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Altitudinal effect and its ecological influence on population dynamics of locust, Dociostaurus maroccanus (Thunberg, 1815) in the Moroccan Middle Atlas

Authors:
© J. ent. Res., 41 (4) : 361-368 (2017)
IntroductIon
Morocco is one of the most Mediterranean
countries exposed to locust invasions, including
those of Moroccan locust Dociostaurus maroccanus,
Thunberg (1815). This species constitutes a
permanent threat to crops and pastures. The Middle
Atlas has the widest locust geographic distribution in
Morocco. Each year, over 18000 hectares of Middle
Atlas crops are sprayed with chemical pesticides in
order to control this pest (Louveaux et al., 1996).
D. maroccanus is an endemic species of Morocco
whose economic importance is very considerable.
It is among the four most harmful locusts for
agricultural and pastoral production (Bey-Bienko
and Mistchenko, 1951). It is ranked in 2nd position
after the desert locusts Schistocerca gregaria on
agricultural disasters (Arie, 1988). The Moroccan
locust belongs to the Acrididae family. It occurs within
the Mediterranean region. It is often located in dry
environments. This devastating species is strictly
linked to rocky and compact soil, diverse vegetation
and semi-arid climate. It is widely inuenced by
climatic changes. D. maroccanus is a univoltine
species. Its reproductive cycle is annual with a single
generation. The active life of this locust is about two
to four months. This life period diers according to
the biotope, especially vegetation disposal as well
as climatic conditions (Uvarov, 1977). In the Middle
Atlas, D. maroccanus occurs as larvae in early
spring. It reach the adult stage starting from the
beginning of the dry season.
Locusts are either strictly related to specic
environments, or adapted to multitude habitats. This
distribution seems to be inuenced by many factors
such as temperature, humidity, photoperiod, soil
and vegetation (Allen et al., 2006; Whitman, 2008).
Locusts are found mainly in open environments
(Uvarov, 1977) but prefer special micro- habitats for
shelter or trophic resources that may vary according
to ecological factors considered at a larger scale,
such as altitude (Boitier, 2004).
        
  Dociostaurus maroccanus     

*

Faculté des Sciences et Techniques, Université Sidi Mohamed Ben Abdellah, Laboratoire d’écologie fonctionnelle et
environnement, BP 2202 Fès, Morocco
AbstrAct
       Dociostaurus maroccanus    
               
              
     
D. maroccanus 
              
                
             
           D. maroccanus     

        
   Dociostaurus maroccanus, locust distribution, ecological index, Middle Atlas, population dynamic.
*Corresponding author's E-mail: lahelghadraoui@yahoo.fr
DOI : 10.5958/0974-4576.2017.00057.3
Journal of Entomological Research, December 2017
362
Despite the development and research progress
on locusts, both in the laboratory and in the eld,
several biological, ecological and physiological
features remain unclear. In the same sense, this
study aim the distribution, the dynamics and the
spatiotemporal progress of the Moroccan locust in
its natural environment.
  
