Invasive ant establishment, spread, and management with changing climate

Ants from the tropical dry forest in the Cauca River geographic valley, Colombia: new records and expansion of distributions

Background

Tropical dry forests (TDF) are amongst the most important tropical biomes globally, recognised for their remarkable biodiversity. This biome features a favourable climate and high soil fertility, which has facilitated the development and expansion of human societies. However, continuous and extensive human intervention has led to habitat loss and fragmentation, disrupting the assemblages of biological communities. Within these communities, ants (Hymenoptera, Formicidae) represent one of the predominant groups and their high sensitivity to habitat transformation makes them a useful model for monitoring the effects of land-use changes and assessing ecosystem quality. The objective of this research was to compare ant diversity between two habitat types, tropical dry forest fragments and the surrounding matrices in the Cauca River Valley region. Ants were collected from 2021 to 2022 using six collection methods: arboreal baiting, epigeal baiting, hypogeal baiting, pitfall traps, mini-Winkler extractors and manual capture. A substantial portion of the data generated from this research is available in two datasets associated with two Colombian entomological collections. The first dataset (1574 ant records) is housed at the Centro de Colecciones Biológicas de la Universidad de Magdalena (CBUMAG) and the second (546 records) at the Museo de Entomología de la Universidad del Valle (MUSENUV).

New information

Five ant species were registered for the first time in Colombia: Leptogenysmontuosa Lattke, 2011, Neoponerarugosula Emery, 1902, Neoponerazuparkoi Mackay & Mackay, 2010, Pheidoletraini Wilson, 2003 and Wasmanniasulcaticeps Emery, 1894. Additionally, the distributions of 45 ant species native to two Departments in the Cauca River Valley geographic region (VGRC) have been expanded. Of these, 31 species extended their distribution into the Valle del Cauca Department: Aztecaalfari Emery, 1893, Foreliusdamiani Guerrero & Fernández, 2008, Ecitonmexicanum Roger, 1863, Neivamyrmexemersoni (Wheeler, 1921), Holcoponeramoelleri Forel, 1912, Brachymyrmexmusculus Forel, 1899, Cephalotesporrasi (Wheeler, 1942), Cephalotestargionii (Emery, 1894), Cephalotesumbraculatus (Fabricius, 1804), Crematogastermontezumia Smith, 1858, Crematogasterobscurata Emery, 1895, Nesomyrmexpittieri (Forel, 1899), Octostrumabatesi (Emery, 1894), Octostrumaexcertirugis Longino, 2013, Octostrumaobtusidens Longino, 2013, Pheidolebilimeki Mayr, 1870, Pheidoleboliviana Wilson, 2003, Pheidolecolobopsis Mann, 1916, Pheidolegauthieri Forel, 1901, Pheidolehasticeps Wilson, 2003, Pheidolesimonsi Wilson, 2003, Pheidolesubarmata Mayr, 1884, Pheidolevallifica Forel, 1901, Solenopsisazteca Forel, 1893, Solenopsisbrevicornis Emery, 1888, Strumigenysgrytava (Bolton, 2000), Strumigenysmarginiventris Santschi, 1931, Strumigenyswheeleriana Baroni Urbani, 2007, Temnothoraxsubditivus (Wheeler, 1903), Hypoponeraopacior (Forel, 1893), Leptogenyspubiceps Emery, 1890 and Pseudomyrmexlongior (Forel, 1904). Ten species extended their distribution into the Cauca Department: Aztecavelox Forel, 1899, Brachymyrmexminutus Forel, 1893, Crematogasterevallans Forel, 1907, Megalomyrmexdrifti Kempf, 1961, Pheidolefimbriata Roger, 1863, Pheidolelongiscapa Forel, 1901, Pheidoleradoszkowskii Mayr, 1884 and Rogeriascandens (Mann, 1922); and four species extended their distribution into both Departments: Brachymyrmexcordemoyi Forel, 1895, Pheidolesculptior Forel, 1893, Hypoponerafiebrigiantoniensis (Forel, 1912) and Hypoponeraparva (Forel, 1909). Finally, three exotic species were registered for the first time in the VGRC, extending their distributions within Colombia: Strumigenysemmae (Emery, 1890) in the Valle del Cauca Department and Cardiocondylaemeryi Forel, 1881 and Cardiocondylawroughtonii (Forel, 1890) in the Cauca Department.

