Intraspecific variation in digit reduction in Testudo: the case of the Hermann’s tortoise

Abstract

Phalangeal reduction is a common and widespread phenomenon among tortoises that has been associated with the adaptation to terrestrial life. While reduced manual digit 1 appears characteristic in almost all Testudo species, it is uncertain why the metacarpal I and distal carpal of the same digit are completely missing in some individuals of Hermann’s tortoise (Testudo hermanni hermanni). To clarify this issue, we investigated the number of manual claws in six populations of Hermann’s tortoise (one from the Ebro Delta in the Iberian Peninsula and five from Minorca Island), their age, sex, genetic lineage, and the substrate type that they inhabit. The number of claws was ascertained based on direct counts (n > 1500 individuals) and by X-rays (n = 32 individuals), obtaining three different phalangeal formulae: (1-2-2-2-1, D-2-2-2-1, 0-2-2-2-1). Thus, claw counts through both methodologies (direct count and X-ray) further confirm that the observed claws serve as a good proxy to assess the actual number of digits. Our results show no loss of phalanges, metacarpal and carpal bones in digit 1 associated with age, sex, or substrate, contrary to some previous authors who hypothesized a relationship between this loss and sexual dimorphism. Therefore, variations in the number of manual digits and the loss of metacarpal I and distal carpal in digit 1 in Hermann’s tortoise are related to population and genetic lineage. More detailed comparisons with other Testudo hermanni populations from elsewhere in Europe would be required to understand the evolutionary significance concerning the intrapopulation variability in the number of digits remaining.

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All data generated and analyzed during this study are included in this published article.

References

  1. Arnholt, A. T., & Evans, B. (2017). BSDA: Basic statistics and data analysis. R package version 1.2.0. https://CRAN.R-project.org/package=BSDA. Accessed 12 March 2018.

  2. Auffenberg, W. (1966). The carpus of land tortoises. Bulletin of Florida State Museum, 10, 159–191.

    Google Scholar 

  3. Bates, D., Maechler, M., Bolker, B., & Walker, S. (2015). Fitting linear mixed-effects models using lme4. Journal of Statistical Software, 67, 1–48. https://doi.org/10.18637/jss.v067.i01.

    Article  Google Scholar 

  4. Baur, G. (1888). Osteologische Notizen über Reptilien (Fortsetzung III). Zoologischer Anzeiger, 285, 417–424.

    Google Scholar 

  5. Bertolero A (2002) Biología de la tortuga mediterránea Testudo hermanni aplicada a su conservación. Unpublished Ph.D. Dissertation, University of Barcelona, Spain.

  6. Bertolero, A. (2010). Tortuga mediterránea – Testudo hermanni Gmelin, 1789. In A. Salvador & A. Marco (Eds.), Enciclopedia Virtual de los Vertebrados Españoles (pp. 1–34). Museo Nacional de Ciencias Naturales: Madrid.

    Google Scholar 

  7. Bertolero, A. (2014). Testudo hermanni Gmelin, 1789. In A. Salvador (Ed.), Reptiles, 2ª edición, revisada y aumentada, Fauna Ibérica, vol. 10 (pp. 217–236). Museo Nacional de Ciencias Naturales: Madrid.

    Google Scholar 

  8. Bertolero, A., & Pretus, J. (2012). Distribució actual de la tortuga mediterrània a Menorca. Revista de Menorca, 91, 177–186.

    Google Scholar 

  9. Bertolero, A., Nougarède, J.-P., Cheylan, M., & Marín, A. (2007). Breeding traits of Hermann’s tortoise Testudo hermanni hermanni in two western populations. Amphibia-Reptilia, 28, 77–85. https://doi.org/10.1163/156853807779798965.

