bluuebunny/crossref_metadata_2025_split huggingface dataset:
Developmental pathways, homology and homonomy in metameric animals
Authors: Minelli Alessandro , Peruffo Beatrice 
Published: December 2004

AbstractFollowing Wagner's (1989) distinction between historical and biological concepts of homology, we analyze homology problems of metameric animals in the light of a biological concept. In identifying homology, we refer to the common informational background which two structures share. Therefore, homology relationships are matters of degree; they are ‘perfect’ only when there is full identity of informational background between the structures under comparison. Homonomy (serial homology) is not fundamentally different from other kinds of homology. We regard the differences between epimorphically and anamorphically developed segments as minor; therefore, the two kinds of segments are largely homologous. The morphogenetic processes giving rise to segmental structures are regarded as not necessarily hierarchical. We contrast the phylogenetic pattern of hierarchically nested homologies with a largely non‐hierarchical pattern of homologous structures within the individual organism. This topological difference adds to heterochrony in generating the widespread mismatch of ontogeny and phylogeny.
Sex‐linked altruism: A stepping‐stone in the evolution of social behavior?
Authors: Kawecki Tadeusz J. 
Published: December 2004

AbstractA verbal model is presented for a mechanism that enhances the probability of the evolution of altruism in diploids if the gene for altruism arises on the X chromosome. If the altruism takes place between sibs of the homogametic sex, the condition for spread of a sex‐linked gene for altruism is less stringent than for an autosomal gene. Then, with altruistic behavior present, selection for increased efficiency (benefit/cost ratio) may raise the efficiency above the autosomal threshold before autosomal modifiers are widespread enough to eliminate the behavior. The results of computer simulations confirms that, if the initial benefit/cost ratio is lower than 2, sex‐linkage can make the evolution of altruism more likely.
Environmentally induced morphological variation in the Barnacle Goose, Branta leucopsis
Authors: Larsson Kjell , Forslund Pär 
Published: December 2004

AbstractThe environmental conditions to which juvenile barnacle geese (Branta leucopsis) were exposed during growth were found to affect their body size at fledging as well as their final adult body size. Small juveniles showed compensatory growth from the time of fledging up to one year of age, but this did not fully compensate the differences in body size that were established before fledging. The variation in protein content in plants eaten during growth could probably explain the observed body size differences, sometimes of more than 10%, between different categories of adult geese. Our results imply that one cannot infer selection on morphological characters from differences between samples of adult birds from different localities or from different cohorts within a population, without first showing that environmental conditions during growth do not affect the development of the characters under study.
An experimental study of geographic variation in avian growth and development
Authors: Rhymer Judith M. 
Published: December 2004

AbstractReciprocal transplant and “common garden” experiments were done to distinguish the genetic and environmental components of geographic variation in growth, development and morphological characters of Mallard Ducks (Anas platyrhynchos) from California, USA and Manitoba, Canada. Most of the variation in growth and development could be attributed to differences in nesting phenology and local environmental conditions. Differences in morphological characters typical of birds in the two wild populations could be induced by transplanting young between localities. All differences between populations disappeared in the F1 offspring from captive breeding crosses, reared in a common environment. These results suggest that population‐level variation in growth, development and morphology of Mallards in the wild is environmentally induced.
Optimum body size: effects of food quality and temperature, when reproductive growth rate is restricted, with examples from aphids
Authors: Kindlmann Pavel , Dixon Anthony F. G. 
Published: December 2004

