ABSTRACT
The study was conducted to investigate the effect of seasonal changes on distribution and abundance of insects in three habitat types in Umudike Area, of Abia State, Nigeria. The specific objectives were to: to investigate the seasonal changes in insect diversity of three habitat types in Umudike Area, Abia State, to compare the abundance of selected key insect species during the wet and dry seasons in three habitat types, to determine the status and distribution of different insect groups in the study sites, to generate baseline data for kick-starting long-term monitoring of the insect’s life of the area. Insects sample were collected weekly from each sampling sites using locally made sweep net, picking was done with hands or forceps. Data were collected for five months with two months wet season (June and July) two months dry season (November and December) and period one month as transition (April) 2018. The results obtained were presented using descriptive statistics such as graphs, tables and chats. A total of 1264 insects spread across nine (9) orders, twenty-eight (28) families and forty-three (43) species were recorded. The different insects sampled, were higher during the wet season as compared to the dry season. Although insect species were significantly most abundant in the Fish farm site followed by the Experimental farm site. Relict forest had the least abundance. Shannon diversity index suggested that insect diversity was highest in Relict forest during the wet season. Species evenness based on the pielou’s index suggested high spread of the species across the habitat types and seasons. In Relict forest, the most abundant insects order is Hymenoptera. Meanwhile, Odonata (damselflies and dragonflies) were most abundant in Fish farm site. While Orthoptera were most abundant in Experimental farm site. In all the three habitat types sampled Orthoptera were most abundant insects order. Meanwhile among the insect families recorded Acrididae was most abundant. Insect species were most abundant at the relative humidity between 93 –97% and at temperature of 27 but least at relative humidity between 88 – 92% and at temperature of 29˚C. Comparing species composition among the surveyed habitat types revealed that insect species assemblages were very similar between the wet and dry seasons in Relict forest and the Fish farm site. The study concluded that there were high spreads of insect species across the surveyed habitats. The study recommended that routine insect abundance and diversity monitoring should be encouraged.
TABLE OF CONTENTS
Title page i
Declaration
ii
Certification iii
Dedication iv
Acknowledgements ix
List of Tables x
List of figures xi
List of plates xi
List of Appendices xi
Abstract xii
CHAPTER 1: INTRODUCTION
1.1 Background
of the study 1
1.2 Statement
of the problem 3
1.3 Objectives
of the study 4
1.4 Scope of the study 5
1.5 Justification
of the study 5
CHAPTER 2: LITERATURE REVIEW
2.1
Insect abundance 6
2.2 Economic importance of insects 8
2.3 The Behaviors’ of an insects 10
2.3.1
The food of insects 11
2.3.2
Communication in insects 12
2.4 Diversity of insects in tropical rainforest 13
2.4.1
Threats to tropical rainforest 14
2.4.2
Restoration of tropical rainforest and its insect communities 15
2.4.3
Responses of insects to agricultural activities 16
2.4.4
Responses of insects to logging 17
2.5 Nigeria forest 19
2.6 Impact of different parameters of climate on
insects 20
2.6.1
Temperature 20
2.6.2 Rainfall 21
2.6.3
Relative humidity 22
2.7 Insect as pollinators 22
2.8 Insect as an ecosystem bio – indicators 24
2.9
Insects conservation 25
2.10
Insect taxonomic challenges 26
2.11
The orders of insects 28
2.11.1
Orthorptera 28
2.11.2
Hemiptera or true bug 28
2.11.3
Hymenoptera 29
2.11.4
Lepidoptera 29
2.11.5
Odonata 30
2.11.6
Earwings 30
2.11.7
Collembola 31
2.11.8
Ephemeroptera 31
2.11.9
Mallophaga 31
2.11.10
Anoplura 32
2.11.11
Thysanoptera 32
2.11.12
Neuraptera 32
2.11.1 Siphonaptera 32
2.11.14 Psocoptera 33
2.11.15
Diptera 33
2.11.16
Dityoptera 33
2.12. Aerial insects 34
CHAPTER 3:
MATERIALS AND METHODS
3.1
Description of the study area 35
3.2
Sampling sites 35
3.2.1
Site 1 Fish farm 35
3.2.2
Site 2 Relic forest 36
3.2.3
Site 3 Experimental farm 36
3.3.
