María José Tulli

The interplay between claw morphology and microhabitat use in neotropical iguanian lizards.

Traditionally, it has been suggested that variation in locomotor mode should be correlated with variation in the anatomy of the structures responsible for locomotion. Indeed, organisms can expand their ecological niche by using specialized traits of the locomotor system including hooks, claws, adhesive pads, etc. Despite the fact that claws are the most common biological mechanism of clinging in vertebrates, little is known about their function or evolutionary relationship to habitat use. The present study focuses on claw morphology in 57 species of iguanian lizards occupying different microhabitats. Qualitative differences in claw shape were explored by means of digital photographs, and quantitative measurements of the length, height and curvature of the claws of both fingers and toes were taken and correlated to information on microhabitat use obtained from the literature. Our analyses showed a strong phylogenetic component that obscured relationships between morphology and ecology. Our results also show differences in claw morphology between species that appear to be related to microhabitat use (climbing versus terrestrial species), with the best ecological descriptors being claw length and height. Performance measures and biomechanical analyses of claw function may consequently be better suited to explain the evolution of claw shape in relation to habitat use in this group.

Effects of different substrates on the sprint performance of lizards.

SUMMARY The variation in substrate structure is one of the most important determinants of the locomotor abilities of lizards. Lizards are found across a range of habitats, from large rocks to loose sand, each of them with conflicting mechanical demands on locomotion. We examined the relationships among sprint speed, morphology and different types of substrate surfaces in species of lizards that exploit different structural habitats (arboreal, saxicolous, terrestrial and arenicolous) in a phylogenetic context. Our main goals were to assess which processes drive variability in morphology (i.e. phylogeny or adaptation to habitat) in order to understand how substrate structure affects sprint speed in species occupying different habitats and to determine the relationship between morphology and performance. Liolaemini lizards show that most morphological traits are constrained by phylogeny, particularly toe 3, the femur and foot. All ecological groups showed significant differences on rocky surfaces. Surprisingly, no ecological group performed better on the surface resembling its own habitat. Moreover, all groups exhibited significant differences in sprint speed among the three different types of experimental substrates and showed the best performance on sand, with the exception of the arboreal group. Despite the fact that species use different types of habitats, the highly conservative morphology of Liolaemini species and the similar levels of performance on different types of substrates suggest that they confer to the ‘jack of all trades and master of none’ principle.

Running in cold weather: morphology, thermal biology, and performance in the southernmost lizard clade in the world (Liolaemus lineomaculatus section: Liolaemini: Iguania)

The integration or coadaptation of morphological, physiological, and behavioral traits is represented by whole-organism performance traits such as locomotion or bite force. Additionally, maximum sprint speed is a good indicator of whole-organism performance capacity as variation in sprinting ability can affect survival. We studied thermal biology, morphology, and locomotor performance in a clade of Liolaemus lizards that occurs in the Patagonian steppe and plateaus, a type of habitat characterized by its harsh cold climate. Liolaemus of the lineomaculatus section display a complex mixture of conservative and flexible traits. The phylogenetically informed analyses of these ten Liolaemus species show little coevolution of their thermal traits (only preferred and optimum temperatures were correlated). With regard to performance, maximum speed was positively correlated with optimum temperature. Body size and morphology influenced locomotor performance. Hindlimbs are key for maximal speed, but forelimb length was a better predictor for sustained speed (i.e. average speed over a total distance of 1.2 m). Finally, sustained speed differed among species with different diets, with herbivores running on average faster over a long distance than omnivores.

Relationships among morphology, clinging performance and habitat use in Liolaemini lizards

The central tenet of ecomorphological theory holds that different ecological requirements lead to different organismal designs (morphology). Here, we studied the relationships between performance (interlocking grasping) and forelimb morphological traits in species of lizards that exploit different structural habitats in a phylogenetic context. The performance (measured by the maximum force of clinging to substrate) was measured on different substrate types. After phylogenetically informed analyses, we found that arboreal and saxicolous species showed stronger resistance to mechanical traction in all substrates when compared to generalists and sand dweller lizards. These species showed a positive relationship between forelimb dimensions (humerus length and length of claw of toe 5) and maximum force exerted, on the contrary, hand width, claw height (CH) of digits III and IV and claw length of toe 4 showed a negative relationship. In addition, we observed a partial positive correlation between CH and maximal cling force on rough surfaces, but not on smooth surfaces.

