Intraspecific Correlations Research Articles

Phylogenetic analysis of correlation structure in stalk-eyed flies (Diasemopsis, Diopsidae).

Morphological divergence among species may be constrained by the pattern of genetic variances and covariances among traits within species. Assessing the existence of such a relationship in nature requires information on the stability of intraspecific correlation and covariance structure and the correspondence of this structure to the pattern of evolutionary divergence within a lineage. Here, we investigate these issues for nine morphological traits and 15 species of stalk-eyed flies in the genus Diasemopsis. Within-species matrices for these traits were generated from phenotypic data for all the Diasemopsis species and from genetic data for a single Diasemopsis species, D. dubia. The among-species pattern of divergence was assessed by calculating the evolutionary correlations for all pairwise combinations of the morphological traits along the phylogeny of these species. Comparisons of intraspecific matrices reveal significant similarity among all species in the phenotypic correlations matrices but not the covariance matrices. In addition, the differences in correlation structure that do exist among species are not related to their phylogenetic placement or change in the means of the traits. Comparisons of the phenotypic and phylogenetic matrices suggest a strong relationship between the pattern of evolutionary change among species and both the intraspecific correlation structure and the stability of this structure among species. The phenotypic and the phylogenetic matrices are significantly similar, and pairs of traits whose intraspecific correlations are more stable across taxa exhibit stronger coevolution on the phylogeny. These results suggest either the existence of strong constraints on the pattern of evolutionary change or a consistent pattern of correlated selection shaping both the phenotypic and phylogenetic matrices. The genetic correlation structure for D. dubia, however, does not correspond with patterns found in the phenotypic and phylogenetic data. Possible reasons for this disagreement are discussed.

Decreasing teleconnections with inter-site distance in monthly climatic data and tree-ring width networks in a mountainous Alpine area

The similarities in time series recorded at sites which are distant from each other are called teleconnections. In this paper, the loss of such correlations with inter-site distance was investigated for both climatic and dendrochronological data sets, with 70 tree-ring chronologies. A dense network of weather stations was studied in the southeastern French Alps, covering complex climatic gradients over three departments. 78 sites with precipitation data (with a total of 48 756 monthly values), and 48 stations that recorded temperature (with 20 722 monthly mean values) were analysed. In the same area, four coniferous species (mountain pine and stone pine, European larch and Norway spruce) provided 37 ring-width chronologies for high elevation sites near the timberline. Both silver fir and Norway spruce provided a second tree-ring chronology network for 33 different sites at lower elevations. The teleconnections between precipitation series were found to be higher than those observed for temperature over short distances, but the maximum threshold distance was lower (193 km) compared to a positive correlation distance that exceeds 500 km for temperature. The maximum temperatures had stronger teleconnections than minimum values (522 km versus 476 km), since the latter are linked more with other site factors, such as slope, exposure and local topography. As expected, the tree-ring chronologies showed weaker teleconnections than the climatic series, with a threshold distance of 374 km obtained for all high elevation forests. The coniferous species with high intra-specific teleconnections over large distances were, in decreasing importance, Pinus uncinata (> 500 km), Picea abies (477 km), Pinus cembra (over 254 km) and Larix decidua (over 189 km only). The two former species showed the highest intra-specific correlations (with mean correlation R=0.625 and 0.666). The dendrochronological teleconnections were found to have a extent lesser for trees species that depend on rainfall (such as larch, and stone pine). They are enhanced, however, for temperature sensitive species such as spruce and mountain pine (a drought resistant tree). Therefore, these two latter conifers appear to be especially suitable for climatic reconstruction over large distances in mountainous areas. However, teleconnections within silver fir (Abies alba) and spruce chronologies were sharply reduced (over 131 km and 135 km) in lower elevation forests, underlining the interest of timberline forests for dendroclimatology. A better knowledge of the spatial correlations in climatic series and ring-width data may enable the optimisation of weather station networks. It may also permit a better choice of weather stations used for dendroclimatology, either for tree-ring and climate relationship calibration or for climate reconstructions. In dendrochronology, wood dating also requires the knowledge of to what extent remote ring-width chronologies can be used.

Morphological Developmental Stability in Plants: Patterns and Causes.

