Caste differentiation responses of two sympatric <Emphasis Type="Italic">Reticulitermes</Emphasis> termite species to juvenile hormone homologs and synthetic juvenoids in two laboratory assays

Summary We report on our investigations comparing three juvenile hormone (JH) homologs and two synthetic juvenoids to induce caste differentiation in laboratory colonies of Reticulitermes flavipes and R. tibialis. Two laboratory assays were evaluated as model systems for inducing caste differentiation: (1) shorter-term dish assays on groups of 20 individuals and (2) longer-term feeding assays on groups of 500 individuals. Each assay possessed attributes that can be considered advantageous under certain conditions. Specifically, dish assays were most suitable for presoldier and soldier induction, while jar assays provided for the induction of nymphs, presoldiers, soldiers, neotenic reproductives, and intercastes. Differences in response to the JH homologs and synthetic juvenoids were noted between species, suggesting differences in JH physiology may exist between R. flavipes and R. tibialis. Substantial morpholo-gical impacts were noted in association with some treatments, including (1) juvenoid-induced mandibular mal-formation in presoldiers, (2) JH II-induced abdominal elongation in R. flavipes soldiers and workers (associated with a presence of internal reproductive anatomy that is consistent with what would be expected to occur in pseudergates), and (3) JH II-induced soldier-nymph intercastes in R. tibialis that were able to further molt into soldier-alate intercastes. Findings are discussed in relation to the potential differences in JH-related physiology between R. flavipes and R. tibialis, and the use of model systems to induce rare castes and intercastes for molecular investigations of caste differentiation.     

Genetic diversity and differentiation in Portuguese cattle breeds using microsatellites

Genotype data from 30 microsatellites were used to assess genetic diversity and relationships among 10 native Portuguese cattle breeds, American Charolais and the Brazilian Caracú. Hardy–Weinberg equilibrium was observed for all loci/population combinations except for five loci in Brava de Lide and one locus in Alentejana that exhibited heterozygote deficiency. Estimates of average observed and expected heterozygosities, total number of alleles (TNA) per breed and mean number of alleles (MNA) per locus/population were obtained. A total of 390 alleles were detected. TNA among Iberian cattle ranged from 170 to 237 and MNA ranged from 5.67 to 8.07. The highest observed heterozygosities were found in the Caracú, Maronesa, Garvonesa and Arouquesa and the lowest in Brava de Lide and Mirandesa. Estimation of population subdivision using Wright's F_ST index showed that the average proportion of genetic variation explained by breed differences was 9%. Neighbour‐joining phylogenetic trees based on D_A distances showed that the genetic relationships of present‐day Portuguese native breeds are consistent with historical origins in the Brown Concave (Arouquesa, Mirandesa, Marinhoa) and Red Convex (Mertolenga, Alentejana, Garvonesa, Minhota) evolutionary groups. The Iberian Black Orthoide group, represented by Brava de Lide and Maronesa, and the Barrosã breed appeared to be more closely related to the Brown Concave group but may represent a separate lineage. The Caracú breed was not found to be closely associated with any of the native Portuguese breeds.     

Group size effect on worker juvenile hormone titers and soldier differentiation in Formosan subterranean termite

In a finite environment, population growth can lead to crowding, increased densities and stress. Termites live in highly organized societies and densities can increase astronomically as colonies grow. However, little is known about juvenile hormone (JH) changes in these insects as numbers increase, despite the fact that JH is a critical caste regulator in this insect. Using Formosan subterranean termites as a model, we evaluated minimum group size requirements for soldier differentiation and the effect of density (50, 100, 500, and 1000 individuals/experimental unit) on worker JH titers either with or without initial soldiers being present. The minimum group size investigation indicated that groups initiated with 5 workers were insufficient for soldier differentiation. Soldiers were produced in groups initiated with 10 or more workers. As density increased from 50 to 1000 individuals per experimental unit, worker JH levels were elevated. Presence of soldiers lessened the effect of density on rising worker JH titers, indicating that soldiers have the ability to down-regulate worker JH. The study provides direct evidence of a population density effect on JH in eusocial insects and sheds light on understanding of the regulatory mechanisms associated with termite soldier caste differentiation.     

