Breeding system of the annual Cruciferae, <Emphasis Type="Italic">Arabidopsis kamchatica</Emphasis> subsp. <Emphasis Type="Italic">kawasakiana</Emphasis>

The breeding system of an annual Cruciferae, Arabidopsis kamchatica subsp. kawasakiana, was studied in three natural populations. We applied four experimental treatments, open pollination, bagging, emasculation + bagging, and emasculation + hand-pollination + bagging. None of the emasculated flowers with bags produced fruits but we observed high fruit sets in the other three treatments. The results confirmed that A. kamchatica subsp. kawasakiana is a self-compatible, non-apomictic species that can produce seeds through auto-pollination. Considering the life cycle as an annual, increased reproductive assurance through auto-pollination should be critical for the maintenance of populations of A. kamchatica subsp. kawasakiana.     

Gene lineage analysis in populations ofHelianthus niveus andH. petiolaris (Asteraceae)

Helianthus petiolaris andH. niveus are polytypic species which are morphologically distinct at the periphery of their ranges but intergrade in areas of sympatry.Helianthus niveus includes both annual and perennial members, whereasH. petiolaris is strictly annual. Chloroplast DNA and nuclear ribosomal DNA restriction site data were used to reconstruct the evolutionary history of populations of the two species. Cladistic analyses reveal the following: (1) neither species is monophyletic; (2) the annual habit is derived once in this complex; and (3) the region of morphological intergradation appears to be primary in origin. The significance of interbreeding versus common descent in defining species concepts is discussed in relation to the above cladistic analyses.     

The mycorrhizal status of Welwitschia mirabilis

This is the first report of the mycorrhizal status of Welwitschia mirabilis, a gymnosperm endemic to the Namib Desert. Like all other gymnosperms except the Pinaceae and Gnetaceae, W. mirabilis is associated with vesicular-arbuscular mycorrhizal (VAM) fungi. Mycorrhizal colonization of roots and the diversity and abundance of VAM species were determined at seven sites. Six sites received annual rainfall of 0–100 mm, varying widely from year to year. The seventh site experienced more predictable annual rainfall of 150–200 mm. Perennial vegetation was sparse at the six low-rainfall sites. Dry annual grasses from previous rain events were present at only three of these six sites and mean mycorrhizal colonization levels of W. mirabilis at these three sites were as high as 18%. W. mirabilis was not mycorrhizal at sites where grasses were absent. The seventh site, receiving higher rainfall, supported small trees and annual grasses in addition to W. mirabilis. Mycorrhizal colonization levels of W. mirabilis at this site were significantly higher than at the other six sites, closely paralleling those of the surrounding annual grasses. The mycorrhizal flora of W. mirabilis consisted of four Glomus species. These taxa were not unique to W. mirabilis, having been found with Stipagrostis and Cladoraphis grasses throughout the Namib and Kalahari deserts.     

Distinctions betweenHordeum bulbosum andH. murinum s.l. in seed and herbarium collections

It is sometimes necessary to identify eitherH. bulbosum orH. murinum on the basis of the inflorescence or seeds alone. The majority of taxonomic keys use the presence of swollen basal culms for the former against the annual habit for the latter. Confusion is due to similarities in inflorescences and spikelet morphology. Lodicules which always persist and are present beside the fruit in a mature caryopsis, and other characters such as the awns of the lemmas of the lateral spikelets enable conclusive distinction.     

Differentiation of perennial and annual types due to habitat conditions in the wild riceOryza perennis

Populations of the common wild rice of AsiaO. rufipogon Griff. (=Oryza perennis Moench) were studied with regard to interrelations between life-history traits and habitat conditions. They showed a perennial-annual continuum and differed in reproductive allocation and many other traits. Perennial populations were found in deep swamps, while annual populations were in shallower, temporary swamps which were parched in the dry season. The perennial and annual types tended to be in association with other perennial and annual plants, respectively, suggesting their niche differentiation. Intermediate perennial-annual populations were in communities with a high species diversity. In one population, plants growing on the periphery of the swamp were of annual and those in deeper center were of perennial type. Another population seemed to be differentiated into an annual and an intermediate type in accordance with different degrees of habitat disturbance. The small genetic distances found between the sub-populations suggested their differentiation within a gene pool.Contribution from National Institute of Genetics, Japan, No. 1415.     

