18 January 2011

Texas crayfish distribution

For a project I was working on, I had reason to compile the county records of crayfish contained in the very good and useful book Texas Crawdads (self-published, but still available for purchase online). The book shows a map with all the Texas counties that have crayfish, but I wanted to see the biodiversity “hotspots.” Because the book has county maps for most of the species, I was able to extract the information from them and compile it into a quick and dirty choropleth map:


The spreadsheet with all the data is available here: https://spreadsheets.google.com/ccc?key=0ApOCD9JZBwq0dGx1T3NfTFRIa05wUnBZMmxyM3k5Y0E&hl=en

The county with the most species, Brazoria, has ten different crayfish species. Van Zandt county (the one white patch in the north east) is shown in a summary map as having a crayfish record, but none of the genus or species maps show anything there.

This map underestimates the number of crayfish species in some counties, particularly in North and West Texas. There are seven (out of 39) species that the authors don’t give county maps for, though where they do mention specific counties in the text, I put that in my spreadsheet).

In particular, there are two very wide-ranging gray crayfish, Procambarus curdi and P. simulans, that didn’t warrant their own county maps, just a combined map with a third species (which did get its own separate map). P. simulans is described as having the widest distribution, so every county that is shown in Texas Crawdads as having “grays” with is assumed to have P. simulans. Those entries are marked with an asterisk.

What does this have to do with Marmorkrebs? It’s sort of related to a paper that’s in press right now about potential distribution of Marmorkrebs in the United States and elsewhere. But mainly, I just wanted to share the compilation in case someone else finds it useful.

References

Johnson SK, Johnson NK. 2008. Texas Crawdads. Crawdad Club Designs, College Station, Texas. http://www.texascrawdads.com

Johnson SK, Johnson NK. 2009. Texas Crawdads Supplement. http://texascrawdads.com/yahoo_site_admin/assets/docs/2009_Texas_Crawdads_Supplement.73195937.pdf

1 comment:

N. Kurt said...

P. simulans is indeed very widespread in Texas and expected in most counties, from East Texas all the way to the Pecos drainage in West Texas. In South Texas it is replaced by what is referred to currently as P. regiomontanus. I have not personally collected it in South Texas from below San Antonio in the San Antonio River drainage to the Rio Grande. I have collected P. regiomontanus (which may actually be an undescribed species similar to the P. regiomontanus occurring in Mexico) as far north along the Texas Coast as San Patricio County. Nice Map. Kurt Johnson