Genetic diversity in the North American captive African elephant collection

One hundred and eight mitochondrial DNA (mtDNA) sequences were used in combination with multilocus genotypes generated from 19 nuclear microsatellite loci to assess the genetic diversity in the North American captive African elephant collection. The analysis of 4488 bp of mitochondrial nicotinamide adenine dinucleotide hydrogenenase subunit 4-cytochrome b (ND4-cyt b ) sequence revealed the existence of three distinct mtDNA lineages (Haplogroups I–III). The genetic distance between Haplogroups I/II and Haplogroup III was determined to be 0.046. The nucleotide diversity for the elephant mtDNA ND4-cyt b was <0.004. Analysis of multilocus genotypes indicated an average observed heterozygosity of 0.53 compared with the expected heterozygosity of 0.64. No subdivision in the data was detected including data partitioned by mtDNA haplogroup. Relatedness among the 108 individuals did not differ from that expected in random mating populations.     

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.     

Genetic differentiation and diversity of Acacia koa populations in the Hawaiian Islands

Acacia koa A. Gray (koa) is a leguminous tree endemic to the Hawaiian Islands and can be divided into morphologically distinguishable groups of A. koaia Hillebrand, A. koa and populations that are intermediate between these extremes. The objectives of this investigation were to distinguish among divergent groups of koa at molecular levels, and to determine genetic diversity within and among the groups. Phylogenetic analyses using the ITS/5.8S rDNA and trnK intron sequences did not separate the representative koa types into distinct clusters. An unweighted pair group method with arithmetic mean cluster analysis and principal coordinate analysis, based on allele profiles of 12 microsatellite loci for 215 individual koa samples, separated the population into three distinct clusters consistent with their morphology, A. koaia, A. koa and intermediate forms. There was an average of 8.8 alleles per polymorphic locus (AP) among all koa and koaia individuals. The intermediate populations had the highest genetic diversity (H′ = 1.599), AP (7.9) and total number of unique alleles (21), whereas A. koaia and A. koa showed similar levels of genetic diversity (H′ = 0.965 and 0.943, respectively). No correlation was observed between geographic distance and genetic distance as determined by a Mantel test (r = 0.027, P = 0.91). The data presented here support previous recommendations that morphological variation within koa should be recognized at the subspecific level rather than as distinct species.     

Genetic differentiation between the Old and New types of Serbian Tsigai sheep

Two Tsigai sheep populations exist in Serbia: the Old type, called Čokan, and the New type. It is assumed that the New type results from upgrading Tsigai sheep with exotic genetic material. We investigated genetic diversity and differentiation of these types by analysing 23 autosomal microsatellites. Tests for Hardy-Weinberg proportions, linkage equilibrium between genotypes across loci and the calculation of inbreeding coefficients were performed and the deficiency in the number of alleles within the Tsigai types was examined using a Wilcoxon sign-rank test. The New type displayed a higher level of genetic variability than the Čokan in terms of allele numbers, but the New Tsigai showed a pattern of heterozygosity deficiency. The positive f value for the Čokan suggests the occurrence of inbreeding in this type. The proportion of linkage disequilibrium was below that expected by chance. Exclusion of two loci in Hardy-Weinberg disequilibrium did not alter our conclusions based on the entire data set i.e. the two Tsigai types are clearly differentiated and the New Tsigai type has been influenced by crossbreeding. Therefore, the Čokan Tsigai should be considered as a distinct endangered breed in the FAO classification.     

