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Article

Can Monoculture Timber Plantations Conserve More Ant Communities Than Adjacent Natural Forests?

by
Thembekile A. Mthimunye
and
Thinandavha C. Munyai
*
School of Life Sciences, College of Agriculture, Engineering and Science, University of KwaZulu-Natal, Private Bag X01, Scottsville 3209, South Africa
*
Author to whom correspondence should be addressed.
Diversity 2022, 14(6), 430; https://doi.org/10.3390/d14060430
Submission received: 8 April 2022 / Revised: 24 May 2022 / Accepted: 25 May 2022 / Published: 27 May 2022
(This article belongs to the Special Issue Invertebrate Diversity in Fragmented Habitats)
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Abstract

:
Understanding where biodiversity is and how it is distributed is crucial to conserving vulnerable and dynamic ecosystems. Although natural forests support greater diversity and are vital for the conservation of organisms, recent studies have argued that monoculture plantations can be used as an alternative habitat for forest species. We investigate how ant diversity patterns and assemblage composition vary between monoculture timber plantations and adjacent natural forests using pitfall traps in the Natal Midlands of South Africa. A total of 326 ants were collected, comprising 4 subfamilies, 13 genera, and 30 species. The blue gum plantations had the highest species diversity compared to other habitats. Although two species were found exclusively in the natural forest, it had the lowest ant diversity. Generally, species assemblages between the compared plantations and the natural forests were distinct. Monoculture plantations affect ant communities, leading to a change in their distribution patterns and assemblage composition. Determining how these rapidly expanding plantations affect biodiversity at different scales is essential for preserving indigenous fauna. Although our findings proposed that blue gum plantations have the potential to conserve ant taxonomic diversity compared to pine plantations, we recommend that future studies investigate the response of ant functional diversity to monoculture timber plantations in the region.

1. Introduction

Indigenous forests contain a large proportion of native biota and are vital for the conservation of organisms [1]. Although the forest biome is the smallest globally, it contains 65% of the global terrestrial fauna [2], leading to a high conservation value [3]. It is characterised by high species diversity due to abundant resources offering diverse niches for organisms [4]. Nonetheless, they are mostly valued based on the vertebrate taxa they support [5]. In addition to conservation value, the ecosystem services provided, which range from carbon sequestration and air purification to nutrient recycling and soil erosion prevention, are vital for environmental health. However, regardless of all these benefits, they are increasingly being fragmented or destroyed and replaced with other land uses, such as monoculture plantations, which are known to establish well in previously forested habitats.
Afforestation and, in some cases, reforestation with monoculture plantations is considered a cost-effective technique for large-scale timber production worldwide [6,7]. Apart from their economic significance, monoculture plantations can absorb atmospheric carbon and potentially rehabilitate biodiversity in previously depauperate areas, including destroyed natural forests, degraded grasslands, and non-productive agricultural land [8]. Armstrong and van Hensbergen [1] stated that pine (Pinus) plantations might benefit adjacent native forest species as they provide forest organisms with alternative resources and facilitate germination and maturation in plants. Brockerhoff et al. [9] supported that these intensely managed plantations have great potential for conserving native species since they improve habitat connectivity, reduce edge effects, and offer complementary forest habitats.
However, these timber trees do not occur naturally in most parts of the world. They may negatively affect biodiversity since they alter the vegetation structure and composition, resulting in homogenised habitats [10]. As the timber plantations continue to expand, the ecosystem structure and functioning of natural habitats is disrupted [10]. Kanowski, Catterall, and Wardell-Johnson [6] found that the exotic pines and blue gum (Eucalyptus) plantations have minimal positive effects on biodiversity compared to the other plantation types. This is more prominent when these plantations are established on rainforest landscapes since the habitat quality of native organisms is reduced [6]. Therefore, non-native plantations may have positive or negative ecological consequences, depending on the scale at which they are planted, the previous land use, and habitat structure. Understanding the biodiversity patterns in human-managed landscapes is essential for conservation, especially since anthropogenic activities increasingly replace natural vegetation. With invasive plantations taking up more land, it is necessary to investigate how different organisms are affected by these exotic forests.
Environmental disturbances such as burning, grazing, and other anthropogenic activities cause spatial heterogeneity, which either favours or hinders species diversity at the spatial or temporal scale [11,12]. Such activities play a significant role in changing the habitat openness, which alters microhabitat conditions such as temperature [13,14]. Temperature has been widely reported as one of the important factors determining ant diversity patterns and assemblage composition [15,16,17,18], particularly for its effect on foraging activity [16,19].
Insects constitute 60% of all known global terrestrial fauna, making them a dominant group [20]. Furthermore, they are useful in biodiversity modelling studies as bioindicators of environmental quality and are ecologically related to other taxa [5]. Among insects, ants are highly diverse and abundant taxa. They occupy a wide range of habitats and respond rapidly to disturbances caused by land-use changes [16]. Relatively simple sampling techniques make it possible to study biodiversity patterns at different scales.
In a previous study in South Africa, Armstrong and van Hensbergen [1] mainly focused on the effects of converting natural vegetation into monoculture timber plantations on vertebrate taxa. Others were conducted in tropical areas [6,9] and temperate regions [9]. However, limited research [21,22] has investigated diversity and distribution patterns of invertebrates, specifically in the Afrotropical areas where timber production is high and undisturbed natural forests are less common. Improving knowledge on biodiversity protection in these rapidly expanding monoculture plantations is essential, especially in South Africa, a country rich in biodiversity and endemic species. A study conducted by Munyai et al. [23] in the Natal Midlands of South Africa reported that subterranean ant species diversity was lowest in the blue gum plantation compared to adjacent grassland and natural forest.
Therefore, this study investigated ant species diversity patterns and assemblage composition between monoculture plantations and natural forests in the Natal Midlands of South Africa. In particular, we investigate (ⅰ) ant species diversity patterns and how their assemblage composition differs between three habitat types and (ii) evaluate the level of dissimilarity between the habitat types. It was hypothesised that monoculture plantations alter ant assemblages, leading to differences in ant species diversity and assemblage composition compared to adjacent natural forests.