Assessing the establishment risk for parthenogenetic populations of Lissorhoptrus oryzophilus in global rice-growing areas and potential economic impact in China

The rice water weevil, Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae), threatens global rice production, with invasion events driven by its parthenogenetic populations. However, the global establishment risk in global rice-growing areas and potential economic losses and control benefits of the populations in invaded areas remain unclear. We applied an optimized MaxEnt model to predict the global suitable areas of the populations under current and future climate scenarios. Furthermore, we used @Risk software to estimate the potential economic losses and controlling benefit of this populations to rice production in China. Compared to its native range (North America), this populations has explored novel climates ecological niches in invaded areas (Europe and Asia) and occupies the broadest range of climatic ecological niches in Asia. The highly suitable area is primarily covered in rice-growing areas in China, the Korean Peninsula, and Japan, with all major rice-growing areas concentrated in these countries and regions. Under SSP1-2.6 and SSP5-8.5 emission scenarios, sum of suitable area for the populations in global rice-growing regions is projected to decrease by 0.35% and 0.26%, respectively, by the 2030s and 2050s. Moreover, @Risk analysis indicates that without control measures, the populations could cost China's rice industry $18.95 billion, but management efforts could recover $17.54 billion. These results provide in-depth reference about the impact of climatic changes on the potential global suitable range of L. oryzophilus parthenogenetic populations and its economic impact on the rice industry in China.

Species Distribution Models Reveal Varying Degrees of Refugia From the Invasive Asian Needle Ant for Native Ants Versus Ant-Plant Seed Dispersal Mutualisms

The Asian Needle Ant, Brachyponera chinensis (Hymenoptera: Formicidae), has spread throughout a substantial portion of the southeastern United States where it has primarily been restricted to low elevations. We focused on the B. chinensis invasion in Great Smoky Mountains National Park (GSMNP). Records in and near the park represent some of the highest elevation locations of B. chinensis in North America. The goals of this study were to characterize the status of the B. chinensis invasion in GSMNP, to assess the role that disturbance and human visitation play in B. chinensis invasion within GSMNP, to identify the potential of B. chinensis to spread into higher elevations in the park and the southern Appalachians and to determine the impact that this might have on native species, including keystone seed-dispersers within the Aphaenogaster rudis complex and their myrmecochorous plants. We surveyed GSMNP for B. chinensis at 45 sites, including sites that were burned during the 2016 Gatlinburg fire, sites with high human visitation, and undisturbed sites. We then built species distribution models (SDMs) for B. chinensis and some of the native species that B. chinensis is most likely to impact. This allowed us to assess the potential for high-elevation refugia within the southern Appalachians. We did not find B. chinensis at any undisturbed sites in GSMNP. We did find B. chinensis at five high-visitation sites. Field findings were consistent with our SDMs, which suggested that GSMNP's unique precipitation regimes may act as a barrier to invasion. Unfortunately, SDMs indicated moderate suitability for B. chinensis across a sizable proportion of the northern border of the park. This is a region where B. chinensis may have disproportionate impacts on myrmecochorous plant species. Thus, although southern Appalachian precipitation and temperature regimes may provide a refuge from B. chinensis at high elevations, this will not protect all species likely to be impacted by this invasive ant.