Study stations : This study was carried out during three
successive years 2012, 2013 and 2014 in four stations
of Moroccan Middle Atlas which are chosen depending
on altitude Table 1. Sefrou is characterized by a warm
temperate climate; rainfall is higher in winter than in
summer. According to Köppen (1900) and Geiger
(1954) the climate is classied as Csa, as well as in
Mazdou and Guigou. The city of Timahdite benet
from a warm temperate climate, it is classied as Csb.
Study Method : Locust visual inspections were
conducted once a fortnight from March to October.
We counted individuals along a transect of 100 m
long and 1 m wide, separated by 10m (Ben Halima
et al., 1984; Mouhim, 1997; El Ghadraoui, 2002a,
b-2008). The covered surface was about 10000 m2
which is large enough for meaningful results (Defaut,
2010). The determination of locust species was done
according to the key of Chopard (1943) and Defaut
(2001). The prospections were conducted during three
successive years 2012, 2013 and 2014. Relative
abundance, consistency or frequency of occurrence
and density are the studied ecological indexes.
Relative abundance : Relative abundance is used for
assessing a species, a category, a class or order (ni)
to all populations of this fauna (N) in a fauna inventory
(Faurie et al., 2003). The relative abundance (RA%)
was calculated using the following formula:
RA (%) = ni × 100
N
RA% = Relative abundance.
ni = Total number of individuals of the considered species.
N = Total number of individuals of all present species.
According to the value of this relative abundance,
Faurie et al. (2003) have classied individuals as follows:
Species very abundant if AR> 75%.
Abundant if 50 <AR <75%.
Common species if 25 <AR <50%.
Rare species if 5 <AR <25%.
A very rare species if AR <5%.
Occurrence frequency : The occurrence frequency
(or constancy) is a ratio which is expressed as a
percentage of the identied number (Dajoz 1982).
Faurie et al. (2003) have defined occurrence
frequency as follows:
C (%) = Pi × 100
P
C: constancy
Pi: number of records containing the studied species
P: total number of such records
 Geo-climatic data in the four prospected stations, (Csa, Csb) Mediterranean climate.
Stations St.A (Sefrou) St.B (Mazdou) St.C (Guigou) St.D (Timahdite)
Coordinates Ed 33° 48' 26.4"N
4° 50' 1.2"W
33° 45' 17.9" N
4° 49' 46.3" W
33° 24' 43.2" N
4° 49' 18.8" W
33° 13' 14"N
5° 3' 37.4"W
Altitude (m) 800 1200 1600 1960
Slope (%) 5 15 10 5
Exposure at ground North South at ground
Annual average T (°C) 17.4 17.5 13.4 13.5
Aa Precipitations (mm) 49.7 48.9 62.8 53.7
Climate type Csa Csa Csa Csb
Ground Marlstone sandy
limestone
Sandy Sandy loam Sandy loam
Recovery rate 50% 50% 70% 70%
Dominant plant Families Asteraceae,
Poaceae, Fabaceae
and Papaveraceae
Polygonaceae,
Papaveraceae,
Asteraceae,
Lamiaceae and
Poaceae
Rutaceae, Poaceae,
Fabaceae,
Zygophyllaceae,
Thymelaeaceae and
Asteraceae
Asteraceae;
Poaceae, Fabaceae,
and Renunculaceae
Cryophyllaceae
Population dynamics of locust, Dociostaurus maroccanus
363
When the species occurs in over 50% of the
samples, it is considered constant. It is accessory
when reported as 25 to 50% of the samples. It is
accidental when its presence is mentioned in less
than 25% of the samples. When the presence of a
species is irregular, it corresponds to less than 5%.
It is then considered as exceptional.
  
