Journal of Biogeography
SUPPORTING INFORMATION
Extreme population subdivision despite high colonization ability: contrasting regional
patterns in intertidal tardigrades from the west coast of North America
Søren Faurby and Paul H. Barber
APPENDIX S1 Supplementary materials and methods.
Tidal separation between taxa
To better characterize the exposure level of each sample containing tardigrades we searched the samples for
bdelloid rotifers and halacarid mites that generally are confined to the upper and lower part of the tidal zone,
respectively (Søren Faurby, pers. obs.). Bdelloid rotifers, however, only occurred in seven samples in total
and were therefore judged to be too rare to be informative in analyses of exposure which instead focused on
co-occurrence between halacarid mites (which occurred in 49 samples). The probability of similar cooccurrence patterns by random was estimated based on the binomial distribution. No analysis was
performed for Taxon 1 because the large abundance of this taxon means that the total average is too
influenced by the average for Taxon 1 to make comparisons between the two meaningful.
Taxon 2 was found between the sample site 1 and 13 and in these 13 sample sites we found
tardigrades in 91 samples and 36 of these also had halacarid mites (39.6%). Taxon 2 was found in eight sites
in six of them with halacarid mites (75%). Assuming an overall probability of 39.6% of mites in the samples
the probability of having mites in six or more out of eight samples with Taxon 2 is 4.71%
Taxon 3 was found between sample site 12 and 18 and in these seven sample sites we found
tardigrades in 64 samples and 11 of them also halacarid mites (17.2%). Taxon 3 was found in 16 sites but in
no cases co-occurring with halacarid mites (0%). Assuming an overall probability of 17.2% of mites in the
samples the probability of not having mites in a single of the samples with Taxon 3 is 4.89%
These data suggest that the distribution of the individual taxa is different and suggest that
Taxon 2 lives lower in the tidal zone and Taxon 3 higher in the tidal zone than Taxon 1. The inference of
Taxon 2 living lower in the tidal zone also makes sense by comparing with its sister Echiniscoides higginsi
which does not live in the tidal zone but instead occurs interstitially (Hallas & Kristensen, 1982).
28S amplification
To test for the presence of additional tardigrade lineages from DNA extractions where COI could not be
amplified, we also sequenced a region of 28S using the universal primers1274F and 689R (Markmann,
2000). Although these primers were originally developed for nematodes, they appear to work universally in
tardigrades (Jørgensen et al., 2010) and are also capable of amplifying a diverse set of protists and fungi
(Søren Faurby, pers. obs.) ensuring that any tardigrade species present will be amplified.
Only three specimens of Taxon 1 (one from San Diego and one from Dana Point) and one
specimen of Taxon 2 (from Gaviota) did not amplify for COI but did amplify for 28S. These three could be
assigned to taxa based on the unique 28S allele of each Taxon. Non-amplification was therefore judged to be
so rare that it could not be a problem.
Furthermore an additional taxon was recovered while sequencing 28S reactions. This
Taxon was recovered in four samples from Catalina Island. Based on comparisons with published
sequences the closest relative of this appears to be the North Atlantic Echiniscoides pollocki. We
refer to this additional taxon as Taxon 4 but will not discuss it in any detail.
References
Hallas, T.E. & Kristensen, R.M. (1982) Two new species in the tidal genus Echiniscoides from Rhode
Island, U.S.A. (Echiniscoididae, Heterotardigrada). Proceedings of the Third International Symposium on the
Tardigrada, August 3-6, 1980 (ed. by D. Nelson), pp. 179–192. East Tennessee State University Press,
Johnson City, TN.
Jørgensen, A., Faurby, S., Hansen, J.G., Møbjerg, N. & Kristensen, R.M. (2010) Molecular phylogeny of
Arthrotardigrada (Tardigrada). Molecular Phylogenetics and Evolution, 54, 1006-1015.
Markmann, M. (2000) Entwicklung und Anwendung einer 28S rDNA-Sequenzdatenbank zur Aufschlüsselung
der Artenvielfalt limnischer Meiobenthosfauna im Hinblick auf den Einsatz moderner Chiptechnologie. PhD
Thesis, University of Munich, Munich.