Guild structures of seed insects in relation to acorn development in two oak species

We investigated patterns of acorn growth in Quercus variabilis Blume and Quercus serrata Thunb., seasonal trends in emergence of seed insects found in the acorns, oviposition periods of the insects and falling periods of insect-infested acorns. In Q. variabilis, two insect guilds were associated with acorn development: (i) the immature acorn feeding (IAF) guild [Curculionidae sp., Poecilips cardamomi (Schaufuss), and Characoma ruficirra (Hampson)]; and (ii) the mature acorn feeding (MAF) guild [Curculio robustus (Roelofs), Curculio sikkimensis (Heller), and Cydia glandicolana (Danilevsky)]. In Q. serrata, there were three guilds: (i) the pistillate flower feeding (PFF) guild (cynipid wasp); (ii) the IAF guild [sap absorption by Mechoris ursulus (Roelofs)]; and (iii) the MAF guild (M. ursulus, C. sikkimensis, Cydia danilevskyi (Kuznetzov), C. glandicolana and Autostichidae sp.). The succession of guilds during acorn development may be a consequence of the use by different species of the limited food resource. The lack of a PFF guild in Q. variabilis that was found in our field site would have a positive effect on IAF guilds in utilizing the acorns.     

Selective consumption of acorns by the Japanese wood mouse according to tannin content: a behavioral countermeasure against plant secondary metabolites

We examined the presence of selective consumption against tannins in acorns as a pre-ingestive countermeasure to plant secondary metabolites by using the Japanese wood mouse (Apodemus speciosus) and acorns of Quercus serrata, which contained ca. 6.4% tannins on a dry weight basis. In addition, the presence of selective consumption against proteins was also examined. In the acorn-feeding experiment, 18 wood mice were allocated to two groups: the experienced group (N = 9), which had previous experience in feeding on acorns, and the inexperienced group (N = 9), which had no experience. Mice of both groups were fed only acorns for 3 nights. Selectivity against tannins (an index estimated from the tannin content in control, remaining, and ingested acorns) was significantly positive in the experienced group, indicating the presence of selective consumption against tannins. In contrast, mice in the inexperienced group did not show significant selectivity against tannins. Comparing the selectivity indices directly between two groups, however, they did not differ significantly. Selective consumption against proteins rather than that for proteins also occurred in the experienced group, but it was thought to be a byproduct resulted from the selectivity against tannins. Selective consumption against tannins can mitigate the negative effects of tannins by decreasing tannin intake.     

Hoarding of acorns by granivorous mice and its role in the population processes of Pasania edulis (Makino) Makino

In order to evaluate the role of granivorous mice, Apodemus speciosus Temminck and Apodemus argenteus Temminck, in the regeneration of Pasania edulis (Makino) Makino, an evergreen tree, we conducted field studies examining acorn crops, the population dynamics and hoarding behavior of mice and pre- and postdispersal acorn predation in an evergreen broad-leaved forest dominated by P.edulis in Kagoshima, southern Japan. The study was conducted from 1994 to 2000. Apodemus mice selected sound acorns and hoarded them in the soil after transporting them for distances ranging from 5.4 to 19.9m. This behavior appeared to be beneficial to the establishment of seedlings of P.edulis. However, the positive effects were negated by a high rate of recovery of the acorns hoarded by the mice. A life-table analysis of five cohorts of P.edulis indicated that postdispersal predation of acorns by Apodemus mice was a major contributor to annual variation in the number of new seedlings. A considerable number of acorns germinated only in years with a good acorn crop and a low level of resident mice. These results suggest that Apodemus mice are serious acorn predators rather than important dispersers. After germination, acorns were attacked by the acorn borer at a high rate. From these results, we can conclude that acorn production probably makes a smaller contribution to the regeneration of P.edulis than coppice shoot production at the study site.     

Comparison of growth habits under various light conditions between two climax species, Castanopsis sieboldii and Castanopsis cuspidata, with special reference to their shade tolerance

Two experiments were conducted to examine the difference in shade tolerance between two climax species, Castanopsis sieboldii and Castanopsis cuspidata, in Aichi Prefecture in the warm-temperate climate of Japan. In the growth experiment, the seedlings of the two species were raised under five light conditions, 100%, 30%, 10%, 3% and 1% relative light intensity (RLI). The growth of C. sieboldii highly exceeded that of C. cuspidata, particularly under higher light conditions. In the heavy shading experiment, the seedlings of the two species were grown under three light conditions (0, 0.15 and 0.3% RLI). While all seedlings of C. sieboldii died within 2 years under 0.15 and 0.3% RLI, about half of the seedlings of C. cuspidata survived more than 2 years under 0.15% RLI, and about 70% survived more than 4 years under 0.3% RLI. It was concluded that C. cuspidata was more shade tolerant than C. sieboldii, and the possibility that C. sieboldii might be more tolerant of the drought stress than C. cuspidata was discussed.     

