bluuebunny/crossref_metadata_2025 huggingface dataset:
Adaptive divergence vs. environmental plasticity: tracing local genetic adaptation of metamorphosis traits in salamanders
Authors: Weitere Markus , Tautz Diethard , Neumann Dietrich , Steinfartz Sebastian
Published: May 2004

In order to assess the significance of local adaptation relative to environmental plasticity on the evolution of life history traits, we analysed the possible genetic basis of differences between pond‐ and stream‐breeding fire salamanders (Salamandra salamandra) in Germany. These salamanders typically deposit their larvae in small streams, where they grow until they are sufficiently large to metamorphose. However, some populations in Western Germany use ponds as larval habitat. Because habitat quality of streams differs from that of ponds one expects life history differences in the pond animals, which may result either from a plastic response or through genetic differentiation (i.e. local adaptation). Using a phylogeographical analysis of mitochondrial D‐loop sequences, we show that both stream and pond populations in Western Germany are derived from a single lineage that recolonized following the last glaciation. This finding suggests that pond breeding originated very recently. Our studies of habitat quality and metamorphic behaviour of larvae in natural ponds and streams disclosed that pond larvae experience a significantly reduced food supply and greater risk of drying than do stream larvae. Pond larvae metamorphose earlier at the cost of reduced mass. Common‐environment experiments with pond and stream larvae show that metamorphic behaviour of pond larvae under limited‐food conditions is determined genetically and is not simply a plastic response to the differing habitat conditions. These results show that phenotypic plasticity is less important than local adaptation in explaining differences in ecological diversification within this species and suggests the possibility of rapid evolution of genetic adaptations when new habitats are exploited.
Genetic detection of sex‐specific dispersal in historical and contemporary populations of anadromous brown trout Salmo trutta
Authors: Bekkevold Dorte , Hansen Michael M. , Mensberg Karen‐Lise D.
Published: May 2004

The study of sex‐biased dispersal has attracted considerable attention in birds and mammals, but less in other taxa, including fishes. We analysed sex‐specific dispersal in historical (1910s and 1950s) and contemporary (1990s) samples of anadromous brown trout Salmo trutta. We tested the hypothesis that dispersal is unbiased using information from microsatellite DNA and applying an assignment index for 11 temporally and spatially separated samples. Our results are most consistent with brown trout dispersal being male biased, and provide no evidence of female bias. We found no evidence that dispersal patterns changed over time, indicating that stocking with hatchery strains did not affect sex‐specific dispersal.
Mitochondrial phylogeography of the moor frog, Rana arvalis
Authors: Babik W. , Branicki W. , Sandera M. , Litvinchuk S. , Borkin L. J. , Irwin J. T. , Rafiński J.
Published: May 2004

The moor frog Rana arvalis is a lowland species with a broad Eurasiatic distribution, from arctic tundra through forest to the steppe zone. Its present‐day range suggests that glacial refugia of this frog were located outside southern European peninsulas. We studied the species‐wide phylogeographical pattern using sequence variation in a 682 base pairs fragment of mtDNA cytochrome b gene; 223 individuals from 73 localities were analysed. Two main clades, A and B, differing by c. 3.6% sequence divergence were detected. The A clade is further subdivided into two subclades, AI and AII differing by 1.0%. All three lineages are present in the Carpathian Basin (CB), whereas the rest of the species range, including huge expanses of Eurasian lowlands, are inhabited solely by the AI lineage. We infer that AII and B lineages survived several glacial cycles in the CB but did not expand, at least in the present interglacial, to the north. The geographical distribution and genealogical relationships between haplotypes from the AI lineage indicate that this group had two glacial refugia, one located in the eastern part of the CB and the other probably in southern Russia. Populations from both refugia contributed to the colonization of the western part of the range, whereas the eastern part was colonized from the eastern refugium only. The effective population size as evidenced by θML is an order of magnitude higher in the AI lineage than in the AII and B lineages. Demographic expansion was detected in all three lineages.
Inbreeding and population structure in two pairs of cryptic fig wasp species
Authors: Molbo Drude , Machado Carlos A. , Herre Edward Allen , Keller Laurent
Published: May 2004

We used recently developed microsatellites to directly estimate inbreeding levels in two pairs of coexisting cryptic fig wasp species (‘Pegoscapus hoffmeyeri sp. A and sp. B’, ‘P. gemellus sp. A and sp. B’). Previous tests of Hamilton's local mate competition (LMC) theory in fig wasps have used the number of dead foundresses in a fig fruit to indirectly estimate the relative contribution of each to the common brood and thereby the level of local mate competition. Further, the population level of inbreeding has been indirectly estimated using the distribution of foundress numbers across broods. Our direct genetic estimates confirmed previous assumptions that the species characterized by lower foundress numbers showed higher relative levels of inbreeding. However, there were quantitative differences between the observed level of inbreeding and the expectation based on the distribution of foundress numbers in both pollinator species associated with Ficus obtusifolia. Here, genotype compositions of broods revealed that only 23% of fruits with multiple foundresses actually contained brood from more than one foundress, thus explaining at least part of the underestimate of actual sibmating. Within the four wasp species there was no evidence for genetic differentiation among the wasp populations sampled from different trees across 20 km and from different points in time. Further, no genotypic disequilibrium was detected within any of the species. Although F1 hybrids were observed between the two species pollinating F. obtusifolia, there was no evidence of genetic introgression. Finally, we found that 11% of the sons of allospecifically mated mothers were diploid hybrids suggesting a break down of the sex determination system in hybrids.
Single nucleotide polymorphism (SNP) discovery in mammals: a targeted‐gene approach
Authors: Aitken Nicola , Smith Steven , Schwarz Carsten , Morin Phillip A.
Published: May 2004

