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Ming KM, Le Verger K, Geiger M, Schmelzle T, Georgalis GL, Shimbo G, Sasaki M, Ohdachi SD, Sánchez-Villagra MR. Insular dwarfism in horses from the Aegean Sea and the Japanese archipelago. Mamm Biol 2024; 104:345-361. [PMID: 39070961 PMCID: PMC11281976 DOI: 10.1007/s42991-024-00408-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Accepted: 02/22/2024] [Indexed: 07/30/2024]
Abstract
The horse (Equus caballus) varieties from Skyros and Rhodes islands (Greece) in the Aegean archipelago are extremely small, reaching shoulder heights of only about 1 m. Furthermore, the Japanese archipelago is home to eight small, native horse breeds. We investigated the evolutionary morphology and provided a review of historical documentations of these horses of cultural interest in Greece and Japan, thus providing a comparison of the independent evolution of small size in islands. We integrate cranial data from historical literature with data from newly gathered and curated skulls and analyse a measurement dataset featuring various domestic and mainland horse breeds and varieties. We use non-invasive imaging to study and measure 3D models of the bony labyrinth, housing the inner ear, and the braincase endocast. When considering the effects of allometry by regressing each PC1 scores (for each set of measurements) with the cranial geometric mean from linear measurements as a body size proxy, we show that size explains a large amount of the shape variation in horse crania, the bony labyrinths and brain endocasts. We found high intrabreed variation in all the analysed datasets. Globally, there are at least 30 distinct horse populations on islands, offering the chance to further study processes of convergence in morphological divergence and evaluate the effect of drift and the environment. Supplementary Information The online version contains supplementary material available at 10.1007/s42991-024-00408-4.
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Affiliation(s)
- Keesha M. Ming
- Department of Paleontology, University of Zurich, Karl-Schmid-Strasse 4, 8006 Zurich, Switzerland
| | - Kévin Le Verger
- Department of Paleontology, University of Zurich, Karl-Schmid-Strasse 4, 8006 Zurich, Switzerland
| | - Madeleine Geiger
- Naturmuseum St. Gallen, Rorschacher Strasse 263, 9016 St. Gallen, Switzerland
| | - Thomas Schmelzle
- Department of Paleontology, University of Zurich, Karl-Schmid-Strasse 4, 8006 Zurich, Switzerland
| | - Georgios L. Georgalis
- Department of Paleontology, University of Zurich, Karl-Schmid-Strasse 4, 8006 Zurich, Switzerland
- Institute of Systematics and Evolution of Animals, Polish Academy of Sciences, Sławkowska 17, 31-016 Kraków, Poland
| | - Genya Shimbo
- Institute of Veterinary Medicine, Hokkaido University, Kita-19, Nishi-8, Kita-Ku, Sapporo, 060-0819 Japan
| | - Motoki Sasaki
- Department of Veterinary Medicine, Obihiro University of Agriculture and Veterinary Medicine, Inada-Cho, Obihiro, Hokkaido 080-8555 Japan
| | - Satoshi D. Ohdachi
- Institute of Low Temperature Science, Hokkaido University, Kita-19, Nishi-8, Kita-Ku, Sapporo, 060-0819 Japan
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Alhaddad H, Powell BB, Pinto LD, Sutter N, Brooks SA, Alhajeri BH. Geometric morphometrics of face profile across horse breeds and within Arabian horses. J Equine Vet Sci 2024; 132:104980. [PMID: 38070586 DOI: 10.1016/j.jevs.2023.104980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Revised: 11/08/2023] [Accepted: 12/06/2023] [Indexed: 12/20/2023]
Abstract
Horse traits under selection are largely quantitative and affected by multiple genes. Horse face shape is an example of a continuous trait, which due to the reliance on observational assessments, is classified into; "dished", "straight", and "roman-nosed". This categorization is often inadequate to convey the full spectrum of the face shape variation especially for genetic studies. The first objective of the current study was to use geometric morphometric methods to quantitatively phenotype face shapes and examine its variation across horse breeds. The second objective was to analyze the face shape variation within Arabian horses since face shape is (1) favored, valued, and genetically selected in certain lineages (e.g. Egyptian), (2) is evaluated by registries and scored in shows, and (3) in its extreme forms pose health concerns. We digitized landmarks on lateral profile photos, particularly on the dorsal curvature of the rostrum, and subjected these landmarks to Generalized Procrustes Analysis to generate independent shape and size variables which were statistically compared across breeds and within Arabians. Horse breeds varied in nasal curvature, ranging from extremely concave to extremely convex, with over 70 % of horse breeds exhibiting intermediate concavity (i.e., straight profile). Interestingly, Arabian horses possessed the highest diversity in face profile and individuals clustered into three distinct shape sub-groups (one dished and two straight profile clusters). Our quantitative phenotyping method can be the basis of future genetic studies of facial profile within Arabian lineages as a favored traits and potentially manage its extreme forms as a likely genetic disease.
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Affiliation(s)
- H Alhaddad
- Department of Biological Sciences, Kuwait University, Shadadiya, Kuwait.
| | - B B Powell
- Department of Animal Science, UF Genetics Institute, University of Florida, Gainesville, Florida, USA
| | - L Del Pinto
- Biology Department, La Sierra University, Riverside, California, USA
| | - N Sutter
- Biology Department, La Sierra University, Riverside, California, USA
| | - S A Brooks
- Department of Animal Science, UF Genetics Institute, University of Florida, Gainesville, Florida, USA
| | - B H Alhajeri
- Department of Biological Sciences, Kuwait University, Shadadiya, Kuwait
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