Shark attacks in the rivers of southern Iran

Synopsis The literature on shark attacks in freshwaters of southern Iran is reviewed and 11 attacks with 3 fatalities recorded from local informants for the period 1953 to 1985. The species of shark responsible is probably the bull shark, Carcharhinus leucas, whose presence in the Tigris River is confirmed by preserved specimens in the British Museum (Natural History). The Iranian records represent a significant proportion (28%) of the documented cases world-wide for unprovoked, freshwater attacks.     

Analysis of variability in vertebral morphology and growth ring counts in two Carcharhinid sharks

Inter- and intra-regional variations in vertebrae morphology and growth increment counts (band counts) were analyzed for two carcharhinid shark species, Carcharhinus plumbeus (n = 10) and C. limbatus (n = 11). Five sequential vertebrae were removed from the cervical region, above the branchial chamber and posterior to the chondrocrainium, and thoracic region, below the first dorsal fin. Dorsal–ventral height, medial–lateral breadth, and caudal–cranial length were measured for each sampled vertebra. Results indicate no significant difference in vertebral morphology within a sampled region of the vertebral column. However, a significant difference in vertebral morphology was noted between regions for both shark species, with thoracic vertebrae consistently larger than cervical vertebrae. A sub-set of three vertebrae was taken from each sampled region of each shark for sectioning and counting of growth increments. Analyses of growth increment counts by two readers indicated no significant difference in band counts within and between sampled regions.     

Xylem water flow in tropical vines as measured by a steady state heating method

Summary A method for determining the mass flow rate of xylem water in thin stems under natural field conditions is presented. Diurnal courses of xylem water flow and stomatal conductance of the vines Entadopsis polystachya, Cyclanthera multifoliolata, and Serjania brachycarpa were examined in a tropical deciduous forest on the west coast of Mexico. E. polystachya (leaf area 23.6 m²) had a maximum water flow rate of 6.50 kg h^-1 or 1.44 kg cm^-2 _{stem basal area} h^-1; daily water use was 2.00 kg m^-2 _{leaf area} day^-1. S. brachycarpa (leaf area 4.5 m²) and C. multifoliolata (leaf area 3.6 m²) had a maximum water flow rate of 0.72 and 0.19 kg h^-1 or 0.63 and 0.92 kg cm^-2 _{stem basal area} h^-1. Daily water use was 1.26 and 0.39 kg m^-2 _{leaf area} day^-1, respectively. The daily courses of xylem water flow were strongly influenced by the orientation of the leaf area to irradiance and its intensity. While leaves of E. polystachya had a constant high stomatal conductance during the day, S. brachycarpa had a maximum stomatal opening in the morning followed by continuous closure during the rest of the day. In contrast to the woody species, the herbaceous C. multifoliolata exhibited a strong midday depression of stomatal conductance and wilting of its leaves. The leaf biomass accounted for 8% (Entadopsis), 16% (Serjania), and 23% (Cyclanthera) of above-ground biomass. The relation of sapwood area to leaf area supplied (Huber value) was 0.19 (Entadopsis), 0.18 (Serjania), and 0.06 (Cyclanthera) cm² m^-2     

Relationships in theAcanthaceae and related families as suggested by cladistic analysis ofrbcL nucleotide sequences

A parsimony analysis of DNA sequences of the chloroplast-encoded generbcL from twelve members of theAcanthaceae s.l., including members of the sometimes segregateThunbergioideae andNelsonioideae, and other families in theBignoniales sensuThorne (1992) is presented. The results largely agree with the classification of theAcanthaceae presented byBremekamp (1965) andThorne (1992) and supportNelsonioideae as a sister group to the rest of theAcanthaceae. Thunbergioideae are placed as a sister toAcanthaceae s.str.Acanthus andAphelandra, both representatives ofAcanthoideae, form a sister group toRuellioideae. An analysis of branch support found that many branches throughout theBignoniales are weakly upheld. This points to the need for further studies in the group using more sequences ofrbcL as well as other data. None of the families ofBignoniales as presently circumscribed (includingAcanthaceae s.l.) were strongly supported, although the larger clade containing the families of theBignoniales was robust.     