Single nucleotide polymorphisms (SNPs) have rarely been exploited in nonhuman and nonmodel organism genetic studies. This is due partly to difficulties in finding SNPs in species where little DNA sequence data exist, as well as to a lack of robust and inexpensive genotyping methods. We have explored one SNP discovery method for molecular ecology, evolution, and conservation studies to evaluate the method and its limitations for population genetics in mammals. We made use of ‘CATS’ (or ‘EPIC’) primers to screen for novel SNPs in mammals. Most of these primer sets were designed from primates and/or rodents, for amplifying intron regions from conserved genes. We have screened 202 loci in 16 representatives of the major mammalian clades. Polymerase chain reaction (PCR) success correlated with phylogenetic distance from the human and mouse sequences used to design most primers; for example, specific PCR products from primates and the mouse amplified the most consistently and the marsupial and armadillo amplifications were least successful. Approximately 24% (opossum) to 65% (chimpanzee) of primers produced usable PCR product(s) in the mammals tested. Products produced generally high but variable levels of readable sequence and similarity to the expected genes. In a preliminary screen of chimpanzee DNA, 12 SNPs were identified from six (of 11) sequenced regions, yielding a SNP on average every 400 base pairs (bp). Given the progress in genome sequencing, and the large numbers of CATS‐like primers published to date, this approach may yield sufficient SNPs per species for population and conservation genetic studies in nonmodel mammals and other organisms.
Adaptive radiation within New Zealand endemic species of the cockroach genus Celatoblatta Johns (Blattidae): a response to Plio‐Pleistocene mountain building and climate change
Authors: Chinn Warren G. , Gemmell Neil J.
Published: May 2004

The South Island of New Zealand offers unique opportunities to study insect evolution due to long‐term physical isolation, recent alpine habitats and high levels of biotic endemism. Using DNA sequence data from cytochrome oxidase subunit 1, we investigated the phylogeographical pattern among 10 endemic cockroach species within the genus Celatoblatta Johns (Blattidae). We tested the hypothesis that an ancestral cockroach species underwent rapid speciation in response to major climatic differentiation induced by mountain building. Results suggest that speciation was a twofold process, with an interspecific radiation of Pliocene/Pleistocene age followed by intraspecific diversification during the mid Pleistocene. Average genetic distance (maximum likelihood GTR + I + Γ) was 9.17%, with a maximum of 14.5%. Data revealed eight deep well‐supported branches, each with terminal clades. Six clades were differentiated according to morphological species, while the seventh was composed of three sympatric species. We consider the latter to be a phylogenetic species, possibly as a result of hybridization within a defined geographical area. This finding seriously challenges species distinctions for these three cockroach species. Correlation between genetic distances and a Climate Similarity Index (CSI) was negative, suggesting that species found in similar habitats are also genetically closely related. A Mantel test on within‐clade genetic distances vs. linear geographical distance was positive, suggesting allopatric isolation for those haplotypes. We present a model of speciation for South Island Celatoblatta.
Stocking impact and migration pattern in an anadromous brown trout (Salmo trutta) complex: where have all the stocked spawning sea trout gone?
Authors: Ruzzante Daniel E. , Hansen Michael M. , Meldrup Dorte , Ebert Kaare M.
Published: May 2004

We examined polymorphism at seven microsatellite loci among sea trout (Salmo trutta) (n = 846) collected from three areas in the Limfjord (Denmark). We then assessed their potential population source by comparing, using a mixed stock analysis (MSA) Bayesian framework, their genetic composition to that of brown trout collected from 32 tributaries pooled into nine geographical regions (n = 3801) and two hatcheries (n = 222) used for stocking. For each of the three regional sea trout groups (western, central and eastern Limfjord, n = 91, n = 426, n = 329, respectively), MSA was conducted with (i) all individuals in the group, (ii) with the subset of spawning sea trout only and (iii) with the subset of foraging, nonspawning individuals only, a subset that consisted primarily of sea trout caught during their first year at sea. For all three regional sea trout groups, a higher proportion of individuals (regardless of whether they were foraging or spawning) appear to have originated from the rivers that drain locally, than from the rivers that drain in other parts of the Limfjord. This suggests (1) that sea trout, at least during their first year at sea, undertake limited migrations within the Limfjord system and (2) that sea trout on their spawning run were caught close to their natal rivers. The proportion of sea trout of hatchery origin varied widely among all three Limfjord areas and broadly reflected regional stocking histories, with high proportions of sea trout of domestic origin in the east (39.3%), where stocking with domestic trout was practised intensely at the time of sampling, and in the west (57.2%), where a programme of coastal stocking of post smolts took place over several years in the early 1990s. In contrast, in the central Limfjord, where stocking with domestic trout was largely abandoned in the early 1990s, the proportion of sea trout of domestic origin was only 8.5%. Interestingly, for all three regional sea trout groups, virtually no sea trout of hatchery origin were found among the spawning individuals, which were on average larger than the nonspawning sea trout. These results suggest that stocked domestic brown trout that become anadromous experience high mortality at sea and are therefore largely absent among the larger, spawning individuals. We conclude that sea trout of domestic origin exhibit much reduced ability to reproduce and are unlikely to contribute significantly to the local gene pool largely because of a relatively high mortality at sea before the onset of maturity.
High similarity between flanking regions of different microsatellites detected within each of two species of Lepidoptera:Parnassius apolloandEuphydryas aurinia
Authors: Meglecz Emese , Petenian Frederic , Danchin Etienne , D’Acier Armelle Coeur , Rasplus Jean‐Yves , Faure Eric
Published: May 2004

