| Abstract |
The non-volant small mammals of Greece are an heterogenous group that is represented with 40 species from the Orders of Eulipotyphla and Rodentia. Although they constitute important components in all terrestrial ecosystems, primary questions about their distribution and ecology remain unanswered.
Tyto alba is a habitat generalist, nocturnal raptor that feeds primarily on small mammals. T. alba pellet analysis provides a great number of skulls of various small mammals that can be utilized for the study of small mammals.
The combination of remote sensing environmental data with geographic occurrences of species allows the use of geographic algorithms to study the ecology of species and communities. The choice of environmental data, the scale, as well as the choice of algorithms and their parameterization significantly affect the results of such analyses.
The aim of the current study is the combination of geographic information systems and T. alba pellet analyses to investigate the distribution and ecological preferences of small mammals in Greece.
We discovered T. alba nests and roosts and collected pellets from 95 locations in continental Greece. For the subsequent analysis we wrote and published the key of the skull of the micromammals in Greece. Pellets from 69 designated locations were analyzed, from which we identified 16.124 vertebrate prey of T.alba, and furthermore at 97 locations on Greek islands we identified 6.628 prey. We additionally gathered occurrences from the literature and other sources.
Small mammals comprised 97.6% of the diet with representation from seven species of Eulipotyphla and 21 species of Rodentia. Most common prey genera in continental Greece were Mus, Microtus and Crocidura, while in the islands the genus Mus was dominant.
To compare the diet, we utilized Levins niche breadth index and Pianka’s similarity index, as well as three ordination techniques (non-metric Multidimensional Scaling, Canonical Correspondence Analysis, Distance based Redundancy Analysis)
44 environmental variables were used for the investigation of the ecology of small mammals. They include land use, climate, topography, and human population. The geographic analyses were restricted to continental Greece, with our scale being 100 * 100 meters with a 1km buffer to simulate the home range of T. alba.
We created species distribution models using three different feature selection techniques (Variance Inflation Factor, Least Absolute Shrinkage and Selection Operator, Statistically Equivalent Signature) in combination with four species distribution algorithms (Maximum Entropy, Artificial Neural Networks, Random Forest, Generalized Linear Models) with various parameters considered for each algorithm, resulting in a total of 1377 models per species. We evaluated the best modes for each algorithm by AUC and selected two models based on expert opinion.
For the investigation of the relations between species and environment we utilized joint species distribution models, with abundance and occurrence data.
The regions of east Greece showed high similarity in the diet of T. alba, while the west and south Greece also showed similarity but with greater variation. The diversity of small mammals was lowest in south Greece.
We created species distribution models for 14 species of small mammals in continental Greece and identified principal ecological variables based on our two chosen models as well as 100 models with the highest AUC. The model evaluation for the best models based on AUC was between 0.7 and 0.9 regardless of the combinations used.
A high number of occurrence data of small mammals from various regions of the country were recorded. For the first time in Greece we recorded Myomimus roachi, as well as rare and common small mammals of Greece. Our results have been provided to inform the European atlas of mammals and the national atlas of mammals that has been published from the Hellenic Zoological Society. Lastly the data was utilized for the evaluation of the extinction risk of some species according to the criteria of IUCN of the Greek Red List of Threatened Species.
|
Collections