Genetic consequences of natal dispersal in the colonial lesser kestrel

Dispersal is a life-history trait that plays a fundamental role in population dynamics, influencing evolution, species distribution, and the genetics and structure of populations. In spite of the fact that dispersal has been hypothesized to be an efficient behavioural mechanism to avoid inbreeding, the expected relationship between dispersal and mate relatedness still remains controversial. Here, we examine the genetic consequences of natal dispersal, namely the higher chance of obtaining genetically less similar mates as a result of moving from natal to breeding sites, in a lesser kestrel (Falco naumanni) population. Relatedness between individuals tended to decrease with distance between their breeding colonies, indicating that the study population follows an 'isolation-by-distance' pattern of spatial genetic structure. Such a fine-scale genetic structure generates a scenario in which individuals can potentially increase the chance of obtaining genetically less similar mates by dispersing over larger distances from their natal colony. Using dispersal information and genotypic data, we showed that mate relatedness decreased with natal dispersal distance, an effect that remained significant both while including and excluding philopatric individuals from the data set. These results, together with the well known detrimental consequences of reduced genetic diversity in the study population, suggest that dispersal may have evolved, at least in part, to avoid the negative fitness consequences of mating with genetically similar individuals.     

Bioassay design and length of time in the laboratory affect intercolonial interactions of the Formosan subterranean termite (Isoptera, Rhinotermitidae)

This study examined the effect of diet, experimental design, and length of time in the laboratory on intercolonial agonism among Formosan subterranean termite, Coptotermes formosanus Shiraki, colonies. In pairings of 12 C. formosanus Shiraki colonies collected in an urban forest, there was no significant reduction in survival of termites in 30 out of 59 colony pairs compared to colony controls, but there was <50% survival in 18 colony pairs and <10% survival in six colony pairs. There was no correlation between the level of aggressive behavior and the laboratory diet of the termites. Effect of bioassay design and length of time in the laboratory was evaluated in three colony pairs where tests were first conducted on the day of field collection, then colony pairs were retested every 7 days. Aggressive behavior decreased over time in both bioassays, but it tended to decrease more rapidly in the Petri dish tests. The rapid loss of agonism in groups of termites kept in the laboratory demonstrates that changes in environmental factors affect intercolonial agonism. This article presents the results of research only. Mention of a commercial or proprietary product does not constitute endorsement or recommendation by the USDA.     

Effects of antibiotics on hydrogen production and gut symbionts in the Formosan subterranean termite Coptotermes formosanus (Isoptera: Rhinotermitidae)

Abstract Symbiotic microorganisms that inhabit the gut of Coptotermes formosanus enable this termite to degrade lignocelluloses and further produce hydrogen as an important intermediate to be recycled in its hindgut or as a byproduct to be emitted to the atmosphere. Both symbiotic protists and prokaryotes in the guts of termites demonstrated some different roles with respect to hydrogen production. In this study, the effects of two antibiotics, ampicillin and tetracycline, on hydrogen emission and the gut symbionts of C. formosanus were investigated. Hydrogen emission from termite guts was significantly enhanced when termites fed on wood diets treated with either ampicillin or tetracycline. The greatest H₂ emission rates, 2 519 ± 74 and 2 080 ± 377 nmol/h/g body weight, were recorded with the treatments of ampicillin and tetracycline, respectively, which showed 6–7 times more H₂ production than that of controls. Antibiotic‐treated diets negatively affected the prokaryotic communities and reduced their abundances, particularly on those ectosymbionts inhabiting the gut walls or in the gut fluid of C. formosanus, such as spirochetes. However, no significant reductions in the counts of gut cellulolytic protists, Pseudotrichonympha grassii and Holomastigotoids hartmanni, were recorded; and with a further observation by confocal laser scanning microscopy, the endosymbionts inhabiting P. grassii generally survived the antibiotic treatments. These results suggest that some prokaryotes may serve as the main hydrogen consumers, while P. grassii, together with its endosymbionts, may function as the main contributors for hydrogen production in the hindgut of C. formosanus.     

