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1.
A central issue in evolutionary biology concerns whether morphology, performance and habitat use have coevolved. We investigated evolutionary relationships among the size of the subdigital toepad, clinging ability and perch height in 12 species of Caribbean Anolis lizard. Specifically, we predicted that: (1) because larger anole species tend to perch high in the canopy, both toepad area and clinging ability should scale with positive allometry to enable small and large lizards to possess approximately similar ratios of both variables relative to mass; (2) anole species with relatively larger toepads (i.e. size-adjusted) should be relatively better clingers compared with species with relatively small toepads; (3) species that perch high in the canopy should possess relatively large clinging abilities (either on an absolute or a size-adjusted basis). Our first hypothesis was refuted, as both toepad area and clinging ability scaled close to isometry (0.67) relative to mass, indicating that large lizard species have low ratios of clinging ability to mass compared with small lizard species. However, our second and third predictions were confirmed. Anole species with relatively larger toepads were relatively better clingers compared with species with relatively smaller toepads. Anole species that perched high in the canopy (either on an absolute scale or relative to size) tended to have relatively larger toepads and greater clinging capacities compared with species that perched lower in the canopy. These data provide indirect comparative evidence that the evolution of increased toepad size in some anole species is adaptive, by facilitating the occupation of perches high in the canopy.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 83 , 389–398.  相似文献   

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3.
One of the central controversies regarding the evolution of adhesion concerns how adhesive force scales as animals change in size, either among or within species. A widely held view is that as animals become larger, the primary mechanism that enables them to climb is increasing pad area. However, prior studies show that much of the variation in maximum adhesive force remains unexplained, even when area is accounted for. We tested the hypothesis that maximum adhesive force among pad-bearing gecko species is not solely dictated by toepad area, but also depends on the ratio of toepad area to gecko adhesive system compliance in the loading direction, where compliance (C) is the change in extension (Δ) relative to a change in force (F) while loading a gecko’s adhesive system (C = dΔ/dF). Geckos are well-known for their ability to climb on a range of vertical and overhanging surfaces, and range in mass from several grams to over 300 grams, yet little is understood of the factors that enable adhesion to scale with body size. We examined the maximum adhesive force of six gecko species that vary in body size (~2–100 g). We also examined changes between juveniles and adults within a single species (Phelsuma grandis). We found that maximum adhesive force and toepad area increased with increasing gecko size, and that as gecko species become larger, their adhesive systems become significantly less compliant. Additionally, our hypothesis was supported, as the best predictor of maximum adhesive force was not toepad area or compliance alone, but the ratio of toepad area to compliance. We verified this result using a synthetic “model gecko” system comprised of synthetic adhesive pads attached to a glass substrate and a synthetic tendon (mechanical spring) of finite stiffness. Our data indicate that increases in toepad area as geckos become larger cannot fully account for increased adhesive abilities, and decreased compliance must be included to explain the scaling of adhesion in animals with dry adhesion systems.  相似文献   

4.
Positive abundance-occupancy relationships (a relationship between the number of sites a species occupies and the average density of individuals in occupied sites) are widespread through a range of taxa. The simplest model for this is the "vital rates" model, which proposes that habitat suitability varies spatially; increasing average habitat quality thus leads to simultaneous increases in average densities within occupied areas, as well as the total area that is habitable. This model has not been tested. We develop a general analytical version of this model and show that it predicts that the skewness of population size or aggregation of individuals within sites should vary systematically with density and occupancy, depending on the distribution of habitat suitability, and that the variance in occupancy should be highest at low densities. We compare these predictions with data from the British Trust for Ornithology's Common Birds Census, and we find systematic changes in both variance and skewness of density, both intra- and interspecifically.  相似文献   