Microsatellite variation and differentiation among local populations of Castanopsis species in Japan

Microsatellite variations in Castanopsis species in Japan were examined to clarify the genetic relationships among 25 local populations according to the difference in the number of layers of adaxial epidermis in the leaves. Six microsatellite loci were assayed for 629 seedlings from the populations, and these seedlings were classified into five types according to the state of the leaf epidermis. Remarkable differences in the allele frequency of the six microsatellite loci were observed among these local populations. The coefficients of genetic differentiation, R_ST, of each locus ranged from 0.209 to 0.388. An unweighted pair-group method (UPGMA) phenogram constructed on the population pairwise R_ST over the loci revealed three clusters (A–C), and six sub-clusters. These clusters reflected the differences in the occurrence frequency of seedlings in each epidermis type within a population. Our findings suggest that clusters A and C are the local populations dominated by Castanopsis sieboldii and Castanopsis cuspidata, respectively, while local populations of cluster B are composed of the two Castanopsis species and/or include many individuals derived by hybridization. The six sub-clusters were found to reflect the geographic relationship among the populations, suggesting a different process for geographic population dynamics during the postglacial period.     

Establishment of the case of Hebeloma radicosum growth on the latrine of the wood mouse

Three cases of Hebeloma radicosum growth on the wood-mouse latrine near a wood-mouse nest are here described from Switzerland. This study establishes that this fungus may associate with wood mice, besides associating with moles as has been previously known. The nest occupant and the latrine maker were independently identified to ensure that the two were not different. For this identification, the characteristics of fallen hairs found from the nest and of those found from the deserted latrines now colonized by the fungus were taken as the most important information. In addition to these case studies, information about the occurrence of H. radicosum in northern Europe and northern Japan (Hokkaido) where moles do not occur is presented, which explicitly indicates the possibility of customer animals other than moles.     

Recovery of mycorrhizas of a fungus, <Emphasis Type="Italic">Cenococcum geophilum</Emphasis>, after urea treatment in warm temperate forests in Japan

We studied recovery of the ectomycorrhizal species Cenococcum geophilum (Cg) after urea treatment in two types of vegetation. The recovery was as quick as 6 months after the treatment and overlapped the fruiting period of ectomycorrhizal ammonia fungi. Ectomycorrhizas investigated as Cg belonged to a single species irrespective of treatment and vegetation type. Cg ectomycorrhizas were significantly more abundant in density in nontreated soil than in treated soil. Between vegetation types, Cg ectomycorrhizas were significantly more in density in broad-leaved deciduous forest than in broad-leaved evergreen forest. Moreover, Cg was dominant in the nontreated soils of the former type of forest.     

Quantitative analysis of acorn transportation by rodents using magnetic locator

Transported distance and mortality of acorns scattered by rodents were investigated with magnets inserted into acorns (40 of Quercus serrata and 20 of Quercus acutissima) and a magnetic locator in a natural forest stand. All the treated acorns were transported, and 60% of them were discovered again with a magnetic locator from autumn to the next spring. Most transported acorns suffered predation within one month after the start of the experiment. Several acorns were rehoarded at least two or three times. Average transported distance of scattered acorns was 22.1±8.9 m (max=38.5 m) and the survival rate was 3.0%. The magnet method is one of the most effective methods for tracking acorns through the winter.     

Influence of method of presentation on results of plant-host preference tests with two species of grasshopper

Leaf material of two Piper spp. (Piperaceae) was presented to two different generalist herbivores (Orthoptera: Acrididae) to determine whether method of leaf presentation in preference trials affects choice. For the grasshopper Leptomerinthoprora brevipennis, the method of presentation had no effect on preference ranking: more of Piper sancti-felicis was eaten than of P. arieianum, regardless of whether leaf material was presented as leaf disks, whole leaves supplemented with water, or whole leaves without water. In contrast, preference of the grasshopper Abracis flavolineata depended on presentation method. In that case, whole leaves of P. scancti-felicis supplemented with water were preferred over the same of P. arieianum, while dry weight consumption of leaf disks of P. arieianum was greater than that for disks of P. sancti-felicis. When presented with leaves not supplemented with water, A. flavolineata showed no significant preference for one plant species over another.

