bluuebunny/crossref_metadata_2025_split huggingface dataset:
The digestive performance of mammalian herbivores: why big may not be that much better
Authors: CLAUSS MARCUS , HUMMEL JÜRGEN 
Published: May 2005

ABSTRACT 1. A traditional approach to the nutritional ecology of herbivores is that larger animals can tolerate a diet of lesser quality due to a higher digestive efficiency bestowed on them by comparatively long ingesta retention times and lower relative energy requirements. 2. There are important physiological disadvantages that larger animals must compensate for, namely a lower gut surface : gut volume ratio, larger ingesta particle size and greater losses of faecal bacterial material due to more fermentation. Compensating adaptations could include an increased surface enlargement in larger animals, increased absorption rates per unit of gut surface, and increased gut motility to enhance mixing of ingesta. 3. A lower surface : volume ratio, particularly in sacciform forestomach structures, could be a reason for the fact that methane production is of significant scope mainly in large herbivores and not in small herbivores with comparably long retention times; in the latter, the substrate for methanogenesis – the volatile fatty acids – could be absorbed faster due to a more favourable gut surface : volume ratio. 4. Existing data suggest that in herbivores, an increase in fibre digestibility is not necessarily accompanied by an increase in overall apparent dry matter digestibility. This indicates a comparative decrease of the apparent digestibility of non‐fibre material, either due to a lesser utilization of non‐fibre substrate or an increased loss of endogenous/bacterial substance. Quantitative research on these mechanisms is warranted in order to evaluate whether an increase in body size represents a net increase of digestive efficiency or just a shift of digestive focus.
The recolonization of Europe by brown bears Ursus arctos Linnaeus, 1758 after the Last Glacial Maximum
Authors: SOMMER R. S. , BENECKE N. 
Published: May 2005

ABSTRACT 1. At the end of the Last Glacial Maximum brown bears Ursus arctos recolonized the glacial landscape of Central and Northern Europe faster than all other carnivorous mammal species of the Holocene fauna. Ursus arctos was recorded in Northern Europe from the beginning of the Late‐Glacial. The recolonization of northern Central Europe may have taken place directly after the maximum glaciation. The distribution of the brown bear was restricted to glacial refugia only during the Last Glacial Maximum, for probably no more than 10 000 years. 2. Genetic analyses have suggested three glacial refugia for the brown bear: the Iberian Peninsula, the Italian Peninsula and the Balkans. Subfossil records of Ursus arctos from north‐western Moldova as well as reconstructed environmental conditions during the Last Glacial Maximum in this area suggest to us a fourth glacial refuge for the brown bear. Because of its connection to the Carpathians, we designate this as the ‘Carpathian refuge’. 3. Due to the low genetic distance between brown bears of northern Norway, Finland, Estonia, north‐eastern Russia and the northern Carpathians (the so‐called eastern lineage), the Carpathians were considered the geographical origin of the recolonization of these regions. During the recolonization of northern Europe the brown bear probably reached these areas rapidly from the putative Carpathian refuge.
Understanding mammalian evolution using Bayesian phylogenetic inference
Authors: KELLY CLINT D. 
Published: May 2005

ABSTRACT 1. Phylogenetic trees are critical in addressing evolutionary hypotheses; however, the reconstruction of a phylogeny is no easy task. This process has recently been made less arduous by using a Bayesian statistical approach. This method offers the advantage that one can determine the probability of some hypothesis (i.e. a phylogeny), conditional on the observed data (i.e. nucleotide sequences). 2. By reconstructing phylogenies using Bayes’ theorem in combination with Markov chain Monte Carlo, phylogeneticists are able to test hypotheses more quickly compared with using standard methods such as neighbour‐joining, maximum likelihood or parsimony. Critics of the Bayesian approach suggest that it is not a panacea, and argue that the prior probability is too subjective and the resulting posterior probability is too liberal compared with maximum likelihood. 3. These issues are currently debated in the arena of mammalian evolution. Recently, proponents and opponents of the Bayesian approach have constructed the mammalian phylogeny using different methods under different conditions and with a variety of parameters. These analyses showed the robustness (or lack of) of the Bayesian approach. In the end, consensus suggests that Bayesian methods are robust and give essentially the same answer as maximum likelihood methods but in less time. 4. Approaches based on fossils and molecules typically agree on ordinal‐level relationships among mammals but not on higher‐level relationships, as Bayesian analyses recognize  the African radiation, Afrotheria, and the two Laurasian radiations, Laurasiatheria and Euarchontoglires, whereas fossils did not predict Afrotheria.
Historic and current habitat use by North Pacific right whales Eubalaena japonica in the Bering Sea and Gulf of Alaska
Authors: SHELDEN KIM E. W. , MOORE SUE E. , WAITE JANICE M. , WADE PAUL R. , RUGH DAVID J. 
Published: May 2005

