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Body Form (body + form)
Selected AbstractsPlesiomorphic Escape Decisions in Cryptic Horned Lizards (Phrynosoma) Having Highly Derived Antipredatory DefensesETHOLOGY, Issue 10 2010William E. Cooper Jr Escape theory predicts that the probability of fleeing and flight initiation distance (predator,prey distance when escape begins) increase as predation risk increases and decrease as escape cost increases. These factors may apply even to highly cryptic species that sometimes must flee. Horned lizards (Phrynosoma) rely on crypsis because of coloration, flattened body form, and lateral fringe scales that reduce detectability. At close range they sometimes squirt blood-containing noxious substances and defend themselves with cranial spines. These antipredatory traits are highly derived, but little is known about the escape behavior of horned lizards. Of particular interest is whether their escape decisions bear the same relationships to predation risk and opportunity costs of escaping as in typical prey lacking such derived defenses. We investigated the effects of repeated attack and direction of predator turning on P. cornutum and of opportunity cost of fleeing during a social encounter in P. modestum. Flight initiation distance was greater for the second of two successive approaches and probability of fleeing decreased as distance between the turning predator and prey increased, but was greater when the predator turned toward than away from a lizard. Flight initiation distance was shorter during social encounters than when lizards were solitary. For all variables studied, risk assessment by horned lizards conforms to the predictions of escape theory and is similar to that in other prey despite their specialized defenses. Our findings show that these specialized, derived defenses coexist with a taxonomically widespread, plesiomorphic method of making escape decisions. They suggest that escape theory based on costs and benefits, as intended, applies very generally, even to highly cryptic prey that have specialized defense mechanisms. [source] REPLICATED EVOLUTION OF INTEGRATED PLASTIC RESPONSES DURING EARLY ADAPTIVE DIVERGENCEEVOLUTION, Issue 4 2006Kevin J. Parsons Abstract Colonization of a novel environment is expected to result in adaptive divergence from the ancestral population when selection favors a new phenotypic optimum. Local adaptation in the new environment occurs through the accumulation and integration of character states that positively affect fitness. The role played by plastic traits in adaptation to a novel environment has generally been ignored, except for variable environments. We propose that if conditions in a relatively stable but novel environment induce phenotypically plastic responses in many traits, and if genetic variation exists in the form of those responses, then selection may initially favor the accumulation and integration of functionally useful plastic responses. Early divergence between ancestral and colonist forms will then occur with respect to their plastic responses across the gradient bounded by ancestral and novel environmental conditions. To test this, we compared the magnitude, integration, and pattern of plastic character responses in external body form induced by shallow versus open water conditions between two sunfish ecomorphs that coexist in four postglacial lakes. The novel sunfish ecomorph is present in the deeper open water habitat, whereas the ancestral ecomorph inhabits the shallow waters along the lake margin. Plastic responses by open water ecomorphs were more correlated than those of their local shallow water ecomorph in two of the populations, whereas equal levels of correlated plastic character responses occurred between ecomorphs in the other two populations. Small but persistent differences occurred between ecomorph pairs in the pattern of their character responses, suggesting a recent divergence. Open water ecomorphs shared some similarities in the covariance among plastic responses to rearing environment. Replication in the form of correlated plastic responses among populations of open water ecomorphs suggests that plastic character states may evolve under selection. Variation between ecomorphs and among lake populations in the covariance of plastic responses suggests the presence of genetic variation in plastic character responses. In three populations, open water ecomorphs also exhibited larger plastic responses to the environmental gradient than the local shallow water ecomorph. This could account for the greater integration of plastic responses in open water ecomorphs in two of the populations. This suggests that the plastic responses of local sunfish ecomorphs can diverge through changes in the magnitude and coordination of plastic responses. Although these results require further investigation, they suggest that early adaptive evolution in a novel environment can include changes to plastic character states. The genetic assimilation of coordinated plastic responses could result