International Research Journal of Plant Science (ISSN: 2141-5447) Vol. 4(2) pp. 33-44, February, 2013
Available online http://www.interesjournals.org/IRJPS
Copyright © 2013 International Research Journals
Full Length Research Paper
Foraging and pollination activity of Apis mellifera
adansonii Latreille (Hymenoptera: Apidae) on flowers of
Gossypium hirsutum L. (Malvaceae) at Maroua,
Cameroon
*1,2
Dounia and 2Fernand-Nestor Tchuenguem Fohouo
1
Laboratory of Zoology, Higher Teacher Training College, University of Yaoundé I, Yaoundé, Cameroon
2
Laboratory of Zoology, Faculty of Science, University of Ngaoundéré, Ngaoundéré, Cameroon
Abstract
To evaluate the impact of Apis mellifera adansonii (Hymenoptera: Apidae) on boll and seed of
Gossypium hirsutum, its foraging and pollinating activities were studied in Maroua, during two years of
flowering (August-October 2010 and 2011). Treatments included unlimited floral access by all visitors,
bagged flowers to avoid all visits and limited visits of A. m. adansonii. Observations were made on 100
flowers per treatment. In addition, all flower visitors were recorded. The worker bee’s seasonal
rhythm of activity, its foraging behavior on flowers, its pollination efficiency, the fruiting rate,
the number of seeds per fruit and the percentage of normal seeds were recorded. Individuals
from 40 species of insects were recorded on flowers of G. hirsutum, after two years of observations.
Apis mellifera adansonii was the most frequent with 32.10% and 40.99% of visits in 2010 and 2011
respectively. This bee intensely and preferably foraged for pollen, almost throughout the day, with a
peak between 6 am and 7 am. The foraging speed was 17.56 ± 6.69 flowers per minute. The fruiting
rate, the number of seeds per fruit and the percentage of normal seeds of unprotected flowers
were significantly higher than those of flowers protected from insects. Apis mellifera adansonii
foraging resulted in a significant increase in the fruiting rate by 38% in 2010 and 33% in 2011,
as well as the number of seeds per fruit by 49.36% in 2010 and 45.42 in 2001, and the
percentage of normal seeds by 26.21 in 2010 and 23.65 in 2011. The installation of A. m. adansonii
colonies in c o t t o n p l a n t a t i o n s i s recommended to increase fruits and seeds production of
this species.
Keywords: Apis mellifera adansonii, Gossypium hirsutum, flower, pollen, pollination
INTRODUCTION
Reproduction depends on pollination (McGregor, 1976).
This is done by several agents including insects
(McGregor, 1976; Faegri and Pijl, 1979; Pesson and
Louveaux, 1984; Philippe, 1991; Tchuenguem Fohouo et
al., 2007, 2008 and 2009). In the natural environment and
in agro ecosystems, flower- feeding insects in general
and Apoidea in particular have great ecological
and economical importance because they have positive
*Corresponding author’s Email: dounia31@yahoo.fr
influence on food. production (Mutsaers, 1991;
Desquesne, 1996; Morison and al., 2000a; Tchuenguem
Fohouo et al., 2002). Effective pollination by insects can
increase fruit yield and quality of grain (Philippe, 1991;
Vaissière and Izard, 1995; Segeren et al., 1996;
Morison et al., 2000a). The lack of pollinating insects
during flowering time can lead to kidney yields fruits and /
or seeds for some crops (McGregor, 1976; Delbrassine
and Rasmont, 1988; Tchuenguem Fohouo et al., 2009).
The former cotton is perennial (Lagière, 1966;
David,1971; Ahmed et al., 1989; Philippe, 1991), but
those grown today are annual (Fryxell, 1979b, 1992;
Selanan et al., 1999; Brubaker et al., 1999a; Brubaker et
34 Int. Res. J. Plant Sci.
al., 1999b).
They are from Nord and Central America (Jakins,
2003). Cotton was domesticated by pre-Columbia people
of Yacatan peninsula (Brubaker and Wendel,1994), The
development cycle is seven months (Lagière, 1966;
David, 1971; Ahmed et al., 1989; Philippe, 1991;
Sassenrath-Cole, 1995; Wise et al., 2000). It grows on a
wide variety of soils (Jenkins, 2003) provided they are
well drained (Lagière, 1966; David, 1971). The cotton
grown in Cameroon belongs to the species Gossypium
hirsutum (Lagière, 1966; David, 1971). It is a kind of
shrub and woody with an average height of less than
1.5 m (David, 1971; Ooterhuis and Jerntedt, 1999; Ritchie
et al., 2007). This Malvaceae consists of vegetative
branches and fruiting branches called sympodes
(Lagière, 1966; David, 1971; Ooterhuis and Jerntedt,
1999; Ritchie et al., 2007). These branches carry three to
eight flowers with five petals white or yellow orange
(Lagière, 1966; David, 1971). The flower of G. hirsutum is
hermaphrodite (McGregor, 1976) with a fundamentally
system of autogamous reproduction (McGregor, 1976;
Moffett, 1983), the flowers attract insects (Green and
Jones, 1953) where susceptibility to cross-pollination by
insects is provided (Green and Jones, 1953; Oosterhuis
and Jernstedt, 1999). The fruit is a boll shaped ovoid or
spherical (Lagière, 1966; David, 1971; Philippe, 1991;
Ritchie et al., 2007) containing 29 to 40 grains (Eastick,
2002; Yasuor et al ., 2007). Fibers are a very important
raw material for the textile industry, as they are used in
the manufacture of clothing. Seeds are rich in oil and
food products such as meal looking for feed (Lagière,
1966; David, 1971; Cherry and Lefflter, 1984; Philippe
1991). World production in total is more than 24.5
million tons of which 40% is produced by the USA.