Mesocosm experiment on the impact of invertebrate predation on zooplankton of a tropical lake

Invertebrate predation on zooplankton was investigated in mesocosms in the shallow tropical Lake Monte Alegre, São Paulo State, Brazil, in the summer of 1999. Two treatments were applied: one with natural densities of prey and the predators Chaoborus brasiliensis and the water mite Krendowskia sp. (Pr+), and another without predators (Pr-). Three enclosures (volume: 6.6 m³ of water per enclosure) per treatment were installed in the sediment of the deepest area of the lake (5.0 m). At the beginning, Chaoborus larvae were present in Pr- enclosures, because of technical difficulties in preventing their entrance, but they virtually disappeared in the course of the experiment. Water mites were almost absent in Pr- enclosures. Chaoborus predation negatively influenced the Daphnia gessneri population, but not the populations of the copepods Tropocyclops prasinus and Thermocyclops decipiens and the rotifers Keratella spp. Death rates of Daphnia were generally significantly higher in the Pr+ treatment; Daphnia densities increased after the disappearance of Chaoborus in Pr-. Copepod losses to predation in the experiment may be compensated by higher fecundity, shorter egg development time, and lower pressure on egg-bearing females, resulting in a lower susceptibility to Chaoborus predation. The predation impact of water mite on microcrustaceans and rotifers in the experiment was negligible.     

Utilisation of soil organic P by agroforestry and crop species in the field,western Kenya

A field experiment in western Kenya assessed whether the agroforestry species Tithonia diversifolia (Hemsley) A. Gray, Tephrosia vogelii Hook f., Crotalaria grahamiana Wight & Arn. and Sesbania sesban (L) Merill. had access to forms of soil P unavailable to maize, and the consequences of this for sustainable management of biomass transfer. The species were grown in rows at high planting density to ensure the soil under rows was thoroughly permeated by roots. Soil samples taken from beneath rows were compared to controls, which included a bulk soil monolith enclosed by iron sheets within the tithonia plot, continuous maize, and bare fallow plots. Three separate plant biomass samples and soil samples were taken at 6-month intervals, over a period of 18 months. The agroforestry species produced mainly leaf biomass in the first 6 months but stem growth dominated thereafter. Consequently, litterfall was greatest early in the experiment (0–6 months) and declined with continued growth. Soil pH increased by up to 1 unit (from pH 4.85) and available P increased by up to 38% (1 g P g^–1) in agroforestry plots where biomass was conserved on the field. In contrast, in plots where biomass was removed, P availability decreased by up to 15%. Coincident with the declines in litterfall, pH decreased by up to 0.26 pH units, plant available P decreased by between 0.27 and 0.72 g g^–1 and P_o concentration decreased by between 8 and 35 g g^–1 in the agroforestry plots. Declines in P_o were related to phosphatase activity (R²=0.65, P<0.05), which was greater under agroforestry species (0.40–0.50 nmol MUB s^–1 g^–1) than maize (0.28 nmol MUB s^–1 g^–1) or the bare fallow (0.25 nmol MUB s^–1 g^–1). Management of tithonia for biomass transfer, decreased available soil P by 0.70 g g^–1 and P_o by 22.82 g g^–1. In this study, tithonia acquired P_o that was unavailable to maize. However, it is apparent that continuous cutting and removal of biomass would lead to rapid depletion of P stored in organic forms.     