2. Materials and Methods

2.1. Study Area

This study was conducted at the University of KwaZulu-Natal Umgenipoort Research Facility (29°29′0.1208″ S; 29°54′0.0146″ E) situated in the KwaZulu-Natal Midlands (Figure 1) between Pietermaritzburg and the foothills of the Drakensburg mountains in the KwaZulu-Natal province of South Africa. This area experiences hot summers and cold, dry winters. The mean temperature of the site is 24.8 °C, with an average annual precipitation of 800 mm [23]. The main vegetation types in the area include the Mooi River Highland Grassland and Southern Mistbelt forest [23]. This native forest consists of tree species such as the Celtis Africana, Afrocarpus Falcatus, Calodendrum capense, Vepris lanceolate, Zanthoxylum davyi, and Podocarpus henkelii, which are mostly deciduous and semi-deciduous [24]. However, the predominant tree species in the forest is Podocarpus henkelii [24].
The Umgenipoort Research Facility and adjacent properties are further dominated by timber monoculture plantations (pine and blue gum), with perennial rivers flowing through the landscape. The three habitat types were sampled in this study: (1) Pine plantations, (2) blue gum plantations, and (3) southern Mistbelt forest, a natural habitat, which is not managed and experiences minimal to no degradation. Each habitat type was replicated seven times (Table S1; Figure S1). Although the investigated monoculture tree plantations on the site were identified at the genus level (Pinus and Eucalyptus), the dominant plantations in the Natal Midlands include Eucalyptus grandis, E. nitens, E. smithii, Pinus elliotii, and P. patula [25,26,27]. Over the years, these species have been planted in some areas in the province, including the current study area. The estimated area covered by the natural forest is 1.14 km2, and the plantations cover a combined area of approximately 2 km2.

