Context-dependent movement behavior of woodland salamanders (Plethodon) in two habitat types

Animal movement is critical to the maintenance of functional connectivity at the landscape scale and can play a key role in population persistence and metapopulation dynamics. The permeability of habitat to animal movement may vary as a result of either differential mortality, physical resistance, or simply the behavioral responses of organisms to perceived habitat quality. Understanding how and when animal movement behavior varies among habitat types is critical for identifying barriers to dispersal and predicting species distributions in relation to landscape features. We conducted an experimental translocation study and compared the movement success and behavioral strategies of plethodontid salamanders in both forest and open-canopy habitat. We found that individuals in closed-canopy forest oriented more strongly towards their home ranges and moved significantly farther on their release night. In spite of the clear differences in movement paths, the ultimate movement success of homing salamanders did not appear to vary with habitat type. Our study contributes to a growing body of literature suggesting the importance of recognizing the context dependence of animal movement behavior. Because the movement rates of displaced salamanders were significantly reduced in open-canopy, dispersal rates of plethodontid salamanders in open-canopy habitat are likely lower than in control forest. Further mechanistic studies focusing on habitat-specific movement behavior and survival costs will be valuable for effectively identifying and mitigating barriers to animal movement.     

Identification and mapping of random amplified polymorphic DNA (RAPD) markers linked to resistance against beet necrotic yellow vein virus (BNYVV) in Beta accessions

Molecular markers linked to resistance genes are useful to facilitate the introgression of one or more of these genes in breeding materials. Following the approach of bulked segregant analysis, RAPD markers linked to resistance genes against beet necrotic yellow vein virus were identified in the four Beta accessions Holly-1-4, R104, R128 and WB42. Two primers were found which generate RAPD markers tightly linked to resistance in segregating families of Holly-1-4, R104 and R128, indicating that the resistance genes in these accessions might be situated at the same locus. Other, specific, primers were identified which generate RAPD markers linked to resistance in each of these accessions. Short-range maps were established around the resistance locus in these accessions. For WB42, RAPD markers were only identified at a relatively large distance from the resistance gene. Conversion of three RAPD primers of Holly-1-4, R104 and R128 into STS primers resulted in STS markers which can be readily used for marker-assisted selection in breeding programmes. Received: 8 January 1996 / Accepted: 14 June 1996     

Pheromonal emission during the mating behavior ofEurycotis floridana (Walker) (Dictyoptera: Blattidae)

The sexual behavior of males and females ofEurycotis floridana was investigated and the various associated behavioral sequences are described. Olfactometer data proved that the male produces a volatile sex pheromone attractive at a distance to conspecific females. The male initiates courtship behavior by exposing the glandular areas on the anterior parts of abdominal tergites 2, 7, and 8. This male calling behavior was observed throughout the day. The males can mate when 8 days old, whereas virgin females are sexually receptive 18 days after becoming adults. Once attracted near the male, the female opens her genital atrium and climbs on the back of the male, where she feeds on the glandular secretions that oozed around a little tuft of setae on the first tergite. These setae are mechanoreceptors and they are stimulated when licked by the females, which informs the male that she is in a proper position for copulation.     

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.     

Mapping of two genes for resistance to clubroot (Plasmodiophora brassicae) in a population of doubled haploid lines of Brassica oleracea by means of RFLP and AFLP markers

A genetic map covering 615 cM in 12 linkage groups was assembled based on 92 RFLP and AFLP markers segregating in a population of 107 doubled haploid lines (DH lines) of Brassica oleracea. The DH-line population was obtained through microspore culture from the of two homozygous parents: DH-line Bi derived from the cabbage landrace Bindsachsener, and DH-line Gr from broccoli cv ‘Greenia’. Sixty-five percent of the loci, and in some cases complete linkage groups, displayed distorted segregation ratios, a frequency much higher than that observed in populations of the same species. DH-line Bi was resistant to clubroot, which is caused by a Dutch field isolate of Plasmodiophora brassicae. Resistance in the DH-line population was determined in two ways: by assigning symptom grades to each plant, and by measuring the fresh weights of the healthy and affected parts of the root system of each plant. Using a multiple QTL mapping approach to analyze the fresh weight data, we found two loci for clubroot resistance; these were designated pb-3 and pb-4. The additive effects of these loci were responsible for 68% of the difference between the parents and for 60% of the genetic variance among DH-line means. Also, indications for the presence of two additional, minor QTLs were found. Analysis of symptom grades revealed the two QTLs pb-3 and pb-4, as well as one of the two minor QTLs indicated by analysis of the fresh weight data. Received: 29 April 1996 / Accepted: 10 May 1996     