Genetic diversity within and among the wild populations of Murraya koenigii (L.) Spreng., as revealed by ISSR analysis

Murraya koenigii (L.) Spreng., commonly known as curry leaf plant, is found in the different hilly regions of India. In the present study, fifty-nine accessions representing eight wild populations of M. koenigii were analyzed using thirteen ISSR primers. A total of 152 bands were amplified, out of which, 136 were polymorphic corresponding to 89.47% polymorphism across the accessions. The pairwise population genetic distances were calculated for all the populations that varied from 0.05 to 0.13 between the populations of M. koenigii. AMOVA and Nei’s genetic diversity analysis revealed higher genetic variations within populations than among the populations. The clustering of populations in the dendrogram was not in congruence with geographical affiliations. The results indicate that the ISSR method is sufficiently informative and powerful to estimate the genetic diversity in M. koenigii populations. As M. koenigii is an important wild plant genetic resource, therefore, information on genetic variability might be a potential source as breeding material for development of commercially valuable traits in M. koenigii plants.     

Inoculation of pines in a nursery withPisolithus tinctorius andThelephora terrestris in Korea

Summary Mycelial inocula of the two ectomycorrhizal fungi,Pisolithus tinctorius (Pt) andThelephora terrestris (Tt) were artificially introduced into fumigated nursery soil before seed sowing. At the end of the first growing season, Pt stimulated the height growth ofPinus densiflora, P. thunbergii, P. rigida, andP. rigida×taeda by 55, 36, 69, and 37%, respectively, compared with control seedlings (with no fumigation and no inoculation). When growth stimulation was expressed by dry weight, Pt increased dry weight ofP. densiflora andP. rigida×taeda by 143% and 128%, respectively, over control seedlings. Total absorption (per plant top) of nitrogen and phosphorus of inoculatedP. densiflora seedlings was also increased by 188 and 144%, respectively, even though the concentration of these two elements in the tissue was not significantly different from that of control seedlings.Tt failed to stimulate growth of the inoculated plants possibly due to its lower level of infection (40–60% mycorrhizal tips) compared with the relatively high infection (over 80%) of Pt.Pinus koraiensis did not respond to inoculation during the first growing season, probably due to its inherent characteristics of producing a small number of short roots and its slow shoot growth during the first few years after germination.This study was supported by the International Foundation for Science in Stockholm, Sweden.     

Genetic diversity and population differentiation of chestnut blight fungus, Cryphonectria parasitica, in China as revealed by RAPD

Seventeen Cryphonectria parasitica populations sampled from six regions in China were investigated using RAPD. Across all 169 isolates from the 17 populations evaluated, 52 of the 71 markers (73%) were polymorphic, total genetic diversity (h) was 0.1463, and Shannon’s index was 0.2312. Diversity within populations accounted for 74% of total genetic diversity, and genetic differentiation among populations was 0.26 (G _ST = 0.26). Gene flow was 1.4 among the populations; higher gene flow was found among populations within regions and among regions [N _m (G _SR) = 2.8 and N _m (G _RT) = 3.5]. The unweighted pair group mean analysis (UPGMA) dendrogram revealed two distinct clusters: the northern China group and the southern China group. The spatial autocorrelation analysis revealed that the variation at most loci was randomly distributed and lacked spatial structure, but several loci and closer distances were spatially structured. Human activity and habitat could also be important factors affecting genetic structure among C. parasitica populations in China. Genetic diversity was highest in Southwest China, descending in an orderly fashion to Northeast China. This pattern indicated that Southwest China might be the center of origin of C. parasitica in China. The present study provides useful information for understanding the origin and spread of chestnut blight fungus in China and valuable data for formulating relevant strategies for controlling the disease in China.     