Sampling Procedure 38
3.5 Data
Analysis 39
CHAPTER 4:
RESULTS AND DISCUSSION
4.1
Results 41
4.2
Discussion 49
CHAPTER 5: CONCLUSION AND RECOMMENDATIONS
5.1
Conclusion 52
5.2
Recommendations 52
References 53
Appendices 69
LIST OF TABLES
Table
2.1: Some Insect Abundance by Species 7
Table
4.1: Species abundance, richness and diversity indices among three habitat
Types and across seasons 44
Table
4.2: Habitat comparison based of habitat species composition across seasons 45
LIST OF FIGURES
1. Insect order abundances in
three habitat types 41
2. Abundance of insect families recorded in
three habitat types Michael Okpara
University of Agriculture, Umudike 42
3. Abundance of
insect species recorded in three habitat types in Umudike 46
4. Variation in insect abundance in response
to changes in temperature (ºC)
and relative humidity (%) 47
5. Agglomerative clustering analyses based
on the habitat species composition 48
LIST
OF PLATES
1: The fish farm site 37
2:The Relict forest site 37
3: Experimental farm site 37
CHAPTER 1
INTRODUCTION
1.1
BACKGROUND OF THE STUDY
Insects
are hexapod invertebrates easily recognised by the possession of distinct three
body regions, namely: the head, thorax, and abdomen. Scientific/Evolutionary
records and all primordial document have a convergent opinion that insects evolved
on planet earth before humans (Speight et
al., 1999). Insects are different in their ways and play important ecological
roles for the survival of life on earth, and their diversity is indeed an intrinsic
part of the earth’s ecosystem (Samways, 1994). They are the most dominant
groups of organisms on the planet earth in terms of species richness, abundance
and biomass (Gullan and Cranston, 2010). Insects comprise more than half of earth
diversity of species (May, 1992).
Burine (2005) noted that insects are
attractive animals. It is believed that they outnumber humans over a billion
times. Though they account for the highest amount of biodiversity in the ecosystem,
they are not studied as much as other
animal species (Cardoso et al., 2011).
Insects are the only invertebrates that can fly (Voshell, 2002). The success of
insects in terms of abundance, diversity and global distribution can be
attributed to a wide range of factors (Samways, 1994). Their high reproductive
potential, capability flight, small body size, the extent of habitat colonisation,
ability to feed on a wide variety of foodstuffs are essential to their survival
and remarkable taxonomic and functional diversity (Tylianakis et. al., 2010). Insects are essential component
in several natural and transformed landscapes. They play a crucial functional
role that ensures the delivery of essential ecosystem services important in
agricultures, tourism, and natural resource conservation etc. (Samways 1994,
Tscharnke et.al., 2005). Insects are
so important that if all are to disappear, humanity probably will not last for
a month. Insects are better known for their deleterious effects on humans and
human activities. Aizen and Feinsinger (2002), noted that insects are habitat-
specific in nature, and highly sensitive to habitat fragmentation as a form of
disturbance. On land, insects reign (Grimaldi and Engel, 2005) and are the chief
competitors with humans for the domination of this planet earth (Wigglessworth,
1976).
Seasonality is a common phenomenon among insects (Wolda
and Wong, 1988). A sharp decrease in insect abundance during the dry season appear
to be restricted to tropical habitats that have a severe dry season (Janzen and
Schoener 1968; Janzen, 1973a, Janzen, 1973b, Wolda 1977). In the tropics, the
difficult period for most herbivorous insects is usually the dry seasons when the
leaves undergo a reduction in nutritional quality (Braby, 1955a). Other factors
that affect the pattern of insects distribution include competition, predation,
and numerical abundance of species, food web structure, and genetic factors,
short and long – term aspects of evolutionary rates and size of the insect (Thomas
et al., 1992). The abundance,
diversity and species richness of insect represent an equivalent variety of
adaptations to variable environmental conditions (Samways, 2003).
