Dipodomys spectabilis: Ecosystem Engineers
A look at Invertebrate Richness and Abundance
By: Scott Johnson Mentor: Andrew Edelman
Dipodomys spectabilis
Banner-tailed Kangaroo Rat
Granivorous rodent Desert Grassland
Ecosystem Ecosystem Engineers
Building Microhabitats
Construct Mounds Earth slightly raised off
the Ground Several entrances
scattered across the mound
Usually One K-rat per Mound
Supporting Evidence
Thomas J. Valone, 1997
– Ant Correlation Hawkins and Nicolleto,
1992– Mounds effect spatial
organization of ground dwelling animals
Shawn Whiteman, 2007– Reptile Diversity
Species Richness
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
Occupied Random
# o
f S
pec
ies
Abundance
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
Occupied Unoccupied Random
(Whiteman 2007)
Unoccupied
Research Questions
How do mounds built by Dipodomys spectabilis influence invertebrate diversity?– Is overall richness and abundance at both
occupied and unoccupied mounds higher than away from the mounds at the random grass sites?
– Is overall richness and abundance at occupied mounds higher than unoccupied mounds?
Methods
Set up pitfall traps to catch mainly terrestrial invertebrates
45 sites; 15 occupied mounds, 15 random sites, and 15 unoccupied mounds
Random Sites set up at least 20m away Two pitfall traps at each site, totaling 90 traps,
opposite each other at random directions Traps opened for five to six day periods Five total collections on 7-2, 7-9, 7-16, 7-23, 7-30 Traps open a total of 27 days
Methods, cont.
Two Solo Cups ¼ full with Propylene Glycol
Pitfalls covered with ceramic tile to keep out debris and rain
One meter plot around each trap measured for percent cover of grass, forbes, detritus, and bare ground
Mound diameter measured and holes counted
The invertebrates identified at the UNM arthropod museum by Dr. Brantley
Results
Eleodes sp. Elateridae Scolopendra polymorphaEdrotes rotundus Dasymutilla vestita Eremobates sp.Sphecidae Vaejovis coahuilae LycosidaeEleodes longicollis Arenivaga erratica MyrmeleontidaeCeuthophilus pallidus Psilochorus imitatus Pasimachus sp.Psoloessa sp. Ophryastes globularis Sphaeropthalma sp.Cicindela punctulata Pompilidae Melanastus sp.Typhoctinae Scutellaridae Amphitornus
coloradus Gryllus sp. Tachinidae Emblethis vicariousCymatodera neomexicana Unknown Fly 1Cicadellidae Epicauta sp. ChloropidaeNoctuidae Unknown Moth TachinidaeLygaeidae Chrysopidae Araeoschizus sp.Trombidium sp. Efferia sp. Dactylotum bicolor
Reticulitermes tibialis Phyllophaga sp. Xanthippus corallipesCremastocheilus sp. Tingidae Omorgus sp.Litaneutra minor Nicrophorus guttulus Trimerotropis pallidipennisMelanoplus sp. Trachyrhinus marmoratusSyrphidae Phrynotettix robustus Orthoporus ornatusLatrodectus hesperus Parabacillus coloradus Tropidolophus formosus
Helluomorphoides sp. Dasymutilla sp. Unknown Fly 2
All three types Occupied only Occupied and Unoccupied Unoccupied OnlyUnoccupied and Random Random Only Occupied and Random
Invertebrate List
Invertebrate Average Richness
0
5
10
15
20
25
30
1
Richness
# o
f S
pe
cie
s
Occupied Unoccupied Random
F = 3.2, P = 0.05
a b b
Invertebrate Total Richness
0
10
20
30
40
50
60
Richness
# o
f S
pec
ies
Occupied Unoccupied Random
Invertebrate Total Abundance
0
500
1000
1500
2000
2500
3000
Abundance
# o
f In
div
idu
als
Occupied Unoccupied Random
Invertebrate Average Abundance
0
50
100
150
200
250
Abundance
# o
f In
div
idu
als
Occupied Unoccupied RandomF = 12.8, P < 0.001
a b b
Mound size
3
3.5
4
4.5
t = 0.5, P = 0.6
Mound type
Dia
me
ter
Occupied Unoccupied
Number of Mound Entrances
0
5
10
15
20
25
# B
urr
ow
Ho
les
Occupied Unoccupiedt = 1.9, P = 0.06
a b
a a
Vegetation Cover Over Pitfall Traps
0
10
20
30
40
50
60
70
80
90
F = 31.0, P < 0.001 F = 1.5, P = 0.23 F = 12.5, P < 0.001 F = 6.6, P = 0.003
% C
ove
r
Occupied Unoccupied Random
grass forbes detritus bare ground
a
b
c
a a a
a a
b
a
b b
Discussion
Statistically, Occupied mounds had significantly more diversity in average richness and average abundance than Unoccupied mounds or Random grass sites.
Occupied and Unoccupied mounds were similar in size, but Occupied mounds had more openings.
The type of vegetation cover over Occupied mounds differed from Unoccupied mounds and the Random Grass Sites.
Discussion
How do mounds built by Dipodomys spectabilis influence invertebrate diversity?
– Is overall richness and abundance at both occupied and unoccupied mounds higher than away from the mounds at the random grass sites?
No. Richness and Abundance at Occupied mounds are significantly higher.
Unoccupied mound diversity is similar to diversity at the Random site, though the components of the diversity differs.
Unoccupied mound data tends toward an intermediate trend.
Discussion
How do mounds built by Dipodomys spectabilis influence invertebrate diversity?– Is overall richness and abundance at occupied
mounds higher than unoccupied mounds? YES.
Conclusion: The Why
Dipodomys spectabilis altered their surroundings creating microhabitats for invertebrates.
Microhabitat– Unique nutrient, water, and light levels– Soil disturbances on and near the mounds
(Guo 1996)
These microhabitats are important to the biodiversity of invertebrates in both abundance and richness
Acknowledgments
University of New Mexico Sevilleta National Wildlife Refuge National Science Foundation US Fish and Wildlife Services Andrew Edelman Jennifer Johnson Dr. Scott Collins Dr. Sandra Brantley The UNM Arthropod Museum Shawn Whiteman Cathy McQueen Mike Friggens John DeWitt Andrew Rominger 2007 Sevilleta REUs 2007 Sevilleta Interns
References
Best, Troy L (1988) Mammalian species dipodomys spectabilis. American Society of Mammologist 311:1-10
Guo, Qinfeng (1996) Effects of bannertail kangaroo rat mounds on small-scale plant community structure. Oecologia 106:247-256
Hawkins LK, Nicoletto PF (1992) Kangaroo rat burrows structure the spatial organization of ground-dwelling animals in a semi arid grassland. Arid Environment 20:199–208
Valone, Thomas J (1994) Interactions between rodents and ants in the chihuahuan desert: an update. Ecology 75:252-255
Whiteman, Shawn (2007) [enter thesis] Senior thesis