3- https://doi.org/10.18474/jes21-58
Diversity and Seasonal Occurrence of Native and Nonnative Ants (Hymenoptera: Formicidae) in Long-Term Experimental Chinese Privet (Lamiales: Oleaceae) Plots in Georgia, USA
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Chinese privet (Ligustrum sinense Loureiro) (Oleaceae) is a shade-tolerant invasive shrub first introduced from China into the US in the mid-19th Century as an ornamental (Wyman 1973, Shrubs and Vines for American Gardens, Macmillan, NY). Chinese privet is an aggressive invader across the southeastern United States and is now found in 27 U.S. states, including Hawaii (EDDMapS, http://www.eddmaps.org/; 20 May 2021), resulting in loss of native species richness across much of its invaded range (Hanula et al. 2009, Invas. Plant Sci. Manag. 2: 292–300; Hudson et al. 2014, Forest Ecol. Manag. 324: 101–108; Merriam and Feil 2003, Biol. Invasions 4: 369–373; Wilcox and Beck 2007, Southeast. Nat. 6: 535–550). Ward (2002, Southeast Geogr. 1: 29–48) documented an 8% increase in Chinese privet cover in the Upper Oconee River floodplain in northern Georgia between 1951 and 1999.Where Chinese privet establishes, it can dominate as an understory monoculture (e.g., Wilcox and Beck 2007), reducing flowering plant richness needed to support pollinators and, over the long term, likely reducing woody debris diversity necessary as harborage and food for a number of arthropods. Several studies have investigated these impacts of Chinese privet infestation on various taxa, including arthropod communities, with most reporting similarly negative results. A more abundant and diverse bee fauna was found on Chinese privet removal plots compared to control (infested) plots 1 and 2 yr after treatment, and again 5 yr after treatment (Hanula and Horn 2011a, Insect. Conserv. Divers. 4: 275–283; Hudson et al. 2013, Biol. Conserv. 167: 355–362). In a later study on bees at the same study site, Ulyshen et al. (2020, Forest Sci. 66: 416–423) placed traps at 0.5, 5, and 15 m above the forest floor. Bee abundance and diversity were higher near the forest floor in plots where Chinese privet was removed, but similar among plots in the elevated traps. Likewise, beetle richness was increased near ground level after Chinese privet removal in the same experimental plots (Ulyshen et al. 2010, Biol. Invasions 12:1573–1579). In another study, butterfly abundance increased after Chinese privet removal, although richness and evenness did not differ between treatments (Hanula and Horn 2011b, For. Ecol. Manage. 262: 674–680).Ants (Hymenoptera: Formicidae) are abundant and ecologically important arthropods—turning and aerating soil, dispersing seeds, playing a major role in food webs, and serving as environmental indicators and ecosystem engineers (Jones et al. 1994, Oikos 69: 373–386; Folgarait 1998, Biodivers. Conserv. 7: 1221–1244). As such, understanding the effects of Chinese privet and other invasive plants on ant communities is an imperative area of invasion biology research. Many ants are highly successful invasive species, transported around the globe via commerce and other human activity (McGlynn 2002, J. Biogeo. 26: 535–548). Both native and nonnative ants inhabit Georgia forests where Chinese privet occurs. In this paper, we present data on ant diversity and seasonal occurrence in experimental plots with and without Chinese privet, as well as in areas with no history of extensive Chinese privet infestation, reporting on native and nonnative ants in our study sites in northern Georgia.Experimental Chinese privet removal plots were established in four locations in northern Georgia within the Oconee River watershed in October–November 2005 as detailed in Hanula et al. (2009). Sites included Sandy Creek Nature Center north of Athens, GA (Sandy Creek); the Georgia State Botanical Gardens south of Athens (Botanical Garden); the Scull Shoals Experimental Forest in the Oconee National Forest (Scull Shoals); and the University of Georgia Warnell School of Forest Resources Watson Springs Forest (Watson Springs). Briefly, treatments consisted of hand-felling, mechanical removal (mulching with a Gyrotrac® mulching machine) (Klepac et al. 2007, USDA. For. Serv. Southern Res. Sta. Res. Paper SRS43), and no treatment (control). Hand-felling and mechanical removal treatments were followed by herbicide application to stumps and, in 2006, to sprouts, seedlings, and saplings. By 2007, virtually all privet had been removed from the hand-felling and mechanical removal plots, and in 2012 reinfestation of treated plots was minimal (3% and 7% in hand-felling and mechanical removal plots, respectively) (Hudson 2013, Effects of removing Chinese privet (Ligustrum sinense) on plant communities, pollinator communities, and tree growth in riparian