Genetic analysis of morphological variability in three Plantago species with different mating systems

Summary Morphological variability in three Plantago species possessing different mating systems — P. Major, P. coronopus, and P. lanceolata — was analyzed. From each species several populations were analyzed. In comparing the species, it appeared that both the inbreeding P. major and the outbreeding P. lanceolata showed a high degree of morphological differentiation between populations. It was hypothesized that the absence of population differentiation for the species with a mixed mating system, P. coronopus, was caused by high adaptive plasticity. Plasticity is probably the predominant mechanism by which this species copes with different environments. There were considerable differences between populations within each species for their levels of variability and their heritabilities. It appeared that besides the influence of the mating system, selection may diminish morphological variability in the case of strong directional selection, especially in P. major and P. lanceolata.Grassland Species Research Group Publication No. 135     

Establishment of Plantago lanceolata L. and Plantago major L. among grass

Summary Establishment of Plantago lanceolata and P. major ssp major among grass was studied in a field experiment in which survival and selection on date of seedling emergence and plant size was investigated in relation to the vegetation structure. P. major — in contrast to P. lanceolata — was not able to establish itself in grass because of its lower competitive ability caused by later germination, smaller seedling size, and shorter leaves. In both species there was selection for early germination. For P. lanceolata a significant correlation was found between the strength of selection and the light climate, determined by the structure of the grass sward. Plants that germinated early were at an advantage because they were larger, especially the leaves, when compared with plants that germinated late. It seems likely that selection was mainly by competition for light. Contrary to expectation P. major-seedlings had a higher shade tolerance than those of P. lanceolata. The performance of both species is discussed in relation to their different life strategies.Grassland species research group publication no 142     

亚热带不同林龄杉木林叶-根-土氮磷化学计量特征

以亚热带地区湖南会同5、10、15、20、25年生杉木(Cunninghamia lanceolata)人工林的针叶、细根及土壤(0—15、15—30、30—45 cm)为研究对象,在测定植物叶、细根、土壤中全N、全P含量的基础上,探讨杉木人工林全生命过程叶-根-土N、P化学计量特征的变化,为其经营过程提供基础数据。研究结果表明:(1)林龄对土壤N、P含量及N∶P具有极显著的影响(P0.01)。土层对土壤N含量影响显著(P0.01)。各层土壤N、P含量随林龄呈先减后升的趋势,变化显著(P0.05),土壤N、P含量的最大值分别出现在成熟林、幼龄林阶段,最小值出现在中龄林阶段。土壤N∶P随林龄呈增加趋势,但变化不显著。(2)林龄、器官均对植物N、P含量及N∶P具有极显著的影响(P0.01)。叶和细根的N、P含量随林龄呈"V"字型的变化趋势,且变化显著(P0.05),叶和细根N、P含量的最大值均出现在幼龄林、成熟林阶段,最小值出现在中龄林阶段。杉木叶的N∶P随林龄无显著变化,细根的N∶P随林龄显著增加(P0.05),杉木叶和细根N∶P变化范围分别为11.79—14.86,9.00—22.89。(3)5个林龄杉木叶、细根、土的N、P含量均表现为叶细根土,且差异显著(P0.05)。叶与细根的N、P含量及N∶P均显著正相关(P0.05)。0—15 cm土壤N与植物叶、细根N无显著相关性,15—30、30—45 cm土壤N与植物叶、细根N在5、10年生时存在显著相关性(P0.05)。5个林龄杉木叶、细根、土壤之间的P含量及N∶P均存在显著相关性。这些结果说明:在杉木的生长过程中,植物叶、细根以及土壤中养分不断变化,叶、细根、土之间的N、P化学计量特征显示出一定的相关关系。     

Establishment of phosphate-solubilizing strains of Azotobacter chroococcum in the rhizosphere and their effect on wheat cultivars under green house conditions