Minor bilateral or radial asymmetry of leaves or flowers, the frequency of phenodeviants, intraindividual variation in repeated characters, and fractal dimensions of morphology are considered to represent measures of developmental instability since deviations from regularity of the phenotype constitute a measure of the inability to maintain developmental precision during ontogeny. First, we review patterns of fluctuating asymmetry in plants and show that levels of asymmetry are considerably greater than in animals. While petal asymmetry tends to decrease with petal size within species, leaf asymmetry tends to increase with leaf size. Intraspecific correlations of petal asymmetry and leaf asymmetry are weakly positive. Second, a meta-analysis of the effects of environmental factors hypothesized to increase asymmetry in leaves and flowers, such as radiation, ultraviolet light, excess artificial fertilizer, pollutants, extreme saline conditions, herbivory, and competition, showed intermediate (i.e., explaining 10% of the variance) to large (i.e., explaining 25% of the variance) effects. Third, a meta-analysis of the effects of genetic factors hypothesized to contribute to increased asymmetry in plants, such as homozygosity, hybridization, mutation, and quantitative genetic differences among individuals, showed variable but usually significant effects, although the number of studies generally was small. Controlled experimental studies of environmental and genetic effects on developmental instability of plants may increase our understanding of the mechanisms causing developmental instability.

Correlations between measures of heat resistance and acclimation in two species of Drosophila and their hybrids

Associations between traits may differ at the interspecific and intraspecific levels, making it difficult to predict long term evolutionary constraints. In this study we used replicate hybrid lines generated from crosses betweenDrosophila serrataandD. birchiito investigate correlations between measures of heat resistance and acclimation responses. Within each species, knockdown heat resistance was uncorrelated with heat resistance as measured by mortality. In contrast,D. serratawas more resistant thanD. birchiifor both measures of heat resistance. Thus, inter- and intraspecific correlations between measures of heat resistance differ. In the hybrids, there was no evidence for a correlation between knockdown time and heat induced mortality. Hybrid data did suggest a trade-off between acclimation for knockdown heat resistance and heat resistance as measured by mortality. We argue that hybrids between species are a potentially useful tool for studying traits such as acclimation responses that show little genetic variation within species.

Correlations between measures of heat resistance and acclimation in two species ofDrosophilaand their hybrids

Associations between traits may differ at the interspecific and intraspecific levels, making it difficult to predict long term evolutionary constraints. In this study we used replicate hybrid lines generated from crosses betweenDrosophila serrataandD. birchiito investigate correlations between measures of heat resistance and acclimation responses. Within each species, knockdown heat resistance was uncorrelated with heat resistance as measured by mortality. In contrast,D. serratawas more resistant thanD. birchiifor both measures of heat resistance. Thus, inter- and intraspecific correlations between measures of heat resistance differ. In the hybrids, there was no evidence for a correlation between knockdown time and heat induced mortality. Hybrid data did suggest a trade-off between acclimation for knockdown heat resistance and heat resistance as measured by mortality. We argue that hybrids between species are a potentially useful tool for studying traits such as acclimation responses that show little genetic variation within species.

Variability of wood extractives among Quercus robur and Quercus petraea trees from mixed stands and their relation to wood anatomy and leaf morphology

Heartwood ellagitannins and volatile extractives were studied by high-pressure liquid chromatography and gas chromatography - mass spectrometry after extraction of wood samples taken from 54 mature trees of pedunculate oak (Quercus robur L.) and sessile oak (Quercus petraea (Matt.) Liebl.) from 14 mixed stands located in the forest of Cîteaux (Bourgogne). These same trees had been previously subject to detailed study of leaf morphology and wood anatomy. Over 50 compounds, of diverse chemical types, were identified in the wood extracts and over 30 of these compounds were quantified. No species-specific extractives were identified, but the amounts of ellagitannins and a small number of volatile compounds, including cis- and trans-β-methyl-γ-octalactone isomers, were found to vary significantly between the two species. Multivariate analyses of these extractives allowed the classification of samples according to species, although less distinctly than similar analyses using leaf morphological characteristics. No strong intraspecific correlations between chemical constituents and anatomical or morphological characteristics were found that were common for both species. Nonetheless, sessile oaks displaying atypical wood anatomy were also less morphologically and chemically representative of their species. Trees possessing the lowest levels of cis- and trans-β-methyl-γ-octalactone are found to be those with a morphology the least distinct of either species.

The Hamilton and Zuk Hypothesis Revisited: a Meta-Analytical Approach

Abstract The Hamilton & Zuk (1982) hypothesis of parasite-mediated sexual selection has been the subject of both inter- and intraspecific tests. Past reviews have used vote counting to determine whether this hypothesis is supported by empirical evidence. This study reanalysed 199 separate quantitative assessments of a central prediction of the Hamilton & Zuk hypothesis using meta-analytical techniques. Overall, our meta-analysis showed that there was a significant negative effect of parasites on male showiness as predicted. However the magnitude of this effect varied between host taxa and between endo and ectoparasitic taxa. As a whole intraspecific correlations between parasite load and male showiness provided very little support for the hypothesis with only the effect of parasites on fish morphology matching the Hamilton & Zuk prediction. There was more support for the hypothesis from interspecific studies especially those based upon the original Hamilton & Zuk (1982) data set, although other bird studies provided weaker support. The generality of the Hamilton & Zuk hypothesis in respect to parasite mediated sexual selection across taxa is thrown into doubt by these results. However, in some specific host-parasite systems the role of parasites appears important and future intraspecific tests of parasite-mediated sexual selection should perhaps focus on such systems.

