bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coming of age in fringillid birds: heterochrony in the ontogeny of secondary sexual characters
Authors: Björklund Mats 
Published: December 2004

AbstractThe great variation in the timing of development of adult plumages in North American male passerine birds has in recent years provoked much theoretical interest. It has commonly been assumed that the heterochronic process involved is invariably a retardation of the development of adult plumages. On the basis of a phylogenetic analysis of the nine‐primaried oscines (Fringillidae), I suggest that the heterochronic process that has operated most frequently in North American taxa is not a retardation, but an acceleration. I also suggest that sexual dimorphism in plumage, and late plumage maturation in males, may arise as a secondary result of selection for neoteny in females with a correlated response in males, and not necessarily, as traditionally thought, as a result of selection for bright plumages in males.
The evolution of queen‐rearing nepotism in social Hymenoptera: Effects of discrimination costs in swarming species
Authors: Ratnieks Francis L. W. , Reeve Hudson Kern 
Published: December 2004

AbstractPolyandry by social hymenopteran queens leads to a potential worker reproductive strategy of rearing full‐sister queens in preference to half‐sister queens. If there is no cost to discrimination, discriminatory queen rearing will be the ESS. However, if discrimination has a cost this conclusion is weakened. This study examines the effect of a “worker efficiency cost” (i.e. discriminatory, nepotistic workers are less effective than non‐nepotistic workers in working to increase total colony reproductive output) on the invasion of rare “nepotist” and “non‐nepotist” alleles in a population in which the other allele is near fixation. Efficiency costs are considered of special relevance to species with swarm founded colonies (e.g., army ants, honey bees).Two analyses are presented: 1) A general model exploring the effects of efficiency costs, the queen‐rearing‐biasing ability of nepotists, and queen mating frequency on invasion of nepotists and non‐nepotists; 2) a discriminatory removal model, in which the actual amount of biasing is dependent on recognition abilities and the discriminatory intensity of nepotists, queen mating frequency, and whether or not removed immature queens are replaced.The results of the removal model indicate that when queen mating frequency is close to one (i.e., because of double mating with unequal sperm use or mixed double and single mating) non‐nepotist is likely to be the ESS. At a higher mating frequency nepotist will become the ESS. At even higher mating frequencies, non‐nepotist may reinvade. This latter conclusion is robust across all models. In particular, non‐nepotists may reinvade at the high mating frequencies found in the honey bee (10–20) if their work efficiency is only a few percent higher than nepotists (the exact amount depends on recognition errors and the intensity of discrimination), resulting in a genetic polymorphism of both nepotists and non‐nepotists. Results of a recent study of patriline discrimination in honey bees (Page et al., 1989) are consistent with such a polymorphism.
Homology and hierarchies: Problems solved and unresolved
Authors: Roth V. Louise 
Published: December 2004

AbstractHomology as a topic in phylogenetic analysis has to do with what is conserved in evolution. The problem of homology in systematics — to find homologues, and in so doing, to identify taxa — is distinct from the problem of identifying what kinds of features tend to be conserved, how and why. The two sets of issues are fundamentally interdependent at the point that one selects the appropriate taxonomic units, identifies the characters one wishes to study, or decides what constitutes a single character.Homology as a phenomenon is a manifestation of replication and of continuity of biological information. Replication occurs at many levels in the biological hierarchy: from the DNA replication that accompanies cell replication, to the replication of gross phenotypic characteristics within individual organisms that results in iterative homologues, to the replication of individuals to form a population that persists (in replication through successive generations) in evolutionary time. In replication, biological information may persist unchanged, or it may be disrupted or transformed. Different patterns of change may be expressed at different levels of the biological hierarchy. Here a concept developed in arguments on levels of selection becomes useful: change at one level of the hierarchy — e.g., genes or gross phenotype — may be screened off from changes at other levels. Understanding the manner in which phenotypic features develop or are replicated, the mechanisms of screening off, and the evolutionary origin and transformation of these mechanisms is a major challenge for understanding the biological basis of homology.The recognition or coding of characters for a phylogenetic analysis calls for decisions on what level of description and how complex a unit character is to be recognized. Here an additional point of comparison within the biological hierarchy — the relationship between organisms and taxa — becomes important. We use characters of organisms to trace phylogenies of taxa; yet because traits can arise and subsequently become fixed in different segments of a population linage, phylogenies of organismal characters can conflict with the phylogeny of the taxa that compairse them.For these reasons, a full understanding of evolutionary changes undergone in lineages will require us to combine phylogenetic analyses with analyses of development, studies of developmental and population genetics, and comparisons of gross phenotype.
Survivorship and fecundity of the radiate and non‐radiate morphs of Groundsel, Senecio vulgaris L., raised in pure stand and mixture
Authors: Abbott Richard J. , Horrill J. Christopher 
Published: December 2004

