Journal of Insects

Journal of Insects / 2014 / Article

Research Article | Open Access

Volume 2014 |Article ID 985684 | https://doi.org/10.1155/2014/985684

Rosina Kyerematen, Daniel Acquah-Lamptey, Erasmus Henaku Owusu, Roger Sigismund Anderson, Yaa Ntiamoa-Baidu, "Insect Diversity of the Muni-Pomadze Ramsar Site: An Important Site for Biodiversity Conservation in Ghana", Journal of Insects, vol. 2014, Article ID 985684, 11 pages, 2014. https://doi.org/10.1155/2014/985684

Insect Diversity of the Muni-Pomadze Ramsar Site: An Important Site for Biodiversity Conservation in Ghana

Academic Editor: Victoria Soroker
Received05 Sep 2013
Revised16 Dec 2013
Accepted05 Jan 2014
Published20 Feb 2014

Abstract

An inventory of species diversity of insects of the Muni-Pomadze Ramsar site, with special reference to species of conservation concern, was carried out as part of an evaluation of changes in the ecological character of the site, twenty years after designation. Samples were taken from two protected areas within the Ramsar site, in the wet (July), dry (January), and intermediate (June) seasons. Community diversity was characterized in terms of number of species accumulated, species richness, Shannon-Weiner indices of diversity, Pielou’s evenness, and Bray-Curtis similarity. A total of 134 families from 19 insect orders were recorded during the entire study period. Yenku Block A recorded the highest species richness (98) and the highest diversity index (14.97), corroborated by the highest Margalef index of 3.82 with a relatively even distribution of species (0.834) during the intermediate season, and recorded the lowest diversity (6.957) and species richness (41) during the dry season. On the whole, the Muni-Pomadzi Ramsar site showed a high diversity of insect species. The presence of species such as Junonia oenone and Papilio demodocus which are specialized in degraded habitats at Yenku Block A in large numbers is a clear indication of degradation of the forest, but the presence of forest species such as Salamis anacardii and Euphaedra crokeri is an indication that some parts of this reserve are still in good shape. A comparison of the butterfly species recorded with findings in a 1997 survey showed a marked increase in numbers from 75 to 130; this may be attributed to the habitat changes that have taken place at the site offering more diverse habitat types.

1. Introduction

Insects constitute a remarkably speciose group of organisms attributed mainly to their small size, which allows them to occupy niches not available to larger organisms. They are adapted to highly differing environments from the Arctic tundra to Alpine mountain summits as well as warmer tropical rainforest and coastal mangrove swamps and are able to tolerate extremes of temperature and other environmental conditions. Estimates of global species richness of insects vary from less than five million to as many as 80 million [1].

Insects are critical natural resources in ecosystems, particularly those of forests [2]. In addition to their role as efficient pollinators and natural/biological pest control agents, some insect species are important indicators in ecosystems management [3]. The habitat heterogeneity hypothesis simply predicts that more arthropod species will occur where different forms and species of plants provide greater structural heterogeneity in the vegetation [4]. Thus, greater resources are available for the coexistence of more species within each trophic group [5]. Arthropod diversity, which takes account of the relative abundance of species as well as their variety [6], would express an asymptotic relationship with increasing numbers of plant species and greater structural heterogeneity in the vegetation. Habitat heterogeneity at small spatial scales can favour the number and abundance of arthropod species in grassland [7], for example.

Insects are essential in the ecosystem by helping in nutrient recycling through leaf litter and wood degradation, carrion and dung disposal, and soil turnover. They play a major role in plant pollination and maintenance of plant community composition and structure via phytophagy [1]. Their demise will therefore result in the disruption of critical ecosystem services such as pollination and source of food. There is therefore the need for the conservation and protection of these species. Indeed the forest canopy is the heart of biotic diversity and thus it is imperative that the forest be properly managed to ensure the persistence of such a unique group of nature, which is critical for ecosystem health.

The Muni-Pomadze Ramsar site was designated in 1992. A few years after its designation, an assessment of the insect diversity of the site and its surroundings in relation to habitat characteristics was carried out by the Coastal Wetlands Management Project (CWMP) funded by the Global Environment Facility (GEF) [8]. This study was carried out to (i) present more detailed descriptive baseline data from an intensive entomological survey in an important site for conservation in West Africa, (ii) provide an inventory of the insect diversity and abundance with special reference to species of conservation concern, and (iii) assess the changes that have taken place in the ecological character of the Ramsar site.