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Résumé Des feuilles provenant de deux espèces de Piper (Piperacae) ont été proposées à deux Orthoptères, Acrididae, herbivores généralistes, pour déterminer si la méthode de présentation des feuilles modifiait le choix. Pour Leptomerinthoprora brevipennis, la méthode de présentation est sans influence sur l'ordre de préférence; la consommation de Piper sancti-felicis est toujours supérieure à celle de P. arieianum, quelque soit le mode de présentation: disques de feuilles, feuilles entières humidifiées, ou feuilles entières sans addition d'eau. A l'opposé, l'ordre de préférence de Abracis flavolineata dépend du type de présentation; les feuilles entières humidifiées de P. sancti-felicis sont préférées à celles de P. arieianum proposées de la même façon, tandis que la consommation de disques secs de P. arieianum est plus importante que celle des disques secs de P. sancti-felicis. En présence de feuilles entières humidifiées, A. flavolineata ne manifeste aucune préférence.

     

In vitro propagation of two spanish endemic species of salvia throught bud proliferation

Summary Salvia valentina Vahl and Salvia blancoana Webb & Heldr subsp. mariolensis Figuerola, two endemic species of Salvia from the Mediterranean coastal region of Spain, were successfully gegenerated in vitro from adult plants using two explant types (apical and nodal segments). Maximum shoot proliferation for both species was obtained with nodal explants: for S. blancoana on Murashige and Skoog medium supplemented with 6-γ-γ-dimethylallylaminopurine at 1 mg 1⁻¹ (4.9 μM). and for S. valentina on the same medium with kinetin at 1–2 mg 1⁻¹ (4.6–9.3 μM). The influence of apical dominance, and the explant viability in culture were found to be the main differences between the two species during the shoot multiplication phase. Rooting of shoots was low, specially for S. valentina. For both species, rooting was achieved in Murashige and Skoog medium without growth regulators. In general the addition of the auxins indole 3 acetic acid or indole-3-butyric acid did not improve the rooting or, in the case of naphthaleneacetic acid, had an inhibitory effect. In the best rooting media, rooting shoots increased in length. The rooted plantlets were acclimated to ex vitro conditions and a survival percentage > 70% was obtained under greenhouse conditions. This work was carried out as an ex situ conservation method for these Spanish endemic species.     

Home range and mating system of two sympatric field mouse species,Apodemus speciosus andApodemus argenteus

The size and spatial distribution of home ranges in two sympatric field mouse species,Apodemus speciosus andApodemus argenteus, were revealed by the capture-recapture method in a temperate deciduous forest from June 1987 to June 1990. InA. speciosus, the home ranges of males were significantly larger tha those of females, and overlapped with those of other males and females during the breeding season. InA. argenteus, the home range of each male overlapped only that of a single female throughout the year. These results suggested thatA. speciosus was promiscuous or polygynous andA. argenteus was monogamous.     

Fruit size in a tropical tree species: variation,preference by birds,and heritability

Ocotea tenera (Lauraceae), an understory bird-dispersed tree, produces single-seeded fruits that vary in diameter from 1.4 to 2.4 cm. Much of the variation within a population at Monteverde, Costa Rica occurred within individual trees. The relative size of fruits produced by different trees remained generally constant over an 11-year period despite slight differences between years in the average size of fruits produced by a given tree.Fruit-eating birds could thus express their preferences for particular fruit size characteristics by choosing among trees that have distinct distributions of fruit diameters, and between individually variable fruits within trees. In a field study of individually marked fruits, birds removed 46.2% of fruits; the rest of the fruits were destroyed by invertebrate (25.3%) and vertebrate (4.3%) pulp-feeders or aborted by the plant after remaining ripe but uneaten for as long as 100 days (24.2%). The four major avian seed dispersers of O. tenera each have gape widths exceeding all but the largest fruits. Birds preferred plants with greater-than-average-sized fruits; within trees, they favored larger fruits, apparently because net pulp mass increases with fruit diameter. Fruits that ripened early in the season were more likely to be removed and were removed more quickly than late-ripening fruits.Based on mother-offspring regressions of mean fruit size, the phenotypic variation in fruit diameter in O. tenera is highly heritable, indicating the potential for an evolutionary response to selection by birds. Nonetheless, directional selection on fruit size or shape is likely to be inconsistent, constrained by genetic correlations, and weak compared to selection on traits like fecundity or phenology.     