    Article  Google Scholar 

  10. Bertolero, A., Cheylan, M., Hailey, A., Livoreil, B., & Willemsen, R. E. (2011a). Testudo hermanni (Gmelin 1789) - Hermann’s tortoise. Conservation biology of freshwater turtles and tortoises: A compilation project of the IUCN/SSC Tortoise and Freshwater Turtle Specialist Group. Chelonian Research Monographs, 5, 059.1–059.20. https://doi.org/10.3854/crm.5.059.hermanni.v1.2011.

    Article  Google Scholar 

  11. Bertolero, A., Pretus, J. L., & Massana, M. (2011b). Características genéticas y demográficas de las poblaciones de tortuga mediterránea en Menorca. In J. A. Mateo (Ed.), La conservación de las tortugas de tierra en España (pp. 41–45). Palma de Mallorca: Conselleria de Medi Ambient i Mobilitat, Govern de les Illes Balears.

    Google Scholar 

  12. Bertolero, A., Pretus, J. L., & Oro, D. (2018). The importance of including survival release costs when assessing viability in reptile translocations. Biological Conservation, 217, 311–320. https://doi.org/10.1016/j.biocon.2017.11.023.

    Article  Google Scholar 

  13. Boulenger, G. A. (1889). Catalogue of the chelonians, rhynchocephalians, and crocodiles in the British Museum (Natural History). London: Taylor and Francis.

    Google Scholar 

  14. Bramble, D. M. (1982). Scaptochelis: Generic revision and evolution of gopher tortoises. Copeia, 4, 853–866. https://doi.org/10.2307/1444097.

    Article  Google Scholar 

  15. Cheylan, M. (1981). Biologie et écologie de la tortue d’Hermann Testudo hermanni Gmelin 1789. Contribution de l’espèce a la connaissance des climats quasternaires de la France. Montpellier: Mémoires et Travaux de l’Institut de Montpellier (E.P.H.E.), 13, 1–382.

    Google Scholar 

  16. Cheylan, M. (2001). Testudo hermanni Gmelin, 1789 – Griechische Landschildkröte. In U. Fritz (Ed.), Handbuch der Reptilien und Amphibien Europas. Band 3/IIIA: Schildkröten I (pp. 179–289). Wiebelsheim: Aula–Verlag.

    Google Scholar 

  17. Cheylan, M. (2004). Incendies: lourd tribu pour les tortues d'Hermann. Espace Naturels, 5, 10.

    Google Scholar 

  18. Choquenot, D., & Greer, A. E. (1989). Intrapopulational and interspecific variation in digital limb bones and presacral vertebrae of the genus Hemiergis (Lacertilia, Scincidae). Journal of Herpetology, 23, 274–281. https://doi.org/10.2307/1564449.

    Article  Google Scholar 

  19. Couturier, T., Cheylan, M., Guérette, E., & Besnard, A. (2011). Impacts of a wildfire on the mortality rate and small-scale movements of a Hermann’s tortoise Testudo hermanni hermanni population in southeastern France. Amphibia-Reptilia, 32, 541–545. https://doi.org/10.1163/156853811X601627.

    Article  Google Scholar 

  20. Crumly, C. R., & Sánchez-Villagra, M. R. (2004). Patterns of variation in the phalangeal formulae of land tortoises (Testudinidae): Developmental constraint, size, and phylogenetic history. Journal of Experimental Zoology Part B: Molecular and Developmental Evolution, 302B, 134–146. https://doi.org/10.1002/jez.b.20010.

    Article  Google Scholar 

  21. Delfino, M., Fritz, U., & Sánchez-Villagra, M. R. (2010). Evolutionary and developmental aspects of phalangeal formula variation in pig-nose and soft-shelled turtles (Carettochelyidae and Trionychidae). Organisms Diversity & Evolution, 10, 69–79. https://doi.org/10.1007/s13127-010-0019-x.

    Article  Google Scholar 

  22. Eendebak, B. T. (2001). Incubation period and sex ratio of Testudo hermanni boettgeri. In: Proceeding International Congress on Testudo Genus. Chelonii, 3, 257–267.

