Coevolution of the mammalian chemokines and their receptors

 A phylogeny of mammalian chemokines revealed two major clusters, corresponding to the CC and CXC chemokines; the C chemokines appeared to be more closely related to the former. In a phylogeny of chemokine receptors, there were also two major clusters: one containing CC chemokine receptors plus other receptors of unknown function and another containing CXC receptors and other receptors of unknown function. However, within the CC receptors, there was not a close correspondence between the phylogenies of chemokines and their receptors. The CC chemokines contained two major subfamilies: (1) the MIP subfamily (including MIP-1α, MIP-1β, and RANTES); and (2) the MCP subfamily (including MCP-1,-2,-3, and -4 and eotaxin). Receptors having preferred ligands in the MCP subfamily did not constitute a monophyletic group but rather evolved twice independently. Reconstruction of ancestral amino acid sequences suggested that these two groups of MCP receptors did not convergently evolve any amino acid residues; rather, they convergently lost sequence features found in the third and fourth extracellular domains of known receptors for MIP-subfamily chemokines. Received: 1 May 1998 / Revised: 3 July 1998     

Neighborhood density and reproductive potential in harvester ants

When neighbors compete for resources, the characteristics of a neighborhood may affect fitness. We examined the relationship between reproductive success and the density and size/age characteristics of neighbors in a population of the seed-eating ant, Pogonomyrmex barbatus, in which the ages of all colonies were known. Reproductive success was estimated by trapping and counting the number of alate, reproductive ants emerging from the nest for the annual mating flight. Alate production was negatively related to neighborhood density. Decreased production of alates by more crowded colonies may be due to competition for food with surrounding colonies. Neighbor size/age was unrelated to alate production. If alate production is correlated with lifetime reproductive success, these results suggest that selection favors colonies that monopolize more space, whatever the size of neighboring colonies. Received: 12 February 1996 / Accepted: 6 September 1996     

Identification of plastid genotypes in Oenothera subsect. Munzia by restriction fragment length polymorphisms (RFLPs)

 Five discrete plastid genotypes (plastomes), designated I–V and typified by Oenothera Hookeri, biennis, Lamarckiana, parviflora and argillicola respectively, have been previously characterized within the European subsect. Euoenothera. The evolutionarily more-derived plastome types (I, II and V) are generally less tolerant of new hybridization events than the ancestral types (III and IV), and were first identified based on their incompatibility reactions with standard hybrid nuclei. Restriction maps for all five plastomes are available for the enzymes PvuII, SalI, KpnI and PstI (Gordon et al. 1982). The present study employs PvuII and KpnI restriction digests to compare 28 of the 45 species of subsect. Munzia with Euoenothera plastomes I–V. The results of plastome RFLP fingerprinting show uniform divergence of the South American taxa from their European congeners; all share the previously documented 45-kb inversion in the large single-copy region reported by Hachtel et al. (1991). However, at least six new plastome types have evolved within subsect. Munzia, giving rise to small-fragment size differences of 0.1–0.7 kb. In two of these cases (Oe. featherstonei and Oe. longiflora) unique fragments occurred. For Oe. featherstonei the unique KpnI fragment resulted from a novel 2.2 kb insertion, whereas in Oe. longiflora an additional PvuII restriction site has been created. Received: 2 June 1998 / Accepted: 14 July 1998     

The reproductive potential of workers in slave-making ants

Summary Colonies of slave-making ants have been used repeatedly to test sex allocation theory. It was suggested that workers of slave-making ants are more strongly selected to reproduce than workers of related, non-parasitic species, because they are incapable of manipulating sex allocation and the sexualization of larvae in their colonies. I show here that in slave-making Formicoxenini, worker ovaries on average consist of significantly more ovarioles than in non-parasiticLeptothorax species. Similarly, whereas in mostLeptothorax species, workers form reproductive hierarchies and lay eggs only in orphaned colonies, slave-maker workers show antagonistic interactions already in the presence of the queen and at least in some species have been observed ovipositing in queen-right colonies. The significance of these results is discussed.     