Estimation of the retention times and distances of seed dispersed by two monkey species, Alouatta seniculus and Lagothrix lagotricha, in a Colombian forest

Isolated-bout method to estimate the retention times and dispersal distances was applied to the seed dispersal by red howler monkeys (Alouatta seniculus) and Humboldts woolly monkeys (Lagothrix lagotricha) in a lowland tropical forest at La Macarena, on the border of the Macarena and Tinigua National Parks, the Department of Meta, Colombia. Continuous observations were made on the feeding and ranging behavior of well-habituated troops of howler monkeys and woolly monkeys as well as continuous collection of monkeys feces. We selected out the isolated-bout as a feeding bout on the specific species that was only once recorded within 48 h before the seeds of that species appeared in the feces of monkeys. In that case, the seeds were strongly suggested to come from that isolated bout. Then retention times, route seed dispersal distances and direct seed dispersal distances were estimated. Howler monkeys, which are regarded as generalist herbivores, showed longer retention times and dispersal distances along monkeys route than did woolly monkeys, which are specialist frugivores. However, the direct distances that seeds were carried from the mother tree were not significantly greater for howler monkeys than for woolly monkeys. This shows that both retention time and movement patterns by the monkeys, especially the total ranging area, influence the direct distance that seeds are carried from the mother tree.     

Germination and water dispersal of seeds from a threatened plant species Penthorum chinense

To conserve a threatened plant species (Penthorum chinense Pursh) in Japan, seed germination responses to pretreatment (imbibition and/or chilled), temperature and light, and seed dispersal by water were examined. The seeds collected from abandoned paddy fields in a warm temperate region, central Japan, germinated in light (14 h photoperiod; light 22°C, dark 21°C) after a moist-chilled treatment. After this pretreatment, the seeds germinated well at 10–25°C (optimum temperature 15°C), but did not germinate in darkness even at the optimum temperature. Most of the seeds floated on distilled water, but 20–60% of the seeds that were collected from several populations sank in distilled water, indicating dimorphism in seed dispersal by water. The floating and sunken seeds did not show significant differences in weight and germination rate within a population. The addition of a surface-active agent in distilled water submerged the seeds, indicating that the buoyancy of the seeds is attributable to an oil coating on the seed surface that enhances the interfacial tension on the seeds. Three times the number of seeds sank in river water collected from a rural area than in distilled water. A greater number of seeds also sank in water that had increasing concentrations of linear alkylbenzenesulfonate, which is a major component of synthetic detergents. This suggests that the water dispersal of this species is suppressed by surface-active agents, including detergents, in river water.     

Screening for microbial trehalases: extracellular trehalases produced byFusarium species

Two hundred microorganisms comprising actinomycetes, bacteria, fungi and yeasts were screened for extracellular trehalases by their growth on trehalose in solid and liquid culture.Candida albicans, Gelasinospora retispora and four isolates belonging to the genusFusarium produced extracellular trehalases. The production of trehalase by theFusarium spp. was influenced by the nutrient composition of the medium and the carbon source; of the substrates examined starch produced the highest enzyme titre. Trehalase was an inducible enzyme and was repressed when theFusarium spp. were grown on glucose. The properties of the trehalases from two of theFusarium spp. (isolates MU-105 and TR-8) were typical of non-regulatory trehalases. Activity of several α-glucosidases, an amylase, an invertase and a cellobiase was also demonstrated when the two isolates were grown on trehalose.     

Development of microsatellite markers for Quercus miyagii Koidz. (Fagaceae), an endemic species in the Ryukyu Islands, Japan

Quercus miyagii is an endemic tree species in the Ryukyu Islands, Japan. We isolated and characterized 15 microsatellite loci in this species. The number of alleles ranged from 2 to 16 and expected heterozygosities from 0.07 to 0.92. This set of markers is potentially useful to investigate the genetic structure, gene flow, and the biogeographic history of Q. miyagii in the Ryukyu Islands, Japan.     

