Genetic variability in Plantago species in relation to their ecology

Summary A survey of enzyme variability in several populations of Plantago major in the Netherlands has been made. Nine of 36 loci were found to be polymorphic. The most extensively studies population showed 7 polymorphic loci (19%). The average heterozygosity was 0.005, a low value since P. major is predominantly inbreeding; a first estimate of the outcrossing rate is only 10%. All nine variable loci show simple Mendelian inheritance, seven of them could be placed into four different linkage groups. Marked differences in allele frequencies were found between two subspecies: ssp. major and ssp. pleiosperma. Two enzyme loci possess subspecies-specific alleles, Pgm-1 and Got-1. The most likely explanation of this phenomenon is the existence of fitness differences, caused either by the enzyme loci themselves or by linked loci.Grassland Species Research Group Publication no. 14     

Genetic variability in Plantago species in relation to their ecology

Summary Populations of the three Plantago species P. major, P. lanceolata and P. coronopus were scored for allozyme variability. They showed normal variability levels compared with other, similar plant species. Differentiation among populations appeared to be rather low in comparison with other species, probably due to a considerable amount of long distance seed transport. In order to be able to make an analysis of small-scale gene flow, all (sub)populations were critically checked for the existence of population structure equilibrium. The allozyme variation was tested for neutrality by testing homogeneity of F values among loci: between populations (Lewontin-Krakauer test) and within populations. No systematic deviations from the prediction of the neutral theory could be established. From the population structure analyses, little gene flow in the species P. major (with high selfing levels) and P. coronopus could be concluded, whereas P. lanceolata showed relatively high levels of gene flow. The degree of homozygosity in the latter species was too high to explain with the available data. In P. coronopus, on the other hand, an unusually high number of heterozygotes were observed.Grassland Species Research Group Publication No. 73     

Genetic variability in Plantago species in relation to their ecology

Summary Twelve Plantago major plants, good representatives of their populations, appeared to be genetically different for several characters which are important for adaptation to the respective habitat conditions. These characters are: juvenile growth, leaf morphology, production of secondary rosettes, flowering time, seed production, seed size and adult leaf production. The adaptive value of some of these characters was investigated by transplantation experiments in the field and by intraspecific competition experiments. The roadside type of ssp. major was adapted to trampling by being erect and elastic. The lawn type of ssp. major was adapted to a short, frequently cut, vegetation by being prostrate and by producing leaves with short petioles throughout the growth season. In the natural situations in which ssp. pleiosperma occurs, growth rate and first-year seed production of this subspecies were considerably higher than that of ssp. major. In a number of experiments, F₁s and F₂s were included, derived from crosses between the original plants. The F₁s were generally rather well adapted to both parental habitats, whereas the F₂s appeared to be less fit. The various alternatives in spending resources relevant for fitness optimization in different habitats are discussed.Grassland Species Research Group Publication No. 93     

Analysis of allozyme variability in three Plantago species and a comparison to morphological variability

Summary The level of electrophoretic variability in three Plantago species, P. major, P. coronopus, and P. lanceolata, was analyzed in relation to their breeding systems and compared with their morphological variability. From each species several populations were analyzed. The outcrossing P. lanceolata had the highest level of electrophoretic variability and the lowest population differentiation. The inbreeding P. major showed the opposite: a low level of electrophoretic variability and a high population differentiation. P. coronopus, with an intermediate breeding system, had an intermediate level of variability and differentiation. In comparing the species, it appeared that P. coronopus and P. major showed good concordance in the distribution of both kinds of variability, each having only a slightly higher morphological than electrophoretic differentiation between populations. P. lanceolata showed a higher morphological than electrophoretic differentiation between populations. A comparison of populations, within species, revealed good concordance of electrophoretic and morphological variability only within P. coronopus, while some populations of the other two species had relatively lower morphological variability compared with electrophoretic variability.Grassland Species Research Group Publication No. 182     

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     

Genetic analysis of ecological relevant morphological variability in Plantago lanceolata L.