Sperm aggregations in the spermatheca of the red back salamander (Plethodon cinereus)

The spermatheca of Plethodon cinereus is a compound tubular gland that stores sperm from mating in early spring (March–April) to oviposition in summer (June–July). The seasonal variation of sperm storage in this species has previously been studied by light and transmission electron microscopy. In this paper, sperm aggregations, interaction of sperm with the spermathecal epithelium, and spermathecal secretions are studied using scanning electron microscopy. Within spermathecal tubules, relatively small groups of sperm are aligned along their entire lengths in parallel arrays. This pattern is similar to other plethdontids with complex spermathecae. Lumina of spermathecal tubules are filled with secretory material in April prior to the arrival of sperm, and after sperm appear, a coating of secretory material persists on the apices of the spermathecal epithelium. Sperm peripheral to the central luminal mass can become embedded in the secretory matrix or pushed deeper into the spermathecal epithelium. The spermathecal secretions may serve to attract and prolong the viability of sperm, but sperm that become enmeshed in the secretions or epithelium are phagocytized. Sperm and spermathecal secretions are largely absent after ovulation and in summer months, and new secretory vacuoles are formed in fall, although mating does not occur until spring.     

Polymorphism, distribution, and segregation of AFLP markers in a doubled haploid rice population

We exploited the newly developed amplified fragment length polymorphism (AFLP) technique to study the polymorphism, distribution and inheritance of AFLP markers with a doubled haploid rice population derived from ‘IR64’/‘Azucena’. Using only 20 pairs of primer combinations, we detected 945 AFLP bands of which 208 were polymorphic. All 208 AFLP markers were mapped and distributed over all 12 chromosomes. When these were compared with RFLP markers already mapped in the population, we found the AFLP markers to be highly polymorphic in rice and to follow Mendelian segregation. As linkage map of rice can be generated rapidly with AFLP markers they will be very useful for marker-assisted backcrossing. Received: 11 April 1996 / Accepted: 14 June 1996     

Mapping of the Rf-3 nuclear fertility-restoring gene for WA cytoplasmic male sterility in rice using RAPD and RFLP markers

The cytoplasmic male sterility (CMS) of wild-abortive (WA) cytoplasm has been widely used for breeding hybrid rice. Two restorer genes for the CMS have been found by traditional genetic analysis. To tag the restorer genes we used a set of near-isogenic lines (NILs) of Zhenshan 97 carrying different genotypes for fertility restoration from IR24, to perform RAPD analysis. From the survey of 720 random primers, six RAPD markers were identified to be associated with Rf-3. Three of these OPK05-800, OPU10-1100 and OPW01-350, were mapped on chromosome 1. Two populations from the crosses between Zhenshan 97 A and a near-isogenic restorer line ZSR21 and between Zhenshan 97 A and IR24 were used for mapping Rf-3. The three RAPD markers and three RFLP markers, RG532, RG140 and RG458, were found to be closely linked to Rf-3 in the two populations. The same location of Rf-3 was also found in a population from the cross of IR58025 A//IR36/IR58025 B. At the RG532 locus, different alleles were found between two CMS lines, Zhenshan 97 A and IR58025 A, and between two restorer lines, IR24 and IR36. The use of these molecular markers closely linked to Rf-3 in facilitating the development of hybrid rice is discussed. Received: 3 January 1996 / Accepted: 17 May 1996     

Phenological stages of natural species and their use as climate indicators

 The objectives of this paper are to: (1) present 10 years of phenological data for nine natural species growing in a Mediterranean-type climate, (2) present threshold temperatures that were derived for the computation of cumulative degree-days (CDD), and (3) evaluate the sensitivity of the nine natural species to weather variability. The study was conducted at the Phenological Research Garden of Oristano, Sardinia, Italy, during the period 1986–96. The observations were made on five typical Mediterranean species and four species that are typical of higher latitudes. The mean annual pattern of phenological events and the CDD from 1 January are given for each development stage. Temperature thresholds were evaluated by comparing the standard deviation about the mean number of days in the development period for each species. A good relationship between timing of phenophase occurrence and temperature was observed for the Mediterranean species, which were little affected by variations in rainfall. Phenological development of the non-native species was affected by springtime rainfall. Accepted: 28 October 1998     

