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Bergmann's Rule (bergmann + rule)
Selected AbstractsAre ecological and evolutionary theories scientific?BIOLOGICAL REVIEWS, Issue 2 2001BERTRAM G. MURRAY Jr. ABSTRACT Scientists observe nature, search for generalizations, and provide explanations for why the world is as it is. Generalizations are of two kinds. The first are descriptive and inductive, such as Boyle's Law. They are derived from observations and therefore refer to observables (in this case, pressure and volume). The second are often imaginative and form the axioms of a deductive theory, such as Newton's Laws of Motion. They often refer to unobservables (e.g. inertia and gravitation). Biology has many inductive generalizations (e.g. Bergmann's Rule and ,all cells arise from preexisting cells') but few, if any, recognized universal laws and virtually no deductive theory. Many biologists and philosophers of biology have agreed that predictive theory is inappropriate in biology, which is said to be more complex than physics, and that one can have nonpredictive explanations, such as the neo-Darwinian Theory of Evolution by Natural Selection. Other philosophers dismiss nonpredictive, explanatory theories, including evolutionary ,theory', as metaphysics. Most biologists do not think of themselves as philosophers or give much thought to the philosophical basis of their research. Nevertheless, their philosophy shows in the way they do research. The plethora of ad hoc (i.e. not universal) hypotheses indicates that biologists are reluctant inductivists in that the search for generalization does not have a high priority. Biologists test their hypotheses by verification. Theoretical physicists, in contrast, are deductive unifiers and test their explanatory hypotheses by falsification. I argue that theoretical biology (concerned with unobservables, such as fitness and natural selection) is not scientific because it lacks universal laws and predictive theory. In order to make this argument, I review the differences between verificationism and falsificationism, induction and deduction, and descriptive and explanatory laws. I show how these differ with a specific example of a successful and still useful (even if now superseded as explanatory) deductive theory, Newton's Theory of Motion. I also review some of the philosophical views expressed on these topics because philosophers seem to be even more divided than biologists, which is not at all helpful. The fact that biology does not have predictive theories does not constitute irrefutable evidence that it cannot have them. The only way to falsify this philosophical hypothesis, however, is to produce a predictive theory with universal biological laws. I have proposed such a theory, but it has been presented piecemeal. At the end of this paper, I bring the pieces together into a deductive theory on the evolution of life history traits (e.g. clutch size, mating relationships, sexual size dimorphism). [source] Bergmann's rule and the mammal fauna of northern North AmericaECOGRAPHY, Issue 6 2004Tim M. Blackburn The observation that "on the whole,,larger species live farther north and the smaller ones farther south" was first published by Carl Bergmann in 1847. However, why animal body mass might show such spatial variation, and indeed whether it is a general feature of animal assemblages, is currently unclear. We discuss reasons for this uncertainty, and use our conclusions to direct an analysis of Bergmann's rule in the mammals in northern North America, in the communities of species occupying areas that were covered by ice at the last glacial maximum. First, we test for the existence of Bergmann's rule in this assemblage, and investigate whether small- and large-bodied species show different spatial patterns of body size variation. We then attempt to explain the spatial variation in terms of environmental variation, and evaluate the adequacy of our analyses to account for the spatial pattern using the residuals arising from our environmental models. Finally, we use the results of these models to test predictions of different hypotheses proposed to account for Bergmann's rule. Bergmann's rule is strongly supported. Both small- and large-bodied species exhibit the rule. Our environmental models account for most of the spatial variation in mean, minimum and maximum body mass in this assemblage. Our results falsify predictions of hypotheses relating to migration ability and random colonisation and diversification, but support predictions of hypotheses relating to both heat conservation and starvation resistance. [source] Bergmann's rule in larval ant lions: testing the starvation resistance hypothesisECOLOGICAL ENTOMOLOGY, Issue 6 2003Amy E. Arnett Abstract., 1.,Body size of the ant lion Myrmeleon immaculatus follows Bergmann's rule , an increase in body size towards higher latitudes. The hypothesis that ant lion body size is larger in the north as an adaptation for starvation resistance was tested. 