Population responses of two omnivorous fish species to impoundment of a Brazilian tropical river

Brycon gouldingi and B. falcatus were the most abundant and widespread of five species of the genus captured in a sampling study encompassing 5 years (1995–2000) in the upper Rio Tocantins, where the river was impounded by the Serra da Mesa hydroelectric dam. Given that impoundments constitute a disturbance to which species will show demographic and biological responses, we assessed such responses of these two omnivorous fishes, whose genus is regarded as vulnerable to impoundments. Both species increased greatly in numbers during the initial reservoir filling period. Brycon gouldingi had higher abundance values than B. falcatus in all sampling months, except in the pre-impoundment period. Both species showed a significant weight increment relative to body length during the time they remained in the reservoir. No reproductive individuals of B. gouldingi were recorded in the study area, but those few of Brycon falcatus were found in both wet and dry seasons, suggesting a more opportunistic strategy of reproduction. Both species were omnivorous and overlapped broadly in diet. The proportions of dietary items, however, varied in relation to fish size class and water dynamics (lotic versus lentic sites). Terrestrial arthropods composed a larger proportion of the diet of smaller-sized individuals and those from lentic sites, whereas seeds and fruits contributed more to the diet of both larger-sized individuals and those from lotic environments. Except for fish and aquatic heteropterans, which were consumed mainly in the reservoir, all other food items were allochthonous, indicating the dependence of these two species of Brycon on the terrestrial environment. The two species responded similarly to the alterations imposed by the impoundment of the upper Tocantins, although reproduction/recruitment pattern was slightly different between species. As observed in other regions of Brazil, impoundments and deforestation appear to produce negative cumulative effects on species of Brycon. These impacts call for greater efforts to conserve and manage members of this diverse and widespread genus. Handling editor: S.M. Thomaz     

Determinants of spatial distribution in a population of the subalpine butterfly Oeneis chryxus

Summary This paper describes temporally varying determinants of the spatial distribution of adults in an insect population and the relationship between that distribution and the mating system. Male Oeneis chryxus butterflies were distributed nonrandomly throughout a sloping Colorado meadow divided horizontally by a dirt road into an upper and lower slope. Over an eight-year period of intensive study, the proportion of males located on the road, the upper slope, and the lower slope varied as a function of population size and sex ratio. In each year, more than half of the male population aggregated on sections of the road in a distinct and recurring pattern that was not correlated with the distribution of any food resource or thermal regime. Females were usually extremely scarce and not distributed in any pattern apparent from the few observations of them. Areas densely occupied by males were associated with visual landmarks. We hypothesize that the male distribution is determined by a pattern of movement of receptive females toward these landmarks. The road offers a thermally favorable environment with an unobstructed view in which to await the passage of scarce females. The mating system in this population has several lek-like features and supports the prediction that landmark mating is a favored strategy under conditions of female scarcity and wide dispersal of resources.     

Connectivity of populations within and between major biogeographic regions of the tropical Pacific in <Emphasis Type="Italic">Conus ebraeus</Emphasis>, a widespread marine gastropod

Information on genetic connectivity and structure of populations in the tropical Pacific is critical for making inferences about the origins and maintenance of diversity in this region. Sequences of the mitochondrial COI gene from 92 individuals of the trans-Pacific gastropod Conus ebraeus from eight localities spanning the tropical Pacific were analyzed to determine whether populations in the western, central, and eastern Pacific exhibit genetic structure, to examine the demographic histories of populations, and to infer patterns of gene flow. A total of 43 unique haplotypes were recovered, including a common haplotype that occurred in six of the eight populations examined. AMOVA and pairwise F-statistics showed that populations in the western and central Pacific were significantly differentiated from populations in the eastern Pacific, but no other evidence of structure. Bayesian isolation–migration (IM) analysis suggested that populations in the western and central Pacific separated from those in eastern Pacific during the Pleistocene. Examination of mismatch distributions and results from IM revealed that populations in the western and central Pacific expanded during the Pleistocene. Gene flow across the East Pacific Barrier appears to occur predominantly westward.     

