A morphometric and molecular study of Anastrepha pickeli Lima (Diptera: Tephritidae)

This study investigated the level of morphometric and genetic variability among populations of Anastrepha pickeli Lima from several localities in Brazil, one locality in Bolivia and one in Paraguay. Traditional and geometric morphometric analyses were used, as well as sequencing of a fragment of the cytochrome oxidase gene (COI). Six variables were measured from the aculeus for traditional morphometric analysis and 14 landmarks from the right wing were used for geometric analysis, using 10 specimes/population. The aculeus tip length, aculeus width at the end of the cloaca opening, and the serrate part length contributed with 62.7% for grouping. According to the results from traditional morphometry, there was no significant difference, but the multivariate tests showed that the canonical variables were statistically significant, indicating a difference in the wing conformation among populations. Molecular phylogenetic analysis indicated that the populations clustered into three clades and revealed a high level of genetic variation within A. pickeli populations from various geographic regions. Anastrepha pickeli populations differed among them according to the methods used in this study, showing incongruence among the methods used.     

Intra‐ and intermale variability of mature sperm traits analysed in two brackish water populations of the pipefish Syngnathus abaster (Syngnathidae)

Sperm cells are highly diversified in animals, and considerable research effort has focused on variation in sperm morphology among species. Surprisingly, little is known about intraspecific variation in sperm morphology. We analysed within‐ and between‐male variation in mature sperm traits in two brackish water populations of the pipefish Syngnathus abaster. Four morphometric parameters, such as the width and length of the head (including nucleus, and midpiece), length of flagellum and total sperm length were taken into account. The differences in all morphometric parameters analysed between populations were not statistically significant. Moreover, the multidimensional scaling analysis shows that (i) the two populations seem to be indistinguishable based on their spermatozoa and (ii) there is not polymorphism, being sperm not distinguishable into discrete classes both within a single male and between males of each populations. The latter datum does not seem to support the presence of polymorphic sperm in syngnathids. Both populations, however, exhibit a high variation in all sperm traits, both among individual sperm within an ejaculate and among males within each population. The relationship between sperm traits variability and the low selection pressure determined by the absence of postcopulatory sexual selection (i.e. absence of sperm competition) is discussed.     

Variability of morphological traits in Drosophila bipectinata complex

Phenotypic or morphological differences among different populations and sexual dimorphism in certain metric traits were analysed in D. bipectinata complex. It was noticed that different populations of D. bipectinata species group harbour large amount of variation for these characters. In all the populations, morphometric characters such as lengths of femur, tibia and wing length, wing width, number of sternopleural bristles and bristles on epandrium varied significantly among populations. The study indicates that the morphological variations are due to the interplay of genetic and environmental endowments. Further, females had significantly larger values, for lengths of femur, tibia and wing length, wing width and sternopleural bristles.     

Investigations of dengue-2 susceptibility and body size among Aedes aegypti populations

The mosquito Aedes aegypti (L.) (Diptera: Culicidae) is the primary global vector for dengue virus (DENV), yet considerable genetic variation exists among populations in terms of its competence to vector DENV. Variability in adult body size has also been observed among various mosquito populations and several studies have reported a relationship between body size and arbovirus dissemination, although most of these relied on artificially derived variation in body size. Here we examine the relationship between body size and disseminated DENV infection among 10 Ae. aegypti populations reared under optimum laboratory conditions. Body size variability was inferred from wing length measurements and DENV competence was evaluated as the proportion of individuals with disseminated infections following exposure to the dengue-2 JAM1409 strain. There were significant differences in mean wing lengths among populations (anova, F(9,22)= 7.10, P < 0.0001), ranging from 2.16 mm (Bangkok population) to 2.79 mm (MOYO-S [susceptible] population). We also observed significant differences among some populations in mean DENV infection rates (Waller-Duncan K-ratio t-test), ranging from 19.54% (MOYO-R [refractory] population) to 56.60% (MOYO-S population). However, we did not observe evidence for significant interactions between body size and DENV dissemination. We suggest that either the two traits are genetically independent or that our ability to detect interactions between them was limited by their respective inheritances as quantitative traits.     