Microsatellite flanking regions have been compared in two butterfly species. Several microsatellite flanking regions showed high similarity to one another among different microsatellites within a same species, but very few similarities were found between species. This can be the consequence of either duplication/multiplication events involving large regions containing microsatellites or of microsatellites imbedded in minisatellite regions. The multiplication of microsatellites might also be linked to mobile elements. Furthermore, crossing over between nonhomologous microsatellites can lead to the exchange of the flanking regions between microsatellites. The same phenomenon was observed in both studied butterfly species but not inAphis fabae(Hemiptera), which was screened at the same time using the same protocol. These findings might explain, at least partially, why microsatellite isolation in Lepidoptera has been relatively unsuccessful so far.
How species evolve collectively: implications of gene flow and selection for the spread of advantageous alleles
Authors: Morjan Carrie L. , Rieseberg Loren H.
Published: May 2004

The traditional view that species are held together through gene flow has been challenged by observations that migration is too restricted among populations of many species to prevent local divergence. However, only very low levels of gene flow are necessary to permit the spread of highly advantageous alleles, providing an alternative means by which low‐migration species might be held together. We re‐evaluate these arguments given the recent and wide availability of indirect estimates of gene flow. Our literature review ofFSTvalues for a broad range of taxa suggests that gene flow in many taxa is considerably greater than suspected from earlier studies and often is sufficiently high to homogenize even neutral alleles. However, there are numerous species from essentially all organismal groups that lack sufficient gene flow to prevent divergence. Crude estimates on the strength of selection on phenotypic traits and effect sizes of quantitative trait loci (QTL) suggest that selection coefficients for leading QTL underlying phenotypic traits may be high enough to permit their rapid spread across populations. Thus, species may evolve collectively at major loci through the spread of favourable alleles, while simultaneously differentiating at other loci due to drift and local selection.
Mitochondrial DNA variation in Northeast Atlantic and Mediterranean populations of Norway lobster, Nephrops norvegicus
Authors: Stamatis C. , Triantafyllidis A. , Moutou K. A. , Mamuris Z.
Published: May 2004

Analysis of the genetic structure of the Norway lobster (Nephrops norvegicus), a marine crustacean with high commercial value, was undertaken to gain information regarding the differentiation of Atlantic from Mediterranean populations of marine invertebrates. Restriction fragment length polymorphism analysis of two mitochondrial DNA segments, 3.6 kilobases in total, was performed. Twelve populations from the North Sea, Irish Sea, Portuguese coast and Aegean Sea were analysed. Low levels of differentiation were found among them (FST = 0.018, P < 0.001) and there were no signs of an Atlantic–Mediterranean divide or of an isolation‐by‐distance scheme of differentiation. Possible reasons for these low levels of differentiation can be found in the recent expansion of N. norvegicus populations. This is supported by the mismatch distribution of pairwise haplotype differences, as well as by the high mean haplotype diversity (h = 0.93) combined with medium nucleotide diversity (π = 0.0057) (in comparison to values for marine crustaceans or teleosts) found in this study. This combination of high levels of haplotype diversity with moderate to low levels of nucleotide diversity has also been frequently attributed to a recent time of divergence for various marine species. No evidence was found for a Mediterranean refugium during glaciation periods, separate from the Atlantic, as has been reported for some marine species. The Irish Sea population was the most differentiated as a result of reduced levels of diversity. Results are also discussed in the light of future management of N. norvegicus stocks.
Past and current gene flow in the selfing, wind‐dispersed species Mycelis muralis in western Europe
Authors: Chauvet S. , Van Der Velde M. , Imbert E. , Guillemin M. L. , Mayol M. , Riba M. , Smulders M. J. M. , Vosman B. , Ericson L. , Bijlsma R. , Giles B. E.
Published: May 2004

