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Linden TJ, Burtner AE, Rickman J, McFeely A, Santana SE, Law CJ. Scaling patterns of body plans differ among squirrel ecotypes. PeerJ 2023; 11:e14800. [PMID: 36718452 PMCID: PMC9884040 DOI: 10.7717/peerj.14800] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Accepted: 01/04/2023] [Indexed: 01/26/2023] Open
Abstract
Body size is often hypothesized to facilitate or constrain morphological diversity in the cranial, appendicular, and axial skeletons. However, how overall body shape scales with body size (i.e., body shape allometry) and whether these scaling patterns differ between ecological groups remains poorly investigated. Here, we test whether and how the relationships between body shape, body size, and limb lengths differ among species with different locomotor specializations, and describe the underlying morphological components that contribute to body shape evolution among squirrel (Sciuridae) ecotypes. We quantified the body size and shape of 87 squirrel species from osteological specimens held at museum collections. Using phylogenetic comparative methods, we first found that body shape and its underlying morphological components scale allometrically with body size, but these allometric patterns differ among squirrel ecotypes: chipmunks and gliding squirrels exhibited more elongate bodies with increasing body sizes whereas ground squirrels exhibited more robust bodies with increasing body size. Second, we found that only ground squirrels exhibit a relationship between forelimb length and body shape, where more elongate species exhibit relatively shorter forelimbs. Third, we found that the relative length of the ribs and elongation or shortening of the thoracic region contributes the most to body shape evolution across squirrels. Overall, our work contributes to the growing understanding of mammalian body shape evolution and how it is influenced by body size and locomotor ecology, in this case from robust subterranean to gracile gliding squirrels.
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Affiliation(s)
- Tate J. Linden
- University of Washington, Seattle, WA, United States of America
| | | | | | - Annika McFeely
- University of Washington, Seattle, WA, United States of America
| | | | - Chris J. Law
- University of Washington, Seattle, WA, United States of America,University of Texas at Austin, Austin, TX, United States of America,American Museum of Natural History, New York, NY, United States of America
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2
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Müller MA, Merten LJF, Böhmer C, Nyakatura JA. Pushing the boundary? Testing the "functional elongation hypothesis" of the giraffe's neck. Evolution 2021; 75:641-655. [PMID: 33443310 DOI: 10.1111/evo.14171] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Revised: 01/07/2021] [Accepted: 01/08/2021] [Indexed: 11/28/2022]
Abstract
Although giraffes maintain the usual mammalian cervical number of seven vertebrae, their first thoracic vertebra (T1) exhibits aberrant anatomy and has been hypothesized to functionally elongate the neck. We test this "functional elongation hypothesis" by combining phylogenetically informed analyses of neck length, three-dimensional (3D) vertebral shape, and of the functional significance of shape differences across a broad sample of ruminants and camelids. Digital bone models of the cervicothoracic transition were subjected to 3D geometric morphometric analysis revealing how the shape of the seventh cervical (C7) has converged in several long-necked species. However, we find a unique "cervicalization" of the giraffe's T1. In contrast, we demonstrate a "thoracalization" of C7 for the European bison. Other giraffids (okapi and extinct Sivatherium) did not exhibit "cervicalized" T1 morphology. Quantitative range of motion (ROM) analysis at the cervicothoracic transition in ruminants and camelids confirms the "functional elongation hypothesis" for the giraffe in terms of increased mobility, especially with regard to dorsoventral flexion/extension. Additionally, other factors related to the unique morphology of the giraffe's cervicothoracic transition such as neck posture and intervertebral stability are discussed and should be considered in future studies of giraffe neck evolution.
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Affiliation(s)
- Marilena A Müller
- AG Vergleichende Zoologie, Institut für Biologie, Humboldt-Universität zu Berlin, Berlin, 10115, Germany
| | - Luisa J F Merten
- AG Vergleichende Zoologie, Institut für Biologie, Humboldt-Universität zu Berlin, Berlin, 10115, Germany
| | - Christine Böhmer
- UMR 7179 CNRS/MNHN, Département Adaptations du Vivant, Muséum National d'Histoire Naturelle, Paris, 75005, France.,Department für Geo- und Umweltwissenschaften und GeoBio-Center, Ludwig-Maximilians-Universität München, München, 80333, Germany
| | - John A Nyakatura
- AG Vergleichende Zoologie, Institut für Biologie, Humboldt-Universität zu Berlin, Berlin, 10115, Germany
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3
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Hou S, Cydylo M, Danowitz M, Solounias N. Comparisons of Schansitherium tafeli with Samotherium boissieri (Giraffidae, Mammalia) from the Late Miocene of Gansu Province, China. PLoS One 2019; 14:e0211797. [PMID: 30753231 PMCID: PMC6376930 DOI: 10.1371/journal.pone.0211797] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Accepted: 01/21/2019] [Indexed: 12/02/2022] Open
Abstract
We are describing and figuring for the first time skulls of
Schansitherium tafeli, which are abundant in the Gansu area
of China from the Late Miocene. They were animals about the size of
Samotherium with shorter necks that had two pairs of
ossicones that merge at the base, which is unlike Samotherium.