AbstractBritish populations of Senecio vulgaris frequently contain two common capitulum morphs (radiate and non‐radiate) and one rare intermediate morph. The radiate morph shows a higher maternal rate of intermorph outcrossing than the non‐radiate morph and due to the ‘cost of outcrossing’ should decline in frequency, ultimately to be lost from a population. To determine whether the radiate morph exhibits some inherent advantage in fitness to offset the ‘cost of outcrossing’, a comparison was made of the survivorship and fecundity of the radiate and non‐radiate morphs raised in pure stands and 1 : 1 mixture at three planting dates (autumn 1983, and spring and autumn 1984). Plants in stands established in spring 1984 were harvested in late August 1984, while plants in stands established in autumn overwintered before being harvested the following summer. In spring planted stands, the two morphs exhibited equivalent survivorships, while the fecundity of the non‐radiate morph tended to be greater than the radiate morph. In autumn planted stands, survivorship and Net Reproductive Output (survivorship × fecundity) of the non‐radiate morph was greater than that of the radiate morph in mixture, and also in pure stands established in 1983. In no instance was the Net Reproductive Output of either morph significantly greater in mixture than in pure stand. Density had a contrasting effect on morph survivorship and fecundity in the spring and autumn 1984 planted stands. Whereas, in spring stands, fecundity was subject to compensating density dependent regulation while survivorship was density independent, the opposite trend was observed in autumn planted stands. It is concluded that under the conditions of the experiments, the radiate morph exhibited no fitness advantage which might offset the inherent disadvantage it suffers in natural polymorphic populations due to the ‘cost of outcrossing’.
A comparison of methods to partition selection acting via components of fitness: Do larger male bullfrogs have greater hatching success?
Authors: Koenig Walter D. , Albano Stephen S. , Dickinson Janis L. 
Published: December 2004

AbstractWe contrast three methods for measuring selection at sequential fitness components (here called the additive, changing variance, and independent methods). The independent method (Koenig and Albano, 1987; Conner, 1988) describes the relationship between a phenotypic character and one fitness component independent of other components. This method is appropriate when the question is whether or not a character has fitness consequences independent of selection at other stages. The additive (Arnold and Wade, 1984a) and changing variance (Kalisz, 1986; Koenig and Albano, 1987) methods measure selection via one component of fitness, taking into consideration constraints imposed by selection via earlier components in the sequence. These methods therefore more accurately track selection over a sequence of fitness components. Of these latter two methods, the changing variance method yields erratic results in simulation studies and is not recommended in its unmodified form. The additive method (equivalent to the changing variance method weighted as described in Wade and Kalisz [1989]) explicitly partitions selection into additive components and is useful for measuring selection taking into account the constraints imposed by selection acting via prior fitness components.The methods often yield very different estimates of the relative degree to which the mean of a character is changed by selection acting via a particular component of fitness (the “strength” of selection). However, neither the additive nor independent method is inherently superior to the other; rather, these measures are complementary.
Genetic differentiation and habitat partition of Robertsonian house mouse populations (Mus musculus domesticus) of Tunisia
Authors: Said Khaled , Britton‐Davidian Janice 
Published: December 2004

