Population level differences in adult body mass emerge in infancy and early childhood: Evidence from a global sample of low and lower‐income countries

Many studies have linked measures of adult body shape and mass in ancient and contemporary populations to ecogeographical variables such as temperature and latitude. These results tend to support Bergmann's rule, which posits that bodies will be relatively less slender for their height in colder climates and more slender in warmer climates. Less well explored is the ontogeny of these population‐level differences. Here we use data on infants and children from 46 low and lower income countries to test whether children's weight for height is associated with measures of temperature and latitude. We also test the hypothesis that children living in areas with greater pathogen prevalence will be lighter for their height because of life history trade‐offs between investment in immune function and growth. Finally, we test whether population specific adult body mass predicts infant and child body mass, and whether this is independent of ecogeographical variables. Our results show that maximum monthly temperature explains 17% of children's weight for height while adult population‐level body mass explains ～44% (Table 5 ). The measures of pathogen prevalence explain little of the variation in children's body shape (8%; P > 0.05). Our results suggest that population differences are consistent with Bergmann's rule but parental body shape explains more variance. Moreover, these population‐level differences arise early in development, suggesting that any possible environmental influences occur in utero and/or result from epigenetic or population genetic differences. Am J Phys Anthropol 154:232–238, 2014. © 2014 Wiley Periodicals, Inc.     

Females are the ecological sex: Sex‐specific body mass ecogeography in wild sifaka populations (Propithecus spp.)

Previous work in primates has shown that body size often covaries with ecological parameters related to resource or energy availability in the environment. This relationship may differ for males and females as access to resources has greater importance for reproductive success in females. We test the hypotheses that (1) female body mass may be more tightly constrained than male body mass by ecological variables, and (2) female body mass may respond more strongly than male body mass to changes in ecological variables (i.e., population‐specific female mass may vary more across an ecological gradient than male mass). Specifically, we investigate the relationship between climatic variables and sex‐specific body mass in Propithecus, a genus in which species‐specific body mass has already been demonstrated to covary significantly with climatic variables. Data from 733 wild sifakas are used to identify sex‐specific body mass for 27 populations representing all nine described sifaka species, and climatic data for each population are derived from the WorldClim database. We use phylogenetic generalized least squares models to demonstrate that body mass in both sexes is significantly correlated with annual rainfall and number of dry months. Furthermore, coefficients of determination are always higher for female models, and coefficients for each climatic variable are higher for females in all significant models. These results support the two hypotheses tested, indicating that ecological forces can have a greater impact on female mass than on male mass in primates. Am J Phys Anthropol 151:77–87, 2013. © 2013 Wiley Periodicals, Inc.     

Statistical multi‐path exposure method for assessing the whole‐body SAR in a heterogeneous human body model in a realistic environment

Assessing the whole‐body absorption in a human in a realistic environment requires a statistical approach covering all possible exposure situations. This article describes the development of a statistical multi‐path exposure method for heterogeneous realistic human body models. The method is applied for the 6‐year‐old Virtual Family boy (VFB) exposed to the GSM downlink at 950 MHz. It is shown that the whole‐body SAR does not differ significantly over the different environments at an operating frequency of 950 MHz. Furthermore, the whole‐body SAR in the VFB for multi‐path exposure exceeds the whole‐body SAR for worst‐case single‐incident plane wave exposure by 3.6%. Moreover, the ICNIRP reference levels are not conservative with the basic restrictions in 0.3% of the exposure samples for the VFB at the GSM downlink of 950 MHz. The homogeneous spheroid with the dielectric properties of the head suggested by the IEC underestimates the absorption compared to realistic human body models. Moreover, the variation in the whole‐body SAR for realistic human body models is larger than for homogeneous spheroid models. This is mainly due to the heterogeneity of the tissues and the irregular shape of the realistic human body model compared to homogeneous spheroid human body models. Bioelectromagnetics 34:240–251, 2013. © 2012 Wiley Periodicals, Inc.     