A pot experiment was conducted in the green house to investigate the establishment of phosphate solubilizing strains of Azotobacter chroococcum, including soil isolates and their mutants, in the rhizosphere and their effect on growth parameters and root biomass of three genetically divergent wheat cultivars (Triticum aestivum L.). Five fertilizer treatments were performed: Control, 90 kg N ha^—1, 90 kg N + 60 kg P₂O₅ ha^—1, 120 kg N ha^—1 and 120 kg N + 60 kg P₂O₅ ha^—1. Phosphate solubilizing and phytohormone producing parent soil isolates and mutant strains of A. chroococcum were isolated and selected by an enrichment method. In vitro phosphate solubilization and growth hormone production by mutant strains was increased compared with soil isolates. Seed inoculation of wheat varieties with P solubilizing and phytohormone producing A. chroococcum showed better response compared with controls. Mutant strains of A. chroococcum showed higher increase in grain (12.6%) and straw (11.4%) yield over control and their survival (12—14%) in the rhizosphere as compared to their parent soil isolate (P4). Mutant strain M37 performed better in all three varieties in terms of increase in grain yield (14.0%) and root biomass (11.4%) over control.     

Suppression of the root rot–root knot disease complex by Pseudomonas aeruginosa in tomato: The influence of inoculum density,nematode populations,moisture and other plant-associated bacteria

The influence of different application rates of the plant growth-promoting rhizobacterium, Pseudomonas aeruginosa, population densities of the root-knot nematode, Meloidogyne javanica, moisture and other plant-associated bacteria in the suppression of root rot–root knot disease complex of tomato are described. The impact of these factors on bacterial rhizosphere and inner root and shoot establishment are also presented. The highest inoculum level of P. aeruginosa (7.4 × 10⁸ cfu ml^–1) in the presence of the lowest population density of M. javanica (500 J2/plant) caused the greatest reduction in gall formation due to M. javanica. The number of root–knot nematodes recovered from soil and roots treated with P. aeruginosa were also significantly reduced. Root infection caused by the soilborne root-infecting fungi Fusarium oxysporum, F. solani and Rhizoctonia solani was also effectively suppressed following application of P. aeruginosa. A P. aeruginosa-Bacillus subtilis treatment was the most effective in the suppression of root-rot disease complex with enhancement of plant growth. Biocontrol and growth promoting potential of the bacterium was enhanced when soil was kept at 50% or 75% moisture holding capacity, whereas a 25% MHC reduced bacterial efficacy. Rhizosphere population of P. aeruginosa declined drastically in P. aeruginosa-Bradyrhizobium japonicum treatments. Rhizosphere colonisation by P. aeruginosa seems to be governed by two factors: Initial inoculum size of the bacterium and severity of the root-knot disease. Endoroot and endoshoot colonisation of the bacterium was dependent on degree of root-colonisation by Fusarium oxysporum. An inoculum level 2.5 × 10⁸ cfu/ml of P. aeruginosa was optimal for the enhancement of plant growth, whereas inoculum below this level reduced plant growth.     

Comparative effects of Glomus mosseae and P fertilizer on foliar mineral composition of Acacia senegal seedlings inoculated with Rhizobium

Summary A factorial experiment with two controlled factors was conducted in the greenhouse with Acacia Senegal seedlings. The substrate was a degraded sandy soil (Dior soil) poor in available P (11 ppm — Olsen). The first controlled factor was soil sterilization, with two levels: (A) sterilized soil; (B) non-sterilized soil. The second factor was fertilization, with six levels: (1) uninoculated control; (2) inoculation with Rhizobium (ORS 1007); (3) inoculation with Glomus mosseae; (4) double inoculation with ORS 1007 and G. mosseae; (5) inoculation with ORS 1007 and 30 ppm phosphorus per plant; (6) inoculation with ORS 1007 and 60 ppm phosphours. The combination of the two factors and their levels led to 12 different plant treatments (A1–A6 and B1–B6). Compared to the control B1, the B5 and B6 treatments containing phosphorus increased: nodule dry weight about 7 times ; leaf dry weight about 4 times ; total N, P and Mg 4–5 times; total K and Ca 3–4 times. The mycorrhizal inoculation had the same positive effect on plant growth and mineral composition but with lower values. Plants inoculated with Rhizobium alone gave the lowest results. The A1 treatment gave lower values than B1. Foliar mineral contents varied within a narrow range (20–30%).     