Influence of small-scale disturbances by kangaroo rats on Chihuahuan Desert ants

Banner-tailed kangaroo rats (Dipodomys spectabilis) are prominent ecosystem engineers that build large mounds that influence the spatial structuring of fungi, plants, and some ground-dwelling animals. Ants are diverse and functionally important components of arid ecosystems; some species are also ecosystem engineers. We investigated the effects of patch disturbances created by D. spectabilis mounds on ant assemblages in a Chihuahuan Desert grassland in southern New Mexico by using pitfall traps in a paired design (mound vs. matrix). Although the disturbances did not alter species richness or harbor unique ant communities relative to the matrix, they did alter species composition; the abundances of 6 of 26 species were affected. The disturbances might also act to disrupt spatial patterning of ants caused by other environmental gradients. In contrast to previous investigations of larger-scale disturbances, we detected no effects of the disturbances on ants at the functional-group level. Whether ant communities respond to disturbance at a functional-group or within-functional-group level may depend on the size and intensity of the disturbance. Useful functional-group schemes also may be scale-dependent, however, or species may respond idiosyncratically. Interactions between disturbance-generating mammals and ants may produce a nested spatial structure of patches. Received: 11 October 1999 / Accepted: 11 March 2000     

Characteristics of genetic variation in the progenies of protoplast-derived plants of rice, Oryza sativa cv Nipponbare

Genetic variation in protoplast-derived rice (Oryza sativa L.) plants was characterized using first and second generation selfed progenies. A total of 133 regenerated plants were obtained from ten protoplasts of the japonica rice cultivar Nipponbare. Sixty two regenerated plants which set enough seeds for the subsequent field tests at the next generation and were derived from five protoplasts were selected, and their selfed seeds were used as the first selfed-seed progeny generation). Fifteen plants were selected from each of the 15 lines, and their selfed seeds were used for tests at the generation. Thirty seven lines (60%) segregated plants with detrimental mutant characters of yellow-green phenotype, dwarf stature, dense and short panicle, or low seed fertility. According to the segregation patterns in the lines having mutated plants among those originated from the same protoplasts, the stages of mutation induction were estimated. Additionally, five quantitative traits were changed in almost all and lines. Varied quantitative traits of heading date, number of spikelets per panicle, and seed fertility, were in a heterozygous state. However, culm and panicle lengths showed high uniformity, whereas reduced culm and panicle lengths were caused by mutational changes in polygenes and/or multiple genes. Received: 20 March 1996 / Accepted: 21 June 1996     

Effects of parasitic castration on plant resource allocation

It has been proposed that host castration is a parasite strategy to reallocate host resources from reproductive to vegetative functions to increase parasite fitness. Since resource partitioning between reproduction and vegetative growth can affect host life-history traits, parasite effects on resource allocation can affect both plant fitness and host-parasite coevolution. Field and greenhouse experiments were used to investigate the effects of host castration by the fungus Atkinsonella hypoxylon on the resource allocation and architecture of the grass Danthonia spicata. The results indicate that non-infected D. spicata can reallocate resources from reproduction to vegetative growth when resource allocation to reproduction is prevented. However, I found no evidence that fungal castration causes reallocation of resources from host reproduction to vegetative growth. Instead, infection reduces host biomass and the fungus directly utilizes resources that would have been used for host reproduction for its own reproduction. Received: 25 March 1999 / Accepted: 24 October 1999     

The herbivores’ dilemma: trade-offs between nutrition and parasitism in foraging decisions

An experiment was carried out using a trade-off framework to determine the rules of sward selection, in relation to gastrointestinal parasite dispersion, used by mammalian herbivores, and the effect of level of feeding motivation and parasitic status on these rules. Twenty-four sheep divided into four animal treatment groups resulting from two levels of feeding motivation (high and moderate) and two parasitic states (parasitised with Ostertagia circumcincta and non-parasitised) were presented with pairs of experimental swards which varied in N content (high and low), sward height (tall and short) and level of contamination with faeces and thus parasites (contaminated and non-contaminated). The selection for tall swards outweighed both the selection for N-rich swards and the avoidance of faecal contaminated swards. The selection for N-rich swards could not completely overcome faecal avoidance. Parasitism in animals with a moderate feeding motivation reduced their bite rates and grazing depths, thereby probably reducing the rate of ingestion of parasitic larvae. In contrast, highly feeding-motivated animals (including those parasitised) increased their bite rates and grazing depths, thereby increasing the rate of ingestion of parasites. The inclusion of parasite distributions, both in the environment and within herbivore host populations, is likely to advance optimal foraging theory by enhancing its predictive power. Received: 30 November 1999 / Accepted: 14 February 2000     