ABSTRACT 1. To help define areas and ecological parameters critical to the survival and recovery of the remnant population of North Pacific right whales, habitat use was investigated by examining all available sighting and catch records in the south‐eastern Bering Sea (SEBS) and Gulf of Alaska (GOA) over the past two centuries. 2. Based on re‐analyses of commercial whaling records, search effort, and resultant catches and sightings, waters of the: (i) SEBS slope and shelf, (ii) eastern Aleutian Islands and (iii) GOA slope and abyssal plain were important habitat for North Pacific right whales through the late 1960s. 3. Since 1980, the only area where right whales have been seen consistently is on the SEBS middle shelf. However, acoustic detections and single sightings have been reported in all other regions except the SEBS slope and oceanic GOA (areas where little, if any, acoustic and visual effort has occurred). 4. Sightings since 1979 were in waters < 200 m deep which may simply reflect the paucity of search effort elsewhere. From the commercial whaling era to the late 1960s, right whales were commonly seen in waters > 2000 m deep, indicating that their distribution is not restricted to shallow continental shelves. 5. North Pacific right whale sightings through the centuries have been associated with a variety of oceanic features, and there is little in common in the bathymetry of these regions. These whales appear to have a greater pelagic distribution than that observed in the North Atlantic, which may be related to the availability of larger copepods across the SEBS and GOA.
Microsatellite and mitochondrial DNA analyses of the genetic structure of blacktip shark (Carcharhinus limbatus) nurseries in the northwestern Atlantic, Gulf of Mexico, and Caribbean Sea
Authors: KEENEY D. B. , HEUPEL M. R. , HUETER R. E. , HEIST E. J. 
Published: May 2005

AbstractWe investigated the genetic structure of blacktip shark (Carcharhinus limbatus) continental nurseries in the northwestern Atlantic Ocean, Gulf of Mexico, and Caribbean Sea using mitochondrial DNA control region sequences and eight nuclear microsatellite loci scored in neonate and young‐of‐the‐year sharks. Significant structure was detected with both markers among nine nurseries (mitochondrial ΦST = 0.350, P < 0.001; nuclear ΦST = 0.007, P < 0.001) and sharks from the northwestern Atlantic, eastern Gulf of Mexico, western Gulf of Mexico, northern Yucatan, and Belize possessed significantly different mitochondrial DNA haplotype frequencies. Microsatellite differentiation was limited to comparisons involving northern Yucatan and Belize sharks with nuclear genetic homogeneity throughout the eastern Gulf of Mexico, western Gulf of Mexico, and northwestern Atlantic. Differences in the magnitude of maternal vs. biparental genetic differentiation support female philopatry to northwestern Atlantic, Gulf of Mexico, and Caribbean Sea natal nursery regions with higher levels of male‐mediated gene flow. Philopatry has produced multiple reproductive stocks of this commercially important shark species throughout the range of this study.
Measuring polyandry in wild populations: a case study using promiscuous crickets
Authors: BRETMAN AMANDA , TREGENZA TOM 
Published: May 2005