The distribution of genetic diversity in Mycelis muralis, or wall lettuce, was investigated at a European scale using 12 microsatellite markers to infer historical and contemporary forces from genetic patterns. Mycelis muralis has the potential for long‐distance seed dispersal by wind, is mainly self‐pollinated, and has patchily distributed populations, some of which may show metapopulation dynamics. A total of 359 individuals were sampled from 17 populations located in three regions, designated southern Europe (Spain and France), the Netherlands, and Sweden. At this within‐region scale, contemporary evolutionary forces (selfing and metapopulation dynamics) are responsible for high differentiation between populations (0.34 < FST < 0.60) but, contrary to expectation, levels of within‐population diversity, estimated by Nei's unbiased expected heterozygosity (HE) (0.24 < HE < 0.68) or analyses of molecular variance (50% of the variation found within‐populations), were not low. We suggest that the latter results, which are unusual in selfing species, arise from efficient seed dispersal that counteracts population turnover and thus maintains genetic diversity within populations. At the European scale, northern regions showed lower allelic richness (A = 2.38) than populations from southern Europe (A = 3.34). In light of postglacial colonization hypotheses, these results suggest that rare alleles may have been lost during recolonization northwards. Our results further suggest that mutation has contributed to genetic differentiation between southern and northern Europe, and that Sweden may have been colonized by dispersers originating from at least two different refugia.
Molecular evidence for the hybrid origin of species in the soft coral genusAlcyonium(Cnidaria: Anthozoa: Octocorallia)
Authors: Mcfadden Catherine S. , Hutchinson M. Breton
Published: May 2004

Several recent studies have suggested that hybridization may play a previously unrecognized and important role in the evolution of corals. Our observations of polymorphic and recombinant sequences in the multicopy ribosomal internal transcribed spacer (ITS) region suggested the possible hybrid origin of two European soft coral species,Alcyonium hibernicumandBellonella bocagei. To examine this possibility further we cloned and sequencedITS‐1from multiple individuals and populations of these two species as well as two sympatric congeners,A. coralloidesandA.sp.M2. Phylogenetic analyses separated the observed sequence variants into two distinct clades. AllA. coralloidessequences belonged to clade A, whileA.sp.M2 had only clade B sequences. A majority ofA. hibernicumindividuals, however, contained both clade A and B sequences that were identical to the predominant sequence variants found inA. coralloidesandA.sp.M2, respectively. This pattern of additivity suggests thatA. hibernicumoriginated from a hybrid cross betweenA. coralloidesandA.sp.M2, a hypothesis that is supported by its unusual mode of reproduction (meiotic parthenogenesis). The predominant sequence variant found inB. bocageiwas a unique, derived clade B sequence; in addition, however, most individuals of this species also had copies of a sequence identified as a recombinant between clade A and clade B sequence types. The presence of this recombinant sequence in theB. bocageigenome suggests that this species may also be the product of past hybridization events within the clade. Reticulate evolution may explain the failure of several previous studies to resolve the phylogeny of these four species.
Mitochondrial DNA and microsatellite variation in the eider duck (Somateria mollissima) indicate stepwise postglacial colonization of Europe and limited current long‐distance dispersal
Authors: Tiedemann R. , Paulus K. B. , Scheer M. , Von Kistowski K. G. , Skírnisson K. , Bloch D. , Dam M.
Published: May 2004

To unravel the postglacial colonization history and the current intercolony dispersal in the common eider, Somateria mollissima, we analysed genetic variation at a part of the mitochondrial control region and five unlinked autosomal microsatellite loci in 175 eiders from 11 breeding colonies, covering the entire European distribution range of this species. As a result of extreme female philopatry, mitochondrial DNA differentiation is substantial both among local colonies and among distant geographical regions. Our study further corroborates the previous hypothesis of a single Pleistocene refugium for European eiders. A nested clade analysis on mitochondrial haplotypes suggests that (i) the Baltic Sea eider population is genetically closest to a presumably ancestral population and that (ii) the postglacial recolonization progressed in a stepwise fashion via the North Sea region and the Faroe Islands to Iceland. Current long‐distance dispersal is limited. Differentiation among colonies is much less pronounced at microsatellite loci. The geographical pattern of this nuclear genetic variation is to a large extent explained by isolation by distance. As female dispersal is very limited, the geographical pattern of nuclear variation is probably explained by male‐mediated gene flow among breeding colonies. Our study provides genetic evidence for the assumed prominent postglacial colonization route shaping the present terrestrial fauna of the North Atlantic islands Iceland and the Faroes. It suggests that this colonization had been a stepwise process originating in continental Europe. It is the first molecular study on eider duck populations covering their entire European distribution range.
Contrasting population genetic patterns and evolutionary histories among sympatric Sonoran Desert cactophilic Drosophila
Authors: Hurtado L. A. , Erez T. , Castrezana S. , Markow T. A.
Published: May 2004

We studied population genetic differentiation in the sympatric Sonoran Desert cactophilic flies Drosophila pachea, D. mettleri and D. nigrospiracula across their continental and peninsular ranges. These flies show marked differences in ecology and behaviour including dispersal distances and host cactus specialization. Examination of a fragment of the mitochondrial cytochrome oxidase subunit I gene (mtCOI) reveals that the Sea of Cortez has constituted an effective dispersal barrier for D. pachea, leading to significant genetic differentiation between the continental and peninsular ranges of this species. No genetic differentiation was detected, however, within its continental and peninsular ranges. In contrast, our mtCOI‐based results for D. mettleri and D. nigrospiracula are consistent with a previous allozyme‐based study that showed no significant genetic differentiation between continental and peninsular ranges of these two species. For D. mettleri, we also found that the insular population from Santa Catalina Island, California, is genetically differentiated with respect to continental and peninsular localities. We discuss how differences in the genetic structure patterns of D. pachea, D. mettleri and D. nigrospiracula may correspond to differences in their dispersal abilities, host preferences and behaviour.
Phylogeography of subterranean and surface populations of water lice Asellus aquaticus (Crustacea: Isopoda)
Authors: Verovnik R. , Sket B. , Trontelj P.
Published: May 2004