2.,In a laboratory experiment testing starvation resistance, survivorship curves differed among 10 ant lion populations for both a starved and a fed treatment. 3.,The average number of months survived by each population was correlated positively with latitude for both treatments. Across both treatments and all populations, large individuals survived longer than small individuals; however individuals from high latitudes had higher survivorship, even after factoring out variation due to initial body size. 4.,These results suggest that starvation resistance may be an adaptation for coping with reduced prey availability in high latitudes. Starvation resistance may contribute to latitudinal gradients in body size of ant lions and other ectotherms. [source] Non-native species disrupt the worldwide patterns of freshwater fish body size: implications for Bergmann's ruleECOLOGY LETTERS, Issue 4 2010Simon Blanchet Ecology Letters (2010) 13: 421,431 Abstract In this study, we test whether established non-native species induce functional changes in natural assemblages. We combined data on the body size of freshwater fish species and a worldwide data set of native and non-native fish species for 1058 river basins. We show that non-native fish species are significantly larger than their native counterparts and are a non-random subset of the worldwide set of fish species. We further show that the median body size of fish assemblages increases in the course of introductions. These changes are the opposite of those expected under several null models. Introductions shift body size patterns related to several abiotic factors (e.g. glacier coverage and temperature) in a way that modifies latitudinal patterns (i.e. Bergmann's rule), especially in the southern hemisphere. Together, these results show that over just the last two centuries human beings have induced changes in the global biogeography of freshwater fish body size, which could affect ecosystem properties. [source] Against Bergmann's rule: fly sperm size increases with temperatureECOLOGY LETTERS, Issue 1 2002Wolf U. Blanckenhorn A long-standing school textbook biological rule, Bergmann's rule, asserts that animals (and their constituent parts) grow bigger when it is colder. This seems to hold for many warm-blooded animals, as well as for egg, cell and body size of most cold-blooded animals. A unifying mechanism producing this pattern has not been found. We here provide the first experimental evidence that the size of an important type of cell, namely sperm, increases (rather than decreases) with temperature in a cold-blooded animal, the yellow dung fly. By pointing to an exception, our work either questions the generality of one prominent category of explanation of Bergmann's rule, that of a physiological constraint, or alternatively suggests that sperm differ fundamentally in their physiology from other cells. [source] EXTREME SELECTION ON SIZE IN THE EARLY LIVES OF FISHEVOLUTION, Issue 8 2010Kestrel O. Perez Although fitness typically increases with body size and selection gradients on size are generally positive, much of this information comes from terrestrial taxa. In the early life history of fish, there is evidence of selection both for and against larger size, leaving open the question of whether the general pattern for terrestrial taxa is valid for fish. We reviewed studies of size-dependent survival in the early life history of fish and obtained estimates of standardized selection differentials from 40 studies. We found that 77% of estimated selection differentials favored larger size and that the strength of selection was more than five times that seen in terrestrial taxa. Selection decreased with study period duration and initial length, and disruptive selection occurred significantly more frequently than stabilizing selection. Contrary to expectations from Bergmann's rule, selection on size did not increase with latitude. [source] Global change and carnivore body size: data are stasisGLOBAL ECOLOGY, Issue 2 2009Shai Meiri ABSTRACT Aim, Global warming and other anthropogenic changes to the environment affect many aspects of biology and have often been invoked as causing body size changes in vertebrates. Here we examine a diverse set of carnivore populations in search of patterns in body size change that could reflect global warming (in accord with Bergmann's rule). Location, Global. Methods, We used > 4400 specimens representing 22 carnivore species in 52 populations collected over the last few decades to examine whether size changed with collection date when geography and sex are accounted for. We then examined several factors related to global warming, body mass, diet, and the attributes of the different datasets, to see whether they affect the standardized slope (,) of the size versus time regression. Results, Six