Demographic characteristics of an intertidal bay goby (Lepidogobius lepidus)

Synopsis In a fourteen month study (May 1976 – June 1977) I examined the following characteristics of an intertidal bay goby (Lepidogobius lepidus) in Morro Bay, California, U.S.A.: annual and seasonal patterns of abundance, age composition and growth rates, survivorship and mortality patterns, and the reproductive cycle for female gobies. Fishes were collected with the aid of quinaldine and otoliths and ovaries removed. Age and growth rates were estimated from otolith annuli using a back calculation formula and a Brody-Bertalanffy growth curve. Mortality rates were derived using the methods of Heincke (1913), Robson & Chapman (1960), mean age, and a catch curve (Ricker 1975). A gonad index was used to describe the annual reproductive cycle. Results indicated that abundance fluctuated seasonally and that these fluctuations appeared to be caused by reproductive emigrations. Bay gobies reached an age of 7+ and a standard length of 87 mm. Growth was relatively constant (6 mm yr⁻¹) until age 5, at which point it began to decline. The mean rates of survivorship, mortality, and instantaneous mortality were 0.75, 0.25, and 0.29 respectively. Mortality rates for individual age classes ranged from 0.13 to 0.51 and increased with age. This stock appears to reproduce mainly during the winter.     

Genetic variation for foot-rot and Fusarium head-blight resistances among full-sib families of a self-incompatible winter rye (Secale cereale L.) population

The amount of genetic variation for resistance to foot rot caused by Pseudocercosporella herpotrichoides, Fusarium spp., and Microdochium nivale and for resistance to head blight caused by Fusarium culmorum are important parameters when estimating selection gain from recurrent selection in winter rye. One-hundred and eighty-six full-sib families of the selfincompatible population variety Halo, representing the Petkus gene pool, were tested for foot-rot resistance at five German location-year combinations (environments) and for head-blight resistance in three environments with artificial inoculation in all but one environment. Foot-rot rating was based on 25 stems per plot scored individually on a 1–9 scale. Head-blight resistance was plotwise scored on a 1–9 scale and, additionally, grain-weight per spike was measured relative to the non-inoculated control plots. Significant estimates of genotypic variance and medium-sized heritabilities (h ²=0.51–0.69) were observed in the combined analyses for all resistance traits. In four out of five environments, the amount of genetic variance was substantially smaller for foot-rot than for head-blight rating. Considerable environmental effects and significant genotype-environment interactions were found for both foot-rot and head-blight resistance. Coefficients of error-corrected correlation among environments were considerably closer than phenotypic correlations. No significant association was found between the resistances to both diseases (r=-0.20 to 0.17). In conclusion, intra-population improvement by recurrent selection should lead to substantial higher foot-rot and head-blight resistances due to significant quantitative genetic variation within Halo. Selection should be carried out in several environments. Lack of correlation between foot-rot and head-blight resistance requires separate infection tests for improving both resistances.     

Identification of fast-growing rhizobia nodulating tropical legumes from Puerto Rico as Rhizobium gallicum and Rhizobium tropici

Fifteen isolates from several nodulated tropical legumes from Puerto Rico (USA) were characterised by their phenotypic, molecular and symbiotic features. The identification of isolates was based on a polyphasic approach, including phenotypic characteristics, 16S rRNA sequencing, Low molecular weight (LMW) RNA profiles, Two Primers-RAPD patterns, and restriction patterns from 16S rDNA molecules. Despite of the variety of hosts included in this study the 15 isolates were separated into only two groups that corresponded to Rhizobium gallicum and Rhizobium tropici. This work shows that R. gallicum and R. tropici nodulate legume plants, such as Sesbania, Caliandra, Poitea, Piptadenia, Neptunia and Mimosa species, that were not previously considered as hosts for these rhizobia. Moreover, some of these host plants can be nodulated by both species. The results confirm the great promiscuity of R. tropici and also support the hypothesis that the species R. gallicum may be native from America or cosmopolitan and worldwide spread.     