forests five years after removal with mechanisms of reinvasion. MS Thesis, Univ. Georgia, Athens). Three additional “desired future condition” plots (riparian hardwood forest with little or no Chinese privet) were established in the Oconee National Forest: one near the Apalachee River (Apalachee) (Greene Co., GA); one near Harris Creek (Harris) (Greene Co., GA), and one near Falling Creek (Falling) (Oglethorpe Co., GA).Ground-dwelling arthropods were sampled using pitfall traps operated for 7-d periods seven times (March, April, May, June, July, August, and October) during 2006, 2007, and 2011. The pitfall traps consisted of a 480-ml plastic cup buried to ground level. A small funnel (8.4-cm diameter) was inserted into the cup and directed crawling insects into a 120-ml specimen cup below. The cup was placed at the intersection of two, 1-m long drift fences and the specimen cup filled with a soap and NaCl-formaldehyde solution (New and Hanula 1998, South. J. Appl. For. 22: 175–183) as a preservative. We used five pitfall traps per plot, each being placed within a subplot. Subplots were located at the plot center and half the distance from the center to each plot corner. Trap samples for each plot were combined into one collective sample per plot and stored in 70% alcohol until they were sorted and identified. Ants were identified using published keys. For the 2006 and 2007 samples, ants were sorted and identified to genus only. Those samples subsequently degraded and were eventually lost. Ants from the 2011 samples were identified to species, and vouchers deposited at the Mississippi Entomological Museum, Mississippi State, MS.We tested for possible treatment effects on ant richness (for ant genera in 2006 and 2007 samples and for species in 2011 samples) using rarefaction and extrapolation with Hill numbers (Chao et al. 2014, Ecol. Monogr. 84: 45–67) using iNEXT Online (Chao et al. 2016, iNEXT (iNterpolation and EXTrapolation, http://chao.stat.nthu.edu.tw/wordpress/software_download/, 1 June 2021]). Because ants are colonial organisms and pitfall catch can be heavily influenced by proximity to nests, we used sampling-unit-based incidence data rather than abundance data (Gotelli et al. 2011, Myrmecol. News 15: 13–19). We set q = 0 to yield species richness, specified an endpoint of 206, and accepted default values for number of knots (40), bootstraps (50), and confidence interval (95%). For species-level 2011 data, we also set q = 1 to yield Shannon diversity using the same parameters.To compare ant communities among the three treatments and the desired condition plots, using species-level data from 2011 we performed nonmetric multidimensional scaling (NMS) using PC-ORD (McCune and Mefford 2010, PC-ORD v. 6.0. MjM Software, Gleneden Beach, OR). We used the Jaccard distance measure on presence–absence data for this analysis. We used the same presence–absence matrix and distance measure to perform a multiresponse permutation procedure (MRPP) to test for differences between treatments. Finally, to test for associations between ant taxa and one or more treatments, we performed indicator species analysis in R using the package “indicspecies” (De Cáceres et al. 2010, Oikos 119: 1674–1684). We used the function multipatt (multilevel pattern analysis) to conduct this analysis, using 9,999 permutations to calculate P-values for each combination. The resulting indicator values range from 0 to 1 (no association to complete association).Lastly, we subjected the four most abundant species to analysis of variance using log-transformed data (logX + 1) to test for treatment effects on those species. Site was used as a blocking factor, and we tested for effects of treatment and date using the F-statistic.We collected and identified 50 species of ants from the pitfalls (Table 1), including the invasive Asian needle ant, Brachyponera chinensis (Emery). While only present at five of the seven sites, Asian needle ant was greater than 4× more abundant than the next-most commonly collected species, Lasius americanus Emery. Asian needle ant was most abundant in the Botanical Gardens control plot, where it was captured in increasing numbers throughout the season (2, 15, 12, 125, 511, 1,000+, and 1,000+ for March, April, May, June, July, August, and October, respectively). When Asian needle ant numbers exceeded 1,000 in a sample, counting of individual ants was stopped. Zungoli and Benson (2008, Pp. 51–57, In Robinson and Bajomi [eds.], Proc. 6th Intern. Conf. Urban Pests, Budapest, Hungary) observed peak worker activity in August, followed by a decline in September and inconsistent activity in October. We do not have exact numbers for August and October, but clearly foraging activity and/or the number of available foragers in colonies increases in this species