Morphometric variability on a microgeographical scale in two inshore seabirds

The range of morphometric variation among two inshore seabirds, the Kerguelen cormorant Phalacrocorax atriceps verrucosus and the gentoo penguin Pygoscelis papua was investigated on the Kerguelen and Crozet archipelagos. Four measurements (weight, culmen, flipper and body length for gentoos; weight, culmen, wing and tarsus length for cormorants) were compared in the same seven localities on Kerguelen. In addition, culmen and wing length were compared in four localities on Crozet for gentoo penguins. The two species exhibited similar trends in variation within Kerguelen although the range of variation was greater in cormorants. Compared to the largest cormorants and gentoo of Kerguelen, the smallest stocks were 60 and 36% of the weights, respectively. There is little evidence elsewhere of similar broad morphometric variability in seabirds on a microgeographical scale. The variation observed did not follow a regular cline and appeared to be less related to physical factors (sea temperatures) than to the local biological factors during the breeding season.     

Morphometric analysis of Mexican and South American populations of the Anastrepha fraterculus complex (Diptera: Tephritidae) and recognition of a distinct Mexican morphotype

Discriminant function and cluster analyses were performed on 19 morphometric variables of the aculeus, wing and mesonotum to determine whether populations of Anastrepha fraterculus (Wiedemann) from different parts of Mexico could be distinguished from populations from South America. Samples were collected from seven localities across Mexico, two from Brazil, and one each from Colombia and Argentina. Results showed there were statistically significant differences between Mexican and South American populations with respect to the aculeus (tip length, length of serrated section, mean number of teeth) and wing (width of S-band and connection between S- and V-bands). The degree of morphological variation observed among Mexican populations was extremely low, and as a consequence, the Mexican populations were identified as a single morphotype by discriminant analysis. The 'Andean morphotype'consisting of the Colombian population, and the 'Brazilian morphotype'consisting of the two Brazilian populations plus the single Argentinian population were also distinguished. It was concluded that the macro-geographical morphotypes from Mexico, Colombia, and Brazil plus Argentina correspond to three distinct taxonomic entities. Comparisons of results with those obtained from behavioural, karyotypic, isozyme and DNA studies suggest that sufficient evidence now exists to name a new Mexican species from within the A. fraterculus complex. This will be done in a separate publication. A provisional key to the morphotypes of A. fraterculus studied is provided.     

Molecular and morphometric variation in chromosomally differentiated populations of the grasshopper Sinipta dalmani (Orthopthera: Acrididae)

Sinipta dalmani is an Argentine grasshopper whose chromosome polymorphisms have been widely studied through cytogenetic, morphometric, and fitness component analyses. The present work analysed molecular and morphometric variation in seven chromosomally differentiated populations from Entre Rios and Buenos Aires provinces to analyse population structure. Molecular studies were performed studying RAPD loci and morphometric analyses were carried out measuring five morphometric traits. Genetic variability was high in all studied populations and was characterized by a decrease in H as a function of latitude and temperature. Both conventional F(ST) analysis and Bayesian approach for dominant marker showed that there were significant genetic differences among all populations, between provinces, and among populations within provinces. Entre Rios populations showed higher mean numbers of migrants per generation as well as low genetic differentiation and high gene flow with almost all populations whereas Buenos Aires populations may be considered as a result of a more recently colonization. There is considerable morphometric variation between populations and this variation correlates with latitude and temperature. Our results suggest that selection contributes to phenotypic differentiation among populations by moulding the differences in trait means whereas genetic drift is responsible for differences in the matrix of variance-covariance. The gene flow detected is insufficient to prevent phenotypic and chromosome divergences.     

