Mims

PREDATOR VS. MONSOON: THE ROLE OF BIOTIC AND ABIOTIC DRIVERS

IN SHAPING AQUATIC INVERTEBRATE

COMMUNITIES IN DESERT ENVIRONMENTS

Jessie HaleMeryl Mims, Michael Bogan, Julian Olden

Kahrs

Mims

IUCN

D. Kahrs

- Introduced in 1926 for food, naturally spread

- Considered a nuisance species starting in 1960s

- Bullfrog removal costs about $20,000 annually in Southeast Arizona

AZGFD

monteverde2000

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

Ave

rage

Mo

ntl

y P

reci

pit

atio

n (

inch

es)

Elgin, AZ

EARLY MONSOON LATE MONSOON

Questions1. What is the effect of bullfrogs on aquatic

invertebrate communities?

2. What is the effect of monsoonal seasonality on aquatic invertebrate communities?

3. What is the relative importance of these two factors in shaping aquatic invertebrate communities?

4. How do bullfrog presence and monsoon seasonality affect aquatic invertebrate community composition?

Hypotheses1. Lower invertebrate abundance and richness in tanks with bullfrogs

0

500

1000

1500

2000

2500

3000

3500

Bullfrog Control2. Higher invertebrate abundance and richness in late monsoon

3. Monsoon seasonality will be of higher relative importance in aquatic invertebrate communities

0

500

1000

1500

2000

2500

3000

3500

Early Late

Pre

cip

itat

ion

Time

United States

Mexico

- Standardized sampling: sampled same area in each tank

- Pooled samples- Used serial rinsing

method

0

2

4

6

8

10

12

14

0 50 100 150 200 250 300 350 400 450 500 550

Nu

mb

er

of

Taxa

Number of Individuals Sampled

Species Accumulation Curve

Subsample Count= 500 individuals

0

1000

2000

3000

4000

5000

6000

Early Late

Ab

un

dan

ce/

sam

plin

g ar

ea

(8

34

.8L)

Monsoon

Invertebrate Abundance

SD= 1409.5

SD= 2634.1

0

5

10

15

20

25

30

35

Early Late

Ric

hn

ess

/sam

plin

g ar

ea

(83

4.8

L)

Monsoon

Invertebrate Richness

SD=6.7SD= 8.1

0

1000

2000

3000

4000

5000

6000

7000

Bullfrog Control

Ab

un

dan

ce/s

amp

ling

are

a (8

34

.8 L

)Invertebrate Abundance

SD=1311.5

SD=2383.5

N=3

N=3

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 5-6 10-50 100s-100,000s

Log

Ab

un

dan

ce/s

amp

ling

are

a (8

34

.8 L

)

Estimated Number of Bullfrogs

Invertebrate Abundance

Early

Late

SD (early)= 0.009SD (late)= 0.30

0

5

10

15

20

25

30

Bullfrog Control

Ric

hn

ess

/sam

plin

g ar

ea

(83

4.8

L)

Invertebrate Richness

SD= 8.8 SD= 4.4

N=3N=3

0

5

10

15

20

25

30

35

0 5-6 10-50 100s-100,000s

Ric

hn

ess

/sam

plin

g ar

ea

(83

4.8

L)

Estimated Number of Bullfrogs

Invertebrate Richness

Early

Late

SD (early)= 4.5SD (late)= 5.0

Conclusions

1. Negative relationship between number of bullfrogs and richness/abundance

2. Monsoon seasonality not as much of a driver as we hypothesized, possibly due to low sample sizes

3. Evidence for differentiation in aquatic invertebrate community composition between control and bullfrog tanks

Management Implications

• Complete removal of bullfrogs may not be necessary (target gravid females and egg masses)

• Out of 26 known stock tanks in the area, it was difficult to find tanks with bullfrogs

Thank you!

• Meryl Mims, Mike Bogan (UCSB) & Julian Olden

• Matt Brawn & Kurt Bahti(AZGFD)

• Scott Kerr (Parker Canyon Lake Store)

• SAFS

• Greg Jensen

Questions?