Using a biologically mimicking climbing robot to explore the performance landscape of climbing in lizards

AbstractThe life and death of an organism often depends on its ability to perform well at some ecologically relevant task. Yet despite this significance we have little idea how well species are optimised for competing locomotor tasks. Most scientists generally accept that the ability for natural systems to become optimised for a specific task is limited by structural, historic or functional constraints. Climbing lizards provide a good example of constraint where climbing ability requires the optimization of conflicting tasks such as speed, stability, or efficiency. Here we reconstruct multiple performance landscapes of climbing locomotion using a 10-DOF robot based upon the lizard bauplan, including an actuated spine, shoulders, and feet, the latter which interlock with the surface via claws. This design allows us to independently vary speed, foot angles, and range of motion, while simultaneously collecting data on climbed distance, stability and efficiency. We first demonstrate a trade-off between speed and stability with high speeds resulting in decreased stability and low speeds an increased cost of transport. By varying foot orientation of fore and hindfeet independently, we found geckos converge on a narrow optimum for both speed and stability, but avoid a secondary wider optimum highlighting a possible constraint. Modifying the spine and limb range of movement revealed a gradient in performance. Evolutionary modifications in movement among extant species appear to follow this gradient towards areas which promote speed and efficiency. This approach can give us a better understanding about locomotor optimization, and provide inspiration for industrial and search-and-rescue robots.Significance StatementClimbing requires the optimization of conflicting tasks such as speed, stability, or efficiency, but understanding the relative importance of these competing performance traits is difficult.We used a highly modular bio-inspired climbing robot to reconstruct performance landscapes for climbing lizards. We then compared the performance of extant species onto these and show strong congruence with lizard phenotypes and robotic optima.Using this method we can show why certain phenotypes are not present among extant species, illustrating why these would be potentially mal-adaptive.These principles may be useful to compare with relative rates of evolution along differing evolutionary histories. It also highlights the importance of biological inspiration towards the optimization of industrial climbing robots, which like lizards, must negotiate complex environments.

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Using a biologically mimicking climbing robot to explore the performance landscape of climbing in lizards

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2020.2576 ◽

2021 ◽

Vol 288 (1947) ◽

Author(s):

Johanna T. Schultz ◽

Hendrik K. Beck ◽

Tina Haagensen ◽

Tasmin Proost ◽

Christofer J. Clemente

Keyword(s):

Functional Constraints ◽

Climbing Robot ◽

Cost Of Transport ◽

Performance Tasks ◽

Natural Systems ◽

High Speeds ◽

Extant Species ◽

Climbing Ability ◽

The Cost ◽

Relative Weighting

Locomotion is a key aspect associated with ecologically relevant tasks for many organisms, therefore, survival often depends on their ability to perform well at these tasks. Despite this significance, we have little idea how different performance tasks are weighted when increased performance in one task comes at the cost of decreased performance in another. Additionally, the ability for natural systems to become optimized to perform a specific task can be limited by structural, historic or functional constraints. Climbing lizards provide a good example of these constraints as climbing ability likely requires the optimization of tasks which may conflict with one another such as increasing speed, avoiding falls and reducing the cost of transport (COT). Understanding how modifications to the lizard bauplan can influence these tasks may allow us to understand the relative weighting of different performance objectives among species. Here, we reconstruct multiple performance landscapes of climbing locomotion using a 10 d.f. robot based upon the lizard bauplan, including an actuated spine, shoulders and feet, the latter which interlock with the surface via claws. This design allows us to independently vary speed, foot angles and range of motion (ROM), while simultaneously collecting data on climbed distance, stability and efficiency. We first demonstrate a trade-off between speed and stability, with high speeds resulting in decreased stability and low speeds an increased COT. By varying foot orientation of fore- and hindfeet independently, we found geckos converge on a narrow optimum of foot angles (fore 20°, hind 100°) for both speed and stability, but avoid a secondary wider optimum (fore −20°, hind −50°) highlighting a possible constraint. Modifying the spine and limb ROM revealed a gradient in performance. Evolutionary modifications in movement among extant species over time appear to follow this gradient towards areas which promote speed and efficiency.

