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How many freshwater diatoms are pH specialists? A response to Pither & Aarssen (2005)
Author(s) -
Telford Richard J.,
Vandvik Vigdis,
Birks H. J. B.
Publication year - 2006
Publication title -
ecology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.852
H-Index - 265
eISSN - 1461-0248
pISSN - 1461-023X
DOI - 10.1111/j.1461-0248.2005.00875.x
Subject(s) - diatom , taxon , ecology , generalist and specialist species , niche , biology , habitat
Pither & Aarssen (2005) propose a null model approach to assess the proportion of niche specialist taxa along ecological gradients. They apply this methodology to a large data set of lacustrine diatom assemblages and conclude that a majority of the taxa are generalists on a pH gradient. This conflicts with previous work, which shows that many diatom taxa have a statistically significant relationship with pH. We demonstrate the methods used by Pither & Aarssen (2005) have a high Type II error for rare taxa, and that this problem is compounded by the non‐uniform sampling of the pH gradient which effectively precludes acid‐lake specialist diatoms from being recognized as such. We re‐analyse the data used by Pither & Aarssen (2005) and show that most of the diatoms have a statistically significant relationship with pH, and we thus refute their conclusions that few diatom species are specialists.