Effects of geolocation archival tags on reproduction and adult body mass of sooty shearwaters (Puffinus griseus)

Abstract

We attached 11 g (1.4% body‐mass equivalent) global location sensing (GLS) archival tag packages to tarsi of 25 breeding sooty shearwaters (Puffinus griseus, titi) on Whenua Hou (Codfish Island), New Zealand during the chick‐rearing period in 2005. Compared with chicks reared by non‐handled adults that did not carry tags, deployment of tags on one or both adult parents ultimately resulted in 35% reduction in chick body mass and significantly reduced chick skeletal size preceding fledging (19 April). However, body mass between chick groups was not significantly different after controlling for skeletal size. Effects on chicks were more pronounced in six pairs where both parents carried tags. Chick mass was negatively related to the duration that adults carried tags. In this study, none of the chicks reared by pairs where both parents were tagged, 54% of chicks reared by pairs where one parent was tagged, and 83% of chicks reared by non‐handled and non‐tagged parents achieved a previously determined pre‐fiedging mass threshold (564 g; Sagar & Horning 1998). Body mass of adults carrying tags and returning from trans‐equatorial migration the following year were 4% lighter on average than non‐tagged birds, but this difference was not statistically significant. Reduced mass among chicks reared by adults carrying tags during the chick‐provisioning period indicated that adults altered “normal” provisioning behaviours to maintain their own body condition at the expense of their chicks. Population‐level information derived from telemetry studies can reveal important habitat‐linked behaviours, unique aspects of sea‐bird foraging behaviours, and migration ecology. Information for some species (e.g., overlap with fisheries) can aid conservation and marine ecosystem management. We advise caution, however, when interpreting certain data related to adult provisioning behaviours (e.g., time spent foraging, provisioning rates, etc.). If effects on individuals are of concern, we suggest shorter‐term deployments, smaller and lighter tags, and alternative attachment techniques, especially when investigating threatened or endangered species.     

MODULARITY AND SCALING IN FAST MOVEMENTS: POWER AMPLIFICATION IN MANTIS SHRIMP

Extremely fast animal actions are accomplished with mechanisms that reduce the duration of movement. This process is known as power amplification. Although many studies have examined the morphology and performance of power‐amplified systems, little is known about their development and evolution. Here, we examine scaling and modularity in the powerful predatory appendages of a mantis shrimp, Gonodactylaceus falcatus (Crustacea, Stomatopoda). We propose that power‐amplified systems can be divided into three units: an engine (e.g., muscle), an amplifier (e.g., spring), and a tool (e.g., hammer). We tested whether these units are developmentally independent using geometric morphometric techniques that quantitatively compare shapes. Additionally, we tested whether shape and several mechanical features are correlated with size and sex. We found that the morphological regions that represent the engine, amplifier, and tool belong to independent developmental modules. In both sexes, body size was positively correlated with the size of each region. Shape, however, changed allometrically with appendage size only in the amplifier (both sexes) and tool (males). These morphological changes were correlated with strike force and spring force (amplifier), but not spring stiffness (amplifier). Overall, the results indicate that each functional unit belongs to different developmental modules in a power‐amplified system, potentially allowing independent evolution of the engine, amplifier, and tool.     

An exploration of adult body shape and limb proportions at Kellis 2, Dakhleh Oasis,Egypt

Several studies have shown that the human body generally conforms to the ecogeographical expectations of Bergmann's and Allen's rules; however, recent evidence suggests that these expectations may not hold completely for some populations. Egypt is located at the crossroads of Sub‐Saharan Africa, Southern Europe, and the Near East, and gene flow among groups in these regions may confound ecogeographical patterning. In this study, we test the fit of the adult physique of a large sample (N = 163) of females and males from the Kellis 2 cemetery (Dakhleh Oasis, Egypt) against ecogeographical predictions. Body shape (i.e., body mass relative to stature) was assessed by the femur head diameter to bicondylar femur length index (FHD/BFL), and brachial and crural indices were calculated to examine intralimb proportions. Body shape in the Kellis 2 sample is not significantly different from high‐latitude groups and a Lower Nubian sample, and intralimb proportions are not significantly different from mid‐latitude and other low‐latitude groups. This study demonstrates the potential uniqueness of body shape and intralimb proportions in an ancient Egyptian sample, and further highlights the complex relationship between ecogeographic patterning and adaptation. Am J Phys Anthropol 153:496–505, 2014. © 2013 Wiley Periodicals, Inc.     