Summary Plants of an F₂ generation derived from crosses between two ecotypes of Plantago lanceolata L. had previously been studied in a greenhouse. In the present experiment, F₂ plants were transplanted into their original habitats (a hayfield and a pasture). Six allozyme loci were used as markers in the analysis of survival and performance of the segregating genotypes. Fitness differences between the plants were large enough to detect natural selection. In both transplantation sites selection appeared to operate, though in different ways. In the hayfield habitat directional selection was hypothesized and both survival and performance of the plants were related to genotype, with the genotypes originating from the hayfield almost always performing better. In the pasture habitat where the habitat is not uniform and unpredictable hazardous droughts occur, survival was nearly genotype independent and environmentally determined, whereas performance of the plants was genotype dependent. The expression of two morphological characteristics, number of leaves and leaf length, was often not in concordance with the greenhouse results and was contradictory in both sites. Expression of both characters in the field, therefore, appeared to be strongly dependent on the general performance and growth conditions of the plant and not on the genotype.Grassland Species Research Group Publication no. 143     

Growth reduction in Plantago lanceolata in relation to biotic factors in the soil environment

Summary To investigate the influence of soil-borne pathogens on the population biology of a grassland species in natural vegetation, soil samples were collected, partly disinfected or sterilized and then planted with Plantago lanceolata. Those on some of the untreated soils showed growth reduction due to a biotic factor in the soil. This growth reduction was not associated with the density of P. lanceolata plants at the sampling sites. It was only visible when differences in abiotic factors — especially nutrient levels —were eliminated. In the natural situation the nutritional status of the soil has a far greater impact than biotic soil factors. Micro-organisms harmful to Plantago roots are considered to be of minor importance in the distribution of the individuals in the P. lanceolata population studied.Study performed by Grassland Species Research Group No 113     

Population and species variation of minisatellite DNA in Plantago

Three Plantago species were surveyed for within- and between-population variation at DNA sequences detected with the M13 minisatellite probe. The levels and patterns of variation detected by this probe correspond to those expected from the mating systems of the species. The highly-selfing species P. major has a relatively low variability of minisatellite sequences within populations and considerable differentiation between populations. The outcrossing species P. lanceolata exhibits higher minisatellite variability within populations and moderate differentiation between populations. P. coronopus, with a mixed mating system, has levels of variation intermediate between P. major and P. lanceolata. The levels of variation within and between populations corresponds, in general, to the levels of allozyme variation determined in an earlier study. Mating system and population structure appear to have a major influence on M13-detected fragment variation.     

Genetic variability in Lycopersicon species and their genetic relationships

Summary Genetic diversity has to be described and measured in order to establish breeding strategies and manage genetic resources. It is also fundamental to develop a comparative intraspecific study before attempting to discuss and conclude any phylogenetic relationship. The genetic variability of Lycopersicon species was studied using starch gel electrophoresis of 11 enzymatic systems in a hierarchical fashion. The species with the greatest genetic variability are L. chilense, L. peruvianum and L. pennellii, mainly due to the within-line component. L. chmielewskii, L. parviflorum and L. pimpinellifolium show an intermediate total variability and their between-component clearly predominates over the within-component. The least variable species are L. cheesmanii and L. esculentum. Cluster analysis resulted in three main groups: one formed by the cultigen, L. pimpinellifolium, L. cheesmanii and L. peruvianum;another by two species with self-incompatibility systems, L. pennelli and L. chilense; and another by two autogamous species L. chmielewskii and L. parviflorum. With respect to L. esculentum the farthest related species is Solanum rickii and the closest, L. pimpinellifolium.     

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     

Genetic analysis of ecological relevant morphological variability in Plantago lanceolata L.

Summary Morphological variability was analysed in an F₂-generation derived from crosses between two ecotypes of Plantago lanceolata L. Six allozyme loci, localised in five linkage groups, were used as markers. For two marker loci, Got-2 and Gpi-1, segregations did not fit monogenic ratios. In the linkage groups to which these two loci belonged, male sterility genes appeared to be present. In these crosses, male sterility (type 3, as described by Van Damme 1983) may be determined by two recessive loci located in the linkage groups of Got-2 and of Gpi-1. Many correlations of morphological and life history characters with allozyme markers were observed. The quantitative trait loci did not appear to be concentrated in major gene complexes. Often many loci were involved, sometimes with effects opposite to those expected from the population values. Main effects of the linkage groups appeared to be more important than interaction effects in determining variability. It also appeared that there is a positive correlation between the number of heterozygous allozyme loci and generative growth.Grassland Species Research Group Publication No. 115     

Genetic analysis of ecologically relevant morphological variability in Plantago lanceolata L.