Cameroon is the 3rd African Cotton producer with more
than 240 000 tons of seed cotton; in this country, demand
for cotton seed is estimated at over 250 000 tons
(MINADER, 2010).
The floral entomofauna of G. hirsutum is not very
well studied. The few studies from the literature are out of
Cameroon, particularly in Sudan (Ahmed et al., 1989),
Russia (McGregor, 1976), Australia (Thomson, 1966;
Mungomery and Glassop 1969; Richards et al., 2005)
and USA (McGregor, 1976; Umbeck et al., 1987; Van
Deynze et al., 2005; Llewellyn et al., 2007). However,
according to Roubik (2000), Tchuenguem (2005) and
Gallai et al., (2009), floral entomofauna of a plant species
can vary from one region to another. This work
was conducted to study the activity of A. m. adansonii
on the flowers of
G. hirsutum to assess
the effectiveness of bee pollination on yields of this
Malvaceae in Maroua. A preliminary study on the
relationship insect-flowers in Maroua before 2010
(unpublished
data) showed that A. m. adansonii
intensely visit the flowers of G. hirsutum.
MATERIALS AND METHODS
Site and biological materials
The studies were conducted from August to October in
2010 and 2011 respectively in the locality of Mayel-Ibbé
(Latitude 10 °62 'N, Longitude 14 °33' E and altitude 400
m), Far North Region of Cameroon.
This R egion
belongs to
the
ecological
zone
with
three
phytogeographical areas (Sahel-Sudanian, Sahelian and
Sudanian altitude) periodically flooded, with unimodal
rainfall
(Letouzey 1985). It has a Sahel-Sudanian
climate type, characterized by two annual seasons: a
long dry season (November to May) and a short rainy
season (June to October); August is the wettest month of
the year (Kuete et al., 1993). Annual rainfall varies from
400 to 1100 mm (Kuete et al., 1993). The annual average
temperature varies between 29 and 38°C and a daily
temperature range between 6 and 7°
C (Kuete et
al.,1993). The experimental plot is an area of 440 m 2.
The animal material was represented by insects
naturally present in the environment and a colony of Apis
mellifera adansonii Latreilles (Hymenoptera: Apidae),
housed in a tree located 900 m from the experimental
plot. Vegetation was represented by wild species and
cultivated plants. The plant material was represented
by the seeds of G. hirsutum provided by SODECOTON.
Planting and maintenance of culture
On May 31st, 2010 and 2011, the experimental plots
(that have been previously plowed) was divided into six
sub - plots of 6.5 x 5 m2 each, with a row of two
meters between the left and subplots. This field
received seedlings of 6 lines per sub - plot. The seeds
were sown in holes at the rate of 10 grains per hole. The
spacing was 25 cm bet ween rows and 80 cm on rows;
a hole was 4 cm depth (Lagière, 1966; David, 1971;
Cotton Australia, 2002; MINADER, 2010). Two weeks
after germination (occurred July 17, 2010 and July 24,
2011), the plants were thinned leaving the stronger.
Thinning of the opening of the first flower, which occurred
August 6, 2010 and August 16, 2011, weeding was done
with a hoe every three weeks. Manual weeding was
performed regularly at the beginning of flowering until
harvest, which ended November 28, 2010 for the first
growing season and December 05, 2011 for the second
growing season.
Determining the mode of reproduction
On September 02, 2010, 200 flowers of G. hirsutum
the bud stage were labeled; of these, 100 were left
Dounia and Fohouo 35
Figure 1. Plant Gossypium hirsutum
showing a flower isolated from insects.
unattended (Treatment 1) and 100 were bagged
(treatment 2) to prevent visitors (Figure 1). On
September 07, 2011, 200 flowers of G. hirsutum at bud
stage were labeled; of these, 100 were left unattended
(Treatment 3) and 100 were bagged (treatment 4) to
prevent visitors. For each year, ten days after the wilting
of the last flower, the number of boll formed in each
treatment was counted. For each treatment, the fruiting
index (Ifr) was calculated using the following formula: Ifr
= ( F1/F2 ), where F1 is the number of boll formed and
the number of flowers F2 initially labeled (Tchuenguem
et al., 2004). The out crossing rate (TC) was calculated
using the formula: TC={[(IfrX - IfrY/IfrX]x100},
Where IfrX and IfrY are mean fruiting indexes of
free treatment and bagged treatment respectively
(Demarly, 1977). The rate of self-pollination in the broad
sense (TA) was calculated using the formula:
TA = (100 - TC).