Craniodental body mass estimators in the dwarf bushbaby (Galagoides)

This study reports data on 17 craniodental body mass estimators in a sample (n = 38) of dwarf galagos (Galagoides). Correlation coefficients (r) range from a high of 0.64 for bizygomatic breadth and body mass to a low of 0.10 for M(3) length and body mass. Of the 17 variables studied, 7 exhibit significant (P < 0.05) correlation coefficients, with 5 of the 7 being multitooth (i.e., tooth row) or cranial variables. In contrast to the correlation coefficients of greater than 0.90 (e.g., Martin [1980] Z Morphol Anthropol 71:115-124; Steudel [1981] Int J Primatol 2:81-90; Gingerich et al. [1982] Am J Phys Anthropol 58:81-100; Conroy [1987] Int J Primatol 8:115-137) published for higher taxonomic level analyses (i.e., all-primate or prosimian) for many of the same variables studied here, the current data indicate weaker relationships when analyzed at the generic level. Possible explanations for the contrast in correlation coefficients between the current and many previous studies include the following: 1) individual variation due to a geographically dispersed sample, 2) individual body mass fluctuations due to seasonal food availability, and 3) individual variation within the sample due to variation in life-history parameters. Because the overall size range of the individuals in a specific or generic level analysis is smaller than that in an ordinal or subordinal sample, the individual variation normally masked when using species means represents a larger proportion of the total variation in a more limited sample. This may then be a cause of these weaker correlations.     

An ecological alternative to Snodgrass & Vanderwart: 360 high quality colour images with norms for seven psycholinguistic variables

This work presents a new set of 360 high quality colour images belonging to 23 semantic subcategories. Two hundred and thirty-six Spanish speakers named the items and also provided data from seven relevant psycholinguistic variables: age of acquisition, familiarity, manipulability, name agreement, typicality and visual complexity. Furthermore, we also present lexical frequency data derived from Internet search hits. Apart from the high number of variables evaluated, knowing that it affects the processing of stimuli, this new set presents important advantages over other similar image corpi: (a) this corpus presents a broad number of subcategories and images; for example, this will permit researchers to select stimuli of appropriate difficulty as required, (e.g., to deal with problems derived from ceiling effects); (b) the fact of using coloured stimuli provides a more realistic, ecologically-valid, representation of real life objects. In sum, this set of stimuli provides a useful tool for research on visual object- and word-processing, both in neurological patients and in healthy controls.     

Anthropometric variables accurately predict dual energy x-ray absorptiometric-derived body composition and can be used to screen for diabetes

The current world-wide epidemic of obesity has stimulated interest in developing simple screening methods to identify individuals with undiagnosed diabetes mellitus type 2 (DM2) or metabolic syndrome (MS). Prior work utilizing body composition obtained by sophisticated technology has shown that the ratio of abdominal fat to total fat is a good predictor for DM2 or MS. The goals of this study were to determine how well simple anthropometric variables predict the fat mass distribution as determined by dual energy x-ray absorptometry (DXA), and whether these are useful to screen for DM2 or MS within a population. To accomplish this, the body composition of 341 females spanning a wide range of body mass indices and with a 23% prevalence of DM2 and MS was determined using DXA. Stepwise linear regression models incorporating age, weight, height, waistline, and hipline predicted DXA body composition (i.e., fat mass, trunk fat, fat free mass, and total mass) with good accuracy. Using body composition as independent variables, nominal logistic regression was then performed to estimate the probability of DM2. The results show good discrimination with the receiver operating characteristic (ROC) having an area under the curve (AUC) of 0.78. The anthropometrically-derived body composition equations derived from the full DXA study group were then applied to a group of 1153 female patients selected from a general endocrinology practice. Similar to the smaller study group, the ROC from logistical regression using body composition had an AUC of 0.81 for the detection of DM2. These results are superior to screening based on questionnaires and compare favorably with published data derived from invasive testing, e.g., hemoglobin A1c. This anthropometric approach offers promise for the development of simple, inexpensive, non-invasive screening to identify individuals with metabolic dysfunction within large populations.     

Relationship between body mass, brain mass and craniometric parameters in the miniature pig Mini-Lewe

The relations between skull measurements, brain mass, and body mass were investigated in 30 female miniature pigs, being 6 month old. The relatively low correlation coefficients between the variables indicate a high variability in skull shape. We found an allometric exponent of 0.236 for the relation between brain and body mass with a coefficient of determination of 0.29. Both measurements show a highest correlation with the arcus zygomaticus width, which shows close relations with the occipital height and condylobasal length.     