Foraging behavior as a determinant of asymmetric competitive interaction between two ant species in a tropical agroecosystem

This work is concerned with elucidating competitive interactions between two neotropical ants, Solenopsis geminata and Pheidole radoszkowskii, focusing on their foraging behavior. When released from competition from P. radoszkowskii, S. geminata increased its foraging activity. On the other hand, when released from competition from S. geminata, P. radoszkowskii did not respond, demonstrating asymmetric competition between the two species. Foraging experiments showed that P. radoszkowskii is more efficient at finding food resources, whereas S. geminata is better at defending the resources once they are encountered. These differences in foraging behavior appear to permit the coexistence of these two species. The practical implications of the results for the management of ant communities in tropical agroecosystems is discussed with respect to the potential use of ants as natural enemies.     

On the conservative nature of the gill filaments of sharks

Synopsis Gill filaments of one highly active and two less active shark species exhibit a conservative morphological scheme including such features as branchial canopies, marginal lamellar projections, and enlarged, discrete outer marginal lamellar channels and lateral lamellar sinuses. The specific spatial orientation of the secondary lamellae respective to one another, the gill filaments, and the interbranchial septa create what appears as one-way interfilament water channels, suggesting the presence of an efficient branchial countercurrent system. It is proposed that the fortified structure of shark gills allows many shark species to ventilate passively without having evolved gill filament modifications as apparently did some highly active teleosts. This in turn may have expedited the evolution of lamnid shark species through pre-adaptation to a swift oceanic lifestyle.     

珍稀濒危植物黄杉种群结构与空间分布格局北大核心CSCD

为了解珍稀濒危植物黄杉种群的生存现状和更新机制,对贵州省威宁县黄杉自然保护区内天然分布的黄杉(Pseudotsuga sinensis)群落的结构特征和空间分布格局进行了研究。结果表明,黄杉种群的中龄级个体数较多,幼龄级和老龄级个体相对较少,呈典型的“∩”型结构。种群结构动态指数V_(pi)(13.49%)和V′_(pi)(0.05%)均大于0,种群属于增长型,但增长幅度逐渐降低,对外界干扰敏感度较高。种群存活曲线趋于Deevey-II型,生命期望值单调下降,死亡率呈“V”型,有2个死亡高峰,第1个出现在I龄级,第2个出现在IX龄级。黄杉种群除部分样地(Q2和Q7)呈均匀分布外,大部分样地呈集群分布;随龄级的增加,空间分布格局由集群分布逐渐趋向于均匀分布。因此,黄杉种群濒危的主要因素是幼树个体无法及时补充种群,建议加强对幼苗的抚育和通过适度干扰,促进黄杉种群的更新。     

Seasonal variation of growth and development of the roots of five second year conifer species in the nursery

Every other week over their second growing season, stem height, collar diameter, shoot and root dry masses, number of lateral roots and length of the tap root were measured on nursery grown seedlings ofAbies balsamea L. Mill.,Pinus banksiana Lamb.,Pinus resinosa Ait.,Picea mariana Mill. BSP andPicea glauca Moench Voss. Root elongation, branching and mycorrhizal development were also recorded.Given species showed distinct seasonal growth patterns. The rate and timing of maximum root growth (mg/dry weight/week) differed markedly between species.Except for the increase in height ofPinus banksiana, root and shoot growth were not negatively correlated.The results are discussed in relation to the performance of tree seedlings in the nursery.     

Isolation and characterization of a temperate cyanophage for a tropical Anabaena strain

In this paper we describe the isolation and characterization of a temperate cyanophage N(S)1 of the genus cyanopodovirus which produces turbid plaques on the host Anabaena 77S15 isolated from tropical soil. Its properties have been compared to those of other well-characterized cyanophages. In addition, two strains of Anabaena 77S15 lysogenic for N(S)1 were isolated. N(S)1 seems to be integrated into the chromosome of the two lysogens, and a 2 kb plasmid present at a low copy number in the non-lysogenic strain is amplified significantly.