted from historical population bottlenecks and natural selection followed by historical isolation. However, the lack of natural regeneration of D. cambodiana indicates that former local adaptations with low genetic diversity may have been genetically weak and are unable to adapt to the current ecological environments.     

Advances in assessing Sabellaria spinulosa reefs for ongoing monitoring

Standardized and repeatable data acquisition and analyses are required to enable the mapping and condition monitoring of reefs within Marine Protected Areas (MPAs). Changes in habitat condition must be reliably identified and reported to best support evidence‐based management. Biogenic reefs in temperate waters, that is, hard matter created by living organisms and raised above the seabed, provide food and shelter for many plant and animal species. This article explores the feasibility of habitat mapping, using remote sensing datasets, as well as metrics for repeatable and suitable assessment of areas of Sabellaria spinulosa for their status as biogenic reef. Data were gathered within the North Norfolk Sandbanks and Saturn Reef candidate Special Area of Conservation/Site of Community Importance in the southern North Sea. Six study areas were identified as potential locations of biogenic reef using previously acquired data, and these were targeted for further investigation using a combination of high resolution multibeam echosounder and sidescan sonar. Where potential S. spinulosa was identified from the acoustic data, a drop‐down camera system was employed for visual verification. Areas of known and potential S. spinulosa reef were mapped successfully at two of the six study areas, although future approaches should take careful consideration of the seabed morphology and predominant habitat backdrop to successfully interpret such data. Camera tows from S. spinulosa reef areas were broken up into 5‐s segments, with each segment scored for (a) average tube elevation; (b) average percentage cover; and (c) for the presence or absence of S. spinulosa. These metrics were utilized to create summary statistics, including a value of patchiness derived from presence/absence data, that is recommended for application as part of future monitoring programs. The application of this methodology could benefit wider assessments of similar threated or declining habitats such as intertidal Mytilus edulis beds on mixed and sandy sediments, Maerl beds, Modioulus modiolus beds, Ostrea edulis beds, and Zostera beds where patchiness may also be considered of environmental importance.     

Isolation and characterization of microsatellite markers in Dendrobium officinale,an endangered herb endemic to China

As an invaluable herb, Dendrobium officinale has been in severe danger since 1950 because of human exploitation and habitat deterioration. In order to investigate the genetic diversity and structure of this species, we isolated and characterized 12 microsatellite loci derived from two microsatellite‐enriched libraries. Twenty‐two individuals from Leye population were analysed. These loci were polymorphic and displayed three to 12 alleles per locus. The observed and expected heterozygosities ranged from 0.150 to 0.624 and from 0.162 to 0.605, respectively. These are the first microsatellite loci characterized from D. officinale that will contribute to research on the conservation, genetic diversity, population structure and individual authentication.     

毛竹-桫椤群丛的种间关系与群落稳定性

种间关系是植物群落重要的数量与结构特征之一,直接影响群落的稳定性,探究种间关系与群落稳定性对于植物种群的保护和稳定性维持具有重要意义。以贵州省赤水桫椤国家级自然保护区内的桫椤群落为研究对象,采用样方法对桫椤(Alsophila spinulosa)群落进行调查,分析植物总体关联性、种间相关性并计算群落的稳定性系数。结果表明,毛竹(Phyllostachys edulis)在群落中占绝对优势,毛竹与桫椤的种间关系表现为显著正相关;桫椤在发育前期受到物种间的影响较大,而在发育的后期处于相对独立的状态,与物种间的关系表现为弱相关或不相关,受到物种间的影响较小;贡献定律法分析表明毛竹-桫椤群落的稳定性系数为21/79,说明金沙沟区域的毛竹-桫椤群落处于稳定状态。     

Isolation and characterization of microsatellite markers for Sabatia campestris (Gentianaceae), an Illinois state‐endangered plant

Sabatia campestris is a regionally endangered prairie plant. Eight polymorphic loci have been generated for S. campestris (Gentianaceae) using non‐enriched and enriched libraries. Polymorphism was quantified from an isolated population from central Illinois yielding mean observed and expected heterozygosities of 0.723 and 0.801, respectively. The number of alleles per locus for this population ranged from three to 25 with a median of 15.5. These genetic markers will be used to determine population genetic structure of Illinois populations as well as to estimate fine‐scale gene flow rates.     

Microsatellite loci in the stable fly,Stomoxys niger niger (Diptera: Muscidae) on La Réunion Island

Six polymorphic microsatellite markers have been isolated from a microsatellite‐enriched DNA library from the stable fly, Stomoxys niger niger. These loci exhibited five to 10 alleles per locus and an expected heterozygosity ranging from 0.57 to 0.81 in the studied populations from La Réunion Island (Indian Ocean). They should therefore be useful for the study of genetic diversity and population structure of S. niger. In addition, cross‐species amplification of four of these six loci in the closely allied species Stomoxys calcitrans produced interpretable results, two of which would be useful for population biology studies.