A bit of history repeating: Lake Baikal diatoms astonish researchers over the centuries

“… a small bottom sample … from the depth of 33 meters taken near the Olkhon Gate of Baikal Lake on July 29th 1916. I have examined about a hundred of microscopic slides from this place and have taken great care to identify and illustrate the forms… The result was unexpected; I have identified 304 species, varieties and forms, among which 148 are new” (Boris V. Skvortzow 1937)

Aulacoseira baicalensis Photo: Irkutsk State University

I had to wait a bit before I got my hands on the recently published Lake Baikal: Hotspot of Endemic Diatoms I. In this impressive body of work, Maxim Kulikovskiy and colleagues, document several hundred species of diatoms from benthic communities around the lake. In the 600 or so pages, the authors describe and illustrate 222 species and 10 genera as new to science! Moreover, they report as many as 170 taxonomic entities yet to be identified or described. If you are not a diatomist, or better a diatom taxonomist, you would probably be surprised when I say that I wasn’t instantly amazed by these numbers. After all, this is the norm for most volumes of Iconographia Diatomologica. For this I blame the extremely fluid state that diatom taxonomy enjoys/suffers from over the past two-three decades. New species are being described left and right, especially from exotic, previously un(der)studied areas, and often without observations of type material or explicit statements of species concept (guilty my self).

After a bit more reading however, some excitement about this book started to creep in. The first instance of ‘wow’ came when the authors mentioned that all newly described species come from only 27 genera! I know, first hand, that benthic diatoms in ancient lakes are very diverse, but 222 new species from just 27 genera? That was somewhat unexpected. What should we expect when more genera are worked out? Then I flipped through and stumbled upon my second ‘cool’ moment: these results are based on observations of just 28 samples; mainly from the Ushkaniy Islands in the northern basin. So all this diversity is found in a fairly small number of samples coming from a more or less limited area in the lake. Again, the question begs, what will happen when we scale to the entire lake?

What made me really appreciate this book was the realization that some of the samples used are original material collected by Skvortzow and Skabitschewsky. Kulikovskiy and colleagues managed to dig out old material and at least had the opportunity to compare their observations to the specimens that the pioneering researchers would have been looking at! I fully understand that not all type material for Lake Baikal is available, and that each newly described taxon cannot be compared with the rigor we’d like to descriptions and line drawings from 70-80 years ago. However, the information presented in ‘Lake Baikal: Hotspot of Endemic Diatoms’ must represent a better synthesis of diatom taxonomy than it would have been without Skvortzow’s and Skabitschewsky’s material. Kudos, Maxim et al.!

Kulikovskiy and colleagues hazard a guess that Lake Baikal harbors up to 1500 diatom species. Even if the real (probably unknowable) number of species is ten times smaller, the sheer variability of forms indicates how little we still know about Baikal’s biodiversity.

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4 Responses to A bit of history repeating: Lake Baikal diatoms astonish researchers over the centuries

  1. lyampolsky says:

    This certainly raises the question about a)validity of species description and, even if that many species are biologically valid, b)usefulness of such detailed taxonomy for ecological application and even conservation. Consider the situation with, say N.American unionid mussels. “Splitters” tradition (based on description of new species being professionally rewarded – I think taxonomists were awarded tenure for description of new species in the first half of 20th century) lead to description of several hundred species often different from each other only by non-overlapping ranges. This, of course, creates artificially high levels of endemism and vicariance. Typological view of species, i.e., largely ignoring the fact that intraspecific genetic variation exists, does not make the situation any easier. In my experience, hundreds of N.American unionids probably represent 50 or 60 “good species”, still an impressive species flock, but a far cry from 300 often recognized. Is there a similar story with Baikal endemics? There an expectation of high species richness and high endemism. This creates a pressure to describe every slight variation (biogeographic, genetic or entirely environmental) as a new species. There are ~250 “good” species of amphipods in Baikal. Yet, there are claims that there may be as many as 2000 amphipod species in Baikal, a claim, which is difficult to falsify, but equally difficult to believe in. Is there, perhaps, something similar with diatoms?

    • lyampolsky says:

      PS: and even when such closely related species are indeed real, conservation efforts are better based on functional, not taxonomic categorizations…

    • Teofil says:

      I couldn’t agree with you more. What makes the problem with diatoms even worse is that diatom taxonomy almost exclusively relies on the silica cell wall. i.e. we are describing extant species based on their dead parts knowing almost nothing about genetic or phenotypic intraspecific variation. Species numbers could be heavily inflated, but as you say we can’t really know.

      Having said that I think it is still good to have these types of monographs. Even if this taxonomic practice might not be the most useful or biologically meaningful. This way at least we describe diversity of any kind. Regardless whether we bin variations in the species or population category. Personally I don’t care too much about the numbers of species, but I admire the morphological diversity. My (cautious) praise for this book is based solely on that: description of huge amounts of diversity.

  2. Pingback: Bringing the pieces together: the Baikal team face-to-face in Michigan | Lake Baikal Dimensions of Biodiversity

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