AbstractMost models of optimum energy partitioning predict variability in adult size, although not always explicitly. Increase in size is usually attributed to an increase in the growth rate or decline in mortality. The model presented shows that this may not always be the case. Even when mortality is kept constant in organisms with overlapping generations, a constraint on the maximum reproductive growth rate may lead, when the rate of overall growth increases, to either an increase or a decline in the optimum adult body size.It is shown that adult size could be a consequence of the differential responses of life history traits to changes in temperature and food quality. This is clearly advantageous for short lived organisms, like aphids, each generation of which only experience a very small part of the great seasonal range in conditions. This hypothesis complements Iwasa's (1991) explanation of the phenotypic plasticity observed in long lived organisms.The predictions are illustrated with empirical data from aphids. The model presented, which has been verified against a very large data set, indicates that for aphids the adult weight observed at a particular combination of temperature and food quality is that at which the population growth rate, rm, is maximized.We conclude that predictions about adult size from models based on the partitioning of energy are more likely to apply to organisms that scramble for resources, i.e., “r” selected species. The size of organisms that contest for resources is more likely to be determined by competitive status and avoidance of natural enemies.
The genetics of phenotypic plasticity. V. Evolution of reaction norm shape
Authors: Gavrilets Sergey , Scheiner Samuel M. 
Published: December 2004

AbstractWe present a general quantitative genetic model for the evolution of reaction norms. This model goes beyond previous models by simultaneously permitting any shaped reaction norm and allowing for the imposition of genetic constraints. Earlier models are shown to be special cases of our general model; we discuss in detail models involving just two macroenvironments, linear reaction norms, and quadratic reaction norms. The model predicts that, for the case of a temporally varying environment, a population will converge on (1) the genotype with the maximum mean geometric fitness over all environments, (2) a linear reaction norm whose slope is proportional to the covariance between the environment of development and the environment of selection, and (3) a linear reaction norm even if nonlinear reaction norms are possible. An examination of experimental studies finds some limited support for these predictions. We discuss the limitations of our model and the need for more realistic gametic models and additional data on the genetic and developmental bases of plasticity.
An unusual histone H4 gene from Tilapia nilotica exhibiting characteristics of both a replication‐dependent histone and a basal‐expression histone: evolutionary considerations
Authors: Englander E. , Moav B. , Tabachnik M. , Shuali Y. , Graur D. 
Published: December 2004

AbstractThe nucleotide sequence of a histone H4 gene from the fish Tilapia nilotica was determined. The deduced amino acid sequence is identical to that of H4 from the trout, Salmo gairdnerii. The 3′ untranslated region of the Tilapia gene exhibits a unique combination of structural features each of which is usually associated with either a replication‐dependent histone or a basal‐expression histone, but not with both. The direction of nucleotide substitutions in the Tilapia and Salmo lineages was inferred. The Tilapia gene was found to evolve faster and to exhibit a more biased pattern of substitution and codon usage than its Salmo homologue. This combination of features cannot be explained by either mutation or purifying selection. The rapid embryonic development of Tilapia prompts us to suggest that the molecular evolution of the histone H4 gene is driven by fixation of advantageous synonymous mutations.
Encephalization and the evolution of longevity in mammals
Authors: Hofman Michel A. 
Published: December 2004

AbstractAllometric principles account for most of the observed variation in maximum life span among mammals. When body‐size effects are controlled for, most of the residual variance in mammalian life span can be explained by variations in brain size, metabolic rate and body temperature. It is shown that species with large brains for a given body size and metabolic rate, such as anthropoid primates, also have long maximum life spans. Conversely, mammals with relatively high metabolic rates and low levels of encephalization, as in most insectivores and rodents, tend to have short life spans. The hypothesis is put forward that encephalization and metabolic rate, which may govern other life history traits, such as growth and reproduction, are the primary determinants directing the evolution of mammalian longevity.
How can a character be developmentally constrained despite variation in developmental pathways?
Authors: Wagner G. P. , Misof B. Y. 
Published: December 2004