5.
Performance capacity influences ecology, behavior and fitness, and is determined by the underlying phenotype. The phenotype-performance relationship can influence the evolutionary trajectory of an organism. Several types of phenotype-performance relationships have been described, including one-to-one relationships between a single phenotypic trait and performance measure, trade-offs and facilitations between a phenotypic trait and multiple performance measures, and redundancies between multiple phenotypic traits and a single performance measure. The F-matrix is an intraspecific matrix of measures of statistical association between phenotype and performance that is used to quantify these relationships. We extend the F-matrix in two ways. First, we use the F-matrix to describe how the different phenotype-performance relationships occur simultaneously and interact in functional systems, a phenomenon we call many-to-many mapping. Second, we develop methods to compare F-matrices among species and compare phenotype-performance relationships at microevolutionary and macroevolutionary levels. We demonstrate the expanded F-matrix approach with a dataset of eight phrynosomatine lizard species, including six phenotypic traits and two measures of locomotor performance. Our results suggest that all types of relationships occur in this system and that phenotypic traits involved in trade-offs are more functionally constrained and tend evolve slower interspecifically than those involved in facilitations or one-to-one relationships.  相似文献   

6.
SYNOPSIS. This essay presents a method for measuring the degreeto which one biological outline form lies in between two others.The procedure does not measure forms separately, but rathercompares pairs of tensors expressing D'Arcy Thompson's "Cartesiantransformations" according to the biorthogonal formalism ofBookstein. In analogy with conventional methods, betweennessis computed as a similarity score, the cosine of a non- Euclideanangle between the tensors. The new quantities, size-betweennessand shapebetweenness, enable comparisons of form series againsta priori orderings intra- and interspecifically  相似文献   

7.
Scorpion cohabitation was studied qualitatively and quantitatively for several years in the field and in controlled experimental conditions in the laboratory. In the field, several cases were recorded of scorpions sharing the same shelter, either intra- or interspecifically. Intraspecific cohabitation was more prevalent than interspecific cohabitation. Among the five scorpion species studied here, Compsobuthus werneri judaicus shows the highest degree of sociality and aggregates both intra- and interspecifically. Leiurus quinquestriatus was never observed to cohabit interspecifically. Both Buthotus judaicus and C. werneri judaicus shared shelters with other scorpions more frequently during the wet season, whereas Nebo hierichonticus and Scorpio maurus fuscus cohabitated more often during the dry season. Under controlled laboratory conditions, density and availability of either food or shelter appear to be significant in facilitating cohabitation, even in the more aggressive species. Received: April 28, 1999 / Accepted: July 30, 1999  相似文献   

8.
The performance of an organism in its environment frequently depends more on its composite phenotype than on individual phenotypic traits. Thus, understanding environmental adaptation requires investigating patterns of covariation across functionally related traits. The replicated adaptive radiations of Greater Antillean Anolis lizards are characterized by ecological and morphological convergence, thus, providing an opportunity to examine the role of multiple phenotypes in microhabitat adaptation. Here, we examine integrated claw and toepad morphological evolution in relation to habitat partitioning across the adaptive radiations of Greater Antillean anoles. Based on analysis of 428 specimens from 57 species, we found that different aspects of claw morphology were associated with different perch dimensions, with claw height positively associated with perch diameter and claw curvature positively associated with perch height. Patterns of integration also varied across claw and toepad traits, likely driven by correlative selection for performance on smoother and rougher substrates. Finally, rates of evolution differed between claw and toepad traits, with claw length evolving faster than all other traits despite having no predicted functional importance. Our results highlight the multivariate nature of phenotypic adaptation and suggest that phenotypic integration across Greater Antillean anoles is driven by fine‐scale correlative selection based on structural habitat specialization.  相似文献   

