Functional ecological convergence between the thylacine and small prey-focused canids

Abstract Background Morphological convergence is a fundamental aspect of evolution, allowing for inference of the biology and ecology of extinct species by comparison with the form and function of living species as analogues. The thylacine (Thylacinus cynocephalus), the iconic recently extinct marsupial, is considered a classic example of convergent evolution with the distantly related placental wolf or dog, though almost nothing is actually known regarding its ecology. This lack of data leads to questions regarding the degree of convergence with, and the similarity of, the functional ecology of the thylacine and the wolf/dog. Here, we examined the cranium of the thylacine using 3D geometric morphometrics and two quantitative tests of convergence to more precisely determine convergent analogues, within a phylogenetically informed dataset of 56 comparative species across 12 families of marsupial and placental faunivorous mammals. Using this dataset, we investigated patterns of correlation between cranial shape and diet, phylogeny, and relative prey size across these terrestrial faunivores. Results We find a correlation between cranial, facial, and neurocranial shape and the ratio of prey-to-predator body mass, though neurocranial shape may not correlate with prey size within marsupials. The thylacine was found to group with predators that routinely take prey smaller than 45% of their own body mass, not with predators that take subequal-sized or larger prey. Both convergence tests find significant levels of convergence between the thylacine and the African jackals and South American ‘foxes’, with lesser support for the coyote and red fox. We find little support for convergence between the thylacine and the wolf or dog. Conclusions Our study finds little support for a wolf/dog-like functional ecology in the thylacine, with it instead being most similar to mid-sized canids such as African jackals and South American ‘foxes’ that mainly take prey less than half their size. This work suggests that concepts of convergence should extend beyond superficial similarity, and broader comparisons can lead to false interpretations of functional ecology. The thylacine was a predator of small to mid-sized prey, not a big-game specialist like the placental wolf.

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Convergence, parallelism, and function of extreme parietal callus in diverse groups of Cenozoic Gastropoda

Paleobiology ◽

10.1017/pab.2020.33 ◽

2020 ◽

pp. 1-26

Author(s):

Carlie Pietsch ◽

Brendan M. Anderson ◽

Lauren M. Maistros ◽

Ethan C. Padalino ◽

Warren D. Allmon

Keyword(s):

Body Size ◽

Functional Ecology ◽

Low Density ◽

Shell Microstructure ◽

Shell Surface ◽

Microscopy Imaging ◽

Living Species ◽

Essential Contribution ◽

And Function ◽

Diverse Groups

Abstract We use scanning electron microscopy imaging to examine the shell microstructure of fossil and living species in five families of caenogastropods (Strombidae, Volutidae, Olividae, Pseudolividae, and Ancillariidae) to determine whether parallel or convergent evolution is responsible for the development of a unique caenogastropod trait, the extreme parietal callus (EPC). The EPC is defined as a substantial thickening of both the spire callus and the callus on the ventral shell surface such that it covers 50% or more of the surface. Caenogastropods as a whole construct the EPC convergently, using a variety of low-density, poorly organized microstructures that are otherwise uncommon in caenogastropod non-callus shell construction. Within clades, however, we see evidence for parallelism in decreased regulation in both the shell and callus microstructure. Low-density and poorly ordered microstructure—such as used for the EPC—uses less organic scaffolding and is less energetically expensive than normal shell microstructure. This suggests the EPC functions to rapidly and inexpensively increase shell thickness and overall body size. Tests of functional ecology suggest that the EPC might function both to defend against crushing predation through increased body size and dissipation of forces while aiding in shell orientation of highly mobile gastropods. These interpretations hinge on the current phylogenetic placement of caenogastropod families, emphasizing the essential contribution of phylogeny when interpreting homoplasy.

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Alan Cyril Walker. 23 August 1938—20 November 2017

Biographical Memoirs of Fellows of the Royal Society ◽

10.1098/rsbm.2019.0017 ◽

2019 ◽

Vol 67 ◽

pp. 449-467

Author(s):

Leslea J. Hlusko ◽

Peter S. Ungar

Keyword(s):

Homo Erectus ◽

Early Adopter ◽

Dental Microwear ◽

Form And Function ◽

Microwear Analysis ◽

Living Species ◽

Late Twentieth ◽

And Function ◽

Late Twentieth Century ◽

Bony Morphology

Colleagues often refer to Alan Walker as the Eric Clapton (one of the most influential musicians of the late twentieth century) of palaeoanthropology in recognition of the artistry of his science. His field discoveries filled major gaps in our knowledge of primate evolution, such as elucidating the Miocene world of Proconsul and finding the transitional ‘Black Skull’ of Australopithecus aethiopicus and the skeleton of a Homo erectus boy. In addition to discovering these remarkable fossils, Alan was essential in bringing a palaeobiological approach to the laboratory interpretation of their bony morphology. He used the relationships between form and function in living species as a baseline for understanding the past, he pioneered dental microwear analysis to infer diet and was an early-adopter of the use of microCT to explore the internal structure of primate ear bones. Beyond these scientific accomplishments, however, it was Alan's grace and generosity that truly set him apart from his peers. As the patriarch of an extensive intellectual family of students, postdocs and colleagues, Alan taught by example how to be intellectually creative, brave, meticulous, generous and kind. His legacy will long be felt in both the science and the culture of palaeoanthropology.