of 52 populations we examined show a significant effect of year of collection on body size at the 0.05 probability level. The response of size to global warming does not reflect spatial patterns of size variation, nor do diet or body mass affect tendency of populations to change in body size. Size changes are no more pronounced in populations that have been sampled more recently. However, change, where it occurs, is rapid. Main conclusions, There may be a tendency in the literature to report only cases where recent changes are prevalent. Although in our data only a minority of populations show body size changes, we may see changes accelerating in the future in response to more drastic climatic changes and other anthropogenic changes. [source] Partitioning phylogenetic and adaptive components of the geographical body-size pattern of New World birdsGLOBAL ECOLOGY, Issue 1 2008Lizabeth Ramirez ABSTRACT Aim To evaluate seasonal body-size patterns for New World birds in geographical space, to develop environmental models to explain the gradients, and to estimate phylogenetic and adaptive contributions. Location The Western Hemisphere. Methods We used range maps to generate gridded geometric mean body masses. Summer and winter patterns were distinguished based on breeding and non-breeding ranges. We first generated the geographical gradients, followed by phylogenetic eigenvector regression to generate body sizes predicted by the birds' positions in a phylogenetic tree, which were used to generate the expected phylogenetic gradient. Subtracting the expected pattern from the observed pattern isolated the adaptive component. Ordinary least squares multiple-regression models examined factors influencing the phylogenetic, adaptive and combined components of the seasonal body-size patterns, and non-spatial and spatial models were compared. Results Birds are larger in the temperate zones than in the tropics. The gradient is quantitatively stronger in winter than in summer. Regression models explained 66.6% of the variance in summer mass and 45.9% of the variance in winter mass. In summer, phylogenetic and adaptive responses of birds contribute equally to the gradient. In winter, the gradient in North America is much stronger than that expected by taxonomic turnover, and responses of species independent of their family membership drive the overall pattern. Main conclusions We confirm Bergmann's rule in New World birds and conclude that winter temperatures ultimately drive the pattern, exerting selection pressures on birds that overwhelm patterns expected by phylogenetic inertia at the family level. However, in summer, the movement of migratory species into the temperate zone weakens the gradient and generates a pattern more congruent with that expected from the taxonomic composition of the fauna. The analytical method we develop here represents a useful tool for partitioning the phylogenetic and non-phylogenetic components of spatially explicit macroecological data. [source] The geography of body size , challenges of the interspecific approachGLOBAL ECOLOGY, Issue 6 2007Shai Meiri ABSTRACT Recent compilations of large-scale data bases on the geographical distributions and body sizes of animals, coupled with developments in spatial statistics, have led to renewed interest in the geographical distribution of animal body sizes and the interspecific version of Bergmann's rule. Standard practice seems to be an examination of mean body sizes within higher taxa on gridded maps, with little regard to species richness or phylogeny. However, because the frequency distribution of body sizes is typically highly skewed, average size within grid cells may differ significantly between species-rich and species-poor cells even when the median and modal sizes remain constant. Species richness influences body size patterns because species are not added to communities at random in relation to their size: areas of low diversity are characterized by a higher range of body sizes than is expected by chance. Finally, a consideration of phylogenetic structure within taxa is necessary to elucidate whether patterns in the geography of size result from turnover between or within intermediate taxonomic levels. We suggest that the highest and lowest quantiles of body size distribution be mapped in order to expose possible physiological or ecological limitations on body size. [source] What determines conformity to Bergmann's rule?GLOBAL ECOLOGY, Issue 6 2007Shai Meiri ABSTRACT Aim, Bergmann's rule, the tendency of body size within species in bird and mammal populations to be positively correlated with latitude, is among the best known biogeographical generalizations. The factors behind such clines, however, are not well understood. Here we use a large data base of 79 mammalian carnivore species to examine the factors affecting latitudinal size clines. Location, Worldwide. Methods, We