AbstractA fundamental riddle of evolutionary developmental biology is the conservation of adult morphological patterns (Hall, 1992). Conservative patterns are either called body plans if they concern overall body design, or homologues if they concern parts of the body (Riedl, 1978; Roth, 1982; Sattler, 1984; Van Valen, 1982; Wagner, 1989a, 1989b). An adult pattern is considered conservative if it remains unchanged in spite of changes in function, as indicated by the original definition of homology by Owen, as a similarity of organs regardless of form and function (Owen, 1848). Conservation of anatomical features despite different adaptive pressures is naturally explained by developmental constraints (Wagner, 1986). However, this approach to explain the biological basis of homology is plagued by the fact that developmental pathways are often more variable than the characters that they produce (see Tab. 1) (Hall, 1992; Roth, 1988, 1991; Spemann, 1915; Wagner, 1989b). This is also true for any other application of the concept of developmental constraints. The widely held opinion that early stages of development are conservative because any early perturbation is likely to interfere with later development, is far from absolute, since a vast amount of data in comparative developmental biology speaks to developmental variation (see e.g. the examples in Tab. 1). The question then is, how can developmental constraints on adult variation be reconciled with the fact of developmental variation?
Genotypic variation in propensity for host alternation within a population of Pemphigus betae (Homoptera: Aphididae)
Authors: Moran Nancy , Seminoff Jeffrey , Johnstone Laurel 
Published: December 2004

AbstractIn a Utah canyon, the aphid Pemphigus betae shows both a complex life cycle, with alternation between a gall‐forming phase on cottonwood leaves and a root‐feeding phase on herbs, and a simple life cycle, with year‐round residence on roots. In order to determine the extent of clonal variation in life cycle, experiments using multiple sublines of individual clones were carried out in the laboratory and in the field. Previous studies suggested that both genetic and environmental factors underlie life cycle differences among subpopulations of aphids from different sites and different life cycle phases. The current study is the first assessment of clonal variation in propensity for host alternation within a natural population of aphids. In the laboratory experiment, clones showed highly significant differences in reproductive rates and in production of the host‐alternating migrants. In agreement with previous findings, clones originating from lineages that had alternated to cotton‐wood hosts in the previous year had lower average density and produced more migrants than clones originating from lineages that had remained on roots during the previous year.In order to ascertain how clonal variation and site‐specific environmental factors affect life cycle variation under natural conditions, clones from laboratory cultures were used to establish experimental colonies at two elevational sites within the canyon. Production of the host‐alternating migrants was affected strongly by clone‐x‐site interaction and was affected slightly by site.Results from both experiments indicate that loss of host alternation in P. betae could be effected through genetic change, environmental change, or both.
Molecular phylogeny of the Canary Island lacertids (Gallotia): mitochondrial DNA restriction fragment divergence in relation to sequence divergence and geological time
Authors: Thorpe Roger S. , McGregor Duncan P. , Cumming Alistair M. 
Published: December 2004

AbstractRestriction fragment length polymorphisms of 6 base pair recognising endonucleases are used to reconstruct the phylogeny of the endemic Canary Island lacertid, Gallotia. The division into conventional species is upheld by this molecular analysis and the western Canary Island lizard (G. galloti) and eastern Canary Island lizard (G. atlantica) are hypothesized to be sister species. A more comprehensive study of the intraspecific relationships of G. galloti, based on nineteen restriction enzymes, indicates that there are distinct southern and northern lineages within this species. The phylogenetic analysis does not uphold the conventional subspecies, but suggests an alternative arrangement with one northern (La Palma, Tenerife) and one southern (Gomera, Hierro) subspecies. The inferred timing of molecular divergence of populations of G. galloti, based on RFLP analysis, is compatible with the geological timing for island origin and fossil data. Mantel tests show that mitochondrial RFLP divergence is correlated with mitrochondrial 12s rRNA and cytochrome oxidase I sequence divergence and highly correlated with mitochondrial cytochrome b sequence divergence.
Genetic variation in a phylogenetic context: Responses of two specialized leaf beetles (Coleoptera: Chrysomelidae) to host plants of their congeners
Authors: Futuyma Douglas J. , Walsh Joseph S. , Morton Timothy , Funk Daniel J. , Keese Mark C. 
Published: December 2004