The anterior ossicones consist of anterior lineations, which may represent
growth lines. They were likely mixed feeders similar to
Samotherium. Schansitherium is tentatively
placed in a very close position to Samotherium.
Samotherium and Schansitherium represent a
pair of morphologically very similar species that likely coexisted similarly to
pairs of modern species, where the main difference is in the ossicones. Pairs of
ruminants in Africa, for example, exist today that differ mostly in their horn
shape but otherwise are similar in size, shape, and diet. The absence of
Schansitherium from Europe is interesting, however, as
Samotherium is found in both locations. While is it
challenging to interpret neck length and ossicone shape in terms of function in
combat, we offer our hypothesis as to how the two species differed in their
fighting techniques.
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Affiliation(s)
- Sukuan Hou
- Key Laboratory of Vertebrate Evolution and Human Origins of Chinese
Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology,
Chinese Academy of Sciences, Beijing, China
- CAS Center for Excellence in Life and Paleoenvironment, Beijing,
China
- College of Earth and Planetary Sciences, University of Chinese Academy of
Sciences, Beijing, China
- * E-mail:
| | - Michael Cydylo
- Department of Anatomy, New York Institute of Technology College of
Osteopathic Medicine, Old Westbury, NY, United States of
America
| | - Melinda Danowitz
- Department of Pediatrics, Alfred I. duPont Hospital for Children,
Wilmington, DE, United States of America
| | - Nikos Solounias
- Department of Anatomy, New York Institute of Technology College of
Osteopathic Medicine, Old Westbury, NY, United States of
America
- Department of Paleontology, American Museum of Natural History, New York,
NY, United States of America
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4
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Ríos M, Sánchez IM, Morales J. A new giraffid (Mammalia, Ruminantia, Pecora) from the late Miocene of Spain, and the evolution of the sivathere-samothere lineage. PLoS One 2017; 12:e0185378. [PMID: 29091914 PMCID: PMC5665556 DOI: 10.1371/journal.pone.0185378] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Accepted: 08/31/2017] [Indexed: 11/19/2022] Open
Abstract
Giraffids include the only living giraffomorph ruminants and are diagnosed by the presence of bi-lobed canines and a special type of epiphyseal cranial appendages called ossicones. The family Giraffidae ranges from the latest early Miocene until today. However they are currently extant relics with only two living representatives, the African genera Okapia and Giraffa. Giraffids were much more diverse and widespread in the past, with more than 30 fossil species described. For the past decades a number of studies intended to resolve the phylogenetic relationships of the family, but due to the lack of really good cranial material no clear consensus was reached regarding the phylogenetic relationships amongst the different members of the group. The exceptionally complete remains of a new large giraffid from the late Miocene of Spain, Decennatherium rex sp. nov., allows us to improve and reassess giraffid systematics, offering a lot of new data, both anatomic and phylogenetic, on the large late Miocene giraffids of Eurasia. The results of our cladistic analysis show Decennatherium as a basal offshoot of a clade containing the gigantic samotheres and sivatheres, characterized by the presence of a Sivatherium-like ossicone-plan among other features. Decennatherium thus offers the most ancient evidence of this Sivatherium-plan and firmly establishes the early morphological patterns of evolution of a sivathere / samothere-clade that is defined as the less inclusive clade that contains Decennatherium and Sivatherium. Finally, this large group of four-ossiconed giraffids evolutionarily links Miocene Europe and Africa indicating vicariance / migration processes among the giraffid genetic pools separated by the Mediterranean Sea.