Host resistance and pathogen virulence across a plant hybrid zone

Hybridization between locally adapted plant populations has been postulated to have significant evolutionary consequences, and, in particular, may influence host-pathogen interactions with respect to resistance and virulence structure. This study investigated patterns of resistance and virulence in a hybrid zone between ”bog” and ”hill” ecotypes of the native Australian flax, Linum marginale, where the host is subject to attack by the rust pathogen, Melampsora lini. Analysis of the resistance structure of adjoining bog, hill and hybrid populations found that bog plants were generally susceptible to pathogen isolates taken from all these sites, but that hybrids exhibited resistance levels similar to the more resistant hill plants. Similarly, the virulence structure of rust isolates collected from the hybrid population was more similar to that of the hill isolates than the bog. Controlled crosses between bog and hill plants showed that crosses in one direction (bog females×hill males) were much more successful than the other. A multi-year reciprocal transplant study further indicated that bog plants had significantly higher survivorship than hill plants, regardless of site. It is suggested that likelihood of differential gene flow and survivorship for bog and hill plants may at least partially explain the maintenance of a relatively narrow hybrid zone. Received: 5 October 1999 / Accepted: 1 July 1999     

Flow cytometric analysis of the chromosomes and stability of a wheat cell-culture line

A rapidly growing, long-term suspension culture derived from Triticum aestivum L. (wheat) was synchronized using hydroxyurea and colchicine, and a chromosome suspension with chromosomes was made. After staining with the DNA-specific fluorochromes Hoechst 33258 and Chromomycin univariate and bivariate flow-cytometry histograms showed 15 clearly resolved peaks corresponding to individual chromosome types or groups of chromosomes with similar DNA contents. The flow karyotype was closely similar to a histogram of DNA content measurements of Feulgen-stained chromosomes made by microdensitometry. We were able to show the stability of the flow karyotype of the cell line over a year, while a parallel subculture had a slightly different, stable, karyotype following different growth conditions. The data indicate that flow cytometric analysis of plant karyotypes enables accurate, statistically precise chromosome classification and karyotyping of cereals. There was little overlap between individual flow-histogram peaks, so the method is useful for flow sorting and the construction of chromosome specific-recombinant DNA libraries. Using bivariate analysis, the AT:GC ratio of all the chromosomes was remarkably similar, in striking contrast to mammalian flow karyotypes. We speculate about a fundamental difference in organization and homogenization of DNA sequences between chromosomes within mammalian and plant genomes. Received: 24 April 1996 / Accepted: 24 May 1996     

The mapping of phytochrome genes and photomorphogenic mutants of tomato

The map positions of five previously described phytochrome genes have been determined in tomato (Lycopersicon esculentum Mill.) The position of the yg-2 gene on chromosome 12 has been confirmed and the classical map revised. The position of the phytochrome A (phy A)-deficient fri mutants has been refined by revising the classical map of chromosome 10. The position of the PhyA gene is indistinguishable from that of the fri locus. The putative phyB1-deficient tri mutants were mapped by classical and RFLP analysis to chromosome 1. The PhyB1 gene, as predicted, was located at the same position. Several mutants with the high pigment (hp) phenotype, which exaggerates phytochrome responses, have been reported. Allelism tests confirmed that the hp-2 mutant is not allelic to other previously described hp (proposed here to be called hp-1) mutants and a second stronger hp-2 allele (hp-2 ^j ) was identified. The hp-2 gene was mapped to the classical, as well as the RFLP, map of chromosome 1. Received: 24 May 1996 / Accepted: 14 June 1996     

Specifying the introgressed regions from H. argophyllus in cultivated sunflower (Helianthus annuus L.) to mark Phomopsis resistance genes

A method based upon targetting of intro-gressed markers in a Phomopsis-resistant line (R) of cultivated sunflower, issuing from a H. argophyllus cross was used to mark the Phomopsis resistance regions. Our study was based upon 203 families derived from a cross between an inbred line susceptible to Phomopsis (S1) and the introgressed resistant line (R). Families were checked for Phomopsis resistance level in a design with replicated plots and natural infection was re-inforced by pieces of contaminated stems. Thirty four primers were employed for RAPD analysis. Out of 102 polymorphic fragments between (S1) and H. argophyllus, seven were still present in (R) suggesting that they marked introgressions of H. argophyllus into (R). The plants were scored for the presence or absence of 19 fragments obtained from five primers, and the relationships between the presence/absence of fragments in plants and Phomopsis resistance/susceptiblity in the progenies was determined by using an analysis of variance. We found that at least two introgressed regions, as well as favourable factors from sunflower, contributed to the level of Phomopsis resistance in cultivated sunflower. Received: 28 June 1996 / Accepted: 5 July 1996     