Study of the activity of insects on the flowers of G.
Hirsutum
Observations were made every two days, on f l owers
of t reatment s 1 and 3, according to six slots: 7-8 h,
9-10 h, 11-12 h, 13-14 h, 15-16 h and 17-18 h.
September 3 to 23, 2010 and from September 7 to 27,
2011, the blooming periods labeled flower buds. Insects
found on flowers were counted at each daily time frame.
Data obtained were used to determine the frequency (Fx)
of visits A. m. adansonii on flowers of G. hirsutum.
For each year of study, Fx = [(Vx / Vi) x 100], where
Vx is the number of visits to A. m. adansonii on flowers of
free treatment and Vi the total number of insect visits on
flowers of the same treatment.
The floral products (nectar and / or pollen) collected
by the bee were recorded for the same dates and time
slots as that of insect counts. The study of this parameter
indicates whether A. m. adansonii is strictly pollinivorous,
or nectarivore, or pollinivorous and nectarivore. This
can give an idea on its involvement in the pollination of
this plant. The duration of visits and foraging speed
(number of flowers visited per minute) (Tchuenguem et
al., 2004) were timed at the same dates and in six time
slots. Abundances (larger numbers of individuals
simultaneously active) per flower and per 1000
flowers 1000 (A1000) were recorded on the same dates
and time slots as the registration of the duration of visits.
The first parameter was recorded as a result of direct
counts. For A1000, A. m. adansonii were counted on a
known number of open flowers; A1000 was then
calculated by the formula: A1000 = [(Ax / Fx) x 1000],
where Fx and Ax are respectively the number of flowers
and the number of A. m. adansonii effectively counted on
these flowers at time x (Tchuenguem et al., 2004).
The influence of the surrounding flora was assessed
by direct observation: the number of times the bee went
from G. hirsutum flowers to another plant species and
vice versa was noted throughout the period of
investigation.
Measuring the temperature and humidity of the
experimental site
During the days of investigation, the temperature and
humidity of the study site were recorded every 30 min, 7-18 h, using a thermo hygrometer installed in the shade.
Evaluation of the impact of flower-feeding insects on
the yield of G. hirsutum
At boll maturity, harvesting was done in all treatments.
For each year of study, the digital input (Pf) of insects on
fruiting is Pf = {[(fx-fy) / fx] x 100}, where fx and fy are the
36 Int. Res. J. Plant Sci.
fruiting rate in treatments x (treatments 1 or 3) and
y (treatments 2 or 4). For a treatment, the f r u i t i n g
rate (Tfr) is Tfr = [(number of boll / number of flowers) x
100]. The digital input (Pf) of insects (Pg) on the number
of seeds is Pg = {[(gx-gy) / gx]} x 100 where gx and gy
are the mean number of seeds per pod in treatments x
and y. The digital input (Pgn) of insects on normal
seeds is Pgn = {[(gnx-gny) / gnx]} x 100 where gnx and
gny are the percentages of normal seed in treatments x
and y.
Measuring the effectiveness of pollination by A. m.
adansonii on G. hirsutum
Along with the development of treatments 1 and 2, 100
flowers were isolated (treatment 5) as those of treatment
2. Along with the development of treatments 3 and 4,
100 flowers were isolated (treatment 6) as those of
treatment 4. Between 7- 9 am, the gauze bag was
gently removed from each newly bloomed flower and
t h e f l o we r observed for up to twenty minutes. Flowers
visited by A. m. adansonii were marked and unattended
flowers were eliminated. After this manipulation, the
flowers were protected once more.
At boll maturity, harvesting was done in treatments 5
and 6. For each year of study, the digital input (Pfx) of A.
m. adansonii on fruiting is Pfx = {[(fz-fy) / fz] × 100},
where fz and fy are the fruiting rate in treatment z
(protected flowers and visited exclusively by A. m.
adansonii) and y (protected flowers) (Tchuenguem et al.,
2004). The digital input (PGX) of A. m. adansonii in the
the number of seeds is PGX = {[(gz-gy) / gz]} x 100
where gz and gy are the average number of seeds per
boll in treatments z and y (Tchuenguem et al., 2004). The
digital input (PGNX) of A. m. adansonii on normal seeds
formation is PGNX = {[(GNZ-gny) / GNZ]} x 100 where
gnz and gny are the percentages of normal seeds
in treatments z and y (Tchuenguem et al., 2004).
Data analysis
SPSS software and Microsoft Excel were used for three
tests: Student's (t) for comparison of means, correlation
coefficient (r) for the study of linear relationship between
two variables, Chi-square (χ2) for the comparison of
percentages.
autogamy rate was 68.13%. In 2011, the corresponding
figures were 28.72 and 71.28%.