Effects of rhizosphere soil,vesicular-arbuscular mycorrhizal fungi and phosphate onPlantago major L. ssp.pleiosperma Pilger

Biotic factors in the rhizosphere and their effect on the growth ofPlantago major L. ssp.pleiosperma Pilger (Great plantain) were studied. In a pot experiment the effect on shoot growth of the addition of 2.5% rhizosphere soil at four levels of phosphate was highly dependent on the availability of phosphate: a promoting effect at low phosphate levels was observed while a reducing effect occurred at higher phosphate levels. As the roots were infected with vesicular-arbuscular mycorrhizal (VAM) fungi in the treatment with rhizosphere soil, two other experiments were set up to separate effects of the indigenous VAM fungi from effects of the total rhizosphere population. The uptake of phosphate and shoot growth was not decreased at higher phosphate availability when VAM inoculum was added alone or in combination with rhizosphere soil. The growth reducing effect of the rhizosphere soil could therefore not be ascribed only to mycorrhizal infection. The results suggest that biotic factors in the rhizosphere soil affect the phosphate uptake ofPlantago major ssp.pleiosperma. This may, under conditions of phosphate limitation, lead to an increase of phosphate stress and, subsequently, a growth reduction. Futhermore, it is concluded that VAM fungi, as part of the rhizosphere population, may compensate this phosphate stress by enhancing the phosphate uptake.Grassland Species Research Group Publication No. 148.     

Biotic soil factors affecting the growth and development of Ammophila arenaria

Summary To study the origin of replant disease of Ammophila arenaria (L.) Link the growth and development in sand originating from the rhizosphere of a natural Ammophila vegetation was compared with the growth in sand from the sea-floor. In a greenhouse experiment, the growth of Ammophila seedlings in rhizosphere sand, when compared with that in sea sand, was significantly reduced. As sterilization by means of gamma-irradiation increased the biomass production of Ammophila seedlings significantly, it was concluded that the rhizosphere sand contained biotic factors that were harmful to Ammophila. In rhizosphere sand the roots of Ammophila were brown and poorly developed, and the specific uptake rates of N, P and K were reduced. The shoot weight proportion of the total plant dry matter was hardly influenced. In an outdoor experiment with Ammophila seedlings and cuttings, using both sands, the mortality was high and the plants were feeble in rhizosphere sand whereas plants in sea sand grew vigorously. It seems plausible that the plants in rhizophere sand were dessicated because the root system was shallow and badly developed. In the greenhouse experiments, Ammophila cuttings were less sensitive to the inhibiting factors in the rhizosphere than seedlings. This was confirmed in the outdoor experiment. Calammophila baltica (Fluegge ex Schrader) Brand, however, was hardly affected by the harmful biotic factors in the greenhouse. These results are discussed with reference to the ecology of Ammophila. It is assumed that the catching of fresh windblown sand provides Ammophila with a way to escape from harmful biotic soil factors, and it was concluded that degeneration of Ammophila is caused mainly by self-intolerance due to these biotic soil factors.     

Influence of Pluchea lanceolata (Asteraceae) on selected soil properties

Allelopathic interference may operate simultaneously, sequentially, and/or in combination with other mechanisms of interference such as nutrient interference. It is hypothesized that under field conditions, allelopathic plants may cause changes in chemical characteristics of soils in addition to qualitative and quantitative changes in the allelochemical status of soil infested with the allelopathic plant. To test this hypothesis, the perennial allelopathic weed Pluchea lanceolata was selected. A comparative study of P. lanceolata-infested soils, and soils 10, 20, 30, and 40 m away from the weed was undertaken to examine soil characteristics and quantitative and qualitative variation in soil phenolics. Impact of seasonal weather on the biotic and chemical characteristics of P. lanceolata, and quantitative variation in phenolics of weed-infested soils was also studied. Growth experiments were conducted to study the seasonal impact on allelopathic interference of P. lanceolata toward certain crop plants. Results indicate that P. lanceolata influences soil properties in addition to causing variation in soil phenolics. Two-way tests (i.e., analyzing allelopathic and nutrient interference) should be run regardless of whether one is studying allelopathy or nutrient interference and it is important to test allelopathy in all studies dealing with nutrient interference.     