Wing shape variation in the medium ground finch (Geospiza fortis): an ecomorphological approach

Wing design in birds is subject to a suite of interacting selective pressures. As different performance traits are favoured in different ecological settings, a tight link is generally expected between variation in wing morphology and variation in ecological parameters. In the present study, we document aspects of variation in wing morphology in the medium ground finch ( Geospiza fortis ) on Isla Santa Cruz in the Galápagos. We compare variation in body size, simple morphometric traits (body mass, last primary length, wing length, wing chord, and wing area) and functional traits (wing loading, aspect ratio and wing pointedness) across years, among populations, and between sexes. Functional traits are found to covary across years with differences in climatic conditions, and to covary among populations with differences in habitat structure. In dry years and arid locations, wing aspect ratios are highest and wings are more pointed, consistent with a need for a low cost of transport. In wet years and cluttered habitats, wing loading is lowest and wings are more rounded, suggesting enhanced capabilities for manoeuvrability. Sexes differ in wing loading, with males having lower wing loadings than females. Superior manoeverability might be favoured in males for efficient territory maintenance. Lastly, in contrast to functional traits, we found little consistent inter-annual or inter-site variation in simple morphometric traits.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 129–138.     

Variation in morphological traits and trait asymmetry in field Drosophila serrata from marginal populations

Drosophila serrata occurs along the eastern coast of Australia with a southern range boundary near Sydney. To compare levels of phenotypic variation in marginal and central populations, we examined morphological variation in populations of this species from the southern range boundary and two more northerly populations. The populations differed for wing traits and there was an increase in wing size in the marginal locations which persisted under laboratory culture. The means of wing and bristle traits increased under laboratory culture, whereas wing trait coefficients of variation and variances decreased. Heritability estimates for wing size traits tended to be lower in the field compared with the laboratory, whereas bristle and crossvein length heritabilities were similar across environments. There was evidence for heritable variation in wing and bristle traits in both the marginal and more northern populations, suggesting that genetic variation was not limiting in marginal populations. Fluctuating asymmetry (FA) was also assessed as a measure of genomic and environmental stress. There were no consistent differences among populations for the FA of individual traits, or for a total FA score summed across traits. FA levels in field parents and laboratory‐reared progeny were similar. Overall, the results do not support the conjecture that levels of phenotypic and genetic variability differ between central and marginal D. serrata populations.     

Heritability of Two Morphological Characters within and among Natural Populations of Drosophila melanogaster

Heritabilities of wing length and abdominal bristle number, as well as genetic correlations between these characters, were determined within and among populations of Drosophila melanogaster in nature. Substantial "natural" heritabilities were found when wild-caught flies from one population were compared to their laboratory-reared offspring. Natural heritabilities of bristle number approximated those derived from laboratory-raised parents and offspring, but wing length heritability was significantly lower in nature than in the laboratory. Among-population heritabilities, estimated by regressing population means of wild-caught flies against those of their laboratory-reared descendants, were close to 0.5. The genetic differentiation of populations was clinal with latitude, and was accompanied by significant geographic differences in the norms of reaction to temperature. These clines are similar to those reported on other continents and in other Drosophila species, and are almost certainly caused by natural selection. Genetic regressions between the characters reveal that the cline in bristle number may be a correlated response to geographic selection on wing length, but not vice versa. Our results indicate that there is a sizable genetic component to phenotypic variation within and among populations of D. melanogaster in nature.     

Inter- and Intraspecific Variation in Wild-type and Single Female-derived Populations of Xiphinema americanum-group Nematodes

Ten populations of Xiphinema americanum-group nematodes were reared from individual females to evaluate inter- and intraspecific variation under identical host and environmental conditions. Data indicated that morphometric variability of X. americanum was the result of genetic variation rather than phenotypic plasticity and that genetic heterogeneity was greater than previously thought. Morphometrics of single female derived (SFD) populations identified different genotypes present in the field populations. Stylet length was the least variable morphometric character of SFD populations, but collectively stylet measurements of all individuals formed an uninterrupted continuum ranging from 107-148 μm. Range and frequency of stylet measurements of field populations could be accounted for by the relative proportion of different genotypes in the population. Nine SFD populations were identified as X. americanum sensu stricto, and one SFD population was similar to X. californicum.     