Notes on Quercus ilex L. in Liguria (NW Italy)

The climatic characteristics of the Liguria region have been outlined by means of raw data and derived indices (water balance related to potential evapotraspiration, Rivas-Martinez's index of mediterraneity and thermicity, De Martonne's index of dryness, and Emberger's pluviothermic quotient and index of summer dryness). Their interpretation suggests that Liguria is a boundary region between two different climatic areas: the Mediterranean and that of Central Europe.The distribution of Quercus ilex communities in Liguria have suffered the heavy consequences of human activity on the coastal belt of the region. There is, however, sufficient evidence to show that their presence is closely linked to climatic conditions. Quercus ilex communities are absent from the western coastal belt where the annual water balance is below –50 mm and high mean temperatures occur. They are also absent from marly limestone dominated areas where annual water balance is below 300 mm. Quercus ilex woods show a preference for water balance values between 0 and 600, with the better developed forests being found in central and eastern coastal Liguria.The Ligurian Quercus ilex woods are ascribed to Quercetum ilicis Br.-Bl. 1915. Given that the presence within their floristic composition of a group of species of Querco-Fagetea (more species in eastern stands, few in western ones) is an almost constant characteristic, the subass. fraxino-ostryetosum Mariotti 1984 can be retained for many of them. Quercus ilex is not present in the initial succession stages of Mediterranean Liguria vegetation. It can be found in later stages when the vegetation is more fully developed towards a maquis type structure. In this case it tends to become dominant and the community develops (if no fire or other human interference occurs) into a Quercus ilex forest. Frequently, this succession takes place under an old tree layer cover (generally Pinus sp.), a remanant of man's past management of the vegetation in the area.     

Distyly and incompatibility inVillarsia congestiflora (Menyanthaceae), with comparative remarks onV. capitata

The Western Australian annual of restricted distribution,Villarsia congestiflora, has distylous flowers and pollen-size heteromorphism. Results of a crossing program indicate that this species is strongly self-incompatible, that crosses among individuals of the same morph produce little or no seed, and that intermorph crosses produce copious seed. The species shares a number of morphological and ecological traits withV. capitata, another distylous, self-incompatible annual species of Western Australia with a greater area of distribution. Artificial hybrids between the two, however, showed reduced pollen stainability. Both species combine a number of specialized morphological features with a breeding system that is primitive for the familyMenyanthaceae.     

Isozyme polymorphism and phylogenetic interpretations in the genus Cicer L.

Summary Allozyme variation among 50 accessions representing the cultivated chickpea (Cicer arietinum L.) and eight wild annual Cicer species was scored and used to assess genetic diversity and phylogeny. Sixteen enzyme systems revealed 22 putative and scorable loci of which 21 showed polymorphism. Variation was prevalent between species (D_st = 0.510) but not within species (H_s = 0.050). No variation for isozyme loci was detected in the cultivated chickpea accessions. Cicer reticulatum had the highest proportion of polymorphic loci (0.59) while the loci Adh-2 and Lap were the most polymorphic over all the species accessions. The phylogeny of annual Cicer species, as determined by allozyme data, generally corroborated those based on other characters in previous studies. Cicer arietinum, C. reticulatum and C. echinospermum formed one cluster, while C. pinnatifidum, C. bijugum and C. judaicum formed another cluster. Cicer chorassanicum was grouped with C. yamashitae, whereas C. cuneatum formed an independent group and showed the largest genetic distance from C. arietinum.     

Recovery after Experimental Cutting and Burning in Three Shrub Communities with Different Dominant Species

The aim of this study is to compare the recovery dynamics in three shrub communities subjected to experimental burning and cutting, and situated on an altitudinal gradient. Climatic features are different in each area, but all had the common characteristic of very homogeneous vegetation cover before the disturbances, with only one shrub species clearly dominant, a different taxon in each area, and with different regeneration strategies. The first area was a heathland dominated by Calluna vulgaris, situated at an altitude of 1600 m, with a continental climate (mean annual precipitation 1320 mm). The second area was a heathland dominated by Erica australis, located at an altitude of 1000 m (mean annual precipitation 840 mm). The third area was a Cistus ladanifer shrubland, located at 900 m altitude, with a Mediterranean climate similar to that of the previous area, but with lower mean annual precipitation (470 mm). Erica australis recovers by vegetative resprouting, but Cistus ladanifer is an obligate seeder, as is Calluna vulgaris in these areas. Each experimental disturbance was carried out over 100 m² in each area. Post-fire recovery is faster in Cistus ladanifer: 2 years after burning there was 40% cover vs. less than 20% in the other two species. However, recovery after cutting was similar for Cistus ladanifer and Erica australis. Calluna vulgaris recovers very slowly, with cover values below 20% even 10 years after both disturbances. Cover of dominant shrub species is negatively correlated with cover of herbaceous species. So different recovery of dominant species lead a different community dynamic in each area.     