AbstractThe karyological analysis of Tunisian populations of house mice revealed the existence of a Robertsonian (Rb) chromosomal race carrying nine pairs of metacentric chromosomes in central Tunisia.Divergence estimates showed that they are genetically differentiated from local all‐acrocentric populations and have a reduced level of genic variability. The Rb populations are restricted to urban habitats, whereas all‐acrocentric populations occur in rural areas. Contact zones between these two types of habitat yield chromosomally polymorphic populations. Analysis of gene flow indicates that it is reduced and limited to populations bordering the contact areas.The reduced genic variability and patchy distribution exhibited by the Tunisian Rb mice do not agree with results from previous studies of the European Rb populations. Two hypotheses are presented to account for this discrepancy based on local differentiation versus introduction of the Tunisian Rb race.
Populational interactions among underdominant chromosome rearrangements help them to persist in small demes
Authors: Spirito Franco , Rossi Carla , Rizzoni Marco 
Published: December 2004

AbstractPopulational interactions among unlinked chromosomal rearrangements with partial heterozygote sterility and multiplicative fitness were studied to verify whether they help such rearrangements to persist in small populations, in spite of a considerable migration rate with a large population. A deterministic island‐continent model was studied by exact recurrence relations connecting gametic frequencies in successive generations.The increase in the number of chromosomal rearrangements with the same sterility rate (s) causes an increase in the critical value of the migration rate (mc) over which the chromosomal rearrangements are eliminated from the small population, mainly for medium s values (0.2 ≤ s ≤ 0.5) (“reciprocal stabilization” of the chromosomal rearrangements).A comparison was made between the velocities of the fixation of a few rearrangements with high heterozygote sterility (low n/high s) and that of many rearrangements with low heterozygote sterility (high n/low s), to reach a given level of populational stability of the rearranged karyotype measured by mc. The former process was shown to be more rapid in small demes, the latter in large ones. However, the increase in the number of unlinked chromosomal rearrangements is more efficient in reducing the neutral gene flow than in increasing the populational stability of the rearranged karyotype.
Within‐island microgeographic variation in the colour pattern of the skink, Chalcides sexlineatus: Pattern and cause
Authors: Brown Richard P. , Thorpe Roger S. 
Published: December 2004

AbstractThe colour pattern of the Gran Canarian skink is described with eight independent colour pattern characters. Significant geographic variation occurs in each character. There are generally high levels of congruence between the patterns of geographic variation in each character although some differences exist. In canonical variate analyses, the first canonical variate expresses most of the among‐locality variation in colour pattern, indicating a largely unidimensional pattern. Patterns of geographic variation in the colour pattern are portrayed by contouring. This reveals north‐east/south‐west clines for seven of the individual characters and the generalized pattern (CV1). Four causal hypotheses were erected which predicted four different unidimensional patterns of geographic variation. Mantel tests and partial correlation analyses were used to compare the observed patterns of microgeographic variation with the four hypothesized patterns. This method suggests differential selection occurring between ecotones as the cause of the microgeographic variation. Microgeographic variation in some aspects of the colour pattern can be explained by selection for different anti‐predator strategies in the hot, arid southern areas vs the cooler, lusher northern areas.
A biomechanical perspective on the use of forelimb length as a measure of sexual selection in frogs
Authors: Emerson Sharon B. 
Published: December 2004

AbstractDifferences in forelimb length between male and female frogs and between amplexing and non‐amplexing males have been interpreted to be the results of sexual selection on forelimb length. The causal feature of the forelimb that has been posited to cause such selection is the observation that non‐amplexing males attempt to disrupt breeding by prying amplexing males from females. A biomechanical model of forelimb function suggests that total length per se may not be the most appropriate measure to use. There are more functionally significant aspects of forelimb morphology, such as lever arm lengths, that should influence amplexing ability and may make measures of overall forelimb length misleading. This example highlights the relevance of functional analysis to current questions in evolutionary biology that rely on postulated roles for morphological structures under selection.
The selective advantage of reaction norms for environmental tolerance
Authors: Gabriel Wilfried , Lynch Michael 
Published: December 2004