2. Materials and Methods

2.1. Sampling Sites

The Muni-Pomadze Ramsar site is situated to the west of the coastal town of Winneba in the Central Region of Ghana, approximately 55 km from Accra and encompasses approximately 90 km2 of the watershed surrounding the Muni Lagoon as well as two protected areas: Yenku Block A and Yenku Block B [2, 9]. At the time of the current study, Yenku Block A, north of the village of Onyadze, was a degraded natural forest interspersed with pockets of farmlands and Teak, Eucalyptus, and Acacia plantations with a few thickets of dense shrubs. Yenku Block B which is close to Mankoadze near the coast consisted mainly of open savanna grassland interspersed with thickets and small trees. An Eucalyptus plantation bordered this area to the north at the foot of the Egyasimanku Hills with maize farms to the south.

2.2. Methods

The field studies were carried out in July 2011, January, and June 2012, the wet, dry, and intermediate seasons, respectively. Eight main sampling methods were employed in the collection of insects. Butterfly nets were used for butterflies, dragonflies, and other high flying insects; visual observations and counts were done for those insects that were missed by the nets and also for insects species of which individuals had already been captured since it was not necessary to capture more insects than necessary. At each site, one Malaise trap for smaller, flying, mainly nocturnal insects, one flight interception trap (FIT) designed to intercept insects in flight and five Charaxes traps for alcohol-loving butterflies and other insects that are attracted to fermenting foods were set up. Rotten banana, mashed and mixed with alcohol (palm wine and or beer), was used as bait for the Charaxes traps. In addition, pitfall and yellow pan traps (five of each) were randomly set up at each site for crawling and ground dwelling insects and insects attracted by the yellow colour; sweeping was done for vegetation-dwelling insects and handpicking with forceps was done for insects within easy reach. Light trapping which lasted about two hours was done for the nocturnal insects along a small stream at Yenku Block B.

In addition to the various trapping methods, random walk sampling was undertaken by three persons for a minimum of three hours during each sampling period twice each day for seven days at each site. Visual observations and counts were done mainly for the dragonflies since they are very fast fliers and difficult to catch.

Insects collected were killed using a killing bottle containing ethyl acetate and kept either in alcohol or glassine envelops for later examination and identification. Identification of insects was done with reference to the collection in the Museum of the Department of Animal Biology and Conservation Science, University of Ghana, as well as with reference to Carter [10], Gullan and Cranston [1, 11], Scholtz and Holm [12], Chinery [13, 14], Carcasson [15], Crowson [16], Belcastro and Larsen [17], Larsen [18], Miller [19], McGavin [20], Pinheiro and Ortiz [21], and Dijkstra and Clausnitzer [9].

3. Data Analyses

Cluster analysis was performed using Bray-Curtis similarity. Species contributing at least 20 individuals of the total abundance at each sampling site were included in the analysis. The original data was transformed (fourth root transformation) and standardized in order to minimize the weighting of numerically dominant species.

Five diversity indices were computed [22].(1)Total Species. —the number of species in each sample, that is, species with nonzero counts.(2)Total Individuals. —the number of individuals in each sample.(3)Species Richness (Margalef). —This is a measure of the number of species present, making some allowance for the number of individuals.(4)Pielou’s Evenness. This is a measure of equitability, a measure of how evenly the individuals are distributed among the different species.(5)Shannon-Wiener Index. It incorporates both species richness and equitability components.

4. Results

A total of 8634 individual insects belonging to 134 families and 19 orders were recorded in the survey. We present the butterflies and dragonflies data separately because of their numerical abundance, conservation interest, and role as indicators of ecosystem health but group all the other insects.

4.1. Butterflies

130 species of butterflies (Table 1) belonging to nine families were recorded during the survey: Nymphalidae, Papilionidae, Hesperiidae, Pieridae, Satyridae, Danaidae, Charaxidae, Acraedae, and Lycaenidae, with the Pieridae dominating with 39 species, followed by Nymphalidae with 37 species.