模拟增温及隔离降雨对中亚热带杉木人工林土壤可溶性有机质的数量及其结构的影响

温度和水分影响森林生态系统的结构与功能,而全球变暖和降雨格局的改变是未来气候变化的趋势。我国中亚热带地区森林覆盖率大,碳库丰富,可溶性有机质(DOM)作为森林生态系统的重要组成部分,气候变化对它的数量和组成具有重要的影响。本文对我国湿润亚热带地区杉木人工林土壤进行模拟增温以及隔离50%的降雨试验,利用光谱技术手段研究增温及隔离降雨对土壤可溶性有机质(DOM)的数量及其结构的影响。试验设对照(CK)、增温(W)、隔离降雨(P)、增温与隔离降雨的交互作用(WP)4种处理。结果表明,与对照相比,土壤增温后,0—10cm和10—20cm土层的土壤可溶性有机碳(DOC)和可溶性有机氮(DON)增加,但其芳香性指数和腐殖化程度降低,增温加速DOM的流失,不利于土壤有机质的稳定。季节变化影响土壤的环境,导致隔离降雨有使DOM的数量增加或减少的趋势;在旱季(2014年10月和2015年1月),隔离降雨降低了土壤DOM的数量,但其芳香性指数和腐殖化程度增加,而进入雨季(2015年4月),隔离降雨有使DOM增加的趋势,但其组分中的芳香化合物较少。增温和隔离降雨的交互作用在一定程度上促进DOM的产生,其结构比对照简单。温度和降雨对DOM的影响较为复杂,在全球气候变化背景下,只有长期对其进行观测并探讨其他因素带来的影响才能深入了解气候变暖和降雨格局的变化对土壤碳、氮的影响。     

广西不同林龄杉木、马尾松人工林根系生物量及碳储量特征

为了解不同林龄杉木、马尾松人工林地地下根系生物量及碳储量特征,以广西杉木、马尾松主产区5个不同林龄阶段(幼龄林、中龄林、近熟林、成熟林、过熟林)的人工林为研究对象,采用全根挖掘法和土钻法获取标准木根系生物量、灌草根系生物量和林分细根生物量,并测定其碳含量,分析其不同林龄阶段地下根系生物量和碳储量分配特征。结果表明:杉木、马尾松林地下根系总生物量分别在9.06—31.40Mg/hm~2和7.91—53.40Mg/hm~2之间,各林龄阶段根系总生物量总体上呈现随林龄增加而增加的趋势,杉木林细根生物量随林龄的增加呈现出先减后增的趋势,马尾松呈现出逐渐减小的趋势;林分各层次根系碳含量表现为乔木灌木草本、细根;杉木、马尾松地下根系碳储量变化趋势与生物量变化趋势相同,杉木、马尾松林不同林龄阶段各层次根系和土壤细根总碳储量分别在7.56—21.97Mg/hm~2和8.86—29.95Mg/hm~2之间;地下根系碳储量总体上以乔木根系占优势,且随林龄的增大其比例呈增加的趋势。     

The use of carbon isotope ratios to evaluate legume contribution to soil enhancement in tropical pastures

