MONOTOCA SCOPARIA TWO FRUITS

Betsy R. Jackes

James Cook University

Peter G. Kevan

University of Guelph

MONOTOCA SCOPARIA

• Subfamily Styphelioideae, family Ericaceae• Shrubs to 1.3 m tall, lignotuber present• Inflorescence axillary, few-flowered spikes

often clustered• Functionally dioecious or ?• Ovary 1-locular• Fruit a drupe, yellow to orange

OBSERVATION

ALL REPRODUCTIVE PLANTS NEAR PALUMA PRODUCED FRUITS.

MAIN QUESTION

IS MONOTOCA SCOPARIA GYNODIOECIOUS, FUNCTIONALLY DIOECIOUS OR?

Townsville

Wet Tropics bioregion

Where are we?

BRISBANE

Queensland

STUDY SITES

• THREE POPULATIONS ALONG A DECREASING RAINFALL GRADIENT

• QUADRAT 30 X 18 M

• ALL PLANTS AT EACH SITE SEXED AND TAGGED AND CO-ORDINATES RECORDED

• ARE SEXES RANDOMLY DISTRIBUTED OR NOT?

Site 1 19o 00’ 27.8”S 146o 05’ 31.3”E

Distribution Site 1

Site 2 19o 00’ 08.1”S 146o 04’ 48.7”E

Distribution Site 2

Site 3 18o 59’ 59.5”S 146o 04’ 29.5”E

FEMALE PLANTS (WITH STAMINODES)MALE PLANTS (WITH FERTILE STAMENS)

WERE RANDOMLY DISTRIBUTED AT ALL SITES DESPITE VARIATIONS IN TOPOGRAPHY AND MOISTURE LEVELS

IS THERE A DIFFERENCE IN THE NUMBER OF FLOWERS PRODUCED PER SEX?

For each sex, 10 plants tagged, 10 sprigs per plant tagged, each sprig 10 cm long, all flowers counted

Female mean 1381, SD 196Male mean 1295, SD 240No significant difference

No significant difference

Female sprigs Male sprigs

♀

Male flower, c. 2.1 mm long

Female flower c. 1.5 mm long

DO MALE AND FEMALE PRODUCE EQUAL QUANTITIES OF NECTAR?

Sprigs cut and placed in water, covered with a plastic bag, left overnight

Then checked under a dissecting microscope and scored for the amount of nectar present.

1 = brim full

2 = well above ovary but not overtopping the style

3 = visible sparkle at base of corolla tube4 = no visible nectar

NECTAR RESULTS

Female n=150 Male, n= 192

1 (none visible) 56 02 49 23 32 724 (brim full) 13 96

Female flowers produced significantly more nectar than male flowers

POLLEN

Pollen from 10 plants, 4 flowers per plantStained with Alexander’s Stain – grains

unstained or partially stained and irregular in shape recorded as aborted.

Pollen grains per flower ranged from 2437 to 13375 mean 8762

% fertility or non-aborted grains = 81.9%

TWO FRUITS

• Fruit from female plantfirmly attached to parentglobular to pear-shaped2.4-2.7 mm long, 2.1-2.4 mm wide

• Fruit from male plantweakly attached to parentcylindrical2.5-3 mm long, 1.25-1.5 mm wide

Female plant

Female, mature and maturing

Male, mature and maturing

FRUIT SET

• All fruit present on the tagged plants were collected after 2 months.

• Percentage fruit set based on the number of buds and flowers recorded for each plant.

• Combined data for sites 1 and 2Female 27.11%Male 11.41%

‘female’ ‘male’

Presence or absence of a well-developed embryo

• Fruits collected from both sites 1 and 2

• Method 1: Fruits cut in half and nature of the embryo noted microscopically, n=20

• Method 2: Fruits cleared with methyl salicylate (modified from Stelly et al. and Scriballo & Barrett). All questionable results confirmed by sectioning

• Method 3: squishing

• Sex Site # examined #well-developed embryos

female 1 154 872 296 142

450 229

male 1 327 02 216 0 (2 partial)

543 0

Note: No females without partially developed embryos

‘female’ seeds with endocarp

2.1-2.5 mm long, 1.2-1.5 mm wide

FLORAL VISITORS

• 20 plants, 10 of each sex, 4 sweeps per plant• All insects captured and examined for pollen

load• Only Trigona ?carbonaria carried Monotoca

pollen.• Male plants, 21 bees captured

• 10 with pollen, 11 lacking pollen• Female plants, 23 bees captured

• 7 with pollen, 16 lacking pollen

CONCLUSIONS

• Monotoca scoparia is functionally dioecious, sexes are randomly distributed

• Two fruits develop but no viable embryos in ‘male’ fruit

• Flowers differ in size and shape with sex• Female flowers produce considerably more nectar

than male flowers• Trigona ? carbonaria is the pollinator