Biodiversity is a contraction of “biological”
diversity and it described the various biological organisms. It relates to the amount
and range of species in a particular community and has three components;
Species diversity; ecosystem (or habitat) diversity; and genetic diversity.
Species
diversity:
Species
diversity relates to the number of different species and the number of
individuals of each species within any one community (Samways, 2005). Species
diversity is computed based on the
number of species found in a given area without indicating the relative
dominance of any species.
The
more the species present in a sample, the “richer” the area (Grimaldi, and
Engel, 2005).
Ecosystem
(habitat) diversity defines the diversity of habitats. A variety of
habitat types are preferable because of its potential to accommodate a greater
species diversity, compared to a less divers habitat.
Genetic
diversity refers to the genetic variability of a species, which can be measured
directly by genetic fingerprinting or indirectly by observing differences in
physical features of the organisms within the population.
Evenness
describes the relative abundance of species within an area.
1.2 STATEMENT OF THE
PROBLEM
Studying
of insects can be an enormous task, and insect taxonomy requires continuous
work. Most of the studies on insects conducted in Nigeria have primarily been
on the insects’ diversity of specific order or family of insects. Very few have
considered the insect community altogether (Medler, 1980). Both the taxonomic
and ecological knowledge of insects have not been adequately investigated in
Nigeria. The distribution and abundance of many insect species are poorly known,
and their associated ecosystem services are often assumed (Kato et al., 2000). Estimates have shown that
Nigeria has lost 56.7% of its primary forest to anthropogenic activities such
as logging, subsistence agriculture, and collection of fuelwood and this may be
affecting the country’s insect communities, (FAO, 2010).
Insects play direct and indirect
roles in the lives of people through serving as pollinators, decomposers and
soil modifiers. Many people in Nigeria always see insects as harmful organisms.
Therefore, there is a need for raising the awareness of the citizenry on life
history strategies and a need to conserve them. Thus, the present study was
conceived to shape up the knowledge of insects, and this will contribute to the
conservation of these vital members of the living world.
1.3
AIM OF THE STUDY
The
aim of this study was to investigate the effect of seasonal changes on the distribution
and abundance of insect fauna in three
habitat types in the Umudike area of
Abia State, Nigeria.
1.4 OBJECTIVES
OF THE STUDY
The
research specifically has the following objectives,
1.
To generate baseline data for a long-term monitoring of the insect life of
the
area.
2.
To investigate the seasonal changes in insect diversity in three habitat
types,
in Umudike, Abia State, Nigeria.
3. To compare the abundance of
selected key insect species during the wet and
dry
seasons, in the three habitat types.
4
To determine the status and distribution of different insect groups in
the study
sites.
1.5 SCOPE
OF THE STUDY
The study was sought to identify insect taxa
that are common to these habitat types, and those that are specific to or
restricted to the habitats. The study was conducted during both the wet and dry
seasons in the three habitat types in Umudike. The sites chosen for the
research were:
i
The Relict Forest in Michael Okpara University
of Agriculture, Umudike;
ii
The Fish Farm Area in Michael Okpara University of Agriculture,
Umudike.
iii Experimental Farms in the Michael Okpara
University of Agriculture,
Umudike.
1.6 JUSTIFICATION OF THE STUDY
The attention paid to the study of
biodiversity has resulted to a growing interest in assessing the diversity of
insects and their relatives. Groups that dominate terrestrial and freshwater ecosystems
are essential indicators of the health of habitats (Grimaldi and Engel, 2005).
There is also the need to have an understanding
of seasonal change in insect species, composition and relative abundance between
different sites. The number of individuals or the abundance of a species is a basic
ecological parameter (Andrewartha and Birch, 1954) for critical consideration
when making management and conservation decisions (Sileshi, 2007). The present
study was directed towards the task of identifying insects’ fauna from
different habitat types in Umudike, Abia State, Nigeria. Information from this
study will not only be helpful for agricultural, medical and veterinary
purposes, but will also provide an insight into the insect species richness of
Umudike, Abia State, Nigeria. It is also
hoped that the result will offer useful information for the biodiversity
conservation as well as other management purposes.
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