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A bio-inspired robotic climbing robot to understand kinematic and morphological determinants for an optimal climbing gait

Bioinspiration & Biomimetics ◽

10.1088/1748-3190/ac370f ◽

2021 ◽

Author(s):

Hendrik Beck ◽

Johanna J Schultz ◽

Christofer J Clemente

Keyword(s):

Optimal Parameter ◽

Legged Locomotion ◽

Robotic Systems ◽

Climbing Robot ◽

Kinematic Parameters ◽

Phase Dynamics ◽

Complex Interactions ◽

Optimal Dynamic ◽

Speed Stability ◽

Robotic Applications

Abstract Robotic systems for complex tasks, such as search and rescue or exploration, are limited for wheeled designs, thus the study of legged locomotion for robotic applications has become increasingly important. To successfully navigate in regions with rough terrain, a robot must not only be able to negotiate obstacles, but also climb steep inclines. Following the principles of biomimetics, we developed a modular bio-inspired climbing robot, named X4, which mimics the lizard’s bauplan including an actuated spine, shoulders, and feet which interlock with the surface via claws. We included the ability to modify gait and hardware parameters and simultaneously collect data with the robot’s sensors on climbed distance, slip occurrence and efficiency. We first explored the speed-stability trade-off and its interaction with limb swing phase dynamics, finding a sigmoidal pattern of limb movement resulted in the greatest distance travelled. By modifying foot orientation, we found two optima for both speed and stability, suggesting multiple stable configurations. We varied spine and limb range of motion, again showing two possible optimum configurations, and finally varied the centre of pro- and retraction on climbing performance, showing an advantage for protracted limbs during the stride. We then stacked optimal regions of performance and show that combining optimal dynamic patterns with either foot angles or ROM configurations have the greatest performance, but further optima stacking resulted in a decrease in performance, suggesting complex interactions between kinematic parameters. The search of optimal parameter configurations might not only be beneficial to improve robotic in-field operations but may also further the study of the locomotive evolution of climbing of animals, like lizards or insects.

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Slowly but surely: gradual diversification and phenotypic evolution in the hyper-diverse tree fern family Cyatheaceae

Annals of Botany ◽

10.1093/aob/mcz145 ◽

2019 ◽

Vol 125 (1) ◽

pp. 93-103

Author(s):

Oriane Loiseau ◽

Anna Weigand ◽

Sarah Noben ◽

Jonathan Rolland ◽

Daniele Silvestro ◽

...

Keyword(s):

Species Richness ◽

Taxonomic Diversity ◽

Tree Fern ◽

Rates Of Evolution ◽

Extant Species ◽

The Family ◽

History Of ◽

Rapid Diversification ◽

The Tropics ◽

Diverse Groups

Abstract Background and Aims The tremendously unbalanced distribution of species richness across clades in the tree of life is often interpreted as the result of variation in the rates of diversification, which may themselves respond to trait evolution. Even though this is likely a widespread pattern, not all diverse groups of organisms exhibit heterogeneity in their dynamics of diversification. Testing and characterizing the processes driving the evolution of clades with steady rates of diversification over long periods of time are of importance in order to have a full understanding of the build-up of biodiversity through time. Methods We studied the macroevolutionary history of the species-rich tree fern family Cyatheaceae and inferred a time-calibrated phylogeny of the family including extinct and extant species using the recently developed fossilized birth–death method. We tested whether the high diversity of Cyatheaceae is the result of episodes of rapid diversification associated with phenotypic and ecological differentiation or driven by stable but low rates of diversification. We compared the rates of diversification across clades, modelled the evolution of body size and climatic preferences and tested for trait-dependent diversification. Key Results This ancient group diversified at a low and constant rate during its long evolutionary history. Morphological and climatic niche evolution were found to be overall highly conserved, although we detected several shifts in the rates of evolution of climatic preferences, linked to changes in elevation. The diversification of the family occurred gradually, within limited phenotypic and ecological boundaries, and yet resulted in a remarkable species richness. Conclusions Our study indicates that Cyatheaceae is a diverse clade which slowly accumulated morphological, ecological and taxonomic diversity over a long evolutionary period and provides a compelling example of the tropics as a museum of biodiversity.

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Adaptive evolution toward larger size in mammals

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1419823112 ◽

2015 ◽

Vol 112 (16) ◽

pp. 5093-5098 ◽

Cited By ~ 59

Author(s):

Joanna Baker ◽

Andrew Meade ◽

Mark Pagel ◽

Chris Venditti

Keyword(s):

Body Size ◽

Large Body ◽

Biological Species ◽

Directional Bias ◽

Rates Of Evolution ◽

Extant Species ◽

Size Evolution ◽

Mammalian Fossil ◽

Cope’S Rule

The notion that large body size confers some intrinsic advantage to biological species has been debated for centuries. Using a phylogenetic statistical approach that allows the rate of body size evolution to vary across a phylogeny, we find a long-term directional bias toward increasing size in the mammals. This pattern holds separately in 10 of 11 orders for which sufficient data are available and arises from a tendency for accelerated rates of evolution to produce increases, but not decreases, in size. On a branch-by-branch basis, increases in body size have been more than twice as likely as decreases, yielding what amounts to millions and millions of years of rapid and repeated increases in size away from the small ancestral mammal. These results are the first evidence, to our knowledge, from extant species that are compatible with Cope’s rule: the pattern of body size increase through time observed in the mammalian fossil record. We show that this pattern is unlikely to be explained by several nonadaptive mechanisms for increasing size and most likely represents repeated responses to new selective circumstances. By demonstrating that it is possible to uncover ancient evolutionary trends from a combination of a phylogeny and appropriate statistical models, we illustrate how data from extant species can complement paleontological accounts of evolutionary history, opening up new avenues of investigation for both.

