Home About us Contact
|
Home About us Contact | ||
|
|
||
Morphological Traits (morphological + trait)
Selected AbstractsEPISTASIS AND DOMINANCE: EVIDENCE FOR DIFFERENTIAL EFFECTS IN LIFE-HISTORY VERSUS MORPHOLOGICAL TRAITSEVOLUTION, Issue 10 2006Derek A. Roff Abstract Dominance and epistatic effects are predicted to be larger in life-history than in morphological traits. We test these predictions using published results from line cross analyses. We find that dominance is found in more than 95% of traits, regardless of the type of trait, but that the magnitude of the effect in relation to the additive effect is much greater in life-history than in morphological traits. Epistatic effects were detected more often in life-history than in morphological traits (79% and 67%, respectively). We also test for a difference in the magnitude of the effects by comparing the ratio of the nonadditive components separately to the additive component. For both dominance and epistatic components, the ratio of the nonadditive component to additive effects in life-history traits is approximately twice as large as that for morphological traits. [source] Morphological Traits above the Flag Leaf Node as Indicators of Drought Susceptibility Index in Durum WheatJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 2 2007D. Villegas Abstract Selection criteria for drought tolerance would be helpful tools for wheat breeding programmes. To assess the usefulness of some morphological traits above the flag leaf node as indicators of yield and the susceptibility index (SI) of Fischer and Maurer, 10 durum wheat genotypes were used in experiments conducted under two water regimes at two latitudes in Spain during 3 years. Morphological traits were measured at anthesis, and yield, yield components and quality traits were evaluated at ripening. Principal components analysis showed associations between morphological traits and yield, yield components and quality, most of them caused by differences between environments. Peduncle weight, spike weight and length and awn length were significantly related to SI within environments. Spike and peduncle weight were the traits more related to yield and SI in all the experiments together and in the rainfed sites, while in the irrigated sites spike length was better. The spike weight and length were negatively associated with SI, while peduncle weight was positively associated to SI. Genotype means across all experiments were associated with SI values. These morphological traits could be selection criteria in breeding programmes to obtain varieties with good yield stability. The genetic variability found suggests opportunity for selection. [source] Sexually antagonistic coevolution in insects is associated with only limited morphological diversityJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 3 2006W. Eberhard Abstract Morphological traits involved in male,female sexual interactions, such as male genitalia, often show rapid divergent evolution. This widespread evolutionary pattern could result from sustained sexually antagonistic coevolution, or from other types of selection such as female choice or selection for species isolation. I reviewed the extensive but under-utilized taxonomic literature on a selected subset of insects, in which male,female conflict has apparently resulted in antagonistic coevolution in males and females. I checked the sexual morphology of groups comprising 500,1000 species in six orders for three evolutionary trends predicted by the sexually antagonistic coevolution hypothesis: males with species-specific differences and elaborate morphology in structures that grasp or perforate females in sexual contexts; corresponding female structures with apparently coevolved species-specific morphology; and potentially defensive designs of female morphology. The expectation was that the predictions were especially likely to be fulfilled in these groups. A largely qualitative overview revealed several surprising patterns: sexually antagonistic coevolution is associated with frequent, relatively weak species-specific differences in males, but male designs are usually relatively simple and conservative (in contrast to the diverse and elaborate designs common in male structures specialized to contact and hold females in other species, and also in weapons such as horns and pincers used in intra-specific battles); coevolutionary divergence of females is not common; and defensive female divergence is very uncommon. No cases were found of female defensive devices that can be facultatively deployed. Coevolutionary morphological races may have occurred between males and females of some bugs with traumatic insemination, but apparently as a result of female attempts to control fertilization, rather than to reduce the physical damage and infections resulting from insertion of the male's hypodermic genitalia. In sum, the sexually antagonistic coevolution that probably occurs in these groups has generally not resulted in rapid, sustained evolutionary divergence in male and female external sexual morphology. Several limitations of this study, and directions for further analyses are discussed. [source] Development of molecular markers to assess the level of introgression of Populus tremula into P. alba natural populationsPLANT BREEDING, Issue 4 2004T. Fossati Abstract Morphological traits traditionally adopted to discriminate between Populus alba L. and P. tremula L. have frequently led to misclassifi-cation of their spontaneous hybrid P. × canescens Sm. Moreover, they may not be of any help in cases of spontaneous backcross phenomena. These limitations can be overcome by molecular markers, which are not environmentally influenced nor subjectively assessed. In this study, the effectiveness of amplified fragment length polymorphism (AFLP) and simple sequence repeat (SSR) markers in species and hybrid discrimination was evaluated by analysing a set of reference samples of P. alba, P. tremula and P. × canescens. Species-specific and species-indicative AFLPs, as well as diagnostic SSR alleles, were recorded in both P. alba and P. tremula reference samples. The results allowed a clear distinction between the two poplar species and their hybrid. Using these diagnostic markers, a natural population of P. alba trees sampled along the Ticino river basin in northern Italy was analysed, and P. × canescens individuals, intermingled with P. alba trees, were detected. [source] Evaluation of pollination syndromes in Antillean Gesneriaceae: evidence for bat, hummingbird and generalized flowersJOURNAL OF ECOLOGY, Issue 2 2009Silvana Martén-Rodríguez Summary 1Current views about the predominance of generalization of pollination systems have stimulated controversy concerning the validity of pollination syndromes. In order to assess the extent to which floral characters reflect selection by the most important pollinators we evaluated pollination syndromes in a florally diverse plant group, the tribe Gesnerieae, a monophyletic plant radiation from the Antillean islands. 