The Experts below are selected from a list of 429 Experts worldwide ranked by ideXlab platform
David W. Kikuchi - One of the best experts on this subject based on the ideXlab platform.
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More than mimicry? Evaluating scope for flicker-fusion as a defensive strategy in coral snake mimics
Current Zoology, 2014Co-Authors: Georgia Titcomb, David W. Kikuchi, David W. PfennigAbstract:Coral snakes and their mimics often have brightly colored banded patterns, generally associated with warning colora- tion or mimicry. However, such color patterns have also been hypothesized to aid snakes in escaping predators through a "flicker-fusion" effect. According to this hypothesis, banded color patterns confuse potential predators when a snake transitions from resting to moving because its bands blur together to form a different color. To produce this motion blur, a moving snake's bands must transition faster than the critical flicker-fusion rate at which a predator's photoreceptors can refresh. It is unknown if coral snakes or their mimics meet this requirement. We tested this hypothesis by measuring the movement speed and color pat- terns of two coral snake mimics, Lampropeltis triangulum campbelli and L. elapsoides, and comparing the frequency of color transitions to the photoreceptor activity of the avian eye. We found that snakes often produced a motion blur, but moving snakes created a blurring effect more often in darker conditions, such as sunrise, sunset, and nighttime when these snakes are often active. Thus, at least two species of coral snake mimics are capable of achieving flicker-fusion, indicating that their color patterns may confer an additional defense aside from mimicry (Current Zoology 60 (1): 123130, 2014).
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A Batesian mimic and its model share color production mechanisms
Current Zoology, 2012Co-Authors: David W. KikuchiAbstract:Batesian mimics are harmless prey species that resemble dangerous ones (models), and thus receive protection from predators. How such adaptive resemblances evolve is a classical problem in evolutionary biology. Mimicry is typically thought to be difficult to evolve, especially if the model and mimic produce the convergent phenotype through different proximate mechanisms. However, mimicry may evolve more readily if mimic and model share similar pathways for producing the convergent phenotype. In such cases, these pathways can be co-opted in ancestral mimic populations to produce high-fidelity mimicry without the need for major evolutionary innovations. Here, we show that a Batesian mimic, the scarlet kingsnake Lampropeltis elapsoides , produces its coloration using the same physiological mechanisms as does its model, the eastern coral snake Micrurus fulvius . Therefore, precise color mimicry may have been able to evolve easily in this system. Generally, we know relatively little about the proximate mechanisms underlying mimicry.
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Predator Cognition Permits Imperfect Coral Snake Mimicry
The American naturalist, 2010Co-Authors: David W. KikuchiAbstract:Abstract: Batesian mimicry is often imprecise. An underexplored explanation for imperfect mimicry is that predators might not be able to use all dimensions of prey phenotype to distinguish mimics from models and thus permit imperfect mimicry to persist. We conducted a field experiment to test whether or not predators can distinguish deadly coral snakes (Micrurus fulvius) from nonvenomous scarlet kingsnakes (Lampropeltis elapsoides). Although the two species closely resemble one another, the order of colored rings that encircle their bodies differs. Despite this imprecise mimicry, we found that L. elapsoides that match coral snakes in other respects are not under selection to match the ring order of their model. We suggest that L. elapsoides have evolved only those signals necessary to deceive predators. Generally, imperfect mimicry might suffice if it exploits limitations in predator cognitive abilities.
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Notes and Comments Predator Cognition Permits Imperfect Coral Snake Mimicry
2010Co-Authors: David W. KikuchiAbstract:Batesian mimicry is often imprecise. An underexplored explanation for imperfect mimicry is that predators might not be able to use all dimensions of prey phenotype to distinguish mimics from models and thus permit imperfect mimicry to persist. We con- ducted a field experiment to test whether or not predators can dis- tinguish deadly coral snakes (Micrurus fulvius) from nonvenomous scarlet kingsnakes (Lampropeltis elapsoides). Although thetwospecies closely resemble one another, the order of colored rings that encircle their bodies differs. Despite this imprecise mimicry, we found that L. elapsoides that match coral snakes in other respects are not under selection to match the ring order of their model. We suggest that L. elapsoides have evolved only those signals necessary to deceive pred- ators. Generally, imperfect mimicry might suffice if it exploits lim- itations in predator cognitive abilities.
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High-model abundance may permit the gradual evolution of Batesian mimicry: an experimental test.
