Insect pathology -the early years

Population biology of Beauveria

Dave Chandler, Gill Davidson

University of Warwick

Anamorphic Ascomycete Entomopathogenic fungi

• Widespread in nature, especially soil.

• Range of species, different properties.

• Used as inundative biopesticides.

• Can be valuable components of IPM.

Chemical clones or bio-control agents?

• Inundative biopesticides: development = chemical model.

• Ignoring ecological attributes (Waage)– numerical response,

– trade offs,

– conservation control.

• Lack of knowledge: affects biocontrol efficacy & environmental risk evaluation.

Ascomycete entomopathogenic fungi

• Natural abundance? Diversity? Ecosystem function?

• Are they ecologically obligate pathogens?

• Determinants of population structure?

• Population dynamics?

• How does virulence evolve?

• Lack meaningful species definitions.

• Theoretical framework for predicting environmental (non target) impacts of biocontrol releases.

Work outline

• Studying natural popns. of fungi in soils, esp. Beauveria.

– Bidochka : biogeography of Beauveria & Metarhizium.

– Rehner: Beauveria phylogeny.

• Expt 1:– Examined Beauveria from culture collection: collected

from UK woodland & farm grassland.

• Expt 2:

– Sampling at a single farm site.

Galleria bait method

• Culture collection: Beauveria isolates from 9 woods & 11 grasslands.– Devon– Somerset– Gloucestershire– Herefordshire– Shropshire– Berkshire– Warwickshire– Leicestershire

Experiment 1: Beauveria biogeography?: national scale

• Culture collection: – Isolates from each location. – 117 total, 85 wood, 32 grass.

• Sequence data:– EF1a– 28s rDNA gp I intron– Beta tubulin, rDNA ITS– DNA lyase, Beta locus– Micro satellites.

Beauveria biogeography: national scale

EF1a woods & grassland(includes 1 sequence each from Rehner clades A – F)

B. scarabaeicola EFCC2533

D (B. caledonica) none

F (B. amorpha) none

E (Cordyceps sp.) none

A :28/56 from woods (exp 41/56)

100

100

100

63

98

88

100B: 20/20 from woods (exp 15/20)

C: 37 / 41 from woods (exp 30/41)

clustal W, distance (NJ)

Chi sq : habitat effect : p < 0.001 (pearson = 28, 2 df)

Stewardship12 ha

hed

ger

ow

Arable7 ha

Grassland 10 ha

Expt 2: Fungi from different habitats in close proximity: Warwick Dept. farm

Deep slade

Long close

Water meadows

Expt 2: Fungi from different habitats in close proximity

samples Beau Met P. fa P. fu Lec

arable 506 16 1 1 0 0

steward 240 28 0.5 0 0 0

grass 150 55 1 2 1 1

hedge 250 34 0 5 11 0

all 1146 28 0.6 2 3 0.3

Frequency of occurrence (%)

Chi square (pearson) 68.7, 9 df, p < 0.001

EF1a Warwick dept farm

Constructed tree (NJ, distance) with Beauveria isolates:Hedgerow 24Arable 26Stewardship 23Grassland 26

Total 99

EF1a Warwick dept. farm: hedge vs. fields(includes 1 sequence each from Rehner clades A – F)

B. scarabaeicola EFCC2533

D (B. caledonica) none

F (B. amorpha) none

E (Cordyceps sp.) none

A :7/77 from hedge (exp 19/77)

100

100

100

64

97

96

100B: 1/2 from hedge

C: 16 / 20 from hedge (exp 5/20)

clustal W, distance (NJ)

Chi sq : habitat effect : p < 0.001 (pearson = 47, 6 df)

Simplified conclusions

• Genetic groups in Beauveria have different habitat preferences. Why?

• Warwick farm study:– Habitat type affects frequency of occurrence

of fungi.– Diff genera have diff habitat preferences?

Why does this matter? • Bio-prospecting.

• Conservation control (habitat manipulation).

• Informs risk assessment.

• Generation & maintenance of diversity in an ‘asexual’ organism.

acknowledgements• USDA Steve Rehner

Thanks for your attention!