2The study species include representatives of three groups of floral phenotypes, two of which chiefly correspond to ornithophilous and chiropterophilous syndromes. The third group includes subcampanulate flowers (characterized by a corolla constriction above the nectar chamber) with combinations of traits not fitting classic pollination syndromes. 3Pollination systems were characterized for 19 Gesnerieae species in five Antillean islands between 2003 and 2007 and supplemented with observations of four Gesneriaceae species from Costa Rica. Pollinator visitation and frequency of contact with anthers or stigmas were used to calculate an index of pollinator importance. Eleven floral traits including morphology, phenology and rewards were used to assess clustering patterns in phenotype space. 4Multidimensional scaling analysis of floral traits resulted in two clusters comprising: (i) tubular, red to yellow-flowered species with diurnal anthesis, (ii) bell-shaped-flowered species; two groups of floral phenotypes were evident within the latter cluster, campanulate nocturnal and subcampanulate flowers. Correlations between pollinator importance values and floral axes revealed strong associations with the expected pollinators, hummingbirds for tubular flowers, and bats for campanulate flowers; subcampanulate-flowered species had generalized pollination systems including bats, hummingbirds and insects. Discriminant analysis of the multivariate set of floral traits correctly classified 19 out of 23 species into the predicted pollination categories. 5Synthesis. This study provides support for classic hummingbird and bat pollination syndromes, demonstrating the importance of pollinator-mediated selection in the floral diversification of Antillean Gesnerieae. However, there was evidence for generalized pollination systems in species characterized by a unique morphological trait (corolla constriction), but with variable combinations of other floral traits. These findings suggests that floral phenotypes might also evolve under selection by various functional groups of pollinators, and underscores the importance of considering the presence and effectiveness of all floral visitors in pollination studies. [source] The genetic basis of early-life morphological traits and their relation to alternative male reproductive tactics in Atlantic salmonJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 4 2010D. J. PáEZ Abstract Although heritability estimates for traits potentially under natural selection are increasingly being reported, their estimation remains a challenge if we are to understand the patterns of adaptive phenotypic change in nature. Given the potentially important role of selection on the early life phenotype, and thereby on future life history events in many fish species, we conducted a common garden experiment, using the Atlantic salmon (Salmo salar L.), with two major aims. The first objective is to determine how the site of origin, the paternal sexual tactic and additive genetic effects influence phenotypic variation of several morphological traits at hatching and emergence. The second aim is to test whether a link exists between phenotypic characteristics early in life and the incidence of male alternative tactics later in life. We found no evidence of a site or paternal effect on any morphological trait at hatching or emergence, suggesting that the spatial phenotypic differences observed in the natural river system from which these fish originated are mainly environmentally driven. However, we do find significant heritabilities and maternal effects for several traits, including body size. No direct evidence was found correlating the incidence of precocious maturation with early life characteristics. We suggest that under good growing conditions, body size and other traits at early developmental stages are not reliable cues for the surpassing of the threshold values associated with male sexual development. [source] GIS-based niche models identify environmental correlates sustaining a contact zone between three species of European vipersDIVERSITY AND DISTRIBUTIONS, Issue 3 2008F. Martínez-Freiría ABSTRACT The current range of European vipers is mostly parapatric but local-scale allopatric distribution is common and few cases of sympatry are known. In the High Course of Ebro River, northern Spain, there is a contact zone between Vipera aspis, V. latastei, and V. seoanei. Sympatry was detected between aspis and latastei and also specimens with intermediate morphological traits. Presence-data at a local scale (1 × 1 km) and ecological niche-based models manipulated in a GIS were used to (1) identify how environmental factors correlate with the distribution of the three vipers and with the location of the sympatry area, and (2) identify potential areas for viper occurrence and sympatry. Ensemble for casting with 10 Maximum Entropy models identified a mixture of topographical (altitude, slope), climatic (precipitation, evapotranspiration, and minimum and maximum temperature), and habitat factors (land cover) as predictors for viper occurrence. Similar predicted probabilities according to the variation of some environmental factors (indicating probable sympatry) were observed only for aspis-latastei and aspis-seoanei. In fact, areas of probable occurrence of vipers were generally allopatric but probable sympatry between vipers was identified for aspis-latastei in 76 UTM 1 × 1 km squares, for aspis-seoanei in 23 squares, and latastei-seoanei in two squares. Environmental factors correlate with the location of this contact zone by shaping the species range: some enhance spatial exclusion and constrain distribution to spatially non-overlapping ranges, while