Proceedings of the Royal Society B: Biological Sciences, 2009Co-Authors: David W. KikuchiAbstract:In Batesian mimicry, a harmless species (the ‘mimic’) resembles a dangerous species (the ‘model’) and is thus protected from predators. It is often assumed that the mimetic phenotype evolves from a cryptic phenotype, but it is unclear how a population can transition through intermediate phenotypes; such intermediates may receive neither the benefits of crypsis nor mimicry. Here, we ask if selection against intermediates weakens with increasing model abundance. We also ask if mimicry has evolved from cryptic phenotypes in a mimetic clade. We first present an ancestral character-state reconstruction showing that mimicry of a coral snake (Micrurus fulvius) by the scarlet kingsnake (Lampropeltis elapsoides) evolved from a cryptic phenotype. We then evaluate predation rates on intermediate phenotypes relative to cryptic and mimetic phenotypes under conditions of both high- and low-model abundances. Our results indicate that where coral snakes are rare, intermediate phenotypes are attacked more often than cryptic and mimetic phenotypes, indicating the presence of an adaptive valley. However, where coral snakes are abundant, intermediate phenotypes are not attacked more frequently, resulting in an adaptive landscape without a valley. Thus, high-model abundance may facilitate the evolution of Batesian mimicry.
Frank T Burbrink - One of the best experts on this subject based on the ideXlab platform.
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exploring chihuahuan desert diversification in the gray banded kingsnake Lampropeltis alterna serpentes colubridae
Molecular Phylogenetics and Evolution, 2019Co-Authors: Edward A. Myers, Robert W. Bryson, Robert W Hansen, Matthew L Aardema, David Lazcano, Frank T BurbrinkAbstract:Abstract Within many biomes, the cause of phylogeographic structure remains unknown even across regions throughout North America, including within the biodiverse Chihuahuan Desert. For example, little is known about population structure or the timing of diversification of Chihuahuan endemics. This is due largely to the lack of population genomic studies within this region. We generated ultra-conserved element data for the gray-banded kingsnake (Lampropeltis alterna) to investigate lineage divergence and historical demography across the Chihuahuan Desert. We found three unique lineages corresponding to the Trans-Pecos and Mapimian biogeographic regions of the Chihuahuan Desert, and a distinct population in the Sierra Madre Occidental. Using several mutation rates to calibrate the timing of divergence among these lineages, we show that lineage divergence likely occurred during the Pleistocene, which indicates that careful consideration needs to be used when applying mutation rates to ultra-conserved elements. We suggest that biogeographic provinces within the Chihuahuan Desert may have served as allopatric refugia during climatic fluctuations of the Quaternary. This work serves as an important template for further testing biogeographic hypotheses within the region.
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Data 3. BioGeoBEARS code for estimating ancestral area in Lampropeltis.
2018Co-Authors: Frank T Burbrink, Marcelo GeharaAbstract:BioGeoBEARS code for estimating ancestral area in Lampropeltis
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Data 2. Georeferenced data for all species of Lampropeltis used for modeling range.
2018Co-Authors: Frank T Burbrink, Marcelo GeharaAbstract:Georeferenced data for all species of Lampropeltis used for modeling range
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Supplementary Fig. S3. Reticulating phylogenies of Lampropeltis from SNaQ for hybrid node numbers from 2-10. Note that hybrid nodes 0,1 are shown in Fig.1
2018Co-Authors: Frank T Burbrink, Marcelo GeharaAbstract:Reticulating phylogenies of Lampropeltis from SNaQ for hybrid node numbers from 2-10. Note that hybrid nodes 0,1 are shown in Fig.
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ND4 nexus file
2016Co-Authors: Edward A. Myers, Richard E Staub, Javier A. Rodríguez-robles, Alyssa Stropoli, Sara Ruane, Frank T BurbrinkAbstract:Aligned ND4 locus originally from Rodríguez-Robles JA, DeNardo DF, Staub RE (1999) Phylogeography of the California mountain kingsnake, Lampropeltis zonata (Colubridae). Molecular Ecology 8, 1923-1934
Robert W. Bryson - One of the best experts on this subject based on the ideXlab platform.