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Affiliation(s)
- María Ríos
- Departamento de Paleobiología, Museo Nacional de Ciencias Naturales-CSIC, Madrid, Spain
- * E-mail:
| | - Israel M. Sánchez
- Departmento de Faunas del Neógeno y Cuaternario, Institut Català de Paleontologia- Miquel Crusafont, Barcelona, Spain
| | - Jorge Morales
- Departamento de Paleobiología, Museo Nacional de Ciencias Naturales-CSIC, Madrid, Spain
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Suzuki TK. On the Origin of Complex Adaptive Traits: Progress Since the Darwin Versus Mivart Debate. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2017; 328:304-320. [PMID: 28397400 DOI: 10.1002/jez.b.22740] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Revised: 03/02/2017] [Accepted: 03/07/2017] [Indexed: 01/12/2023]
Abstract
The evolutionary origin of complex adaptive traits has been a controversial topic in the history of evolutionary biology. Although Darwin argued for the gradual origins of complex adaptive traits within the theory of natural selection, Mivart insisted that natural selection could not account for the incipient stages of complex traits. The debate starting from Darwin and Mivart eventually engendered two opposite views: gradualism and saltationism. Although this has been a long-standing debate, the issue remains unresolved. However, recent studies have interrogated classic examples of complex traits, such as the asymmetrical eyes of flatfishes and leaf mimicry of butterfly wings, whose origins were debated by Darwin and Mivart. Here, I review recent findings as a starting point to provide a modern picture of the evolution of complex adaptive traits. First, I summarize the empirical evidence that unveils the evolutionary steps toward complex traits. I then argue that the evolution of complex traits could be understood within the concept of "reducible complexity." Through these discussions, I propose a conceptual framework for the formation of complex traits, named as reducible-composable multicomponent systems, that satisfy two major characteristics: reducibility into a sum of subcomponents and composability to construct traits from various additional and combinatorial arrangements of the subcomponents. This conceptual framework provides an analytical foundation for exploring evolutionary pathways to build up complex traits. This review provides certain essential avenues for deciphering the origin of complex adaptive traits.
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Affiliation(s)
- Takao K Suzuki
- Transgenic Silkworm Research Unit, Division of Biotechnology, Institute of Agrobiological Sciences, NARO, Ibaraki, 305-8634, Japan
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Williams EM. Giraffe Stature and Neck Elongation: Vigilance as an Evolutionary Mechanism. BIOLOGY 2016; 5:biology5030035. [PMID: 27626454 PMCID: PMC5037354 DOI: 10.3390/biology5030035] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 09/02/2016] [Accepted: 09/07/2016] [Indexed: 11/16/2022]
Abstract
Giraffe (Giraffa camelopardalis), with their long neck and legs, are unique amongst mammals. How these features evolved is a matter of conjecture. The two leading ideas are the high browse and the sexual-selection hypotheses. While both explain many of the characteristics and the behaviour of giraffe, neither is fully supported by the available evidence. The extended viewing horizon afforded by increased height and a need to maintain horizon vigilance, as a mechanism favouring the evolution of increased height is reviewed. In giraffe, vigilance of predators whilst feeding and drinking are important survival factors, as is the ability to interact with immediate herd members, young and male suitors. The evidence regarding giraffe vigilance behaviour is sparse and suggests that over-vigilance has a negative cost, serving as a distraction to feeding. In woodland savannah, increased height allows giraffe to see further, allowing each giraffe to increase the distance between its neighbours while browsing. Increased height allows the giraffe to see the early approach of predators, as well as bull males. It is postulated that the wider panorama afforded by an increase in height and longer neck has improved survival via allowing giraffe to browse safely over wider areas, decreasing competition within groups and with other herbivores.
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Affiliation(s)
- Edgar M Williams
- Faculty of Life Sciences and Education, University of South Wales, Wales CF37 1DL, UK; ; Tel.: +44-1443-483-893.
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Solounias N, Danowitz M. Astragalar Morphology of Selected Giraffidae. PLoS One 2016; 11:e0151310. [PMID: 27028515 PMCID: PMC4814102 DOI: 10.1371/journal.pone.0151310] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Accepted: 02/28/2016] [Indexed: 11/23/2022] Open
Abstract
The artiodactyl astragalus has been modified to exhibit two trochleae, creating a double pullied structure allowing for significant dorso-plantar motion, and limited mediolateral motion. The astragalus structure is partly influenced by environmental substrates, and correspondingly, morphometric studies can yield paleohabitat information. The present study establishes terminology and describes detailed morphological features on giraffid astragali. Each giraffid astragalus exhibits a unique combination of anatomical characteristics. The giraffid astragalar morphologies reinforce previously established phylogenetic relationships. We find that the enlargement of the navicular head is a feature shared by all giraffids, and that the primitive giraffids possess exceptionally tall astragalar heads in relation to the total astragalar height. The sivatheres and the okapi share a reduced notch on the lateral edge of the astragalus. We find that Samotherium is more primitive in astragalar morphologies than Palaeotragus, which is reinforced by tooth characteristics and ossicone position. Diagnostic anatomical characters on the astragalus allow for giraffid species identifications and a better understanding of Giraffidae.
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Affiliation(s)
- Nikos Solounias
- Department of Anatomy, New York Institute of Technology College of Osteopathic Medicine, Old Westbury, NY, United States of America
- Department of Paleontology, American Museum of Natural History, Central Park West at 79 Street, New York, NY, United States of America
- * E-mail:
| | - Melinda Danowitz
- Department of Anatomy, New York Institute of Technology College of Osteopathic Medicine, Old Westbury, NY, United States of America
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