Bioclimatic data : Sefrou displays an annual average
temperature of 17.4°C and 49.7 mm annual average
rainfall. July is the driest month with only 16.3 mm.
March has 84.4 mm average rainfall. It is displays the
highest rainfall rate. With an average temperature of
29°C, August is the hottest of the year. In January, the
average temperature is 7.7°C. January is therefore
the coldest month of the year.
Mazdou station has an annual average
temperature of 17.5°C. It has an average 48.9 mm
of rain per year. The driest month is July, with only
16.3 mm rainfall. An average of 103.5 mm makes of
November the mouth with the highest rainfall rate.
With an average temperature of 22.9°C, August
is the hottest month of the year. January is the
coldest month of the year with a temperature of
7.6°C. The dierence in rainfall between the driest
and wettest months is 133.9 mm. The dierence
between lowest and the highest temperature of the
year is about 23.3°C.
Guigou displays 13.4°C annual average
temperature. The annual average rainfall is 62.8 mm.
The driest month is July with only 28.2 mm rainfall
rate. March is the highest rainfall month, with an
average of 108.9 mm rainfall rate. With an average
temperature of 25.3°C, August is the hottest month
of the year. In January, the average temperature is
3°C. Therefore, January is the coldest month of the
year. The dierence between the driest month and the
wettest month is 147.6 mm rainfall rate. A variation
of 24 ± 2°C was registered during the three years.
Timahdite displays an annual average temperature
of 13.5°C. Each studied year, the rainfall had an average
of 51 ± 2 mm rainfall rate. July is the driest month of
the year (21.9 mm rainfall rate). November has the
highest rainfall rate (103.3 mm). The hottest month of
the year is July with an average temperature of 25.7°C.
In January, the average temperature is 2.4°C. January is
therefore the coldest month of the year. The dierence
of rainfall between the driest and wettest months is
128.8 mm. The dierence between the lowest and the
highest temperature of the year is 25 ± 2°C.
Dynamic and spatiotemporal distribution of the
species : We were able to locate the species in
the four studied stations, but it appears that the
individuals were very active and auent in the
high-altitude stations C and D; however, in the low
altitude stations A and B, this species was only
reported Fig. 1.
In 2012, a total number of 159 D. maroccanus
individuals is recorded in the four studied stations.
This number has tripled in 2013 with 568 individuals.
Nonetheless, the percentages of D. maroccanus
individuals have not exceeded 16.5%. During 2014,
the number of D. maroccanus individuals was less
important than 2013 (400 individuals). Still, its
percentage has exceeding 50% in the station C
Table 2.
Monthly dynamics in the four stations during the
three years : The locust population is plotted in the
ombrothermic diagram. In the station A, the species
has a high individual number rate during June for
the three studied years. This is the period when all
individuals are in the adult phase. The maximum
number have been sampled during 2013 with 25 D.
maroccanus individuals Fig. 2.
In station C, the D. maroccanus number of
individuals is higher compared to the other stations.
The number of individuals increases each year to
reach 42 individuals in 2012; 104 individuals in
 Individuals number and percentage of D. maroccanus encountered in the four stations during the three years.
Station
Year
A (Sefrou) B (Mazdou) C (Guigou) D (Timahdite)
N ni% N ni% N ni% N ni%
2012 221 23 10.4 219 9 4.1 467 74 15.8 321 53 16.5
2013 484 43 8.8 633 26 4.1 1110 254 22.8 1023 245 23.9
2014 246 22 8.9 271 29 10.7 455 240 52.5 293 109 37.2
N = total number of D. maroccanus individuals; ni = number of D. maroccanus individuals; % = percentage of D. maroccanus
individuals.
Journal of Entomological Research, December 2017
364
2013 and 130 individuals in 2014. The maximum
D. maroccanus number of individuals is reported in
May; nevertheless, this number was at its maximum
during June of 2012 and 2013 (Fig. 4).
Station D has the highest D. maroccanus
number of individuals during June 2013 with 94
individuals Fig. 5. In May 2012, D. maroccanus had
the lowest D. maroccanus number of individuals all
the way along the studied transect. the maximum D.
maroccanus number of individuals was counted in
June 2012 in the four studied stations. In July 2012,
we noticed a few individuals of D. maroccanus in
the station A; the species was absent in the station
B. simultaneously, the eective of D. maroccanus
individuals in C and D stations were very high.
Therefore, these stations could be considered
as permanent foci of D. maroccanus. In Sefrou
and Mazdou, a low D. maroccanus number of
individuals was reported. In 2012, D. maroccanus
occurrence period was very short (May, June and
July). This, could be explained by the sensibility
of D. maroccanus to climate changes, especially
precipitation and temperature. In fact, the total
disappearance of the species, at the end of July,
was probably due to the storms that took place in
the Middle Atlas from July to late September.
  Representation of D. maroccanus number of individuals at stations during the three years
  Population dynamics of D. maroccanus species during the three years in Sefrou station
Population dynamics of locust, Dociostaurus maroccanus
365
  Population dynamics of D. maroccanus species during the three years in the Mazdou station
  Population dynamics of D. maroccanus species during the three years in Guigou station
  Population dynamics of the species D. maroccanus during the three years in the Timahdite station
Journal of Entomological Research, December 2017
366