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exploring chihuahuan desert diversification in the gray banded kingsnake Lampropeltis alterna serpentes colubridae
Molecular Phylogenetics and Evolution, 2019Co-Authors: Edward A. Myers, Robert W. Bryson, Robert W Hansen, Matthew L Aardema, David Lazcano, Frank T BurbrinkAbstract:Abstract Within many biomes, the cause of phylogeographic structure remains unknown even across regions throughout North America, including within the biodiverse Chihuahuan Desert. For example, little is known about population structure or the timing of diversification of Chihuahuan endemics. This is due largely to the lack of population genomic studies within this region. We generated ultra-conserved element data for the gray-banded kingsnake (Lampropeltis alterna) to investigate lineage divergence and historical demography across the Chihuahuan Desert. We found three unique lineages corresponding to the Trans-Pecos and Mapimian biogeographic regions of the Chihuahuan Desert, and a distinct population in the Sierra Madre Occidental. Using several mutation rates to calibrate the timing of divergence among these lineages, we show that lineage divergence likely occurred during the Pleistocene, which indicates that careful consideration needs to be used when applying mutation rates to ultra-conserved elements. We suggest that biogeographic provinces within the Chihuahuan Desert may have served as allopatric refugia during climatic fluctuations of the Quaternary. This work serves as an important template for further testing biogeographic hypotheses within the region.
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DOI:10.1093/sysbio/syt099 Coalescent Species Delimitation in Milksnakes (Genus Lampropeltis) and Impacts on Phylogenetic Comparative Analyses
2016Co-Authors: Sara Ruane, Alexander R Pyron, Robert W. Bryson, T. BurbrinkAbstract:Abstract.—Both gene-tree discordance and unrecognized diversity are sources of error for accurate estimation of species trees, and can affect downstream diversification analyses by obscuring the correct number of nodes, their density, and the lengths of the branches subtending them. Although the theoretical impact of gene-tree discordance on evolutionary analyses has been examined previously, the effect of unsampled and cryptic diversity has not. Here, we examine how delimitation of previously unrecognized diversity in the milksnake (Lampropeltis triangulum) and use of a species-tree approach affects both estimation of the Lampropeltis phylogeny and comparative analyses with respect to the timing of diversification. Coalescent species delimitation indicates that L. triangulum is not monophyletic and that there are multiple species of milksnake, which increases the known species diversity in the genus Lampropeltis by 40%. Both genealogical and temporal discordance occurs between gene trees and the species tree, with evidence that mitochondrial DNA (mtDNA
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coalescent species delimitation in milksnakes genus Lampropeltis and impacts on phylogenetic comparative analyses
Systematic Biology, 2014Co-Authors: Alexander R Pyron, Frank T Burbrink, Sara Ruane, Robert W. BrysonAbstract:Both gene-tree discordance and unrecognized diversity are sources of error for accurate estimation of species trees, and can affect downstream diversification analyses by obscuring the correct number of nodes, their density, and the lengths of the branches subtending them. Although the theoretical impact of gene-tree discordance on evolutionary analyses has been examined previously, the effect of unsampled and cryptic diversity has not. Here, we examine how delimitation of previously unrecognized diversity in the milksnake (Lampropeltis triangulum) and use of a species-tree approach affects both estimation of the Lampropeltis phylogeny and comparative analyses with respect to the timing of diversification. Coalescent species delimitation indicates that L. triangulum is not monophyletic and that there are multiple species of milksnake, which increases the known species diversity in the genus Lampropeltis by 40%. Both genealogical and temporal discordance occurs between gene trees and the species tree, with evidence that mitochondrial DNA (mtDNA) introgression is a main factor. This discordance is further manifested in the preferred models of diversification, where the concatenated gene tree strongly supports an early burst of speciation during the Miocene, in contrast to species-tree estimates where diversification follows a birth-death model and speciation occurs mostly in the Pliocene and Pleistocene. This study highlights the crucial interaction among coalescent-based phylogeography and species delimitation, systematics, and species diversification analyses. (Divergence-time estimation; diversification rates; Lampropeltini; gene-tree/species- tree discordance; mtDNA introgression; Pleistocene diversification.)
