The evolution of jumping performance in anurans: morphological correlates and ecological implications

We investigated the evolution of anuran locomotor performance and its morphological correlates as a function of habitat use and lifestyles. We reanalysed a subset of the data reported by Zug (Smithson. Contrib. Zool. 1978; 276: 1–31) employing phylogenetically explicit statistical methods (n = 56 species), and assembled morphological data on the ratio between hind-limb length and snout-vent length (SVL) from the literature and museum specimens for a large subgroup of the species from the original paper (n = 43 species). Analyses using independent contrasts revealed that classifying anurans into terrestrial, semi-aquatic, and arboreal categories cannot distinguish between the effects of phylogeny and ecological diversification in anuran locomotor performance. However, a more refined classification subdividing terrestrial species into 'fossorials' and 'non-fossorials', and arboreal species into 'open canopy', 'low canopy' and 'high canopy', suggests that part of the variation in locomotor performance and in hind-limb morphology can be attributed to ecological diversification. In particular, fossorial species had significantly lower jumping performances and shorter hind limbs than other species after controlling for SVL, illustrating how the trade-off between burrowing efficiency and jumping performance has resulted in morphological specialization in this group.     

Do functional demands associated with locomotor habitat,diet, and activity pattern drive skull shape evolution in musteloid carnivorans?

A major goal of evolutionary studies is to better understand how complex morphologies are related to the different functions and behaviours in which they are involved. For example, during locomotion and hunting behaviour, the head and the eyes have to stay at an appropriate level in order to reliably judge distance as well as to provide postural information. The morphology and orientation of the orbits and cranial base will have an impact on eye orientation. Consequently, variation in orbital and cranial base morphology is expected to be correlated with aspects of an animal's lifestyle. In this study, we investigate whether the shape of the skull evolves in response to the functional demands imposed by ecology and behaviour using geometric morphometric methods. We test if locomotor habitats, diet, and activity pattern influence the shape of the skull in musteloid carnivorans using (M)ANOVAs and phylogenetic (M)ANOVAs, and explore the functional correlates of morphological features in relation to locomotor habitats, diet, and activity pattern. Our results show that phylogeny, locomotion and, diet strongly influence the shape of the skull, whereas the activity pattern seems to have a weakest influence. We also show that the locomotor environment is highly integrated with foraging and feeding, which can lead to similar selective pressures and drive the evolution of skull shape in the same direction. Finally, we show similar responses to functional demands in musteloids, a super family of close related species, as are typically observed across all mammals suggesting the pervasiveness of these functional demands.     

Patterns of cranial shape diversification during the phylogenetic branching process of New World monkeys (Primates: Platyrrhini)

One of the central topics in evolutionary biology is understanding the processes responsible for phenotypic diversification related to ecological factors. New World monkeys are an excellent reference system to investigate processes of diversification at macroevolutionary scales. Here, we investigate the cranial shape diversification related to body size and ecology during the phylogenetic branching process of platyrrhines. To investigate this diversification, we used geometric morphometric techniques, a molecular phylogenetic tree, ecological data and phylogenetic comparative methods. Our statistical analyses demonstrated that the phylogenetic branching process is the most important dimension to understand cranial shape variation among extant platyrrhines and suggested that the main shape divergence among the four principal platyrrhine clades probably occurred during the initial branching process. The phylogenetic conservatism, which is the retention of ancestral traits over time within the four principal platyrrhine clades, could be the most important characteristic of platyrrhine cranial shape diversification. Different factors might have driven early shape divergence and posterior relative conservatism, including genetic drift, stabilizing selection, genetic constraints owing to pleiotropy, developmental or functional constraint, lack of genetic variation, among others. Understanding the processes driving the diversification among platyrrhines will probably require further palaeontological, phylogenetic and comparative studies.     

Where to Live? How Morphology and Evolutionary History Predict Microhabitat Choice by Tropical Tadpoles

Tadpoles have diverse morphologies and occupy diverse habitats. The morphological differences between tadpoles can be represented by linear and geometric measurements and used to explain the organization of tadpole assemblages. However, the effects of evolutionary history must be isolated from the morphological differences before we can determine which patterns result from the use and sharing of common ecological resources. Here, we aimed to determine how morphological similarities and phylogenetic distances affect microhabitat choice by tadpoles. We analyzed the tadpoles of 101 anuran species and classified them according to ecomorphological guild, habitat use, position in the water column, and floor substrate. We used geometric and traditional morphometric approaches to describe the morphological variation among tadpoles and calculated the patristic distance for each species. Afterwards, we used morphometric and phylogenetic matrices as predictors of the variance in the ecological matrix, using a partial redundancy analysis. When we used traditional morphometric data, phylogeny explained a large amount of the ecological variation. By contrast, when we used geometric morphometric data, morphology and phylogeny explained similar amounts of the ecological variation, showing that the technique used to extract morphological variation affects the results. We provide evidence that both morphology, as a surrogate for contemporary factors, and evolutionary inertia are important in determining the behavior of tadpoles. Thus, niche conservatism can be important in modeling the behavior of tadpoles, but does not explain all the preferences of tadpoles.     