The water louse Asellus aquaticus is a widespread, euryoecious species, mostly uniform throughout its range. However, six subspecies are known from the Dinaric karst in the northwestern Balkans. They include some specialized subterranean populations. The pattern of genetic variation among subterranean and surface populations in this hydrographically highly fragmented karst region was investigated using a 653 bp fragment of the mitochondrial gene (COI). Sequencing of 168 individuals from 25 localities revealed 72 haplotypes. amova and methods of phylogenetic reconstruction all uncovered hydrographic structuring of genetic variation of the populations. Nested clade analysis pointed out several fragmentation events, along with some range expansions within hydrographical systems. By superimposing the subterranean mode of life on the phylogeographical pattern, three independent cave colonizations could be inferred within a distance of < 100 km. Caves were invaded after the ancestral surface populations became isolated through vicariant fragmentation. A possible scenario of hydrographic history of the region was constructed combining the molecular data with palaeogeographical information.
Extra‐pair paternity does not result in differential sexual selection in the mutually ornamented black swan (Cygnus atratus)
Authors: Kraaijeveld K. , Carew P. J. , Billing T. , Adcock Greg J. , Mulder Raoul A.
Published: May 2004

We studied patterns of parentage in 85 broods (332 cygnets) of black swans during three breeding seasons, using a set of eight polymorphic microsatellite markers. We detected both intraspecific brood parasitism (IBP; < 5% of cygnets per year) and extra‐pair paternity (EPP). In these years, 10–17% (mean = 15.1%) of cygnets resulted from EPP, and 27–40% (mean 37.6%) of broods contained at least one extra‐pair cygnet. Compared with levels of EPP in closely related species with similar life histories, these values are unexpectedly high. EPP in black swans appears unrelated to ecological factors (breeding density and synchrony) or genetic factors (genetic similarity between pair members or genetic quality of the offspring). We found no evidence that a mutual sexual feather ornament known to play a role in social mate choice in black swans (curled wing feathers) is involved in extra‐pair mate choice. EPP does not lead to greater variance in reproductive success in males, relative to females in this species. We therefore suggest that EPP does not result in differential sexual selection on males and females, explaining why they are ornamented to the same degree.
Reproductive success and effective population size in woodrats (Neotoma macrotis)
Authors: Matocq M. D.
Published: May 2004

Discrepancies between the census size and the genetically effective size of populations (Ne) can be caused by a number of behavioural and demographic factors operating within populations. Specifically, strong skew in male reproductive success, as would be expected in a polygynous mating system, could cause a substantial decrease in Ne relative to census size. Because the mating system of Neotoma macrotis had previously been described as one nearing harem polygyny, I examined the distribution of reproductive success and genetic variation within a population of this species. Combining genetic data and three years of field observations, I show that variance in reproductive success does not deviate from poisson expectations within either sex and variance in success is similar between the sexes. Furthermore, both males and females had multiple partners across litters in addition to some evidence of multiple paternity within litters. Despite a lack of strong skew in reproductive success, an estimate of Ne based on a number of demographic parameters suggests that the ratio of Ne/N in this population is 0.48. Although the ratio of Ne/N suggests that the population is experiencing higher rates of genetic drift than would be expected based on census size alone, the population maintains high levels of genetic diversity. Estimates of neighbourhood size and patterns of recruitment to the study site suggest that immigration plays an important role in this population and may contribute to the maintenance of high levels of genetic diversity.
Phylogeographical lineages of Arctic grayling (Thymallus arcticus) in North America: divergence, origins and affinities with EurasianThymallus
Authors: Stamford M.D. , Taylor E.B.
Published: May 2004

