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Extensive Variation (extensive + variation)
Selected AbstractsField Cricket Species Differences in the Temporal Patterns of Long-Distance Mate Attraction SignalsETHOLOGY, Issue 9 2006Susan M. Bertram We quantify variation in the temporal components of long-distance mate attraction signals produced by a North American field cricket, Gryllus rubens Scudder. Total signaling time, trilling bout duration, and hourly bout number exhibit high repeatability within individuals. Extensive variation exists across individuals: some males never signal while others signal for several hours each night; of the signalers, average trilling bout duration ranges from <1 min to well over an hour; some males produce only one trilling bout in an evening while others produce three bouts every 2 h. Body size, weight, wing morphology, and condition do not appear to explain the variation. We compare the temporal signaling components of G. rubens with its sister species, G. texensis. Although G. rubens produce slightly more trills per hour with slightly shorter trilling bout durations, the temporal components of these long-distance mate attraction signals are surprisingly similar across species. [source] Combining information from range use and habitat selection: sex-specific spatial responses to habitat fragmentation in tawny owls Strix alucoECOGRAPHY, Issue 2 2006Peter Sunde How individuals respond to habitat heterogeneity is usually measured as variation in range size and by ranking the relative importance of habitat types (habitat selection). The combined effect of how individuals incorporate different habitat types in their home ranges and allocate their time budget between them is rarely derived. Additionally, when home range size varies between individuals, habitat selection analyses might be flawed if foraging decisions are based on variation in absolute rather than proportional availability. We investigated the suitability of standard analytical approaches by measuring the spatial responses of tawny owls to habitat fragmentation. These owls inhabited woodland of various sizes, representing a fragmentation gradient from open farmland with small, isolated woodland patches, to continuous woodland within their home ranges. In 17 territories within open farmland, the available area covered by woodland increased with the square root of the area of open land embraced in the home range. The owls did not display functional response in habitat selection, but females selected woodland more strongly than males. Females utilised woodland 10 times more intensively in farmland than in continuous woods, whereas males utilised farmland woods 3.2 times more intensively. Moreover, females in farmland exploited woodland 3.2 times as intensively as males, apparently because of higher travel costs in open areas. Since the extensive variation in intensity of use as a function of total availability was not indicated from the analysis of habitat selection, we suggest that information about intensity of use be more widely used as a supplementary measure of habitat use patterns than appears to be the practice at present. [source] Spatio-temporal dynamics and local hotspots of initial recruitment in vertebrate-dispersed treesJOURNAL OF ECOLOGY, Issue 4 2008Arndt Hampe Summary 1Initial recruitment, or the arrival and establishment of propagules, is the most variable period in the life cycle of long-lived plants, and the extent to which studies of initial recruitment can be used to predict patterns of regeneration remains unresolved. 2We investigated the spatio-temporal dynamics of initial recruitment across five populations of three fleshy-fruited tree species from contrasting environments. Among-year variation in total seedfall, dispersed seedfall and seedling distributions was examined using analytical approaches that are new to the field and that explicitly incorporate space and allow comparisons among studies. 3Observed patterns ranged from remarkable across-year consistency in seedfall distributions and strong spatial coupling between seed and seedling stages to extensive variation and almost complete independence of stages. Spatial distributions of frugivore-mediated seedfall were markedly more consistent than those of the total seedfall in two of the five populations. Seedling distributions were generally more variable among years than seedfall distributions. 4All populations showed a positive relationship between the long-term mean density of recruitment at a given microsite and its year-to-year consistency. This relationship remained valid when considering only microsites away from fruiting tree canopies (i.e. those receiving actually dispersed seeds), and was virtually independent of their distance to the nearest fruiting tree. 5Synthesis. Our results point to the existence of some general rules behind the idiosyncratic recruitment dynamics of perennial plant populations, which should help with projecting spatial patterns of plant establishment in long-lived species. In particular, those microsites that combine a great intensity with a high year-to-year consistency of recruitment should represent potential regeneration ,hotspots' whose identification and characterization can be of great use for the management and conservation of naturally regenerating tree populations. [source] Tracing the geographical origin of Megastigmus transvaalensis (Hymenoptera: Torymidae): an African wasp feeding on a South American plant in North AmericaMOLECULAR ECOLOGY, Issue 2 2003Sonja J. Scheffer Abstract Determining the geographical origin of an introduced organism can be critical to understanding or managing a non-native species, but is often difficult when the organism is small or inconspicuous. We used a phylogeographical approach to identify the region of endemism and determine the geographical origin of world populations of the seed-feeding wasp Megastigmus transvaalensis (Hussey). This wasp feeds on African Rhus species and South American Schinus species in various locations around the world. Because it is present both in Africa and in South America, it is unclear whether the wasp was originally an African Rhus -feeder that has begun feeding on Schinus or a South American Schinus -feeder that has started feeding on Rhus. Phylogenetic analysis of 800 bp of mitochondrial cytochrome oxidase I sequence data found extensive variation and phylogeographical structure within African M. transvaalensis. Specimens from other