AbstractMating rate has important implications for patterns of sexual selection and sexual conflict and hence for issues such as speciation and the maintenance of genetic diversity. Knowledge of natural mating rates can provide insights into the factors driving female mating behaviour. We investigated the level of polyandry in a Spanish population of the field cricketGryllus bimaculatususing microsatellite markers. Two approaches were employed: (i) genotyping the offspring of wild‐caught gravid females to determine the number of males siring the brood and (ii) genotyping sperm stored in the spermathecae of females mated in the wild to estimate the number of mating partners. We compared existing methods for inferring the minimum and probable number of fathers and described a novel probabilistic technique estimating the number of mates by genotyping stored sperm. Using the most conservative allele‐counting method, 71% of females produced offspring sired by at least two males (a minimum mean of 2.4 fathers per clutch), and all females had mated to at least two males with minimum mean estimates of 2.7–5.1 mates per female. Our study reveals high levels of polyandry in the wild and suggests that females mate with more males than sire their offspring.
Range‐wide molecular analysis of the western pond turtle (Emys marmorata): cryptic variation, isolation by distance, and their conservation implications
Authors: SPINKS PHILLIP Q. , SHAFFER H. BRADLEY 
Published: May 2005

AbstractWe analysed phylogeography and population genetic variation across the range of the western pond turtle (Emys marmorata) using rapidly evolving mitochondrial and nuclear DNA sequence data. Nuclear DNA sequences from two unlinked introns displayed extremely low levels of variation, but phylogenetic analyses based on mtDNA recovered four well‐supported and geographically coherent clades. These included a large Northern clade composed of populations from Washington south to San Luis Obispo County, California, west of the Coast Ranges; a San Joaquin Valley clade from the southern Great Central Valley; a geographically restricted Santa Barbara clade from a limited region in Santa Barbara and Ventura counties; and a Southern clade that occurs south of the Tehachapi Mountains and west of the Transverse Range south to Baja California, Mexico. An analysis of molecular variance (amova) based on regional hydrographic units revealed that populations from the Sacramento Valley north to Washington were virtually invariant, with no evidence of population substructure among northern river drainage basins. In other areas,E. marmoratacontains considerable unrecognized variation, particularly in central and southern California and in northern Baja California, Mexico. Our northern clade is congruent with the distribution of the subspeciesEmys marmorata marmorata(Washington–central California). However, no clade is congruent with the distribution of the southern subspeciesEmys marmorata pallidafrom central California–Baja. Thus, recognition of the current subspecies split is not warranted, based on the available genetic evidence. Ouramovaand phylogenetic results, in conjunction with a growing comparative database for other codistributed aquatic taxa, confirm the occurrence of genetic breaks across the Tehachapi Mountains and Transverse Range bounding the southern end of the Great Central Valley, and point to southern California as a rich source of cryptic genetic variation.
Streams over mountains: influence of riparian connectivity on gene flow in the Pacific jumping mouse (Zapus trinotatus)
Authors: VIGNIERI SACHA N. 
Published: May 2005

AbstractIn species affiliated with heterogeneous habitat, we expect gene flow to be restricted due to constraints placed on individual movement by habitat boundaries. This is likely to impact both individual dispersal and connectivity between populations. In this study, a GIS‐based landscape genetics approach was used, in combination with fine‐scale spatial autocorrelation analysis and the estimation of recent intersubpopulation migration rates, to infer patterns of dispersal and migration in the riparian‐affiliated Pacific jumping mouse (Zapus trinotatus). A total of 228 individuals were sampled from nine subpopulations across a system of three rivers and genotyped at eight microsatellite loci. Significant spatial autocorrelation among individuals revealed a pattern of fine‐scale spatial genetic structure indicative of limited dispersal. Geographical distances between pairwise subpopulations were defined following four criteria: (i) Euclidean distance, and three landscape‐specific distances, (ii) river distance (distance travelled along the river only), (iii) overland distance (similar to Euclidean, but includes elevation), and (iv) habitat‐path distance (a least‐cost path distance that models movement along habitat pathways). Pairwise Mantel tests were used to test for a correlation between genetic distance and each of the geographical distances. Significant correlations were found between genetic distance and both the overland and habitat‐path distances; however, the correlation with habitat‐path distance was stronger. Lastly, estimates of recent migration rates revealed that migration occurs not only within drainages but also across large topographic barriers. These results suggest that patterns of dispersal and migration in Pacific jumping mice are largely determined by habitat connectivity.
Spatial genetic structure of northern pike (Esox lucius) in the Baltic Sea
Authors: LAIKRE LINDA , MILLER LOREN M. , PALMÉ ANNA , PALM STEFAN , KAPUSCINSKI ANNE R. , THORESSON GUNNAR , RYMAN NILS 
Published: May 2005

