Tag Archives: Tandy Hills Prairie

Looking for ants that define prairies

My analysis right now is focused on considerations of alpha and beta diversity. I have been held up by computer issues but here are the initial results of a form of discriminant analysis on ant species occurrence in 21 sites over 3 months in the Fort Worth/Arlington, Texas area.

I used both a biplot scaling (for short gradients — which I think is most appropriate) and a Hill’s scaling (which is meant for long gradients) and got the same results. So, I will continue these analyses with the biplot scaling.  This initial work was done using soil type as the clustering category. (I will continue DA using ecological group, habitat type (disturbance), and the presence of the Comanche harvester ant as clustering groups. So, several more analyses to do.)

This first summary table and plots are for species occurrence data from 21 sites. The analysis called a CCA in CANOCO, the program I am running (CCA is a general form of CVA, and otherwise called a discriminant analysis). I am using this as a clustering analysis: do the ants cluster by soil type basically. Turn it the other way round: Knowing the ants present, can I say what the soil is? Are the ants bioindicators?  This first analysis uses all the species presence data.

Here is the summary table:

**** Summary **** of CCA for Soil Clustering, biplot scaling, all species

Axes                                    1      2      3      4  Total inertia
Eigenvalues 1.000  0.970  0.770  0.706         6.000
Species-environment correlations  1.000 0.985 0.877 0.840 6.000
Cumulative percentage variance of species data                16.7   32.8   45.7   57.4
Cumulative percentage variance of species-environment relation   22.9   45.1   62.7   78.8
Sum of all eigenvalues      6.000
Sum of all canonical eigenvalues      4.370

And the biplot of data: messy, messy, messy. The red are the species, the triangles with the S followed by a number are the soils.

For the second analysis, I only included species that made up more than 1% of the total ants collected from that sample.

Here’s the summary table:

**** Summary Of CCA with Ecological Descriptors ****






Total inertia







Species-environment correlations 





Cumulative percentage variance of species data





 Cumulative percentage variance of species-environment relation





Sum of all  eigenvalues






Sum of all canonical     eigenvalues     






And the triplot — here with the addition of circles with numbers — these are the samples.

I haven’t reached interpretations or conclusions yet. This is still pretty raw data…

Stratford and Tandy Hills Prairie Ants

I am completing the ant identifications for the prairie and forest in the Southwest Nature Preserve in Arlington, Texas and the additional prairies, Statford  and Tandy Hills, in Fort Worth, Texas. I believe I have found another Temnothorax species which I have not been able to identify and another Pheidole species. This is quite exciting. No Pogonomyrmex ants are found in the Stratford or Tandy Hills Prairies.