Genetic diversity and bottleneck studies in the Marwari horse breed

Genetic diversity within the Marwari breed of horses was evaluated using 26 different microsatellite pairs with 48 DNA samples from unrelated horses. This molecular characterisation was undertaken to evaluate the problem of genetic bottlenecks also, if any, in this breed. The estimated mean (± s.e.) allelic diversity was 5.9 (± 2.24), with a total of 133 alleles. A high level of genetic variability within this breed was observed in terms of high values of mean (±s.e.) effective number of alleles (3.3 ± 1.27), observed heterozygosity (0.5306 ± 0.22), expected Levene’s heterozygosity (0.6612 ± 0.15), expected Nei’s heterozygosity (0.6535 ± 0.14), and polymorphism information content (0.6120 ± 0.03). Low values of Wright’s fixation index, F_IS (0.2433 ± 0.05) indicated low levels of inbreeding. This basic study indicated the existence of substantial genetic diversity in the Marwari horse population. No significant genotypic linkage disequilibrium was detected across the population, suggesting no evidence of linkage between loci. A normal ‘L’ shaped distribution of mode-shift test, non-significant heterozygote excess on the basis of different models, as revealed from Sign, Standardized differences and Wilcoxon sign rank tests as well as non-significantM ratio value suggested that there was no recent bottleneck in the existing Marwari breed population, which is important information for equine breeders. This study also revealed that the Marwari breed can be differentiated from some other exotic breeds of horses on the basis of three microsatellite primers.     

Genetic divergence and isolation by distance in the West Atlantic sea anemone Actinia bermudensis (McMurrich, 1889)

The sea anemone Actinia bermudensis [Proc. Acad. Nat. Sci. Philadelphia 41 (1889) 102] has a widespread distribution over the Western Atlantic, where it has been reported from Bermuda and Bahamas to southern Brazil. Nonetheless, reproductive features of this species, which broods asexually produced offspring, suggest that it has low dispersal capabilities. This raises a question about the specific status of the Brazilian population of A. bermudensis. The aim of this paper was to evaluate the taxonomic status of the Brazilian population, by genetically comparing it with the type locality (Bermuda) population. For this, we used allozyme electrophoresis to analyze samples from both populations. Thirteen enzyme systems (16 loci) yielded interpretable results for all populations. A high differentiation was encountered for the Western Atlantic A. bermudensis population (F_ST=0.434), partially due to the presence of a diagnostic locus (LAP) between Bermuda and Brazilian populations. This result could be taken as an indication that the Brazilian population should be elevated to a specific status. We do expect some genetic differentiation, however, between natural populations separated over wide geographic distances. Finally, since Mantel and regression analyses did not rule out the isolation by distance model, we have conservatively decided to maintain the specific status of A. bermudensis from Brazil.     

Strong association between polymorphisms in an intronic microsatellite and in the coding sequence of the BoLA-DKB3 gene: implications for micro-satellite stability and PCR-based DRB3 typing

A highly polymorphic microsatellite in the bovine DRB3 gene was characterized by polymerase chain reaction (PCR) analysis and DNA sequencing. A very strong association between expressed DRB3 polymorphism and microsatellite alleles was revealed by PCR analysis of genomic DNA from 116 animals representing three breeds of cattle. The results indicated a low frequency of microsatellite length mutations as the association was consistent over breeds. The DRB3 microsatellite may be utilized in a PCR-based typing method of bovine class II alleles. The microsatellite polymorphism did not distinguish all known DRB3 alleles, but it was shown that this method may be complemented by the use of allele-specific PCR based on the extensive polymorphism in the DRB3 exon 2. The DNA sequences of seven microsatellite alleles, associated with different class II hap-lotypes, were determined. The DRB3 microsatellite is composed of three repeat motifs, a stretch of at least 10 uninterrupted (TG)_n dinucleotides, a long but interrupted stretch of (GA)_n dinucleotides, and a few (CAGA)_n tetranucleotides. There were pronounced sequence differences beween alleles and the results indicated that the evolution of this microsatellite has involved length mutations of the dinucleotide repeats as well as point mutations causing interruptions in the dinucleotide repeats.     