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Coalescent species delimitation in milksnakes (genus Lampropeltis) and impacts on phylogenetic comparative analyses
2014Co-Authors: Sara Ruane, Alexander R Pyron, Robert W. Bryson, T. BurbrinkAbstract:Abstract.—Both gene-tree discordance and unrecognized diversity are sources of error for accurate estimation of species trees, and can affect downstream diversification analyses by obscuring the correct number of nodes, their density, and the lengths of the branches subtending them. Although the theoretical impact of gene-tree discordance on evolutionary analyses has been examined previously, the effect of unsampled and cryptic diversity has not. Here, we examine how delimitation of previously unrecognized diversity in the milksnake (Lampropeltis triangulum) and use of a species-tree approach affects both estimation of the Lampropeltis phylogeny and comparative analyses with respect to the timing of diversification. Coalescent species delimitation indicates that L. triangulum is not monophyletic and that there are multiple species of milksnake, which increases the known species diversity in the genus Lampropeltis by 40%. Both genealogical and temporal discordance occurs between gene trees and the species tree, with evidence that mitochondrial DNA (mtDNA
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a phylogeny of the Lampropeltis mexicana complex serpentes colubridae based on mitochondrial dna sequences suggests evidence for species level polyphyly within Lampropeltis
Molecular Phylogenetics and Evolution, 2007Co-Authors: Robert W. Bryson, Frank T Burbrink, Jennifer Pastorini, Michael R J ForstnerAbstract:The systematic relationships of snakes in the Lampropeltis mexicana complex (L. mexicana, L. alterna, and L. ruthveni) are poorly known despite several taxonomic studies over the last 80 years. Mitochondrial DNA sequences were used to infer the phylogeny of the L. mexicana complex. At least one representative sample from the nine currently recognized species of Lampropeltis was sequenced. Our results suggest that a deep basal split resulted in the divergence of two groups of Lampropeltis, with one group occupying the upland areas of western United States and most of western and central Mexico, and the other northeastern Mexico and the lowland areas of the southern United States. Results also revealed that the L. mexicana complex and Lampropeltis triangulum are polyphyletic, with taxa from both groups nested together in deeply divergent northern and southern clades. These results are incongruent with previous hypotheses of phylogenetic relationships based on morphology, and suggest that morphological characters shared among the various tri-colored Lampropeltis (e.g., hemipenal structure and tri-colored pattern) may be difficult to interpret phylogenetically.
Sara Ruane - One of the best experts on this subject based on the ideXlab platform.
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DOI:10.1093/sysbio/syt099 Coalescent Species Delimitation in Milksnakes (Genus Lampropeltis) and Impacts on Phylogenetic Comparative Analyses
2016Co-Authors: Sara Ruane, Alexander R Pyron, Robert W. Bryson, T. BurbrinkAbstract:Abstract.—Both gene-tree discordance and unrecognized diversity are sources of error for accurate estimation of species trees, and can affect downstream diversification analyses by obscuring the correct number of nodes, their density, and the lengths of the branches subtending them. Although the theoretical impact of gene-tree discordance on evolutionary analyses has been examined previously, the effect of unsampled and cryptic diversity has not. Here, we examine how delimitation of previously unrecognized diversity in the milksnake (Lampropeltis triangulum) and use of a species-tree approach affects both estimation of the Lampropeltis phylogeny and comparative analyses with respect to the timing of diversification. Coalescent species delimitation indicates that L. triangulum is not monophyletic and that there are multiple species of milksnake, which increases the known species diversity in the genus Lampropeltis by 40%. Both genealogical and temporal discordance occurs between gene trees and the species tree, with evidence that mitochondrial DNA (mtDNA
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ND4 nexus file
2016Co-Authors: Edward A. Myers, Richard E Staub, Javier A. Rodríguez-robles, Alyssa Stropoli, Sara Ruane, Frank T BurbrinkAbstract:Aligned ND4 locus originally from Rodríguez-Robles JA, DeNardo DF, Staub RE (1999) Phylogeography of the California mountain kingsnake, Lampropeltis zonata (Colubridae). Molecular Ecology 8, 1923-1934
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independent demographic responses to climate change among temperate and tropical milksnakes colubridae genus Lampropeltis
PLOS ONE, 2015Co-Authors: Frank T Burbrink, Sara Ruane, Omar TorrescarvajalAbstract:The effects of Late Quaternary climate change have been examined for many temperate New World taxa, but the impact of Pleistocene glacial cycles on Neotropical taxa is less well understood, specifically with respect to changes in population demography. Here, we examine historical demographic trends for six species of milksnake with representatives in both the temperate and tropical Americas to determine if species share responses to climate change as a taxon or by area (i.e., temperate versus tropical environments). Using a multilocus dataset, we test for the demographic signature of population expansion and decline using non-genealogical summary statistics, as well as coalescent-based methods. In addition, we determine whether range sizes are correlated with effective population sizes for milksnakes. Results indicate that there are no identifiable trends with respect to demographic response based on location, and that species responded to changing climates independently, with tropical taxa showing greater instability. There is also no correlation between range size and effective population size, with the largest population size belonging to the species with the smallest geographic distribution. Our study highlights the importance of not generalizing the demographic histories of taxa by region and further illustrates that the New World tropics may not have been a stable refuge during the Pleistocene.