It appears that G. hirsutum has a mixed mating
system, autogamous-allogamous, with the predominance
of allogamy.
Activity of A. m. adansonii on the flowers of G.
hirsutum
Seasonal frequency of visits
For 21 and 23 days of the flowering periods in 2010
and 2011, 587 and 644 visits of 38 and 36 species of
insects were counted on 100 and 100 flowers of G.
hirsutum respectively in 2010 and 2011. A. m.
adansonii comes with 183 and 264 visits spread
over all periods of flowering, t h a t is 31.17% and
40.99% of all visits recorded in 2010 and 2011
respectively; this bee species ranked first in whatever
year of investigation (Table 1). The difference between
these two percentages is highly significant (χ2 = 12.80
[df = 1, P<0.001]). This insect has been active on the
flowers of G.hirsutum from 6 am to 17 pm, with a peak
of visits between 6 am and 7 am in 2010 as well as in
2011 (Figure 2).
Abundance of bees
In 2010, the highest average number of A. m. adansonii
simultaneously active was one bee per flower (n = 50, s =
0) and 450.66 per 1000 flowers (n = 35 s = 326.7, max =
1200). In 2011, the corresponding figures were 1 per
flower (n = 50, s = 0) and 514.10 per 1000 flowers (n =
35, s = 378.11, max = 1625). The difference between the
average number of bees per 1000 flowers in 2010 and
2011 is highly significant (t = - 3.09 [df = 68, P <0.01]).
The flowers of G. hirsutum are visited by other
Apidae (Allodape sp. 1, Amegilla sp. 1, Amegilla sp. 2,
Thyrus sp., Xylocopa sp. 1, Xylocopa sp. 2), Halictidae
(Lipotriches
collaris,
Macronomia
vulpina)
and
Megachilidae (Chalicodoma sp.1, Chalicodoma sp. 2,
Creightonella sp. Megachile sp. 1, Megachile sp. 2,
Megachile sp. 3) to collect pollen. Other insects such as
Eumenidae (Delta sp.), Calliphoridae and Stratiomyiidae
(Hermetia 1 sp. and 2 sp.) eat
pollen on
flowers.
Predators of Apidae, Halictidae and Megachilidae are
Sphecidae (Philanthus triangulum), Nevroptera
and
Mantodea.
RESULTS
Floral substances taken
Reproductive system
The mean f ruiting indexes were 0.91, 0.62, 0.94
and 0.67 in treatments 1, 2, 3 and 4 respectively.
Thus in 2010, the allogamy rate was 31.87% and the
During each period of flowering of G. hirsutum, A. m.
adansonii harvest preferably and regularly pollen (Figure
3). The exclusive collection of nectar (Figure 4) and
Dounia and Fohouo 37
Table 1. Diversity of floral insects on G. hirsutum flowers in 2010 and 2011, number and
percentage of visits of different insects
Insects
2010
Order
Family
Hymenoptera Apidae
Formicidae
Halictidae
Megachilidae
Sphecidae
Vespidae
Diptera
Eumenidae
Calliphoridae
Coleoptera
Stratiomyiidae
Syrphidae
Scarabeidae
Hemiptera
Lepidoptera
Meloidae
Coreidae
Pyrrhocoridae
Acraeidae
Nymphalidae
Pieridae
Pieridae
Pieridae
Orthroptera
Dythioptera
Nevroptera
Total
Mantodae
Genus,
species,
subspecies
NP
Apis mellifera adansonii
P
Allodape sp.
Amegilla sp. 1 P
P
Amegilla sp. 2
P
Thyrus sp.
P
Xylocopa sp. 1
Xylocopa sp. 2 P
P
Polyrachis sp. 1
P
Lipotriches collaris
Macronomia vulpinaP
Chalicodoma sp.1 P
Chalicodoma sp.2 P
P
Creightonella sp.
P
Megachile sp. 1
Megachile sp. 2 P
Megachile sp. 3 P
Philanthus triangulumPr
(1sp.) Pr
Synagris cornutaN
(1sp.) N
Delta sp. N
(1sp) P
(2sp) P
Hermetia sp. P
(1sp.) P
(1sp) P
(2sp) P
Coryna sp. P
Anoplocnemis curvipesP
Dysdercus voelkeriP
Acraea acerataN
(1sp.) N
Catopsilia florellaN
(1sp) N
( 2sp) N
(1sp.) p
(2sp.) p
(sp) Pr
(1sp)Pr
(2sp) Pr
40 species
n1
183
18
15
7
7
35
17
13
37
44
11
2
1
3
6
7
9
1
3
4
1
13
9
3
4
34
7
2
12
7
33
12
8
2
2
6
4
0
5
0
587
p1%
31.2
3.07
2.56
119
1.19
5.96
2.9
2.21
6.3
7.5
1.87
0.34
0.17
0.51
1.02
1.19
1.53
0.17
0.51
0.68
0.17
2.21
1.53
0.51
0.68
5.79
1.19
0.34
2.04
1.19
5.62
2.04
1.36
0.34
0.34
1.02
0.68
0
0.85
0
100
2011
n2
264
7
11
27
1
31
2
26
31
42
7
0
0
1
2
0
4
0
5
1
3
8
3
1
1
41
4
1
9
6
52
3
11
3
7
9
13
2
3
2
644
p2%
40.99
1.09
1.71
4.19
0.16
4.81
0.31
4.04
4.81
6.52
1.09
0.00
0.00
0.16
0.31
0.00
0.62
0.00
0.78
0.16
0.47
1.24
0.47
0.16
0.16
6.37
0.62
0.16
1.40
0.93
8.07
0.47
1.71
0.47
1.09
1.40
2.02
0.31
0.47
0.31
100
Comparison of percentages of Apis mellifera adansonii visits for two years: χ2 = 18.80 ([ddl = 1; P <
0.001]).