Occurrence and potential diffusion of pine wilt disease mediated by insect vectors in China under climate change

BACKGROUND

Pine wilt disease (PWD), a major international quarantined forest pest, causes serious ecological and economic damage to Pinus species in Asia and Europe. In China, PWD has spread northeasterly and northwesterly beyond its original northern limits. Consequently, an evaluation of the insect vector-mediated occurrence and potential diffusion of PWD is needed to identify important transmission routes and control the spread of disease.

RESULTS

An optimized MaxEnt model was used to assess the current and future geographical distribution of Bursaphelenchus xylophilus and its insect vectors in China. The predicted suitable area for B. xylophilus colonization is currently 212.32 × 104 km2 and mainly concentrated in Central, East, Southwest and South China, although is anticipated to include the northwestern regions of China in the future. As for the insect vectors, Monochamus alternatus and M. saltuarius are expected to spread toward the northwest and southwest, respectively. The maximum predicted dispersion area of PWD mediated by M. alternatus, M. saltuarius and both species was 91.85 × 104, 218.76 × 104 and 29.99 × 104 km2, respectively, with potential diffusion areas being anticipated to increase in the future. Both the suitable probabilities and areas of B. xylophilus and its insect vectors were found to vary substantially along the latitudinal gradient, with the latitudinal range of these species being predicted to expand in the future.

CONCLUSION

This is the first study to investigate the potential diffusion areas of PWD mediated by insect vectors in China, and our finding will provide a vital theoretical reference and empirical basis for developing more effective management strategies for the control of PWD in China. © 2024 Society of Chemical Industry.

A Host Tree and Its Specialist Insects: Black Locust (Robinia pseudoacacia) Availability Largely Determines the Future Range Dynamics of Its Specialist Insects in Europe

Black locust is the only host of Robinia-specialist insects in Europe. However, no study to date has examined future range shifts of specialist insects, and the relative effects of host plant availability and other factors on their range shifts. Here, we characterized the future range shifts in the host and its four specialist insects and the factors contributing to changes in their ranges. We detected substantial range expansions in all target species. Climate predictors and host plant availability were expected to have the strongest effects on the range shifts in the host and its specialist insects, respectively, suggesting that the specialist insects will track the ranges of their host. Parectopa robiniella showed the largest potential and expanding ranges and should be made a priority species for controlling invasions of Robinia-specialist insects in Europe. The expanding ranges of all specialist species were largely identified in the United Kingdom, Germany, and France, suggesting that these should be priority regions for mitigating their effects on ecosystems. Reducing future climate change is essential for preventing the spreading of specialist insects in Europe since specialist insects track their specialist host plants, and host range expansions are mainly driven by future climate changes.

Risk assessment framework for pine wilt disease: Estimating the introduction pathways and multispecies interactions among the pine wood nematode, its insect vectors, and hosts in China

Pine wilt disease (PWD), caused by the pine wood nematode (PWN, Bursaphelenchus xylophilus), a destructive, invasive forest pathogen, poses a serious threat to global pine forest ecosystems. The global invasion of PWN has been described based on three successive phases, introduction, establishment, and dispersal. Risk assessments of the three successive PWN invasion phases can assist in targeted management efforts. Here, we present a risk assessment framework to evaluate the introduction, establishment, and dispersal risks of PWD in China using network analysis, species distribution models, and niche concepts. We found that >88 % of PWN inspection records were from the United States, South Korea, Japan, Germany, and Mexico, and 94 % of interception records were primarily from the Jiangsu, Shanghai, Shandong, Tianjin, and Zhejiang ports. Based on the nearly current climate, the areas of PWN overlap with its host Pinus species were primarily distributed in southern, eastern, Yangtze River Basin, central, and northeastern China regions. Areas of PWN overlap with its insect vector Monochamus alternatus were primarily distributed in southern, eastern, Yangtze River Basin, central, and northeastern China regions, and those of PWN overlap with the insect vector Monochamus saltuarius were primarily distributed in eastern and northeastern China. The niche between PWN and the insect vector M. alternatus was the most similar (0.68), followed by that between PWN and the insect vector M. saltuarius (0.47). Climate change will increase the suitable probabilities of PWN and its two insect vectors occurring at high latitudes, further increasing their threat to hosts in northeastern China. This risk assessment framework for PWD could be influential in preventing the entry of the PWN and mitigating their establishment and dispersal risks in China. Our study provides substantial clues for developing a framework to improve the risk assessment and surveillance of biological invasions worldwide.