Species Yenku Block A Yenku Block B
July January June July January June

Euryphene barombyna 221001
Euryphene sp.110000
Euphaedra sarcoptera 1224000
Euphaedra edwardsi 210000
Euphedra hapalyce 512000
Euphaedra eleus 210000
Euphaedra medon 923000
Euphaedra crockeri 412000
Euphaedra xypete 1414000
Euphaedra sp.302000
Eurytela dryope 12323000
Pseudoacrea sp.9245501
Pseudoneptis ianthe 302000
Pseudoneptis sp.101000
Diestogina feronia 211000
Neptis melicerta 3633014
Neptis agatha 1351004
Neptis metella 229203
Neptis merosa 113100
Neptis seeldrayersi 002000
Salamis anacardii 311000
Junonia terea 43327206
Junonia oenone 1126560
Junonia octavia 01120010
Junonia sp.212110
Gnophodes chelys 335000
Gnophodes betsimena 021000
Kallima rumia 213000
Phalanta phalanta 1362975366
Ariadne enotera 8114001
Aterica galene 211000
Aterica sp.701000
Byblia achelola 242000
Byblia sp.113000
Hypolimnas salmacis 221010
Hypolimnas missipus 112000
Hypolimnas dinarcha 120000
Acraea epaea 2357613
Acraea zetes 458371365
Acraea terpsichore 0470024
Acraea pseudolycia 001000
Acraea doubledayi 002000
Acraea egina 103000
Acraea sp.12416411
Bematistis epaea 4560214
Hallelesis haliwa 210100
Hallelesis sp.411000
Ypthima itonia 013000
Bicyclus zinebi 1133100
Bicyclus safitza 1325203
Bicyclus auricruda 013000
Mycalensis safitza 115001
Mycalensis sp.501600
Bicyclus vansoni 020000
Bicyclus condamini 011000
Bicyclus vulgaris 010000
Papilio demodocus 188211121166
Papilio dardaunus 352010
Papilio nireus 23429000
Papilio bromius 312000
Graphium policenes 243101
Papilio menesthius 121002
Amauris niavus 325100
Amauris egialea 213100
Amauris sp.112100
Danaus chryssipus 2125813247
Danaus limniace 012000
Eurema brigitta 1789206540
Eurema senegalensis 92316211
Eurema hecabe 61383111
Eurema lisa 1134710
Eurema brenda 001000
Eurema sp.1325400
Colias philodice 421000
Pieris rapae 3460226
Pieris sp.4231110
Nepheronia thalassina 1815212329
Nepheronia argia 228180335
Nepheronia sp.536000
Leptosia alcesta 21833000
Leptosia medusa 181022000
Leptosia sp.835000
Appias phaola 013000
Dixeia astarte 108310
Dixeia cebon 8323423
Colotis erone 942272513
Colotis danae 723583
Colotis evippe 128141157
Colotis antevippe 1822420385
Colotis evinina 6399362
Colotis eunoma 405325
Anthocharis cardamine 446303
Belinois calypso 68158712866
Belinois creona 325469120
Belinois theora 1611912014
Belinois gidica 18471402
Belinois aurota 143122109
Belinois theuszi 9810710
Belinois hedyle 003000
Catopsilla florella 782931212169
Catopsilla sp.427165916
Euronia cleodora 001000
Mylothris chloris 5671342318
Mylothris poppea 349275119
Mylothris sp.511210406
Mylothris rhodope 178112026
Charaxes varanes 921402
Charaxes protocrea 211000
Charaxes etheocles 011000
Charaxes brutus 002010
Charaxes tiridates 513000
Charaxes cynthia 324100
Charaxes zelica 213000
Euxanthe eurinome 102000
Castalius carana 3213512
Lycaena helloides 2535270
Lycaena sp.621580
Meza indusiata 031080
Euchrysops albistriata 581133925
Osmodes adon 010000
Spalgis lemolea 011000
Poecilmitis chrysaor 001000
Anthene sp.001000
Pyrrhiades lucagus 61103767051
Amblyscirtis vialis 323010
Lerodea sp.432100
Hesperia leonardus 214002
Hesperia sp.321201
Oeneis polixenes 236100
Coliades chalyba 003000

Table 2 gives the diversity indices for the butterfly species for the three sampling seasons. Yenku Block A (YBA) was the most important site for butterflies, with the highest numbers ( and 1011 for July and June, resp.) and the highest species richness (, 111, and 122 for July, January, and June, resp.), which was corroborated by the highest Margalef index () of 15.07 in July, 16.85 in January, and 17.49 in June. Yenku Block B (YBB) had low butterfly species richness in June () but relatively high abundance (). YBB had the lowest abundance () as well as a relatively low species richness () in January corroborated by the lowest Margalef index () 7.15 (Table 2).