Antennal muscles and fast antennal movements in ants

The antennal movements of eight ant species (subfamilies Ponerinae, Myrmicinae, and Formicinae) are examined by high-frequency videography. They show a wide range of antennal velocities which is generated by antennal muscles composed of particularly diverse muscle fibers. Fiber diameter, sarcomere length and histochemically assessed myosin ATPase activity suggest that some thin fibers are fairly slow, while the bulk of antennal muscle fibers show intermediate or fast properties. These morphological properties correlate with the antennal movement velocities measured for the respective species. Based on their morphology, the fibers that generate the fast antennal retraction in some trap-jaw ants appear particularly fast and comprise the shortest sarcomeres yet described (1.1 μm). Accepted: 2 January 1997     

Gliadin polymorphism in wild and cultivated einkorn wheats

To study the relationships between different species of the Einkorn group, 408 accessions of Triticum monococcum, T. boeoticum, T. boeoticum ssp. thauodar and T. urartu were analyzed electrophoretically for their protein composition at the Gli-1 and Gli-2 loci. In all the species the range of allelic variation at the loci examined is remarkable. The gliadin patterns of T. monococcum and T. boeoticum were very similar to one another but differed substantially from those of T. urartu. Several accessions of T. boeoticum and T. monococcum were shown to share the same alleles at the Gli-1 and Gli-2 loci, confirming the recent nomenclature that considers these wheats as different subspecies of the same species, T. monococcum. The gliadin composition of T. urartu resembled that of the A genome of polyploid wheats more than did T. boeoticum or T. monococcum, supporting the hypothesis that T. urartu, rather than T. boeoticum, is the donor of the A genome in cultivated wheats. Because of their high degree of polymorphism the gliadin markers may help in selecting breeding parents from diploid wheat germ plasm collections and can be used both to search for valuable genes linked to the gliadin-coding loci and to monitor the transfer of alien genes into cultivated polyploid wheats. Received: 8 July 1996 / Accepted: 12 July 1996     

Genetic relatedness among worker nestmates of three formicine slave-making ants

Summary We estimated genetic relatedness among worker nestmates of the facultative slave-making antFormica subnuda (28 colonies), and the obligate slavemakers F. subintegra (19 colonies) andPolyergus breviceps (14 colonies) using horizontal starch gel electrophoresis. Relatedness among nestmates was 0.42 inF. subnuda, 0.70 inF. subintegra, and 0.49 inP. breviceps on average. Relatedness ofF. subintegra workers did not differ significantly from 0.75 indicating that this species is monogynous, though some females may mate multiply. The estimates ofF. subnuda andP. breviceps were significantly lower than 0.75 and, consequently, colonies were polygynous and/or poly-androus. The inbreeding coefficients were close to zero in all species suggesting random mating. We suggest that owing to practical monogyny and obligate nature of its slavemaking,F. subintegra is a good species for tests of sex allocation theory.     

Characterization of spelt (Triticum spelta L.) forms by gel electrophoretic analyses of seed storage proteins. I. The gliadins

A comparison betweeen the electropherograms of the spelt and wheat cultivars showed specific differences in the gliadin band patterns which provided the possibility of a clear classification into spelt or wheat. A special nomenclature was developed to be able to improve the presentation of the gliadin band pattern of spelt, which is different from that of wheat. This nomenclature, however, has not yet been applied to other cereals. The gliadin band patterns were presented in a schematic form. As a parameter for comparison, idealized band patterns of both wheat and spelt were developed by comparing the proportions of the bands of all available types. When comparing the gliadin band patterns of the spelt cross-breeds with their corresponding parental generations, it was noted that the same parental bands were not always transmitted and that the cross-breeds showed differences in the intensity, mobility, occurrence, and the splitting of single bands. In general it can be said that the band pattern of the daughter generation – even in the examined and generations – is more similar to the band pattern of the mother than to that of the father, which proves a maternal effect. Received: 29 June 1996 / Accepted: 12 July 1996     

Genetic variance, coefficient of parentage, and genetic distance of six soybean populations

Plant breeders would like to predict which biparental populations will have the largest genetic variance. If the population genetic variance could be predicted using coefficient of parentage or genetic distance estimates based on molecular marker data, breeders could choose parents that produced segregating populations with a large genetic variance. Three biparental soybean {Glycine max (L.) Merr.} populations were developed by crossing parents that were closely related, based on pedigree relationships. Three additional biparental populations were developed by crossing parents that were assumed to be unrelated. The genetic variance of each population was estimated for yield, lodging, physiological maturity, and plant height. Coefficient of parentage was calculated for each pair of parents used to develop the segregating populations. Genetic distance was determined, based on the number of random amplified polymorphic markers (RAPD) that were polymorphic for each pair of parents. Genetic distance was not associated with the coefficient of parentage or the magnitude of the genetic variance. The genetic variance pooled across the three closely related populations was smaller than the genetic variance pooled across the three populations derived from crossing unrelated parents for all four traits that were evaluated. Received: 24 April 1996 / Accepted: 17 May 1996     