AbstractA tolerance curve defines the dependence of a genotype's fitness on the state of an environmental gradient. It can be characterized by a mode (the genotype's optimal environment) and a width (the breadth of adaptation). It seems possible that one or both of these characters can be modified in an adaptive manner, at least partially, during development. Thus, we extend the theory of environmental tolerance to include reaction norms for the mode and the width of the tolerance curve. We demonstrate that the selective value of such reaction norms increases with increasing spatial heterogeneity and between‐generation temporal variation in the environment and with decreasing within‐generation temporal variation. Assuming that the maintenance of a high breadth of adaptation is costly, reaction, norms are shown to induce correlated selection for a reduction in this character. Nevertheless, regardless of the magnitude of the reaction norm, there is a nearly one to one relationship between the optimal breadth of adaptation and the within‐generation temporal variation perceived by the organism. This suggests that empirical estimates of the breadth of adaptation may provide a useful index of this type of environmental variation from the organism's point of view.
Mitochondrial gene frequencies in Africanized honeybees (Apis mellifera L.): Theoretical model and empirical evidence
Authors: Moritz Robin F. A. , Meusel Michael S. 
Published: December 2004

AbstractA population genetical model is used to investigate the effects of queen and drone fitness and swarming ability on nuclear and mitochondrial (mt) DNA variation in honeybees. The analysis of both types of DNA is particularly useful for a genetic study of the Africanized bee problem in the Americas. Both an analytical model and a Monte Carlo simulation show that even if mtDNA proves to be selectively neutral, Africanized mitotypes are expected at high frequencies because of the more frequent swarming of Africanized honeybees. Since the fitness of Africanized drones is higher than that of European drones, European and African mitotypes are expected to be polymorphic and consequently unreliable as diagnostic tools to discriminate between the two types. Samples of Africanized honeybees in Brazil reveal high mtDNA polymorphisms as predicted by the theoretical models.
Gene flow rates in Yugoslavian populations of the smooth newt Triturus vulgaris
Authors: González‐Candelas Fernando , Crnobrnja Jelka , Kalezic Milos L. , Moya Andrés 
Published: December 2004

AbstractAllozymic variation in 22 loci in several Yugoslavian populations of four subspecies of the smooth newt Triturus vulgaris, has been analyzed. The frequency of private alleles and the coefficient of genetic differentiation, FST, give very different indirect estimates of the effective number of migrants per generation, Nm. However, such Nm estimates, in most cases higher than 1, imply that gene flow between populations is large enough as to prevent differentiation by random drift. In the case of T.v. vulgaris, of which sixteen populations amply distributed through Yugoslavia were sampled, there is evidence that frequent extinction and recolonization processes might be responsible for the observed genetic structure. This conclusion has been reached after testing the correlation between genetic, environmental and geographical matrices.
Sexual selection in the monogamous barn swallow (Hirundo rustica). II. Mechanisms of sexual selection
Authors: Møller Anders Pape 
Published: December 2004