AbstractThe genetic relationships among 337 northern pike (Esox lucius) collected from the coastal zone of the central Baltic region and the Finnish islands of Åland were analysed using five microsatellite loci. Spatial structure was delineated using both traditional F‐statistics and individually based approaches including spatial autocorrelation analysis. Our results indicate that the observed genotypic distribution is incompatible with that of a single, panmictic population. Isolation by distance appears important for shaping the genetic structure of pike in this region resulting in a largely continuous genetic change over the study area. Spatial autocorrelation analysis (Moran's I) of individual pairwise genotypic data show significant positive genetic correlation among pike collected within geographical distances of less than c. 100–150 km (genetic patch size). We suggest that the genetic patch size may be used as a preliminary basis for identifying management units for pike in the Baltic Sea.
Hybrid origin of a parthenogenetic genus?
Authors: MORGAN‐RICHARDS MARY , TREWICK STEVEN A. 
Published: May 2005

AbstractThe origin of the obligate‐parthenogenetic New Zealand stick insect genus Acanthoxyla was investigated using cytogenetics and sequencing of nuclear and mitochondrial DNA. Little mitochondrial DNA sequence variation (COI‐II) was found among seven species of the genus Acanthoxyla and we found no evidence for monophyly of the morphologically distinguished lineages. In contrast, two distinct clades of nuclear sequence (ITS) were obtained, one is restricted to the genus Acanthoxyla, while the other includes sequences obtained from its sister genus Clitarchus. Although Acanthoxyla appears to be diploid (2n = 36–38), it has two ill‐matched chromosome pairs. We hypothesize that two or more hybridization events involving the parental sexual species Clitarchus hookeri and an unknown taxon probably resulted in the formation of the parthenogenetic genus Acanthoxyla. However, the karyotype of Acanthoxyla bears little resemblance to the karyotype of the putative paternal species C. hookeri so the exact nature of Acanthoxyla remains in question.
Genetic diversity and population structure of an insular tree, Santalum austrocaledonicum in New Caledonian archipelago
Authors: BOTTIN L. , VERHAEGEN D. , TASSIN J. , OLIVIERI I. , VAILLANT A. , BOUVET J. M. 
Published: May 2005

AbstractWe present a study of the genetic diversity and structure of a tropical tree in an insular system. Santalum austrocaledonicum is endemic to the archipelago of New Caledonia and is exploited for oil extraction from heartwood. A total of 431 individuals over 17 populations were analysed for eight polymorphic microsatellite loci. The number of alleles per locus ranged from 3 to 33 and the observed heterozygosity per population ranged from 0.01 in Maré to 0.74 in Ile des Pins. The genetic diversity was lowest in the most recent islands, the Loyautés, and highest in the oldest island, Grande Terre, as well as the nearby small Ile des Pins. Significant departures from panmixia were observed for some loci–population combinations (per population FIS = 0–0.03 on Grande‐Terre and Ile des Pins, and 0–0.67 on Loyautés). A strong genetic differentiation among all islands was observed (FST = 0.22), and the amount of differentiation increased with geographic distance in Iles Loyauté and in Grande Terre. At both population and island levels, island age and isolation seem to be the main factors influencing the amount of genetic diversity. In particular, populations from recent islands had large average FIS that could not be entirely explained by null alleles or a Wahlund effect. This result suggests that, at least in some populations, selfing occurred extensively. Conclusively, our results indicate a strong influence of insularity on the genetic diversity and structure of Santalum austrocaledonicum.
Crop‐to‐weed introgression has impacted allelic composition of johnsongrass populations with and without recent exposure to cultivated sorghum
Authors: MORRELL P. L. , WILLIAMS‐COPLIN T. D. , LATTU A. L. , BOWERS J. E. , CHANDLER J. M. , PATERSON A. H. 
Published: May 2005