later in the season.For ant genera identified in 2006 and 2007 (1 and 2 yr after treatment, respectively) there were no significant differences in ant diversity among the treatments. The 95% confidence intervals for extrapolated species richness data (q = 0) from 2011 overlapped among treatments, but 95% confidence intervals for desired future condition plots diverged from control and mulched plots using extrapolated Shannon diversity (q = 1) (Fig. 1). There was an overall trend toward increased ant diversity in desired condition plots in 2007 and 2011. Mean species richness for all years and treatments is presented in Table 2.Our NMS analysis yielded a three-dimensional solution with a final stress of 8.29. The desired plots form a distinct cluster within the ordination space, suggesting a relatively distinct ant community, while there is considerable overlap among the three other treatments (Fig. 2). Based on MRPP, there was a marginally significant difference in community composition among treatments (T = –1.38, P = 0.09). Pairwise comparisons reveal that the ant communities in the desired plots differed significantly from those in the control (T = –2.26, P = 0.03) and chainsaw (T = –1.57, P = 0.05) plots. No other pairwise comparison was significant. Indicator species analysis found four ant species to be significantly associated with the desired plots, with one of them also associated with the control plots (Table 3). The first species, Nylanderia vividula Nylander (“Nylander's crazy ant”) is an indoor pest in many situations, widely distributed throughout the U.S. Gulf Coast states. Pseudomyrmex ejectus (Smith) nests in dead twigs and stalks of herbaceous plants. Solenopsis carolinensis Forel is a common thief ant in forests in the southeastern United States and is known to nest in the bark of pine trees (J.A.M., pers. obs.). Strumigenys louisianae Roger is widespread and is a specialized predator on collembola (Wilson 1953, Ann. Entomol. Soc. Am. 46: 479–495). It is thought to be the only native species in the genus. It cannot be determined from our data if these species-level patterns were driven by differences in privet invasion history or by other factors affecting ant distribution across our sampling area.Analysis of variance results for the four most abundant species varied. Brachyponera chinensis catches were related to site, and site × date × treatment (F = 4.75; df = 4, 79; P = 0.002; and F = 7.52, df = 2, 70, P = 0.001, respectively), with more being captured late in the season and a single control plot at the Botanical Gardens yielding thousands of individuals compared to 0–13 in all other plots. For Crematogaster ashmeadi, site, site × date, and site × date × treatment were all significant (F= 3.12, df = 4, 79, P= 0.021; F= 2.56, df = 7, 72, P= 0.021; F = 18.8, df = 2, 70, and P < 0.001, respectively). Fewer C. ashmeadi were collected at the Botanical Gardens site than the other sites, and seasonal activity was highest June–August, although they were collected on all sampling dates. More C. ashmeadi were collected in mulched (7.4 ±1.9) (x̄ ± SE) and chainsaw (2.29 ± 0.65) plots than in controls (1.25 ± 0.36). There were no significant treatment effects noted for L. americanus or Aphaenogaster carolinensis Wheeler.Although a few species with specialized nesting habits were collected in this study (e.g., arboreal species, twig and cavity nesting species), the majority of ant species collected are known to nest in soil, under debris, and/or in decaying wood. Plots where Chinese privet was hand-felled may have offered more nesting sites for some ant species for a limited time after treatment. Differences in pitfall catches for individual species suggest that dense populations of Chinese privet may favor (B. chinensis) or suppress (C. ashmeadi) some ants; however, these results should be interpreted cautiously given the potential local variation in pitfall traps with respect to nest proximity. Regardless, presence of Chinese privet did not appear to impact our measures of ant diversity relative to the removal treatments. Species contributing to increased diversity in desired condition plots included myrmicine species in the specialized predator genus Strumigenys and the uncommonly collected myrmicine Aphaenogaster mariae Forel, an arboreal species that has usually been collected from the trunks of live trees using bait (DeMarco 2015, Phylogeny of North American Aphaenogaster species [Hymenoptera: Formicidae] reconstructed with morphological and DNA data. PhD Dissertation. Michigan State Univ., East Lansing).Ant sampling is biased by sampling method, with pitfall traps generally collecting fewer species than more-targeted methods such as hand-collecting in quadrats (Gotelli et al. 2011, Myrmecol. News 15: 13–19; Salata et al. 2020, Biodiv. Conserv. 