Sample site (loge)

YBAJUL106106115.070.85473.986
YBAJAN11168416.850.75543.558
YBAJUN122101117.490.85134.09
YBBJUL608258.7860.73583.013
YBBJAN412697.150.83543.102
YBBJUN5310647.4610.86023.415

YBA: Yenku Block A; YBB: Yenku Block B; JUL: July; JAN: January; JUN: June; : species richness; : number of individuals; : Margalef’s index; : Pielou’s evenness index; : Shannon-Wiener index.

Yenku Block B (YBB) recorded a relatively lower evenness, () in July. The six species, Eurema brigitta, Papilio demodocus, Catopsilla florella, Acreae zetes, Phalanta phalanta, and Colotis antevippe, made up about 42% of the total numbers recorded at YBB in July. Both sites had a high evenness () in the wet (YBAJUL) and intermediate (YBBJUN) seasons (Table 2) with individuals evenly distributed among the different species. Yenku Block A (YBA) recorded a high diversity (Margalef index ) in January but with a low evenness () as a result of the dominance of D. chryssipus and Pyrrhiadis lucagus.

From the cluster analysis (Figure 1) the species population structure could be considered homogenous below a Bray-Curtis similarity of 50%. Homogeneity however begins to break down above 60%, leading to the formation of two clusters of species communities: YBAJAN, YBAJUL, and YBAJUN forming one cluster and YBBJUL and YBBJUN forming the other.

Figure 2 is a dendrogram showing the relationships between butterfly species occurring at Muni-Pomadze that contributed abundance of 20 or more using group-average linking on Bray-Curtis species similarity from fourth root transformed abundance data. Above a Bray-Curtis similarity of 60% there is a formation of two clusters with more than 40 forming the main cluster which further breaks down into four distinct clusters around 73%. Red-dotted lines indicate closely related species or species of close associations.

4.2. Dragonflies

Yenku Block B recorded the highest species richness () for dragonflies in July which was corroborated by the highest Shannon-Wiener () and Margalef () indices. Dragonflies were most abundant in July () at Yenku Block A with the lowest numbers recorded in January at Yenku Block B () (Table 3).


Sample (loge)

YBAJUL7771.3810.74761.455
YBBJUL10682.1330.83061.912
YBAJAN7691.4170.66081.286
YBBJAN5261.2280.89061.433
YBAJUN8441.850.7761.614
YBBJUN8401.8980.88741.845

YBA: Yenku Block A; YBB: Yenku Block B; JUL: July; JAN: January; JUN: June; : species richness; : number of individuals; : Margalef’s index; : Pielou’s evenness index; : Shannon-Wiener index.
4.3. Other Insects

A total of 3720 insects belonging to 19 other insect orders were recorded from the traps. Diptera was the most abundant (1932) as well as the most diverse order with 36 families, followed by Coleoptera with 21 families and Hymenoptera with 13 families (Table 4).


