Causal explanations for the evolution of ‘low gear’ locomotion in insular ruminants

Rozzi, Roberto; Varela, Sara; Bover, Pere Rosselló; Martin, Jeff M.

doi:10.1111/jbi.13942

Cited by 11 publications

(13 citation statements)

References 72 publications

(126 reference statements)

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“…Sondaar (1977) described that decrease in speed as a “low gear locomotion.” However, the shortening of the metapodials was not the only reason for the reduced speed in insular ungulates. The ecological conditions of the Mediterranean islands, consisting of poor species diversity faunas characterized by the absence of predators, likely led to the speed reduction in Cypriot hippo (Rozzi et al, 2020).…”

Section: Discussionmentioning

confidence: 99%

Functional morphology of the hindlimb of fossilized pygmy hippopotamus from Ayia Napa (Cyprus)

Georgitsis

Liakopoulou

Θεοδώρου

et al. 2022

Journal of Morphology

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We studied the functional morphology of the postcranial skeleton of the endemic hippopotamus Phanourios minor, derived from the Upper Pleistocene site of Ayia Napa. The deposit, which consists of a hard limestone substrate on which the species moved, has yielded a great abundance of hippopotamus material, making the Ayia Napa locality one of the most important paleontological sites in Cyprus. The immigration of the large‐sized mainland Hippopotamus to Cyprus led to the emergence of a new insular species with its main characteristic being the extremely reduced body size. In this study, all the hindlimb elements of the Cypriot hippo are described in detail and compared with those of the modern species, with the extant Hippopotamus amphibius being considered similar to the possible ancestor of P. minor. In some cases, the morphological comparison is reinforced using bones of other extinct insular and mainland hippos. Additionally, we provided a functional analysis of the hindlimb joints, suggesting specific locomotor habits for the species. The anatomical examination reveals that the elements in P. minor are robust with marked muscular insertion areas resembling those found in Hippopotamus. However, there are also similarities with Choeropsis liberiensis in certain morphofunctional traits. P. minor adapted to slow but powerful locomotion with remarkable stabilization, particularly in the zeugopodium and the autopodium. The knee was less mobile in the craniocaudal direction compared with that in recent hippos, while the abduction–adduction movements of the thigh were advanced. The pes presented good mobility in the sagittal plane and limitation in transversal movements. Thus, P. minor displayed modifications to its limbs, influenced by the mountainous island environment and the body size reduction, resulting in specialized locomotion, which was different from that of extant hippopotamuses.

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Section: Discussionmentioning

confidence: 99%

Functional morphology of the hindlimb of fossilized pygmy hippopotamus from Ayia Napa (Cyprus)

Georgitsis

Liakopoulou

Θεοδώρου

et al. 2022

Journal of Morphology

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“…In this context, it would be possible to apply this IBM in a comparative way based on explicit variations in life history and ecology on the several islands in which C. elaphus experienced body size changes (van der Geer et al, 2012). Another important research avenue is to analyze phenotypic changes in multivariate space, incorporating other traits and their complex interactions, evaluating the constraints of body size evolution in the context of island syndromes (see Rozzi, 2018; Rozzi et al 2020 for recent examples).…”

Section: Discussionmentioning

confidence: 99%

Quantitative genetics of extreme insular dwarfing: The case of red deer on Jersey

Diniz‐Filho

Santos

Barreto

et al. 2021

Journal of Biogeography

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Aim The Island Rule—that is, the tendency for body size to decrease in large mammals and increase in small mammals on islands has been commonly evaluated through macroecological or macroevolutionary, pattern‐orientated approaches, which generally fail to model the microevolutionary processes driving either dwarfing or gigantism. Here, we seek to identify which microevolutionary process could have driven extreme insular dwarfism in the extinct dwarf red deer population on the island of Jersey. Location Jersey, UK (Channel Islands). Taxon Red deer (Cervus elaphus). Methods We applied an individual‐based quantitative genetics model parameterized with red deer life‐history data to study the evolution of dwarfism in Jersey's deer, considering variations in island area and isolation through time due to sea level changes. Results The body size of red deer on Jersey decreased fast early on, due to phenotypic plasticity, then kept decreasing almost linearly over time down to the actual body size of the Jersey deer (36 kg on average). Only 1% of 10,000 replicates failed to reach that size in our simulations. The distribution of time to adaptation in these simulations was right skewed, with a median of 395 generations (equivalent to roughly 4 kyr), with complete dwarfism effectively occurring in less than 6 kyr 84.6% of times. About 72% of the variation in the time to adaptation between simulations was collectively explained by higher mutational variance, the number of immigrants from the continent after isolation, available genetic variance, heritability, and phenotypic plasticity. Main Conclusions The extreme dwarfing of red deer on Jersey is an expected outcome of high mutational variance, high immigration rate, a wide adaptive landscape, low levels of inbreeding, and high phenotypic plasticity (in the early phase of dwarfing), all occurring within a time window of around 6 kyr. Our model reveals how extreme dwarfism is a plausible outcome of common, well‐known evolutionary processes.