Summary Morphological variability was studied in two populations of Plantago lanceolata using diallel analysis. In each population, reciprocal crosses between all possible pairs of ten plants were made. In the greenhouse, six members of each family were grown and many characters were measured. Using the model of Cockerham and Weir, the contributions of the different genetic variance components were calculated. From earlier papers it was postulated in advance to what extent and by which effect the characters in both populations were genetically determined. The populations had been differentiated for life history and morphological characters, and varied also in the relative contribution of genetic components to variability. In the Merrevliet (Me) population, where strong biotic selection was assumed, low levels of additive-genetic variability were present and the relative dominance appeared to be high. The contrasting population, Westduinen (Wd), which is abiotically controlled and shows strong environmental variability, possessed higher levels of additive-genetic variability and lower levels of relative dominance. It is possible that differential natural selection has diminished additive-genetic variability to different extents in both populations: plasticity and environmental heterogeneity prevented the loss of additive-genetic variability in Wd, whereas in the stable population, Me, natural selection had the opportunity of not only changing the means of the characters but also of diminishing additive-genetic variability to a great extent.Grassland Species Research Group Publication No. 146     

Subcellular concentrations of sugar alcohols and sugars in relation to phloem translocation in <Emphasis Type="Italic">Plantago major,Plantago maritima</Emphasis>, <Emphasis Type="Italic">Prunus persica</Emphasis>, and <Emphasis Type="Italic">Apium graveolens</Emphasis>

Sugar and sugar alcohol concentrations were analyzed in subcellular compartments of mesophyll cells, in the apoplast, and in the phloem sap of leaves of Plantago major (common plantain), Plantago maritima (sea plantain), Prunus persica (peach) and Apium graveolens (celery). In addition to sucrose, common plantain, sea plantain, and peach also translocated substantial amounts of sorbitol, whereas celery translocated mannitol as well. Sucrose was always present in vacuole and cytosol of mesophyll cells, whereas sorbitol and mannitol were found in vacuole, stroma, and cytosol in all cases except for sea plantain. The concentration of sorbitol, mannitol and sucrose in phloem sap was 2- to 40-fold higher than that in the cytosol of mesophyll cells. Apoplastic carbohydrate concentrations in all species tested were in the low millimolar range versus high millimolar concentrations in symplastic compartments. Therefore, the concentration ratios between the apoplast and the phloem were very strong, ranging between 20- to 100-fold for sorbitol and mannitol, and between 200- and 2000-fold for sucrose. The woody species, peach, showed the smallest concentration ratios between the cytosol of mesophyll cells and the phloem as well as between the apoplast and the phloem, suggesting a mixture of apoplastic and symplastic phloem loading, in contrast to the herbal plant species (common plantain, sea plantain, celery) which likely exhibit an active loading mode for sorbitol and mannitol as well as sucrose from the apoplast into the phloem.     

Genetic variability and genomic divergence of Elymus repens and related species

Summary In order to study the genetic variation and phylogenetic relationship in Elymus repens, amplified fragment length polymorphism (AFLP) were used, together with sequence data for the nuclear gene phytochrome B, phyB, and the chloroplast ribosomal protein encoding gene rps4. A total of 83 collected E. repens samples, 3 E. repens reference samples and 18 related species accessions were analysed and compared with 13 GenBank sequences. AMOVA analysis revealed a moderate genetic differentiation between the populations of E. repens in the three Swedish provinces investigated, while no differentiation was observed due to landscape type. A moderate genetic differentiation was also found when samples from different fields in one province were compared to samples from a selected field. A common female origin was found in E. repens and seven other Elymus species, Pseudoroegneria spicata, Thinopyrum intermedium, T. junceum, Hordeum bogdanii and H. stenostachys. The latter two both harbour the H genome. Taken together, the data suggest that the Swedish E. repens population is slightly heterogeneous and comprises multiple origins of genome donors; a nuclear genome with contributions from Pseudoroegneria (St), Hordeum (H), Thinopyrum (E) and Y with an unknown donor together with a maternal genome donated from Pseudoroegneria.     