29: 3031–3050 and references therein). Collections at the Sandy Creek site in 2011–2012 using a modified Winkler litter extraction method captured >47 ant species (D. Booher, pers. comm.), whereas we collected and identified 31 species at Sandy Creek in this study; our results are somewhat limited in contrast to more-exhaustive collecting methods. Long-term studies with multiple collection methods would be informative in terms of ant communities in restored areas where Chinese privet has been removed versus similar, undisturbed areas with no or little history of Chinese privet infestation, and in Chinese privet-infested controls. Understory plant cover in both privet removal treatments and desired condition plots was similar (∼40–60%) 2 yr after treatment, but the plant communities in desired condition plots were highly dissimilar to both controls and privet removal treatments (Hanula et al. 2009) with early successional species abundant in the treated plots. Plants may provide ants with vegetative matter for foraging, food bodies, nesting sites, nectar, and eliasomes (Beattie and Hughes 2002, Pp. 211–235. In Herrera and Pellmyr [eds.], Plant-Animal Interactions: An Evolutionary Approach, Blackwell Science, Oxford, U.K.), and higher diversity of plants in desired condition plots may support a more diverse ant population. As pointed out by Hanula et al. (2009), it is likely that Chinese privet suppression may be required for long periods of time, or that active understory restoration may be necessary, to realize understory and forest conditions similar to areas with no history of Chinese privet. The same is likely true for arthropod groups such as ants that interact with shrubs and forbs in the understory.We thank Doug Booher, Timothy Menzel, and two anonymous reviewers for many helpful comments on the manuscript and Frank Roesch for statistical expertise. This work was funded by USDA Forest Service Research and Development. The findings and conclusions in this publication are those of the authors and should not be construed to represent any official USDA or U.S. Government determination or policy.
- Research Article
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- 10.1016/j.foreco.2014.04.013
- May 10, 2014
- Forest Ecology and Management
Impacts of removing Chinese privet from riparian forests on plant communities and tree growth five years later
- Research Article
- 41
- 10.1016/j.biocon.2013.09.001
- Sep 28, 2013
- Biological Conservation
Removing Chinese privet from riparian forests still benefits pollinators five years later
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- 67
- 10.1016/j.foreco.2011.04.040
- May 24, 2011
- Forest Ecology and Management
Removing an exotic shrub from riparian forests increases butterfly abundance and diversity
- Research Article
- 95
- 10.1111/j.1523-1739.2008.01040.x
- Jan 14, 2009
- Conservation Biology
Research that connects the effects of urbanization on biodiversity and ecosystem services is lacking. Ants perform multifarious ecological functions that stabilize ecosystems and contribute to a number of ecosystem services. We studied responses of ant communities to urbanization in the Lake Tahoe basin by sampling sites along a gradient of urban land development. We sampled ant communities, measured vegetation characteristics, quantified human activities, and evaluated ant-community responses by grouping ants into service-providing units (SPUs), defined as a group of organisms and their populations that perform specific ecosystem services, to provide an understanding of urbanization impacts on biodiversity and their delivery of ecosystem services. Species richness and abundance peaked at intermediate levels of urban development, as did the richness of 3 types of ant SPUs (aerators, decomposers, and compilers). With increasing land development aerator and decomposer ants significantly declined in abundance, whereas compiler ants significantly increased in abundance. Competing models demonstrated that precipitation was frequently among the strongest influences on ant community structure; however, urban development and human activities also had a strong, negative influence on ants, appearing in most models with DeltaAIC(c) < 2 for species richness and abundance patterns of SPUs and generalists. Response diversity was observed within SPUs, which suggests that the corresponding ecosystem services were maintained until development reached 30-40%. Our data provide evidence that ecosystem functions, such as water infiltration and soil productivity, may be diminished at sites subject to greater levels of urbanization and that conserving ant communities and the ecosystem services they provide could be an important target in land-use planning and conservation efforts.
