Using data for the body size and shell shape of Algerian Testudo graeca, we assessed how proximate causes shaped the observed variation in the morphology of adults. All of the studied populations displayed significant sexual size and shape dimorphisms. Relative to body length, females displayed larger, more voluminous and domed shells than males. We found clear evidence that variation in body size at maturity influenced sexual size dimorphism. Body size at maturity depends on the duration of growth from hatching up to the point of reaching sexual maturity. In the studied populations, sexual maturity, estimated by counting growth lines, was always reached earlier in males than in females (a time difference of 1.4-3.0 years). Similar to sexual size dimorphism, geographic variation in adult body sizes was also influenced by variations in the corresponding sizes at maturity. Remarkably, the population with the largest tortoises had the latest mean maturation time: 9.1 for males and 10.5 for females. Thus, the later completion of maturation was a determinant for a larger size in adulthood. The largest tortoises among the studied populations were measured at the Djelfa locality, where the recorded sizes of males and females reached 186 and 230 mm, respectively.

CEITEC Central European Institute of Technology University of Veterinary Sciences Brno Palackého 1946 1 612 42 Brno Czech Republic

Department of Biology and Wildlife Diseases Faculty of Veterinary Hygiene and Ecology University of Veterinary Sciences Brno Palackého 1946 1 612 42 Brno Czech Republic

Environment and Biodiversity Research Division National Environmental Research Center Sidi Amar University Campus 2024 Annaba 23005 Algeria

Functional and Evolutionary Ecology Laboratory Faculty of Natural and Life Sciences University Chadli Bendjedid 76 El Tarf 36000 Algeria

National Environmental Research Center Sidi Amar University Campus 2024 Annaba 23005 Algeria

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