Genetic relationships in the genus Cicer L. as revealed by polyacrylamide gel electrophoresis of seed storage proteins

Summary Total seed storage protein of the cultivated chickpea, C. arietinum L., and eight other wild annual Cicer species (all 2n = 16) was separated and compared by sodium dodecyl sulphate polyacrylamide gel electrophoresis. The seed-protein profile was a conservative and species-specific trait. Relative interspecific similarities of protein patterns were estimated using Jaccard's similarity index, and a cluster analysis was performed. The resultant dendrogram generally agreed with the limited data already available on interspecific relationships in Cicer based on morphological characteristics, crossability, genome pairing in hybrids, karyotypes and isozyme analysis. The difference between the profiles of C. judaicum and C. pinnatifidum supported the idea that they are indeed two separate species. The closest relative of C. arietinum was C. reticulatum, followed by C. echinospermum and other species, while C. cuneatum was the farthest relative. In general, C. cuneatum was also genetically the farthest removed from any other species. The suggestion that C. reticulatum is the wild progenitor of the cultivated chickpea was therefore further supported.     

Climate and the evolution of annual/perennial life-histories in Nemesia (Scrophulariaceae)

The Cape Floristic Region and the Succulent Karoo in southwestern Africa are both noted for their plant species richness and high levels of endemism. The southwestern tip of Africa is one of the world's five Mediterranean-type climate regions. The biodiversity in the Cape Floristic Region and Succulent Karoo is thought to be at least partly due to changes to the climate of these regions that have occurred since the middle Miocene. Annual species are usually a significant proportion of local flora in Mediterranean-type climate regions. Previous studies of species radiations in the Cape Floristic Region have concentrated on genera that predominantly contain perennial species. Nemesia (Scrophulariaceae) comprises c. 65 species of annual and perennial herbs and sub-shrubs that are native to southern and tropical Africa. Annuals make up a significant proportion (~75%) of Nemesia species. We have reconstructed a phylogeny of 23 Nemesia species using nucleotide sequences of the ITS, ETS and trnL-spacer regions. Species were grouped into five clades, two composed of annual species, one that contained two annual and one perennial species, one that contained one annual and two perennial species, and one that was predominantly composed of perennial species. Phylogenetic dating of the ITS + ETS based phylogenetic tree using penalised likelihood suggested the genus evolved during the Miocene, and that the majority of extant Nemesia species studied radiated during the Pliocene. Ancestral state reconstruction supports at least three separate origins of the annual habit from plants with a perennial life history. One origin can be traced to the late Miocene while the other two transitions occurred more recently during the Pliocene. The transition from perennial to annual life-histories in Nemesia may have been a response to climate change.     

Assessing and predicting the success of Najas flexilis (Willd.) Rostk. & Schmidt, a rare European aquatic macrophyte, in relation to lake environmental conditions

Najas flexilis (Willd.) Rostk. & Schmidt is a submerged annual macrophyte, rare in Europe, which is protected under the EC Habitats Directive. N. flexilis appears to be decreasing in the British Isles, its main stronghold in Europe. We outline the environmental conditions required for N. flexilis growth, comparing between present and recently extinct sites for the plant. Plant traits (leaf area/shoot length; and reproductive number/shoot length) can be used to assess N. flexilis population success, and models are produced that can predict this. Both the comparison between present and extinct sites, and the models, suggest that eutrophication and acidification of lakes are the main threats to N. flexilis. Acidification appears to reduce the ability of N. flexilis to produce seeds (potentially fatal for an annual). On the other hand, eutrophication leads to conditions where N. flexilis, an obligate carbon dioxide utiliser, cannot photosynthesise due to the predominance of bicarbonate rather than dissolved carbon dioxide in lake water.     