AbstractSorghum halepenseL. (johnsongrass) is one of the world's most noxious weeds, and a paradigm for the potential dangers of crop–weed hybridization. Introduced into the southeastern United States about 200 years ago,S. halepenseis a close relative of cultivated sorghum (Sorghum bicolor). Both artificial crossing and experimental field studies have demonstrated the potential forS. halepense×S. bicolorhybrid formation, but no prior study has addressed the long‐term persistence of sorghum genes in johnsongrass populations. We surveyed 283 loci (on all 10 sorghum linkage groups) to identify 77 alleles at 69 loci that are found in US sorghum cultivars but are absent from a worldwide sampling of johnsongrass genotypes. These putatively cultivar‐specific alleles were present in up to 32.3% of individuals in johnsongrass populations adjacent to long‐term sorghum production fields in Texas and Nebraska. Lower frequencies of cultivar‐specific alleles at smaller numbers of loci are found in johnsongrass populations from New Jersey and Georgia with no recent exposure to cultivated sorghum, suggesting that introgressed sorghum alleles may be dispersed across long distances. The number of cultivar‐specific alleles and extensive multilocus patterns of cultivar‐specific allelic composition observed at both linked and unlinked loci in the johnsongrass populations, are inconsistent with alternatives to introgression such as convergence, or joint retention of ancestral polymorphisms. Naturalized johnsongrass populations appear to provide a conduit by which transgenes from sorghum could become widely disseminated.
Cholinergic and noncholinergic brainstem neurons expressing Fos after paradoxical (REM) sleep deprivation and recovery
Authors: Verret Laure , Léger Lucienne , Fort Patrice , Luppi Pierre‐Hervé 
Published: May 2005

AbstractIt is well accepted that populations of neurons responsible for the onset and maintenance of paradoxical sleep (PS) are restricted to the brainstem. To localize the structures involved and to reexamine the role of mesopontine cholinergic neurons, we compared the distribution of Fos‐ and choline acetyltransferase‐labelled neurons in the brainstem of control rats, rats selectively deprived of PS for ≈ 72 h and rats allowed to recover from such deprivation. Only a few cholinergic neurons from the laterodorsal (LDTg) and pedunculopontine tegmental nuclei were Fos‐labelled after PS recovery. In contrast, a large number of noncholinergic Fos‐labelled cells positively correlated with the percentage of time spent in PS was observed in the LDTg, sublaterodorsal, alpha and ventral gigantocellular reticular nuclei, structures known to contain neurons specifically active during PS. In addition, a large number of Fos‐labelled cells were seen after PS rebound in the lateral, ventrolateral and dorsal periaqueductal grey, dorsal and lateral paragigantocellular reticular nuclei and the nucleus raphe obscurus. Interestingly, half of the cells in the latter nucleus were immunoreactive to choline acetyltransferase. In contrast to the well‐accepted hypothesis, our results strongly suggest that neurons active during PS, recorded in the mesopontine cholinergic nuclei, are in the great majority noncholinergic. Our findings further demonstrate that many brainstem structures not previously identified as containing neurons active during PS contain cholinergic or noncholinergic neurons active during PS, and these structures may therefore play a key role during this state. Altogether, our results open a new avenue of research to identify the specific role of the populations of neurons revealed, their interrelations and their neurochemical identity.
Abnormal activation of face processing systems at early and intermediate latency in individuals with autism spectrum disorder: a magnetoencephalographic study
Authors: Bailey Anthony J. , Braeutigam Sven , Jousmäki Veikko , Swithenby Stephen J. 
Published: May 2005

AbstractThe neurological basis of developmental psychopathology in autism is a matter of intense debate. Magnetoencephalography (MEG) was used to study the neuronal responses associated with the processing of faces in 12 able adults with autism spectrum disorders (ASD), performing image categorization and image identification tasks. The neuromagnetic data were analysed using nonparametric time‐series analysis and equivalent current dipole estimation. Comparison data were obtained from 22 normally developing adults. In individuals with ASD, the neural responses to images of faces, observed in right extrastriate cortices at ≈ 145 ms after stimulus onset, were significantly weaker, less lateralized and less affected by stimulus repetition than in control subjects. Early latency (30–60 ms) responses to face images, over right anterior temporal regions, differed significantly between the two subject groups in the image identification task. No such difference was observed for images of mugs or meaningless geometrical patterns. These findings suggest that, during the course of development in individuals with ASD, the cortical activity associated with the processing of human faces assumes a different‐from‐normal localization in extrastriate brain regions. This abnormal localization may be associated with unusual, but nevertheless face‐specific, fast processing pathways.