n1: number of visits on 100 flowers in 10 days.
n2: number of visits on 100 flowers in 10 days.
p1 and p2: percentages of visits.
p1 = (n1 / 587) x 100.
p2= (n2 / 644) x 100.
NP: Visitor collected nectar and pollen.
N: Visitor collected nectar.
P: Visitor collected pollen.
Pr: Predation.
1 sp.: Undetermined species.
38 Int. Res. J. Plant Sci.
Figure 2. Distribution of visits A. m. adansonii on the flowers of G. hirsutum according to
daily time frames in 2010 and 2011.
Figure 3. A. m. adansonii collecting
pollen in a flower of G. hirsutum
Figure 4. A. m. adansonii collecting nectar in
a of G. hirsutum
simultaneous harvest of nectar and pollen during a
foraging trip were less frequent (Table 2).
Rate of visits according to the flowering stages
Overall, visits of A. m. adansonii were more numerous on
treatments 1 and 3 when the number of open flowers
was highest (Figures 5). The correlation between the
number of visits of A. m. adansonii and the number of
opened flowers was positive and highly significant in
2010 (r = 0.80 [df = 8, P <0.05]) as well as in 2011 (r =
0.72 [df = 8, P < 0.05]).
Dounia and Fohouo 39
Table 2. Products harvested by A. m. adansonii on flowers of G. hirsutum in 2010 and 2011.
year
Number of
visits studies
Visits for pollen
harvest
Visits for nectar
harvest
Visits for pollen and nectar
harvest
Number
%
Number
%
Number
%
2010
183
115
62.84
32
17.48
36
19.67
2011
264
197
74.62
67
25.37
0
0
Figure 5. Variation of number of flowers and number of visits of A. m. adansonii, on the
flowers of G. hirsutum in 2010 and 2011.
Duration of visits per flower
The average duration of a visit of A. m. adansonii per
flower of G. hirsutum varied significantly depending on
the substance taken. In 2010, the average duration of a
visit for pollen collection was 4.84 sec (n = 107, s = 1.53,
max = 8); for the collection of nectar, it was 1.78 sec (n =
32, s = 0.7, max = 3). In 2011, the corresponding
results were 5.32 sec (n = 197, s = 2.93, max = 15) and
3.37 sec (n = 67, s = 2.03, max = 9) for pollen and
nectar harvest respectively. The difference between
the two mean durations is highly significant in 2010 (t
= 53.68 [df = 137, P <0.001]) as well as in 2011 (t =
37.50 [df = 262, P<0.001]).
The difference between the duration of the visit to
harvest nectar in 2010 and 2011 is highly significant (t =
- 20.12 [df = 97, P<0.001). Also, the difference between
the duration of visit for pollen in 2010 and 2011 is
highly significant (t = - 13.33 [df = 302, P <0.001]).
Foraging speed of A. m. adansonii on the flowers of
G. hirsutum
On the plot of G. hirsutum, A. m. adansonii visited 4-24
flowers / min in 2010 and 3 to 20 flowers / min in 2011.
The average speed is 17.54 foraging flowers / min (n =
80, s = 6.69) in 2010 and 13.08 flowers / min (n = 80, s =
6.39) in 2009. The difference between these two means
is highly significant (t = 27.87 [df = 158, P < 0.001]).
Influence of wildlife
Workers of A. m. adansonii are disturbed in their
foraging by other workers or other arthropods which are
either predators or c om p e t i t o r s f or t h e se a rc h of
p o l l e n or nectar.
These disturbances have resulted in the interruption
of certain visits. In 2010, for 183 visits of A. m. adansonii
7 (3.82%) were interrupted by the same worker bees
and in 2011, for 264 visits o f A. m. adansonii, 11
(4.16%) were interrupted by the same worker bees. For
their load of pollen foragers who suffered such
disturbances are forced to visit more flowers and / or
plants during the corresponding foraging trip. In pollen
foragers, these disturbances resulted in partial loss of
carried pollen.