2.2. Ant Sampling

Ground-dwelling ants were sampled from each of the three habitat types using standardised pitfall trapping [18,28,29,30]. The pitfall traps were placed on the ground with the lid removed and the mouth (62 mm in diameter) of the pitfall trap at the same level as the ground surface. For each replicate, traps were laid 10 m apart, in a 2 × 5 sampling grid, totalling 10 pitfall traps per sampling grid. Each pitfall trap was filled with 50% propylene glycol solution, which does not result in the attraction or the repulsion of ants [18]. Since propylene glycol has a slow evaporation rate, the traps were left at the study site for seven days in March 2021 to maximize the specimens captured. Seven days has been suggested as an appropriate sampling interval for this method [31,32]. For each habitat type, seven replicates were established. To prevent psuedoreplication, the replicates were separated by a distance of >300 m [18]. The collected ant samples were washed, sorted, and stored in vials containing 70% ethanol in the laboratory for identification. The specimens were identified at the genus level using Fisher and Bolton [33]. Online databases viz., AntWiki (http://www.antwiki.org/, accessed on 11 June 2021) and AntWeb (http://antweb.org/, accessed on 11 June 2021) were then used to separate ant species where possible. Specimens that could not be identified to species level were assigned to morphospecies. All voucher specimen are held at the School of Life Sciences, University of KwaZulu-Natal, in the Pietermaritzburg campus and will later be deposited at Iziko Museum of Cape Town.

2.3. Statistical Analysis

Sample coverage, which measures sample completeness in each habitat type for ant species diversity, was explored using the iNEXT online software program [34]. The number of individuals caught per sample was calculated and presented as species occurrence (Table 1). A one-way ANOVA was used to compare species richness between the habitat types. Quantitative metrics of species diversity, the Shannon–Wiener diversity index (H’), and Evenness (J’) in PAST [35] were used to investigate and compare ant diversity in the three sampled habitats. The Shannon entropies (diversity indices) of each habitat were converted to true diversities (effective numbers of species) as outlined in Jost [36]. The effective number of species represents the number of equally abundant species required to obtain the diversity value in the dataset [36,37]. The difference in ant assemblage composition across the habitats was explored through non-metric multidimensional scaling (NMDS), cluster analysis, and ANOSIM, using the Bray–Curtis similarity measure and square root transformation in Primer version 6 [38]. SIMPER was used to determine habitat dissimilarities and the main species contributing to this, utilising the S17 Bray Curtis similarity matrix and a cut-off low contribution of 90% [38].

3. Results

3.1. Sample Coverage for Species Diversity and Species Occurrence

In total, 326 ant specimens were collected, with 30 species in 13 genera and four subfamilies represented (Table S2). The average sample coverage for species diversity was 0.95, indicating that the sampled ant communities represent each habitat type, even though the blue gum habitat had the highest number of observed species and species occurrence (Figure 2 and Table 1).
The highly diverse subfamilies were Myrmicinae (50% total ant abundance) with 15 species in 6 genera, followed by Formicinae (27% total ant abundance), consisting of 8 species in 3 genera. The most specious genera were Tetramorium (7 species) and Lepisiota (5 species) in the Myrmicinae and Formicinae subfamilies, respectively. Five species were common to all the habitat types: Dorylus helvolus, Crematogaster UKZN_01 (castanea complex), Monomorium UKZN_10, Solenopsis UKZN_03, and Tretramorium UKZN_03 (setigerum gp.). The blue gum and the pine plantations had the most species in common (11 species), while 1 species (Tetramorium UKZN_32 (weitzekeri gp.)) was common to the blue gum plantation and the natural forest (Table S2). Seven species were restricted to the blue gum plantations and eight species were found explicitly in the natural forest, mainly from the genus Hypoponera (four species) (Table S2). Parasyscia UKZN_06 was also exclusively found in the natural forest, with 23 individuals collected from this habitat type (Table S2). Only three species (Lepisiota UKZN_02 (capensis gp.), Pheidole UKZN_07, and Tetramorium UKZN_10 (simillimum gp.)) were restricted to the pine plantations (Table S2).

3.2. Species Diversity

The highest number of species (19) was observed in the blue gum plantations (Table 1, Figure 3). However, there was no significant difference in species richness (Anova, F = 2.07, MS = 12.33, df = 2, p = 0.16) among the three habitat types (Figure 3). Variation in ant species diversity in the habitats was estimated using the Shannon–Wiener diversity index, converted into true diversities. Ant species diversity was highest in the blue gum plantations (H’ = 2.38), followed by the pine plantations (H’ = 2.31), which was also more even (J’ = 0.72) (Table 2). The natural forest had the lowest species diversity (H’ = 1.96) (Table 2).