AbstractMechanisms of sexual selection in the monogamous, sexually dimorphic barn swallow (Hirundo rustica) were studied during a seven‐year period. First, the sex ratio of reproducing adults was male‐biased, and mated males had significantly longer tail ornaments than unmated males. Secondly, some of the unmated individuals later committed infanticide and became mated with the mother of the killed brood. Fathers of killed broods had significantly shorter tails than other males, and there was a tendency for infanticidal males to have longer tail ornaments than other unmated males. Thirdly, long‐tailed male barn swallows were more successful in acquiring extra‐pair copulations than other males, and females involved in extra‐pair copulations, as compared to females not involved in such copulations, had mates with shorter tail ornaments. Fourthly, male barn swallows having long tails as compared to short‐tailed males acquired mates in better body condition. Females mated to long‐tailed males reproduced earlier, laid more eggs and were more likely to have two clutches than were females mated to short‐tailed males. Finally, females mated to long‐tailed males put more effort into reproduction than did other females, as evidenced by their relatively larger contribution to feeding of offspring. Thus, at least five different components of sexual selection affected male reproductive success. Selection arising from differential success during extra‐pair copulations, differential reproductive success and differential male reproductive effort thus accounted for most of the selection on tail ornaments in male barn swallows.
A narrow hybrid zone between two crayfish species from a Mexican cave
Authors: Cesaroni Donatella , Allegrucci Giuliana , Sbordoni Valerio 
Published: December 2004

AbstractIn Northern Chiapas (Mexico), two newly discovered species of Procambarus crayfish inhabit a subterranean stream. These species can be morphologically distinguished only by comparing extreme phenotypes (dark, thick‐eyed, surface dwelling‐like individuals vs light, elongated, microphtalmic, cave dwelling‐like individuals). Individuals with intermediate phenotypes co‐occur with those exhibiting extreme phenotypes.Crayfish were assayed electrophoretically and individual patterns at 23 gene loci were obtained. Unusually high levels of heterozygosity in both species and a clear discrimination between the two gene pools were revealed. The relationships between individuals were investigated by means of multivariate analysis on individual multilocus genotype profiles. Results showed the occurrence of individuals genetically intermediate between the two major clusters, which shared allozymic variants with both species. Due to the occurrence of alternative alleles in the two gene pools, we could quantify patterns of introgression, which revealed asymmetric gene flow between the two species. Moreover, differential levels of introgression in subsamples within the surface‐like species were found: most introgressed individuals came from the inner section of the cave, where the two species were greatly mixed. These results are also discussed in reference to the morphometric results from a companion paper.A possible evolutionary pathway, leading to the situation in this cave, and possibly in neighbouring cave systems, is outlined. The hypothesis of a past history of allopatric divergence from a common ancestor and a subsequent secondary contact between these two Procambarus species is supported by geological studies. Crayfish sympatry and competitive exclusion are also discussed.
Homology and logical fallacy
Authors: Rieppel Olivier 
Published: December 2004

AbstractThe meaning of homology, is analyzed in a phylogenetic context. The notion of homology is unequivocal only if tied to recency of common ancestry, i.e. to the concept of monophyly. Processual analysis of the biological causes of similarity cannot provide guidance in the search for relations of homology. Instead, it is the reconstruction of the taxic hierarchy based on homology and congruence which provides guidance in the search for underlying causes of similarity. Pattern reconstruction is shown to have logical precedence over process explanations.
Application of the biogenetic law to behavioral ontogeny: a test using nest architecture in paper wasps
Authors: Wenzel John W. 
Published: December 2004

AbstractGeneral principles derived from studies of morphological ontogeny are useful in ethology. Behavioral ontogeny may be interpreted from an holistic view in which a series of behaviors is treated as an ontogeny toward a larger, complex, behavioral product. If the component behaviors are defined broadly, many taxa may be compared to find general principles that are not evident when behaviors are dissected to their smallest recognizable units. Flow charts can illustrate such general ontogenetic sequences in a manner that shows what sorts of modifications have evolved from the general pattern. Certain changes may illustrate forms of ontogenetic evolution that are well known for morphological development, such as addition or embellishment of terminal ontogenetic steps, or compression of ontogeny by acceleration or deletion of early steps. The major modifications in nest construction behavior of 28 genera of paper wasps are presented to test the predictions of the biogenetic rule with respect to character polarity. Cladistic analyses of separate morphological and behavioral data sets show that polarity is accurately inferred with respect to the five major patterns of nest construction in paper wasps.