Soil carbon distribution with depth, stable carbon isotope ratios in soil organic matter and their changes as a consequence of the presence of legume were studied in three 12-year-old tropical pastures (grass alone —Brachiaria decumbens (C₄), legume alone —Pueraria phaseoloides (C₃) and grass + legume) on an Oxisol in Colombia. The objective of this study was to determine the changes that occurred in the¹³C isotope composition of soil from a grass + legume pasture that was established by cultivation of a native savanna dominated by C₄ vegetation. The¹³C natural abundance technique was used to estimate the amount of soil organic carbon originating from the legume. Up to 29% of the organic carbon in soil of the grass + legume pasture was estimated to be derived from legume residues in the top 0–2-cm soil depth, which decreased to 7% at 8–10 cm depth. Improvements in soil fertility resulting from the soil organic carbon originated from legume residues were measured as increased potential rates of nitrogen mineralization and increased yields of rice in a subsequent crop after the grass + legume pasture compared with the grass-only pasture. We conclude that the¹³C natural abundance technique may help to predict the improvements in soil quality in terms of fertility resulting from the presence of a forage legume (C₃) in a predominantly C₄ grass pasture.     

毛竹各器官和根际土浸提液对杉木种子萌发的化感作用

随着毛竹杉木混交林面积的不断扩大,它们之间既会产生促进作用,又会产生抑制作用。本研究对比分析了不同浓度毛竹各器官(鲜叶、干叶、枝条、竹杆、竹鞭和鞭根)的浸提液及枯落物、根际土浸提液对杉木种子发芽率的影响,探讨了毛竹各器官浸提液及枯落物、根际土浸提液对杉木种子萌发的化感作用。结果表明:(1)处理前期,毛竹各器官浸提液对杉木种子萌发具有抑制作用,且当浸提液浓度为1∶25和1∶50的高浓度时,相对于低浓度浸提液对杉木种子萌发的抑制作用更为持久;(2)处理后期,低浓度的毛竹各器官浸提液对杉木种子萌发促进作用较快,而高浓度的浸提液仍呈现抑制作用,促进作用出现较为缓慢;(3)枯落叶浸提液总体上对杉木种子萌发具有抑制作用,在整个实验过程中低于对照组的发芽率,仅在1∶50浓度时略高对照组实验;而根际土浸提液对杉木种子萌发自始至终都具有促进作用,其中低浓度的促进作用十分显著。故在实际的毛竹杉木混交林生产营林过程中可选用毛竹根际土制备浸提液,促进杉木种子萌发,为毛竹杉木混交林的生产经营提供参考。     

Factors influencing population dynamics of Macrophomina phaseolina in arid soils

The quantitative determination of Macrophomina phaseolina population in an arid soil was carried out utilizing a selective medium. The population of the fungus increased under continuous monocropping with a susceptible host, but considerable reduction was recorded with crop rotation or a change in crop sequence. The effects of fungi, bacteria, actinomycetes, total microbial population, minimum and maximum soil temperature on the survival of M. phaseolina population were studied in the absence of a crop at different soil depths. Highest population and survival rates were recorded at 0–5 cm soil depth. Correlation and path coefficient analyses were carried out to determine the role of individual factors influencing M. phaseolina population. In winter months, low temperature and high actinomycete population were found to be the major factors governing the reduction of the population of M. phaseolina.     

Trichoderma spp. tolerance to Brassica carinata seed meal for a combined use in biofumigation

Biofumigation by Brassicaceae green manure or seed meal incorporation into soil is an ecological alternative to chemical fumigation against soil-borne pathogens, based on the release of glucosinolate-derived compounds. This study aimed at investigating the tolerance of the beneficial fungus Trichoderma to these compounds in view to combined utilization with Brassica carinata seed meal (BCSM). Forty isolates of Trichoderma spp. were tested in vitro for tolerance to toxic volatiles released by BCSM and in direct contact with the meal. They were found to be generally less sensitive than the assayed pathogens (Pythium ultimum, Rhizoctonia solani, Fusarium oxysporum), even if a fungistatic effect was observed at the highest dose (10 μmole of sinigrin). Most of them also were able to grow on BCSM and over the pathogens tested. A preliminary experiment of integrating BCSM with Trichoderma in soil was carried out under controlled conditions with the patho-system P. ultimum—sugar beet. BCSM incorporation increased pathogen population, but reduced disease incidence, probably due to indirect mechanisms. The greatest effect was achieved when BCSM was applied in combination with Trichoderma, regardless of meal ability to release isothiocyanate. These findings suggest that disease control can be improved by this integrated approach. This study also highlighted that a reduction of allyl-isothiocyanate concentration in soil could occur due to the activity of some Trichoderma isolates. This effect could protect resident or introduced Trichoderma isolates from depressing effects due to the biocidal compounds, but, on the other hand, could reduce the efficacy of biofumigation against target pathogens.     