Yenku Block A Yenku Block B
Family July January June July January June

Gryllidae871561311
Acrididae6647514
Tettigonidae3041233
Tridactylidae025014
Tetrigidae211621
Formicidae819631753929
Apidae608415
Evaniidae131311
Sphecidae225018
Vespidae0311016
Braconidae37138615
Ichneumonidae224413
Scelionidae032121
Halictidae012211
Pompylidae104003
Chalcididae022014
Eulophidae103024
Tiphiidae201000
Blattidae659141
Mantidae201001
Noctuidae342004
Arctidae010102
Satyridae202003
Pieridae003112
Acraeidae001100
Nymphalidae012200
Termitidae112025
Rhinotermitidae001002
Kalotermitidae200001
Cercopidae511610268
Aleyrodidae024000
Aphididae003000
Fulgoridae001000
Cicadellidae231317913
Delphacidae002322
Membracidae010001
Pseudococcidae001001
Dictyopharidae100201
Psyllidae003034
Acanalonidae100001
Flatidae001000
Isotomidae3332213227
Calliphoridae2253123
Sepsidae003500
Tachinidae451301219
Sarcophagidae3115136
Culicidae15834617
Muscidae219317
Tephritidae6924294522
Drossophilidae1532435993
Phoridae11142471528
Tipulidae402003
Asilidae002704
Diopsidae000001
Dolichopodidae112904
Syrrphidae2175210
Rhagionidae001003
Stratiomyiidae002001
Bombylidae202101
Tabanidae19028103
Glossinidae1092008
Simulidae200301
Mycetophilidae004009
Sciaridae002006
Chironomidae000301
Ceratopogonidae003002
Conopidae002300
Lauxanidae000002
Psychodidae001000
Cecidomyiidae102000
Platypezidae001000
Trichoceridae001004
Acroceridae000002
Empididae00213018
Therevidae103031
Otitidae0012003
Anthomyiidae0008011
Bibionidae000703
Chrysomelidae113121928
Carabidae23014842
Tenebrionidae316100
Scarabaeidae167044202
Mordellidae501811
Phalacridae002001
Coccinellidae200030
Dermestidae000400
Meloidae000300
Curcujidae0160014
Scolytidae001100
Lampyridae0051302
Staphylinidae501552051
Ptinidae001001
Lucanidae002001
Hesteridae002000
Anthicidae000001
Cleridae000001
Scaphididae002000
Curculionidae506106
Cerambycidae101002
Hydropsychidae5031404
Polycentropodidae300005
Philopotamidae001400
Leptoceridae2011002
Psychomyiidae000200
Thripidae2077113
Forfinculidae102001
Labiidae002010
Carcinophoridae011002
Libellulidae102001
Coenagrionidae000001
Pyrrhocoridae113203
Coreidae101200
Pentatomidae313102
Reduvidae013121
Lygaeidae002112
Berytidae011000
Largidae200011
Nepidae000100
Alydidae001100
Cydnidae102001
Thyreocoridae101002
Ascalaphidae001000
Sialidae000100
Phasmatidae103001
Oligotomidae001000
Machilidae000001
Panorpidae000001

The diversity indices for the total of 127 insect families caught in the traps are presented in (Table 5) to give a comparison for the two sampling sites. Yenku Block A recorded the highest family richness () with a diversity (() and ()) in June, but the lowest family richness () and the lowest family diversity () in January. Yenku Block B recorded the highest abundance of with richness of in June. This was reduced to and in January. Insect diversity was the highest at both sites in June (intermediate season).


Sample (loge)

YBAJUL595139.2940.65442.668
YBAJAN413146.9570.6942.577
YBAJUN9865114.970.83473.827
YBBJUL6347210.070.82453.416
YBBJAN422277.5580.80753.018
YBBJUN91151512.290.44051.987

YBA: Yenku Block A; YBB: Yenku Block B; JUL: July; JAN: January; JUN: June; : species richness; : number of individuals; : Margalef’s index; : Pielou’s evenness index; : Shannon-Wiener index.

A cluster analysis using Bray-Curtis similarity was performed for all the insects collected from the traps at both sites for the three sampling seasons (Figure 3).

The insects were averaged over the orders and similarity analyses were performed on all 3720 insects from the 19 orders collected from the traps over the entire sampling period. The cluster analysis revealed three distinct clusters/groupings above a Bray-Curtis similarity 25% (Figure 4) with homogeneity below a Bray-Curtis of 20%, indicating, a high level of dissimilarity in distribution. This gives an indication of the evenness of the distributions of insect orders at the Ramsar site.

5. Discussion

5.1. Butterflies

130 species of butterflies belonging to nine families were recorded during the survey. From the diversity indices for the butterfly species calculated for the three sampling seasons, the lowest abundance of butterflies at YBB in January () as well as a relatively low species richness () corroborated by the lowest Margalef index () 7.15 can be attributed to the fact that in January most of the vegetation covers at Yenku Block B (YBB) had been removed by burning, a common practice for that time of the year. This was in contrast to a study on butterflies of two sacred grooves in the Eastern Region of Ghana carried out by Nganso et al. [23] which reported that butterflies were more speciose and diverse in the dry season most probably due to higher temperatures.

The low evenness () at YBB in July can be attributed to the dominance of Eurema brigitta, Papilio demodocus, Catopsilla florella, Acreae zetes, Phalanta phalanta, and Colotis antevippe which constituted about 42% of the total numbers recorded at YBB. These are typically open country, grassland species, and their dominance at Yenku Block B was not surprising given the open nature of the vegetation which allows for free flight and easy movement.