AbstractThis work explores the possibility that constraints on genetic variation guide host shifts and are responsible for the evolutionary conservatism of host affiliation in phytophagous insects. To this end, we used full‐ and half‐sib breeding designs to screen two species of the North American bettle genus Ophraella for genetic variation in larval and adult feeding responses to several host plants of other species of Ophraella. All the plants are in the family Asteraceae. In O. conferta, we observed effectively no feeding response, and hence no genetic variation in response, to three of five test plant species; only those plants related to the species' natural hosts evoked genetically variable responses. In O. artemisiae, adults displayed genetic variation in response to a congener of the natural host, but not to two distantly related plants. However, significant variation among full‐sib broods in larval feeding suggests the existence of nonadditive genetic variance in feeding response to all five species of test plants—although survival was very low on most of them. The results suggest that patterns of presence versus apparent absence of detectable genetic variation may be related to the chemical similarity of plants to the insects' natural hosts, but not evidently to the phylogenetic history of host affiliation within the genus. Almost all genetic correlations in responses to host plants were not significantly different from zero; the few significant correlations were positive, and negative correlations that might explain host specificity were not found. Our data do not explain why exclusive shifts to new hosts should occur, but the apparent lack of genetic variation in responses to some plants suggests that the direction of host shifts is genetically constrained.
Parental control of sex ratio in Gammarus duebeni, an organism with environmental sex determination
Authors: Watt Penelope J. 
Published: December 2004

AbstractParental sex ratio control was investigated in Gammarus duebeni, an amphipod with an environmentally mediated sex determining system. The effect on the F2 generation sex ratio of the photoperiodic conditions experienced by a) the P generation during and after copulation, b) the F1 generation before and after sex determination, and c) the F2 generation themselves during the period of sex determination, was tested. The photoperiodic conditions the F2 generation experienced during the period of sex determination had a significant effect on their sex ratio (more males were produced under long‐day than under short‐day conditions), but the photoperiodic conditions experienced by the F1 generation males and females or the P generation on the F1 male's side had no effect on the F2 sex ratio. However, the photoperiodic conditions the P generation on the F1 female's side experienced significantly affected the F2 sex ratio. When these animals experienced long‐day conditions the F2 generation became female biased and when they experienced short‐day conditions, male biased. It is proposed that the mechanism of control operates through the F1 generation mothers whilst in an embryonic stage of development in the P generation mother's brood pouch. The photoperiodically mediated effects of the embryonic F1 generation mother and the F2 generation on sex determination are additive. A mechanism by which both F1 generation maternal and F2 generation sex ratio control could operate in the field is proposed.
Comparison of molecular and paleontological data in diatoms suggests a major gap in the fossil record
Authors: Philippe Hervé , Sörhannus Ulf , Baroin Anne , Perasso Roland , Gasse Françoise , Adoutte André 
Published: December 2004

AbstractDiatoms, unicellular eukaryotic algae with a siliceous skeleton, offer the rare advantage of displaying both an extensive fossil record and numerous extant species, thus providing the opportunity of confronting molecular and paleontological data in a protist group. A portion of the 28S ribosomal RNA was sequenced from 5 diatoms, the divergence times of which are well known. The nucleotide substitution rate was estimated in these unicellular eukaryotes and compared with the rate of multicellular eukaryotes, using a broad data base comprising metazoans and metaphytes. When using fossil record derived divergence times, our results show that the nucleotide substitution rate is about 5 times faster in diatoms than in chordates. But, when using the relative rate test, it is observed that, over a long time period, the nucleotide substitution rate may in fact have been slightly slower in diatoms than in chordates. For this contradiction, two possible explanations are proposed: (i) a failure of the relative rate test, (ii) a gap in the pre‐Jurassic diatom fossil record. We have checked that our results concerning the relative rate test were valid. Thus, the second hypothesis, which implies pre‐Jurassic diatom evolution, in fact already suggested by some non‐molecular evidences, is favoured. Decoupling of morphological differentiation from genetic speciation also appears to have occurred and may account in part for the underestimation of the dates of recent cladogenesis events.
Sexual isolation in Drosophila. II. Intraspecific variation in mate recognition systems
Authors: Marín Ignacio 
Published: December 2004