不同林龄杉木人工林土壤C:N:P化学计量特征及其与土壤理化性质的关系

为了阐明林龄对杉木人工林土壤理化性质及碳氮磷(C∶N∶P)生态化学计量特征的影响,在福建农林大学三明莘口林场选取4个林龄(4, 20, 24, 33a)的杉木人工林为研究对象,测定0—20,20—40,40—60 cm深度土壤的水分-物理性质、pH、总碳(TC)、全氮(TN)、全磷(TP)、全钾(TK),探讨它们随林龄的变化及其与C∶N∶P化学计量比之间的关系,为杉木人工林持续经营管理提供科学依据。结果表明:(1)随着林龄的增加,质量含水量、田间持水量和毛管孔隙度先减小后增加,在20 a达到最小,TN和TP也有相似的变化趋势,但在24 a林分的深层土壤达到最小,TC和TK保持不变;(2)随着林龄的增加,C∶N保持不变,C∶P和N∶P在24 a成熟林达到最大,但只在20—60 cm达到显著差异;(3)TC与多数水分-物理性质及3个生态化学计量比显著相关,质量含水量和孔隙度与C∶N∶P生态化学计量比均显著相关,TP与C∶P和N∶P显著负相关。土壤物理性质与土壤养分循环存在一定关联,有机质与土壤结构及养分平衡的调节有关,研究区杉木林发育过程中土壤腐殖质化进程较缓慢,24 a成熟林杉木的生长受到土壤磷的限制,在杉木速生阶段适当增施磷肥,保证林木的良好生长,促进土壤与植物的良性养分循环。     

Cultural and Environmental Factors Affecting the Longevity of Escherichia coli in Histosols

The survival of Escherichia coli in organic soils (Histosols) was examined. The death rate of this organism in Pahokee muck was less than that observed in Pompano fine sand. The number of viable E. coli cells found in the muck was approximately threefold greater than that found in the sand following 8 days of incubation. The initial population of the coliform affected the death rate. The rate of loss of viability varied 100-fold when the population size decreased from 2.5 × 10⁷ to 3.4 × 10⁴. Other factors affecting the viability of E. coli in muck were aerobic versus anaerobic growth of the organism and moist versus flooded conditions in the soil. The greatest survival of the coliform was noted with anaerobically grown cells amended to flooded soil. That the observed decrease in E. coli viability in soil was the result of biotic factors was demonstrated with amendment of sterile soil with E. coli. When 1.1 × 10⁵ bacteria per g of soil were added to sterile muck, a population of 3.0 × 10⁷ organisms per g of soil developed over a 10-day period. The role of the protozoa in eradication of the coliform from the muck was indicated by a sixfold increase in the protozoan population in natural soil amended with E. coli. Higher organic matter content in a Histosol compared with a mineral soil resulted in an increased survival of the fecal coliforms. Biotic factors are instrumental in the decline in coliform populations, but the potential for growth of the coliform in the organic soil could extend the survival of the organism.     

Genetic variation in defensive chemistry in Plantago lanceolata (Plantaginaceae) and its effect on the specialist herbivore Junonia coenia (Nymphalidae)