Factors such as resource availability for adults and larval host plants, behavioural traits, and interaction with other species [21] may explain the increase in butterfly richness and diversity during the dry season at YBA. This underscores the importance of measuring and documenting local conditions as part of studies to determine species composition, even though these factors were not adequately measured in this survey.

Although Yenku Block A (YBA) recorded a high diversity (Margalef index ) in January, its low evenness () was due to the dominance of Danaus chryssipus and Pyrrhiadis lucagus. Pyrrhiades lucagus, a fast flier from the family Hesperiidae was observed in large numbers along the fringes of the forest and also in the Teak and Acacia plantations at Yenku Block A, most probably feeding on the nectar from their flowers. D. chryssipus, though an open savannah species, was found in large numbers at Yenku Block A where portions of the Eucalytus plantation had been cut down and converted to maize and cassava farmlands, providing adequate food resources as well as pockets of open areas for easy flight for these species. Their larvae feed on milkweed (Asclepias spp.) and other related species.

The species population structure could be considered homogenous, below a Bray-Curtis similarity of about 53%, however, homogeneity begins to break down leading to the formation of two clusters of species communities around 58%: YBBJUL, YBAJUL, YBAJUN, and YBBJUN forming one cluster and YBAJAN and YBBJAN forming the other (Figure 1). From the cluster analysis Pyrrhiades lucagus, Danaus chrysippus, Mylothris chloris, Belinois calypso, and Catopsilla florella, for example, (linked by red-dotted lines) cluster above a Bray-Curtis similarity of 80% (Figure 2). Each of these five species was recorded in excess of 150 individuals. They have similar behavioural traits and most feed on the same or related plant species and so their clustering together is to be expected.

Species of butterflies such as Papilio demodocus, P. nireus, Junonia oenone, and J. terea are known to be now much more common in West Africa than they ever were due to the widespread destruction and fragmentation of forest cover that has taken place in this part of Africa [24]. They are specialized in degraded habitats and open spaces and very few would ever be met within forest of good condition. Papillio demodocus was observed in large numbers in the open grassland areas and also along the beach close to the Muni Lagoon. Junonia oenone, for example, though common to both sites, was recorded mainly as singletons at Yenku Block A but in much larger numbers in the thickets and grasslands along the coastal villages of Mankoaze and Akosua which were sampled as part of Yenku Block B. The presence of these species, especially at Yenku Block A, is therefore a clear indication of the forest degradation that has taken place at this site and thus can be considered as clear-cut indicator species of forest disturbance. In theory, these species are known to be generally common to have fairly wide ranges and to colonize both intact and disturbed forests [6]. The high numbers especially of J. terea and P. nireus recorded at Yenku Block A also suggest that the degraded forest at Yenku Block A is not in a particularly good shape.

Species common to both sites were Phalanta phalanta, Acraea zetis, Danaus chryssipus, Eurema brigitta (which was the second most abundant species recorded), Catopssila florella, Colotis evippe and Colotis antevippe. Species such as Nepheronia thalassina, Nepheronia argia, Belinois calypso, Mylothris chloris, and Mylothris poppea, though common to both sites, were more abundant at Yenku Block A, a degraded natural forest interspersed with pockets of farmlands, Eucalyptus, Teak, and Acacia plantations with a few thickets of dense shrubs. These species are commonly found in African woodlands.

Satyrids are generally dusty to dark brown and blend well with the dark vegetation of forested areas and forest undergrowths and are associated with grasses. Species such as Bicyclus safitza and B. zinebi which are associated with woodland and forests throughout Africa [15] were recorded in relatively larger numbers at Yenku Block A. The increased presence of grass-feeding Satyrine species is an apparent sign of forest disturbance [24]. Grasses are generally uncommon on the Afrotropical forest floor [25] but can colonize and spread in abundance when light penetration into the forest proper increases as a result of, for example, increased edge to interior habitat or degradation of the forest canopy [26]. This coupled dynamic between grasses and Satyrines also signals the high potential of this group as indicators of forest condition, an attribute that could be beneficially exploited to help direct limited conservation resources in economically disadvantaged countries, for example, to identify priority sites for formal protection or to steer restoration efforts [26].

Most of the eight species of Euphaedra such as E. crockeri and E. eleus were found along footpaths deep in the forests of Yenku Block A. Nepheronia spp. are high fast fliers which can be seen darting in and out of the top of trees and so were recorded in larger numbers at Yenku Block A which had more trees than Yenku Block B, a more grassland open area.