others allow contact between species. The distribution in the contact zone apparently results from the balance between the pressures exerted by the different environmental factors and in the sympatry area probably by interspecific competition. Further ecological and genetical data are needed to evaluate the dynamics of the probable hybrid zone. GIS and niche-modelling tools proved to be powerful tools to identify environmental factors sustaining the location of contact zones. [source] Spatial and temporal variation in the morphology (and thus, predicted impact) of an invasive species in AustraliaECOGRAPHY, Issue 2 2006Ben L. Phillips The impact of an invasive species is unlikely to be uniform in space or time, due to variation in key traits of the invader (e.g. morphology, physiology, behaviour) as well as in resilience of the local ecosystem. The weak phylogeographic structure typical of an invasive population suggests that much of the variation in an invading taxon is likely to be generated by the environment and recent colonisation history. Here we describe effects of the environment and colonisation history on key morphological traits of an invader (the cane toad Bufo marinus). These "key traits" (body size and relative toxicity) mediate the impact of toads on Australian native predators, which often die as a consequence of ingesting a fatal dose of toad toxin. Measurements of museum specimens collected over >60 yr from a wide area show that seasonal variation in toad body size (due to seasonal recruitment) effectively swamps much of the spatial variance in this trait. However, relative toxicity of toads showed strong spatial variation and little seasonal variation. Thus, the risk to a native predator ingesting a toad will vary on both spatial and temporal scales. For native predators capable of eating a wide range of toad sizes (e.g. quolls, varanid lizards), seasonal variation in overall toad size will be the most significant predictor of risk. In contrast, gape-limited predators restricted to a specific range of toad sizes (such as snakes) will be most strongly affected by the relative toxicity of toads. Gape-limited predators will thus experience strong spatial variation in risk from toad consumption. [source] Correlated morphological and colour differences among females of the damselfly Ischnura elegansECOLOGICAL ENTOMOLOGY, Issue 3 2009JESSICA K. ABBOTT Abstract 1.,The female-limited colour polymorphic damselfly Ischnura elegans has proven to be an interesting study organism both as an example of female sexual polymorphism, and in the context of the evolution of colour polymorphism, as a model of speciation processes. 2.,Previous research suggests the existence of correlations between colour morph and other phenotypic traits, and the different female morphs in I. elegans may be pursuing alternative phenotypically integrated strategies. However, previous research on morphological differences in southern Swedish individuals of this species was only carried out on laboratory-raised offspring from a single population, leaving open the question of how widespread such differences are. 3.,The present study therefore analysed multi-generational data from 12 populations, investigating morphological differences between the female morphs in the field, differences in the pattern of phenotypic integration between morphs, and quantified selection on morphological traits. 4.,It was found that consistent morphological differences indeed existed between the morphs across populations, confirming that the previously observed differences were not simply a laboratory artefact. It was also found, somewhat surprisingly, that despite the existence of sexual dimorphism in body size and shape, patterns of phenotypic integration differed most between the morphs and not between the sexes. Finally, linear selection gradients showed that female morphology affected fecundity differently between the morphs. 5.,We discuss the relevance of these results to the male mimicry hypothesis and to the existence of potential ecological differences between the morphs. [source] Environmental features influencing Carabid beetle (Coleoptera) assemblages along a recently deglaciated area in the Alpine regionECOLOGICAL ENTOMOLOGY, Issue 6 2007MAURO GOBBI Abstract 1.,The spatio-temporal approach was used to evaluate the environmental features influencing carabid beetle assemblages along a chronosequence of an Italian Alpine glacier foreland. The influence of environmental variables on species richness, morphology (wing and body length), and distribution along the chronosequence was tested. 2.,Species richness was found to be a poor indicator of habitat due to weak influences by environmental variables. It seems that the neighbouring habitats of a glacier foreland are not able to determine significant changes in carabid species richness. 3.,Instead it appears that history (age since deglaciation) and habitat architecture of a glacier foreland are strongly correlated to species adaptive morphological traits, such as wing morphology and body length. Assemblages characterised by species with reduced wing size are linked to the older stages of the chronosequence, where habitat is more structured. Assemblages characterised by the largest species are linked to the younger sites near the glacier. These morphological differentiations are explained in detail. 4.,Habitat age can therefore be considered the main force determining assemblage composition. On the basis of the relationship between morphological traits and environmental variables, it seems likely that age since deglaciation is the main variable influencing habitat structure (primary effect) on the Forni foreland. The strong relationship between carabid assemblages and habitat type indicates that site age has but a secondary effect on carabid assemblages. This may be utilised to interpret potential changes in assemblages linked to future glacier retreat. [source] Inter-sexual combat and resource allocation into body parts in the spider, Stegodyphus lineatusECOLOGICAL ENTOMOLOGY, Issue 6 2006ALEXEI A. MAKLAKOV Abstract 1.,Sexual conflict, which results from the divergence of genetic interests between males and females, is predicted to affect multiple behavioural, physiological, and morphological traits. 2.,Sexual conflict over mating may interact with population density to produce predictable changes in resource allocation into inter-sexual armament. 