Reconsidering diversity–productivity relationships: directness of productivity estimates matters

Despite extensive research efforts, the controversy over diversity–productivity (D–P) patterns in natural communities still looms large. Recent meta‐analyses suggest that unimodal D–P relationships tend to pre‐dominate in plant studies, while positively linear relationships are more common in animal studies. These patterns, however, are based on studies in which productivity is estimated either directly, based on the biomass or energy of the studied organisms, or indirectly, according to the productivity of lower trophic levels, and various surrogates. Our analysis shows that the distribution of D–P patterns is sensitive to the directness of productivity estimates in animal studies but not in plant studies. Analysis of D–P patterns should be based on direct productivity estimates of the studied organisms, especially in comparative meta‐analyses of communities from multiple trophic levels, where productivity is often affected nonlinearly by indirect factors or when complex feedback interactions are expected between productivity and diversity.     

Reproductive biology of the threatened golden galaxias Galaxias auratus Johnston and the influence of lake hydrology

Golden galaxias Galaxias auratus (31–235 mm fork length, L _F) were collected monthly from littoral habitats in Lakes Crescent and Sorell, Tasmania, Australia, between July 2000 and December 2002. Spawning habitats were identified and monitored in both lakes, and surveyed in Lake Crescent. Trends in gonado-somatic indices and reproductive stages of development indicated that gonad development in both sexes begins in midsummer and peaks in late autumn to early winter. Males mature at smaller sizes (50% at 52 mm L _F) than females (50% at 76 mm L _F), larger individuals are predominately females (95% of fish ≥138 mm L _F), and overall male to female ratios are female biased ( c . 1:2). Spawning occurs late autumn to early spring (water temperatures = 1·4–9·7° C) with peaks in spawning activity in winter (mean water temperatures <5° C). Demersal adhesive eggs ( c. 1·5 mm diameter) were found on cobble substrata ( c. 20–250 mm diameter) in littoral areas ( c. 0·2–0·6 m deep) and fecundity of fish 71–181 mm L _F ranged from 619 to 14 478 eggs. The rate of change in water level over the 20 days prior to monthly sampling was important in explaining the occurrence of spent fish and this accounted for temporal differences in spawning between the populations. Lake hydrology influences the reproductive cycle of G. auratus by possibly providing a stimulus for spawning and it controls the availability of spawning habitat in Lake Crescent. Seasonal hydrological cycles ( i.e. rises during late autumn to winter) and a minimum water level of 802·20 m Australian Height Datum in Lake Crescent during autumn (above which littoral areas of cobble substratum are inundated) are critical to G. auratus populations.     

Effect of Rotylenchulus reniformis on Yield and Nitrogen,Potassium, Phosphorus and Amino Acid Content of Seed of Glycine max

Soybean cultivars varied in their response and tolerance to low initial Rotylenchulus reniforrnis populations of 10,000 nematodes/3.8 liters of soil, but a high initial population of 25,000 consistently reduced yields on resistant and susceptible cultivars by an average of 33.1%. At the 10,000 nematode inoculum level, dry seed yields of Hood decreased while those of Pickett increased significantly. Generally, total phosphorus decreased 11.1 and 11.5% and potassium increased 5.9 and 4.5% in seeds harvested from plants receiving initial inoculum levels of 5000 and 10,000 nematodes/pot, respectively. Little change in the total nitrogen content in seed was noted. Leucine content of seeds from infected plants was slightly less than from noninfected plants.     

The role of parasitoids in evolution of habitat and larval food plant preference by three Pieris butterflies

This article attempts to explain that parasitoids provide the evolutionary pressure responsible for relationships between habitat use and larval food plant use in herbivorous insects. Three species of butterflies of the genus Pieris, P. rapae, P. melete, and P. napi use different sets of cruciferous plants. They prefer different habitats composed of similar sets of cruciferous plants. In our study, P. rapae used temporary habitats with ephemeral plants, P. melete used permanent habitat with persistent plants, although they also used temporary habitats, and P. napi used only permanent habitat. The choice experiment in the field cages indicated that each of the three butterfly species avoided oviposition on plants usually unused in its own habitat, but accepted the unused plants which grew outside its own habitat. Their habitat use and plant use were not explained by intrinsic plant quality examined in terms of larval performance. Pieris larvae collected from persistent plants or more long lasting habitats were more heavily parasitized by two specialist parasitoids, the braconid wasp Cotesia glomerata and the tachinid fly Epicampocera succincta. The results suggest that Pieris habitat and larval food plant use patterns can be explained by two principles. The evolution of habitat preference may have been driven by various factors including escape from parasitism. Once habitat preference has evolved, selection favors the evolution of larval food plant preferences by discriminating against unsuitable plants, including those which are associated with high parasitism pressures. Received: December 3, 1998 / Accepted: January 20, 1999     

Trace element levels in mollusks from clean and polluted coastal marine sites in the Mediterranean, Red and North Seas