The Lycaenids such as Lycaena helloides, Castalius carana, and Euchrysops albistriata were found around drying puddles of water and along paths and roads in relatively larger numbers at Yenku Block B. Most of these butterflies are associated with ants that were abundant in the sampled areas.

5.2. Odonata

Dragonflies are relatively ever-present in freshwater wetlands, and occupy a critical trophic niche in these systems. The adults are easily sampled; they are insects that are susceptible to human disturbance and constitute good candidates for wetlands assessment [27]. Dragonflies can serve as biological indicators of environmental health [2830]. According to [1] vegetation covering can lead to a decline in population of adult dragonflies or, in contrast, cause an increase in the species diversity according to Clark and Samways [31] and Acquah-Lamptey et al. [28].

All the dragonfly species recorded in Yenku Blocks A and B are widespread species and therefore classified as of least concern [32]. The presence of species such as Pantala flavescens and Tramea basilaris indicate open areas or nearness to open areas, whereas the presence of Phoan iridipennis infer that the area it occurred in is adequately shaded, occurring especially in gallery forests [33]. Crocothemis erythreae is an open area species and usually prefers areas close to large water bodies which was the case at YBB. Palpopleura lucia and Orthetrum julia are known to be widespread and very common species; hence the high abundance recorded in this study was expected.

5.3. Other Insects

A total of 3720 insects belonging to 19 orders were recorded from the traps. Diptera was the most abundant (1932) as well as the most diverse order with 36 families, followed by Coleoptera with 21 families and Hymenoptera with 13 families. The high numbers of Dipterans may have resulted from the use of the Malaise traps and the flight interception traps employed in this study which are basically designed to trap small flying insects, mainly Diptera and Hymenoptera. They were set up close to streams and many of the insects recorded were aquatic species that may have been trapped on emergence or as they came to lay eggs in or close to the water. Flight interception traps are also designed to intercept the flight of small to medium-sized flying insects. In a baseline survey conducted in 1997 [8], 3151 insects belonging to 15 orders were recorded with Coleoptera, being the most abundant order (1258 individuals) followed by Hymenoptera (716) and Lepidoptera (416 individuals).

Insect diversity was the highest at both sites in June (intermediate season) most probably because, during this time of the year, there are ample food resources for the insects and rainfall is not too heavy since heavy rainfall sweeps most insects away and destroys many of their food resources. The high numbers of Dipterans accounted for the highest abundance () and the lowest evenness () at Yenku Block B in June. Most of the Dipterans sampled were aquatic and at this time of the year water levels are just right for them whereas during the wet season most of these Dipterans as well as other aquatic insects are swept away or dislodged during the heavy rains.

From the cluster analysis the insect species composition at Yenku Blocks A and B had a fairly similar species distribution for June and July (Figure 3). There was a distinct cluster of species communities for both Yenku Blocks A and B in January indicating similar species composition and distribution, as was the case for the butterfly species composition, the burning that had occurred during the dry season accounted for the low numbers and diversity at both sites during the January sampling. The dominance of Hymenoptera, Diptera, Collembola, Orthoptera, and Homoptera at both sampling sites in January may explain the similarity.

The cluster analysis performed on the insect orders revealed three distinct clusters/groupings above a Bray-Curtis similarity 25% with homogeneity below a Bray-Curtis of 20%, indicating a high level of dissimilarity in distribution (Figure 4). It is not surprising that Thysanura and Mecoptera form outside the three main clusters since they have a similar distribution spending most or part of their life cycle in moist decaying vegetation and soil. Thysanura are among the most primitive of all insects.

It is interesting to note that Diptera, Hymenoptera, and Coleoptera cluster together around 95% indicating a high level of similarity in distribution. These three orders contributed to 81% of the entire insect collection from the traps at both sites.

The presence of dung beetles, Scarabaeidae, in large numbers at Yenku Block A during the wet season sampling is an indication of the presence of large mammals at this site which is typical for the kind of vegetation found at the site.