  23. Ernst, C. H., & Barbour, R. W. (1989). Turtles of the world. Washington, USA: Smithsonian Institution Press.

    Google Scholar 

  24. Ernst, C. H., Altenburg, R. G. M., & Barbour, R. W. (2000). Turtles of the world. World biodiversity database, CDROM series, windows version 1.2. Amsterdam, The Nertherlands: Biodiversity Center of ETI.

    Google Scholar 

  25. Fritz, U., & Bininda-Emonds, O. R. P. (2007). When genes meet nomenclature: Tortoise phylogeny and the shifting generic concepts of Testudo and Geochelone. Zoology, 110, 298–307. https://doi.org/10.1016/j.zool.2007.02.003.

    CAS  Article  PubMed  Google Scholar 

  26. Fritz, U., Auer, M., Bertolero, A., Cheylan, M., Fattizzo, T., Hundsdörfer, A. K., Martín Sampayo, M., Pretus, J. L., ŠIrok, Ý. P., & Wink, M. (2006a). A rangewide phylogeography of Hermann’s tortoise, Testudo hermanni (Reptilia: Testudines: Testudinidae): Implications for taxonomy. Zoologica Scripta, 35, 531–543. https://doi.org/10.1111/j.1463-6409.2006.00242.x.

    Article  Google Scholar 

  27. Fritz, U., Petzold, A., & Auer, M. (2006b). Osteology in the Cuora galbinifrons complex suggests conspecifity of C. bourreti and C. galbinifrons, with notes on shell osteology and phalangeal formulae within the Geoemydidae. Amphibia-Reptilia, 27, 195–205. https://doi.org/10.1163/156853806777240029.

    Article  Google Scholar 

  28. Grant, P. R., & Grant, R. (1994). Phenotypic and genetic effects of hybridization of Darwin’s finches. Evolution, 48, 297–316. https://doi.org/10.1111/j.1558-5646.1994.tb01313.x.

    Article  PubMed  Google Scholar 

  29. Highfield, A. C. (1988). New size record for T. hermanni? The Rephiberary, 132, 5–6.

    Google Scholar 

  30. Hitschfeld, E., Auer, M., & Fritz, U. (2008). Phalangeal formulae and ontogenetic variation of carpal morphology in Testudo horsfieldii and Testudo hermanni. Amphibia-Reptilia, 29, 93–99. https://doi.org/10.1163/156853808783431569.

    Article  Google Scholar 

  31. Hothorn, T., Bretz, F., & Westfall, P. (2008). Simultaneous inference in general parametric models. Biometrical Journal, 50, 346–363. https://doi.org/10.1002/bimj.200810425.

    Article  PubMed  PubMed Central  Google Scholar 

  32. Litingtung, Y., Dahn, R. D., Li, Y., Fallon, J. F., & Chiang, C. (2002). Shh and Gli3 are dispensable for limb skeleton formation but regulate digit number and identity. Nature, 418, 979–983. https://doi.org/10.1038/nature01033.

    CAS  Article  PubMed  Google Scholar 

  33. Ludwig, M., Auer, M., & Fritz, U. (2007). Phalangeal formulae of geoemydid terrapins (Batagur, Callagur, Hardella, Heosemys, Kachuga, Orlitia, Pangshura, Rhinoclemmys) reflect distinct modes of life. Amphibia-Reptilia, 28, 574–576. https://doi.org/10.1163/156853807782152570.

    Article  Google Scholar 

  34. Luján, À. H., Delfino, M., Robles, J. M., & Alba, D. M. (2016). The Miocene tortoise Testudo catalaunica Bataller, 1926, and a revised phylogeny of extinct species of genus Testudo (Testudines: Testudinidae). Zoological Journal of the Linnean Society, 178, 312–342. https://doi.org/10.1111/zoj.12414.

    Article  Google Scholar 

  35. Marmi, J., & Luján, À. H. (2012). An overview of the threatened phylogenetic diversity of living testudines based on a review of the complex evolutionary history of turtles. In M. J. Cosgrove & S. A. Roe (Eds.), Turtles: Anatomy, Ecology and Conservation (pp. 117–150). Nova Science Publishers: New York.