Two Reproductive Life History Types of Kokanee, Onchorynchus nerka, Exhibit Multivariate Morphometric and Protein Genetic Differentiation

Two reproductive types of kokanee are found in Okanagan Lake, British Columbia: one form that spawns in streams, and another that spawns approximately 2–4 weeks later along beaches of the lake. We examined the levels and patterns of genetic and morphometric variation among three populations (1 beach and 2 stream populations) to better understand life history differentiation. We assayed allozyme variation at 74 loci and identified 15 P_0.095 loci. Average F_ST was 0.041 among the three samples; the two stream-spawning populations grouped together in genetic distance analyses. We examined multivariate morphometric variation and fin size/shape variation using 35 truss characters. Populations did not sort morphologically by spawning type in principal component and relative warp analyses. Instead both analyses indicated that one stream-spawning population (Peachland Creek) was significantly more robust and had shallower caudal fins in comparison to the other samples. Second, clear multivariate shape differences between males and females were identified involving jaw size, mid-body dimensions, and caudal fin shape. A simple bivariate plot of tail `forkness' against fork length demonstrated that males had more forked tails and females had flattened tails. Level of differentiation of secondary sexual characteristics did not vary between the spawning types, although the beach-spawning population and one stream-spawning population did not show the strong, gender-discriminating variability in tail forkness. Although these two reproductive life history types of kokanee form discrete genetic groups, environmental differences are apparently insufficient to effect consistent differences in body shape, or fin size and shape between stream and beach-spawning morphs.     

Phenotypic plasticity of body size in a temperate population ofDrosophila melanogaster: When the temperature—size rule does not apply

A natural population ofDrosophila melanogaster in southern France was sampled in three different years and 10 isofemale lines were investigated from each sample. Two size-related traits, wing and thorax length, were measured and the wing/thorax ratio was also calculated. Phenotypic plasticity was analysed after development at seven different constant temperatures, ranging from 12‡C to 31‡C. The three year samples exhibited similar reaction norms, suggesting a stable genetic architecture in the natural population. The whole sample (30 lines) was used to determine precisely the shape of each reaction norm, using a derivative analysis. The practical conclusion was that polynomial adjustments could be used in all cases, but with different degrees: linear for the wing/thorax ratio, quadratic for thorax length, and cubic for wing length. Both wing and thorax length exhibited concave reaction norms, with a maximum within the viable thermal range. The temperatures of the maxima were, however, quite different, around 15‡C for the wing and 19.5‡C for the thorax. Assuming that thorax length is a better estimate of body size, it is not possible to state that increasing the temperature results in monotonically decreasing size (the temperature-size rule), although this is often seen to be the case for genetic variations in latitudinal clines. The variability of the traits was investigated at two levels—within and between lines—and expressed as a coefficient of variation. The within-line (environmental) variability revealed a regular, quadratic convex reaction norm for the three traits, with a minimum around 21‡C. This temperature of minimum variability may be considered as a physiological optimum, while extreme temperatures are stressful. The between-line (genetic) variability could also be adjusted to quadratic polynomials, but the curvature parameters were not significant. Our results show that the mean values of the traits and their variance are both plastic, but react in different ways along a temperature gradient. Extreme low or high temperatures decrease the size but increase the variability. These effects may be considered as a functional response to environmental stress.     