5.4. Changes in Insect Species Composition over the Twenty Years of Site Designation as a Ramsar Site

The total number of species recorded in the current study and composition of the various taxonomic groups suggest an increase in insect abundance when compared with the findings in the 1997 survey. However, with the exception of butterflies, a direct comparison of overall insect abundance recorded in the two studies would not be appropriate because of the limited range of techniques and different sampling methods used in the 1997 study. The sampling methods used for butterflies in the two studies were similar and therefore the results are comparable. 74 (57% of the total) butterfly species were common to both Yenku Blocks A and B in this survey as compared to 22 species (29.3% of the total) that were common to both sites in 1997 [8]. 56 species (43% of the total) were recorded only in Yenku Block A compared to 32 species (42.6% of the total) in 1997. The 130 species of butterflies from 9 families recorded in the current survey is an increase from the 75 species from five families recorded during the 1997 baseline survey [8]. Species such as Charaxes fulvescens, Graphium adamastor, Belinois ianthe, and Bebearia sophus were recorded in the 1997 survey but not in the current survey. Many species belonging to the genera Belinois, Mylothris, Eurema, Euphaedra, Colotis, and Acraea look similar in flight and can only be properly identified when captured and critically examined. The fewer number of those species recorded by Gordon and Cobblah [8] may therefore be accounted for by the fact that their records may have been based mostly on insects observed in flight and hence the possibility of mixing up these species.

No butterfly species were recorded only in Yenku Block B in the current survey; however Gordon and Cobblah [8] recorded two species (2.7% of the total) that were found only at Mankoadze (Yenku Block B) in 1997. Gordon and Cobblah [8] state that several of the butterfly species such as Papilio demodocus, P. nireus, Neptis morosa, Bicyclus safitza, and Charaxes varanes recorded at Mankoadze (Yenku Block B) were strongly associated with thickets. However in the current study, P. nireus was not recorded at Yenku Block B but was rather observed in relatively large numbers at Yenku Block A darting between the Acacia trees and the open fields that had been cultivated with maize and cassava. Neptis merosa was recorded only as a singleton at Yenku Block B.

Many habitat changes had occurred at the Ramsar site since its designation in 1992. The presence of pockets of farmlands created from portions of the Eucalytus plantation within Yenku Block A that had been cut down and converted to maize and cassava farmlands, for example, had created a wider range of habitat types and adequate food resources as well as pockets of open areas for easy flight allowing for the colonization of more butterfly species. At the initial stages of habitat loss, new habitats occur as gaps within the original habitat; however, as the proportion of new habitats increases in the landscape, the remaining areas of original habitat will be smaller and more isolated from one another [34].

6. Conclusion

The survey revealed high levels of insect diversity at the Muni-Pomadze Ramsar site with 134 insect families belonging to 19 orders recorded, including 130 species of butterflies. Butterfly species richness was greater at Yenku Block A (130) than at Yenku Block B (74). As was the case in a survey conducted in 1997 [35], there were clear differences in butterfly fauna of the two sites which represented somewhat different habitats. These differences indicate a fine grained response by the butterfly communities to habitat changes and confirm the suggestion by [8] that butterfly monitoring at Muni would provide useful ecological indicator data to compliment those of mammals, birds, and plant species monitoring.

Species such as Junonia oenone, J. terea, Papillio nireus, and P. demodocus are specialized in degraded habitats and open spaces and very few would ever be met within forest of good condition. Their presence especially at Yenku Block A in relatively large numbers is a clear indication of forest degradation (the result of the conversion of parts of the forest into farmlands).

The presence of deep forest species such as Salamis anacardii, Euphaedra crokeri, Charaxes tiridatus, Hypolimnas salmacis, and Diestogina feronia however is welcome news and an indication that some parts of this reserve are still in good shape. Obviously, the forests areas at Muni-Pomadze serve as refuges for displaced species from areas where farming and other human activities have disturbed these insects.

The Muni-Pomadzi Ramsar site is still in a relatively good condition although more efforts should be put in place by the Forestry Commission of Ghana to maintain it and prevent encroachment by farmers and loggers since it is a site for conservation not only in Ghana but also in West Africa.

Conflict of Interests

All authors agree to the publication of this paper and they do not have any conflict of interests with any party or commercial identity. They have no involvement that might raise questions of bias in this reported work or in its conclusions, implications, or opinions.

Acknowledgments

This study was undertaken under the building capacity to meet the climate change challenge (B4C) - Ghana project, which is implemented by a consortium of three institutions, the University of Ghana (lead), the Centre for African Wetlands, and the Ghana Wildlife Society, with funding from the Open Society Foundations. The authors are grateful to the Open Society Foundations for the funds that made the study possible.

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Copyright © 2014 Rosina Kyerematen et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


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