In 2013, D. maroccanus was present in the
four stations. It was only reported in the two
stations A and B while it was permanent in the
other two stations. The number of individuals was
very important during this year. The maximum D.
maroccanus number of individuals was reached in
the month of June. D. maroccanus was present up
until September and a small number of individuals
were captured in station D. We sampled a high D.
maroccanus number of individuals during June. This
might be owing to environmental conditions such
as abundant rainfall.
Average temperatures during the year 2013 gave
then a well-developed and diversied vegetation
cover. It had a positive impact on the emergence,
development and insect species richness (Essakhi et
al., 2015). In 2014, D. maroccanus has transformed
from solitary to the gregarious phase. In Guigou
station, D. maroccanus swarms invaded nearby
areas during May and early June. Fig. 5.
This transformation from solitary to gregarious
phase could be explained by climate changes.
Unsteady precipitation in winter followed by high
temperature periods have led to less developed and
less diverse vegetation cover. Food shortage has
led individuals to gather and move. Thus, population
dynamic is directly related to climatic variations that
aect resources level. Therefore, the appearance
or disappearance of individuals and their eectives
is closely related to weather conditions. Actually,
this ectothermic species is sensitive to climatic
conditions controlling its ecology, dynamics and
behavior.
Ecological indexes : Relative abundance rate
in the four studied stations and during the
three successive years from April to October
are summarized in Table 3. The number of D.
maroccanus individuals was higher in both stations
C and D during all studied years in comparison
with stations A and B. The relative abundance of
D. maroccanus is lower in both stations A and B
Fig. 6. It varies between 8 and 10% in the station A
and between 4 and 10% in station B. The species
in the two stations had a very low eective. In the
station C, the relative abundance varied every year
(15.8% in 2012, 22.8% in 2013 and 52.74% in
2014); the species was rare in 2012 and became
abundant during 2014 because 50% < RA <75%.
In addition, RA rate was 16.5% in 2012 to 37.2%
in 2014 in station D. Thereby; this species has
become so common. This can be explained by
the fact that the semi-arid microclimate with cold
winters is favoring plant cover development (Weyer
et al., 2012). The altitude in the stations C and D
ensure favorable conditions for the development,
multiplication and abundance this species. That
can be considered then as permanent stations for
the studied species.
Occurrence frequency : The occurrence frequency
rate of D. maroccanus captured between April and
October are summarized in Table 4. D. maroccanus
is constant in both C and D stations. Its occurrence
frequency rate exceeded 50% in the three years.
In A and B stations, D. maroccanus is considered
incidental because the rate of consistency, during
the years of study, vary between 27% and 50%.
  Relative abundance of D. maroccanus in the four
stations during the three years
 Relative abundance of D. maroccanus in the four studied stations.
Station A Station B Station C Station D
years niN RA% niN RA% niN RA% niN RA%
2012 23 221 10.4 9 219 4.1 74 467 15.8 53 321 16.5
2013 43 484 8.8 26 633 4.1 254 1110 22.8 245 1023 23.9
2014 22 246 8.9 29 271 10.7 240 455 52.74 109 293 37.2
ni = number of D. maroccanus individuals; N = total number of locusts; RA = Relative abundance.
Population dynamics of locust, Dociostaurus maroccanus
367
Density : The species density is given by the following
formula:
D = N
P
D: density; N: total number of individuals of collected species;
P: total number of samples taken in the considered populating
Regarding the species density, we found that D.
maroccanus individuals are denser in the station C,
Table 5. The higher densities, in the three years,
are between 6 and 20 D. maroccanus individuals.
Followed by the station D with a density of 4 to 9
D. maroccanus individuals. The remaining stations
have smaller densities that vary between 0.81 and
3.3 density rate of D. maroccanus. This can be
explained by the fact that in the stations C and
D abiotic factors (type of substrate, temperature,
precipitation, altitude, exposure and plant cover)
promote the development and propagation of
this species. On the other hand, a competitive
behavior is expressed between D. maroccanus
and other existing species in the stations. In spite
of Orthopteroid species richness, D. maroccanus
prevails owing to its persistence to unfavorable
bioclimatic conditions. Indeed, more the number of
species in a station increases, more it gathers and
more this species sets o an intense gregarious
character (El Ghadraoui et al. 2002); for station C
and D and vice versa for A and B stations, where
the number of individuals is less important.
The highest density rate of D. maroccanus was
recorded during 2013 in the stations C (19.53) and
D (18.84). In 2014, it reached its highest rate in
the station C with 20 individuals per sample. The
reason of the rise of this index may directly be
related to climatic conditions. The period before its
appearance was characterized by high rainfall in
March. Then it was immediately followed by high
temperatures. This has favored the multiplication of
the species. The results obtained in this study are
of capital importance in modeling D. maroccanus
population dynamic. This allowed us to understand
the mechanism behind the pullulating species in the
Moroccan Middle Atlas and promote D. maroccanus
control methods and limit its economic damages.
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