3.,In the spider Stegodyphus lineatus, males fight with females over re-mating. The outcome of the fight is influenced by the cephalothorax size of the contestants. The investment in armament , the cephalothorax, may be traded-off against investment in abdomen, which is a trait that affects survival and fecundity. Pay-offs may depend on population density. Both sexes are expected to adjust resource allocation into different body parts accordingly. 4.,Males had increased cephalothorax/body size ratio in low densities where probability of finding another receptive female is low and females had increased cephalothorax/body size ratio in high densities where cumulative costs of multiple mating are high. 5.,The results support the theoretical conjecture that population density affects resource allocation into inter-sexual armament and call for further research on the interaction between sexual selection and population density. [source] Does morphological variation between young-of-the-year perch from two Swedish lakes depend on genetic differences?ECOLOGY OF FRESHWATER FISH, Issue 2 2010M. Heynen Heynen M, Hellström G, Magnhagen C, Borcherding J. Does morphological variation between young-of-the-year perch from two Swedish lakes depend on genetic differences? Ecology of Freshwater Fish 2010: 19: 163,169. © 2009 John Wiley & Sons A/S Abstract,,, Different local environmental conditions have often been found to generate phenotypic diversity. In the present study we examined morphological differences between young-of-the-year perch from two lake populations with differences in size-specific predation risk. A common garden setup was used to examine the genetic and environmental components of the morphological variation. We found differences in head and jaw length and slight differences in body depth between the wild young-of-the-year perch from Lake Ängersjön and Lake Fisksjön. The differences found between the wild fish from the two lakes were not maintained under common garden rearing. The observed morphological divergence between the wild young-of-the-year perch from Lake Ängersjön and Lake Fisksjön seems to stem mainly from a plastic response to different environmental conditions in the two lakes. It is clear that the morphological traits are not influenced by direct reaction to the size-specific risk of cannibalism, but probably stem from a combination of different environment characteristics, including resource and habitat use, and the density of other piscivores, such as pike. [source] Female Mate Choice, Calling Song and Genetic Variance in the Cricket, Gryllodes sigillatusETHOLOGY, Issue 3 2008Jocelyn Champagnon Female preferences for song patterns of males of Gryllodes sigillatus and genetic variance of morphological traits correlated with them were analyzed. Females preferred short pulses associated with large males. The males' thorax width, wing length and femur III length showed stronger relationship with the song pulse duration, whereas the relationship between pulse duration and wing width was not significant. Interestingly, this last trait was the only one that showed significant levels of genetic variance. Perhaps these results could be explained by the evolutionary response to sexual selection. Sexual selection could deplete the genetic variance in the male traits related to male-mating success. [source] PURGING THE GENOME WITH SEXUAL SELECTION: REDUCING MUTATION LOAD THROUGH SELECTION ON MALESEVOLUTION, Issue 3 2009Michael C. Whitlock Healthy males are likely to have higher mating success than unhealthy males because of differential expression of condition-dependent traits such as mate searching intensity, fighting ability, display vigor, and some types of exaggerated morphological characters. We therefore expect that most new mutations that are deleterious for overall fitness may also be deleterious for male mating success. From this perspective, sexual selection is not limited to influencing those genes directly involved in exaggerated morphological traits but rather affects most, if not all, genes in the genome. If true, sexual selection can be an important force acting to reduce the frequency of deleterious mutations and, as a result, mutation load. We review the literature and find various forms of indirect evidence that sexual selection helps to eliminate deleterious mutations. However, direct evidence is scant, and there are almost no data available to address a key issue: is selection in males stronger than selection in females? In addition, the total effect of sexual selection on mutation load is complicated by possible increases in mutation rate that may be attributable to sexual selection. Finally, sexual selection affects population fitness not only through mutation load but also through sexual conflict, making it difficult to empirically measure how sexual selection affects load. Several lines of enquiry are suggested to better fill large gaps in our understanding of sexual selection and its effect on genetic load. [source] THE LOCI OF EVOLUTION: HOW PREDICTABLE IS GENETIC EVOLUTION?EVOLUTION, Issue 9 2008David L. Stern Is genetic evolution predictable? Evolutionary developmental biologists have argued that, at least for morphological traits, the answer is a resounding yes. Most mutations causing morphological variation are expected to reside in the cis -regulatory, rather than the coding, regions of developmental genes. This "cis -regulatory hypothesis" has recently come under attack. In this review, we first describe and critique the arguments that have been proposed in support of the cis -regulatory hypothesis. We then test the empirical support for the cis -regulatory hypothesis with a comprehensive survey of mutations responsible for phenotypic evolution in multicellular organisms. Cis -regulatory mutations currently represent approximately 22% of 331 identified genetic changes although the number of cis -regulatory changes published annually is rapidly increasing. Above the species level, cis -regulatory mutations altering morphology are more common than coding changes. Also, above the species level cis -regulatory mutations predominate for genes not involved in terminal differentiation. These patterns imply that the simple question "Do coding or cis -regulatory mutations cause more phenotypic evolution?" hides