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Approximate complete range size, sample range size, mean and median effective population size and number of size changes for six species of Lampropeltis.
2015Co-Authors: Sara Ruane, Omar Torres-carvajal, Frank T BurbrinkAbstract:The 95% highest posterior density (HPD) is shown for each in parentheses; for number of size changes, species that had non-zero HPDs are indicated (*)Approximate complete range size, sample range size, mean and median effective population size and number of size changes for six species of Lampropeltis.
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coalescent species delimitation in milksnakes genus Lampropeltis and impacts on phylogenetic comparative analyses
Systematic Biology, 2014Co-Authors: Alexander R Pyron, Frank T Burbrink, Sara Ruane, Robert W. BrysonAbstract:Both gene-tree discordance and unrecognized diversity are sources of error for accurate estimation of species trees, and can affect downstream diversification analyses by obscuring the correct number of nodes, their density, and the lengths of the branches subtending them. Although the theoretical impact of gene-tree discordance on evolutionary analyses has been examined previously, the effect of unsampled and cryptic diversity has not. Here, we examine how delimitation of previously unrecognized diversity in the milksnake (Lampropeltis triangulum) and use of a species-tree approach affects both estimation of the Lampropeltis phylogeny and comparative analyses with respect to the timing of diversification. Coalescent species delimitation indicates that L. triangulum is not monophyletic and that there are multiple species of milksnake, which increases the known species diversity in the genus Lampropeltis by 40%. Both genealogical and temporal discordance occurs between gene trees and the species tree, with evidence that mitochondrial DNA (mtDNA) introgression is a main factor. This discordance is further manifested in the preferred models of diversification, where the concatenated gene tree strongly supports an early burst of speciation during the Miocene, in contrast to species-tree estimates where diversification follows a birth-death model and speciation occurs mostly in the Pliocene and Pleistocene. This study highlights the crucial interaction among coalescent-based phylogeography and species delimitation, systematics, and species diversification analyses. (Divergence-time estimation; diversification rates; Lampropeltini; gene-tree/species- tree discordance; mtDNA introgression; Pleistocene diversification.)
Stanislav N Gorb - One of the best experts on this subject based on the ideXlab platform.
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long term low friction maintenance and wear reduction on the ventral scales in snakes
Materials Letters, 2021Co-Authors: J C Sanchezlopez, Clemens F Schaber, Stanislav N GorbAbstract:Abstract Snake skins evolved to withstand permanent friction and wear during sliding. Here, the microstructure of ventral scales of the snake Lampropeltis getula californiae was analyzed using scanning electron microscopy, and the long-term dynamic friction behavior was investigated by reciprocating sliding friction tests. A smooth epoxy resin with similar elasticity modulus and hardness was used for comparison purposes. Strong differences in frictional and wear mechanisms between the two materials were revealed in spite of similar mechanical properties. Snake skin showed a considerably lower frictional coefficient that kept stable over several thousands of sliding cycles. A reduction of the stick-slip behavior was also denoted by analyzing the variation of the friction coefficient in the forward and reverse motion influencing the wear mechanism. This frictional behavior can be explained by three different but complementary mechanisms: fibrous layered composite material of the skin with a gradient of material properties, surface microstructure, and the presence of ordered layers of lipid molecules at the skin surface.
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dry friction of microstructured polymer surfaces inspired by snake skin
Beilstein Journal of Nanotechnology, 2014Co-Authors: Martina Baum, Lars Heepe, Elena Fadeeva, Stanislav N GorbAbstract:The microstructure investigated in this study was inspired by the anisotropic microornamentation of scales from the ventral body side of the California King Snake (Lampropeltis getula californiae). Frictional properties of snake-inspired microstructured polymer surface (SIMPS) made of epoxy resin were characterised in contact with a smooth glass ball by a microtribometer in two perpendicular directions. The SIMPS exhibited a considerable frictional anisotropy: Frictional coefficients measured along the microstructure were about 33% lower than those measured in the opposite direction. Frictional coefficients were compared to those obtained on other types of surface microstructure: (i) smooth ones, (ii) rough ones, and (iii) ones with periodic groove-like microstructures of different dimensions. The results demonstrate the existence of a common pattern of interaction between two general effects that influence friction: (1) molecular interaction depending on real contact area and (2) the mechanical interlocking of both contacting surfaces. The strongest reduction of the frictional coefficient, compared to the smooth reference surface, was observed at a medium range of surface structure dimensions suggesting a trade-off between these two effects.