The trace element contamination levels in mollusks were evaluated for different marine coastal sites in the Mediterranean (Israeli coast), Red (Israeli coast) and North (German coast) Seas. Three bivalve species (Mactra corallina, Donax sp, and Mytilus edulis) and two gastropod species (Patella sp.and Cellana rota) were sampled at polluted and relatively clean sites, and their soft tissue analyzed for Hg, Cd, Zn, Cu, Mn and Fe concentrations. Representative samples were screened for organic contaminants [(DDE), polychlorinated biphenyls PCBs and polycyclic aromatic hydrocarbons (PAHs)] which exhibited very low concentrations at all sites. In the Red Sea, the gastropod C. rota showed low levels of Hg (below detection limit) and similar Cd concentrations at all the examined sites, while other trace elements (Cu, Zn, Mn, Fe) were slightly enriched at the northern beach stations. Along the Mediterranean coast of Israel, Hg and Zn were enriched in two bivalves (M. corallina and Donax sp.) from Haifa Bay, both species undergoing a long-term decrease in Hg based on previous studies. Significant Cd and Zn enrichment was detected in Patella sp. from the Kishon River estuary at the southern part of Haifa Bay. In general, Patella sp. and Donax sp. specimens from Haifa Bay exhibited higher levels of Cd compared to other sites along the Israeli Mediterranean coast, attributed to the enrichment of Cd in suspended particulate matter. Along the German coast (North Sea) M. edulis exhibited higher concentrations of Hg and Cd at the Elbe and Eider estuaries, but with levels below those found in polluted sites elsewhere. Received: 25 February 1999 / Received in revised form: 22 April 1999 / Accepted: 30 April 1999     

离体血流循环切应力水平控制方法的研究

本文应用流体力学及血流动力学理论和分析方法,建立了离体心血管循环系统的切应力水平控制方法。并采用该方法研制可精确控制切应变水平的模拟在体血流动力学环境的层流流动装置,用于研究动力学因素对人工培养的内皮细胞生物学特性影响。     

Influence of resource level on maternal investment in a leaf-cutter bee (Hymenoptera: Megachilidae)

Fisher's (1930) prediction of equal investment for each sexin a panmictic population is influenced by a number of ecologicalfactors, among which resource availability plays a major role,particularly when the population exists under changing resource availability.Rosenheim et al. proposed a multifaceted parental investment modelbased on the underlying assumption that individual females determine theirsex investment according to resource availability and oocyte availabilityto maximize reproductive success. The model predicts that greater availabilityof resources used for provisions will lead to (1) an increasein the proportion of females produced (when the female is thelarger sex) and (2) an increase in the amount of provisionsper offspring and thus an increase in offspring size. I testedthese predictions by a controlled experiment using a leaf-cutterbee, Megachile apicalis. I presented two levels of food resourcesto the nesting females, which were allowed to forage and nestin cages. The experimental results supported these parentalinvestment model's predictions.     

High‐altitude adaptation in vertebrates as revealed by mitochondrial genome analyses

The high‐altitude environment may drive vertebrate evolution in a certain way, and vertebrates living in different altitude environments might have different energy requirements. We hypothesized that the high‐altitude environment might impose different influences on vertebrate mitochondrial genomes (mtDNA). We used selection pressure analyses and PIC (phylogenetic independent contrasts) analysis to detect the evolutionary rate of vertebrate mtDNA protein‐coding genes (PCGs) from different altitudes. The results showed that the ratio of nonsynonymous/synonymous substitutions (dN/dS) in the mtDNA PCGs was significantly higher in high‐altitude vertebrates than in low‐altitude vertebrates. The seven rapidly evolving genes were shared by the high‐altitude vertebrates, and only one positive selection gene (ND5 gene) was detected in the high‐altitude vertebrates. Our results suggest the mtDNA evolutionary rate in high‐altitude vertebrates was higher than in low‐altitude vertebrates as their evolution requires more energy in a high‐altitude environment. Our study demonstrates the high‐altitude environment (low atmospheric O₂ levels) drives vertebrate evolution in mtDNA PCGs.     

Analysis of precocious metamorphosis induced by application of an imidazole derivative to early third instar larvae of the silkworm,Bombyx mori

When an imidazole derivative (KK-42) was applied to day 1 third instar larvae of the silkworm, Bombyx mori, 100% underwent precocious metamorphosis at the end of the fourth instar. Thus, the fourth instar becomes the last instar in these KK-42–treated larvae. The endocrine systems underlying the precocious metamorphosis were analyzed in the present study. Hydroprene application during the prolonged third instar after KK-42 treatment can prevent precocious metamorphosis, and the results showed dose-dependent and stage-specific effects. From analysis of the developmental changes in ecdysteroid levels in both KK-42–treated larvae and KK-42– and hydroprene-treated larvae, we conclude that changes in JH levels during the third larval instar can modify the secretion pattern of prothoracic glands and that during the next larval instar, very low ecdysteroid levels during the early stages of the presumptive last (fourth) larval instar are directly related to precocious metamorphosis. Arch. Insect Biochem. Physiol. 36:349–361, 1997. © 1997 Wiley-Liss, Inc.     

A quantitative anharmonic analysis of the amide A band in α‐helical poly(L‐alanine)

Polarized ir spectra of oriented films of α‐helical poly(l ‐alanine) (α‐PLA) have been obtained as a function of residual solvent dichloroacetic acid (DCA). The amide A, B, II, and V regions exhibit multiple bands whose structure depends on the residual DCA content, and those associated with the α_I‐PLA structure have been identified. A calculation of the relevant cubic anharmonic force constants indicates that, contrary to previous assignments, the overtone of amide II(A) is in Fermi resonance with the NH stretch fundamental, whose unperturbed frequency we now find to be at 3314 cm⁻¹, significantly higher than the previously suggested 3279 cm⁻¹. The presence of a structure in addition to the standard α_I‐PLA is indicated by our analysis. © 1999 John Wiley & Sons, Inc. Biopoly 49: 195–207, 1999