3.3. Assemblage Composition

The non-metric multidimensional scaling (NMDS) plot (Figure 4) revealed that although not completely distinct, there was a variation in assemblage composition across the habitats. Most pine and blue gum plantation replicates were close together as they shared most ant species but were clearly distinguishable in assemblage composition (Table S2). The samples of the natural forests showed variation among them, yet were separable from other habitat types due to the presence of Hypoponera species, which was found only in this habitat type. Only Pheidole UKZN_07 was collected from the fourth pine replicate, resulting in an outlier in the pine plantations.
Relatively similar results were obtained through cluster analysis. Generally, the habitat types overlapped in assemblage composition (Figure 4 and Figure S2). However, some samples were clustered together, showing that many species were shared between the replicates of different habitat types (Figure 4). Notably, replicates from the pine and the blue gum plantations were clustered with some replicates of the natural forest (Figure S2).
A significant difference in assemblage composition between the three habitat types was reported from a one-way ANOSIM (ANOSIM, Global R = 0.13, p = 0.034, no. of permutations = 999), due to the variation in assemblages between the habitat types (Table S2). A pairwise ANOSIM comparing the similarity between two habitat types simultaneously showed contrasting results. The p-values were greater than 0.05 for all three comparisons (Table 3), indicating that the compared habitats were identical. This was also supported by the R statistic values (close to zero) in all the comparisons (Table 3). However, the similarity between the blue gum and the pine plantations is questionable (p = 0.06) (Table 3).

3.4. Percentage Similarity between the Habitats

The average similarities in assemblage composition in the sampled habitat types were 33.75%, 24.73%, and 29.74% for the blue gum, natural forest, and pine plantation, respectively (Table S3). The average dissimilarity percentage between the blue gum and the natural forest was 73.19, while the dissimilarity between the blue gum and the pine plantation was 73.02%. The natural forest and the pine plantation had the highest average dissimilarity percentage of 78.40 (Table S3). These results are similar to those reported in the NMDS plot, as the natural forest and pine plantation were more separated (Figure 4). The main species that contributed to the observed dissimilarities between the habitats are listed in Table 4. These species had a high dissimilarity/standard deviation ratio compared to other species, making them the discriminating species among the habitats (Table S3).

4. Discussion

Monoculture plantations are often characterized by poor biological diversity and limited resource availability. Nonetheless, this should not be generalised to all organisms. The current study investigated the effects of monoculture plantations on ant communities, specifically comparing ant diversity and assemblage composition in the natural forests, pine, and blue gum plantations. It further determined how distinct these habitat types were in assemblage composition if the difference existed.

4.1. Ant Species Diversity

The current study results are comparable to those reported in previous studies. For example, a similar study by Ratsirarson et al. [39], conducted in Cape Peninsula National Park, South Africa, collected a relatively similar number of leaf litter invertebrate species (19 and 17) as in this study (19 and 14) from the blue gum and pine plantations, respectively. However, compared to the latter study, more species were collected from the natural forests (22). It was suggested that the forest type and latitude were possibly responsible for such trends in the compared study [39], since the site was located in a region characterised by a Mediterranean climate.
The current study reported higher number of species in blue gum plantations as compared to the other habitat types (Figure 3, Table 2), even though the difference was insignificant. These results were similar to those obtained from Samways, Caldwell, and Osborn [21]. The latter study observed that although invertebrate species richness and diversity in exotic vegetation was low compared to native vegetation types, the blue gum plantations had the highest invertebrate diversity among the sampled exotic plantations [21]. Some studies have argued that adjacent vegetation with a similar structure as forests can support more forest species [40,41] since these sites gain species from the surrounding natural forests, which act as source areas [3]. This could have been the case in this study, as many species were common between habitat types (Table S2). Corresponding to the findings of this current study, Murray et al. [42] found that pine plantations had the lowest species richness in order Hymenoptera, Blattodea, and Acari. It was suggested that the seasonal response of arthropods to resource availability and moisture in the plantations should also be considered [42]. Similarly, Corley et al. [43] observed a reduction in ant species richness and the abundance of dense plantations.
In contrast to this study’s findings, natural grasslands supported high ant, spider, and orthopteran species richness compared to the surrounding pine plantations, as reported in a study conducted in the Natal Midlands, South Africa [44]. Notably, the open habitat of the grasslands enhances ant activity due to increased exposure to the sun, favouring this thermophilic taxon. Ant species richness was reported to be higher in primary forests of the Amazon, with a unique assemblage composition compared to secondary forests [3]. However, the former study was conducted at a large scale, in a continuum of indigenous forests, consisting of more ant species that are less tolerant to disturbance. This was further supported Achury and Suarez [5], as they reported high ant species richness in densely forested plantation areas compared to more disturbed sites in central Colombia. The type of land use activity and the level of disturbance might have contributed to similar conclusions from these past observations. In addition, most of these were conducted along the equatorial regions, with the largest land biomass made up of ants [3] and which experience high temperatures and speciation rates.

