Dynamics of cuticular chemical profiles of Polistes dominulus workers in orphaned nests (Hymenoptera, Vespidae)

We analysed changes in cuticular hydrocarbon signatures of workers in orphaned colonies of the paper wasp Polistes dominulus. In natural conditions, workers and foundresses possess characteristic cuticular signatures, and foundresses are further distinguishable, both behaviourally and chemically, on the basis of their rank in a reproductive dominance hierarchy. In our study, several workers were found to develop their ovaries and produce cuticular signatures resembling those of dominant foundresses, while remaining workers possessed undeveloped ovaries and had cuticular blends characteristic of subordinate foundresses. Workers that did not develop their ovaries had changed epicuticular signatures, demonstrating that the mixture of hydrocarbons of worker individuals is strongly dependent on social role and environment. Our results suggest that the composition of epicuticular lipids is not determined at the pre-imaginal stage, and that physiological pathways leading to cuticular chemical changes are similar in foundresses and workers of P. dominulus.     

A new role for antennation in paper wasps (Hymenoptera,Vespidae): antennal courtship and sex dimorphic glands in antennomeres

Summary. Males of Polistes dominulus perform antennal vibrations and grasping of female antennae during pre-copulatory and copulatory phases. Male antennation plays a relevant role in mating success. In several antennomeres of males of P. dominulus and Vespa crabro, a further species in which we observed male antennation, we found secretory cells of class 1 and 3 associated to the same release site. In P. dominulus, class 3 cells with ampulla-like reservoirs and class 1 cells release their secretion through hairless multiporous areas. In V. crabro, tyloid-like structures are associated with large apodemes. The as yet unidentified secretion of these glands may act as a contact or low-volatile sex pheromone during courtship behaviour.Received 4 December 2003; revised 16 August 2004; accepted 7 September 2004.     

RFLP variation and genealogical distance,multivariate distance,heterosis, and genetic variance in oats

Patterns of restriction fragment length polymorphisms (RFLPs) have been proposed as estimators of genetic diversity among breeding lines and as predictors of heterosis and genetic variance. We evaluated these proposals by using a set of nine elite oat lines crossed in a diallel mating design without reciprocals. RFLP analysis was conducted using HindIII-digested DNA and a total of 107 probes from three different sources: 14 heterologous wheat cDNA clones, 17 oat genomic clones, and 76 oat cDNA clones. Of the 77 probes that produced high-quality autoradiographs, 26 detected polymorphisms among this set of lines, with an average of 2.6 variants per probe. RFLP-based genetic distance (FD) was calculated from these data by using Nei and Li's measure of genetic similarity, and was compared with two other measures of genetic divergence. Genealogical distance (GD ^*) was obtained from the coefficients of parentage based on known parental pedigrees, and multivariate distance (DI) was calculated by using the first five principal components of the parental correlation matrix for 12 agronomic traits. FD was significantly correlated with GD ^* (r=0.63, P<0.01), but not with DI (r=-0.05). Cluster analysis based on these three distance estimates did not produce equivalent groupings, but the FD and GD ^* clusters were more similar to each other than to the DI clusters. These results indicate that: (1) sufficient variation exists for further application of RFLP technologyto oats, (2) RFLPs could provide accurate estimates of genetic divergence among elite oat lines, and (3) it is unlikely that dispersed markers can predict heterosis or population genetic variance in oats. Further investigations will require more parental lines, a larger set of markers, and more information on the linkage relationships between RFLP markers and loci controlling the trait of interest.Journal paper No. J-15302 of the Iowa Agriculture and Home Economics Experiment Station, Ames, IA 50011, USA. Project No. 2818 and 2447. Supported by Quaker Oats grant to M. Lee     

Rank and epicuticular hydrocarbons in different populations of the paper wasp <Emphasis Type="Italic">Polistes dominulus</Emphasis> (Christ) (Hymenoptera,Vespidae)