Tissue-water relations of two co-occurring evergreen Mediterranean species in response to seasonal and experimental drought conditions

Tissue-water relations were used to characterize the responses of two Mediterranean co-occurring woody species (Quercus ilex L. and Phillyrea latifolia L.) to seasonal and experimental drought conditions. Soil water availability was reduced 15% by partially excluding rain throughfall and lateral flow (water runoff). Seasonal and experimental drought elicited physiological and morphological adaptations other than osmotic adjustment: both species showed large increases in cell-wall elasticity and decreased saturated-to-dry-mass ratio. Increased elasticity (lower elastic modulus) resulted in concurrent decreases in relative water content at turgor loss. In addition, P. latifolia showed significant increases in apoplastic water fraction. Decreased saturated-to-dry-mass ratio and increased apoplastic water fraction were accompanied by an increased range of turgor maintenance, which indicates that leaf sclerophyllous traits might be advantageous in drier scenarios. In contrast, the degree of sclerophylly (as assessed by the leaf mass-to-area ratio) was not related to tissue elasticity. An 15% reduction in soil water availability resulted in significant reductions in diameter growth when compared to control plants in both species. Moreover, although P. latifolia underwent larger changes in tissue water-related traits than Q. ilex in response to decreasing water availability, growth was more sensitive to water stress in P. latifolia than in Q. ilex. Differences in diameter growth between species might be partially linked to the effects of cell-wall elasticity and turgor pressure on growth, since Q. ilex showed higher tissue elasticity and higher intrinsic tolerance to water deficit (as indicated by lower relative water content at turgor loss) than P. latifolia.     

Experimental study on the impact of dinoflagellate Alexandrium species on populations of the rotifer Brachionus plicatilis

To investigate harmful effects of the dinoflagellate Alexandrium species on microzooplankton, the rotifer Brachionus plicatilis was chosen as an assay species, and tested with 10 strains of Alexandrium including one known non-PSP-producer (Alexandrium tamarense, AT-6). HPLC analysis confirmed the PSP-content of the various strains: Alexandrium lusitanicum, Alexandrium minutum and Alexandrium tamarense (ATHK, AT5-1, AT5-3, ATCI02, ATCI03) used in the experiment were PSP-producers. No PSP toxins were detected in the strains Alexandrium sp1, Alexandrium sp2.Exposing rotifer populations to the densities of 2000 cells ml⁻¹ of each of these 10 Alexandrium strains revealed that the (non-PSP) A. tamarense (AT-6) and two other PSP-producing algae: A. lusitanicum, A. minutum, did not appear to adversely impact rotifer populations. Rotifers exposed to these three strains were able to maintain their population numbers, and in some cases, increase them. Although some increases in rotifer population growth following exposures to these three algal species were noted, the rate was less than for the non-exposed control rotifer groups.In contrast, the remaining seven algal strains (A. tamarense ATHK, AT5-1, AT5-3, ATCI02, ATCI03; also Alexandrium sp1 and Alexandrium sp2) all have adverse effects on the rotifers. Dosing rotifers with respective algal cell densities of 2000 cells ml⁻¹ each, for Alexandrium sp1, Alexandrium sp2, and A. tamarense strains ATHK and ATCI03 showed mean lethal time (LT₅₀) on rotifer populations of 21, 28, 29, and 36h, respectively. The remaining three species (A. tamarense strains AT5-1, AT5-3, ATCI02) caused respective mean rotifer LT₅₀s of 56, 56, and 71 h, compared to 160 h for the unexposed “starved control” rotifers. Experiments to determine ingestion rates for the rotifers, based on changes in their Chlorophyll a content, showed that the rotifers could feed on A. lusitanicum, A. minutum and A. tamarense strain AT-6, but could graze to little or no extent upon algal cells of the other seven strains. The effects on rotifers exposed to different cell densities, fractions, and growth phases of A. tamarense algal culture were respectively compared. It was found that only the whole algal cells had lethal effects, with strongest impact being shown by the early exponential growth phase of A. tamarense. The results indicate that some toxic mechanism(s), other than PSP and present in whole algal cells, might be responsible for the adverse effects on the exposed rotifers.     

Studies on five species of Pythium parasitic on mustard and cabbage in India

Diseased seedlings and roots of cabbage and mustard of Khurpatal (Nainital), were surveyed for zoosporic plant pathogens. Pythium aphanidermatum and P. debaryanum were isolated from cabbage and P. middletonii, P. spinosum and P. undulatum were isolated from mustard. Pathogenicity tests conducted in the glasshouse indicated that P. debaryanum and P. spinosum are the most virulent pathogens of cabbage and mustard respectively.