Genetic systems of six species ofPlantago (Plantaginaceae)

Investigation of the genetic system of six species ofPlantago has revealed striking differences in their breeding and meiotic systems.Plantago patagonica is an inbreeder on account of preanthesis cleistogamy, whereasP. lanceolata is an obligate outbreeder, as it is self-incompatible.Plantago drummondii, P. lagopus, P. ovata, andP. major show mixed mating but in varying proportions. In terms of their energy budgets, outbreeding species invest more in floral advertisement and male function, while inbreeders invest more in female function. The contribution of the meiotic system to genetic variability, as revealed through recombination index, is more important in the inbreeding species.     

Genetic variability for esterase enzyme in Onobrychis species

Summary Understanding polymorphism at the enzyme level is basic to its use in population and genetic studies. However, no such information is available on the variability among different sainfoin (Onobrychis) species. Therefore, our objective was to study the existence of genetic polymorphism for esterase in 17 Onobrychis species and three cultivars of O. viciifolia Scop. Three regions of banding were observed in all the materials tested, with the number of bands varying from 0 to 3, 3 to 14, and 1 to 2 bands in each of these zones, which have been designated EST1, EST2, and EST3 respectively. All the materials studied had unique banding patterns, the only common feature being that all of them, except one species, had isozyme 1. Identification was possible only for four species (O. iberica, O. kachetica, O. transcaucasica, and O. bieberstenii) and one cultivar (Nova) based on the banding patterns. Large diversity was evident from the wide range of percent similarity values (0%–79%). Subsequent studies should be directed in using these isozyme banding patterns as markers to the desirable agronomic and quality traits of different germplasm lines.This work was supported by USDA Specific Cooperative Agreement No. 58-7MN1-8-143 from the Plant Stress and Water Conservation Unit, USDA-ARS, Lubbock, Texas. Joint contribution of the Texas Tech University, Lubbock, Texas and the USDA-ARS. TTU Journal no. T-4-302     

Pressurized gas transport in two Japanese alder species in relation to their natural habitats

Oxygen uptake measurements have shown that pressurized gas transport, resulting from the physical effect of thermo-osmosis of gases, improves oxygen supply to the roots of the seedlings in two alder speciesAlnus japonica (Thunb.) Steud. andAlnus hirsuta (Spach) Rupr., which are both native in Japan. When gas transport conditions were established by irradiation of the tree stems the internal aeration was increased to a level nearly equal to the oxygen demand of the root system in leafless seedlings ofA. hirsuta, but was higher inA. japonica so that excess oxygen was excreted into the environment. An increase of superoxide dismutase (SOD) activity, which protects plants from toxic oxygen radicals and post-anoxic injury, has been observed in root tissues ofA. japonica when the seedlings were flooded for 3 days. The increase of SOD activity, in concert with high gas transport rates, may enable this tree species to grow in wet sites characterized by low oxygen partial pressure in the soil and by varying water tables. A less effective gas transport, flood-induced reduction of SOD activity in root tissues, and reduced height growth in waterlogged soil may be responsible for the fact thatA. hirsuta is unable to inhabit wettland sites.     

Allozyme variability and phylogenetic relationships in the cultivated potato (Solanum tuberosum) and related species