4.2. Ant Species Assemblages

It was argued that that abundant leaf litter reduces ground temperature, favouring the survival of generalist arthropod groups [10]. Although drivers of assemblage composition were not investigated in the current study, such an observation is consistent with low diversity in the pine plantations, a habitat characterised by deep, dense leaf litter in our study. Species sampled in the pine plantation of the current study were mainly generalist group (Crematogaster, Solenopsis, and Tetramorium) and are tolerant to a wide range of environmental conditions [12]. Correspondingly, Riedel et al. [45] found that generalists dominated plantations established on areas that were formerly pastures areas. Ant assemblages have a better chance of thriving in timber plantations since open habitats favour the establishment of understory vegetation to increase niches [46,47]. The current study’s findings support this speculation since the pine plantations had distinct ant assemblages compared with the natural forest.
Although ant assemblages varied among the habitat types, some samples of the natural forests were clearly separated from one another and overlapped with the other habitat types (Figure 4). This is explained by microhabitat heterogeneity within each of the three habitats, which accounts for the observed slight similarity of ant species assemblages, with some species having a broad range of environmental tolerance. Although timber plantations generally have low plant species richness, they may offer a complex habitat structure to ground-dwelling invertebrates. Budiaman et al. [48] postulated that clear cutting of timber plantations reduces favourable microhabitat conditions for ground-dwelling ants, causing a decrease in ant species communities and altered assemblages. Burghouts et al. [49] noted that horizontal habitat complexity affects ground-foraging invertebrate activity. This may be facilitated by salvage logging. Georgiev et al. [50] found that salvage logging enhances biodiversity, particularly invertebrate species associated with open habitat structures. Salvage logging was not notably observed in the sampled study site; nonetheless, the presence of dead or decaying wood within the blue gum plantation stands may have diversified ant nests and forage grounds [50,51].
Non-native plantations have an effect on invertebrates communities at the species level [21]. Particularly, woody plant invaders have a greater influence on arthropods than herbaceous plants species [52]. In this study, four Hypoponera species dominated the natural forests. These ants nest and forage in leaf litter, soil, decaying wood, and shaded microhabitats with adequate moisture and are generally predators [53]. This could explain their absence in plantations associated with dry soil and open habitats. In addition, species belonging to genus Parasyscia were only found in the natural forest (Table S2). These cryptobiotic species are leaf litter specialists, mostly nesting below rocks and decomposing logs [54], which offer protection against extreme soil temperatures experienced in open habitats [17]. Since ants use pheromones to communicate, dense vegetation may prevent chemical detection among populations and efficient foraging [55]. However, the close spatial proximity between the habitat types and the historical vegetation type, which were mainly grasslands and forests in this particular site, could explain why many species were shared between the habitats.
Vegetation height and density have an impact on epigeic insects since this alters ground surface temperature [56]. Although not measured in the current study, temperature differences associated with habitat openness could explain assemblage variations between the plantations and the natural forest. Andersen [13] proposed that ant species have different preferences in the amount of habitat openness they can tolerate. Warm temperatures favour ant survival by promoting forage abundance [57], foraging time [16], and ant productivity [58]. Controversially, temperature may be a limiting factor in ant species richness since it causes physiological stress in shade-adapted species, such as forest specialists [16,58]. It is essential to note that the morphology of the plants, rather than their status as indigenous or non-native, is more vital in affecting ground-dwelling invertebrates.

5. Conclusions

The findings of the current study showed no significant difference in species richness between the plantations and the natural forest, even though the blue gum plantations had the highest number of species and diversity. There was a variation in assemblage composition across the habitat types. Therefore, the effects of monoculture plantations on species should not be generalised for all taxa. Our study therefore supports that some of these monoculture plantations (for example, blue gum plantations) have the potential to conserve taxonomic ant diversity. Given that ants play a vital role in ecosystem functioning, the conservation of ants in plantations could reduce the tension between plantation production and biodiversity conservation in natural ecosystems. However, for a robust conclusion on this, future studies should consider investigating the variation in ant functional diversity with these habitat types.