measured the skulls and teeth of carnivores in natural history museums, and calculated the amount of variation in size explained by latitude, supplementing our measurements with published data. We examined the effects of a number of variables on the tendency to show latitudinal clines. Results, We found that geographical range and latitudinal extent are strongly related to size clines. Minimum temperatures across the range, net primary productivity and habitat diversity also have some, albeit much less, influence. Main conclusions, We suggest that species with large geographical ranges are likely to encounter significant heterogeneity in those factors that influence body size, and are thus likely to exhibit size clines. However, the key factors that determine body size may not always operate along a latitudinal (or other geographical) cline, but be spatially linked to patches in the species range. One such important factor is likely to be food availability, which we show is a strong predictor of size in the brown bear (Ursus arctos) but is not associated with a latitudinal cline. We argue that the spatial distribution of key resources within the species range constitutes a significant predictor of carnivore body size. [source] Bergmann's rule does not apply to geometrid moths along an elevational gradient in an Andean montane rain forestGLOBAL ECOLOGY, Issue 1 2004Gunnar Brehm ABSTRACT Aim, Bergmann's rule generally predicts larger animal body sizes with colder climates. We tested whether Bergmann's rule at the interspecific level applies to moths (Lepidoptera: Geometridae) along an extended elevational gradient in the Ecuadorian Andes. Location, Moths were sampled at 22 sites in the province Zamora-Chinchipe in southern Ecuador in forest habitats ranging from 1040 m to 2677 m above sea level. Methods, Wingspans of 2282 male geometrid moths representing 953 species were measured and analysed at the level of the family Geometridae, as well as for the subfamily Ennominae with the tribes Boarmiini and Ourapterygini, and the subfamily Larentiinae with the genera Eois, Eupithecia and Psaliodes. Results, Bergmann's rule was not supported since the average wingspan of geometrid moths was negatively correlated with altitude (r = ,0.59, P < 0.005). The relationship between body size and altitude in Geometridae appears to be spurious because species of the subfamily Larentiinae are significantly smaller than species of the subfamily Ennominae and simultaneously increase in their proportion along the gradient. A significant decrease of wingspan was also found in the ennomine tribe Ourapterygini, but no consistent body size patterns were found in the other six taxa studied. In most taxa, body size variation increases with altitude, suggesting that factors acting to constrain body size might be weaker at high elevations. Main conclusions, The results are in accordance with previous studies that could not detect consistent body size patterns in insects at the interspecific level along climatic gradients. [source] Body size,climate relationships of European spidersJOURNAL OF BIOGEOGRAPHY, Issue 3 2010Wiebke Entling Abstract Aim, Geographic body size patterns of mammals and birds can be partly understood under the framework of Bergmann's rule. Climatic influences on body size of invertebrates, however, appear highly variable and lack a comparable, generally applicable theoretical framework. We derived predictions for body size,climate relationships for spiders from the literature and tested them using three datasets of variable spatial extent and grain. Location, Europe. Methods, To distinguish climate from space, we compared clines in body size within three datasets with different degrees of co-variation between latitude and climate. These datasets were: (1) regional spider faunas from 40 European countries and large islands; (2) local spider assemblages from standardized samples in 32 habitats across Europe; and (3) local spider assemblages from Central European habitats. In the latter dataset climatic conditions were determined more by habitat type than by geographic position, and therefore this dataset provided a non-spatial gradient of various microclimates. Spider body size was studied in relation to latitude, temperature and water availability. Results, In all three datasets the mean body size of spider assemblages increased from cool/moist to warm/dry environments. This increase could be accounted for by turnover from small-bodied to large-bodied spider families. Body size,climate relationships within families were inconsistent. Main conclusions, Starvation resistance and accelerated maturation can be ruled out as explanations for the body size clines recorded, because they predict the inverse of the observed relationship between spider body size and temperature. The relationship between body size and climate was partly independent of geographic