- Research Article
- 579
- 10.1890/0012-9658(1999)080[0238:cmutdo]2.0.co;2
- Jan 1, 1999
- Ecology
COMPETITIVE MECHANISMS UNDERLYING THE DISPLACEMENT OF NATIVE ANTS BY THE INVASIVE ARGENTINE ANT
- Research Article
- 103
- 10.2307/176993
- Jan 1, 1999
- Ecology
Competitive Mechanisms Underlying the Displacement of Native Ants by the Invasive Argentine Ant
- Research Article
- 8
- 10.1002/ecs2.2344
- Jul 1, 2018
- Ecosphere
Human activities are increasing the size, frequency, and severity of disturbance across earth's ecosystems including deserts. Ants are important drivers of ecosystem function and are good bioindicators of ecosystem sensitivity to disturbance and change. Rodents also play an important role in ecosystem response to disturbance and often compete with ants for resources. The purpose of our study was to test the main and interactive effects of fire, rodent activity, and time on ant forager abundance, species richness, and diversity, as well as changes in ant mound density and disk area in the Great Basin Desert. We experimentally applied burn and rodent exclusion treatments and used pitfall traps to collect ants each month from April through October from 2014 to 2016. Over the three‐year period, burned areas had lower richness and diversity than unburned areas. Rodent exclusion had minimal effects on the ant community, and there was not a significant rodent exclusion interaction with fire. Treatment effects varied by month and year. The western harvester ant, Pogonomyrmex occidentalis, was the most abundant ant species, comprising about 70% of the total ants captured. Shifts in ant diversity following fire were driven by positive responses of harvester ants to burned habitat conditions. In contrast, all other ant species when analyzed together had lower forager abundance in burned plots, which drove lower ant diversity in burned plots. Ant forager abundance, richness, and diversity increased each year of the study in all plots; however, richness and diversity remained lower in burned areas than in unburned areas each year. Structural equation modeling shows that the effects of fire on ant community diversity are partially mediated through the plant community. While rodents affected the plant community, those effects do not seem to transfer over to the ant community. Pogonomyrmex occidentalis mound density was higher in burned areas, but disk area was smaller. Our results suggest that fire has adverse effects on ant community diversity. This could have long‐lasting effects on ecosystem function in the face of a changing fire regime in deserts of North America caused by invasive annual plants.
- Research Article
- 14
- 10.3389/fevo.2022.832268
- Feb 22, 2022
- Frontiers in Ecology and Evolution
Invasive non-native woody shrubs pose a major threat to forested ecosystems in many parts of the world and there is an urgent need for research on the restoration and recovery of these areas. We studied patterns of tree growth and regeneration 13 years after the experimental eradication (by chainsaw or mulching machine followed by herbicide treatments) ofLigustrum sinenseLour. (Chinese privet) from riparian forests in Georgia, United States. We also followed the recovery of bee and butterfly populations using sites with no history of privet invasion as a reference. By the end of the study, the basal area of restored plots was 24% greater, on average, than still-invaded control plots. Because tree growth rates did not differ among treatments, this increase is attributable to the 60% increase in the number of regenerating native stems (dominated byAcer negundoL.) following privet removal. The benefits of privet removal on pollinators were immediate and long-lasting with the richness and abundance of bees and butterflies being consistently higher in restored plots than in control plots. The diversity, abundance, and composition of bees in restored and reference (i.e., never invaded) plots were comparable by the end of the study. This was less true for butterflies, however, possibly due to the legacy effects of privet invasion on plant communities. Our results demonstrate the long-term benefits of removing privet on forest regeneration and pollinator communities. Indeed, without such efforts, it is probable that forest cover will gradually thin and ultimately disappear from privet-invaded areas as overstory trees die without replacement.