To examine genetic variation in defensive chemistry within and between natural populations of Plantago lanceolata, we performed a greenhouse experiment using clonal replicates of 15 genotypes from each of two populations, from a mowed lawn and an abandoned hayfield. Replicates of each genotype were harvested for determinations of aboveground biomass and leaf chemical content either at the beginning of the experiment (initial controls), after exposure to herbivory by larvae of Junonia coenia, a specialist on P. lanceolata (herbivory treatment), or at the end of the experiment without exposure to herbivory (final controls). Allocation to the iridoid glycosides aucubin and catalpol and the phenylpropanoid glycoside verbascoside displayed significant genetic variation within and between populations, and differed with leaf age. Significant genotypextreatment interactions indicated genetic variation in response of leaf chemistry to the treatments. There was no evidence for a cost of allocation to chemical defense: genetic correlations within and between chemical pathways and between defensive chemicals and aboveground growth were positive or nonsignificant. Although iridoid glycosides are known to be qualitative feeding stimulants for J. coenia, multiple regression of larval survivorship on leaf chemical content and shoot biomass indicated that larvae had lower survivorship on P. lanceolata ge-notypes with higher concentrations of aucubin in the leaves. Larval survivorship was unaffected by levels of catalpol and verbascoside. Thus, although specialist herbivores may respond to defensive chemicals as qualitative feeding stimulants, they do not necessarily have higher fitness on plant genotypes containing higher concentrations of these chemicals.     

Population differences in larval hostplant use in the checkerspot butterfly, Euphydryas chalcedona

Larvae from two populations of Euphydryas chalcedona Doubleday & Hewitson (Nymphalidae) were reared on their own hostplant and that of the other population, in both pre-diapause and post-diapause instars. One population, Chico, uses Penstemon breviflorus Lindl. (Scrophulariaceae), and the other, Echo Lake, uses P. newberryi Gray. Growth rate and survival were determined for pre-diapause and post-diapause larvae from both populations on both plant species; and digestive efficiencies were calculated during the prediapause instars. The results showed that larvae from the two populations differed in their responses to the two plant species. Pre-diapause larvae from Chico performed equally well on both plant species—survival and digestive indices were not significantly different for two Penstemon species. In contrast, pre-diapause larvae from Echo Lake performed significantly worse on the non-hostplant—growth and survival were significantly lower on the non-host, P. breviflorus. In addition, comparison of digestive efficiencies for the two plants showed that larvae from Echo Lake digested P. breviflorus better than P. newberryi, but were significantly less able to convert P. breviflorus to body mass. In the post-diapause instars, larvae from Chico grew faster on the host than on the non-host. Larvae from Echo Lake grew quite slowly on both plant species and significantly more of the Echo Lake larvae returned to diapause instead of completing development.

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Résumé Des chenilles de deux populations d'E. chalcedona ont été élevées sur leur propre plante-hôte et sur celle de l'autre population, aux stades avant et après diapause. Les deux populations s'alimentent sur différentes espèces de Penstemon (Scrophulariaceae), et une population—Echo Lake—est monophage sur P. newberry, tandis que l'autre—Chico—utilise d'abord P. breviflorus, mais les chenilles après diapause sont trouvées sur au moins deux autres espèces de plantes. Les taux de croissance et de survie ont été déterminés pour des chenilles avant et après diapause pour les deux populations sur les deux plantes; les efficacités digestives ont été calculées sur les chenilles avant diapause.Les résultats ont montré que les chenilles des deux populations différaient par leur degré de spécialisation digestive sur leur plante hôte normale: les chenilles de Chico ont utilisé aussi bien les deux plantes, tandis que celles d'Echo Lake le faisaient significativement moins bien sur la plante non-hôte, par suite de l'inaptitude à la digérer. Ainsi la population oligophage est alimentairement moins spécialisée et plus capable de se débrouiller avec une plante non-hôte. Après diapause, les chenilles de Chico s'alimentaient significativement mieux sur plante hôte que non-hôte, ce qui était le cas aussi pour la population monophage. Dans l'ensemble, les chenilles de la population monophage semblaient moins capables de se débrouiller dans des conditions défavorables ou moins avantageuses.

     

Individual and group selection for productivity in Tribolium castaneum

Summary The usefulness of a non-random group selection method in the improvement of a character influenced by interactions among individuals has been experimentally tested in a population of Tribolium castaneum. The selected trait —number of adults produced in a fixed period of time —showed a clear increase after 11 generations of selection. This increase is related to a reduction in developmental time, and it was specific for the population structure in which selection was applied, vanishing when this structure was altered.