Tardigrades of Alaska: distribution patterns, diversity and species richness

Abstract

During the summer of 2010, a biotic survey of tardigrades was conducted along a latitudinal transect in central Alaska from the Kenai Peninsula, via Fairbanks and the Arctic Circle to the coastal plain. Work was centred at the Toolik and Bonanza Creek Long Term Ecological Research Network sites and supplemented by opportunistic collections from the Kenai Peninsula and Anchorage areas. The 235 samples collected at 20 sites over 10 degrees of latitude yielded 1463 tardigrades representing two classes, three orders, 10 families, 23 genera and 73 species from 142 positive samples. A total of 50 species are new to Alaska, increasing the state's known species richness to 84. Several environmental metrics, such as pH, substrate, elevation, location and habitat were measured, recorded and analysed along the latitudinal gradient. Contrary to expectations, pH did not appear to be a predictor of tardigrade abundance or distribution. Density and species richness were relatively consistent across sites. However, the assemblages were highly variable within and between sites at only 14–20% similarity. We detected no correlation between species diversity and latitudinal or environmental gradients, though this may be affected by a high (59.9%) occurrence of single-species samples (containing individuals of only one species). Estimates of species richness were calculated for Alaska (118) and the Arctic (172). Our efforts increased the number of known species in Alaska to 84, and those results led us to question the validity of the estimate numbers.

• Tardigrade
• Alaska
• distribution
• latitudinal gradient
• pH
• species richness

Acknowledgements

This project was supported by US National Science Foundation grants, numbers DEB 0640847 to Baker University, DEB 0641051 to Fresno City College and DEB0640959 to Brigham Young University. We are grateful for the geographic information system-based Alaska map produced by Dr Jeff Miller of Missoula, MT. Stephanie Calloway, Carleigh Takemoto, Alex Arnett and Brittany Deegan provided hundreds of hours of invaluable effort in sampling, identification and database management. Philip Pugh was gracious with his time, independently verifying and confirming our findings using additional statistical tests. Bill Johansson provided suggestions and motivation to improve and shape the manuscript. We also want to particularly thank the reviewers of this manuscript. They took an exceptional amount of time and expended considerable effort in reviewing, editing and improving this article. Their efforts are greatly appreciated by the authors.