Hybrid performance and genetic distance as revealed by the (GATA)4 microsatellite and RAPD markers in pearl millet

 Genetic diversity in five cytoplasmic male-sterile and seven restorer lines of pearl millet was determined by DNA fingerprinting using a (GATA)₄ microsatellite and randomly amplified polymorphic DNAs (RAPDs). A total of 160 polymorphic loci were generated and, based on the polymorphism data, similarity index values ranged from 0.81 to 0.50. Cluster analysis was performed and relationships among these lines revealed that they were not in agreement with the available pedigree data. The per se performance of parents and hybrids was analyzed for days-to-50% flowering, plant height, productive tillers, ear length, ear width, 1000-grain weight and grain yield per plot. Path co-efficient analysis revealed that productive tillers, ear width and days-to-50% flowering had a relatively large positive effect. The correlation values were mostly not significant with respect to genetic distance, except for days-to-50% flowering, ear length and ear width. Our results have indicated that genetic-distance measures based on the (GATA)₄ microsatellite and RAPDs may be useful for the grouping of parents, but not for predicting heterotic combinations, in pearl millet. Received: 3 January 1998 / Accepted: 25 February 1998     

Characterization of the genetic resources of redcurrant (Ribes rubrum: subg. Ribesia) using anchored microsatellite markers

 Redcurrant, Ribes rubrum L., germplasm was screened for molecular polymorphism using anchored microsatellite primers in polymerase chain reactions (PCRs). Eighty markers were detected using only three primers and 16 redcurrant genotypes were fingerprinted using these markers. The genetic relatedness of these genotypes, as determined by the anchored microsatellite markers, and the implications for redcurrant breeding programmes are examined. Received: 18 October 1997 / Accepted: 1 December 1997     

Selective fruit filling in relation to pollen load size in Alstroemeria aurea (Alstroemeriaceae)

 We conducted an experiment in a natural population of Alstroemeria aurea, a clonal perennial, to determine (1) if reproduction was resource limited, and (2) if fruits would be selectively filled based on differences in pollination intensity when pollen loads were adequate for full seed set. Under these conditions, differences in pollination intensity are unlikely to affect seed number, but could affect seed quality, providing an interesting test of the gametophytic competition hypothesis. To test for resource limitation, percent fruit maturation, number of seeds per fruit and average seed weight were compared to paired controls for ramets in which all but one fruit was removed. To test the effect of pollination intensity on selective resource allocation, three types of pollination treatments were performed: (1) all flowers of the single inflorescence received a low pollen load, (2) all flowers received a high pollen load, (3) alternate flowers of the inflorescence received either a high or a low pollen load. We determined the percentage of fruit that reached maturity, counted the number of seeds and ovules and calculated the average seed weight for all capsules in each treatment. Resources appeared to limit reproduction in this population since seed number and weight were significantly higher than in controls when competing capsules were removed. At the whole ramet level, a four fold difference in pollen loads had no significant effect on any of the parameters measured. However, when pollination intensity varied within an inflorescence, the number of seeds per fruit increased by about 10% in flowers that received the higher pollen load. We observed the same trend in each of 2 years, but the increase was significant in only 1 year. The differences, although not great, were only slightly smaller than when all competing fruits were removed, and were consistent with selective resource allocation based on pollination intensity independent of seed set. Received: 28 September 1997 / Accepted: 30 April 1998     

Identification of DNA amplification fingerprinting (DAF) markers close to the symbiosis-ineffective sym31 mutation of pea (Pisum sativum L.)

