Planktonic and periphytic bdelloid rotifers from Thailand reveal a species assemblage with a combination of cosmopolitan and tropical species

Abstract

The dispersal pattern of microorganisms has been a debated topic in the last decade, because for microscopic organisms with dispersing stages, biogeographic barriers may not exist and geographic distances may have little effect on the probability of their occurrence. In this study we tested whether a group of microscopic animals, the bdelloid rotifers, sampled in a tropical country, could indeed be cosmopolitan, strictly tropical, and/or have endemic species. We sampled freshwater habitats throughout Thailand in dry and rainy seasons between 2014 and 2016, focusing on permanent water bodies, where the prevalence of species producing resting stages acting as propagules for dispersal should be minimal and thus dispersal limitation should exist, with several species being narrowly distributed. We used traditional morphological identification, geometric morphometric analyses on the shape and size of the jaws, and DNA taxonomy to identify species and to quantify the morphological and genetic distances of Thai samples in comparison with data on bdelloids from other areas in the world. We found a total of 12 species of planktonic and periphytic bdelloid rotifers, and all approaches we used, qualitative and quantitative, confirmed a group of nine potentially cosmopolitan species already known from other continents, one tropical oriental species, and two new species with a potentially narrow geographic distribution, one of which we here formally describe. We thus support the idea that for microscopic animals the moderate endemicity hypothesis suggested for protists may also hold true: most of the species we found indeed have a wide geographic distribution, but other species with narrower distributions do exist.

http://zoobank.org/urn:lsid:zoobank.org:pub:3DF5A913-BE6A-4EA4-88FD-C38C0F7AE00A

Key words:

• biogeography
• distribution
• DNA taxonomy
• geometric morphometrics
• Rotaria megarostris sp. nov.
• trophi

Acknowledgements

This research was financially supported by Science Achievement Scholarship of Thailand (SAST), Graduate School and National Research Universities (NRU), Prince of Songkla University and Research Career Development Grant, Thailand Research Fund (RSA6080032). Particular thanks to The Centre of Excellence for Biodiversity of Peninsular Thailand (CBIPT), Faculty of Science, Prince of Songkla University and visiting professor grant from Department of Zoology, Faculty of Science, Kasetsart University for inviting Dr Diego Fontaneto to Thailand. Our special thanks go to Wijitra Choedchim and Watcharapong Boonnam for their help in field sampling throughout Thailand.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplemental data

Supplemental data for this article can be accessed here: https://doi.org/10.1080/14772000.2017.1353554.

Additional information

Funding

This research was financially supported by Science Achievement Scholarship of Thailand (SAST), Graduate School and National Research Universities (NRU), Prince of Songkla University and Research Career Development Grant, Thailand Research Fund (RSA6080032).