The Tendinous Patterns in the Palmar Surface of the Lizard Manus: Functional Consequences for Grasping Ability

In lizards, distinct patterns of the tendinous structures associated with the forearm flexors have been described. In most lizards, the m. flexor digitorum longus ends in a tendinous plate with an embedded sesamoid, from which tendons run to the terminal phalanx of each digit. This structure is known as the flexor plate. In many polychrotid lizards, however, the flexor digitorum longus muscle is continuous with individual tendons running to each digit, and no complete flexor plate is present. In most geckos, the flexor plate is reduced to a tendinous plate without sesamoid. To evaluate the consequences of these differences in morphology on locomotion and grasping, we compared the use of the fore‐arm and hand in lizards exhibiting three different tendon patterns (Pogona vitticeps, an agamid with a well‐developed flexor plate; Gekko gecko, a gekkonid with a flexor plate, but without an embedded sesamoid; Anolis equestris, a polychrotid without flexor plate, but showing independent tendons running to each digit) while moving on different substrates. We found that the presence of a flexor plate with sesamoid bone prevents digital flexion and creates a rather stiff palmar surface in P. vitticeps. This configuration makes it impossible for P. vitticeps to grasp narrow branches and results in a strongly impaired locomotor performance on narrow substrates. Both G. gecko and A. equestris can flex the palms of their hands and their fingers more extensively, and do so when moving on narrow substrates. We suggest that the reduction of the flexor plate in both G. gecko and A. equestris allows these animals to move effectively on narrow substrates. Anat Rec, 292:842–853, 2009.

An ecomorphological analysis of forelimb musculotendinous system in sigmodontine rodents (Rodentia, Cricetidae, Sigmodontinae)

Abstract The central tenet of ecomorphological theory holds that there is a correlation between design (morphological traits) and ecology of organisms. The sigmodontine rodents (Rodentia, Cricetidae, Sigmodontinae) exhibit a remarkably high diversity of locomotory types, allowing them to occupy different environments and ecological niches. The main aims of our work were to test whether the internal morphology of the forelimb of 26 species of sigmodontines, as assessed through the analysis of 32 characters, differs among taxa that exhibit different types of locomotion (saltatorial, ambulatory, fossorial, scansorial, and natatorial), and whether such patterns also can be explained by the phylogenetic affinities of the species examined. Our results show that phylogeny explains an important part of the observed morphological variation in sigmodontine rodents. This phylogenetic inertia could be responsible for the homogeneity in the overall muscle forelimb morphology in this group. Tendon variables seem to be better descriptors of locomotory types than muscule variables. Twelve tendon variables of the forelimb exhibit distinct differences between fossorial and scansorial sigmodontines. No particular morphological variables are associated with ambulatory, saltatorial, and natatorial taxa. Additionally, 3 muscles (triceps longus, extensor digitorum, and flexor digitorum profundus) exhibit a greater anatomical cross-sectional area in fossorial and natatorial taxa than in other locomotory types. Resumen La idea central de la teoría ecomorfológica plantea que existe una correlación entre los requisitos ecológicos y el diseño (morfología) de los organismos. Los roedores sigmodontinos presentan una amplia variedad de tipos locomotores que les permiten explorar distintos hábitats. Dada la escasez de estudios sobre aspectos ecomorfológicos del sistema músculo-tendinoso del miembro anterior, en este trabajo se propone investigar la relación entre los tipos locomotores y los rasgos morfológicos del miembro anterior en especies de sigmodontinos que exploran diferentes hábitats en un contexto filogenético. Se analizaron 32 caracteres en 26 especies de sigmodontinos exhibiendo distintos tipos de locomoción (cavador, trepador, saltador, terrestre y nadador) usando análisis de ordenamiento canónico. Nuestros resultados muestran que la filogenia explica una importante parte de la variación morfológica observada en los roedores sigmodontinos. Esta inercia filogenética podría ser la responsable de la homogeneidad morfológica general de los músculos del miembro anterior de este grupo. Se encontró que varios rasgos del sistema tendinoso fueron más informativos que los del sistema muscular, siendo aquellos los mejores descriptores para especies cavadoras y trepadoras. Doce rasgos del sistema tendinoso del miembro anterior de las especies cavadoras y trepadoras señalan interesantes diferencias entre estas dos actividades. Las especies saltadoras, terrestres y nadadoras no presentaron variables particulares asociadas con su tipo locomotor. Además, se observó que los cavadores y nadadores exhiben una mayor área de sección transversal anatómica de los tres músculos seleccionados (triceps longus, extensor digitorum, y flexor digitorum profundus) que el resto de las categorías locomotoras consideradas.