in the further, and possibly rapid, divergence of such populations and could also account for the evolution of genes of major effect that contribute to suites of phenotypic differences between divergent populations. [source] WHY DOES A TRAIT EVOLVE MULTIPLE TIMES WITHIN A CLADE?EVOLUTION, Issue 1 2006REPEATED EVOLUTION OF SNAKELINE BODY FORM IN SQUAMATE REPTILES Abstract Why does a trait evolve repeatedly within a clade? When examining the evolution of a trait, evolutionary biologists typically focus on the selective advantages it may confer and the genetic and developmental mechanisms that allow it to vary. Although these factors may be necessary to explain why a trait evolves in a particular instance, they may not be sufficient to explain phylogenetic patterns of repeated evolution or conservatism. Instead, other factors may also be important, such as biogeography and competitive interactions. In squamate reptiles (lizards and snakes) a dramatic transition in body form has occurred repeatedly, from a fully limbed, lizardlike body form to a limbreduced, elongate, snakelike body form. We analyze this trait in a phylogenetic and biogeographic context to address why this transition occurred so frequently. We included 261 species for which morphometric data and molecular phylogenetic information were available. Among the included species, snakelike body form has evolved about 25 times. Most lineages of snakelike squamates belong to one of two ecomorphs, either short-tailed burrowers or long-tailed surface dwellers. The repeated origins of snakelike squamates appear to be associated with the in situ evolution of these two ecomorphs on different continental regions (including multiple origins of the burrowing morph within most continents), with very little dispersal of most limb-reduced lineages between continental regions. Overall, the number of repeated origins of snakelike morphology seems to depend on large-scale biogeographic patterns and community ecology, in addition to more traditional explanations (e.g., selection, development). [source] Does pregnancy affect swimming performance of female Mosquitofish, Gambusia affinis?FUNCTIONAL ECOLOGY, Issue 3 2002I. Plaut Summary 1.,The cost of reproduction due to limiting of the reproductive female's locomotion capability has been suggested many times, but has rarely been directly examined, especially in fishes. Here, the effect of pregnancy on swimming performance in the viviparous Mosquitofish, Gambusia affinis, was studied. 2.,Eight females of G. affinis were isolated, each in a separate aquarium, and critical swimming speed (Ucrit), body mass (BM) and cross-section area were measured every 5 days from the beginning of the pregnancy until 2,4 days after parturition. 3.,Swimming kinematics (tail beat frequency and amplitude) was measured in non-pregnant and pregnant females at different swimming speeds. 4.,BM increased during pregnancy from 0·47 ± 0·13 g to 0·72 ± 0·19 g, and the cross-section area also increased during pregnancy from 0·21 ± 0·06 cm2 to 0·32 ± 0·07 cm2. Ucrit decreased from 25·0 ± 1·3 cm s,1 before pregnancy to 20·1 ± 1·5 cm s,1 just before parturition, and returned to 24·7 ± 1·4 cm s,1 2,4 days after parturition. Interindividual variation was repeatable and reflects real differences among individuals. 5.,Swimming kinematics was not affected by pregnancy. 6.,The results suggest that reductions in Ucrit are probably because of aerobic constraints and not necessarily due to hydrodynamic changes resulting from changing in body form or plasticity. Moreover, the reduction in Ucrit is, potentially, a ,cost of reproduction' owing to decrease in the ability to gain food during pregnancy in G. affinis females. [source] Assessing the taxonomic status of dingoes Canis familiaris dingo for conservationMAMMAL REVIEW, Issue 2 2006AMANDA E. ELLEDGE ABSTRACT 1The conservation status of the dingo Canis familiaris dingo is threatened by hybridization with the domestic dog C. familiaris familiaris. A practical method that can estimate the different levels of hybridization in the field is urgently required so that animals below a specific threshold of dingo ancestry (e.g. 1/4 or 1/2 dingoes) can reliably be identified and removed from dingo populations. 2Skull morphology has been traditionally used to assess dingo purity, but this method does not discriminate between the different levels of dingo ancestry in hybrids. Furthermore, measurements can only be reliably taken from the skulls of dead animals. 3Methods based on the analysis of variation in DNA are able to discriminate between the different levels of hybridization, but the validity of this method has been questioned because the materials currently used as a reference for dingoes are from captive animals of unproven genetic purity. The use of pre-European materials would improve the accuracy of this method, but suitable material has not been found in sufficient quantity to develop a reliable reference population. Furthermore, current methods based on DNA are impractical for the field-based discrimination of hybrids because samples require laboratory analysis. 