Spontaneous quantity discrimination in crickets

Recent studies have reported that the ability to discriminate among quantities is not a prerogative of vertebrates. Ants, bees, and spiders can solve tasks in which they are required to discriminate between groups of objects. Although many studies regarding numerical cognition on invertebrates proposed a proto‐counting system, more control experiments for non‐numerical variables are necessary to confirm this hypothesis. Here, we developed a new method to investigate quantity discrimination abilities in invertebrates. We investigated the spontaneous choice of a cricket, Acheta domesticus. We exploited its natural shelter‐seeking behavior by presenting sets of geometrical shapes that simulated potential shelters. In a dichotomous choice between sets of geometrical black shapes differing in number of items, the majority of crickets chose the set containing the larger numerosity up to 2 versus 3 items. Control experiments suggested that crickets discriminated between sets consisting of different numbers of items by attending to continuous variables (i.e., convex hull and cumulative surface area) rather than by attending to numerosity. Secondly, when discriminating between single geometrical shapes, crickets attend to the width but not to the height of the stimuli.     

Feeding ecology has a stronger evolutionary influence on functional morphology than on body mass in mammals

Ecological specialization is a central driver of adaptive evolution. However, selective pressures may uniquely affect different ecomorphological traits (e.g., size and shape), complicating efforts to investigate the role of ecology in generating phenotypic diversity. Comparative studies can help remedy this issue by identifying specific relationships between ecologies and morphologies, thus elucidating functionally relevant traits. Jaw shape is a dietary correlate that offers considerable insight on mammalian evolution, but few studies have examined the influence of diet on jaw morphology across mammals. To this end, I apply phylogenetic comparative methods to mandibular measurements and dietary data for a diverse sample of mammals. Especially powerful predictors of diet are metrics that capture either the size of the angular process, which increases with greater herbivory, or the length of the posterior portion of the jaw, which decreases with greater herbivory. The size of the angular process likely reflects sizes of attached muscles that produce jaw movements needed to grind plant material. Further, I examine the impact of feeding ecology on body mass, an oft-used ecological surrogate in macroevolutionary studies. Although body mass commonly increases with evolutionary shifts to herbivory, it is outperformed by functional jaw morphology as a predictor of diet. Body mass is influenced by numerous factors beyond diet, and it may be evolutionarily labile relative to functional morphologies. This suggests that ecological diversification events may initially facilitate body mass diversification at smaller taxonomic and temporal scales, but sustained selective pressures will subsequently drive greater trait partitioning in functional morphologies.     

Morphological adaptations to marine life in snakes

We investigated morphological adaptations to aquatic life within animals that exhibit a structurally simple, elongate body form, i.e., snakes. This linear body plan should impose different biomechanical constraints than the classical streamlined body shape associated with propulsion by fins, feet, or wings. Our measurements of general body shape of terrestrial, amphibious, and marine snakes (all from the same phylogenetic lineage, the Elapidae) show that seasnakes display specialized morphological attributes for life in water. Most notably, the cross‐sectional body shape is circular in terrestrial snakes but dorso‐ventrally elongated in seasnakes (due to a prominent ventral keel); amphibious species (sea kraits) exhibit an intermediate shape. The tail of amphibious and marine species (a major propulsive structure during swimming) is higher and thinner than in terrestrial snakes (i.e., paddle‐shaped) but shorter relative to body length. The evolution of a laterally compressed shape has been achieved by an increase in body height rather than a decrease in body width, possibly reflecting selection for more effective propulsive thrust, and for an ability to maintain hydrodynamic efficiency despite the minor bodily distension inevitably caused by prey items and developing offspring. J. Morphol., 2011. © 2011 Wiley‐Liss, Inc     

Gender differences in predictors of body weight and body weight change in healthy adults