During the study period, other plant species located
near the experimental field of cotton were also visited by
A. m. adansonii for nectar (N) and / or pollen (P). Among
these
plants,
there
were:
Arachis
hypogaea
(Papilionaceae, P), Mitracarpus villosus (Rubiaceae, N
and P) Jathropha gossipiifolia (Euphorbiaceae, N), Striga
40 Int. Res. J. Plant Sci.
Table 3. Daily distribution of A. m. adansonii visits on 100 G. hirsutum flowers over 10 days of observation in 2010 and 2011
respectively, mean temperature and mean humidity of the study site
Daily period (hours)
10-11
12-13
year
Parameter registered
6-7
8-9
2010
Number of visits
o
Temperature ( C)
Hygrometry (%)
61
29.12
72.4
43
31.95
63.8
26
34.5
59.2
2011
Number of visits
o
Temperature ( C)
Hygrometry (%)
103
27.2
71.8
77
31.4
63.8
56
34.06
59.79
14-15
16-17
9
37.54
52.4
12
36.14
46.9
26
34.52
48.8
9
37.21
52.9
7
35.9
47.2
12
34.34
49.11
2010: for temperature and hygrometry, each figure represents the mean of 50 observations.
2011: for temperature and hygrometry, each figure represents the mean of 50 observations.
Figure 6. Mean daily temperature and humidity and mean number of visits of A.
m. adansonii on the flowers of G. hirsutum in 2010 and 2011.
hermonthica (Scrophulariaceae, N), Hibiscus asper
(Malvaceae, N and P), Sesamum indicum (Pedaliaceae,
N), Sorghum bicolor (Poaceae, P). During A. m.
adansonii foraging trips of 2010, on 183 visits, only 13
(7.10%) were made by individuals from any of these
plants. In 2011, the corresponding values were 264
visits, 24 (9.09%).
correlation was negative and significant between the
number of visits of A. m. adansonii on the flowers of G.
hirsutum and temperature in 2010 (r = -0.78 [df = 4, P
<0.05]) and 2011 (r = -0.77 [df = 4, P <0.05]). The
correlation between the number of visits and the relative
humidity of the air was positive and significant in 2010
(r = 0.71 [df = 4, P <0.05]) and 2011 (r = 0.87 [df = 4, P
<0.05]) (figure 6).
Daily rate of visits
Beekeeping value of G. hirsutum
A. m. Adansonii has been active on the flowers of G.
hirsutum from 6 am to 18 am, with a peak of visits
between 6 and 7 am in 2010 and 2011.
Strong winds disrupted visits A. m. adansonii on the
flowers of G. hirsutum. Thus, of the 183 and 264 visits
recorded in 2010 and 2011 respectively, 7 (3.82%) and 11
(4.14%) were interrupted by such winds. Climatic factors
have influenced the activity of A. m. adansonii on the
flowers of G. hirsutum in field conditions (Table 3). The
During the rainy season in Maroua, we noted an activity
developed in workers of A. m. adansonii on G. hirsutum
flowers. In particular, there was a very good harvest of
pollen, a low harvest of nectar and fidelity to flowers of
G. hirsutum. These data highlight the high attractiveness
of pollen of this Malvaceae vis-à-vis A. m. adansonii.
They allow the classification of G. hirsutum as a highly
polliniferous and slightly nectariferous bee plant.
Dounia and Fohouo 41
Table 4. G. hirsutum yields under pollination treatments.
Seeds / boll
Treatment
Unlimited visits
Bagged flowers
Unlimited visits
Bagged flowers
A. m. adansonii
A. m. adansonii
year
2010
2010
2011
2011
2010
2011
Flowers
100
100
100
100
30
30
boll
91
62
94
67
30
30
Fruiting
rate
91.00
62.00
94.00
67.00
100
100
Impact of flower-feeding insects in pollination and
yields of G. hirsutum
During pollen and/or nectar harvest, flower-feeding
insects of G. hirsutum are in regular contact with the
anthers and stigma (Figure 3). These flower-feeding
insects therefore increase the possibilities of this
Malvaceae pollination. Table 4 presents the results on
fruiting rate, number of seeds per pod and percentage of
normal seeds in different treatments. It is clear from
this table that:
a)
Comparison of rates of fruiting shows that the
differences are highly significant between treatments 1
and 2 (χ2 = 23.39 [df = 1, P <0.001]), treatments 3 and 4
(χ2 = 23.22 [df = 1, P <0.001]) and not significant
between treatments 1 and 3 (χ2 = 0.65 [df = 1, P> 0.05]).