    Google Scholar 

  36. McHorse, B. K., Biewener, A. A., & Pierce, S. E. (2017). Mechanics of evolutionary digit reduction in fossil horses (Equidae). Proceedings of the Royal Society B: Biological Sciences, 284, 20171174. https://doi.org/10.1098/rspb.2017.1174.

    Article  Google Scholar 

  37. Merino, R., Gañan, Y., Macias, D., Economides, A. N., Sampath, K. T., & Hurle, J. M. (1998). Morphogenesis of digits in the avian limb is controlled by FGFs, GFbs, and Noggin through BMP signaling. Developmental Biology, 200, 35–45. https://doi.org/10.1006/dbio.1998.8946.

    CAS  Article  PubMed  Google Scholar 

  38. Minx, P. (1992). Variation in phalangeal formulae in the turtle genus Terrapene. Journal of Herpetology, 26, 234–238. https://doi.org/10.2307/1564873.

    Article  Google Scholar 

  39. Nikolić, S., Golubović, A., Bonnet, X., Arsovski, D., Ballouard, J.-M., Ajtić, R., Sterijovski, B., Iković, V., Vujović, A., & Tomović, L. (2018). Why an apparently prosperous subspecies needs strict protection? The case of Testudo hermanni boettgeri from the central Balkan. Herpetological Conservation and Biology, 13, 673–690.

    Google Scholar 

  40. R Development Core Team. (2015). R: A Language and Environment for Statistical Computing. R Foundation for Statistical Computing, Vienna. [Online.] Available at cran.r-project.org/doc/manuals/refman.pdf. Accessed 12 March 2018.

  41. Rieseberg, L. H., Widmer, A., Arntz, A. M., & Burke, J. M. (2003). The genetic architecture necessary for transgressive segregation is common in both natural and domesticated populations. Philosophical transactions of the Royal Society of London Series B, Biological Sciences, 358, 1141–1147. https://doi.org/10.1098/rstb.2003.1283.

    CAS  Article  PubMed  PubMed Central  Google Scholar 

  42. Santos, X., & Cheylan, M. (2013). Taxonomic and functional response of a Mediterranean reptile assemblage to a repeated fire regime. Biological Conservation, 168, 90–98. https://doi.org/10.1016/j.biocon.2013.09.008.

    Article  Google Scholar 

  43. Shapiro, M. D., Hanken, J., & Rosenthal, N. (2003). Developmental basis of evolutionary digit loss in the Australian lizard Hemiergis. Journal of Experimental Zoology (Mol Dev Evol), 297B, 48–56. https://doi.org/10.1002/jez.b.19.

    Article  Google Scholar 

  44. Shapiro, M. D., Shubin, N. H., & Downs, J. P. (2007). Limb diversity and digit reduction in reptilian evolution. In B. K. Hall (Ed.), Fins into limbs: Evolution, development, and transformation (pp. 225–245). University of Chicago Press: Chicago.

    Google Scholar 

  45. Sheth, R., Marcon, L., Bastida, M. F., Junco, M., Quintana, L., Dahn, R., Kmita, M., Sharpe, J., & Ros, M. A. (2012). Hox genes regulate digit patterning by controlling the wavelength of a Turing-type mechanism. Science, 338, 1476–1480. https://doi.org/10.1126/science.1226804.

    CAS  Article  PubMed  PubMed Central  Google Scholar 

  46. te Welscher, P., Zuniga, A., Kuijper, S., Drenth, T., Goedemans, H. J., Meijlink, F., & Zeller, R. (2002). Progression of vertebrate limb development through SHH-mediated counteraction of GLI3. Science, 298, 827–830. https://doi.org/10.1126/science.1075620.

