基本HTML版本
Bioscience Methods 2014, Vol.5, No.3, 1-11
http://bm.biopublisher.ca
7
2.3 Effect of abiotic factors
The relationship between the climatic factors and
fruit fly population dynamics is shown in Figure 3.
Tephritid populations were generally regulated by
changes in rainfall, temperature and relative
humidity. The fly species generally appeared at low
numbers at the start of the rainy season, became
more abundant at the peak of the rains and
drastically declined at the end of the rains. Between
the months of January and March, low precipitation
coincided with minimum relative humidity with
increasing air temperature. During this period,
average infestation levels of both
B. invadens
and
C.
cosyra
were as low as 10.0 and 20.0 flies per kg
fruit, respectively. However, as precipitation increased
from 50 mm in April to the peak of about 240 mm in
September, there was a consistent increase in relative
humidity (from 45.5 to 59.0 %) with a decrease in air
temperature (from 34.9 to 29.8ºC). This conditions
greatly favoured tephritid populations, with
infestation levels of
B. invadens
and
C. cosyra
increasing to the peak of about 186 and 210 flies per
kg fruit, respectively. However, as average
precipitation assumed its sharp drop between October
and December, there was a corresponding decrease in
relative humidity with some fluctuations in average air
temperature. During this period, tephritid numbers
dropped steadily to their lowest levels.
Figure 3 Relationship between climatic factors and infestation levels of
B. invadens
and
C. cosyra
on the 12 main host plants (pooled data)
Table 4 shows the results of the regression analysis of
counts of
B. invadens
and
C. cosyra
. Regression
between the climatic factors and infestation levels of
the fly species indicated that temperature, mean
relative humidity and rainfall all had positive
relationship (r
2
=0.58) with
B. invadens
numbers. As
described previously, these parameters increased
during the fruiting season of many host plants. At the
onset of the first effective rains in April, and with a
considerable increase in relative humidity, the
population of
B. invadens
rapidly resurged and
became widely predominant from April to July. The
first effective rain at 50 mm probably led to a very
rapid increase in the population of
B. invadens
to a
level higher than
C. cosyra
until August (Figure 3).
Moreover, the high season x mean relative humidity
interactions showed that as fly populations declined
towards the late season, the mean relative humidity
begun to decrease. Thus, temperature and rainfall had
positive relationship (r
2
= 0.60) with the upsurge of
C.
cosyra
population upsurge while relative humidity had
negative correlation (r
2
= 1.98). For both fruit fly
species, only rainfall showed positive relationship (r
2
= 0.77) with total average infestation levels (Table 4).