Genetic diversity, population structure, effective population size and demographic history of the Finnish wolf population

The Finnish wolf population (Canis lupus) was sampled during three different periods (1996-1998, 1999-2001 and 2002-2004), and 118 individuals were genotyped with 10 microsatellite markers. Large genetic variation was found in the population despite a recent demographic bottleneck. No spatial population subdivision was found even though a significant negative relationship between genetic relatedness and geographic distance suggested isolation by distance. Very few individuals did not belong to the local wolf population as determined by assignment analyses, suggesting a low level of immigration in the population. We used the temporal approach and several statistical methods to estimate the variance effective size of the population. All methods gave similar estimates of effective population size, approximately 40 wolves. These estimates were slightly larger than the estimated census size of breeding individuals. A Bayesian model based on Markov chain Monte Carlo simulations indicated strong evidence for a long-term population decline. These results suggest that the contemporary wolf population size is roughly 8% of its historical size, and that the population decline dates back to late 19th century or early 20th century. Despite an increase of over 50% in the census size of the population during the whole study period, there was only weak evidence that the effective population size during the last period was higher than during the first. This may be caused by increased inbreeding, diminished dispersal within the population, and decreased immigration to the population during the last study period.     

Genetic and morphological characterisation of the Ankole Longhorn cattle in the African Great Lakes region

The study investigated the population structure, diversity and differentiation of almost all of the ecotypes representing the African Ankole Longhorn cattle breed on the basis of morphometric (shape and size), genotypic and spatial distance data. Twentyone morphometric measurements were used to describe the morphology of 439 individuals from 11 sub-populations located in five countries around the Great Lakes region of central and eastern Africa. Additionally, 472 individuals were genotyped using 15 DNA microsatellites. Femoral length, horn length, horn circumference, rump height, body length and fore-limb circumference showed the largest differences between regions. An overall F_ST index indicated that 2.7% of the total genetic variation was present among sub-populations. The least differentiation was observed between the two sub-populations of Mbarara south and Luwero in Uganda, while the highest level of differentiation was observed between the Mugamba in Burundi and Malagarasi in Tanzania. An estimated membership of four for the inferred clusters from a model-based Bayesian approach was obtained. Both analyses on distance-based and model-based methods consistently isolated the Mugamba sub-population in Burundi from the others.     

Isolation by distance in the crustose lichens Candelariella vitellina and Placynthium nigrum colonising gravestones in northeast Scotland

The majority of estimates of isolation by distance are produced byindirect molecular methods rather than direct observation of dispersal events orcolonisation rates. This is in part due to technical difficulties in recordingrare dispersal events in the field, and may be limiting the testing ofmetapopulation models. The fact that tombstones are dated on erection was usedto perform direct measurements of rates of colonisation for two contrasting speciesof crustose lichen, Candelariella vitellina andPlacynthium nigrum, which occur commonly on sandstone andgranite headstones, respectively. The effects of isolation by distancewere observed in the colonisation of sandstone by C. vitellina within the first 50 years of the erection of headstones in thesmallest of three burial grounds investigated in northeast Scotland. When therate of colonisation was estimated over different periods of time the effect ofisolation by distance was seen to decline as the stones aged. There was noapparent effect of isolation by distance on the rate of colonisation of graniteheadstones by P. nigrum at any of the three study sites atany period of colonisation. This study suggests that effects of isolation by distance are likely to behighly case specific, varying between species, between sites and over time. Thisimplies that great care should be taken when producing parameter estimates formetapopulation models.     