AbstractA simple behavioral model is used to investigate whether differences in the specific‐mate‐recognition system (SMRS), occur within species of the Drosophila genus. This model takes into account, and overcomes, the distorting effect of vigor differences on experimental results. Analysis shows significant deviations from the expected values under the assumption of identical SMRSs in around one fifth of the multiple‐choice experiments performed with natural strains of twelve different Drosophila species. Different selection procedures raise the number of significant assortative mating results between strains of D. melanogaster and D. pseudoobscura from 3.0% to 32.8%. Finally, sub‐ or semispecific taxa show variations in their SMRS even more frequently (74.5%). Differences in male vigor and female receptivity are also found. These results show that a classification of Drosophila species based on SMRS stability, as proposed by the “Recognition concept of species”, is virtually impossible.
Habitats, stress, and evolutionary rates
Authors: Parsons P. A. 
Published: December 2004

AbstractHabitats of organisms are expressed as an interaction between stress intensity, magnitude of environmental fluctuations, and energy availability from resources. Under this model organisms should evolve broad biological properties defined by such physical characteristics. When energy is severely restricted under the continuing constant stress of adversity‐selection, or in widely fluctuating and highly stressful environments, little evolutionary change is expected; relict species and ‘living fossils’ are the respective expectations. In rather stable abiotic environments where resources are limited habitat preferences may develop leading to specialization and ultimately adaptive radiations. On the other hand major new innovations are more likely in highly disturbed resource‐rich habitats. Evidence from the living and fossil biota is presented which is consistent with these conclusions.
Evolution in natural and experimental populations of Amphicarpaea bracteata
Authors: Parker Matthew A. 
Published: December 2004

AbstractGenetically divergent lineages (biotypes) often coexist within local populations of the selfing annual Amphicarpaea bracteata (Leguminosae). At one site, a rapid change in lineage frequency was observed, with one biotype decreasing from 41% to 16% of the population over a 2 year period. During 6 additional years of censuses, this lineage showed no tendency to recover to its former abundance. An experimental population was constructed with approximately equal numbers of individuals from the two dominant biotypes in this population, and plants were allowed to grow and reproduce without interference for 3 generations. The same lineage that declined in the natural habitat was also strongly selected against in this experimental population, with a selection coefficient (0.57 per generation) comparable to that inferred from the initial decline in frequency of this lineage in nature (0.47). A greenhouse experiment suggested that differential adaptation to high vs. low light environments could be one factor affecting relative success of these lineages. Differences in reproductive allocation and disease resistance to local pathogens are also key factors likely to affect relative fitness. Overall, these results show that the genetic structure of selfing plant populations can be highly dynamic, with intense selection and sudden shifts in relative abundance of different lineages.
Origin of the crustacean schizoramous limb: A re‐analysis of the duplosegmentation hypothesis
Authors: Zrzavý J. , Štys P. 
Published: December 2004

AbstractEmerson and Schram's hypothesis of a duplosegmental origin of the crustacean schizoramous (biramous) limb is confronted with new data on the phylogeny of arthropods and their mechanisms of development. The hypothesis is considered to be falsified since (a) the cephalic segments of the crustaceans bear schizoramous limbs but still seem to be homologous to those of the hexapods; (b) the embryonic origin of crustacean segments, limbs, and neuromeres appears to be the same as in the hexapods; (c) no genetic mechanism allowing for duplosegmentation in the crustaceans seems to exist.