position. Thus, the restriction of large-bodied spiders to their glacial refugia owing to dispersal limitations can be excluded. Our results are consistent with mechanisms invoking metabolic rate, desiccation resistance and community interactions to predict a decrease in body size from warm and dry to cool and moist conditions. [source] Bergmann's rule, natural selection and the end of the Panglossian paradigm in ecogeographical analysesJOURNAL OF BIOGEOGRAPHY, Issue 4 2008José Alexandre F. Diniz-Filho No abstract is available for this article. [source] Testing Bergmann's rule in the presence of potentially confounding factors: a case study with three species of Galerida larks in MoroccoJOURNAL OF BIOGEOGRAPHY, Issue 4 2008Alban Guillaumet Abstract Aim, To test Bergmann's rule (which predicts a larger body size in colder areas within warm-blooded vertebrate species) in three partially sympatric species of larks (Galerida theklae, Galerida cristata and Galerida randonii) that occur in Morocco. Location, Morocco. Methods, Restriction fragment length polymorphism techniques applied on cytochrome b haplotypes were used to discriminate G. cristata and G. randonii, and to investigate the effects of interspecific hybridization in their contact zone. A comprehensive statistical framework was then designed to test Bergmann's rule in our three Galerida species (using altitude as a proxy for cold temperatures), while controlling for the possible influence of interspecific hybridization and competition and accounting for spatial autocorrelation. The method we propose is conservative in the sense that potentially confounding factors are adjusted so as to maximize their influence on the variable of interest. Results, Bergmann's rule was strongly supported in G. theklae and G. randonii. However, body size did not respond to altitude in G. cristata, a result that was not simply explained by species-specific differences in geographical ranges and altitudinal span. In G. cristata, we detected a tendency for body size to increase with aridity, in agreement with an alternative definition of Bergmann's rule. However, since G. cristata also hybridizes with G. randonii in a contact zone located in the most arid part of the range of G. cristata, we could not tease apart the relative contribution of selection and hybridization in driving this pattern. Main conclusions, This study highlights the need for careful statistical designs that allow meaningful variables to be picked out from large sets of potential factors. When taking these factors into account, we found that Bergmann's rule was still strongly supported in two out of the three species examined. [source] The importance of phylogenetic scale in tests of Bergmann's and Rapoport's rules: lessons from a clade of South American lizardsJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2005F. B. CRUZ Abstract We tested for the occurrence of Bergmann's rule, the pattern of increasing body size with latitude, and Rapoport's rule, the positive relationship between geographical range size and latitude, in 34 lineages of Liolaemus lizards that occupy arid regions of the Andean foothills. We tested the climatic-variability hypothesis (CVH) by examining the relationship between thermal tolerance breadth and distribution. Each of these analyses was performed varying the level of phylogenetic inclusiveness. Bergmann's rule and the CVH were supported, but Rapoport's rule was not. More variance in the data for Bergmann's rule and the CVH was explained using species belonging to the L. boulengeri series rather than all species, and inclusion of multiple outgroups tended to obscure these macroecological patterns. Evidence for Bergmann's rule and the predicted patterns from the CVH remained after application of phylogenetic comparative methods, indicating a greater role of ecological processes rather than phylogeny in shaping the current species distributions of these lizards. [source] Latitudinal and altitudinal growth patterns of brown trout Salmo trutta at different spatial scalesJOURNAL OF FISH BIOLOGY, Issue 10 2009I. Parra Spatial variation in growth of stream-dwelling brown trout Salmo trutta was explored in 13 populations using a long-term study (1993,2004) in the Bay of Biscay drainage, northern Spain. The high variability in fork length (LF) of S. trutta in the study area was similar to the body-size range found in the entire European distribution of the species. Mean LF at age varied: 0+ years, 57·4,100·7 mm; 1+ years, 111·6,176·0 mm; 2+ years, 155·6,248·4 mm and 3+ years, 194·3,290·9 mm. Average LF at age was higher in main courses and lower reaches compared with small tributaries and upper reaches. Annual specific growth rates (GL) were: 0+ to 1+ years, 0·634,0·825 mm mm,1 year,1; 1+ to 2+ years, 0·243,0·342 mm mm,1 year,1; 2+ to 3+ years, 0·166,0·222 mm mm,1 year,1, showing a great homogeneity. Regression models showed that