Therefore, in 2010 and 2011, the fruiting rate of flowers
from open pollination (treatment 1 and 3) was higher than
that for protected flowers (treatments 2 and 4). In 2010
and 2011, the percentage of fruiting rate due to the action
of the flower-feeding insects was 31.86% and 28.72%
respectively. For t h e two years of investigations, the
rate of boll due to the influence of the flower-feeding
insects including A. m. adansonii is 30.29%;
b)
Comparison of the average number of seeds
per capsule showed a highly significant difference
between the treatments 1 and 2 (t = 43.51 [(df = 151,
P<0.001]) treatments 3 and 4 (t = 43.24 [(df = 1159,
P<0.001]), and treatments 1 and 3 (t = 7.6 [(df = 183,
P <0.001]). Consequently, in 2010 and 2011, the
number of seeds boll for open pollinated flowers
(treatments 1 and 3) was higher than that for protected
flowers (treatments 2 and 4). The percentages of the
number of seeds per capsule due to the action of insects
including A. m. adansonii were 43.29 and 38.37%
respectively in 2010 and 2011. F or b oth years of
study, this percentage is 40.83%;
c)
Comparison of the percentages of normal
seeds showed highly significant difference between
treatments 1 and 2 (χ2 = 392.10 [df = 1, P <0.001]),
treatments 3 and 4 (χ2 = 310.75 [df = 1, P <0.001]) and
non significant difference between treatments 1 and 3
(χ2 = 0.82 [(df = 1, P> 0.05]). Consequently, in 2010 and
Mean
31.16
17.67
32.68
20.14
34.9
36.9
sd
10.43
14.39
9.68
15.09
2.35
3.78
Total
Seeds
3116
1767
3268
2014
1087
1107
Normal
Seeds
2878
1229
2959
1450
987
1044
%
normal
seeds.
92.36
69.55
90.54
71.99
94.26
94.3
2011, the percentage of normal seeds of flowers from
open pollination (treatment 1 and 3) was higher than
that for protected flowers (treatments 2 and 4).
For 2010 and 2011, the percentages of normal seeds
due to the action of insects including A. m. adansonii
were 24.69 and 20.48% respectively. For two cumulative
years, this percentage is 22.58%.
Pollination efficiency of A. m. adansonii on G.
hirsutum
From Table 4, it appears that:
a)
Comparison of f r u i t i n g rates shows a highly
significant difference between treatments 2 and 5 (χ2 =
21.67 [df = 1, P <0.05]) and treatments 4 and 6 (χ2 =
24.74 [df = 1, P <0.05]). Therefore, the rate of fruit se t
o f flowers isolated and visited exclusively by A. m.
adansonii (treatments 5 and 6) is higher than that of
protected flowers (treatments 2 and 4). In 2010 and 2011,
the percentagees of fruiting rate due to the efficiency of
pollinating A. m. adansonii were 38.00 and 33.00%
respectively. For the two years of experiments, the
percentage is 35.5%;
b)
Comparison of the average number of seeds per
boll shows a highly significant difference between
treatments 2 and 5 (t = - 2.93 [(df = 90, P <0.01]) and
treatments 4 and 6 (t = - 32.93 [(df = 95, P <0.001]).
Consequently, in 2010 and 2011, the number of seeds
per boll of flowers isolated and visited exclusively by A.
m. adansonii (treatments 5 and 6) was higher than that of
protected flowers (treatments 2 and 4). Percentages of
the number of seeds per boll due to the pollination
efficiency of A. m. adansonii were 49.36 and 45.42%
in 201O and 2011 respectively. For the two seasons of
study, this percentage is 47.39%;
c)
Comparison of the percentage of normal seeds
showed a highly significant difference between
treatments 2 and 5 (χ2 = 245.50 [df = 1, P <0.001]) and
treatments 4 and 6 (χ2 = 221.54 [df = 1, P <0.001]).
Therefore, in 2010 and 2011, the percentage of normal
seeds from flowers isolated and visited exclusively by A.
m. adansonii (treatments 5 and 6) was higher than that
42 Int. Res. J. Plant Sci.
protected flowers (treatments 2 and 4). The percentages
of normal seeds due to pollination efficiency of A. m.
adansonii were 26.21 and 23.65% in 2010 and 2011
respectively. For the two years of experimentation,
this
percentage
was
24.93%.
In summary, the influence of A. m. adansonii on boll
and grain yields was positive. A positive and significant
correlation has been found between the number of
seeds and the number of visits of A. m. adansonii in 2010
(r = 0.82 [df = 37, P <0.05]) and in 2011 (r = 0.72 [df = 31,
P <0.05]).
DISCUSSION
A. mellifera workers were the main floral visitor of G.
hirsutum during the observation periods.T these bees
are known as insects visiting the flowers of G. hirsutum
in West
Africa (Ahmed
et
al, 1989), Australia
(Thomson, 1966; Mungomery and Glossop, 1969), India
and Russia (McGregor, 1976). The significant difference
between the percentages of A. m. adansonii visits of
studied years could be attributed to the experimental
site variation in 2010 and 2011. It is known that the
anthophilous insect fauna of a plant varies over time
(Moffett et al., 1975; Elfawal et al., 1976; Moffet et al.,
1976; Tchuenguem Fohouo, 2005). The peak of A. m.