Revisiting Fisher: range size drives the correlation between variability and abundance of British bird eggs

We evaluate the correlation between intraspecific variation in egg size and population size in breeding British birds. Using information on abundance, range occupancy, migration status and phylogenetic relationships among species, we show that a wider geographical distribution rather than larger population size per se best predicts egg size variability. A similar result applies to wing length variability. Results from a phylogenetic path analysis suggest that geographical variation is the most parsimonious causal explanation for high intraspecific variation in common species.     

川西云杉天然种群表型多样性

为了揭示川西云杉(Picea balfouriana)天然种群表型变异程度和变异规律, 以四川甘孜藏族自治州天然分布的川西云杉为研究对象, 调查了12个种群360个单株的种实和针叶表型性状, 采用变异系数、巢式方差分析、相关分析和聚类分析等方法, 分析了种群间和种群内表型多样性。结果表明: 川西云杉表型性状在种群间和种群内存在极其丰富的多样性, 种群间表型分化系数均值为36.53%, 小于种群内变异(63.47%); 球果、针叶、种鳞和种翅的表型分化系数均值分别为47.15%、31.93%、21.89%和45.14%, 球果、针叶、种鳞和种翅4类表型性状的变异系数分别为12.56%、22.16%、12.61%和16.53%, 种鳞的变异系数和表型分化系数最小, 表明其性状最为稳定; 12个表型性状间多数呈显著或极显著正相关, 球果长、球果径、针叶长和种鳞长为川西云杉重要的表型性状。川西云杉表型变异在空间分布上呈现以经度(球果和针叶)和纬度(种鳞和种翅)并存的单向变异模式; 利用种群间欧氏距离进行聚类分析, 可以把川西云杉12个种群划分为3类。     

Vocalizations and morphology: interpreting the divergence among populations of Chough Pyrrhocorax pyrrhocorax and Alpine Chough P. graculus

Capsule Differences in vocalizations among populations are mostly explained on morphological bases, but historical factors may have played a significant role in differentiation processes.

Aims To investigate the relationships among vocal and morphological variation in two corvids: Chough and Alpine Chough.

Methods We used data from 11 populations of Chough and seven populations of Alpine Chough spanning the Palearctic distribution of the two species. Three data sets (morphometry, spectrotemporal parameters of trill calls and acoustic repertoire) were analysed and their variation compared with uni- and multivariate techniques.

Results In both species, morphological differences among populations were correlated to spectro-temporal variation of trills; in particular, frequencies of calls were negatively correlated to wing length (an indicator of body size). By considering only co-existing populations of the two species, the magnitude of morphological and spectrotemporal divergence was similar.

Conclusions In both species, birds from populations with similar morphology uttered similar call types and trills with close spectrotemporal features. In particular, larger-sized populations, as expressed by wing length, emitted lower pitched calls. However, the fact that dissimilarities in repertoire and morphology were correlated cannot be explained only by appealing to functional explanations, as the observed intraspecific morphological variability does not seem to be high enough to promote consistent changes in the pool of calls. In this case, historical factors might have contributed to the present pattern of differentiation.     

The origins of ecotypic variation of rainbow trout: a test of environmental vs. genetically based differences in morphology

Although morphological plasticity has been observed in a variety of taxa, few experimental studies have compared the relative proportion of morphological variability that is accounted for by environmentally induced plasticity, and how much is because of genetically based differences among populations. We compared the morphology of six rainbow trout (Oncorhynchus mykiss) populations from different ecotypic categories that were raised under flowing vs. standing-water conditions. Our data indicate that both environmental conditions and ecotypic differences account for a significant proportion of variation in morphology. Among ecotype effects, however, accounted for a much larger proportion of morphological variability than environmental conditions. Rainbow trout from stream populations had deeper caudal peduncles, and longer fins than lake populations, and rainbow trout from a piscivorous population had larger mouth and head lengths than all other ecotypes. Environmentally induced differences in morphology were primarily related to differences in mouth and head lengths, as well as fin length. Relative to morphometric differences from natural rainbow trout populations, most characteristics deviated in the same direction in our experimental populations. Our data indicate that morphological differences across rainbow trout populations have a genetic basis and may represent locally adaptive characteristics and highlight the role of ecology in promoting phenotypic divergence.     