locations around the world were all identical in COI sequence and were phylogenetically nested within the African samples. We conclude that M. transvaalensis was originally an African Rhus -feeder that readily attacks Schinus. We evaluate potential pathways of introduction of this wasp to the New World, and we discuss implications of our results for biocontrol efforts against invasive Schinus populations. [source] Introduction of aromatic fragrance into cultivated tomato from the peruvianum complex'PLANT BREEDING, Issue 2 2001H. M. Kamal Abstract This study was performed to introduce the distinct aromatic fragrance of Lycopersicon peruvianum LA 1554 into the cultivated tomato, Lycopersicon esculentum. The strong breeding barriers existing between these two distantly related species were circumvented by the ovule selection and culture method. A large BC1F1 population was developed and among 127 plants, 36 were self-compatible and yielded fruits. Fruits of some of these selected plants were found to be enriched with a sweet aromatic flavour. Sensory evaluation of the fruit aroma of these selected plants was performed by a panel of 12 members against one of the best consumer-rated Japanese commercial tomato cultivars, ,Momotaro'. Although extensive variation was observed in fruit-aroma in the BC1F1 population, panel opinion on ,flavour-desirability' significantly favoured the BC1F1 fruits of some selected plants over the cv. ,Momotaro'. Therefore, it can be concluded that the aromatic fragrance of a ,L. peruvianum' accession has successfully been introduced into the cultivated tomato gene pool. [source] Hominoid seminal protein evolution and ancestral mating behaviorAMERICAN JOURNAL OF PRIMATOLOGY, Issue 10 2008Sarah J. Carnahan Abstract Hominoid mating systems show extensive variation among species. The degree of sexual dimorphism in body size and canine size varies among primates in accordance with their mating system, as does the testes size and the consistency of ejaculated semen, in response to differing levels of sperm competition. To investigate patterns of evolution at hominoid seminal proteins and to make inferences regarding the mating systems of extinct taxa, we sequenced the entire coding region of the prostate-specific transglutaminase (TGM4) gene in human, chimpanzee, bonobo, western lowland gorilla, eastern lowland gorilla, orangutan, and siamang, including multiple humans, chimps, and gorillas. Partial DNA sequence of the coding regions was also obtained for one eastern lowland gorilla at the semenogelin genes (SEMG1 and SEMG2), which code for the predominant proteins in semen. Patterns of nucleotide variation and inferred protein sequence change were evaluated within and between species. Combining the present data with previous studies demonstrates a high rate of amino acid substitutions, and low intraspecific variation, at seminal proteins in Pan, presumably driven by strong sperm competition. Both gorilla species apparently possess nonfunctional TGM4, SEMG1, and SEMG2 genes, suggesting that gorillas have had low sperm competition, and therefore their current polygynous mating system, for a long time before their divergence. Similarly, orangutans show longstanding stasis at TGM4, which may be interpreted as evidence for an unchanging mating system for most of their evolution after their divergence from African apes. In contrast to the great apes, the data from humans could be interpreted as evidence of fluctuations between different mating systems or alternatively as a relaxed functional constraint in these proteins. It is our hope that this study is a first step toward developing a model to predict ancestral mating systems from extant molecular data to complement interpretations from the fossil record. Am. J. Primatol. 70:939,948, 2008. © 2008 Wiley-Liss, Inc. [source] Variation in chicken populations may affect the enzymatic activity of lysozymeANIMAL GENETICS, Issue 2 2010T. Downing Summary The chicken lysozyme gene encodes a hydrolase that has a key role in defence, especially in ovo. This gene was resequenced in global chicken populations [red, grey, Ceylon and green jungle fowl (JF)] and related bird species. Networks, summary statistics and tests of neutrality indicate that although there is extensive variation at the gene, little is present at coding sites, with the exception of one non-synonymous site. This segregating site and a further fixed non-synonymous change between red JF and domestic chicken populations are spatially close to the catalytic sites of the enzyme and so might affect its activity. [source] Indigenous domestic breeds as reservoirs of genetic diversity: the Argentinean Creole cattleANIMAL GENETICS, Issue 5 2001G. Giovambattista Contrary to highly selected commercial breeds, indigenous domestic breeds are composed of semi-wild or feral populations subjected to reduced levels of artificial selection. As a consequence, many of these breeds have become locally adapted to a wide range of environments, showing high levels of phenotypic variability and increased fitness under natural conditions. Genetic analyses of three loci associated with milk production (,S1 -casein, , -casein and prolactin) and the locus BoLA-DRB3 of the major histocompatibility complex indicated that the Argentinean Creole cattle (ACC), an indigenous breed from South America, maintains high levels of genetic diversity and population structure. In contrast to the commercial Holstein breed, the ACC showed considerable variation in heterozygosity (He) and allelic diversity (A) across populations. As expected, bi-allelic markers showed extensive variation in He whereas the highly polymorphic BoLA-DRB3 showed substantial variation in A, with individual populations having 39,74% of the total number of alleles characterized for the breed. An analysis of molecular variance (AMOVA) of nine populations throughout the distribution range of the ACC revealed that 91.9,94.7% of the total observed variance was explained by differences within populations whereas 5.3,8.1% was the result of differences among populations. In addition, the ACC breed consistently showed higher levels of genetic differentiation among populations than Holstein. Results from this study emphasize the importance of population genetic structure within domestic breeds as an essential component of genetic diversity and suggest that indigenous breeds may be considered important reservoirs of genetic diversity for commercial domestic species. [source] | ||||||||||