Background: Overweight and obesity are important predictors of a wide variety of health problems. Analysis of naturally occurring changes in body weight can provide valuable insights in improving our understanding of the influence of demographic, lifestyle, and psychosocial factors on weight gain in middle‐age adults. Objective: To identify gender‐specific predictors of body weight using cross‐sectional and longitudinal analyses. Methods and Procedures: Anthropometric, lifestyle and psychosocial factors were measured at baseline and then quarterly for 1 year in 572 healthy adult volunteers from Central Massachusetts who were recruited between 1994 and 1998. Linear mixed models were used to analyze the relationship between body weight and potential predictors, including demographic (e.g., age, educational level), lifestyle (e.g., diet, physical activity, smoking), and psychosocial (e.g., anxiety, depression) factors. Results: Over the 1‐year study period, on average, men gained 0.3 kg and women lost 0.2 kg. Predictors of lower body weight at baseline in both men and women included current cigarette smoking, greater leisure‐time physical activity, and lower depression and anxiety scores. Lower body weights were associated with a lower percentage of caloric intake from protein and greater occupational physical activity levels only among men; and with higher education level only among women. Longitudinal predictors of 1‐year weight gain among women included increased total caloric intake and decreased leisure‐time physical activity, and among men, greater anxiety scores. Discussion: Demographic, lifestyle and psychosocial factors are independently related to naturally occurring changes in body weight and have marked differential gender effects. These effects should be taken into consideration when designing interventions for weight‐loss and maintenance at the individual and population levels.     

Collateral fattening: When a deficit in lean body mass drives overeating

In his last review entitled “Some Adventures in Body Composition,” Gilbert Forbes reminded us that “lean body mass and body fat are in a sense companions.” To what extent the lean body mass (or fat‐free mass) component in this companionship impacts on energy intake is rarely a topic for discussion, amid a dominant adipocentric view of appetite control. Yet an analysis of the few human studies that have investigated the relationships between objectively measured food intake and body composition reveals a potentially important role for both an increase and a decrease in fat‐free mass in the drive to eat. These studies are highlighted here, together with the implications of their findings for research directed as much toward the elucidation of peripheral signals and energy‐sensing mechanisms that drive hunger and appetite, as toward understanding the mechanisms by which dieting and sedentariness predispose to fatness.     

Ancient and contingent body shape diversification in a hyperdiverse continental fish radiation

The characiform fishes of the Neotropics and Africa radiated remarkably in ecomorphology, but the macroevolutionary processes responsible for their biodiversity remain unexplored, and the degree to which their continental diversification parallels classic adaptive radiations remains untested. We reconstruct their diversification using a new fossil‐calibrated molecular phylogeny, dietary information, and geometric morphometrics. Though body shape diversified early in a manner consistent with an ancient continental adaptive radiation, trophic shifts did not always coincide with shape changes. With the notable exception of piscivores, lineages that converged in diet did not converge closely in body shape. Shifts in habitat or other variables likely influenced body shape evolution in addition to changes in diet, and the clade's history departs from many classic adaptive radiations in lakes or on islands, in which trophic convergence drives morphological convergence. The contrast between the Neotropical radiation's exhaustive exploration of morphospace and the more restrained diversification in Africa suggests a major role for contingency in characiform evolution, with the presence of cypriniform competitors in the Old World, but not the New, providing one possible explanation. Our results depict the clearest ecomorphological reconstruction to date for Characiformes and set the stage for studies further elucidating the processes underlying its diversification.     

Cranial variables as predictors of hominine body mass

Body mass is a key variable in investigating the evolutionary biology of the hominines (Australopithecus, Paranthropus, and Homo). It is not only closely related to life-history parameters but also provides a necessary baseline for studies of encephalization or megadonty. Body mass estimates are normally based on the postcranial skeleton. However, the majority of hominid fossils are cranio-dental remains that are unassociated with postcranial material. Only rarely can postcranial material be linked with craniodentally defined hominid taxa. This study responds to this problem by evaluating body mass estimates based on 15 cranial variables to determine whether they compare in reliability with estimates determined from postcranial variables. Results establish that some cranial variables, and particularly orbital area, orbital height, and biporionic breadth, are nearly as good mass predictors for hominoids as are some of the best postcranial predictors. For the hominines in particular, orbital height is the cranial variable which produces body mass estimates that are most in line with postcranially generated estimates. Both orbital area and biporionic breadth scale differently in the hominines than they do in the other hominoids. This difference in scaling results in unusually large estimates of body mass based on these variables for the larger-sized hominines, although the three cranial variables produce equivalent predicted masses for the smaller-bodied hominines. © 1994 Wiley-Liss, Inc.     