The number and location of Arctic glacial refugia utilized by taxa during the Pleistocene are continuing uncertainties in Holarctic phylogeography. Arctic grayling (Thymallus arcticus) are widely distributed in freshwaters from the eastern side of Hudson Bay (Canada) west to central Asia. We studied mitochondrial DNA (mtDNA) and microsatellite DNA variation in North AmericanT. arcticusto test for genetic signatures of survival in, and postglacial dispersal from, multiple glacial refugia, and to assess their evolutionary affinities with EurasianThymallus. In samples from 32 localities, we resolved 12 mtDNA haplotypes belonging to three assemblages that differed from each other in sequence by between 0.75 and 2.13%: a ‘South Beringia’ lineage found from western Alaska to northern British Columbia, Canada; a ‘North Beringia’ lineage found on the north slope of Alaska, the lower Mackenzie River, and to eastern Saskatchewan; and a ‘Nahanni’ lineage confined to the Nahanni River area of the upper Mackenzie River drainage. Sequence analysis of a portion of the control region indicated monophyly of all North AmericanT. arcticusand their probable origin from eastern SiberianT. arcticusat least 3 Mya. Arctic grayling sampled from 25 localities displayed low allelic diversity and expected heterozygosity (HE) across five microsatellite loci (means of 2.1 alleles and 0.27HE, respectively) and there were declines in these measures of genetic diversity with distance eastward from the lower Yukon River Valley. Assemblages defined by mtDNA divergences were less apparent at microsatellite loci, but again the Nahanni lineage was the most distinctive. Analysis of molecular variance indicated that between 24% (microsatellite DNA) and 81% (mtDNA) of the variance was attributable to differences among South Beringia, North Beringia and Nahanni lineages. Our data suggest that extant North American Arctic grayling are more diverse phylogeographically than previously suspected and that they consist of at least three major lineages that originated in distinct Pleistocene glacial refugia.T. arcticusprobably originated and dispersed from Eurasia to North America in the late to mid‐Pliocene, but our data also suggest more recent (mid–late Pleistocene) interactions between lineages across Beringia.
Genetic equilibrium despite habitat fragmentation in an Afrotropical bird
Authors: Galbusera Peter , Githiru Mwangi , Lens Luc , Matthysen Erik
Published: May 2004

We examined the effects of habitat fragmentation of the white‐starred robin Pogonocichla stellata metapopulation in the Taita Hills archipelago, a hotspot for biodiversity which was fragmented ~40 years ago. Using seven microsatellite markers, we analysed the robin's genetic structure and tested for equilibrium between migration and drift (testing the probability of decreased dispersal) as well as between mutation and drift (test for recent reduction in effective population size, i.e. bottlenecks). This metapopulation was found to retain relatively high levels of genetic variability (HE between 0.63 and 0.71) and to be in migration–drift equilibrium, suggesting that increased isolation between fragments did not have much effect on the dispersal between them. Furthermore, this equilibrium test greatly enhanced the interpretation of parameters (e.g. FST) assumed to have reached an equilibrium value. In contrast to previous findings on the related and sympatric Taita thrush Turdus helleri (which is critically endangered), there were no indications for recent bottlenecks in any of the robin subpopulations. This difference can be attributed to the higher dispersal capacity of the robin compared with the thrush (deduced from both the genetic and capture–recapture data). Our results stress the importance of sustained dispersal for species conservation.
Assessing variability in fecundity of Amaranthus powellii using a simulation model
Authors: Brainard D C , Bellinder R R
Published: May 2004

Estimates of weed fecundity and its variability are critical for the development of population dynamic models and for evaluating the long‐term consequences of weed management practices. The purpose of this research was to estimate Amaranthus powellii fecundity across years, seasons and competitive environments using a mechanistic model. Existing models were modified to account for weed responses to shade, and to dynamically simulate seed production among subthreshold densities of A. powellii. The model was parameterized and tested using five sets of field data in which A. powellii was grown either alone or with transplanted broccoli. The model overestimated A. powellii height, but predicted both dry weight and fecundity well. Mean simulated fecundity for A. powellii ranged from 0 to 268 000 seeds per plant depending on year, crop maturity date, relative time of emergence and location. Year‐to‐year variability in simulated fecundity was large with coefficients of variation ranging from 77 to 128 under low and high competitive environments respectively. Our results suggest that estimates of weed fecundity based on 1 or 2 years of empirical data may result in significant errors in population dynamic models, and that the use of economic optimum thresholds based on weed density alone entails considerable risks.
Evaluation of sampling methods and assessment of the sample size to estimate the weed seedbank in soil, taking into account spatial variability
Authors: Ambrosio L , Iglesias L , Marín C , Del Monte J P
Published: May 2004

As field sampling is time consuming, it is necessary to develop efficient sampling techniques to obtain accurate estimates of the weed seedbank in soil. The relative efficiency between sampling schemes depends on the spatial variability in weed seed density across agricultural fields. Spatial variability of the weed seed density was characterized by theoretical correlograms. A systematic sampling (square grill) scheme was considered and it was found that, taking into account spatial variability, this sampling scheme was more efficient than simple random sampling. As a result, the sample size can be reduced in comparison with that given in previous studies, where spatial correlation was ignored. The reduction depends on the correlation structure defined as a function of the ratio, τ, between the nugget effect and the sill of the variogram. The maximum reduction of the sample size, without loss of either precision or confidence level corresponds to the case where there is no nugget effect, τ = 0. The opposite extreme case, where the reduction is nil, corresponds to the case of a pure nugget effect τ = 1. The abaci based on given expressions are provided to determine the sample size in species whose spatial pattern can be fitted either to a Poisson or to a negative binomial distribution.
Use of lidocaine metabolism to test liver function during the long‐term follow‐up of liver transplant recipients
Authors: Conti Filoména , Dousset Bertrand , Cherruau Brigitte , Guérin Corinne , Soubrane Olivier , Houssin Didier , Calmus Yvon
Published: May 2004

Abstract:  Background/Aims:  The aim of this study was to assess the usefulness of the monoethylglycinexylidide (MEGX) test to monitoring the long‐term function of liver allografts.