water temperature and altitude were the major determinants of LF at age variability within the study area. A broader spatial analysis using available data from stream-dwelling S. trutta populations throughout Europe indicated a negative relationship between latitude and LF of individuals and a negative interaction between latitude and altitude. These findings support previous evidence of the pervasive role of water temperature on the LF of this species. Altitude appeared as the overall factor that includes the local variation of other variables, such as water temperature or food availability. At a larger scale, latitude was the factor that encompassed these environmental gradients and explained the differences in LF of S. trutta. In summary, LF at age in stream-dwelling S. trutta decreases with latitude in Europe, the converse of Bergmann's rule. [source] Global warming, Bergmann's rule and body mass , are they related?JOURNAL OF ZOOLOGY, Issue 4 2002The chukar partridge (Alectoris chukar) case Abstract Using museum specimens collected in Israel during the second half of the 20th century, no support was found for the hypothesis that body mass and tarsus length of chukar partridges Alectoris chukar has changed as a result of global warming. Body mass showed fluctuations during the year, reaching a maximum in late winter and spring and a minimum in summer. Bergmann's rule predicts that in warm-blooded animals, races from warm regions will be smaller than races from colder regions, and a wider explanation states that body size is positively related to latitude. Because of its topography and varied climate, Israel provides a unique opportunity to separate partly the effect of latitude from that of ambient temperature, thus testing if Bergmann's rule is related to latitude or to climatic variables. We found that body mass (and marginally also tarsus length) declined significantly with decreasing latitude in accordance with the wider explanation of Bergmann's rule, but ambient temperature explained a much smaller fraction of the variation in body mass than latitude. These results weaken the traditional explanation to Bergmann's rule that a heat conservation mechanism causes the latitudinal size variation. [source] Taxonomic and biogeographical status of guanaco Lama guanicoe (Artiodactyla, Camelidae)MAMMAL REVIEW, Issue 2 2006BENITO A. GONZÁLEZ ABSTRACT 1We review the status of the four currently recognized guanaco Lama guanicoe subspecies, and provide information about their taxonomy and distribution. The success of guanaco in inhabiting open habitats of South America is based mainly on the flexibility of their social behaviour and ecophysiological adaptations to harsh environments. 2Lönnberg described the first subspecies, L. g. cacsilensis, at the beginning of the 20th century. Forty years later Krumbiegel described L. g. voglii, based on skull measurements and pelage colouration. The other two subspecies, L. g. huanacus and L. g. guanicoe, were classified as subspecies by Krumbiegel based on pelage colouration and body size, while maintaining the original Latin names and descriptors. 3Further guanaco populations have been incorporated into each of these subspecies, based on their proximity to the type locality but without attention to the homogeneity of phenotype or habitat and only limited consideration of Bergmann's rule based on scarce skulls. Two alternative geographical ranges were proposed in the middle and towards the end of the 20th century. Discrepancies occur in the geographical range of each subspecies. 4Molecular studies based on mitochondrial DNA cytochrome b sequences recognized only two subspecies: the Peruvian L. guanicoe cacsilensis and the rest of the populations grouped in the clade recognized as L. g. guanicoe. We conclude that the evolutionary biology of L. guanicoe requires a significant revision with respect to biogeography. Phylogeographical data hold particular value in developing conservation strategies, particularly for some of the reduced and marginal populations and/or subspecies and will support IUCN (The World Conservation Union) Red List classification. [source] Fecundity selection predicts Bergmann's rule in syngnathid fishesMOLECULAR ECOLOGY, Issue 6 2009ANTHONY B. WILSON Abstract The study of latitudinal increases in organismal body size (Bergmann's rule) predates even Darwin's evolutionary theory. While research has long concentrated on identifying general evolutionary explanations for this phenomenon, recent work suggests that different factors operating on local evolutionary timescales may be the cause of this widespread trend. Bergmann's rule explains body size variation in a diversity of warm-blooded organisms and there is increasing evidence that Bergmann's rule is also widespread in ectotherms. Bergmann's rule acts differentially in species of the Syngnathidae, a family of teleost fishes noted for extreme