Genome size in Bulgarian Centaurea s.l. (Asteraceae)

Thirty-nine species and subspecies of the genera Centaurea, Colymbada, Psephellus and Cyanus (all included in Centaurea s.l.) including many rare and endemic taxa of preponderantly Bulgarian distribution have been investigated with Feulgen DNA image densitometry for holoploid and monoploid genome size (C- and Cx-values). Cyanus varies gradually 2.17-fold between 0.74 pg and 1.56 pg (1Cx). In the remaining taxa two major genome size groups are found, which differ about 1.8-fold in Cx-value. Low values occur in Centaurea subgenera Acrolophus, Solstitiaria, Phalolepis (0.77 pg to 0.90 pg, 1Cx) and Jacea (0.95 pg to 1.09 pg, 1Cx), high values in the genera Colymbada (1.65 pg to 1.93 pg, 1Cx) and Psephellus (1.79 pg, 1Cx, in P. marschallianus). Cx-values support a distinction of Colymbada from Centaurea. Genome size variation is discussed with regard to phylogeny, life form (annual versus perennial), polyploidy, chromosome basic numbers, altitude of occurrence and climate, endemism, and rarity.     

我国3个桉树人工林种植区生产力影响因素

研究影响桉树人工林生产力的主要因素,对于提高桉树人工林生产力以及经营水平和合理利用树种都具有重要的意义。收集我国3个桉树人工林种植区(广东省、广西壮族自治区、云南省)关于生物量与生产力研究中的相关数据,对海拔、林分密度、林龄、年均温和年降水量与乔木层生物量进行了主成分分析与混合模型分析,探究各因素对我国桉树人工林生物量与生产力的影响。结果显示:年均温、年降水量、林龄、海拔和林分密度均是影响广东、广西、云南这3个省(区)桉树人工林生物量的主要因素,其中年降水量对这3个地区桉树人工林的生物量影响极其显著(P0.01),林龄和林分密度对桉树人工林的生物量影响显著(P0.05)。这是因为这3个地区都位于亚热带,温度都属于桉树生长的适宜温度,而这3个地区存在明显的干湿季,降水量在季节和地域上分布不均匀,导致这3个地区年降水量存在较明显的差异。因此,年降水量成为影响这3个地区桉树人工林生物量的关键因素。     

辽宁省人工林樟子松径向生长对水热梯度变化的响应

基于树轮年代学的理论和方法,建立辽宁地区人工林樟子松年轮宽度年表网络,研究人工林樟子松树木年轮生长变化,探讨樟子松生长与气候变化的关系以及其对水热梯度变化的响应规律。结果表明,研究区各采样点人工林樟子松的径向生长变化呈现较为一致的显著下降趋势(P0.05),并且下降趋势由西北至东南降低。空间上水平上,研究区樟子松的径向生长与研究区降水和相对湿度的空间梯度变化吻合(P0.05),均呈西北至东南增加的特点;各采样点樟子松年轮宽度变化的平均敏感度与降水量、相对湿度显著负相关关系(P0.05),但与温度的正相关关系不显著。各样点樟子松径向生长与月降雨量和月平均相对湿度多呈正相关关系,与月平均温度多呈负相关关系,进一步表明区域水分因子对人工林樟子松生长的限制作用明显。     

Comparative mapping of loci controlling winter survival and related traits in oilseed Brassica rapa and B. napus

Winter survival is an important characteristic of oilseedBrassica that is seeded in the fall in northern climates,and it may be affected by genetic variation for other cold-regulated traits,such as freezing tolerance and vernalization responsive flowering time. Weanalyzed immortalized populations of oilseed Brassica rapa(recombinant inbred lines) and B. napus (double haploidlines) derived from crosses of annual and biennial types in order to comparethe map positions and effects of quantitative trait loci controlling wintersurvival, nonacclimated and acclimated freezing tolerances, and flowering time.The B. napus population was evaluated in multiple winters,and six of the 16 total significant QTL for winter survival were detected inmore than one winter. Correspondence in the map positions of QTL controllingdifferent traits within species provided evidence that some alleles causinggreater acclimated freezing tolerance and later flowering time also contributedto increased winter survival. Correspondence in the map positions of QTLbetween species provided evidence for allelic variation at homologous loci inB. rapa and B. napus. The potentialrole of some candidate genes in regulating these traits is discussed.     