Variability of Wing Size and Shape in Three Populations of a Recent Brazilian Invader, Zaprionus indianus (Diptera: Drosophilidae), from Different Habitats

Zaprionus indianus (Diptera: Drosophilidae) is an African species that was introduced in Brazil near the end of the 1990’s decade. To evaluate the adaptive potential of morphological traits in natural populations of this recently introduced species, we have investigated wing size and shape variation at Rio de Janeiro populations only two years after the first record of Z. indianus in Brazil. Significant genetic differences among populations from three distinct ecological habitats were detected. The heritability and evolvability estimates show that, even with the population bottleneck that should have occurred during the invasion event, an appreciable amount of additive genetic variation for wing size and shape was retained. Our results also indicated a greater influence of environmental variation on wing size than on wing shape. The importance of quantitative genetic variability and plasticity in the successful establishment and dispersal of Z. indianus in the Brazilian territory is then discussed.     

Genetic variation and plasticity of thorax length and wing length in Drosophila aldrichi and D. buzzatii

Reaction norms across three temperatures of development were measured for thorax length, wing length and wing length/thorax length ratio for ten isofemale lines from each of two populations of Drosophila aldrichi and D. buzzatii. Means for thorax and wing length in both species were larger at 24 °C than at either 18 °C or 31 °C, with the reduction in size at 18 °C most likely due to a nutritional constraint. Although females were larger than males, the sexes were not different for wing length/thorax length ratio. The plasticity of the traits differed between species and between populations of each species, with genetic variation in plasticity similar for the two species from one locality, but much higher for D. aldrichi from the other. Estimates of heritabilities for D. aldrichi generally were higher at 18 °C and 24 °C than at 31 °C, but for D. buzzatii they were highest at 31 °C, although heritabilities were not significantly different between species at any temperature. Additive genetic variances for D. aldrichi showed trends similar to that for heritability, being highest at 18 °C and decreasing as temperature increased. For D. buzzatii, however, additive genetic variances were lowest at 24 °C. These results are suggestive that genetic variation for body size characters is increased in more stressful environments. Thorax and wing lengths showed significant genetic correlations that were not different between the species, but the genetic correlations between each of these traits and their ratio were significantly different. For D. aldrichi, genetic variation in the wing length/thorax length ratio was due primarily to variation in thorax length, while for D. buzzatii, it was due primarily to variation in wing length. The wing length/thorax length ratio, which is the inverse of wing loading, decreased linearly as temperature increased, and it is suggested that this ratio may be of greater adaptive significance than either of its components.     

Population dynamics of fisheries stock enhancement

A comparative analysis was performed on sixteen morphometric characters, in three different juvenile sterlet Acipenser ruthenus L. populations. Specimens were collected from a wild population in the Serbian part of the Danube River ( n  = 46), from aquaculture stocks in the Czech Republic originating from Russia ( n  = 40), and aquaculture stocks in the Slovak Republic originating from Slovakian part of the Danube River ( n  = 28). Average values for total length were 29·9 ± 3·9 cm, 29·1 ± 3·7 cm and 27·3 ± 7·7 cm for Serbia, Czech Republic and Slovak Republic, respectively. Populations were compared using t ‐test and sequential Bonferroni correction for multiple comparisons was applied in order to determine significant differences between them. Results of analysis showed that all three populations differed in prebarbel length, interocular distance and maximum head width. Although all these characters are head‐related, head length itself was very uniform among all populations. The natural population from the Serbian part of the Danube River differed from the populations reared in aquaculture in seven morphometric characters. The two populations reared in aquaculture consistently showed lower morphological variability than the wild population, even though they had different genetic backgrounds (Russia and Slovakia). Future genetic studies will show if this tendency is caused by a reduction in genetic variability.