Morphology of locomotor appendages in Arachnida: evolutionary trends and phylogenetic implications

The morphological diversity of locomotor appendages in Arachnida is surveyed lo reconstruct phylogenetic relationships and discover evolutionary trends in form and function. The appendicular skeleton and musculature of representatives from the ten living arachnid orders ate described, and a system of homology is proposed. Character polarities are established through comparison with an outgroup. Limulus polyphemus Xiphosura). Cladistic analysis suggests that Arachnida is monophyletic and that absence of extensor muscles is a primitive condition. Extensors are primitively absent in Araneae. Amblypygi, Uropygi, Palpigradi, Ricinulei and Acari. Most similarities in the appendages of these orders are symplesiomorphic so that phylogenetic relationships among the 'extensorless' groups cannot be resolved solely on the basis of appendicular characters. Extensor muscles appear to have evolved once, and their presence is considered a synapomorphic feature of Opiliones, Scorpiones, Pseudoscorpiones and Solifugae. Solifugae lack extensors, but a parsimonious interpretation of other characters indicates that this is a secondary, derived condition. The phylogenetic relationships among these four orders are clarified by modifications of the patellotibial joint. Cladistic analysis indicates that Opiliones may be the sister group of the other three orders and that Scorpiones is the sister group of Pseudoscorpiones and Solifugae. Conclusions concerning phylogenetic relationships and evolutionary morphology presented here differ substantially from those of earlier studies on the locomotor appendages of Arachnida.     

Convergent evolution of lizard toe fringes

Lizard toe fringes are composed of laterally projecting elongated scales and have arisen independently at least 26 times in seven families of lizards. Four different fringe types are identified: triangular, projectional, conical and rectangular. To determine if variation in fringe morphology can be attributed to environmental differences, each independent evolution of a fringe type is identified; correlation of substrate types with evolutionary independent fringe morphologies are then studied. Variation in fringe morphology shows a strong association with substrate type: triangular, projectional and conical fringes with windblown sand; and rectangular fringes with water. Some aspects of fringe morphology may result from differences in functional requirements, and others may have no adaptive significance. This example of convergent evolution points out difficulties inherent to comparative studies of adaptation and underscores the value of broad comparative surveys which provide an alternative to ad hoc adaptive explanations of similarity.     

Morphological cranial diversity contributes to phylogeny in soft-furred sengis (Afrotheria, Macroscelidea)

Despite the well-supported Macroscelidea phylogeny proposed at the end of the 1960s, several systematic arrangements have been suggested in the last 20 years, raising doubts about the phylogeny of the Macroscelidinae; sengi inter-specific relationships are still debated to this day. The main issue of concern involves the supposed Elephantulus diphyly. To solve this persisting debate about sengi phylogeny, we examined the cranium ventral surface of 13 species using geometric morphometric techniques and neighbour-joining algorithms. This study supported the idea that the ventral side of the sengi cranium has the potential to provide important signals for reconstructing the Macroscelidea phylogeny. The phylogenetic signals seemed to differentiate between two major clades in the sengi radiation. In the first clade, the two monospecific genera (Petrodromus and Macroscelides), the two African Horn species (Elephantulus revoilii and E. rufescens), and the only North African species (E. rozeti) were clustered together. The second clade includes the remnant south-central African Elephantulus species. Our results were in agreement with both mitochondrial and nuclear data, confirmed that there is no Elephantulus monophyly and highlighted the close relationship between Petrodromus and E. rozeti. It appears that all the soft-furred sengi species are organised in two evolutionary lines: an old monophyletic clade, comprising only Elephantulus species, and a new polyphyletic clade, including P. tetradactylus, M. proboscideus, and E. rozeti. This requires a taxonomic and nomenclatural rearrangement within Macroscelidinae, where the phylogenetic position of the remnant 4 (of 12) Elephantulus species has yet to be fully defined.