Summary Several studies of social insects have shown that epicuticular hydrocarbons are involved in recognition. The hypothesis is that the animals can use differences in chemical composition to acquire information about conspecific status (sex, colony, reproductive status or caste recognition).In this study, we searched for differences between the epicuticular profiles of alpha and beta co-foundresses in Polistes dominulus (Christ) colonies from three separate localities. Our aim was to identify specific compounds or sets of compounds which could be general indexes of foundress rank position in an associative foundation.We found quantitative and qualitative differences in the epicuticular profile among the three populations. The compounds that differentiate between alpha foundresses and their subordinates in the two neighbouring localities were not the same as in the third population. However, in all localities the alpha foundresses of each associative foundation presented a higher proportion of heavy compounds than their respective subordinates. Chemical differences related to rank position may be a fertility signal and are probably caused by physiological and behavioural characteristics, although it is not yet certain if they are actually used by the wasps.Received 28 November 2003; revised 22 February 2004; accepted 25 February 2004.     

Blochmannia endosymbionts and their host, the ant Camponotus fellah: cuticular hydrocarbons and melanization

Carpenter ants (genus Camponotus) have mutualistic, endosymbiotic bacteria of the genus Blochmannia whose main contribution to their hosts is alimentary. It was also recently demonstrated that they play a role in improving immune function as well. In this study, we show that treatment with an antibiotic produces a physiological response inducing an increase in both the quantity of cuticular hydrocarbons and in the melanization of the cuticle probably due to a nutritive and immunological deficit. We suggest that this is because it enhances the protection the cuticle provides from desiccation and also from invasions by pathogens and parasites. Nevertheless, the cuticular hydrocarbon profile is not modified by the antibiotic treatment, which indicates that nestmate recognition is not modified.     

Variation in cuticular hydrocarbon signatures, hormonal correlates and establishment of reproductive dominance in a polistine wasp

In many social insects the relationship between reproductive dominance and physiological correlates is poorly understood. Recent evidence now strongly suggests that cuticular hydrocarbons are important in reproductive differentiation in these societies where they are used as signals of ovarian activity in reproductive females. In this study we investigated the relationship between reproductive dominance, size of the corpora allata (CA, producer of Juvenile Hormone, JH) and the proportions of cuticular hydrocarbons present on the cuticle in overwintering foundresses and both associative (polygynous) and solitary (monogynous) pre-emergence colonies of the social wasp Polistes dominulus. Size of the CA was positively correlated with ovarian development in polygynous colonies. In contrast, solitary foundresses possessed significantly smaller CAs than dominant foundresses from polygynous nests, yet ovarian activity was similar for both female types. CA size variation was associated with variation in cuticular hydrocarbon proportions. Overwintering, solitary, dominant and subordinate (from associative nests) females all possessed distinctive cuticular chemical profiles revealed by multivariate discriminant analyses. Our data indicate that the social environment strongly affects reproductive physiology in this wasp, and we discuss the role of cuticular hydrocarbons in reproductive signaling in P. dominulus and other social insects.     

Dissimilar patterns of genetic variation in two insular endemic plants sharing species characteristics,distribution, habitat,and ecological history

Camssonia guadalupensis ssp. clementina (Onagraceae) and Cryptantha traskiae (Boraginaceae) share many species characteristics that affect levels and pattern of genetic variation. In addition, they have a similar distribution, are found in the same habitat, and share ecological history by virtue of co-occurring at nearly all of the locations at which they are found. All populations of the two taxa on San Clemente Island were surveyed for genotypes at 16 allozyme loci, revealing generally low levels of genetic variation. However, Cam. g. clementina has more genetic variation than Cryp. traskiae at the taxon level (P = 37.5 versus 18.8, A = 1.69 versus 1.31, and H_E = 0.088 versus 0.003) and significantly more alleles and higher heterozygosity within populations (A = 1.09 versus 1.03, A_E = 1.02 versus 1.00; H_O = 0.013 versus 0.001 and H_E = 0.017 versus 0.003). Some populations of each taxon are monomorphic at all loci. Much greater differentiation among populations occurs in Cam. g. clementina (G_ST = 0.810) than in Cryp. traskiae (G_ST = 0.042). Locations of the more variable populations of each taxon do not coincide, and the pattern of genetic similarity of localities differs in the two taxa. Striking population genetic differences exist between these taxa despite shared species characteristics, distribution, habitat, and recent history.     

