Ecological factors determining Tardigrada distribution in Costa Rica.

Over 700 moss, lichen and hepatic samples were collected from territory of Costa Rica. Tardigrades were present in nearly half of the samples. Overall, more than 7000 tardigrades were found. All specimens were identified as 64 species belonging to 18 genera. The number of species per positive sample varied between 1 and 10, but on average it did not exceed three. The most important factor influencing distribution of Tardigrada in Costa Rica was altitude. Tardigrades most often inhabited mosses, lichens and hepatics collected from 2000 to 2400 m asl and above 3200 m asl (more than 70% positive samples). The highest Tardigrada species diversity was found between 1400 and 2000 m asl (35 species, 55%), and the lowest between 2400 and 2800 m asl (18 species, 28%). The second strongest factor that influenced tardigrade distribution was the type of environment. A significantly higher proportion of positive samples were found in urban and agricultural areas (about 60%) than in natural habitats (only about 30%). The highest frequency of positive samples was found in humid habitats. Surprisingly, among all analysed factors, the substrate and plant type had the weakest influence on tardigrade distribution. [ABSTRACT FROM AUTHOR]