Genetic population structure and contemporary dispersal patterns of a recent European invader, the Chinese mitten crab, Eriocheir sinensis

Genetic studies of recently established populations are challenging because the assumption of equilibrium underlying many analyses is likely to be violated. Using microsatellites, we investigated determinants of genetic structure and migration among invasive European-Chinese mitten crab populations, applying a combination of traditional population genetic analyses and nonequilibrium Bayesian methods. Consistent with their recent history, invasive populations showed much lower levels of genetic diversity than a native Chinese population, indicative of recent bottlenecks. Population differentiation was generally low but significant and especially pronounced among recently established populations. Significant differentiation among cohorts from the same geographical location (River Thames) suggests the low effective population size and associated strong genetic drift that would be anticipated from a very recent colonization. An isolation-by-distance pattern appears to be driven by an underlying correlation between geographical distance and population age, suggesting that cumulative homogenizing gene flow reduces founder bottleneck-associated genetic differentiation between longer-established populations. This hypothesis was supported by a coalescent analysis, which supported a drift + gene flow model as more likely than a model excluding gene flow. Furthermore, admixture analysis identified several recent migrants between the UK and Continental European population clusters. Admixture proportions were significantly predicted by the volume of shipping between sites, indicating that human-mediated transport remains a significant factor for dispersal of mitten crabs after the initial establishment of populations. Our study highlights the value of nonequilibrium methods for the study of invasive species, and also the importance of evaluating nonequilibrium explanations for isolation by distance patterns.     

Allelic and genotypic diversity in long-term asexual populations of the pea aphid, Acyrthosiphon pisum in comparison with sexual populations

Many aphid species exhibit geographical variation in the mode of reproduction that ranges from cyclical parthenogenesis with a sexual phase to obligate parthenogenesis (asexual reproduction). Theoretical studies predict that organisms reproducing asexually should maintain higher allelic diversity per locus but lower genotypic diversity than organisms reproducing sexually. To corroborate this hypothesis, we evaluated genotypic and allelic diversities in the sexual and asexual populations of the pea aphid, Acyrthosiphon pisum (Harris). Microsatellite analysis revealed that populations in central Japan are asexual, whereas populations in northern Japan are obligatorily sexual. No mixed populations were detected in our study sites. Phylogenetic analysis using microsatellite data and mitochondrial cytochrome oxidase subunit I (COI) gene sequences revealed a long history of asexuality in central Japan and negated the possibility of the recent origin of the asexual populations from the sexual populations. Asexual populations exhibited much lower genotypic diversity but higher allelic richness per locus than did sexual populations. Asexual populations consisted of a few predominant clones that were considerably differentiated from one another. Sexual populations on alfalfa, an exotic plant in Japan, were most closely related to asexual populations associated with Vicia sativa L. The alfalfa-associated sexual populations harboured one COI haplotype that was included in the haplotype clade of the asexual populations. Available evidence suggests that the sexuality of the alfalfa-associated populations has recently been restored through the northward migration and colonization of alfalfa by V. sativa- associated lineages. Therefore, our results support the theoretical predictions and provide a new perspective on the origin of sexual populations.     

Admixture determines genetic diversity and population differentiation in the biological invasion of a lizard species

Molecular genetic analyses show that introduced populations undergoing biological invasions often bring together individuals from genetically disparate native-range source populations, which can elevate genotypic variation if these individuals interbreed. Differential admixture among multiple native-range sources explains mitochondrial haplotypic diversity within and differentiation among invasive populations of the lizard Anolis sagrei. Our examination of microsatellite variation supports the hypothesis that lizards from disparate native-range sources, identified using mtDNA haplotypes, form genetically admixed introduced populations. Furthermore, within-population genotypic diversity increases with the number of sources and among-population genotypic differentiation reflects disparity in their native-range sources. If adaptive genetic variation is similarly restructured, then the ability of invasive species to adapt to new conditions may be enhanced.