GIS Modelling of the Distribution of Terrestrial Tortoise Species: Testudo graeca and Testudo hermanni (Testudines, Testudinidae) of Eastern Europe in the Context of Climate Change

Abstract

The study of the distribution of protected animal species in Europe is especially relevant in a changing climate. Therefore, in this work, we tried to solve the problem of the possibility of habitation of turtles Testudo graeca and Testudo hermanni in Eastern Europe by using species distribution models (SDMs). We used bioclimatic variables from the CliMond dataset (18 uncorrelated variables of 35) and 19 paleoclim variables of the “early-Holocene”. Packages Maxent package and 'ntbox' were employed. In addition to our data, we used findings listed in the GBIF databases: 1935 points for T. graeca and 991 points for T. hermanni. It has been shown that subspecies of turtles differ in the characteristics of the ecological niche. In addition to direct anthropogenic influences, the limiting factor is the “Mean temperature of coldest quarter” (bio11) for both species. Moreover, T. graeca is less demanding and can tolerate both frost and higher temperatures during drier periods than T. hermanni. Thus, T. graeca (90%, bio11) – from -2 to +14 °C (limits from -6 and +17 °C), mean consisting +7 °C, and T. hermanni (90%) from -1 to +11 °C (limits between -3 and +12 °C), mean consisting +6 °C (DivaGis). Modeling found that in the future it is possible for these species to move in a north-eastern direction, where potentially suitable habitats will appear: by 2090 in the South of Ukraine (Odessa region, Crimea) and East Ukraine (floodplain of the Seversky Donets River of the Don basin).

Keywords

• ecological niche model
• distribution
• turtle
• climate change
• expansion