more interesting phenomena. Evolution in different kinds of populations and over different durations may result in selection of different kinds of mutations. Predicting the genetic basis of evolution requires a comprehensive synthesis of molecular developmental biology and population genetics. [source] EVOLUTIONARY DYNAMICS OF A SEXUAL ORNAMENT IN THE HOUSE SPARROW (PASSER DOMESTICUS): THE ROLE OF INDIRECT SELECTION WITHIN AND BETWEEN SEXESEVOLUTION, Issue 6 2008Henrik Jensen The relative contribution of sexual and natural selection to evolution of sexual ornaments has rarely been quantified under natural conditions. In this study we used a long-term dataset of house sparrows in which parents and offspring were matched genetically to estimate the within- and across-sex genetic basis for variation and covariation among morphological traits. By applying two-sex multivariate "animal models" to estimate genetic parameters, we estimated evolutionary changes in a male sexual ornament, badge size, from the contribution of direct and indirect selection on correlated traits within males and females, after accounting for overlapping generations and age-structure. Indirect natural selection on genetically correlated traits in males and females was the major force causing evolutionary change in the male ornament. Thus, natural selection on female morphology may cause indirect evolutionary changes in male ornaments. We observed however no directional phenotypic change in the ornament size of one-year-old males during the study period. On the other hand, changes were recorded in other morphological characters of both sexes. Our analyses of evolutionary dynamics in sexual characters require application of appropriate two-sex models to account for how selection on correlated traits in both sexes affects the evolutionary outcome of sexual selection. [source] A NEGATIVE RELATIONSHIP BETWEEN MUTATION PLEIOTROPY AND FITNESS EFFECT IN YEASTEVOLUTION, Issue 6 2007Tim F. Cooper It is generally thought that random mutations will, on average, reduce an organism's fitness because resulting phenotypic changes are likely to be maladaptive. This relationship leads to the prediction that mutations that alter more phenotypic traits, that is, are more pleiotropic, will impose larger fitness costs than mutations that affect fewer traits. Here we present a systems approach to test this expectation. Previous studies have independently estimated fitness and morphological effects of deleting all nonessential genes in Saccharomyces cerevisiae. Using datasets generated by these studies, we examined the relationship between the pleiotropic effect of each deletion mutation, measured as the number of morphological traits differing from the parental strain, and its effect on fitness. Pleiotropy explained ,18% of variation in fitness among the mutants even once we controlled for correlations between morphological traits. This relationship was robust to consideration of other explanatory factors, including the number of protein,protein interactions and the network position of the deleted genes. These results are consistent with pleiotropy having a direct role in affecting fitness. [source] LINEAGES WITH LONG DURATIONS ARE OLD AND MORPHOLOGICALLY AVERAGE: AN ANALYSIS USING MULTIPLE DATASETSEVOLUTION, Issue 4 2007Lee Hsiang Liow Lineage persistence is as central to biology as evolutionary change. Important questions regarding persistence include: why do some lineages outlive their relatives, neither becoming extinct nor evolving into separate lineages? Do these long-duration lineages have distinctive ecological or morphological traits that correlate with their geologic durations and potentially aid their survival? In this paper, I test the hypothesis that lineages (species and higher taxa) with longer geologic durations have morphologies that are more average than expected by chance alone. I evaluate this hypothesis for both individual lineages with longer durations and groups of lineages with longer durations, using more than 60 published datasets of animals with adequate fossil records. Analyses presented here show that groups of lineages with longer durations fall empirically into one of three theoretically possible scenarios, namely: (1) the morphology of groups of longer duration lineages is closer to the grand average of their inclusive group, that is, their relative morphological distance is smaller than expected by chance alone, when compared with rarified samples of their shorter duration relatives (a negative group morpho-duration distribution); (2) the relative morphological distance of groups of longer duration lineages is no different from rarified samples of their shorter duration relatives (a null group morpho-duration distribution); and (3) the relative morphological distance of groups of longer duration lineages is greater than expected when compared with rarified samples of their shorter duration relatives (a positive group morpho-duration distribution). Datasets exhibiting negative group morpho-duration distributions predominate. However, lineages with higher ranks in the Linnean hierarchy demonstrate positive morpho-duration distributions more frequently. The relative morphological distance of individual longer duration lineages is no different from that of rarified samples of their shorter duration relatives (a null individual morpho-duration distribution) for the majority of datasets studied. Contrary to the common idea that very persistent lineages are special or unique in some significant way, both the results from analyses of long-duration lineages as groups and individuals show that they are morphologically average. Persistent lineages often arise early in a group's history, even though there is no prior expectation for this tendency in datasets of extinct groups. The implications of these results for diversification histories and niche preemption are discussed. [source] EPISTASIS AND DOMINANCE: EVIDENCE FOR DIFFERENTIAL EFFECTS IN LIFE-HISTORY VERSUS MORPHOLOGICAL TRAITSEVOLUTION, Issue 10 2006Derek A. Roff Abstract Dominance and epistatic effects are predicted to be larger in life-history than in morphological traits. We test these predictions using published results from line cross analyses. We find that dominance is found in more than 95% of traits, regardless of the type of trait, but that the magnitude of the effect