    CAS  Article  Google Scholar 

  47. TTWG [Turtle Taxonomy Working Group] (2017). Turtles of the world. Annotated checklist and atlas of taxonomy, synonymy, distribution, and conservation status (8th ed.). Lunenburg, Canada: Chelonian Research Foundation and Turtle Conservancy (Chelonian Research Monographs 7). http://10.3854/crm.7.checklist.atlas.v8.2017. Accessed 22 March 2018.

  48. Vasilyev, V. A., Korsunenko, A. V., Pereshkolnik, S. L., Mazanaeva, L. F., Bannikova, A. A., Bondarenko, D. A., Peregontsev, E. A., Semyenova, S. K., & Semyenova, S. K. (2014). Differentiation of tortoises of the genera Testudo and Agrionemys (Testudinidae) based on the polymorphism of nuclear and mitochondrial markers. Russian Journal of Genetics, 50, 1060–1074. https://doi.org/10.1163/15685381-00002895.

    CAS  Article  Google Scholar 

  49. Vetter, H. (2006). In Chimairia (Ed.), Herman’s tortoise – Testudo hermanni. Frankfurt: Chimairia.

    Google Scholar 

  50. Zenboudji, S., Cheylan, M., Arnal, V., Bertolero, A., Leblois, R., Astruc, G., Bertolere, G., Pretus, J. L., Lo Valvo, M., Sotgiu, G., & Montgelard, C. (2016). Conservation of the endangered Mediterranean tortoise Testudo hermanni hermanni: The contribution of population genetics and historical demography. Biological Conservation, 195, 279–291. https://doi.org/10.1016/j.biocon.2016.01.007.

    Article  Google Scholar 

  51. Zug, G. R. (1971). Buoyancy, locomotion, morphology of the pelvic girdle and hindlimb, and systematics of cryptodiran turtles. Miscellaneous Publications. Museum of Zoology, University of Michigan, 142, 1–98.

    Google Scholar 

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Acknowledgments

AB thanks especially Delta de l’Ebre Natural Park staff, Joan Pretus and Marta Massana, for their valuable assistance over several years. We thank Pierre Dupont and Vérane Berger for helpful comments and discussion of statistical analyses. We further acknowledge the Editor (A. Wanninger) and two reviewers (W. Joyce and G. Ferreira) for helpful and constructive comments and suggestions that helped us to improve a previous version of this paper.

Funding

The research reported in this work was funded by the Spanish Agencia Estatal de Investigación – European Regional Development Fund of the European Union (CGL2016-76431-P and CGL2017-82654-P, AEI/FEDER EU to À.H.L) and the Generalitat de Catalunya (CERCA Programme to À.H.L and 2017 SGR 1006 to M.F.R). À.H.L. is financially supported through postdoctoral grant by the European Union at Masaryk University, Czech Republic (CZ.02.2.69/0.0/0.0/16_027/0008360) during the elaboration of this paper and a research visit to the University of Comenius in Bratislava, Slovakia (National Scholarship Programme of the Slovak Republic for the support of mobility of researchers, Autumn Call 2017). AB is supported by the Delta de l’Ebre Natural Park (Generalitat de Catalunya), l’Institut Menorquí d’Estudis, and the Conselleria de Medi Ambient (Direcció General de Biodiversitat) de les Illes Balears.

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MFR and CT performed the statistical analyses; AB and AHL coordinated the data collection; AB, AHL, and MFR conceived and designed the experiment; AB, AHL, MFR, and CT analyzed the data; AB, AHL, and MFR wrote the paper.

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Correspondence to Àngel H. Luján or Mariona Ferrandiz-Rovira.

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Luján, À.H., Ferrandiz-Rovira, M., Torres, C. et al. Intraspecific variation in digit reduction in Testudo: the case of the Hermann’s tortoise. Org Divers Evol 19, 625–635 (2019). https://doi.org/10.1007/s13127-019-00413-3

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Keywords

  • Testudo hermanni
  • Phalange reduction
  • Ebro Delta
  • Minorca Island
  • Phalangeal formula