9.
《Zoology (Jena, Germany)》2014,117(6):363-369
Exploring the relationship between phenotype and performance in an ecological and evolutionary context is crucial to understanding the adaptive nature of phenotypic traits. Despite their ubiquity in vertebrates, few studies have examined the functional and ecological significance of claw morphologies. Here we examine the adhesive toepad and claw system of Anolis lizards. Claw characters are significantly different between lizards classified as arboreal (perch height  1 m) and non-arboreal (perch height < 1 m). Arboreal species possess significantly higher and longer claws, and show trends toward decreased claw curvature and wider claw tip angles. Toepad size and claw length and height are tightly correlated with each other and with perch height, suggesting that the adhesive toepad and gripping claw have co-evolved to accommodate different habitats. The functional morphology and evolution of claws are ripe areas for future investigation.  相似文献   

10.
Toe pad morphology and mechanisms of sticking in frogs   总被引:4,自引:0,他引:4  
Sticking ability in frogs was measured on a series of different substrates. Analysis of performance suggests that frogs use two sticking mechanisms: interlocking on rough surfaces and capillarity on smooth surfaces. There is a correlation between morphological specializations of the toe pad and sticking ability, but these morphological features are not unique to arboreal species. Terrestrial species that use leaves as resting sites during times of inactivity have many of the same morphological specializations and stick as well as the strictly arboreal species.  相似文献   

11.
Photosynthesis is a main driver of plant performance and varies between and within species. This study investigates the effects of plant functional traits as well as abiotic site conditions on the intra- and interspecific variability of photosynthetic performance measured via maximum carboxylation capacity (Vcmax) in five widespread species (Campanula glomerata, Centaurea jacea, Plantago media, Salvia pratensis and Trifolium montanum) and on 18 dry calcareous grassland sites across Europe. In addition to that we assessed plant traits associated with plant performance like specific leaf area, leaf nitrogen and carbon status and stable nitrogen isotope content in parallel on each individual. Climate variables, site characteristics and soil nutrients were recorded to test whether abiotic conditions had a direct impact on photosynthesis rates, or whether that influence was mitigated by their impact on the leaf functional traits measured. Leaf functional traits and abiotic site conditions had an influence on Vcmax both, within and between species. However, the results differed between these scales with differences between species, where mainly T. montanum responded differently than the other species. Leaf nitrogen content had the strongest link of all parameters analysed to Vcmax and was positively related to it both, intra- and interspecifically. Slope, soil nitrogen, irradiation and temperature influenced Vcmax yet we found that mainly leaf traits had direct effects on Vcmax when we analysed all traits and site conditions together using structural equation models. However, the indirect effects of abiotic site conditions via changing leaf functional traits were strong. We thus conclude that abiotic site conditions change Vcmax mainly via affecting leaf functional traits, thus representing an indirect effect. This effect has to be considered when using abiotic site conditions and leaf functional traits for forecasting and measuring photosynthesis.  相似文献   

12.
Understanding the evolution of complex functional traits is a challenge for evolutionary physiology. Here we investigate the evolution of subdigital toepads in lizards, which have arisen independently at least three times, although with subtle anatomical differences. Some designs (anole, gecko) appear functionally equivalent, whereas other designs (skink) are inferior. The functional equivalence of geckos and anoles highlights the creative aspect of the evolutionary process in that these two groups have arrived at the same functional endpoint along very different trajectories. However, this functional equivalence does not result in equivalence for performance at whole-organism tasks (e.g., running uphill), as the evolution of behavior (e.g., toe-furling) has enabled geckos to be superior climbers than anoles. We also show that adaptive increases in the toepad size within a closely related lizard genus (Anolis) has resulted in concomitant evolution of enhanced clinging ability and increased perch heights. A third insight is that pad-bearing geckos are capable of carrying tremendous loads (up to 250% of body weight) up smooth surfaces, and that the toepad itself does not appear limiting. This comparative and whole-organism approach to lizard toepads underscores how organisms can evolve multiple solutions to evolutionary problems.  相似文献   

13.
This study examines the relationship between feeding strategy and the evolutionary radiation of three genera of broadly sympatric cricetid rodents (Phyllotis, Akodon, Calomys) found in the Andes of southern Peru. Stomach contents from 13 species reveal that although food habits are variable, both intra- and interspecifically, there are two general feeding strategies: diurnal insectivory and nocturnal herbivory-omnivory. Intraspecific variation in diet was sometimes correlated with altitude. Patterns which might suggest competitive exclusion or ecological release were generally not observed. Interspecific dietary variation is related to morphological variation in both size and shape as revealed by regression and discriminant function analyses. There is a significant negative relationship between the degree of insectivory and body size (wt). The existence of correlated patterns of dietary variation with environment and morphology supports the hypothesis that feeding strategy is adaptive and has been a factor in the evolutionary radiation of these groups. We propose that both phyllotines and akodonts arose from small, insectivorous ancestors. In conjunction with shifts toward herbivory, most phyllotines have evolved larger size plus tooth and jaw modifications. Calomys sorellus is atypical of other phyllotines; it is small, and insectivorous. Most Peruvian Akodon are also small and insectivorous; A. jelskii is an exceptional akodont being large and principally herbivorous.  相似文献   

14.
Anoles of the Anolis onca series represent a dramatic case of retrograde evolution, exhibiting great reduction (A. annectens) and loss (A. onca) of the subdigital pads considered a key innovation for the evolutionary radiation of anoles in arboreal environments. We present a molecular phylogenetic analysis of these anoles and their closest known relatives (A. auratus, A. lineatus, A. meridionalis, and A. nitens) using new mitochondrial DNA sequence data from the ND2 gene, five tRNA genes (tRNA(Trp), tRNA(Ala), tRNA(Asn), tRNA(Cys), tRNA(Tyr)), the origin of light-strand replication, and a portion of the CO1 gene (1,446 aligned base positions, 612 parsimony informative). Our results confirm monophyly of the A. onca series and suggest an evolutionary separation of approximately 10 million years between A. annectens and A. onca. Evolution of subdigital structure in this series illustrates ectopic expression of developmental programs that replace flexible subdigital lamellae of the toepad with rigid, keeled scales resembling dorsal digital scales. Our phylogenetic results indicate that narrowing of the toepad in A. auratus evolved separately from toepad reduction in the A. onca series. Expansion of the subdigital lamellae along the phalanges in A. auratus appears to compensate constriction of lamellae by digital narrowing, maintaining greater climbing capability in this species. Toepad evolution in the lineage ancestral to A. auratus features changes of the same developmental modules as the A. onca series but in the opposite direction. Large molecular distances between geographic populations of A. auratus indicate that its derived toepad structure is at least 9 million years old.  相似文献   

15.
We investigated the ecology and interspecific interactions of the two gibbon species (Hylobates lar and H. pileatus) that overlap in distribution within a narrow zone of contact in the headwaters of the Takhong River at Khao Yai National Park in central Thailand. The zone is about 10-km wide, with phenotypic hybrids comprising 6.5% of the adult population. We compared species with respect to diet, territory size, intra- and interspecific group encounters, and territory quality. The two gibbon species exploited the same types of resources within their territories despite variation in the relative abundance of food-plant species between territories. The gibbons were interspecifically territorial, and males of both species displayed aggressive behaviors at both intraspecific and interspecific territorial boundaries. There was no marked difference in the amount of overlap between territories of conspecific and heterospecific pairs of groups. Although the habitat was not homogeneous, territory quality did not vary significantly between species. The species have not diverged in habitat preference or in diet. Neither species dominated in interspecific encounters, and both were reproducing well in the contact zone. We analyzed the potential consequences of several types of interspecific interactions on individual dispersal options and on the structure of the contact zone. Interference competition through interspecific territoriality affects the dispersal of individuals into the range of the other species. In general, territorial competition coupled with limited hybridization leads to predictions of a narrow contact zone or parapatry between species; thus, behavioral and ecological interactions between species need to be considered as potential factors in explaining range borders of primate species.  相似文献   

16.
Extrapair paternity and the evolution of bird song   总被引:1,自引:0,他引:1  
Bird song is usually considered to have evolved in the contextof sexual selection. Because extrapair paternity is a majorcomponent of sexual selection, mating advantages at the sociallevel for males that produce songs of high quality may be transformedinto higher success in extrapair paternity. Therefore, maleswith longer and more complex songs should suffer less from extrapairpaternity intraspecifically, whereas species with high ratesof extrapair paternity, reflecting intense sperm competition,should produce more elaborate songs. Although some intraspecificstudies demonstrated a negative link between features of songsand extrapair paternity in own nest, others failed to detectsuch a relationship. Contrary to expectation, a meta-analysisof all studies revealed no significant intraspecific evidencefor songs being associated with extrapair paternity. In addition,in comparative analyses based on generalized least squares (GLS)models, we found that no measures of song complexity and temporaloutput were significantly related to extrapair paternity interspecifically,even when potentially confounding factors such as social matingsystem, life history, migration, habitat, or sexual dichromatismwere held constant. Only plumage dichromatism was significantlyrelated to extrapair paternity. The absence of both intra- andinterspecific relationships between measures of song variabilityand extrapair paternity suggests that factors other than postmatingsexual selection have been the important evolutionary forcesshaping differences in song.  相似文献   

17.

Background  

Ants form highly social and cooperative colonies that compete, and often fight, against other such colonies, both intra- and interspecifically. Some invasive ants take sociality to an extreme, forming geographically massive 'supercolonies' across thousands of kilometres. The success of social insects generally, as well as invasive ants in particular, stems from the sophisticated mechanisms used to accurately and precisely distinguish colonymates from non-colonymates. Surprisingly, however, the specific chemicals used for this recognition are virtually undescribed.  相似文献   

18.
In this paper we apply a new modelling strategy, called MICMAC modelling for studying the possibility of coexistence of two predators, which live in a patchy environment, which feed exclusively on one and the same prey and which do not interact intra- or interspecifically except through this common resource. The MICMAC modelling strategy enables us to model the interaction within each of the patches, the interaction among the patches, and the interaction between these models. The results of the simulations reveal that each of the following factors can cause coexistence by itself or in collaboration with the others: differences in risk of local extinction, dynamical isolation of patches, differences in relative duration of the growth and starvation phase.  相似文献   

19.
Skull structure is intimately associated with feeding ability in vertebrates, both in terms of specific performance measures and general ecological characteristics. This study quantitatively assessed variation in the shape of the cranium and mandible in varanoid lizards, and its relationship to structural performance (von Mises strain) and interspecific differences in feeding ecology. Geometric morphometric and linear morphometric analyses were used to evaluate morphological differences, and finite element analysis was used to quantify variation in structural performance (strain during simulated biting, shaking and pulling). This data was then integrated with ecological classes compiled from relevant scientific literature on each species in order to establish structure-function relationships. Finite element modelling results showed that variation in cranial morphology resulted in large differences in the magnitudes and locations of strain in biting, shaking and pulling load cases. Gracile species such as Varanus salvadorii displayed high strain levels during shaking, especially in the areas between the orbits. All models exhibit less strain during pull back loading compared to shake loading, even though a larger force was applied (pull =30N, shake = 20N). Relationships were identified between the morphology, performance, and ecology. Species that did not feed on hard prey clustered in the gracile region of cranial morphospace and exhibited significantly higher levels of strain during biting (P = 0.0106). Species that fed on large prey clustered in the elongate area of mandible morphospace. This relationship differs from those that have been identified in other taxonomic groups such as crocodiles and mammals. This difference may be due to a combination of the open ‘space-frame’ structure of the varanoid lizard skull, and the ‘pull back’ behaviour that some species use for processing large prey.  相似文献   

20.
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