Quantitative genetic analysis suggests causal association between cuticular hydrocarbon composition and desiccation survival in Drosophila melanogaster

Survival to low relative humidity is a complex adaptation, and many repeated instances of evolution to desiccation have been observed among Drosophila populations and species. One general mechanism for desiccation resistance is Cuticular Hydrocarbon (CHC) melting point. We performed the first Quantitative Trait Locus (QTL) map of population level genetic variation in desiccation resistance in D. melanogaster. Using a panel of Recombinant Inbred Lines (RILs) derived from a single natural population, we mapped QTL in both sexes throughout the genome. We found that in both sexes, CHCs correlated strongly with desiccation resistance. At most desiccation resistance loci there was a significant association between CHCs and desiccation resistance of the sort predicted from clinal patterns of CHC variation and biochemical properties of lipids. This association was much stronger in females than males, perhaps because of greater overall abundance of CHCs in females, or due to correlations between CHCs used for waterproofing and sexual signalling in males. CHC evolution may be a common mechanism for desiccation resistance in D. melanogaster. It will be interesting to compare patterns of CHC variation and desiccation resistance in species which adapt to desiccation, and rainforest restricted species which cannot.     

RFLP analysis of phylogenetic relationships and genetic variation in the genus Lycopersicon

Summary Forty single-copy, nuclear probes of known chromosomal position were used to examine restriction fragment length polymorphism in the tomato genus Lycopersion. The probes were from three libraries: one cDNA, and two genomic libraries ne genomic made with EcoRI and the other with PstI. Total DNA from 156 plants representing eight species was cut with five different restriction enzymes and scored in 198 probe-enzyme combinations. Genetic distances between accessions (populations) and species were calculated from the resultant restriction patterns and proportion of shared bands. Accessions belonging to the same species largely clustered together, confirming their current classification. However, one mountain accession, classified as L. peruvianum var. humifusum (LA2150), was sufficiently distinct from the other accessions of L. peruvianum that it may qualify as a separate species L. esculentum and L. pimpinellifolium were the least clearly differentiated, possibly reflecting introgressive hybridization, known to have been promoted by man in recent history. Dendrograms constructed from cDNA versus genomic clones were nearly identical in their general grouping of species. The dendrograms revealed two major dichotomies in the genus: one corresponding to mating behavior [self-compatible (SC) versus self-incompatible (SI) species] and the other corresponding to fruit color (red versus green-fruited species). The ratio of withinversus between-accession diversity was much lower for SC species, indicating that most of the diversity within these species exists between populations, rather than within populations. Overall, the amount of genetic variation in the SI species far exceeded that found in SC species. This result is exemplified by the fact that more genetic variation could be found within a single accession of one of the SI species (e.g., L. peruvianum) than among all accessions tested of any one of the SC species (e.g., L. esculentum or L. pimpinellifolium). Results from this study are discussed in relationship to germ plasm collection/utilization and with regard to the use of RFLPs in tomato breeding and genetics.     

The impact of genetic parental distance on developmental stability and fitness in Drosophila buzzatii

Measures of genetic parental distances (GPD) based on microsatellite loci (D (2) and IR), have been suggested to be better correlated with fitness than individual heterozygosity (H), as they contain information about past events of inbreeding or admixture. We investigated if GPD increased with increasing genetic divergence between parental populations in Drosophila buzzatii and if the measures indicate past events of admixture. Further we evaluated the relationship between GPD, fitness and fluctuating asymmetry (FA) of size and shape. We investigated three populations of Drosophila buzzati, from Argentina, Europe and Australia. From these populations two intraspecific hybridisation lines were made; one between the Argentinean and European populations, which have been separated 200 years and one between the populations from Argentina and Australia, which have been separated 80 years. By doing this we obtained hybrid progeny having different levels of GPD. We found that D (2) and H can be used as indicators of admixture when comparing hybrid individuals with their parentals. IR was not informative. Our results does not exclude the presence of genetic fitness correlations (GFC) over individuals with a broad fitness range from populations in equilibrium, but we doubt the presence of GFC using GPD measures in admixed populations. Shape FA could be a relevant measure for fitness, however, only when comparing populations, not at individual level.     