 We demonstrate efficient genome mapping through a combination of bulked segregant analysis (BSA) with DNA amplification fingerprinting (DAF). Two sets of 64 octamer DAF primers, along with two PCR programs of low- and high-annealing temperatures (30°C and 55°C, respectively), appeared to be enough to locate molecular markers within 2–5 cM of a gene of interest. This approach allowed the rapid identification of four BSA markers linked to the pea (Pisum sativum L.) Sym31 gene, which is responsible for bacteroid and symbiosome differentiation. Three of these markers are shown to be tightly linked to the sym31 mutation. Two markers flanking the Sym31 gene, A21-310 and B1-277, cover a 4–5 cM interval of pea linkage group 3. Both markers were converted to sequence-characterized amplified regions (SCARs). The flanking markers may be potential tools for marker-assisted selection or for positional cloning of the Sym31 gene. Received: 2 July 1998 / Accepted: 8 October 1998     

Development and characterization of microsatellite markers in the sexual-apomictic complex Taraxacum officinale (dandelion)

 Microsatellite markers were developed in Taraxacum officinale to study gene flow between sexual and apomictic plants and to identify clones. Twenty five thousand genomic DNA clones were hybridized with a (CT)₁₂D probe. The density of (GA/CT) _n repeats was estimated at one every 61 kb in the T. officinale genome, which translates to 13 500 repeats per haploid genome. Ninety two percent of 110 positive clones sequenced contained at least one (GA/CT) _n≥5 repeat. Sixteen (CA/GT) _n≥5 and 11 (AT) _n≥5 arrays were also found in these sequences, suggesting some clustering of dinucleotide repeats. Among 50 PCR primer pairs tested, 32 produced bands and 28 of them were polymorphic. Of these polymorphic markers, 15 were putatively single-locus and the other 13 produced only polymorphic fingerprints. Six loci were further characterized for polymorphism and showed between 6 and 32 alleles per locus. Among eight primer pairs used to analyze the progeny of a sexual cross, seven were co-dominant single-locus Mendelian markers, but one (MSTA10) gave a dominant pattern in accordance with the hypothesis of a null allele segregating in a Mendelian fashion. Three pairs of loci among 28 showed significant linkages of 10, 21, and 39 cM. Observed and expected heterozygosities in two sexual populations indicate that null alleles may be present at two loci, including MSTA10. Received: 4 November 1997 / Accepted: 12 February 1998     

Applicability of inter-simple sequence repeat polymorphisms in wheat for use as DNA markers in comparison to RFLP and RAPD markers

 Inter-simple sequence repeat polymorphic DNA (ISSR) was evaluated for its applicability as a genetic marker system in wheat. PCR was carried out with primers that annealed to simple sequence repeats. The resultant products were subjected to agarose-gel electrophoresis, and the banding patterns were compared among six wheat accessions containing diploid, tetraploid, and hexaploid members. Out of 100 examined, 33 primers produced distinguishable as well as polymorphic bands in each of the six accessions. Although most of the primers that gave distinct bands (30 primers out of 33) contained dinucleotide repeats, each of the primers with tri-, tetra-, and penta-nucleotide motifs also yielded discrete bands. Primers based on (AC)_n repeats gave the most polymorphic bands. In total, 224 polymorphic bands were found in the comparison between Einkorn wheats whereas, on the average, 120 polymorphic bands were detected between common wheats. ISSR primers produced several times more information than RAPD markers. The extent of band polymorphism was similar to that of RFLP markers, and greater than that of RAPDs. The genetic relationships of wheat accessions estimated by the polymorphism of ISSR markers were identical with those inferred by RFLP and RAPD markers, indicating the reliability of ISSR markers for estimation of genotypes. These polymorphic bands are potential candidates as novel markers for use in linkage-map construction in wheat. The characteristic features of ISSR markers, i.e. polymorphism, generation of information and ease of handling, suggest their applicability to the analysis of genotypes as well as to the construction of PCR-based genome maps of wheats. Received: 15 September 1996 / Accepted: 25 October 1996     

A high-density molecular map for ryegrass (Lolium perenne) using AFLP markers

AFLP markers have been successfully employed for the development of a high-density linkage map of ryegrass (Lolium perenne L.) using a progeny set of 95 plants from a testcross involving a doubled-haploid tester. This genetic map covered 930 cM in seven linkage groups and was based on 463 amplified fragment length polymorphism (AFLP) markers using 17 primer pairs, three isozymes and five EST markers. The average density of markers was approximately 1 per 2.0 cM. However, strong clustering of AFLP markers was observed at putative centromeric regions. Around these regions, 272 markers covered about 137 cM whereas the remaining 199 markers covered approximately 793 cM. Most genetic distances between consecutive pairs of markers were smaller than 20 cM except for five gaps on groups A, C, D, F and G. A skeletal map with a uniform distribution of markers can be extracted from this high-density map, and can be applied to detect and map QTLs. We report here the application of AFLP markers to genome mapping, in Lolium as a prelude to quantitative trait locus (QTL) identification for diverse agronomic traits in ryegrass and for marker-assisted plant breeding. Received: 4 November 1998 / Accepted:15 March 1999     