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Effects of size, phylogeny and locomotor habits on the pelvic and femoral morphology of South American spiny rats (Rodentia: Echimyidae)

Biological Journal of the Linnean Society ◽

10.1093/biolinnean/blaa150 ◽

2020 ◽

Vol 131 (4) ◽

pp. 835-869

Author(s):

William Corrêa Tavares ◽

Leila Maria Pessôa

Keyword(s):

Body Mass ◽

Phylogenetic Signal ◽

South American ◽

Ecological Diversity ◽

Multivariate Statistical Methods ◽

Multivariate Statistical ◽

Cranial Variation ◽

Selective Pressures ◽

Key Factor ◽

Living Species

Abstract The rodent family Echimyidae (spiny rats, hutias and coypu) is notable for its high phylogenetic and ecological diversity, encompassing ~100 living species with body mass ranging from 70 to 4500 g, including arboreal, epigean (non-arboreal or scansorial), fossorial and semi-aquatic taxa. In view of this diversity, it was hypothesized that echimyid morphological variation in the pelvis and femur should reflect: (1) allometric association with body mass; (2) morphofunctional specializations for the different locomotor habits; and (3) phylogenetic history. To test these propositions, we examined 30 echimyid species, in addition to eight species of two other octodontoid families, Abrocomidae and Octodontidae. Pelvic and femoral variation was assessed with linear morphometry, using bivariate and multivariate statistical methods, part of which was phylogenetically informed. Approximately 80% of the total variation among echimyids was explained by body mass, and some univariate measurements were found potentially to be effective as body mass estimators after simple allometric procedures, notably in the pelvis. Even considering the significant phylogenetic signal, variation in shape was largely structured by locomotor habits, mainly in the pelvis, suggesting that the echimyid hindlimb diversification was driven, in part, by selective pressures related to locomotor habits. Finally, echimyid femoral disparity was considerably greater than in other octodontoids, contrasting with their relatively modest cranial variation. Thus, this study suggests that hindlimb diversity constitutes a key factor for the exceptional echimyid ecological and phyletic diversification.

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Righting time versus shell size and shape dimorphism in adult Hermann’s tortoises: Field observations meet theoretical predictions

Animal Biology ◽

10.1163/15707563-00002420 ◽

2013 ◽

Vol 63 (4) ◽

pp. 381-396 ◽

Cited By ~ 5

Author(s):

Dragana Stojadinović ◽

Ðurađ Milošević ◽

Jelka Crnobrnja-Isailović

Keyword(s):

Body Mass ◽

Geometric Modeling ◽

Interdisciplinary Approach ◽

Width Ratio ◽

Shape Variation ◽

Shell Size ◽

Form And Function ◽

Righting Response ◽

And Function ◽

The Impact

We investigated the relation between righting time (RT) and carapace morphology in 303 adult Hermann’s tortoises (Testudo hermanni Gmelin, 1789) from two geographically close localities. Their size, shape and body mass, adjusted for size, were significantly different between males and females. Righting time differed among the populations and was related to the ambient temperature and the relative body mass and carapace shape. However, analysis showed that the impact of carapace “form” (shape plus relative body mass) alone had only moderate influence on the variation in righting time (“function”). Both “form” and “function” did not contribute much to the segregation of individuals in geometric space, based on either sex or locality. An interesting detail was that tortoises with a height/width ratio of the shell contour higher than 0.75 had quite a short righting time (less than 100 seconds), which is in accordance with the proposed theoretical model of energy balance of righting in chelonians. We suppose that interactions between general carapace “form”, specific components of shell structure, physiological parameters and local environments shape variation in righting response in this species. An interdisciplinary approach combining geometric modeling with traditional biological disciplines would be needed to support this hypothesis.

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Scanning tunneling microscopy (STM) of DNA and RNA

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100152148 ◽

1989 ◽

Vol 47 ◽

pp. 34-35

Author(s):

Patricia G. Arscott ◽

Gil Lee ◽

Victor A. Bloomfield ◽

D. Fennell Evans

Keyword(s):

Molecular Structures ◽

Inorganic Materials ◽

Resolving Power ◽

Scanning Tunneling ◽

Tunneling Microscopy ◽

Form And Function ◽

Dna And Rna ◽

Calf Thymus ◽

And Function ◽

The Relationship

STM is one of the most promising techniques available for visualizing the fine details of biomolecular structure. It has been used to map the surface topography of inorganic materials in atomic dimensions, and thus has the resolving power not only to determine the conformation of small molecules but to distinguish site-specific features within a molecule. That level of detail is of critical importance in understanding the relationship between form and function in biological systems. The size, shape, and accessibility of molecular structures can be determined much more accurately by STM than by electron microscopy since no staining, shadowing or labeling with heavy metals is required, and there is no exposure to damaging radiation by electrons. Crystallography and most other physical techniques do not give information about individual molecules.We have obtained striking images of DNA and RNA, using calf thymus DNA and two synthetic polynucleotides, poly(dG-me5dC)·poly(dG-me5dC) and poly(rA)·poly(rU).

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