4Coat colour has also been used to estimate the extent of hybridization and is possibly the most practical method to apply in the field. However, this method may not be as powerful as genetic or morphological analyses because some hybrids (e.g. Australian cattle dog × dingo) are similar to dingoes in coat colour and body form. This problem may be alleviated by using additional visual characteristics such as the presence/absence of ticking and white markings. [source] FEEDING PREFERENCES OF THE MONKEY MIA DOLPHINS: RESULTS FROM A SIMULTANEOUS CHOICE PROTOCOLMARINE MAMMAL SCIENCE, Issue 4 2003Lawrence M. Dill Abstract The semiwild beach-feeding bottlenose dolphins (Tursiops aduncus) of Monkey Mia, Western Australia, provide an unparalleled opportunity to examine prey preference of this species. In a series of binary-choice feeding experiments, we took advantage of the animals' willingness to be fed by hand, to explore their preferences for fish species, size, and state (freshly caught or previously frozen). At the end of each beach visit, each dolphin was provided with a pair of fish but allowed to eat only the first one chosen. The dolphins appeared indifferent among the three species of fish offered to them (yellowtail trumpeter, Amniataba caudovittatus; striped trumpeter, Pelates sexlineatus; and western butterfish, Pentapodus vitta), which were of similar body form and matched for mass. Overall, the dolphins showed a slight preference for the larger of two yellowtail trumpeter offered, suggesting the capability for rational choice when there was a basis for it (most likely energy in this case), although there was considerable individual variation. The dolphins did not distinguish between freshly caught and previously frozen yellowtail. The methodology we describe can be used to generate data of potential value for understanding food and habitat selection of wild dolphins, and for modifying management practices for semiwild dolphins at Monkey Mia and elsewhere. [source] Body proportions of circumpolar peoples as evidenced from skeletal data: Ipiutak and Tigara (Point Hope) versus Kodiak Island InuitAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 2 2010Trenton W. Holliday Abstract Given the well-documented fact that human body proportions covary with climate (presumably due to the action of selection), one would expect that the Ipiutak and Tigara Inuit samples from Point Hope, Alaska, would be characterized by an extremely cold-adapted body shape. Comparison of the Point Hope Inuit samples to a large (n > 900) sample of European and European-derived, African and African-derived, and Native American skeletons (including Koniag Inuit from Kodiak Island, Alaska) confirms that the Point Hope Inuit evince a cold-adapted body form, but analyses also reveal some unexpected results. For example, one might suspect that the Point Hope samples would show a more cold-adapted body form than the Koniag, given their more extreme environment, but this is not the case. Additionally, univariate analyses seldom show the Inuit samples to be more cold-adapted in body shape than Europeans, and multivariate cluster analyses that include a myriad of body shape variables such as femoral head diameter, bi-iliac breadth, and limb segment lengths fail to effectively separate the Inuit samples from Europeans. In fact, in terms of body shape, the European and the Inuit samples tend to be cold-adapted and tend to be separated in multivariate space from the more tropically adapted Africans, especially those groups from south of the Sahara. Am J Phys Anthropol, 2010. © 2009 Wiley-Liss, Inc. [source] Using form analysis techniques to improve photogrammetric mass-estimation methodsMARINE MAMMAL SCIENCE, Issue 1 2008Kelly M. Proffitt Abstract Numerical characterization of animal body forms using elliptical Fourier decomposition may be a useful analytic technique in a variety of marine mammal investigations. Using data collected from the Weddell seal (Leptonychotes weddellii), we describe the method of body form characterization using elliptical Fourier analysis and demonstrated usefulness of the technique in photogrammetric mass-estimation modeling. We compared photogrammetric mass-estimation models developed from (1) standard morphometric measurement covariates, (2) elliptical Fourier coefficient covariates, and (3) a combination of morphometric and Fourier coefficient covariates and found that mass-estimation models employing a combination of morphometric measurements and Fourier coefficients outperformed models containing only one covariate type. Inclusion of Fourier coefficients in photogrammetric mass-estimation models employing standard morphometric measurements reduced the width of the prediction interval by 24.4%. Increased precision of photogrammetric mass-estimation models employing Fourier coefficients as model covariates may expand the range of ecological questions that can be addressed with estimated mass measurements. [source] | ||||||||||