Resistance to 16 diverse species of herbivorous insects within a population of goldenrod,Solidago altissima: genetic variation and heritability

Summary Genetic variation in resistance to 16 species of herbivorous insects was studied in 18 clones of Solidago altissima growing in an old field near Ithaca, New York, USA. Resistance to each insect, defined as the abundance of a species attacking a particular host genotype relative to other genotypes, was measured in both the natural stand and in two experimental gardens. The heritability of resistance was estimated by parent-offspring regression and sibcorrelation. The primary result was that clones differed in resistance to 15 of 16 insect species. The resistance of genotypes to these insect species remained relatively constant over the four years of the study. However, for only 10 of these resistances were the heritability estimates significantly different from zero. Thus the common assumption of plant-insect studies — that phenotypic variation in insect abundance is closely correlated with underlying genetic variation — is only conditionally true. There is heritable variation in resistance to many insects, but not all. The insects for which we observed heritable variation in plant resistance represent five different orders and several functional groups, including leaf chewers, phloem and xylem feeders, and gall formers. There was no apparent pattern between the degree of heritability of plant resistance and the destructiveness, feeding method, breadth of host range, or taxonomic group of the insects. The lack of marked heritable variation in resistance to some insects may be the result of (a) reduced variation caused by strong selection during prolonged or repeated insect outbreaks, and (b) genotype-environment interactions that obscure differences among genotypes.     

Mitochondrial DNA divergence in yoshinobori gobies (Rhinogobius species complex) between the Bonin Islands and the Japan–Ryukyu Archipelago

To investigate the genetic differentiation between the Bonin (Ogasawara) Islands' freshwater goby Rhinogobius sp. Bonin Island (BI) form (Ogasawara-yoshinobori) and the Japan–Ryukyu Archipelago relatives, the mitochondrial DNA (mtDNA) phylogeny of Japanese Rhinogobius species was inferred from partial nucleotide sequences of the mitochondrial NADH dehydrogenase 5 subunit (ND5) gene (945 bp). The resultant tree showed that the Bonin Islands group separated first from the other Japanese lineage, and a test calculation indicated the divergence date to be approximately 3 million years BP. Although it is necessary to use a more reliable estimate to confirm the divergence date, Rhinogobius sp. BI has retained its mtDNA lineage in the islands for millions of years.     

Contrasting genetic variation and differentiation on Hainan Island and the Chinese mainland populations of Dacrycarpus imbricatus (Podocarpaceae)

Dacrycarpus imbricatus is a vulnerable conifer in China whose geographical distribution encompasses large island but small mainland populations, providing a framework for contrasting the patterns of population genetic composition. In this study, seven populations on Hainan Island and the Chinese mainland were sampled throughout its distribution range and assessed using ISSR. The results did not show significant differences neither in genetic variation nor in genetic differentiation between the island and the mainland populations (P > 0.05). Severe bottlenecks were identified at population, island/mainland as well as range-wide scales. A relatively high level of variation but a low degree of differentiation was revealed. Ecological and life traits were suggested to play main roles in the shaping of genetic variation pattern. Of them long generation times could have exerted a lagging effect on both the genetic variation and differentiation. Our findings may contribute to establish management practices.     