气候变暖背景下春兰和蕙兰的适生区分布预测

为了阐明气候变暖背景下春兰(Cymbidium goeringii)和蕙兰(C. faberi)在我国的适生区分布变化情况,根据157条分布记录和19个生物气候变量,应用最大熵物种分布模型,对2070年4种温室气体排放情景下春兰和蕙兰在我国的适生区分布进行预测,并筛选影响其地理分布的主要气候因子。结果表明:(1)2070年春兰和蕙兰分布点的年均温(bio1)、最冷月最低温度(bio6)和最冷季平均温度(bio11)等均升高,气候有变暖趋势;(2)受试者工作特征曲线下面积(AUC)值在0.9—1.0之间,模型预测结果可信度较高;(3)影响春兰、蕙兰当前和2070年地理分布的限制性气候因子主要有最冷月最低温度(bio6)、最冷季平均温度(bio11)、年均降水量(bio12)和最干月份降水量(bio14);(4)气候变暖将会对春兰和蕙兰的适宜生境范围和面积产生影响。预测2070年春兰的适宜生境面积将会有所减小,而蕙兰的适宜生境面积将会增加,且整体有向北迁移的趋势。研究结果为野生春兰和蕙兰的生态风险评价和引种提供了重要依据。     

印加孔雀草入侵生态风险评估及其管理措施

【目的】印加孔雀草为菊科一年生草本植物,原产南美洲,现已在我国多个地区发现,局部呈现生态危害。分析印加孔雀草生态适应性特点,可以有针对地提出其风险指标体系和判断标准,确定其危险级别。【方法】对印加孔雀草的分布、危害情况及生物学特性进行调查,定性分析其生态适应性特点,定量分析评估其生态风险,确定其危险级别。【结果】根据风险指标体系准则层的赋值,其中入侵性R_1为83,适应性R_2为88,扩散性R_3为65,危害性R_4为84,计算得出印加孔雀草风险值(R)=8061,属于具有危害性和侵入性的物种。【结论】印加孔雀草为具有危害性和侵入性的物种,应严格禁止引入。由于该植物已经传入我国,应采取必要的应急措施,开展检疫、监测和灭除,防止其传入其他还未发生的地区。     

Life cycle and production of Hydrobia acuta Drap. (Gastropoda: Prosobranchia) in a hypersaline coastal lagoon

The life cycle and annual production of Hydrobia acuta was studied in a hypersaline lagoon (s = 39 in summer), forming a part of solar salt works. Quantitative random samples were taken at regular intervals over a period of 15 months using a corer, and snails collected were counted and measured. Weight and biomass was calculated from a length-weight relationship and from measurements of ash content. H. acuta was a strictly annual species in the study lagoon. Recruitment takes place over a brief period in May and June, after which the breeding population dies. Growth of the new generation was slow during summer, probably due to the unfavourably high salinity. A period of rapid growth took place in autumn coinciding with a drop in salinity caused by rainfall. In winter Hydrobia hibernated by burrowing deeply into the sediment. Growth recommenced in spring when the lagoon was reflooded, but by this time the number of survivors was low.The maximum density of snails was 6 000 m^–2 and maximum biomass 500 mg organic dry wt · m^–2. Annual cohort production was estimated as 786 mg organic dry wt · m^–2 · a^–1. These figures are low compared to other studies on hydrobiid snails, and for production in inland waters, but the value for annual P/B = 4.5 is typical for a univoltine species. The relevance of the results to foraging by wading birds (the main consumers), is discussed.     

Estimating the Productivity of the Black Sea Bivalve Chamelea gallinafrom the Size and Biomass of Its Populations

Characteristics of annual production based on various mass data (whole animal mass; shell mass; and wet, dry, and ash-free dry soft tissue mass), the P/B coefficient, and specific production were estimated for the bivalve mollusk Chamelea gallinasampled from 21 localities in the northwestern and eastern Black Sea. The annual production correlated with population biomass (r= 0.994) and mean individual mass (r= –0.737), while the P/Bcoefficient depended mainly on mean individual mass (r= –0.719). Estimates of the P/Bcoefficient in Ch. gallinafrom the Black Sea were smaller than those of other marine invertebrates found worldwide with the same energy equivalent. Multiple linear regression equations were calculated for empirical relationships of various characteristics of annual production to the population biomass and mean individual biomass of Ch. gallina.