Studies in Evo-Devo benefit from the use of a variety of organisms, as comparative approaches provide a better understanding of Biodiversity and Evolution. Standardized protocols to incubate eggs and manipulate embryo development enable postulation of additional species as suitable biological systems for research in the field.In the past decades, vertebrate lineages such as Squamata (lizards, snakes, and amphisbaenians) emerged as crucial study systems for addressing topics as diverse as phenotypic evolution and climate change. However, protocols for maintaining gravid females and incubating eggs in the lab under experimental conditions are available to only a few squamate species. This resource article presents a simple incubation guide that standardizes conditions to maintain embryos of Tropidurus catalanensis (Squamata: Tropiduridae) under different experimental conditions, manipulating relevant environmental factors like temperature and humidity. We identified associated effects relating the egg incubation condition to developmental stage, incubation time, hatching success, and resulting morphotypes. Temperature and humidity play a key role in development and require attention when establishing the experimental design. Current literature comprises information for Tropidurus lizards that ponders how general in Squamata are the ecomorphs originally described for Anolis. Studies evaluating phenotypic effects of developmental environments suggest plasticity in some of the traits that characterize the ecomorphological associations described for this family. We expect that this incubation guide encourages future studies using Tropidurus lizards to address Evo-Devo questions.
Coevolution of form and function inspires investigation of associations between morphological variation and the exploitation of specific ecological settings. Such relationships, based mostly on traits of external morphology, have been extensively described for vertebrates, and especially so for squamates. External features are, however, composed by both soft tissues and bones, and these likely play different biomechanical roles during locomotion, such as in the autopodia. Therefore, ecological trends identified on the basis of external morphological measurements may not be directly correlated with equivalent variation in osteology. Here, we investigate how refined parameters of autopodial osteology relate to ecology, by contrasting climbing and nonclimbing geckos. Our first step consisted of inferring how external and osteological morphometric traits coevolved in the group. Our results corroborate the hypothesis of coevolution between external and osteological elements in the autopodia of geckos, and provides evidence for associations between specific osteological traits and preferred locomotor habit. Specifically, nonclimbers exhibit longer ultimate and penultimate phalanges of Digit V in the manus and pes and also a longer fifth metatarsal in comparison with climbers, a pattern discussed here in the context of the differential demands made upon locomotion in specific ecological contexts. Our study highlights the relevance of osteological information for discussing the evolution of ecological associations of the tetrapod autopodium. J. Morphol. 278:290-299, 2017. © 2017 Wiley Periodicals, Inc.
Vertebrate limb morphology often reflects the environment due to variation in locomotor requirements. However, proximal and distal limb segments may evolve differently from one another, reflecting an anatomical gradient of functional specialization that has been suggested to be impacted by the timing of development. Here we explore whether the temporal sequence of bone condensation predicts variation in the capacity of evolution to generate morphological diversity in proximal and distal forelimb segments across more than 600 species of mammals. Distal elements not only exhibit greater shape diversity, but also show stronger within-element integration and, on average, faster evolutionary responses than intermediate and upper limb segments. Results are consistent with the hypothesis that late developing distal bones display greater morphological variation than more proximal limb elements. However, the higher integration observed within the autopod deviates from such developmental predictions, suggesting that functional specialization plays an important role in driving within-element covariation. Proximal and distal limb segments also show different macroevolutionary patterns, albeit not showing a perfect proximo-distal gradient. The high disparity of the mammalian autopod, reported here, is consistent with the higher potential of development to generate variation in more distal limb structures, as well as functional specialization of the distal elements.
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