When a general morphology allows many habitat uses

During the last decades the study of functional morphology received more attention incorporating more detailed data corresponding to the internal anatomy that together contribute for a better understanding of the functional basis in locomotion. Here we focus on 2 lizard families, Tropiduridae and Liolaemidae, and use information related to muscle-tendinous and external morphology traits of hind legs. We investigate whether the value of the traits analyzed tend to exhibit a reduced phenotypic variation produced by stabilizing selection, and whether species showing specialization in their habitat use will also exhibit special morphological features related to it. As a result, we identified that evolution of hind limb traits is mainly explained by the Ornstein-Uhlenbeck model, suggesting stabilizing selection. Liolaemids and tropidurids show clear ecomorphological trends in the variables considered, with sand lizards presenting the most specialized morphological traits. Some ecomorphological trends differ between the 2 lineages, and traits of internal morphology tend to be more flexible than those of external morphology, restricting the ability to identify ecomorphs shared between these 2 lineages. Conservative traits of external morphology likely explain such restriction, as ecomorphs have been historically defined in other lizard clades based on variation of external morphology.

Interplay between postcranial morphology and locomotor types in Neotropical sigmodontine rodents

Sigmodontine rats are one of the most diverse components of the Neotropical mammal fauna. They exhibit a wide ecological diversity and a variety of locomotor types that allow them to occupy different environments. To explore the relationship between morphology and locomotor types, we analyzed traits of the postcranial osteology (axial and appendicular skeletons) of 329 specimens belonging to 51 species and 29 genera of sigmodontines exhibiting different locomotor types. In this work, postcranial skeletal characters of these rats are considered in an ecomorphological study for the first time. Statistical analyses showed that of the 34 osteological characters considered, 15 were related to the locomotor types studied, except for ambulatory. However, character mapping showed that climbing and jumping sigmodontines are the only taxa exhibiting clear adaptations in their postcranial osteology, which are highly consistent with the tendencies described in many other mammal taxa. Climbing, digging and swimming rats presented statistically differences in traits associated with their vertebral column and limbs, whereas jumping rats showed modifications associated with all the skeletal regions. Our data suggest that sigmodontine rats retain an all‐purpose morphology that allows them to use a variety of habitats. This versatility is particularly important when considering the lack of specialization of sigmodontines for a specific locomotor mode. Another possible interpretation is that our dataset probably did not consider relevant information about these groups and should be increased with other types of characters (e.g. characters from the external morphology, myology, etc.).

Anatomy of the Crus and Pes of Neotropical Iguanian Lizards in Relation to Habitat use and Digitally Based Grasping Capabilities

Ecomorphological studies of lizards have explored the role of various morphological traits and how these may be associated with, among other things, habitat use. We present an analysis of selected traits of internal morphology of the hind limbs of Neotropical iguanian lizards and their relationship to habitat use. Considering that one of the most widely‐held hypotheses relating to the origin of grasping is associated with the exploitation of the narrow‐branch arboreal habitat, we include subdivisions of this designation as two of our ecologically defined categories of habitat exploitation for analysis, and compare lizards assigned to these categories to the features displayed by terrestrial lizards. The influence of phylogeny in shaping the morphology of lizards was assessed by using the comparative method. K values were significant for several osteological traits. Most of the K values for the variables based upon muscle and tendon morphometric characters (13 out 21), by contrast, had values <1, suggesting that their variation cannot be explained by phylogeny alone. Results of our phylogenetic and conventional ANCOVA analyses reveal that the characters highlighted through the application of the comparative method are not absolutely related to habitat in terms of the categories considered here. It appears that the bauplan of the lizard pes incorporates a morphological configuration that is sufficiently versatile to enable exploitation of almost all of the available habitats. As unexpected as conservation of internal gross morphology appears, it represents a means of accommodating to environmental challenges by apparently permitting adequacy for all situations examined. Anat Rec, 297:397–409, 2014.

Osteological postcranial traits in hylid anurans indicate a morphological continuum between swimming and jumping locomotor modes

Anurans exhibit a particularly wide range of locomotor modes that result in wide variations in their skeletal structure. This article investigates the possible correlation between morphological aspects of the hylid postcranial skeleton and their different locomotor modes and habitat use. To do so, we analyzed 18 morphometric postcranial variables in 19 different anuran species representative of a variety of locomotor modes (jumper, hopper, walker, and swimmer) and habitat uses (arboreal, bush, terrestrial, and aquatic). Our results show that the evolution of the postcranial hylid skeleton cannot be explained by one single model, as for example, the girdles suggest modular evolution while the vertebral column suggests other evolutionary modules. In conjunction with data from several other studies, we were able to show a relationship between hylid morphology and habitat use; offering further evidence that the jumper/swimmer and walker/hopper locomotor modes exhibit quite similar morphological architecture. This allowed us to infer that new locomotor modalities are, in fact, generated along a morphological continuum. J. Morphol. 278:403–417, 2017.