Generalized mutualisms promote range expansion in both plant and ant partners

Mutualism improves organismal fitness, but strong dependence on another species can also limit a species' ability to thrive in a new range if its partner is absent. We assembled a large, global dataset on mutualistic traits and species ranges to investigate how multiple plant-animal and plant-microbe mutualisms affect the spread of legumes and ants to novel ranges. We found that generalized mutualisms increase the likelihood that a species establishes and thrives beyond its native range, whereas specialized mutualisms either do not affect or reduce non-native spread. This pattern held in both legumes and ants, indicating that specificity between mutualistic partners is a key determinant of ecological success in a new habitat. Our global analysis shows that mutualism plays an important, if often overlooked, role in plant and insect invasions.

Anthropogenic Influence on the Distribution of the Longlegged Ant (Hymenoptera: Formicidae)

The longlegged ant Anoplolepis gracilipes (Smith) is a highly invasive tramp ant species known for its deleterious effects on native ecosystems. While tramp ants are associated with human activity, information on how different intensities of human activity affect their distribution is limited. This study investigated how anthropogenic activities affected the distribution of A. gracilipes in Penang, a tropical island in northern peninsular Malaysia. Three study sites (Youth Park, Sungai Ara, and Bukit Jambul/Relau) were selected, containing four sub-locations corresponding to different levels of human activity (low, moderate, high, and very high), determined by the average number of passersby observed over 30 min. Baited index cards were placed at each sub-location to evaluate ant abundance and distribution. The results demonstrated that A. gracilipes worker abundance was highest in areas of moderate human activity, as opposed to areas with low and higher human activity. The low abundance of A. gracilipes in comparatively undisturbed localities may be attributed to unsuitable microclimate, lack of propagule pressure, and diminished honeydew availability. In contrast, its exclusion from more urbanized localities could be explained by high interspecific competition with other tramp species and the absence of preferred nesting sites.

Urban tropical forest islets as hotspots of ants in general and invasive ants in particular

Urbanization is a crucial driver of environmental and biodiversity change. It is suggested that urbanization favours generalist and invasive species and might harm specialists of natural and semi-natural habitats. In this study, we examined how an urbanization gradient and environmental gradients in the habitat area, habitat diversity, elevation, and proportion of built-up area influenced the abundance and richness of ants within tropical forest islet habitat in south India. We used abundance (proportional trap incidence) of overall ants, native ants, invasive ants, and Anoplolepis gracilipes—a globally notorious invasive ant of possible south Asian origin—and rarefied richness as the response variables. We found that native ant abundance was greater and A. gracilipes abundance was lesser in less-urbanized landscape compared to moderately-urbanized and highly-urbanized landscape. The richness of ants and abundance of overall and invasive ants were unaffected by the urbanization. We also found that none of the measured environmental gradients but habitat diversity influenced abundance of overall ants, native ants, overall invasive ants, and richness of ants; however, A. gracilipes abundance was negatively correlated with habitat diversity. Ant species composition of less-urbanized landscape was distinct from that of higher urbanization levels. The richness and abundance of native ants and abundance of non-A. gracilipes invasive ants decreased with the abundance of A. gracilipes. Because the forest islets of all three urbanization levels supported similar richness of native ants, the urbanization seems not to have an adverse effect for the native ants of native forest islets. The increasing population of A. gracilipes in urban green islets, however, is a concern. Future studies might investigate its effect on other invertebrates of epigeal and soil strata.