Supplementary Materials

The following are available online at https://www.mdpi.com/article/10.3390/d14060430/s1, Figure S1: Landscape of the Umgenipoort Research Facility with the three habitat types (Natural forests (NF), Blue-gum (BG) and Pine plantations (PN), with their replicates, and the sampling design showing each habitat replicated seven times. The replicates are >300 m apart, sampled in a 2 × 5 sampling grid with sampling points located 10 m apart, Figure S2: Dendrogram showing similarities (based on the Bray Curtis similarity abundance data) in ant communities between the sampled habitat types (Blue-gum, Natural forests and Pine) and their replicates in Umgenipoort Research Facility, Table S1: The average canopy cover and the geographical coordinates (latitude and longitude) of each replicate in the three habitat types (Blue-gum, Natural forest and Pine) sampled in Umgenipoort Research Facility, Table S2: Ant subfamilies and species, with their abundance and richness in each habitat types (Blue-gum (BG); Pine (PN) and Natural forest (NF)) sampled in Umgenipoort Research Facility, in the Natal Midlands of Kwa-Zulu Natal, Table S3: SIMPER analysis results showing the species contributing mostly to the observed differences in assemblage composition in each habitat type sampled in Umgenipoort Research Facility, using the Bray Curtis similarity matrix and a cut off low contributions of 90%. (Av.Abund—Average abundance, Av.Sim—Average similarity, Sim/SD—Similarity/Standard deviation, Contrib%—Contribution%, Cum%—Cumulative%), Table S4: SIMPER analysis results showing the species resulting in the dissimilarities in assemblage composition within the habitat types sampled in Umgenipoort Research Facility, using the Bray Curtis similarity and a cut off low contributions of 90%. (Av.Abund—Average abundance, Av.Sim—Average similarity, Diss/SD—Dissimilarity/Standard deviation, Contrib%—Contribution%, Cum%—Cumulative%).

Author Contributions

T.C.M. designed and conceptualized the study; T.A.M. and T.C.M. collected the data; T.A.M. analysed the data and led writing, under supervision by T.C.M. and T.C.M. was responsible for funding acquisition. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Oppenheimer Generations Research and Conservation and the National Research Foundation, Grant number 114416 to TC Munyai.

Institutional Review Board Statement

Permission to sample ants in the study site was approved by Oppenheimer Generations Research and Conservation.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data used in the current study are available in Table S2.

Acknowledgments

We would like to convey our appreciation to the Umgenipoort Research Facility owners for granting access to the study area, in particular Thulani Mnguni and his staff. We are more than grateful to Nkululeko Mbanjwa, Luyanda Hlamaphi, Lindiwe Khoza and, in particular, Nokubonga Thabethe, who helped us both in the lab and the field.