- Research Article
- 50
- 10.1007/s10530-009-9569-2
- Sep 3, 2009
- Biological Invasions
Chinese privet (Ligustrum sinense Lour.), an invasive shrub from Asia, is well established in the southeastern United States where it dominates many floodplain forests. We used flight intercept traps to sample beetles at three heights (0.5, 5 and 15 m) in ~2 ha plots in which L. sinense had (by chainsaws or mulching machine) or had not been removed from forests in northeastern Georgia. Removing L. sinense, particularly by machine, increased the richness and diversity of beetles and affected composition near the ground (0.5 m) but not in the forest canopy (15 m). There were no differences among treatments above the L. sinense canopy (5 m) aside from Xylosandrus crassiusculus, an exotic ambrosia beetle from Asia, dominating the beetle community at that height in control plots. Removing the L. sinense layer greatly increased beetle richness near the ground, resulting in vertical distribution patterns more similar to those observed in areas of forest devoid of L. sinense. We suspect that even organisms in the canopy will benefit from privet removal in the long term given that tree regeneration is nearly impossible in forests in which L. sinense has become well established.
- Research Article
- 16
- 10.1016/j.biocon.2015.04.012
- May 15, 2015
- Biological Conservation
The fire ant Solenopsis saevissima and habitat disturbance alter ant communities
- Research Article
- 10.1007/s11252-025-01895-0
- Jan 16, 2026
- Urban Ecosystems
Urbanization is a major threat to global biodiversity because it alters environmental conditions at both local and landscape scales. As urbanization accelerates, understanding its effects on biodiversity has become increasingly important. Ants play key ecological roles and are reliable bioindicators, making them useful models for assessing biodiversity responses in cities. The aim of this study was to investigate how ant communities in urban squares are affected by local site characteristics of the squares and by their surrounding landscapes in Rio de Janeiro, Brazil. Ant diversity (Hill numbers) was calculated for different groups of ant species: all native, native arboreal, native leaf-litter and non-native species. To investigate the effects of local and landscape characteristics on ants, an information-theoretic model selection framework was employed. Results indicate that ant diversity in urban squares is structured by environmental filters operating at multiple spatial scales. Local vegetation structure emerged as a strong filter: canopy cover had a consistently positive effect on native ant diversity in all evaluated groups. Additionally, the surrounding landscape played a key role in shaping ant diversity in urban squares: urban cover had a negative effect on native arboreal and leaf-litter ants but also on non-natives, forest cover had a positive effect on native arboreal and non-native ants and forest fragmentation had a positive effect on total and arboreal native ant diversity. These findings suggest that ant diversity in urban squares can be enhanced by increasing canopy cover and the amount of urban green spaces interspersed among built-up areas in the city.
- Research Article
- 69
- 10.1111/j.1752-4598.2011.00131.x
- Jan 27, 2011
- Insect Conservation and Diversity
Abstract. 1. Chinese privet ( Ligustrum sinense Lour.) was removed from riparian forests in the Piedmont of Georgia in November 2005 by mulching with a track‐mounted mulching machine or by chainsaw felling. The remaining privet in the herbaceous layer was killed with herbicide in December 2006. 2. Bee (Hymentoptera: Apoidea) abundance, diversity and community similarity in the forests were measured for 2 years after shrub removal and compared with heavily invaded controls and with non‐invaded forests (desired future condition) using pan traps. 3. In 2006, control plots averaged 8.8 species and 34.8 bees per plot. Privet mulching resulted in 32.5 bee species and 418.3 bees per plot, and privet felling plots had 29 species and 259 bees per plot. In 2007, control plots averaged only10 species per plot and 32.8 bees per plot, while mulched and felled plots had 48 and 38 species per plot and 658.2 and 382.5 bees per plot, respectively. 4. The bee community on untreated control plots was dissimilar from the communities on privet felling, mulched and desired future condition plots during both years; however, by 2007, desired future condition, felling and mulched plots had similar bee communities. 5. Removal of an invasive shrub provided immediate benefits for native pollinators and resulted in bee communities similar to non‐invaded forests even without further restoration of native plant communities.
