Habitat Preference for
Comanche Peak Prairie Clover (Dalea
reverchonii, Fabaceae) a rare
North Central Texas endemic
Allan D. Nelson and Samuel R. Kieschnick,
Comanche Peak prairie clover (Dalea
reverchonii) - decumbent growth
Flowering head of D. reverchonii
Rare Texas endemic due to habitat loss
and substrate specialization
Endemic to Wise, Parker, and
Somervell counties
Walnut Limestone Glade habitat
Rocky, shallow soil of glade and young D. reverchonii plants
Prairie Barren Habitat
Methods
1.
Censused both glade and barren for numbers of Comanche Peak
prairie clover in
 20 X 50 meter quadrats in both habitats
2.
Surveyed both glade and barrens using meter
squared quadrats for:
 presence and number of Comanche Peak prairie clover, amount of
coverage, associated species, and richness
 measured Comanche Peak prairie clover head diameter and head
length as well as counted head numbers for plants in quadrats
Census of Comanche Peak prairie
clover in Glade and Barren
Survey: Three 100 m transects in each habitat
Survey: 10 quadrats/transect-30/community
Census Results
Year
2010
2011
2012
Mean
Glade
754
731
848
778
Adjacent barren
58
108
159
108
Survey Results:
Mean number of Dalea reverchonii, richness, and percentage
cover per quadrats between the limestone glade and barren. P
values are from Mann Whitney tests for significance.
_______________________________________
Mean/quadrat
Glade
Barren
P-value
__________________________________________________________________
Number of D. reverchonii 1.1
Richness
5.4
Percent Cover
16.9
0.2
8.4
68.4
<0.001
<0.001
<0.001
-about 5 times as many D. reverchonii, richness was a little over 1/2, and vegetative
coverage was approximately 1/4 in glade habitats as compared to adjacent barrens
Survey Results:
Mean richness and percentage cover within glade quadrats that contained D.
reverchonii compared to those where plants were absent. P-values are from
Mann Whitney tests for significance and are <.0.001.
Mean
With D. reverchonii
Without D. reverchonii
Richness
6.7; n=37
4.5; n=53
Cover (%)
23.6; n=37
13.9; n=53
Within quadrats that contained D. reverchonii in glades, both richness and
percent coverage were significantly greater than those without Comanche Peak
prairie clover.
Survey Results:
Mean head number, head length (mm), and plant diameter (mm) for plants
occurring in a Walnut limestone glade and barren. P-values are from Mann
Whitney tests for significance.
______________________________________
Glade
Barren
P-value
_______________________________________
Mean Head number
Mean Head length
Mean Plant diameter
6.3
36.2
262.1
14.0
43.2
383.6
0.002
0.318
0.001
• Significant differences in head number and plant
diameter in comparison between the two habitats
with more heads and greater diameters in Barren
Species associated with Dalea reverchonii and number of times associated
species were found in quadrats that contained D. reverchonii in walnut
limestone glade and adjacent barren.
Walnut limestone glade
Adjacent barren
_________________________________________________________________________
Aristida purpurea var. nealleyi
4/81= 5%
1/39= 3%
Bromus japonicus
0
1/39= 3%
Dalea frutescens
1/81= 1%
0
Eleocharis acutisquamata
0
3/39= 8%
Erioneuron pilosa
3/81= 4%
0
Gaillardia pulchella
0
3/39= 8%
Minuartia michauxii var. texana
15/81= 19%
0
Plantago helleri
28/81= 35%
5/39= 13%
P. wrightiana
0
4/39= 10%
Sedum nuttallianum
4/81= 5%
0
Sida abutifolia
0
1/39= 3%
Tetraneuris linearifolia
15/81= 19%
10/39=26%
Thelesperma filifolium
9/81= 11%
2/39= 5%
Tridens albescens
2/81= 2%
9/39= 23%
Minuartia michauxii var. texana –
Common Associate
Tetraneuris linearifolia - Common Associate
Sedum nuttallianum and Plantago
helleri - Common Associates
Conclusions
• Seven times more D. reverchonii censused and
five times more sampled in the limestone glade
than the barren >> Better adapted to the glade
habitat, which has shallower soil, less richness,
and lower percentage of plant cover
• Support for the hypothesis by O’Kennon
(2010) that D. reverchonii preferentially
inhabits limestone glades
Conclusions
• Significant difference in richness and coverage
between the glade and barren with glade
having lower values of each >> Likely because
of thinner soils
• Within the glade, richness and percentage
cover was significantly higher in quadrats with
D. reverchonii >> It and associated species
likely colonized pockets of shallow soil within
the walnut limestone outcrop
Conclusions
• Significant difference in head number and
plant diameter for D. reverchonii in
comparisons of plants from barrens and glades
>> Glade plants tended to be younger and
smaller whereas barren plants were mostly
mature and there were few young plants
• Head length was not significantly different >>
Possibly because we only measured the
longest head associated with each plant
Acknowledgements
David Utley for access to his property.
Bob O’Kennon for helping us start the project
For field assistance during the project:
Volunteers from the North Texas Plant Conservation
Alliance: Dawn Hancock and Becky Nelson.
Undergraduate student: Cherie Porter.
Graduate students: Paige Cowley, Sara Harsley, Stephen
Henderson, Jeremy Munz, and Brian Scoggins.