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

OccupiedRandomUnoccupied

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