Agonistic behavior among colonies of the Formosan subterranean termite,Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae), from Florida and Hawaii: Lack of correlation with cuticular hydrocarbon composition

Cuticular hydrocarbon patterns of the Formosan subterranean termite, Coptotermes formosanus Shiraki, were similar among colonies from the same geographical location. Hydrocarbon patterns of Florida colonies were easily distinguished from those of Hawaii colonies by using canonical discriminant analysis. Groups of termites from the same colony did not fight one another when placed in an arena. Intercolonial aggression was not recorded among C. formosanuspopulations from Florida but three colonies from Hawaii fought with the other Hawaiian and three Florida colonies. Of the 12 colonies (six each from Florida and Hawaii) tested, 3 Florida colonies did not direct or receive aggression from any other colony. Cuticular hydrocarbon patterns were not correlated with agonistic behavior.     

Low genetic diversity and significant population structuring in the relict Amentotaxus argotaenia complex (Taxaceae) based on ISSR fingerprinting

Amentotaxus, a genus of the Taxaceae, represents an ancient lineage that has long existed in Eurasia. All Amentotaxus species experienced frequent population expansion and contraction over periodical glaciations in Tertiary and Quaternary. Among them, Amentotaxus argotaenia complex consists of three morphologically alike species, A. argotaenia, Amentotaxus yunnanensis, and Amentotaxus formosana. This complex is distributed in the subtropical region of mainland China and Taiwan where many Pleistocene refugia have been documented. In this study, genetic diversity and population structuring within and between species were investigated based on the inter-simple sequence repeats (ISSR) fingerprinting. Mean genetic diversity within populations was estimated in three ways: (1) the percentage of polymorphic loci out of all loci (P) (2) Neis unbiased expected heterozygosity (He), and (3) Shannons index of phenotypic diversity. For a total of 310 individuals of 15 populations sampled from the three species, low levels of ISSR genetic variation within populations were detected, with P=4.66–16.58%, He=0.0176–0.0645 and Hpop=0.0263–0.0939, agreeing with their seriously threatened status. AMOVA analyses revealed that the differences between species only accounted for 27.38% of the total variation, whereas differences among populations and within populations were 57.70 and 14.92%, respectively, indicating substantial isolation between the patch-like populations. A neighbor-joining tree identified a close affinity between A. yunnanensis and A. formosana. Genetic drift due to small population size, plus limited current gene flow, resulted in significant genetic structuring. Low levels of intrapopulational genetic variation and considerable interpopulational divergence were also attributable to demographic bottlenecks during and/or after the Pleistocene glaciations.     

Morphological and molecular variation in Mitchella undulata,with special reference to the systematic treatment of the dwarf form from Yakushima

Morphological and molecular variation in Mitchella undulata Siebold et Zucc. was examined to evaluate the genetic basis for recognizing the dwarf variety, M. undulata var. minor Masamune. Considerable variation in leaf size in M. undulata, but no obvious morphological discontinuities, were found between the normal and dwarf varieties. Instead, a weak cline running from the Pacific Ocean to the Sea of Japan was found. Anatomical observations of leaf blades revealed that the large variation in leaf size can be attributed to variation in the number of leaf cells and not to differences in cell size. A molecular analysis based on sequences of rDNA internal transcribed spacer regions indicated that there were two major genotypes in M. undulata with minor variation in haplotypes resulting from additional substitutions or putative recombination. The dwarf form from Yakushima was neither genetically uniform nor apparently differentiated from other populations. From these results, we conclude that the dwarf form of M. undulata should be treated at the rank of forma.     

Growth form distribution and genetic relationships in tree clusters of Pinus flexilis,a bird-dispersed pine