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“…High-altitude habitat occupation by robust equinins may represent evidence of a perissodactyl form of a 'low-gear' locomotor morphology [47]. Low-gear locomotion is a method of low-speed walking in mountainous terrain exhibited by a wide range of artiodactyls, often associated with short and broad distal limb bones [48]. This phenomenon is known within insular populations evolving in predator-free environments [47], and is also exhibited in bovine artiodactyls inhabiting mountainous regions with low topographical complexity [48].…”

Section: (B) Extinction Migration and Morphological Disparitymentioning

confidence: 99%

“…Low-gear locomotion is a method of low-speed walking in mountainous terrain exhibited by a wide range of artiodactyls, often associated with short and broad distal limb bones [48]. This phenomenon is known within insular populations evolving in predator-free environments [47], and is also exhibited in bovine artiodactyls inhabiting mountainous regions with low topographical complexity [48]. The robust South American equinin metapodials with broad articular surface to dissipate loading forces, large areas for collateral, and suspensory ligament attachment [49] would have conferred a high degree of stability for the distal monodactyl forelimb [50], ideal for negotiating unstable or inclined substrates [48].…”

Section: (B) Extinction Migration and Morphological Disparitymentioning

confidence: 99%

“…The robust South American equinin metapodials with broad articular surface to dissipate loading forces, large areas for collateral, and suspensory ligament attachment [49] would have conferred a high degree of stability for the distal monodactyl forelimb [50], ideal for negotiating unstable or inclined substrates [48]. These convergent morphologies between two monodactyl lineages suggest that equinins migrating to South America underwent similar selective pressures to their locomotor apparatus, potentially resulting in a 'low-gear' locomotor mode akin to mountain-dwelling artiodactyls [48]. Evolutionary rates evidence suggests that MCP joint divergence in Hi.…”

Section: (B) Extinction Migration and Morphological Disparitymentioning

confidence: 99%

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Biogeography a key influence on distal forelimb variation in horses through the Cenozoic

Maclaren

2021

Proc. R. Soc. B.

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Locomotion in terrestrial tetrapods is reliant on interactions between distal limb bones (e.g. metapodials and phalanges). The metapodial–phalangeal joint in horse (Equidae) limbs is highly specialized, facilitating vital functions (shock absorption; elastic recoil). While joint shape has changed throughout horse evolution, potential drivers of these modifications have not been quantitatively assessed. Here, I examine the morphology of the forelimb metacarpophalangeal (MCP) joint of horses and their extinct kin (palaeotheres) using geometric morphometrics and disparity analyses, within a phylogenetic context. I also develop a novel alignment protocol that explores the magnitude of shape change through time, correlated against body mass and diet. MCP shape was poorly correlated with mass or diet proxies, although significant temporal correlations were detected at 0–1 Myr intervals. A clear division was recovered between New and Old World hipparionin MCP morphologies. Significant changes in MCP disparity and high rates of shape divergence were observed during the Great American Biotic Interchange, with the MCP joint becoming broad and robust in two separate monodactyl lineages, possibly exhibiting novel locomotor behaviour. This large-scale study of MCP joint shape demonstrates the apparent capacity for horses to rapidly change their distal limb morphology to overcome discrete locomotor challenges in new habitats.

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Causal explanations for the evolution of ‘low gear’ locomotion in insular ruminants

Abstract: This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Cited by 11 publications

References 72 publications

Functional morphology of the hindlimb of fossilized pygmy hippopotamus from Ayia Napa (Cyprus)

Functional morphology of the hindlimb of fossilized pygmy hippopotamus from Ayia Napa (Cyprus)

Quantitative genetics of extreme insular dwarfing: The case of red deer on Jersey

Biogeography a key influence on distal forelimb variation in horses through the Cenozoic

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