Gene frequencies at 13 isozyme loci were determined in three South American taxa of cultivated potatoes [the diploid group (gp.) Stenotomum, the diploid subgroups (subgp.) Goniocalyx, and the tetraploid gp. Andigena ofS. tuberosum], in the diploid weed speciesS. sparsipilum, and in most of the main cultivars now raised in the Northern Hemisphere (the tetraploid gp. Tuberosum ofS. tuberosum). High levels of genetic variability (mean number of alleles per locus, percentage of polymorphic loci, and mean heterozygosity) were detected, being higher in tetraploid potatoes. An equilibrium among the evolutionary factors which increase genetic variability and artificial selection for maximum yield would explain the high uniformity of heterozygosity values we observed in both Andigena (0.36 ± 0.02) and Tuberosum (0.38 ± 0.01) cultivars.—The low value of genetic distance (D = 0.044) between Stenotomum and Goniocalyx does not support the status of species forS. goniocalyx.—In most isozyme loci, the electromorphs of gp. Andigena were a combination of those found in both gp. Stenotomum andS. sparsipilum, suggesting an amphidiploid origin of gp. Andigena from that two diploid taxa. The presence in Andigena of unique electromorphs, which were lacking in both gp. Stenotomum andS. sparsipilum, suggests that other diploid species could be also implied in the origin of tetraploid Andean potatoes. Furthermore, since Andigena were more related to Stenotomum (D = 0.052) than toS. sparsipilum (D = 0.241), the autopolyploidization of Stenotomum individuals and the subsequent hybridization with gp. Andigena may also have occurred. Thus, our study suggests a multiple origin (amphidiploidy, autoploidy, and hybridization at tetraploid level) of gp. Andigena.—Most of the electromorphs of gp. Tuberosum were also found in gp. Andigena; both the direct derivation of that group from the Andean tetraploid potatoes and the repeated introgression provided by breeding programmes could explain this result. However, the allele c of Pgm-B, present in 30 out of 76 Tuberosum cultivars from Northern Hemisphere as well as in 3 Chilean Tuberosum cultivars, lacks in the 258 Andigena genotypes sampled, suggesting that Chilean germplasm could have taken part in the origin of at least the 39% of the potato cultivars from Europe and North America analyzed here.—The distanceWagner procedure provides an estimate of a 30% of heterogeneity in the evolutionary divergence shown by different groups of cultivated potatoes. Diploid groups show a higher (22.5%) evolutionary rate than tetraploids, which can be attributed to both tetrasomic inheritance and facultative autofecundation that exists in Andigena and Tuberosum groups. Thus, artificial selection acting since 10000 years has not resulted in a higher rate of molecular evolution at the isozyme level in the tetraploids.     

Genetic pollution and number of matings in a black honey bee (Apis mellifera mellifera) population

Summary In the south-east of France, local honey bees possess only the B allele at the MDH locus, whereas the races which are usually imported into this area do not have this allele. The proportion of non-B genes in a sample of drones was used to measure the genetic pollution in the local population. Within the course of a breeding scheme of local bees, 99 queens, whose genotypes are BB, were naturally mated between April 25 and June 10, 1985 at la Tave (Gard, France). Twenty daughters-workers of each queen were analysed at the MDH locus. The frequency of the B allele in drones that mated with these queens is estimated by the proportion of workers with genotype BB and the genetic pollution by the cumulated frequency of the other alleles. The sampling variances of these frequencies involve a coefficient which is a function of the average number of drones mated with a queen. This latter parameter is estimated through the maximum likelihood method. In addition to the three well-known alleles, a rare allele (frequency=0.0055), possibly equivalent to the S1 allele described by Badino et al. (1983), has been found in three different colonies. Cumulating the frequencies of the non-B alleles results in an estimation of the genetic pollution equal to 0.0394 (±0.0071). This low value allows us to proceed to the next step of the selection project. The mean number of drones mated to a queen is 12.4 with a (10.4–19.3) confidence interval at the 90% level.     

Sea turtle species vary in their susceptibility to tropical cyclones

Severe climatic events affect all species, but there is little quantitative knowledge of how sympatric species react to such situations. We compared the reproductive seasonality of sea turtles that nest sympatrically with their vulnerability to tropical cyclones (in this study, “tropical cyclone” refers to tropical storms and hurricanes), which are increasing in severity due to changes in global climate. Storm surges significantly decreased reproductive output by lowering the number of nests that hatched and the number of hatchlings that emerged from nests, but the severity of this effect varied by species. Leatherback turtles (Dermochelys coriacea) began nesting earliest and most offspring hatched before the tropical cyclone season arrived, resulting in little negative effect. Loggerhead turtles (Caretta caretta) nested intermediately, and only nests laid late in the season were inundated with seawater during storm surges. Green turtles (Chelonia mydas) nested last, and their entire nesting season occurred during the tropical cyclone season; this resulted in a majority (79%) of green turtle nests incubating in September, when tropical cyclones are most likely to occur. Since this timing overlaps considerably with the tropical cyclone season, the developing eggs and nests are extremely vulnerable to storm surges. Increases in the severity of tropical cyclones may cause green turtle nesting success to worsen in the future. However, published literature suggests that loggerhead turtles are nesting earlier in the season and shortening their nesting seasons in response to increasing sea surface temperatures caused by global climate change. This may cause loggerhead reproductive success to improve in the future because more nests will hatch before the onset of tropical cyclones. Our data clearly indicate that sympatric species using the same resources are affected differently by tropical cyclones due to slight variations in the seasonal timing of nesting, a key life history process.