adansonii activity on the flowers of was in the morning,
which corresponds to the period of the high availability
of pollen on flowers of G. hisutum. Furthermore, this
pollen is produced in large quantities, up to 20,000
pollen grains per flower (Ter Avanesian, 1978) and is
easily accessible to insects (Green and Jones, 1953;
McGregor, 1976; Oosterhuis and Jonestedt, 1999) the
opened flower has a large diameter (5-9 cm) (Ter
Avanesian, 1978; Maffett, 1983),
The decreased of the activity between 11 am and
13.pm could be related to the increase of the temperature
in the experimental field. Although, foragers preferred
warm or sunny days for good floral activity (Kasper et
al., 2008), some high temperature negatively affect
insect activity on foraged flowers. Similarly, rainfall has
been documented as an environmental factor that can
disrupt the floral insect activity (McGregor, 1976).
The abundance of A. m. adansonii foragers on 1000
flowers and the positive and highly significant correlation
between the number of G. hirsutum flowers in bloom and
the number of A. m. adansonii visits indicates the
attractiveness of G. hirsutum pollen with respect to this
bee. In fact, weather conditions during bloom were
demonstrated to affect the abundance and foraging of
pollinator insects (Bramel et al., 2004; Julianna and
Rufus, 2010).
The significant difference between the duration of
visits in 2010 and 2011 could be attributed to the
availability of floral products or the variation of diversity of
flowering insects from one year to another. During each
of the two flowering periods of G. hirsutum, A. m.
adansonii intensely and regularly harvested pollen. This
could be attributed to the needs of individuals or bee
colonies during the flowering period. The disruptions of
visits by other insects reduced the duration of certain A.
m. adansonii visits. This obliged some bees to visit
more flowers during a foraging trip in order to maximize
their pollen loads. Similar observations were made for A.
mellifera adansonii workers foraging on flowers of Entada
africana (Fabaceae) flowers, P. guajava (Myrtaceae) f
(Tchuenguem et al., 2007), Croton macrostachyus
(Euphorbiaceae), Syzygium guineense var. guineense
(Myrtaceae) (Tchuenguem et al., 2008a), Persea
americana (Lauraceae), Vitellaria paradoxa (Sapotaceae)
(Tchuenguem et al., 2008b), V. unguiculata (L.)
(Fabaceae) (Tchuenguem et al., 2009b), Combretum
nigricans, Erythrina sigmoidea, Lannea kerstingii,
Vernonia amygdalina (Tchuenguem et al., 2010) and for
Chalicodoma cincta cincta (Hymenoptera: Megachilidae)
foraging on flowers of Cajanus cajan (Fabaceae) (Pando
et al., 2011b), Xylocopa olivacea workers foraging
P. vulgaris flowers (Kingha et al., 2012) and Xylocopa
calens foraging on flowers of P. coccineus (Pando et al.,
2011a).
The h o n e y bee foragers had a high affinity with
respect to G. hirsutum when compared to the neighboring
plant species, indicating their faithfulness to this
Malvaceae, a phenomenon
known
as
“floral
constancy” (Louveaux,1984; Backhaus, 1993; Basualdo
et al., 2000). Flower constancy is an important aspect in
the management of pollination. For this research, it
indicates that A. m. adansonii can provide benefits to
pollination management of G. hirsutum.
During the collection of pollen on each flower, A. m.
adansonii foragers regularly come into contact with the
stigma. They were also able to carry pollen with their
hairs, legs and mouth accessories from a flower of one
plant to stigma of another flower of the same plant
(geitonogamy), to the same flower (autogamy) or to that
of another plant (xenogamy). The workers can thus
influence self- pollination and cross-pollination (Moffett et
al., 1975; Rao et al., 1969).
The significant contribution of A. m. adansonii in boll
and seed yields of G. hirsutum is in agreement with
similar findings in Australia (Llewellyn et al., 2007)
and United State of America (Vam Deynze et al., 2005).
This Higher productivity of boll and seeds in
unlimited visits when compared with bagged flowers
showed that insect visits were effective in increasing
cross-pollination. Our results confirmed those of
Llewellyn et al. (2007), Vam Deynze et al. (2005) and
Xanthopulos and Kechagia (2005) who revealed that G.
hirsutum flowers set little pods in the absence of insect
pollinators. Similar experiments in England (Free, 1966)
and in Brazil (Free, 1993) have shown that pollination by
insects was not always needed.
Thus, pollination
requirements may different between regions.
Dounia and Fohouo 43
CONCLUSION
This study reveals that G. hirsutum outlets studied is a
highly polliniferous bee plant that obtained benefits from
the pollination by insects among which A. m. adansonii is
of great importance. The comparison of boll and seeds
set of unprotected flowers with that of flowers visited
exclusively by A. m. adansonii underscores the value of
this bee in increasing boll and seed yields as well as
seed quality. The installation of A. m. adansonii hive at
the proximity of G. hirsutum fields should be
recommended for the increase of boll and seed yields of
this valuable crop, and to improve pollen production as a
hive product.
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