Inheritance patterns of new genetic markers and occurrence of spontaneous mosaicism in the monogenic blowfly Chrysomya rufifacies (Diptera: Calliphoridae)

 Four new genetic markers for Chrysomya rufifacies, a fly with maternal sex determination, were characterized. The markers include one body colour mutant, black body (bl), and three eye colour mutants, brown eye (br), apricot eye (ap), and red eye (w ^r ). Two of the latter, br and w ^r , turn out to be sex linked, the others behave as autosomal genes belonging to different linkage groups. w ^r is a hypomorphic and w an apomorphic mutation of the white gene, w/w is epistatic to br/br and to ap/ap. A preliminary genetic linkage map with the sex realizer F′/f  and the loci br and w residing in homomorphic sex chromosomes is established. Evidence is presented that crossing over is absent in the male sex. The possible causes of the spontaneous appearance of mosaics for eye colour observed among individuals heterozygous for recessive genes are discussed. Received: 18 March 1996/Accepted: 9 August 1996     

Sequence-tagged-sites (STSs) of cDNA clones in Cryptomeria japonica and their evaluation as molecular markers in conifers

 We have generated 66 sequence-tagged-site (STS) markers from cDNA clones of Cryptomeria japonica, and 60% of them have already been mapped into C. japonica linkage groups. All of the STS markers showed a single fragment following polymerase chain reaction (PCR) amplification. We investigated by polymorphism of these STS markers in a mapped F₂ population and 15 plus trees by means of a restriction endonuclease analysis. Polymorphism levels were 10.6% and 22.7% in the F₂ population and the 15 plus trees, respectively. PCR amplification levels of the 66 STS markers in 14 conifer species varied depending on their genetic relationship with C. japonica. Taxodium, which is closely related to C. japonica, had the most amplifications (31.82%), followed by Sequoiadendron giganteum, which is of the same family. The average proportion of PCR amplifications in each family gradually declined in the following order: from Taxodiaceae to Cuppresaceae, Sciadopityaceae, Pinaceae, and Taxaceae. These results are in general agreement with a molecular phylogenetic relationship based on chloroplast DNA. The 66 STS markers will be useful as on anchor point for genome mapping and population genetics, and some of them will also be useful when studying other conifers. Received: 8 September 1996 / Accepted: 8 November 1996     

Genomic relationships within Boronia (Rutaceae) as revealed by karyotype analysis and RAPD molecular markers

 The genus Boronia Sm. section Boronia series Boronia contains species with n=7 (B. megastigma), n=7 or 8 (B. heterophylla), n=8 (B. molloyae) and n=9 (B. purdieana), representing ideal species with which to examine comparative chromosome morphology. Between species there were few chromosomes with similar morphology, indicating numerous genome re-organisations. Karyotypes between and within species of Boronia could be distinguished and inheritance of some chromosomes was observed. Species and hybrids with 2n = 14 or 15 had at least one large chromosome. Chromosome morphology indicated a closer relationship between B. heterophylla and B. molloyae and between B. purdieana and B. megastigma than between these two groups. Whole genomic DNA was extracted from 9 genotypes of Boronia. RAPD bands were analysed and pairwise distance matrices between genotypes were computed. Dendrograms were generated and analysed using unweighted pair-group method with arithmetic average cluster analysis. Dendograms supported cytological results, indicating B. heterophylla and B. molloyae are closely related and clearly distinct from B. megastigma and B. purdieana. The evolution of boronias is discussed. Received February 16, 2001; accepted March 21, 2002 Published online: October 14, 2002 Address of the authors: G. Yan, F. Shan, J. A. Plummer (e-mail: jplummer@cyllene.uwa.edu.au), Plant Sciences, Faculty of Natural and Agricultural Science, The University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia.