Relations between microhabitat use and limb shape in phrynosomatid lizards

With the exception of the well-documented case for anoline lizards, recent studies have found few evolutionary relationships between morphology and habitat use in lizards despite clear-cut biomechanical predictions. One of the factors typically hampering these analyses is the clustering of habitat use within evolutionary lineages. In the present study, body shape was quantified for male and female lizards of 30 species of phrynosomatid lizards. This group was selected as little clustering of ecological variables seemed to be present. The results of traditional analyses indicate that evolutionary correlates of habitat use were prominent in the hindlimbs of both sexes. Species living in open habitats are characterized by longer femurs, and longer hindlimbs relative to the forelimb. Moreover, males from ground-dwelling species utilizing open habitats have longer toes on the hind foot than males from climbing species. Phylogenetic analyses indicated strong evolutionary associations between habitat use and the relative length of front and hindlimbs, with species from open terrestrial habitats having significantly shorter frontlimbs relative to their hindlimb than rock or tree climbing species. Evolutionary associations between morphology and habitat use were generally stronger for male lizards, indicating a potentially important contribution of sexual selection to the evolution of differences in limb proportions.  © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 77 , 149–163.     

Ontogenetic and individual variation in size, shape and speed in the Australian agamid lizard Amphibolurus nuchalis

The present study investigates relationships among size, shape and speed in the Australian agamid lizard Amphibolurus nuchalis . Maximal running speed, body mass, snout-vent length, tail length, fore- and hind limb spans and thigh muscle mass were measured in 68 field-fresh individuals spanning the entire ontogenetic size range (1.3 48 g). Relative lengths of both foreand hind limbs decrease with increasing body mass (= negative allometry), whereas relative tail length and thigh muscle mass increase with body mass (= positive allometry). Repeatable and significant differences in maximal running speed exist among individuals. Maximal running speed scales as (body mass)^0.161, and 59% of the variation in maximal speed was related to body mass. Based on the results of the present and previous studies, data on scaling of body proportions alone appear inadequate to infer scaling relationships of functional characters such as top speed.
Surprisingly, individual variation in maximal speed is not related to individual variation in shape (relative limb, tail and body lengths). These components of overall shape are not independent; individuals tended to have either relatively long or relatively short limbs, tails and bodies for their body mass. Even the significant difference in multivariate shape between adult males and females has no measurable consequences for maximal speed. Speeds of field-fresh animals did not vary on a seasonal basis, and eight weeks of captivity had no effect on maximal running speeds. Gravid females and long-term (obese) captive lizards were both approximately 12% slower than field-fresh lizards.     

Marine fungal lineages in the Hypocreomycetidae

Phylogenetic analyses of DNA sequences from protein coding and ribosomal nuclear loci support the placement of a number of marine fungal species associated with a well-supported clade containing fungicolous species of Melanospora and wood inhabiting Coronophorales. Three subclades containing marine species were recovered including Torpedospora radiata plus T. ambispinosa, Swampomyces species plus Juncigena adarca, and two Etheirophora species plus additional Swampomyces species. The monophyly of these three subclades, as well as a subclade containing representatives of Coronophorales and Melanospora, is well supported statistically. However, relationships among the different subclades remain largely unresolved. A sister relationship for this group with Hypocreales is significantly supported by Bayesian and ML methods. In addition to the Halospheariales and Lulworthiales, this clade, which is characterized by considerable morphological and ecological diversity, represents a third major clade of marine Sordariomycetes.     

A phylogenetic analysis of the tropidurine lizards (Squamata: Tropiduridae), including new characters of squamation and epidermal microstructure

Characters of scale surface microstructure are combined with 'traditional'morphological characters in a phylogenetic analysis of the Tropidurini. Tropidurid lizards show variation in types of coarse and fine scale surface microstructure, in the anatomical distribution of different scale surface features, and in scale organ morphology and distribution. The morphology of the inner surface zone of scales is here described for the first time using scanning electron microscopy. Our phylogeny differs considerably from those proposed in earlier studies. New characters and frequency coding of polymorphic characters help resolve the problematic relationships of several species. Statistical confidence supports recognition of one large cis-Andean and one large trans-Andean clade of species. Based on our results, we synonymize Plesiomicrolophus with Microlophus and Uranoscodon with Tropidurus. The phylogenetic relationships of newly discovered Tropidurus are resolved: T. caltathelys is the sister species of T. melanopleurus; T. xanthochilus is the sister species of T. spinulosus. Tropidurus spinulosus is found to be more closely related to T. strobilurus and a clade of Amazonian species than to T. melanopleurus. The species previously placed in Uracentron are more closely related to species previously placed in Plica than to 77 strobilurus as previously thought.     

The relationship between morphology, escape behaviour and microhabitat occupation in the lizard clade Liolaemus (Iguanidae: Tropidurinae: Liolaemini)

Phenotypic differences among species are known to have functional consequences that in turn allow species to use different habitats. However, the role of behaviour in this ecomorphological paradigm is not well defined. We investigated the relationship between morphology, ecology and escape behaviour among 25 species of the lizard clade Liolaemus in a phylogenetic framework. We demonstrate that the relationship between morphology and characteristics of habitat structure shows little or no association, consistent with a previous study on this group. However, a significant relationship was found between morphology and escape behaviour with the distance a lizard moved from a potential predator correlated with body width, axilla-groin length, and pelvis width. A significant relationship between escape behaviour and habitat structure occupation was found; lizards that occupied tree trunks and open ground ran longer distances from predators and were found greater distances from shelter. Behavioural strategies used by these lizards in open habitats appear to have made unnecessary the evolution of limb morphology that has occurred in other lizards from other clades that are found in open settings. Understanding differences in patterns of ecomorphological relationships among clades is an important component for studying adaptive diversification.     

Patterns of infestation by the trombiculid mite Eutrombicula alfreddugesi in four sympatric lizard species (genus Tropidurus) in northeastern Brazil

We studied the parasitism by the chigger mite Eutrombicula alfreddugesi on four sympatric lizard species of the genus Tropidurus in Morro do Chapéu, Bahia state, Brazil: T. hispidus, T. cocorobensis, T. semitaeniatus and T. erythrocephalus. For each species, we investigated the patterns of infestation and analyzed to which extent they varied among the hosts. We calculated the spatial niche breadth of the chigger mite on the body of each host species and the distribution of mites along the hosts' bodies for each Tropidurus species. All four species of Tropidurus at Morro do Chapéu were parasited by the chigger mite, with high (97-100%) prevalences. Host body size significantly explained the intensity of mite infestation for all species, except T. erythrocephalus. The body regions with highest intensity of infestation in the four lizard species were the mite pockets. The spacial niche width of the chigger varied consistently among the four lizards species studied being highest for T. erytrocephalus and lowest for T. cocorobensis. We conclude that the distribution and intensity with which lizards of the genus Tropidurus are infested by Eutrombicula alfreddugesi larvae results from the interaction between aspects of host morphology (such as body size and the occurrence and distribution of mite pockets) and ecology (especially microhabitat use).     

Limb segment contributions to the evolution of hind limb length in phrynosomatid lizards

Longer hind limbs are often associated with faster maximum sprint speeds measured in the laboratory and sometimes with increased Darwinian fitness in studies of individual variation in natural populations. Limb length may be altered by changing the length of one or all segments, with different functional consequences. Segment length evolution can be influenced by both natural and sexual selection, and lineage‐specific effects (multiple solutions) may also occur. We examined the evolution of total hind limb length, as well as thigh, crus, pes, and toe length, among 46 species of phrynosomatids and also investigated the role of habitat use and shared evolutionary history in shaping limb morphology. Because sexes are usually behaviourally and morphologically dimorphic, we examined them separately. In females, habitat was only an important predictor of crus (lower leg) length. In males, habitat was not an important predictor of any variable. Overall, clade‐level differences were more important than habitat as predictors of segment or total hind limb length. Not all limb segments scaled isometrically with the combined length of other segments, and both sex and clade affected the scaling of some segments. These results suggest that clade‐level differences are more important than habitat use for explaining differences in limb length and proportions, and sexual dimorphism may be an important consideration in morphology–performance–behaviour–fitness relationships.     

Does metatarsal/femur ratio predict maximal running speed in cursorial mammals?

We tested the hypothesis that hind limb proportions may be used to predict locomotor performance in a sample of 49 species of primarily cursorial mamals. Data on maximal sprint running speeds taken from published sources were related to measurements of hind limb lengths. To control for statistical complications due to the hierarchical nature of phylogenetic relationships, we used Felsenstein's (1985) independent contrasts method for analysing comparative data, and a composite phylogeny for all 49 species, based on a variety of published sources. The independent contrasts method indicates that maximal running speed does not covary significantly with body mass for this sample of mammals (mass range= 2.5–2,000 kg). Even though quality of the available speed data is highly variable, both metatarsal/femur ratio—the traditional index of 'cursoriality' in mammals—and hind limb length (corrected for body size) are significant predictors of maximal running speed. When only fully curorial species are included in the analyses (n = 32), hind limb length still significantly predicts speed (r²= 16%), but MT/F ratio does not. Although ungulates tend to have larger MT/F ratios than do Carnivora, they are not generally faster; relatonships between speed and limb proportions within the two clades show no significant differences. These and previous results suggest that hind limb proportions and maximal running speed may not have evolved in a tightly coupled fashion. Prediction of locomotor performance of extinct forms, based solely on their limb proportions, should be undertaken with caution.     

A tiny lizard (Lepidosauria,Squamata) from the Lower Cretaceous of Spain

Abstract: The smallest living amniotes are all lizards, but the fossil history of this size trait in Squamata is difficult to follow because small skeletons have low preservation potential and are often hard to detect in the field. A new squamate taxon, Jucaraseps grandipes gen. et sp. nov., is here described on the basis of an articulated skeleton from the Early Cretaceous Spanish lagerstätten of Las Hoyas. It differs from other known Mesozoic lizards in combining very small body size with a short rostrum, low maxillary tooth count, a relatively slender and elongated body, and short limbs with large hind feet. Phylogenetic analysis using TNT places it on the stem of a clade encompassing scincomorphs, gekkotans, snakes, amphisbaenians and anguimorphs. Comparison with modern lizards suggests it was probably a cryptic surface or subsurface ground dweller but not a burrower.     

Integration and dissociation of limb elements in flying vertebrates: a comparison of pterosaurs, birds and bats

Flapping flight has evolved independently in three vertebrate clades: pterosaurs, birds and bats. Each clade has a unique flight mechanism involving different elements of the forelimb. Here, patterns of limb integration are examined using partial correlation analysis within species and matrix correlation analysis across species to test whether the evolution of flapping flight has involved developmental dissociation of the serial homologues in the fore- and hind limb in each clade. Our sample included seven species of birds, six species of bats, and three species of pterosaurs for which sufficient sample sizes were available. Our results showed that, in contrast to results previously reported for quadrupedal mammals, none of the three clades demonstrated significant integration between serial homologues in the fore- and hind limb. Unexpectedly, there were few consistent patterns of within-forelimb correlations across each clade, suggesting that wing integration is not strongly constrained by functional relationships. However, there was significant integration within the hind limbs of pterosaurs and birds, but not bats, possibly reflecting the differing functions of hind limbs (e.g. upright support vs. suspension) in these clades.     

Ontogenetic Scaling of Fore- and Hind Limb Posture in Wild Chacma Baboons (Papio hamadryas ursinus)

Large-scale interspecific studies of mammals ranging between 0.04–280 kg have shown that larger animals walk with more extended limb joints. Within a taxon or clade, however, the relationship between body size and joint posture is less straightforward. Factors that may affect the lack of congruence between broad and narrow phylogenetic analyses of limb kinematics include limited sampling of (1) ranges of body size, and/or (2) numbers of individuals. Unfortunately, both issues are inherent in laboratory-based or zoo locomotion research. In this study, we examined the relationship between body mass and elbow and knee joint angles (our proxies of fore- and hind limb posture, respectively) in a cross-sectional ontogenetic sample of wild chacma baboons (Papio hamadryas ursinus) habituated in the De Hoop Nature Reserve, South Africa. Videos were obtained from 33 individuals of known age (12 to ≥108 months) and body mass (2–29.5 kg) during walking trials. Results show that older, heavier baboons walk with significantly more extended knee joints but not elbow joints. This pattern is consistent when examining only males, but not within the female sample. Heavier, older baboons also display significantly less variation in their hind limb posture compared to lighter, young animals. Thus, within this ontogenetic sample of a single primate species spanning an order of magnitude in body mass, hind limb posture exhibited a postural scaling phenomenon while the forelimbs did not. These findings may further help explain 1) why younger mammals (including baboons) tend to have relatively stronger bones than adults, and 2) why humeri appear relatively weaker than femora (in at least baboons). Finally, this study demonstrates how field-acquired kinematics can help answer fundamental biomechanical questions usually addressed only in animal gait laboratories.     

Sexual dimorphism of tail length in lacertid lizards: test of a morphological constraint hypothesis

Males of many lizard species have longer tails than similarly-sized females. We hypothesized that this dimorphism is induced by a longer non-autotomous tail part in males, which is associated with the presence of the copulatory organs at the tail base, and presumably reduces the males' ability to escape predation by tail shedding. A compensatory mechanism would be an increase of total tail length in males, to achieve equal lengths of the autotomous tail part in both sexes. A critical prediction of this 'morphological constraint' hypothesis is that the extent of dimorphism in total tail length increases with the magnitude of sexual differences in length of the non-autotomous tail base. We tested this prediction through a comparative study in a small clade of lacertid lizards. Within each of nine species, sexual differences in length of the non-autotomous tail base and in total tail length do not change with body size. All species, except one, exhibit a clear male-biased dimorphism in length of the non-breakable tail base. In all species studied, males have longer tails than females. We used the method of phylogenetically independent contrasts to explore the interspecific relation between dimorphism in length of the tail base and sexual differences in total tail length. Contrary to our prediction, we found no evidence for a positive correlation between the extent of dimorphism in both traits. Thus, constraints imposed by the male copulatory organs on tail autotomy do not seem to be a significant factor in the evolution of dimorphism in tail length in this clade of lacertid lizards.     

Phylogenetic studies on the Thamnocalamus group and its allies (Gramineae: Bambusoideae) based on its sequence data.

Phylogenetic analyses, using the parsimony method and the neighbor-joining method, of 31 species of the Thamnocalamus group and its allies based on internal transcribed spacer (ITS) sequences in nuclear ribosomal DNA are presented. Two species from Arundinaria and Acidosasa were used as outgroups. The ITS phylogeny strongly supports the monophyly of the Thamnocalamus group and its allies, which have pachymorph rhizomes and semelauctant synflorescences with three stamens. Within this clade, Chimonocalamus pallens was resolved in the basal position. The Thamnocalamus group, including species placed in Thamnocalamus, Fargesia (Sinarundinaria, Borinda), and Yushania, may be polyphyletic/paraphyletic according to the ITS phylogeny, but internal support was relatively low. All three sampled species of Ampelocalamus were resolved as a monophyletic group and may be related to Drepanostachyum hookerianum. Two taxa of Thamnocalamus and the species Gaoligongshania megalothyrsa were resolved as monophyletic despite their different morphological characters, but again with a low bootstrap support. Within the Fargesia yunnanensis subclade, the sister relationship of Fargesia fungosa and Fargesia edulis was supported. Another subclade, the Fargesia communis clade, was also weakly supported as monophyletic. However, further resolution within the Thamnocalamus group has not been provided by this sequence data. The results indicate that reevaluation of relationships within this group is necessary.     

Size dimorphism in Rankinia [Tympanocryptis] diemensis (Family Agamidae): sex-specific patterns and geographic variation

Sexual dimorphism has implications for a range of biological and ecological factors, and intersexual morphological differences within a species provide an ideal opportunity for investigating evolutionary influences on phenotypic variation. We investigated sexual size dimorphism (SSD) in an agamid species, Rankinia [Tympanocryptis] diemensis , to determine whether overall size and/or relative morphological trait size differences exist and whether geographic variation in size dimorphism occurs in this species. Relative morphological trait proportions included a range of head, limb, and inter-limb measurements. We found significant overall intersexual adult size differences; females were the larger sex across all sites but the degree of dimorphism between the sexes did not differ between sites. This female-biased size difference is atypical for agamid lizards, which are usually characterized by large male body size. In this species, large female-biased SSD appears to have evolved as a result of fecundity advantages. The size of relative morphological trait also differed significantly between the sexes, but in the opposite direction: relative head, tail, and limb sizes were significantly larger in males than females. This corresponds to patterns in trait size usually found in this taxonomic group, where male head and limb size is important in contest success such as male–male rivalry. There were site-specific morphological differences in hatchlings, including overall body size, tail, inter-limb, thigh, and hindlimb lengths; however, there were no sex-specific differences indicating the body size differences present in the adult form occur during ontogeny.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 699–709.     

Correlations between habitat use and body shape in a phrynosomatid lizard (Urosaurus ornatus): a population-level analysis

Recent ecomorphological studies have shown that the predicted correlations between morphology and ecology on broad taxonomic levels are often obscured when comparing more closely related groups. Among species, comparisons of lizards often indicate very little support for adaptive radiations into novel habitats. As few population level studies have been performed, we compared body, head and limb shape between four populations of Urosaurus ornatus living in structurally distinct habitats (cliffs, rocks, trees and boulders). Surprisingly, clear correlations between habitat use and body shape among populations were found, most of which were in good accordance with a priori biomechanical predictions (e.g. flat body and head for extreme climbers; long distal hindlimb segments for jumpers and runners; narrow body and long tail for tree dwelling lizards). This indicates that populations of Urosaurus ornatus are seemingly 'adapted' to the habitat they live in. However, quantification of performance and behaviour are needed to determine the adaptive nature of these observations.     

Intraspecific ecomorphological variation: linear and geometric morphometrics reveal habitat‐related patterns within Podarcis bocagei wall lizards

Morphological variation in relation to habitat is known to occur in several lizard groups. Comparative studies have linked morphology and habitat use, showing that locomotion is the principal mediator of this evolutionary relationship. Here, we investigate intraspecific ecomorphological variation in Podarcis bocagei by examining three habitat types, representing a variety between saxicolous and ground‐dwelling habits. Our results indicate variation in absolute and relative limb length, but patterns are only partially concordant to biomechanical predictions. Whereas the femur and hind foot are longer in ground‐dwelling lizards, confirming previous observations, the tibia and hind limb are relatively shorter, contradicting expectations. Additionally, head shape varies substantially between habitats, in line with a hypothesis of mechanical restrictions related to microhabitat and refuge use. Finally, we detect male‐specific variation between habitats in total body size and head size, providing evidence for interactions between natural and sexual selection. Although performance and behaviour studies are necessary to definitely confirm the functional and evolutionary significance of the observed patterns, our study indicates that ecomorphological adaptations can arise in a very short evolutionary time in this group of lizards.     

Delimitation and phylogeny of Aletris (Nartheciaceae) with implication for perianth evolution

Aletris, containing approximately 21 species, is the largest genus in Nartheciaceae, and is disjunctively distributed in eastern Asia and eastern North America. Its delimitation has been controversial because it is uncertain whether Metanarthecium should be included in the genus. Although there are a few molecular phylogenetic studies on Aletris, the interspecific relationships within the genus have never been evaluated in a phylogenetic context. Here we used two cpDNA loci, matK and trnL-F, to delimitate Aletris and discuss the phylogeny within the genus. Phylogenetic analyses showed Metanarthecium might be distantly related to Aletris. This is also supported by morphological, palynological, cytological, and phytochemical data. Therefore, Metanarthecium should be excluded from Aletris. Within Aletris, there are two major clades: A. farinosa and A. lutea of eastern North America and A. glabra of eastern Asia form clade A; and the remaining Asian species form clade B. The Asian clade includes three subclades: subclade I (two varieties of A. pauciflora, and A. glandulifera and A. megalantha), subclade II (three samples of A. laxiflora), and subclade III (all other sampled Asian species). Based on phylogenetic relationships, A. pauciflora var. khasiana deserves a specific status, and A. gracilipes, formerly a synonym of A. laxiflora, should be reinstated. The reconstruction of the perianth evolution indicates that perianth connate halfway and glabrous on abaxial surface are plesiomorphic for Aletris and Nartheciaceae. Farinose-glutinous perianth is a diagnostic character for clade A.     

THE EVOLUTION OF FORM AND FUNCTION: MORPHOLOGY AND LOCOMOTOR PERFORMANCE IN WEST INDIAN ANOLIS LIZARDS

I tested biomechanical predictions that morphological proportions (snout–vent length, forelimb length, hindlimb length, tail length, and mass) and maximal sprinting and jumping ability have evolved concordantly among 15 species of Anolis lizards from Jamaica and Puerto Rico. Based on a phylogenetic hypothesis for these species, the ancestor reconstruction and contrast approaches were used to test hypotheses that variables coevolved. Evolutionary change in all morphological and performance variables scales positively with evolution of body size (represented by snout–vent length); size evolution accounts for greater than 50% of the variance in sprinting and jumping evolution. With the effect of the evolution of body size removed, increases in hindlimb length are associated with increases in sprinting and jumping capability. When further variables are removed, evolution in forelimb and tail length exhibits a negative relationship with evolution of both performance measures. The success of the biomechanical predictions indicates that the assumption that evolution in other variables (e.g., muscle mass and composition) did not affect performance evolution is probably correct; evolution of the morphological variables accounts for approximately 80% of the evolutionary change in performance ability. In this case, however, such assumptions are clade-specific; extrapolation to taxa outside the clade is thus unwarranted. The results have implications concerning ecomorphological evolution. The observed relationship between forelimb and tail length and ecology probably is a spurious result of the correlation between these variables and hindlimb length. Further, because the evolution of jumping and sprinting ability are closely linked, the ability to adapt to certain microhabitats may be limited.     

Limb proportions in climbing and ground-dwelling geckos (Lepidosauria, Gekkonidae): a phylogenetically informed analysis

Biomechanical considerations predict that limb proportions should differ between animals with climbing and ground-dwelling lifestyles. Ground-dwellers should have relatively long, parasagittal hind limbs, with high tibia:femur ratios, and relatively short fore limbs. Climbers should have relatively short limbs, with low tibia:femur ratios, and equally long hind and fore limbs. We tested these predictions using gecko species with different locomotion habits (climbing versus ground-dwelling). We measured snout-vent length and lengths of limb segments in 29 species of geckos and analysed them using both non-phylogenetic statistics (nested analysis of variance and principal component analysis) and phylogenetic statistics (analysis of covariance). Neither approach allowed us to find any consistent relationship between habitat use and the morphometric variables. We conclude that either relative limb lengths and limb proportions in geckos have not evolved in response to the physical demands of the microhabitat, or our understanding of those demands is insufficient. Accepted: 22 February 2001     

The m. caudifemoralis longus and its relationship to caudal autotomy and locomotion in lizards (Reptilia: Sauna)

Although the phenomenon of tail autotomy has traditionally been viewed in a purely adaptive light, functional constraints imposed by the locomotor system appear to have influenced the presence and extent of autotomy in lizards. Them. caudifemoralis longus is an unsegmented hind limb retractor that originates from the caudal vertebrae. It does not participate in autotomy and thus limits the proximal position of autotomic septa. Variation in the extent of the m. caudifemoralis is correlated with locomotor type. The muscle is large and originates from a long series of caudal vertebrae in fast moving lizards with powerful limb retraction, as exemplified by taxa capable of bipedal running. In slower lizards with sprawling postures, such as geckos, the m. caudifemoralis is small and restricted to the first few postsacral vertebrae. Autotomy is typically restricted or absent in the former lizards, while in the latter only the most proximal vertebrae are incapable of autotomy. In the evolution of existing patterns of caudal autotomy, functional demands intrinsic to the tail may be subservient to locomotor constraints imposed on the tail base by the m. caudifemoralis longus .