| BEN |
| BOTANICAL ELECTRONIC NEWS |
|---|
| ISSN 1188-603X |
No. 137 May 26, 1996
Over the last 25 years, I have been examining the evolution of endemic threespine stickleback on the Queen Charlotte Islands. The stickleback provide a particular interesting case of adaptive variation as each lake contains a distinctive form of stickleback, quite comparable to the morphological variability in Darwin's finches. Most of the highly divergent stickleback, including giant forms and unarmoured forms occur in the bog lowlands on the north-eastern corner of Graham Island. We have been able to associate many of the morphological differences among the populations to distinct predation regimes in each habitat.
During the course of these studies, which involved samples from over 300 ponds and lakes, I discovered some unarmoured stickleback in several ponds on the north-eastern corner of Graham Island. In one of these ponds (Rouge Pond), many of the fish were covered in a thin gelatinous envelope in which were embedded numerous vegetative microcysts. These were subsequently identified by Max Taylor (UBC) as a dinoflagellate of unknown affinity. Numerous SEM and TEM studies by John Buckland-Nicks (StFX) have shown that these cysts, which contain chlorophyll, are unlike other dinoflagellate fish parasites. The cyst contains a rigid fenestrated matrix penetrated by cytoplasmic processes that extend from the dinokaryotic nucleus and associated chloroplasts. These traits, in addition to amoeboid stages, a very short duration trophont and a variety of resting cysts suggest associations with the Phytodiniales while a temporary dinokaryon and palintomic sporogenesis suggest affinities to the Blastodiniales. Although there remain numerous ambiguities in its higher level associations, we have initiated formal taxonomic description of this dinoflagellate.
Response of the fish to the infection is extensive epithelial hyperplasia which produces a thick layer of cells over the entire fish in which the dinoflagellates are embedded. Even in cases of extensive infection, the fish exhibit no obvious behavioral signs of stress, suggestive of a symbiosis or non-pathological association.
My student, P. O'Reilly, undertook mtDNA work of the stickleback populations and found that the majority of populations have a mtDNA lineage that is very similar to that found in the ancestral stickleback found in marine waters surrounding the Queen Charlottes. However, he also found a highly divergent mtDNA lineage (>2.0% sequence divergence) in a several populations. The stickleback from Rouge Pond, which have the dinoflagellate association, were monomorphic for this rare lineage. More recent work by G. Orti (Stony Brook) shows that this rare haplotype also characterizes stickleback from Japan and several sites in Alaska, suggestive of a previously wide distribution, but now restricted in space.
We are not yet sure whether the combined presence of this highly atypical dinoflagellate with the rare mtDNA haplotype of the stickleback in Rouge Pond are merely coincidental events that occurred after postglacial colonization or whether the biogeography of both were bound together during the Pleistocene in an ice-free refugium suspected of occurring between the Queen Charlotte Islands and the mainland.
The following references provide more detail on the dinoflagellate/stickleback associations.
These papers provide more detail on the host populations:
My colleague Joe McDermott and I are doing a study on the population structure of Thamnolia vermicularis from a genetic point of view. The presumptive sterile nature of this lichen suggests that there would be an overall low level of variation. To test this, we are using PCR based methods to investigate variation in the ribosomal RNA genes (primarily in number and location of introns in the coding regions) and in the spacer DNA between the genes (the ITS and IGS regions). Through the generosity of a number of helpful individuals, we have been able to examine nearly 75 specimens from various distant places. To improve the geographic representation of the study, we would like to have at least about 250 samples worldwide. I'd like to ask the members of this group for help in obtaining additional specimens, especially of material from the southern hemisphere.
Although fresh material is better, we have worked successfully with older material (a specimen from the 1930's is the oldest to date). Whatever the age, only a small amount of material is needed (one or two thalli). If you can spare a small amount of material from your collection, or if you can recommend someone we should contact, please e-mail me at the address below.
Thanks very much for your help.
This is the latest addition to the popular series of field guides to plants of British Columbia and the Pacific Northwest [see BEN 31, 75, 114, and also 125 & 132]. The guide "features nearly 700 species of plants commonly found in the region from the crest of the Rockies west to the Coast Mountains, including the interior of Washington and Idaho." The book contains more than 1000 photographs and over 700 line drawings.
This is a great series of field guides, highly praised by their users and reviewers. The Southern Interior guide is possibly the best in the series, its editors and writers have done an excellent job. The guide was produced by ten authors (three of them edited the book). I could not find who wrote what part, but you can feel Anna Roberts' fine hand in the contribution to sedges, Trevor Goward's logical participation on lichens, and Dr. George Douglas's treatment of Asteraceae. I was able to detect Dr. Wilf Schofield's excellent contribution to the treat- ment of bryophytes, although he is listed as a co-author only in the Acknowledgements.
What should I say more? This is an excellent book. It is loaded with information, it's easy to use, and yes, it has rounded corners.
The correct e-mail address of Sybille Haeussler is:
Sybille Haeussler - 847-9451 - sybh@netshop.net
Submissions, subscriptions, etc.: aceska@freenet.victoria.bc.ca.
BEN is archived on gopher freenet.victoria.bc.ca. The URL is:
gopher://freenet.victoria.bc.ca:70/11/environment/Botany/ben. Also archived at http://www.ou.edu/cas/botany-micro/ben/