Conflicts of Interest

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

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Figure 1. Location of the study area (University of KwaZulu-Natal Umgenipoort Research Facility) in the Natal Midlands of KwaZulu-Natal province in South Africa.
Figure 1. Location of the study area (University of KwaZulu-Natal Umgenipoort Research Facility) in the Natal Midlands of KwaZulu-Natal province in South Africa.
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Figure 2. Sample coverage for species diversity of the sampled habitat types at Umgenipoort Research Facility.
Figure 2. Sample coverage for species diversity of the sampled habitat types at Umgenipoort Research Facility.
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Figure 3. Boxplots representing ant species richness across the three habitat types (Blue gum, Natural forest, and Pine plantations) sampled at Umgenipoort Research Facility.
Figure 3. Boxplots representing ant species richness across the three habitat types (Blue gum, Natural forest, and Pine plantations) sampled at Umgenipoort Research Facility.
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Figure 4. Non-metric multidimensional scaling (NMDS) plot showing ant assemblage composition across all the three habitat types with 20 replicates in total. The pine plantation (PN2) replicate was excluded from the NMDS analysis as it did not contain any ants. The data were square root transformed and based on the Bray–Curtis dissimilarity measurement, with a stress value of 0.14.
Figure 4. Non-metric multidimensional scaling (NMDS) plot showing ant assemblage composition across all the three habitat types with 20 replicates in total. The pine plantation (PN2) replicate was excluded from the NMDS analysis as it did not contain any ants. The data were square root transformed and based on the Bray–Curtis dissimilarity measurement, with a stress value of 0.14.
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Table
Table 1. Observed number of species (Sobs), species occurrence, and sample coverage values of the habitat types sampled in Umgenipoort Research Facility. Species occurrence represents frequency of the number of individuals collected and sample coverage values depict whether the specimens collected were representative of the habitat type.
Table 1. Observed number of species (Sobs), species occurrence, and sample coverage values of the habitat types sampled in Umgenipoort Research Facility. Species occurrence represents frequency of the number of individuals collected and sample coverage values depict whether the specimens collected were representative of the habitat type.
Habitat TypesSobsSpecies OccurrenceSample Coverage
Blue gum19440.967
Natural forest14270.950
Pine14290.931
Table
Table 2. Mean and standard deviation of ant species richness, Shannon–Weiner diversity indices, species evenness, and true diversity, given as the effective number of species, in all the sampled habitat types at Umgenipoort Research Facility. The effective number of species represents the conversion of the Shannon–Weiner diversity index into the actual species diversity value in the community [36].
Table 2. Mean and standard deviation of ant species richness, Shannon–Weiner diversity indices, species evenness, and true diversity, given as the effective number of species, in all the sampled habitat types at Umgenipoort Research Facility. The effective number of species represents the conversion of the Shannon–Weiner diversity index into the actual species diversity value in the community [36].
Habitat TypeSpecies Richness ± SD Shannon–Wiener Diversity Index (H’)EvennessEffective Number of Species
Blue gum6.29 ± 1.382.380.5711
Natural Forest3.86 ± 1.771.960.517
Pine4.14 ± 3.582.310.7210
Table
Table 3. Pairwise ANOSIM summaries comparing ant assemblages sampled across the three habitat types in Umgenipoort Research Facility. The R statistic value close to one represents dissimilarity between the habitat types, while an R statistic value close zero depicts that the habitat types were similar in assemblage composition [38]. The significance level shows the degree of similarity across the habitat types.
Table 3. Pairwise ANOSIM summaries comparing ant assemblages sampled across the three habitat types in Umgenipoort Research Facility. The R statistic value close to one represents dissimilarity between the habitat types, while an R statistic value close zero depicts that the habitat types were similar in assemblage composition [38]. The significance level shows the degree of similarity across the habitat types.
GroupsR StatisticSignificance Level
Blue gum, Natural forest0.110.13
Blue gum, Pine0.170.06
Natural forest, Pine0.140.08
Table
Table 4. SIMPER results showing the species that contributed the most to distinguishing the habitat types at Umgenipoort Research Facility (BG—Blue gum, PN—Pine, NF—Natural forest). Ratio: Dissimilarity/Standard deviation.
Table 4. SIMPER results showing the species that contributed the most to distinguishing the habitat types at Umgenipoort Research Facility (BG—Blue gum, PN—Pine, NF—Natural forest). Ratio: Dissimilarity/Standard deviation.
Habitat Type CombinationsSpeciesDiss/SD Ratio
BG & NFHypoponera UKZN_030.77
Lepisiota UKZN_08 (crinita gp.)0.77
BG & PNTetramorium UKZN_03 (setigerum gp.)0.99
Monomorium UKZN_100.97
NF & PNSolenopsis UKZN_030.98
Monomorium UKZN_100.91
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Mthimunye, T.A.; Munyai, T.C. Can Monoculture Timber Plantations Conserve More Ant Communities Than Adjacent Natural Forests? Diversity 2022, 14, 430. https://doi.org/10.3390/d14060430

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Mthimunye TA, Munyai TC. Can Monoculture Timber Plantations Conserve More Ant Communities Than Adjacent Natural Forests? Diversity. 2022; 14(6):430. https://doi.org/10.3390/d14060430

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Mthimunye, Thembekile A., and Thinandavha C. Munyai. 2022. "Can Monoculture Timber Plantations Conserve More Ant Communities Than Adjacent Natural Forests?" Diversity 14, no. 6: 430. https://doi.org/10.3390/d14060430

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