in relation to the additive effect is much greater in life-history than in morphological traits. Epistatic effects were detected more often in life-history than in morphological traits (79% and 67%, respectively). We also test for a difference in the magnitude of the effects by comparing the ratio of the nonadditive components separately to the additive component. For both dominance and epistatic components, the ratio of the nonadditive component to additive effects in life-history traits is approximately twice as large as that for morphological traits. [source] FROM MICRO- TO MACROEVOLUTION THROUGH QUANTITATIVE GENETIC VARIATION: POSITIVE EVIDENCE FROM FIELD CRICKETSEVOLUTION, Issue 10 2004Mattieu Bégin Abstract . -Quantitative genetics has been introduced to evolutionary biologists with the suggestion that microevolution could be directly linked to macroevolutionary patterns using, among other parameters, the additive genetic variance/ covariance matrix (G) which is a statistical representation of genetic constraints to evolution. However, little is known concerning the rate and pattern of evolution of G in nature, and it is uncertain whether the constraining effect of G is important over evolutionary time scales. To address these issues, seven species of field crickets from the genera Gryllus and Teleogryllus were reared in the laboratory, and quantitative genetic parameters for morphological traits were estimated from each of them using a nested full-sibling family design. We used three statistical approaches (T method, Flury hierarchy, and Mantel test) to compare G matrices or genetic correlation matrices in a phylogenetic framework. Results showed that G matrices were generally similar across species, with occasional differences between some species. We suggest that G has evolved at a low rate, a conclusion strengthened by the consideration that part of the observed across-species variation in G can be explained by the effect of a genotype by environment interaction. The observed pattern of G matrix variation between species could not be predicted by either morphological trait values or phylogeny. The constraint hypothesis was tested by comparing the multivariate orientation of the reconstructed ancestral G matrix to the orientation of the across-species divergence matrix (D matrix, based on mean trait values). The D matrix mainly revealed divergence in size and, to a much smaller extent, in a shape component related to the ovipositor length. This pattern of species divergence was found to be predictable from the ancestral G matrix in agreement with the expectation of the constraint hypothesis. Overall, these results suggest that the G matrix seems to have an influence on species divergence, and that macroevolution can be predicted, at least qualitatively, from quantitative genetic theory. Alternative explanations are discussed. [source] CONSTANCY OF THE G MATRIX IN ECOLOGICAL TIMEEVOLUTION, Issue 6 2004Mats BjÖrklund Abstract The constancy of the genetic variance-covariance matrix (G matrix) across environments and populations has been discussed and tested empirically over the years but no consensus has so far been reached. In this paper, I present a model in which morphological traits develop hierarchically, and individuals differ in their resource allocation and acquisition patterns. If the variance in resource acquisition is many times larger than the variance in resource allocation then strong genetic correlations are expected, and with almost isometric relations among traits. As the variation in resource acquisition decreases below a certain threshold, the correlations decrease overall and the relations among traits become a function of the allocation patterns, and in particular reflecting the basal division of allocation. A strong bottleneck can break a pattern of strong genetic correlation, but this effect diminishes rapidly with increasing bottleneck size. This model helps to understand why some populations change their genetic correlations in different environments, whereas others do not, since the key factor is the relation between the variances in resource acquisition and allocation. If a change in environment does not lead to a change in this ratio, no change can be expected, whereas if the ratio is changed substantially then major changes can be expected. This model can also help to understand the constancy of morphological patterns within larger taxa as a function of constancy in resource acquisition patterns over time and environments. When this pattern breaks, for example on islands, larger changes can be expected. [source] THE EVOLUTION OF SEXUAL SIZE DIMORPHISM IN THE HOUSE FINCH.EVOLUTION, Issue 6 2000Abstract Recent colonization of ecologically distinct areas in North America by the house finch (Carpodacus mexicanus) was accompanied by strong population divergence in sexual size dimorphism. Here we examined whether this divergence was produced by population differences in local selection pressures acting on each sex. In a long-term study of recently established populations in Alabama, Michigan, and Montana, we examined three selection episodes for each sex: selection for pairing success, overwinter survival, and within-season fecundity. Populations varied in intensity of these selection episodes, the contribution of each episode to the net selection, and in the targets of selection. Direction and intensity of selection strongly differed between sexes, and different selection episodes often favored opposite changes in morphological traits. In each population, current net selection for sexual dimorphism was highly concordant with observed sexual dimorphism,in each population, selection for dimorphism was the strongest on the most dimorphic traits. Strong directional selection on sexually dimorphic traits, and similar intensities of selection in both sexes, suggest that in each of the recently established populations, both males and females are far from their local fitness optimum, and that sexual dimorphism has arisen from adaptive responses in both sexes. Population differences in patterns of selection on dimorphism, combined with both low levels of ontogenetic integration in heritable sexually dimorphic traits and sexual dimorphism in growth patterns, may account for the close correspondence between dimorphism in selection and observed dimorphism in morphology across house