Wood ants as biological control of the forest pest beetles Ips spp.

Abstract

Climate change is one of the major threats to biodiversity, but its impact varies among the species. Bark beetles (Ips spp.), as well as other wood-boring pests of European forests, show escalating numbers in response to the changes driven by climate change and seriously affect the survival of the forests through the massive killing of trees. Many methods were developed to control these wood-boring beetles, however, their implementation can be detrimental for other forest specialists. Ants are widely used for biological pest-control, so in our study, we aimed to test the effect of Formica polyctena on the control of the wood-boring beetles. The results show that the proportion of infested trees is significantly reduced by the increase of the number of F. polyctena nests, with a strong effect on those infested by Ips species. We also show that the boring beetle community is shaped by different biotic and abiotic factors, including the presence of F. polyctena nests. However, the boring beetle infestation was not related to the latitude, altitude and age of the forests. Based on our results, we assert the effectiveness of the red wood ants as biological pest control and the importance of their conservation to keep the health of the forests.

Implementing wood ants in biocontrol: Suppression of apple scab and reduced aphid tending

“…Further examples have been identified where Crematogaster scutellaris ants inhabiting oak galls reduced fungal infections on oak leaves 24 and weaver ant presence ( Oecophylla longinoda ) in orange trees reduced post‐harvest decay caused by anthracnose and green mould 25 . Although no effect has been found with Formica polyctena in reducing fungal infections of various forest trees, it has been observed that this ant species tended to reduce infections ( P = 0.086) 26 . Lastly, it has been observed that wood ants ( F. polyctena ) used for insect biocontrol in an apple plantation reduced the incidence of both apple brown rot ( Monilia fructigena ) and apple scab ( Venturia inaequalis ) on apples 16 and that the presence of various ant species reduced pear scab ( V. pyrina ) on pear trees 27 …”

“…25 Although no effect has been found with Formica polyctena in reducing fungal infections of various forest trees, it has been observed that this ant species tended to reduce infections (P = 0.086). 26 Lastly, it has been observed that wood ants (F. polyctena) used for insect biocontrol in an apple plantation reduced the incidence of both apple brown rot (Monilia fructigena) and apple scab (Venturia inaequalis) on apples 16 and that the presence of various ant species reduced pear scab (V. pyrina) on pear trees. 27 Ants are thus promising biological control agents that may be effective and broadly beneficial in open agricultural systems.…”

Extensive hybridisation between multiple differently adapted species may aid persistence in a changing climate

“…Specifically, hybridisation has resulted in male-biased mortality, female heterosis and potential for thermal adaptation (Kulmuni & Pamilo, 2014; Martin-Roy et al, 2021). Understanding hybridisation in the F. rufa group ants is important, since they are keystone species in boreal and mountain forests across Eurasia (Stockan & Robinson, 2016; Trigos-Peral et al, 2021). They build stable nest mounds (Seifert, 2018), and polygynous (i.e., multiple queens per nest) species and populations in particular can reach densities of hundreds of nests per km², as well as impact ecosystem characteristics, ranging from nutrient cycling below ground to aphid farms in the forest canopy.…”

Semipermeable species boundaries create opportunities for gene flow and adaptive potential

“…Instability in the barriers of gene flow has been reported previously (Kulmuni et al, 2020) in this system, suggesting that the balance between the costs and benefits of hybridisation may vary across space and time. Understanding hybridisation in the F. rufa group is important since these ants are keystone species in boreal and mountain forests across Eurasia (Stockan & Robinson, 2016; Trigos‐Peral et al, 2021). They have a significant role in the forest ecosystem: they build stable nest mounds (Seifert, 2018), and populations of polygynous (i.e.…”