adaptations for male parental care. While variation in body size of polygamous Syngnathus pipefish is consistent with Bergmann's rule, body size is uncorrelated with latitude in monogamous Hippocampus seahorses. A study of populations of Syngnathus leptorhynchus along a natural latitudinal and thermal gradient indicates that increases in body size with latitude maintain the potential reproductive rate of males despite significant decreases in ambient temperatures. Polygyny is necessary in order to maximize male reproductive success in S. leptorhynchus, suggesting a possible a link between fecundity selection and Bergmann's rule in this species. [source] Genetic, geographic, and environmental correlates of human temporal bone variationAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 3 2007Heather F. Smith Abstract Temporal bone shape has been shown to reflect molecular phylogenetic relationships among hominoids and offers significant morphological detail for distinguishing taxa. Although it is generally accepted that temporal bone shape, like other aspects of morphology, has an underlying genetic component, the relative influence of genetic and environmental factors is unclear. To determine the impact of genetic differentiation and environmental variation on temporal bone morphology, we used three-dimensional geometric morphometric techniques to evaluate temporal bone variation in 11 modern human populations. Population differences were investigated by discriminant function analysis, and the strength of the relationships between morphology, neutral molecular distance, geographic distribution, and environmental variables were assessed by matrix correlation comparisons. Significant differences were found in temporal bone shape among all populations, and classification rates using cross-validation were relatively high. Comparisons of morphological distances to molecular distances based on short tandem repeats (STRs) revealed a significant correlation between temporal bone shape and neutral molecular distance among Old World populations, but not when Native Americans were included. Further analyses suggested a similar pattern for morphological variation and geographic distribution. No significant correlations were found between temporal bone shape and environmental variables: temperature, annual rainfall, latitude, or altitude. Significant correlations were found between temporal bone size and both temperature and latitude, presumably reflecting Bergmann's rule. Thus, temporal bone morphology appears to partially follow an isolation by distance model of evolution among human populations, although levels of correlation show that a substantial component of variation is unexplained by factors considered here. Am J Phys Anthropol 2007. © 2007 Wiley-Liss, Inc. [source] Latitudinal clines in body size, but not in thermal tolerance or heat-shock cognate 70 (HSC70), in the highly-dispersing intertidal gastropod Littorina keenae (Gastropoda: Littorinidae)BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2010HYUK JE LEE Natural populations of widely-distributed animals often exhibit clinal variation in phenotypic traits or in allele frequencies of a particular gene over their geographical range. A planktotrophic intertidal snail, Littorina keenae is broadly distributed along the north-eastern Pacific coast through a large latitudinal range (24°50,N,43°18,N). We tested for latitudinal clines in two complex phenotypic traits , thermal tolerance and body size , and one single locus trait , heat shock cognate 70 (HSC70) , in L. keenae along almost its entire geographical range. We found only weak evidence for a latitudinal cline in the thermal tolerance and no evidence for a cline in allele frequencies at HSC70. However, as predicted by Bergmann's rule, we detected a strong latitudinal cline that accounted for 60% of the variance in body size (R2 = 0.598; P < 0.001). In contrast, body size did not significantly affect thermal tolerance. HSC70 showed no genetic differentiation among the populations, supporting our previous mitochondrial gene-based estimate of high gene flow during this snail's free-swimming larval stage. Given that L. keenae experiences panmixia along its species range, the observed size cline may be partially or entirely caused by a phenotypically plastic response to local thermal environments rather than by genetic divergence in body size among populations in response to locally optimizing natural selection. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 494,505. [source] Phenotypic evolution in high-elevation populations of western fence lizards (Sceloporus occidentalis) in the Sierra Nevada MountainsBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2010ADAM D. LEACHÉ Adaptive divergence in response to variable habitats, climates, and altitude is often accentuated along elevation gradients. We investigate phenotypic evolution in body size and coloration in the western fence lizard (Sceloporus occidentalis Baird & Girard, 1852) across elevation gradients in Yosemite National Park, California, situated in the Sierra Nevada mountains of Western North America. High-elevation populations occurring above 2100 m a.s.l. are recognized as a separate subspecies (Sceloporus occidentalis taylori Camp, 1916), with a distinctive phenotype characterized by a large body size and extensive blue ventral pigmentation. We sampled S. occidentalis from across elevation gradients in Yosemite National Park, California, and collected phenotypic data (body size and ventral coloration measurements; 410 specimens) and mitochondrial DNA sequence data (complete NADH1 gene; 969 bp, 181 specimens) to infer phylogenetic relationships, and examine the genetic and phenotypic diversity among populations. Populations of S. occidentalis in Yosemite National Park follow Bergmann's rule and exhibit larger body sizes in colder, high-elevation environments. The high-elevation subspecies S. o. taylori is not monophyletic, and the mitochondrial DNA genealogy supports a model of convergent phenotypic evolution among high-elevation populations belonging to different river drainages. The hypothesis that separate populations of S. occidentalis expanded up river drainages after the recession of glaciers is supported by population demographic analyses, and suggest that Bergmann's clines can evolve rapidly along elevation gradients. The distinctive high-elevation phenotype that is attributable to S. o. taylori has evolved independently several times, and includes adaptive phenotypic changes associated with increases in body size and ventral coloration. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 630,641. [source] Evolutionary history of the bank vole Myodes glareolus: a morphometric perspectiveBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2010RONAN LEDEVIN The bank vole experienced a complex history during the Quaternary. Repeated isolation in glacial refugia led to the differentiation of several lineages in less than 300 000 years. We investigated if such a recent differentiation led to a significant divergence of phenotypic characters between European lineages, which might provide insight into processes of intraspecific differentiation. The size and shape of the first and third upper molars, and first lower molar, of bank voles genetically attributed to different lineages were quantified using an outline analysis of their occlusal surface. The three teeth present similar trends of decreasing size towards high latitudes. This trend, the inverse of Bergmann's rule, is interpreted as the result of a balance between metabolic efficiency and food availability, favouring small body size in cold regions. Molar shape appeared to differ between lineages despite genetic evidence of suture zones. A mosaic pattern of evolution between the different teeth was evidenced. The analysis of such phenotypic features appears as a valuable complement to genetic analyses, providing a complementary insight into evolutionary processes, such as selective pressures, that have driven the differentiation of the lineages. It may further allow the integration of the paleontological dimension of the bank vole phylogeographic history. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 681,694. [source] Geographic variation in jungle cat (Felis chaus Schreber, 1777) (Mammalia, Carnivora, Felidae) body size: is competition responsible?BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2007SHOMITA MUKHERJEE There is a striking difference in body size of jungle cats (Felis chaus) in the west and the east of their distribution, with Israeli cats being 43% heavier than Indian cats. We tested the hypothesis that increasing competition from other small felids towards the east is responsible for the difference in body size. We measured jungle cat skulls for eight cranial and dental variables and related these to independent variables such as species richness (local and regional), latitude, longitude, temperature, and precipitation. Data from a narrow band between latitudes 24.0°N and 33.9°N, where Bergmann's rule was largely not observed, showed that the western population (, 50.0°E longitude) of jungle cats is larger than the eastern (> 60.0°E longitude) population with the size difference being most evident in the upper carnassials (P4L). Species richness at the regional level showed a significant negative relation to P4L. An even spacing in condylobasal length for a small-cat guild from India through null model analysis indicated the occurrence of character displacement. The results support the hypothesis that competition is responsible for geographical variation in jungle cat body size in the region where Bergmann's rule does not apply. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 92, 163,172. [source] | ||||||||||||||||||||||||||||