Adaptive,but not condition‐dependent,body shape differences contribute to assortative mating preferences during ecological speciation

Assortative mating is critical for reproductive isolation during speciation; however, the mechanisms underlying mating preferences are often unknown. Assortative mating can be mediated through preferences for condition‐dependent and adaptive (“magic”) traits, but rigorously testing these hypotheses has been impeded by trait covariation in living organisms. We used computer‐generated models to examine the role of body shape in producing association preferences between fish populations undergoing ecological speciation in different habitat types. We demonstrate that body shape can serve as an adaptive trait (variation in head size between populations) and a condition‐dependent signal (variation in abdominal distention among individuals). Female preferences for stimuli varying in only one aspect of body shape uncovered evidence for body shape as a magic trait across population pairs, but no evidence for body shape serving as a condition‐dependent signal. Evolution of preferences only in females from one habitat type as well as stronger preferences in sympatric nonsulfidic as opposed to allopatric nonsulfidic populations suggests that reinforcement may have played a role in producing the observed patterns.     

Climatic influences on human body size and proportions: Ecological adaptations and secular trends

This study reevaluates the long-standing observation that human morphology varies with climate. Data on body mass, the body mass index [BMI; mass (kg)/stature (m)²], the surface area/body mass ratio, and relative sitting height (RSH; sitting height/stature) were obtained for 223 male samples and 195 female samples derived from studies published since D.F. Roberts' landmark paper “Body weight, race, and climate” in 1953 (Am. J. Phys. Anthropol. 11:533–558). Current analyses indicate that body mass varies inversely with mean annual temperature in males (r = −0.27, P < 0.001) and females (r = −0.28, P < 0.001), as does the BMI (males: r = −0.22, P = 0.001; females: r = −0.30, P < 0.001). The surface area/body mass ratio is positively correlated with temperature in both sexes (males: r = 0.29, P < 0.001; females: r = 0.34, P < 0.001), whereas the relationship between RSH and temperature is negative (males: r = −0.37, P < 0.001; females: r = −0.46, P < 0.001). These results are consistent with previous work showing that humans follow the ecological rules of Bergmann and Allen. However, the slope of the best-fit regressions between measures of body mass (i.e., mass, BMI, and surface area/mass) and temperature are more modest than those presented by Roberts. These differences appear to be attributable to secular trends in mass, particularly among tropical populations. Body mass and the BMI have increased over the last 40 years, whereas the surface area/body mass ratio has decreased. These findings indicate that, although climatic factors continue to be significant correlates of world-wide variation in human body size and morphology, differential changes in nutrition among tropical, developing world populations have moderated their influence. Am J Phys Anthropol 106:483–503, 1998. © 1998 Wiley-Liss, Inc.     

Predictors of body shape among populations of a stream fish (Cyprinella venusta,Cypriniformes: Cyprinidae)

Performance‐related variation in fitness can manifest as morphological responses to ecological and evolutionary pressures. Eco‐morphological studies often utilize stark binary comparisons, such as lentic to lotic populations of freshwater fishes, to characterize relationships between form and function despite possible complications from confounding factors. In the present study, we compared body shape variation among lotic populations of a stream fish (Cyprinella venusta Girard) to disentangle the influence of ecological and evolutionary drivers of phenotypic change. We assessed the extent to which body shape corresponded to three key environmental factors (mean channel velocity, mean discharge, and mean annual run‐off), phylogeny (mitochondrial DNA divergence), and body size (centroid size). We also examined relationships between these parameters and a fineness index, which is a measure of streamlining and morphological optimization for steady swimming performance. All three environmental variables had some explanatory power, although morphological characteristics were predominantly associated with variation in mean annual run‐off. Phylogeny was also a strong predictor of morphological variation, whereas body size had little predictive power. Populations experiencing higher mean annual run‐off exhibited a shorter base of the dorsal fin, a more slender body and caudal peduncle, a smaller head in both horizontal and vertical dimensions, and a more anterior placement of the eye. With some exceptions, such as variation in jaw length, differences in body shape associated with phylogenetic history were similar to those associated with run‐off. Notably, all clades exhibited parallel responses to variation in run‐off. Populations experiencing high mean annual run‐off approached a hydrodynamic optimum, suggesting a morphology optimized for steady swimming performance. In contrast to previous studies that emphasize the importance of average water velocity, the findings of the present study indicate that morphological variation among populations of stream fishes is tightly linked to more complex aspects of hydrology and evolutionary history. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, ●● , ●●–●●.