- Dissertation
- 1
- 10.53846/goediss-5649
- Feb 21, 2022
- eDiss (Georg-August-Universität Göttingen)
Land-use change due to agricultural expansion is one of the greatest global threats to biodiversity and associated ecosystem functions and services. In the tropics in particular, conversion of forest and agroforests into monoculture agriculture such as oil palm is happening at an extremely rapid rate, leading to highly simplified landscapes. In Indonesia, currently the world’s leading palm oil producer, oil palm plantation crop cover was nine million hectares in 2010 with a projected increase to 18 million hectares by 2020. The predicted further large-scale expansion of oil palm plantations and other high-intensity agricultural systems has extensive implications for biodiversity loss. In agricultural production systems, loss of economically important functional groups can lead to decreases in essential ecosystem services such as pollination, biocontrol and soil turnover. Ants for example, dominate terrestrial biomass and are important for number of ecosystem services that are crucial in agriculture and have been shown to influence yield. In this thesis I aim to understand 1) how ant communities respond to land-use change, 2) if certain factors can alter their response, and 3) if changes in the ant community can alter their influence on biodiversity, ecosystem functions and yield. \nIn chapter 2 and 3 of this thesis I investigated land-use change effects on the taxonomic and functional diversity of ant communities in lowland forest, jungle rubber, monoculture rubber and oil palm plantation sites. In chapter 2 I focus on changes in species richness and composition and in chapter 3 changes in functional diversity and composition, including also birds and leaf-litter invertebrates in the analysis to broaden the study. The results show that ant species richness responded contrary to expected to land-use change, either increasing or not changing from forest to the agricultural systems studied dependent on the sampling methods used. However, species composition changed considerably and few ant species were shared among different land-use types. These results suggest land-use change would result in a net loss of ant species, even though ant species richness in plantations and forested habitats are similar. Furthermore, there was a linear relationship between species richness and functional diversity for ants, birds and leaf-litter invertebrates, indicating low redundancy in these systems. Finally, the functional composition of all three animal groups also changed with land-change. In particular, species from higher trophic guilds decreased from forest to oil palm. The observed decrease changes in species composition from rainforest to monoculture plantations, along with the tightly coupled decreases in functional diversity and low functional redundancy, could threaten long-term ecosystem stability through potential consequences for ecosystem processes \nThe results from chapter 2 and 3 provide strong evidence that overall impacts of conversion from natural ecosystems to land-use systems on ant communities are negative. However, there are factors which can influence the severity of these impacts. Therefore, in chapter 4 and 5 I investigate the response of ant communities and associated functions to landscape context and local management in oil palm plantations. In chapter 4 I examined the effects of location within the plantation (edge vs centre) and local characteristics (epiphyte cover, herbicide use, and local microclimate) on ant and other arthropod communities and litter decomposition in oil palm leaf axils. Arthropod abundance and taxa richness were higher at the edge of plantations than in the centre. Moreover, organic matter mass and height of the leaf axil were more important for arthropod communities and decomposition rate than epiphyte or ground vegetation cover. In chapter 5 I investigated the effect of surrounding landscape and distance from the edge on predation rates and predator occurrences in oil palm plantations. Predation rates were ~70% higher in non-oil palm habitat. This effect spilled over into the oil palm plantations, where predation increased by 55-100% 20 m from the edge of the plantation and by 40-55% 50 m from the edge when surrounded by a land-use other than oil palm. Taken together, chapters 4 and 5 show that oil palm plantations adjacent to different land-use systems have enhanced biodiversity and associated functioning, though this effect quickly declines with distance from the edge. Furthermore, local management of ground cover has mixed effects on arthropods and epiphyte management is unlikely to influence ant communities. \nIn chapter 6 and 7 I look further into the changes in ant communities shown in Chapter 1 and 2 by investigating the role of ant communities in shaping arthropod communities and associated ecosystem functions and services. In chapter 6 I studied the influence of ants on both above- and belowground invertebrate communities, soil and litter variables and decomposition across different land-use systems using ant suppression plots at forest, jungle rubber, rubber and oil palm sites. Belowground