Seed dispersal by the Clark's nutcracker (Nucifraga columbiana Wilson) may markedly influence the growth form and genetic population structure of limber pine (Pinus flexilis James). The nutcracker buries clusters of seeds in subterranean caches; germination of clustered seeds often results in a growth form characterized by two or more genetically distinct trees with fused or contiguous trunks (tree clusters). The occurrence of a morphologically similar form, the multi-trunk tree (a single genet branched near the base), as well as the typical single-trunked tree, complicates the study of limber pine populations. We examined growth form distribution and genetic relationships in tree clusters in limber pine populations at four elevations (from 2585 m to 3460 m) in the Colorado Front Range. At three study areas, relative occurrence of limber pine growth forms, as well as that of associated pines, was examined by a point-centered quarter survey. From the four study areas, we collected foliage from each trunk from a total of 74 clumps (combined tree clusters and multi-trunk trees) in order to differentiate the two growth forms using starch gel protein electrophoresis. Tree clumps were significantly more common in limber pine than in ponderosa or lodgepole pine (P<0.010). Although single-trunk limber pine was the most common growth form, except at the highest elevation, both multi-trunk trees and tree clusters were present in each stand. Tree clusters were estimated to comprise about 20% of the tree sites in each limber pine stand; the estimated proportion of multi-trunk trees varied by site from 5% to 77%. Trees in clusters were related, on average, as half to full siblings (mean r=0.43), but were unrelated to trees in other clusters (mean r=0.01). Electrophoretic analysis suggests possible genetic differentiation in limber pine that may be the result of different selection pressures on the growth forms.     

NRAMP1 polymorphism in a hybrid population between Japanese and Taiwanese macaques in Wakayama, Japan

A macaque population produced by the hybridization of native Japanese macaques (Macaca fuscata) and introduced Taiwanese macaques (M. cyclopis) in Wakayama Prefecture was shown to possess three DNA haplotypes of the natural resistance-associated macrophage protein 1 (NRAMP1). Based on genotyping and comparison with M. fuscata populations, it was revealed that the introduced M. cyclopis population was polymorphic for the NRAMP1 locus. Extensive crossbreeding of the introduced species with the native species was confirmed using this genetic marker and the proportion of M. cyclopis genes was 57.4%. Results of statistical tests suggested non-random mating in the hybrid population.     

Species relationships and genetic variation in the diploid wheats (Triticum,Aegilops) as revealed by starch gel electrophoresis

Twenty enzyme loci were examined in the diploid species ofTriticum andAegilops for allelic variation by starch gel electrophoresis. SectionSitopsis, including the five species,Ae. speltoides, Ae. lingissima, Ae. sharonensis, Ae. bicornis andAe. searsii form a close subgroup withAe. speltoides slightly removed from the others.T. monococcum s. lat., was found to be closest to the species of theSitopsis group.Ae. comosa, Ae. umbellulata andAe. uniaristata form a second subgroup withAe. caudata most closely related to these species.Ae. squarrosa appears almost equally related to all of the species, showing no special affinity for any one species group. Nineteen out of twenty loci examined were polymorphic with a mean of 6.7 alleles per locus. Species could be, for most loci, characterized by the presence of predominant alleles. A conspicious genetic characteristic ofTriticum-Aegilops is the sharing of these predominant alleles between species. Within species variation is characterized by a diffuse distribution of secondary alleles.     

The combined role of topography and overstorey tree composition in promoting edaphic and floristic variation in a Mediterranean forest

This study aimed to address which factors, other than topography, contribute to the floristic variation of forested slopes. The natural forest studied is located in the Sudoeste Alentejano e Costa Vicentina Nature Park (southwestern Portugal). We sampled topographic, edaphic, floristic and community structure variables along three bottom–top hillside transects. Multivariate analyses of soil variables (by PCA), and of woody species composition and floristic–environmental relationships (by CCA and pCCA) were performed. Environmental–floristic trends strongly associated with the elevation gradient were identified. At lower altitudes, the lowest species richness, the highest soil fertility, and the tallest and most dense (least available light) canopy occurred. The spatial variation in woody species composition and abundance was closely associated with Zn availability in the soil and litter groundcover, but these varibles had significant spatial structure in the studied forest. The non-spatially structured species variance was better predicted by soil NO₃^– and NH₄⁺. The spatial variation of species data not shared with environmental variables was also calculated. We suggest that the influence of topographic gradient on the variation of edaphic variables and on the distribution and abundance of woody species was mediated by overstorey tree composition. Locally dominant tree species, in particular Quercus faginea and Quercus suber, may function as ecosystem engineers promoting environmental changes (i.e., Zn availability in soil, litter accumulation and light availability) that influence overall floristic variation.