Reduced bird visits lower seed set of

Banksia robur in fragmented

heathlandRachele Wilson

Introduction: scope and purpose

How relationship

between plant and

pollinator is affected by

habitat fragmentation

Focus on a coastal

heath species –

Banksia robur

(Swamp Banksia)

Image source: (above) http://www.texas-wildlife.org/program-areas/category/property-rights

(below) http://www.anhs.com.au/images/

Previous research

Visits decline faster in:

tropical > temperate

vertebrates (birds,

bats) > invertebrates

Seed/fruit set decline

greater in self-

incompatible plants

Focus on herbs and

trees, forest and

grassland

Few coastal studies,

despite urbanisation

Image source: (above) Ricketts et al. 2008; (below) Montero-Castaño and Vila 2012

Coastal heathland

Sandy, low nutrient

soils

Habitat for

threatened species

Historically cleared

sand mining,

agriculture,

development

(~2 million ha)

endangered south

of Noosa

Eastern Ground Parrot

(Pezoporus wallicus)

Wallum Sedge Frog

(Litoria olongburensis)

Image sources: (parrot) http://www.environment.nsw.gov.au/threatenedspeciesapp/profile.aspx?id=10608#

(sedge frog) http://www.wildlife.org.au/projects/researchgrants/wallumsedgefrog.html

Research question

“Do pollinator behaviour and

reproductive success of B. robur differ

between intact and fragmented coastal

heath?”

Plant-pollinator interactions

Banksia robur

Fragmented vs. intact habitat

Methods: site selection Two coastal heath

sites (intact and

fragmented)

Five replicate plots

(20 × 5 m) per site

At least three

flowering plants per

plotWest of Dilli Village,

Fraser Island (Intact)

East Weyba Section,

Noosa N.P. (Fragmented)

Observations

40 × 20 min

observations

morning and

afternoon

twice per plot

Bird species –

foraging behaviour

duration

movement

between B. robur

flower spikes

number of visits

Images: background – visiting P. nigra; inset – observers. Courtesy of Marvin Scheiffer

Sampling 216 samples

up to 25 fruits per plot

Seed set

calculated as = follicles

per fruit (one seed per

follicle)

(a) (b)

(c)

(a) B. robur fruit with closed follicles; (b)

with open follicles; and (c), left – winged

seed, centre – separator, and right –

seedless wing.

Species Intact Fragmented Total

(a) White-cheeked Honeyeater (Phylidonyris nigra) 349 26 375

(b) Lewin’s Honeyeater (Meliphaga lewinii) 0 6 6

(c) Noisy Friarbird (Philemon corniculatus) 0 2 2

(d) Red-browed Finch (Neochmia temporalis) 1 0 1

Total 350 34 384

(a) (b) (c) (d)

Results: bird species observed

Image credits (a,b,d): David & Diane Armbrust, http://www.anhs.com.au/images/ (c): David Cook,

http://www.flickr.com/photos/kookr/2877951061/

Visitation rate

0

2

4

6

8

10

12

14

16

18

20

Intact Fragmented

Me

an

nu

mb

er

vis

its

/ 20m

in

Site

Frequency of bird

visits to flower spikes

was significantly

lower in fragmented

coastal heath

Mann-Whitney U Test (U(39) =

106, Z = -2.923, p = 0.010).

10 × more visits in

intact habitat

Duration of visits

Mean duration of

bird visits was similar

between sites

Mann-Whitney U Test (U(383) =

6 174.5, Z = 0.363, p = 0.716).

0

10

20

30

40

50

60

Intact Fragmented

Me

an

du

ratio

n o

f v

isit (

sec

)Site

Movement between flowers

Visitor travel

between flower

spikes was similar

across sites

Independent Samples T-Test

(t(9.5) = 2.247, p = .050).

0

5

10

15

20

25

30

35

40

45

Intact Fragmented

Me

an

pe

rce

nt

vis

its

with

in

ter-

flo

we

r

tra

ve

l (%

)

Average seed set

Seed set was

significantly reduced

in fruits from

fragmented sites

Independent Samples T-Test

(t(213) = 3.249, p = 0.001).

0

10

20

30

40

50

60

70

Intact FragmentedM

ea

n s

ee

d s

et

pe

r fr

uit

Site

Discussion: reduced visits

Less visits in fragmented

population,

e.g. B. goodii, B. cuneata

perceived decline in

nesting or foraging

resources

competition with

aggressive edge species

Forage in nearby

woodland

P. nigra dual habitat

Image source: (above) http://upload.wikimedia.org/wikipedia/commons/1/13/Noisy-Miner-juvenile.jpg

(below) http://farm7.static.flickr.com/6068/6158449973_74676438f7.jpg

Lower fertility

22% reduction in

average seed set

changes in

pollinator activity

disruption to

pollination

services

limited seed

production

Lower fertility

Similar to that found in

other fragmented

ecosystems:

tropical forest 20%

grassland 16%

Risk to demographic

turnover:

Low seed set low %

survival seedlings

E.g. up to 80%

seedling mortality

from kwongan

fragments

Alternative explanations

Smaller plant population size and

low density in fragmented site

‘inbreeding’ poor pollen

quality fewer seeds

E.g. B. sphaerocarpa

Physiological stress on plants (e.g.

drier conditions)

less resources, less output

Conclusion

Pollen limitation due to

habitat fragmentation

reduced bird visits lower

seed set of B. robur in

fragmented heathland

Potential risk to long-term

viability of population

Larger studies needed to

assess risk

Questions? Special thanks to:

Prof Helen Wallace

Ilee Sannholm

Marvin Scheiffer

Laura Simmons

Dr David Walton

Image (right) courtesy of Laura Simmons