invertebrates, i.e. collembola, had 30% lower biomass in ant suppression plots. However, soil and litter variables and above-ground invertebrates were mostly unaffected. Rather, differences in local conditions between the four studies land-use systems were generally the most important predictors. Most notably, effects on decomposition rates were context-dependent, whereby ant suppression reduced decomposition in the forest sites only. Therefore, differences in ant communities between land-use systems alter their relationship to decomposition processes, however, the underlying drivers of these effects require further investigation. In chapter 7 I manipulated ant as well as flying vertebrate (birds and bats) access in only oil palm sites and measured effects on arthropod communities, related ecosystem functions (herbivory, predation, decomposition and pollination) and crop yield. Non-ant arthropod predator populations increased in response to reductions in ant and bird access, and the net effect of experimental manipulations on ecosystem functioning was minimal. Similarly, effects on yield were not significant. Chapter 7 shows that ecosystem functions and productivity in oil palm are, under current levels of pest pressure and pollinator populations, robust to large changes in the communities of major predator groups. \nIn conclusion, although forest conversion to oil palm and other agricultural systems in Indonesia has wide-ranging negative influences on biodiversity and function, there is the opportunity to enrich biodiversity in these systems. In oil palm plantations in particular this should be encouraged as changes in biodiversity do not compromise production.
- Research Article
- 69
- 10.1111/j.1744-7429.2010.00662.x
- Jun 9, 2010
- Biotropica
Invasions by introduced ant species can be ecologically destructive and affect a wide range of taxa, particularly native ants. Invasive ant species often numerically dominate ant communities and outperform native ant species in effective resource acquisition. Here, we describe interactions between the invasive ant Anoplolepis gracilipes (Smith) and resident ant species in disturbed habitats in NE Borneo. We measured interference competition abilities of A. gracilipes by performing arena bioassays between two A. gracilipes colonies and seven local ant species, and measured its effective resource competition at baits within supercolonies and at supercolony boundaries. Furthermore, we compared ant species diversity and composition at baits among (A) core areas of A. gracilipes supercolonies, (B) supercolony boundaries and (C) outside supercolonies. Anoplolepis gracilipes was behaviorally dominant over most ant species except Oecophylla smaragdina. Within supercolonies, A. gracilipes discovered all food baits first, and monopolized the vast majority throughout the course of the experiment. At supercolony boundaries, A. gracilipes discovered baits later than resident ant species, but subsequently monopolized half of the baits. Furthermore, the activity and diversity of the ant community within A. gracilipes supercolonies was lower than at its boundaries and outside supercolonies, and the ant communities differed significantly between infested and noninfested areas. Our study supports the hypothesis that successful establishment of A. gracilipes in anthropogenically disturbed habitats may negatively affect resident ant communities through high levels of direct interspecific aggression and almost complete monopolization of resources within high-density supercolonies.
- Research Article
- 74
- 10.1614/ipsm-09-028.1
- Oct 1, 2009
- Invasive Plant Science and Management
Chinese privet is a major invasive shrub within riparian zones throughout the southeastern United States. We removed privet shrubs from four riparian forests in October 2005 with a Gyrotrac® mulching machine or by hand-felling with chainsaws and machetes to determine how well these treatments controlled privet and how they affected plant community recovery. One year after shrub removal a foliar application of 2% glyphosate was applied to privet remaining in the herbaceous layer. Three “desired-future-condition” plots were also measured to assess how well treatments shifted plant communities toward a desirable outcome. Both methods completely removed privet from the shrub layer without reducing nonprivet shrub cover and diversity below levels on the untreated control plots. Nonprivet plant cover on the mulched plots was > 60% by 2007, similar to the desired-future-condition plots and higher than the hand-felling plots. Both treatments resulted in higher nonprivet plant cover than the untreated controls. Ordination showed that after 2 yr privet removal plots were tightly grouped, suggesting that the two removal techniques resulted in the same plant communities, which were distinctly different from both the untreated controls and the desired-future-condition. Both treatments created open streamside forests usable for recreation and other human activities. However, much longer periods of time or active management of the understory plant communities, or both, will be required to change the forests to typical mature forest plant communities.