finch populations. [source] SEXUAL DIMORPHISM IN RELATION TO CURRENT SELECTION IN THE HOUSE FINCHEVOLUTION, Issue 3 2000Alexander V. Badyaev Abstract., Sexual dimorphism is thought to have evolved in response to selection pressures that differ between males and females. Our aim in this study was to determine the role of current net selection in shaping and maintaining contemporary sexual dimorphism in a recently established population of the house finch (Carpodacus mexicanus) in Montana. We found strong differences between sexes in direction of selection on sexually dimorphic traits, significant heritabilities of these traits, and a close congruence between current selection and observed sexual dimorphism in Montana house finches. Strong directional selection on sexually dimorphic traits and similar intensities of selection in each sex suggested that sexual dimorphism arises from adaptive responses in males and females, with both sexes being far from their local fitness optimum. This pattern is expected when a recently established population experiences continuous immigration from ecologically distinct areas of a species range or as a result of widely fluctuating selection pressures, as found in our study. Strong and sexually dimorphic selection pressures on heritable morphological traits, in combination with low phenotypic and genetic covariation among these traits during growth, may have accounted for close congruence between current selection and observed sexual dimorphism in the house finch. This conclusion is consistent with the profound adaptive population divergence in sexual dimorphism that accompanied very successful colonization of most of the North America by the house finch over the last 50 years. [source] ESTIMATING PHYLOGENETIC INERTIA IN TITHONIA (ASTERACEAE): A COMPARATIVE APPROACHEVOLUTION, Issue 2 2000Eduardo Morales Abstract., Phylogenetic inertia is a difficult issue in evolutionary biology because we have yet to reach a consensus about how to measure it. In this study a comparative approach is used to evaluate phylogenetic inertia in 14 demographic and morphological characters in 10 species and one subspecies of the genus Tithonia (Asteraceae). Three different methods, autocorrelational analysis, phylogenetic correlograms, and ancestor-state reconstruction, were used to evaluate phylogenetic inertia in these traits. Results were highly dependent on the method applied. Autoregression and phylogenetic eigenvector regression (PVR) methods found more inertia in morphological traits. In contrast, phylogenetic correlograms and ancestor-state reconstruction suggest that morphological characters exhibit less phylogenetic inertia than demographic ones. The differences between results are discussed and methods are compared in an effort to understand phylogenetic inertia more thoroughly. [source] Morphological clines in dendritic landscapesFRESHWATER BIOLOGY, Issue 9 2007A. CHAPUT-BARDY Summary 1. In complex landscapes such as river networks, organisms usually face spatio-temporal heterogeneity and gradients in geomorphological, water, ecological or landscape characteristics are often observed at the catchment scale. These environmental variables determine developmental conditions for larval stages of freshwater insects and influence adult phenotypic characteristics. Environmental clines are therefore expected to generate morphological clines. Such a process has the potential to drive gradual geographical change in morphology-dependent life history traits, such as dispersal. 2. We studied the influence of aquatic and terrestrial environmental factors on morphological variations in Calopteryx splendens across the Loire drainage. To investigate these effects we took explicitly into account the hierarchical structure of the river network. 3. We analysed eight morphological traits. Results showed significant body size variation between tributaries and the presence of a morphological cline at the drainage scale. We observed an effect of pH and water temperature on body size. Individuals in downstream sites were larger than individuals in upstream sites, and adults whose larval stages were exposed to alkaline pH and high temperatures during summer were larger. 4. Body size affects flight abilities in insects. Thus, our results suggest that morphological clines may generate an asymmetric dispersal pattern along the downstream,upstream axis, downstream populations dispersing farther than upstream ones. Such a process is expected to influence population genetic structure at the drainage scale if larval drift and floods do not balance an asymmetrical dispersal pattern of adults along the downstream,upstream gradient. To assess the influence of environmental gradients on the variation of life history traits it is important to understand the population biology of freshwater insects, and more generally of riverine organisms. It is also essential to integrate such data in conservation or restoration programmes. [source] Interpreting the smells of predation: how alarm cues and kairomones induce different prey defencesFUNCTIONAL ECOLOGY, Issue 6 2009Nancy M. Schoeppner Summary 1.,For phenotypically plastic organisms to produce phenotypes that are well matched to their environment, they must acquire information about their environment. For inducible defences, cues from damaged prey and cues from predators both have the potential to provide important information, yet we know little about the relative importance of these separate sources of information for behavioural and morphological defences. We also do not know the point during a predation event at which kairomones are produced, i.e. whether they are produced constitutively, during prey attack or during prey digestion. 2.,We exposed leopard frog tadpoles (Rana pipiens) to nine predator cue treatments involving several combinations of cues from damaged conspecifics or heterospecifics, starved predators, predators only chewing prey, predators only digesting prey or predators chewing and digesting prey. 3.,We quantified two behavioural defences. Tadpole hiding behaviour was induced only by cues from crushed tadpoles. Reduced tadpole activity was induced only by cues from predators digesting tadpoles or predators chewing + digesting tadpoles. 