Methods:  MEGX production was measured prospectively in 60 consecutive liver transplant recipients undergoing their annual review.

Results:  Median MEGX values in liver recipients (54 ng/mL; range 10–146) were lower than those found in healthy controls (78 ng/mL; range 44–118). MEGX values correlated negatively with alanine aminotransferase (ALT) activity (p = 0.004) and with the overall histological score (p = 0.01), and positively with sulfobromophthalein (BSP) and indocyanine green (ICG) clearances (p = 0.0002 and p = 0.002, respectively). A stepwise decline was observed with worsening liver fibrosis, from 71 ± 5 μg/L in patients with no fibrosis to 27 ± 9 μg/L in patients with bridging fibrosis (p = 0.002). BSP and ICG clearances correlated more closely than the MEGX test with the overall histological score (p = 0.001 and p = 0.001, respectively) and portal fibrosis (p = 0.002 and p = 0.001).

Conclusions:  The measurement of MEGX formation is a simple and non‐invasive method to monitor liver graft function. It may constitute a valuable tool for assessing the degree of fibrosis.
Cost‐minimization study comparing Simulect® vs. Thymoglobulin® in renal transplant induction
Authors: Lilliu H , Brun‐Strang C , Le Pen C , Büchler M , Al Najjar A , Priol G , Reigneau O , Lebranchu Y
Published: May 2004

Abstract:  Purpose:  Based on the data of clinical trial CHI‐F‐02 comparing the efficacy and safety of basiliximab (Simulect®) vs. anti‐thymocyte globulin (Thymoglobulin®) in renal transplant induction, we carried out an economic evaluation.

Method:  This pharmacoeconomic study was a cost‐minimization study, i.e. given the equivalent efficacy of the products, the strategy that minimized the cost of care was considered better. The cost of care was analyzed from the hospital perspective.

Material:  This ‘piggyback’ study of 100 patients estimated the direct medical costs incurred over 6 months of use of two strategies for renal transplant induction therapy. Direct medical costs are those of utilized medical resources: medications, hospital stays, dialysis, and physician visits and investigations not scheduled in the protocol.

Results:  In the Simulect® arm, significant reductions were found in the initial hospital stay duration and number of infectious episodes. Therefore, although the average cost of treatment was slightly higher with Simulect® than with Thymoglobulin® (2964 vs. 2298 Euros), the cost of the initial hospitalization was significantly lower in the Simulect® arm (10 907 vs. 11 967 Euros; p = 0.02). Furthermore the mean cost of infectious episodes was significantly lower in the Simulect® arm (1056 vs. 1790 Euros, p = 0.03). Cytomegalovirus infection accounted for a significantly smaller proportion of this cost in the Simulect® arm than in the Thymoglobulin® arm (30% vs. 53%, p = 0.001).

Conclusion:  This study showed direct medical cost savings of 1159 Euros per patient in the Simulect® arm, which more than compensated for the higher price of this immunosuppressive drug.
The long‐term outcome of kidney transplantation in patients under cyclosporine – a developing country experience
Authors: Rafique Moosa M.
Published: May 2004

Abstract:  The introduction of cyclosporine revolutionized the practice of solid organ transplantation. Although early studies showed better short‐term results, the long‐term benefits of cyclosporine appear to be more contentious. Our study investigated the outcome of sustained cyclosporine usage on patient and renal allograft survival in a developing country setting. All patients receiving primary renal transplants at our institution over a 23‐yr period were included and data analysed for patient and graft survival rates using the Kaplan–Meier actuarial method. The patients receiving cyclosporine were compared with historical controls receiving conventional treatment. Early graft survival was superior in patients under cyclosporine but this benefit disappeared after the first year. There was no significant improvement in early patient survival in patients under cyclosporine but late survival was better in patients under conventional treatment. In our setting cyclosporine only improves early graft survival and does not have long‐term benefit either on patient or graft survival.
Living donor transplantation of a pelvic kidney
Authors: Boughey Judy C , Emovon Osemwegie E , Afzal Fuad , Baliga Prabhakar , Rogers Jeffrey , Lin Angello , Chavin Kenneth , Rajagopalan PR
Published: May 2004

Abstract:  Pelvic kidneys are uncommon anomalies rarely utilized in kidney transplantation. We describe a successful case of living‐donor transplantation using a pelvic kidney in a 17‐month‐old infant with congenital renal dysplasia. The recipient had exhausted all options for renal replacement therapy, and urgent transplantation was considered a life saving treatment.
Synthesis and X‐ray study of the 6‐(N‐pyrrolyl)purine and thymine derivatives of 1‐aminocyclopropane‐1‐carboxylic acid
Authors: Cetina M. , Džolić Z. , Mrvoš‐Sermek D. , Hergold‐Brundić A. , Nagl A. , Mintas M.
Published: May 2004