Highly polymorphic microsatellites of rice consist of AT repeats, and a classification of closely related cultivars with these microsatellite loci

Microsatellites consisting of AT repeats are highly polymorphic in rice genomes and can be used to distinguish between even closely related japonica cultivars in Japan. Polymorphisms of 20 microsatellite loci were determined using 59 japonica cultivars, including both domestic and modern Japanese cultivars. Although the polymorphisms of these 20 microsatellite loci indicated that the Japanese cultivars were genetically quite similar, microsatellites consisting of AT repeats showed high gene diversity even among such closely related cultivars. Combinations of these hypervariable microsatellites can be employed to classify individual cultivars, since the microsatellites were stable within each cultivar. An identification system based on these highly polymorphic microsatellites could be used to maintain the purity of rice seeds by eliminating contamination. A parentage diagnosis using 17 polymorphic microsatellite loci clearly demonstrated that plants which carried desired chromosome regions had been selected in breeding programs. Thus, these hypervariable microsatellites consisting of AT repeats should promote the selection of plants which carry desired chromosomes from genetically similar parents. Backcrossing could also help to eliminate unnecessary chromosome regions with microsatellite polymorphisms at an early stage in breeding programs. Received: 8 July 1996 / Accepted: 12 July 1996     

Comparative RFLP mapping of the chlorotoluron resistance gene (Su1) in cultivated wheat (Triticum aestivum) and wild wheat (Triticum dicoccoides)

Chlorotoluron is a selective phenylurea herbicide widely used for broad-leaved and annual grass weed control in cereals. Variation in the response to chlorotoluron (CT) was found in both hexaploid bread wheat (Triticum aestivum L.) and wild tetraploid wheat (Triticum dicoccoides KöRN.). Here, we describe the comparative mapping of the CT resistance gene (Su1) on chromosome 6B in bread and wild wheat using RFLP markers. In bread wheat, mapping was based on 58 F₄ single-seed descent (SSD) plants of the cross between a genotype sensitive to chlorotoluron, ‘Chinese Spring’ (CS), and a resistant derivative, the single chromosome substitution line, CS (‘Cappele-Desprez’ 6B) [CS (CAP6B). In T dicoccoides, mapping was based on 37 F₂ plants obtained from the cross between the CT-susceptible accession B-7 and the resistant accession B-35. Nine RFLP probes spanning the centromere were chosen for mapping. In bread wheat Su1 was found to be linked to α-Amy-1 (9.84 cM) and Xpsr371 (5.2 cM), both on the long arm of 6B, and Nor2 (2.74 cM) on the short arm. In wild wheat the most probable linkage map was Nor2-Xpsr312-Su1-Pgk2, and the genetic distances between the genes were 24.8cM, 5.3cM, and 6.8cM, respectively. These results along with other published map data indicate that the linear order of the genes is similar to that found in T. aestivum. The results of this study also show that the Su1 gene for differential response to chlorotoluron has evolved prior to the domestication of cultivated wheat and not in response to the development and use of chemicals.     

Genetic control of macro-and micro-environmental sensitivities in Populus

Understanding the genetic mechanisms for the phenotypic plasticity and developmental instability of a quantitative trait has important implications for breeding and evolution. Two clonally replicated plantations of two 3-generation inbred pedigrees derived from the highly divergent species Populus trichocarpa and P. deltoides were used to examine the genetic control of macro- and micro-environmental sensitivities and their genetic relationships with the trait mean across two contrasting environments. For all stem-growth traits studied, the trait mean had a higher broad-sense heritability (H²) level than macroenvironmental sensitivity, both with much higher values than microenvironmental sensitivity. Genetic correlation analyses indicated that the trait mean was more or less independent of macro- or micro-environmental sensitivity in stem height. Thus, for this trait, the genetic difference in response to the two environments might be mainly due to epistasis between some regulatory loci for plasticity and loci for trait mean. However, for basal area and volume index, pleiotropic loci might be more important for their genetic differences between the two environments. No evidence was found to support Lerner’s (1954) homeostasis theory in which macro- or micro-environmental sensitivity is the inverse function of heterozygosity. Received: 8 March 1996 / Accepted: 31 May 1996