4.,We also quantified tadpole mass and two size-adjusted morphological traits that are known to be phenotypically plastic. Mass was unaffected by the cue treatments. Relative body length was affected (i.e. there were differences among some treatments), but none of the treatments significantly differed from the no-predator control. Relative tail depth was affected by the treatments and deeper tails were induced only when tadpoles were exposed to cues from predators digesting tadpoles or cues from predators chewing + digesting tadpoles. 5.,These results demonstrate that some prey species can discriminate among a diverse set of potential cues from heterospecific prey, conspecific prey and predators. Moreover, the results illustrate that the cues responsible for the full suite of behavioural and morphological defences are not induced by tadpole crushing nor can they be induced by generalized digestive chemicals produced when predators digest their prey. Instead, both prey damage and predator digestion of conspecific tissues appear to be important for communicating predatory risk to phenotypically plastic anuran prey. Importantly, the production of chemical cues by predators may be unavoidable and prey have evolved the ability to eavesdrop on these signals. [source] Increased mite parasitism as a cost of testosterone in male striped plateau lizards Sceloporus virgatusFUNCTIONAL ECOLOGY, Issue 2 2007ROBERT M. COX Summary 1Testosterone (T) co-ordinates the seasonal and sex-specific expression of numerous physiological, behavioural and morphological traits that contribute to male reproductive success. However, increased susceptibility to parasitism has been proposed as a potential cost of elevated plasma T. 2During the spring breeding season, male striped plateau lizards Sceloporus virgatus harbour significantly more ectoparasitic mite larvae (Acari: Trombiculidae) than females. Plasma T levels are also elevated in males at this time, suggesting that sex differences in mite parasitism may be driven by underlying sex differences in circulating T. 3We tested this hypothesis experimentally by manipulating plasma T levels of yearling males via surgical castration and exogenous T implants. Upon recapture of free-living animals, we found significantly fewer mites on castrated males relative to either intact controls or castrated males that received T implants. 4After removing variance attributable to treatment effects, we observed (1) a positive correlation between residual measures of plasma T and mite load, and (2) a negative correlation between residual measures of mite load and growth rate. These correlations suggest a growth cost associated with mite parasitism. 5Previous studies have shown that exogenous T increases parasitism, but ours is one of the few to show that castration also reduces parasitism. This result, coupled with the fact that our induced plasma T levels remain within physiological limits, makes this one of the clearest demonstrations of a functional relationship between T and parasitism in any free-living vertebrate. [source] Hybridization between perennial ryegrass and Italian ryegrass in naturalized Japanese populationsGRASSLAND SCIENCE, Issue 2 2008Hiroyuki Tobina Abstract Introduced Lolium species, including perennial ryegrass (Lolium perenne) and Italian ryegrass (Lolium multiflorum), have been widely utilized in Japan for forage, turf and soil conservation. These ryegrasses have escaped from cultivated areas and become naturalized, and this has become a serious issue in recent years. Interspecific hybrids between perennial ryegrass and Italian ryegrass have often been found in naturalized populations. It has also been suggested that hybridization between plant species might serve as a stimulus for the evolution of invasiveness. We surveyed the genetic structure of naturalized ryegrass populations in Japan using genetic markers that distinguished perennial ryegrass and Italian ryegrass. Of the 55 naturalized populations surveyed, 41 exhibited morphological traits of Italian ryegrass. DNA analysis using simple sequence repeat and chloroplast DNA markers characterized 20 of these 41 populations as Italian ryegrass, with the remaining populations as interspecific hybrid derivatives. Approximately half of the naturalized ryegrasses populations in Japan were inferred to include interspecific hybrids. [source] Morphological and Molecular Data Reveal the Presence of the Invasive Artemia franciscana in Margherita di Savoia Salterns (Italy)INTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 6 2006Graziella Mura Abstract Introduced populations of the American invasive Artemiafranciscana have been reported in Mediterranean countries except for Italy. A recent sampling at Margherita di Savoia revealed the presence of mating pairs in a saltwork known to host only parthenogens. An integrated approach, based on scanning electron microscopy of four morphological traits, discriminant analysis of 13 morphometric characters and 16S rRNA PCR-RFLP profiles of eight endonucleases was implemented for the identification of the invader. Patterns of variability in all assayed markers provided congruent and solid evidence that the allochthonous species is A. franciscana. Native parthenogens are still predominant (,98.4%) in this Italian site but they can be rapidly outcompeted by A. franciscana, as it occurred in similar cases throughout Europe and elsewhere. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Two new species of DiaphanosomaFischer, 1850(Crustacea: Branchiopoda: Cladocera) from the United StatesINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 2 2005Nikolai M. Korovchinsky Abstract Two new species of the genus Diaphanosoma,D. oligosetum and D. dorotheae, from Louisiana and North Carolina respectively, are described. The former species has large head with protruding dorsal part, large lanceolate spine on the basipodite's distal outer end, an extremely reduced number of antennal setae, up to six in adult specimens, and unique armament of valve margin. On the whole, it shows the pronounced combination of primitive and specialized morphological traits. D. dorotheae is a member of D. brachyurum species group differing from its other known representatives in presence of a small but very conspicuous spine on the end of proximal segment of antennal exopodite and a variable number of setae (seven or eight) on the distal segment of the branch. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||||||||||||||||||||