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Anisotropic Friction of the Ventral Scales in the Snake Lampropeltis getula californiae
Tribology Letters, 2014Co-Authors: Martina J. Baum, Alexander E. Kovalev, Jan Michels, Stanislav N GorbAbstract:Since the ventral body side of snakes is in almost continuous contact with the substrate during undulating locomotion, their skin is presumably adapted to generate high friction for propulsion and low friction to slide along the substrate. In this study, the microstructure of ventral scales was analyzed using scanning electron microscopy, atomic force microscope and confocal laser scanning microscopy. Dynamic friction was investigated by a microtribometer. The ventral scales demonstrated anisotropic frictional properties. To analyze the role of the stiffness of underlying layers on the frictional anisotropy, two different types of scale cushioning (hard and soft) were tested. To estimate frictional forces of the skin surface on rough substrates, additional measurements with a rough surface were performed. Frictional anisotropy for both types of scale cushioning and rough surfaces was revealed. However, for both types of surface roughness, the anisotropy was stronger expressed in the soft-cushioned sample. This effect could be caused by (1) the stronger interaction of the microstructure with the substrate in soft-cushioned samples due to larger real contact area with the substrate and (2) the composite character of the skin of this snake species with embedded, highly ordered fiber-like structures, which may cause anisotropy in material properties.
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Friction behavior of a microstructured polymer surface inspired by snake skin.
Beilstein Journal of Nanotechnology, 2014Co-Authors: Martina Baum, Lars Heepe, Stanislav N GorbAbstract:The aim of this study was to understand the influence of microstructures found on ventral scales of the biological model, Lampropeltis getula californiae, the California King Snake, on the friction behavior. For this purpose, we compared snake-inspired anisotropic microstructured surfaces to other microstructured surfaces with isotropic and anisotropic geometry. To exclude that the friction measurements were influenced by physico-chemical variations, all friction measurements were performed on the same epoxy polymer. For frictional measurements a microtribometer was used. Original data were processed by fast Fourier transformation (FFT) with a zero frequency related to the average friction and other peaks resulting from periodic stick-slip behavior. The data showed that the specific ventral surface ornamentation of snakes does not only reduce the frictional coefficient and generate anisotropic frictional properties, but also reduces stick-slip vibrations during sliding, which might be an adaptation to reduce wear. Based on this extensive comparative study of different microstructured polymer samples, it was experimentally demonstrated that the friction-induced stick-slip behavior does not solely depend on the frictional coefficient of the contact pair.
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epidermis architecture and material properties of the skin of four snake species
Journal of the Royal Society Interface, 2012Co-Authors: Mariechristin G Klein, Stanislav N GorbAbstract:On the basis of structural and experimental data, it was previously demonstrated that the snake integument consists of a hard, robust, inflexible outer surface (Oberhautchen and β-layer) and softer, flexible inner layers (α-layers). It is not clear whether this phenomenon is a general adaptation of snakes to limbless locomotion or only to specific conditions, such as habitat and locomotion. The aim of the present study was to compare the structure and material properties of the outer scale layers (OSLs) and inner scale layers (ISLs) of the exuvium epidermis in four snake species specialized to live in different habitats: Lampropeltis getula californiae (terrestrial), Epicrates cenchria cenchria (generalist), Morelia viridis (arboreal) and Gongylophis colubrinus (sand-burrowing). Scanning electron microscopy (SEM) of skin cross sections revealed a strong variation in the epidermis structure between species. The nanoindentation experiments clearly demonstrated a gradient of material properties along the epidermis in the integument of all the species studied. The presence of such a gradient is a possible adaptation to locomotion and wear minimization on natural substrates. In general, the difference in both the effective elastic modulus and hardness of the OSL and ISL between species was not large compared with the difference in epidermis thickness and architecture.