Cloacal protuberances and extreme sperm production in Australian fairy-wrens

In many passerine species males have enlarged cloacal protuberances during the breeding season. One hypothesis for the evolution of cloacal protuberances posits that they are a response to sperm competition and thus predicts that both within and between species the size of the protuberance correlates with the number of sperm stored. Here we provide the first intraspecific test of this hypothesis. In Australian fairy-wrens (Aves: Maluridae) females regularly mate outside of their social group resulting in intense sperm competition among males. Male fairy-wrens develop enlarged cloacal protuberances, and in a study of three species, splendid fairy-wren, white-winged fairy-wren, and variegated fairy-wren, we found significant intraspecific correlations between the size of a male’s protuberance and the stored sperm reserves in two of the three species. Males of these species had extreme numbers of sperm in their cloacal protuberances, up to 8.3 billion for splendid fairy-wrens, which should be available for a single ejaculate and is the most ever reported in an avian species. Studies of both captive and wild males showed that individuals can produce as many as 2 billion sperm per day. These data support the sperm competition hypothesis for the evolution of cloacal protuberances and highlight extreme sperm production as one possible outcome of sperm competition.

EVOLUTION OF BASAL METABOLIC RATE AND ORGAN MASSES IN LABORATORY MICE.

Animal species of similar body mass vary widely in basal metabolic rate (BMR). A central problem of evolutionary physiology concerns the anatomical/physiological origin and functional significance of that variation. It has been hypothesized that such interspecific differences in wild animals evolved adaptively from differences in relative sizes of metabolically active organs. In order to minimize confounding phenotypic effects and maximize relevant genetic variation, we tested for intraspecific correlations between body-mass-corrected BMR and masses of four organs (heart, kidney, liver, and small intestine) among six inbred strains of mice. We found significant differences between strains in BMR and in masses of all four organs. Strains with exceptionally high (or low) BMR tended to have disproportionately large (or small) organs. The mass of each organ was correlated with the masses of each of the other three organs. Variation in organ masses accounted for 52% of the observed variation in BMR, of which 42% represented between-strain variation, and 10% represented within-strain variation. This conclusion is supported by published measurements of metabolic rates of tissue slices from the four organs. The correlation between BMR and intestine or heart mass arose exclusively from differences between strains, while the correlation between BMR and liver or kidney mass also appeared in comparing individual mice within the same strain. Thus, even though the masses of the four examined organs account for no more than 17% of total body mass, their high metabolic activities or correlated factors account for much of the variation in BMR among mice. We suggest that large masses of metabolically active organs are subject to natural selection through evolutionary trade-offs. On the one hand, they make possible high-energy budgets (advantageous under some conditions), but on the other hand they are energetically expensive to maintain.

COMPARATIVE METHODS AT THE SPECIES LEVEL: GEOGRAPHIC VARIATION IN MORPHOLOGY AND GROUP SIZE IN GREY-CROWNED BABBLERS (POMATOSTOMUS TEMPORALIS).

We show that a new comparative method that sheds light on evolutionary trends among species may also illuminate trends within species. This finding comes from a phylogenetic autocorrelation analysis of morphological traits among individuals sampled from ten populations of a cooperatively breeding songbird, the Grey-crowned Babbler (Pomatostomus temporalis). Highly variable mitochondrial DNA (mtDNA) sequences from both the eastern (Pomatostomus temporalis temporalis) and western (Pomatostomus temporalis rubeculus) lineages were used to define genetic distances among 120 individuals and to estimate correlations among individuals in wing length, tarsus length, and body weight via an intraspecific weighting matrix. The autoregressive model effectively removed intraspecific correlations for all three morphological variables, and the proportion of the total phenotypic variance due to genealogical relationships varied from 0.68 (weight) to 0.23 (tarsus). The analysis revealed correlations among the specific components of traits, in which none were previously detected (type-I error) and diminished correlations that appeared strong when phylogeny was ignored. Group size was the only trait for which the autoregressive model failed to remove intraspecific correlations, a result likely due to the plasticity, convergence, and clinal variation in this trait in both the eastern and western lineages. The autocorrelation analysis weakened significant negative correlations between group size and total values for wing length and body weight, but the interpretation of this result depends on the adaptive significance ascribed to the "phylogenetic component" of trait values removed by the analysis. Comparative methods employing distance matrices are one useful way of summarizing the pattern of nonhierarchical relationships among conspecific individuals ("tokogenetic" relationships, sensu Hennig).

