Morphological Divergence of Hermann's Tortoise (Testudo hermanni boettgeri Mojsisovits, 1889) in Albania

Abstract

Testudines show phenotypic plasticity, and variation among specific populations within a species is widespread. Morphological differences between populations may reflect ecological factors that drive adaptation to local conditions. In this context, we gathered basic data on the morphology of the Hermann's tortoise (Testudo hermanni boettgeri Mojsisovits, 1889) to document their variation across different geographical regions. We surveyed Hermann's tortoises in five different locales within Albania during April and May 2020 and measured 20 morphological characteristics, including carapace and plastron dimensions. We measured 188 tortoises (81 males, 107 females) in this study, and females were larger (p = 0.0001) and heavier (p = 0.0001) than males. Mean straight carapace length (SCL) and body mass were 172.4 mm and 1128.8 g, respectively, for females, and 151.3 mm and 735 g, respectively, for males. The Albanian T. h. boettgeri were regionally diverged into three different populations that were situated in northern (Shkodra), central (Tirana, Berati, and Ballshi), and southern (Saranda) Albania. The body size (curved carapace length (CCL)) of females was positively correlated (r = 0.216; p = 0.025) with the latitude, in accordance with Bergmann's rule. However, there was no correlation between body size and latitude in males. These striking regional differences among Albanian T. h. boettgeri strongly suggest that further study of molecular variations and reproductive output of Hermann's tortoises is warranted.

Keywords: Bergmann’s rule; Hermann’s tortoises; Testudo hermanni boettgeri; carapace morphometry; plastron scutes.

Figure 1

Location and distribution of the field survey regions of Hermann’s tortoises in five regions of Albania.

Figure 2

Measurement parameters of the carapace and plastron of T. h. boettgeri. Abbreviations are defined in the Materials and Methods section. The numbers in parentheses indicate the parameter number. (A,B) indicate carapace measurements, (C) indicates plastron measurements.

Figure 3

Frequency distributions of body condition index (CI) in male (n = 81) and female (n = 107) Hermann’s tortoises in Albania.

Figure 4

Discriminant function analysis plot with 95% confidence ellipses based on morphological analysis among the five regions in Albania.

Figure 5

Discriminant function analysis plot with 95% confidence ellipses based on the morphological analysis by the male and female among the five regions in Albania.