Abstract:  The novel purine and pyrimidine derivatives of 1‐aminocyclopropane‐1‐carboxylic acid 1 and 2 were obtained by alkylation of 6‐(N‐pyrrolyl)purine and thymine with methyl 1‐benzamido‐2‐chloromethylcyclopropanecarboxylate. X‐ray crystal structure analysis shows that the cyclopropane rings in 1 and 2 posses Z‐configuration. The cyclopropane ring atoms and attached atoms of the benzamido and methoxycarbonyl moiety of both molecules are disposed perpendicularly to each other. The carbonyl oxygen of the methoxycarbonyl moiety adopts in both compounds a synperiplanar conformation with respect to the midpoint of the distal bond of the cyclopropane ring. The torsion angles φ and ψ for the 1‐aminocyclopropane‐1‐carboxylic acid residue in 1 and 2 correspond to a folded conformation, while the torsion angles ω define antiperiplanar conformation. Intermolecular hydrogen bonds connect the molecules of 1 into dimers. Each dimer is hydrogen‐bonded with four ethanol molecules, thus forming discrete unit. On the contrary, intermolecular hydrogen bonds link the molecules of 2 generating three‐dimensional network.
Analogues of arginine vasopressin modified in the N‐terminal part of the molecule with enantiomers of N‐methylphenylalanine
Authors: Kowalczyk W. , Derdowska I. , Dawidowska O. , Prahl A. , Hartrodt B. , Neubert K. , Slaninová J. , Lammek B.
Published: May 2004

Abstract:  Four new analogues of arginine vasopressin (AVP) substituted in positions 2 and 3 with all possible combinations of enantiomers of N‐methylphenylalanine were synthesized and studied to assess the influence of N‐methylation of the peptide bonds between the first three amino acids on the pharmacological properties of the resulting peptides. The next three analogues were designed to learn how the shortening of the peptide chain, by removal of one of the N‐methylphenylalanine residues, would affect pharmacological properties of the resulting compounds. The activity of the analogues was tested in the in vitro uterotonic, pressor and antidiuretic tests. None of the prepared analogues displayed significant biological activity with the exception of [Me‐d‐Phe2, Me‐Phe3]AVP and [Me‐d‐Phe2,3]AVP, which showed low antiuterotonic activity (pA2 = 6.6 and pA2 = 6.4, respectively). Our results, while not impressive in terms of biological activity, may be helpful for designing potent and selective oxytocin antagonists.
Difference in Web Construction Behavior at Newly Occupied Web Sites Between Two Cyclosa Species
Authors: Nakata Kensuke , Ushimaru Atushi
Published: May 2004

Animals make decisions based on subjective assessments of their environment. To determine their future foraging activities, animals probably assess food availability from past foraging experiences. Thus, foraging also functions as a way for animals to collect information, with the uncertainty of an assessment decreasing as foraging activity increases. This suggests that different needs for a correct assessment may affect the investment made in foraging activities. Orb‐web spiders sometimes relocate their webs and relocation rate differs among species. After web relocation, several spider species have been reported to construct the first webs at newly occupied web sites using less silk than usual, possibly to avoid the risk of an overinvestment at sites where food availability has not been determined. Nevertheless, they may pay a cost, because of inadequate decision‐making, if webs constructed with less silk convey less information and increase the uncertainty of an assessment. We expect that stronger site tenacity necessitates a greater requirement for correct assessment of web site and the degree to which spiders reduce the amount of web silk in the first web after web relocation is smaller in species that use the same site longer. To test this hypothesis, we examined web construction in two orb‐web spiders, Cyclosa octotuberculata and C. argenteoalba. At the same time we found that these two species exhibit different web‐site tenacity, as C. octotuberculata does not relocate its webs as frequently as does C. argenteoalba. After artificially induced web relocation, C. argenteoalba constructed webs that were initially smaller and contained only about 2/3 of the silk in control webs that were constructed at the original site. In contrast, C. octotuberculata did not exhibit such decreases in web size or in the amount of web silk used. This result is consistent with our hypothesis.
Role‐Reversed Nepotism Among Cubs and Sires in the Spotted Hyena (Crocuta crocuta)
Authors: Van Horn Russell C. , Wahaj Sofia A. , Holekamp Kay E.
Published: May 2004

Nepotism is widespread among parents and offspring, and is typically associated with fundamental asymmetries; parents can usually do more to help their offspring than vice versa, and the cost of a given nepotistic behavior is usually less for parents than for offspring. This may not be so among spotted hyenas (Crocuta crocuta); sires never achieve social rank equal to that of their cubs, to whom they provide no obvious paternal care. Nepotism by sires towards their cubs is thus socially constrained. However, the higher social status of cubs might offset cubs’ developmental disadvantages and permit nepotistic treatment of sires by offspring. We therefore sought to determine whether the interactions among spotted hyena cubs and adult males were influenced by kinship, using long‐term observations from one clan of spotted hyenas. Sires exhibited no overt nepotism towards their cubs in most behaviors, but they did associate more closely with their daughters than with unrelated control females. Sires also associated more closely with their daughters than with their sons, with whom they associated no more closely than they did with unrelated control males. Cubs favored their sires by directing less intense aggression towards them than towards unrelated control males. Cubs of both sexes also associated more closely with their sires than with control males after the cubs were independent of the clan's communal den. Although sires evidently recognize their offspring, paternal nepotism by sires towards their cubs is weaker than filial nepotism by cubs towards their sires. The small size and immaturity of cubs thus appear to be weaker constraints on nepotism than is the low social status of their sires.