Biology Reference
In-Depth Information
The most complex, well-documented example is provided by the
soapberry bug (
Jadera haematoloma
), a true bug (Order Hemiptera) whose
native North American hosts are the soapberry tree (
Sapindus saponaria
)
in the south-central United States and the balloon vine (
Cardiospermum
corindum
) in southern Florida (Carroll and Dingle 1996). The soapberry
bug feeds on the seeds of these plants by using a tubular beak to pierce
the fruit wall and gain access to the seeds, which are then liquified and
sucked out.The bug's beak length must thus be adapted to the thickness
of the fruit wall. The average beak lengths of soapberry bugs living on
the balloon vine are significantly longer than those living on the soap-
berry tree, corresponding to the balloon vine's larger, thicker walled
fruits (table 13.1).
Several exotic plants of the family Sapindaceae have been introduced
to the southern United States, and soapberry bugs have adopted them as
hosts (Carroll and Dingle 1996). The small-fruited flamegold tree (
Koel-
reuteria elegans
) has been introduced to peninsular Florida, near the region
where the native host plant is the balloon vine. A clear pattern of evolu-
tionary adaptation to this new introduced host is evident (table 13.1).
Soapberry bugs feeding on the flamegold tree have evolved beaks more
than 25% shorter than those feeding on balloon vines (Carroll and Boyd
Table 13.1.
Fruit radius of native and alien plants of the family
Sapindaceae, together with beak lengths of soapberry bugs feeding
on these hosts. (Data from Carroll and Dingle 1996.)
Fruit
Beak
Host plant
Status
radius (mm)
length (mm)
F
LORIDA
Balloon vine
Native
11.92
9.32
(
Cardiospermum corindum
)
Flamegold tree
Alien
2.82
6.93
(
Koelreuteria elegans
)
S
OUTH
-
CENTRAL
U
NITED
S
TATES
Soapberry tree
Native
6.05
6.68
(
Sapindus saponaria
)
Goldenrain tree
Alien
7.09
7.23
(
Koelreuteria paniculata
)
Heartseed vine
Alien
8.54
7.80
(
Cardiospermum halicacabum
)