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Phylogeny and Rates of Character Evolution Among Ringtail Possums (Pseudocheiridae, Marsupialia)

Australian Journal of Zoology ◽

10.1071/zo9930273 ◽

1993 ◽

Vol 41 (3) ◽

pp. 273 ◽

Cited By ~ 9

Author(s):

MS Springer

Keyword(s):

Plant Material ◽

Biochemical Analysis ◽

Sister Taxon ◽

Phylogenetic Position ◽

Rates Of Evolution ◽

Process Plant ◽

Extant Species ◽

Dollo Parsimony ◽

Pseudocheirus Peregrinus ◽

Cladistic Analyses

A total of 47 craniodental characters seen in fossil and extant ringtail possums (Pseudocheiridae: Marsupialia) were examined using Wagner, Camin-Sokal, and Dollo parsimony. All extant species form a clade to the exclusion of Miocene genera. Hemibelideus and Petauroides are sister taxa, as are Petropseudes and Pseudochirops. All species of Pseudocheirus are united together, except Pseudocheirus peregrinus, the phylogenetic position of which is uncertain on the basis of craniodental information. Overall, the agreement between cladistic analyses of craniodental characters and biochemical analysis is excellent, although the latter provide much stronger evidence that P. peregrinus is a sister taxon to other Pseudocheirus species. Rates of evolution of craniodental characters are highest in the Pseudochirops-Petropseudes lineage, where widening of the molars, elaboration of cusps and conules, accentuation of cristae and cristids, and the development of highly crenulated enamel create a dental battery that is better equipped to process plant material. Pseudocheirus displays the least modification of the presumed primitive dental condition.

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Occurrence and biogeographic significance of Heliaster (Echinodermata: Asteroidea) from the Pliocene of southwest Florida

Journal of Paleontology ◽

10.1017/s0022336000058960 ◽

1988 ◽

Vol 62 (01) ◽

pp. 126-132 ◽

Cited By ~ 8

Author(s):

Douglas S. Jones ◽

Roger W. Portell

Keyword(s):

Central American ◽

Eastern Pacific ◽

Whole Body ◽

Marine Fauna ◽

Western Atlantic ◽

Southwest Florida ◽

Extant Species ◽

Geologic Record ◽

Central American Isthmus

Whole body asteroid fossils are rare in the geologic record and previously unreported from the Cenozoic of Florida. However, specimens of the extant species,Heliaster microbrachiusXantus, were recently discovered in upper Pliocene deposits. This marks the first reported fossil occurrence of the monogeneric Heliasteridae, a group today confined to the eastern Pacific. This discovery provides further non-molluscan evidence of the close similarities between the Neogene marine fauna of Florida and the modern fauna of the eastern Pacific. The extinction of the heliasters in the western Atlantic is consistent with the pattern of many other marine groups in the region which suffered impoverishment following uplift of the Central American isthmus.

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Effect of Iron Limitation on the Ultrastructure of Agmenellum Quadruplicatum

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100098551 ◽

1981 ◽

Vol 39 ◽

pp. 410-411

Author(s):

L. P. Hardie ◽

D. L. Balkwill ◽

S. E. Stevens

Keyword(s):

Growth Medium ◽

Green Alga ◽

Natural Habitat ◽

Iron Limitation ◽

Natural Environments ◽

Blue Green Alga ◽

Marine Cyanobacterium ◽

Natural Systems ◽

Thin Sectioning ◽

Agmenellum Quadruplicatum

Agmenellum quadruplicatum is a unicellular, non-nitrogen-fixing, marine cyanobacterium (blue-green alga). The ultrastructure of this organism, when grown in the laboratory with all necessary nutrients, has been characterized thoroughly. In contrast, little is known of its ultrastructure in the specific nutrient-limiting conditions typical of its natural habitat. Iron is one of the nutrients likely to limit this organism in such natural environments. It is also of great importance metabolically, being required for both photosynthesis and assimilation of nitrate. The purpose of this study was to assess the effects (if any) of iron limitation on the ultrastructure of A. quadruplicatum. It was part of a broader endeavor to elucidate the ultrastructure of cyanobacteria in natural systemsActively growing cells were placed in a growth medium containing 1% of its usual iron. The cultures were then sampled periodically for 10 days and prepared for thin sectioning TEM to assess the effects of iron limitation.

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