Prey abundance and male parental behaviour in Acrocephalus warblers

This study examined the prey abundance at nesting sites of five different Acrocephalus warbler species. Intraspecific variations in prey density were analysed to determine the relative significance of this ecological factor for different mating systems and components of male parental behaviour. The Great Reed Warbler Acrocephalus arundinaceus, a facultatively polygynous species, nested in areas with the highest insect abundance. Its intraspecific variation in prey density (between different territories) was the highest while the male: female offspring feeding ratio was the lowest. At the other extreme, the monogamous Moustached Warbler Acrocephalus melanopogon and Reed Warbler Acrocephalus scirpaceus nested in areas with the lowest prey abundance and lowest intraspecific variation. Males of these species had the highest involvement in feeding young. In the Moustached Warbler and Marsh Warbler Acrocephalus palustris, an intraspecific comparison revealed a negative correlation between insect abundance and the male feeding component; a tendency in this direction was found for the Reed Warbler, while no correlation was evident in the polygynous Great Reed Warbler. These data demonstrate a general pattern relating prey abundance, mating systems and male parental investment on an interspecific level. However, intraspecific correlations revealed a net of complex interdependence. One of the factors which may be important is resource predictability. We found a significant correlation between certain vegetation types and insect abundance. The vegetation composition of territories is further influenced by interspecific dominance relationships whereby the dominant Great Reed Warbler occupies territories with the vegetation type which correlates with high prey abundance while the overlapping Moustached Warbler and Reed Warbler are restricted to areas with lower insect density.

SOUND PRODUCTION AND SOUND EMISSION IN SEVEN SPECIES OF EUROPEAN TETTIGONIIDS. PART I. THE DIFFERENT PARAMETERS OF THE SONG; THEIR RELATION TO THE MORPHOLOGY OF THE BUSHCRICKET

Abstract Comparative studies of sound production and sound emission in seven species of European tettigoniids have been carried out. The species chosen were two Tettigoniines (Tettigonia cantans, Tettigonia viridissima), two Ephippigerines (Ephippiger discoidalis, Ephippiger ephippiger), and three Decticines (Decticus albifrons, Decticus verrucivorus, Psorodonotus illyricus). The factors which determined the choice of species were the different morphology (for example body shape and weight, and wing size) of the three subfamilies. The parameters of the different songs (e.g. dominant frequency, intensity) are normally not correlated to any of the investigated morphological characteristics of the animals. In the brachypterous species intraspecific correlations exist between wing size and the dominant low frequency band of the call. This frequency band is also observable at related higher frequencies in the ultrasonic range (20–60 kHz), the observed band width increasing with frequency. Sound emission in all...

Zur Ökologie vonPomatoceros triqueter (Serpulidae, Polychaeta)

Based on previous studies (Klockner, 1976b) dealing with field investigations on breeding season, choice of substratum, growth and mortality of the sessile filter-feeding tube wormPomatoceros triqueter in Helgoland waters (southern North Sea), data from laboratory experiments on the physiological potential of the polychaete in regard to temperature are presented. Adult worms tolerated temperatures from −3° C (24 h LT 28) to 30° C (24 h LT 50) when heated or cooled in steps of 1 C° d−1; a two-week period of acclimation within 6° to 18° C did not change their tolerance. Standard oxygen consumption and regeneration of the calcareous tube were found to be dependent on temperature, body weight and food supply; acclimation periods of two weeks had no significant influence. Highly increasing metabolic rates were noted between 6° and 18° C (Q10-values up to 6) and a maximum was found between 20° and 24° C (0.32 μg O2 mg−1h−1 and 10.2 μg CaCO3 mg−1d−1); tube regeneration followed a nonlinear regression of y=ax−b when compared to body weight and was reduced by starving animals to less than 50% within 15 days. Filtration activity ofP. triqueter, however, was found to be highly independent of temperature from 12° to 24° C; maximum activity was 1 ml mg−1 h−1 (all data refer to fresh weight). For comparisons with the results of previous field investigations onP. triqueter some intraspecific correlations of the different parameters employed (tube sizes, fresh and dry weight) are presented as exponential functions of y=axb.

Effects of humidity and body size on evaporative water loss in three desert rodents

1. 1. Pulmocutaneous evaporative water loss (EWL) was studied in 3 Namib Desert rodents at three relative humidities (RH). 2. 2. Mean EWL at each RH in these species was inversely correlated with RH, and the dependence of EWL on RH was described relatively well by a linear model. 3. 3. In 2 species, EWL sample variances tended to decrease with increasing RH. 4. 4. Interspecific differences in body size were inversely correlated with mean EWL, EWL sample variances, the slopes of the regressions of EWL on RH, and the intraspecific correlations between body size and EWL. 5. 5. Body size effects on EWL appeared to interact with RH effects.