Experimental evidence that increased surface temperature affects bioturbation by ants.

Ants are important bioturbators that actively produce biopores and move soil particles. They could be particularly affected by global warming as they are ectotherms. Nevertheless, they can indirectly regulate their temperature, through changes in their circadian cycles and the architecture of their nests (e.g. digging deep nests or using insulating materials). Nest architecture has been considered an expanded functional trait of ant colonies and thus sensitive to environmental changes such as increasing temperatures. This work aimed to study the nest architecture of ants as a functional trait and its effects on soil bioturbation. We hypothesized that, when exposed to increased surface temperatures, ants would increase their excavation activities, build deeper nests and alter the layout of chambers to maintain their preferred temperature and humidity, thus enhancing soil porosity. We allowed 17 young Lasius niger ant colonies to excavate nests in soil columns exposed to three surface temperatures (mild, n = 5; medium, n = 6; and high, n = 6) for 100 days. We measured the amount of soil excavated weekly and took X-ray scans of the soil column on Days 7, 14, 28, and 88 to characterize the three-dimensional structure of the nests (depth, shape, volume of chambers and tunnels). We then collected the colonies and measured their growth during the experiment, and the size and weight of workers. Ants reacted to surface temperature. Colonies exposed to medium and high temperatures excavated larger and deeper nests than those exposed to mild temperature. Nests excavated under high and medium temperatures had the same maximal depth, but chambers were located deeper in the former, which were further characterized by the refiling of some of the upper chambers. Colonies grew well in all treatments, although less under mild temperature. They produced normal-sized workers despite differences in surface temperature. Overall, these results suggest that ants exposed to higher temperatures live in deeper chambers. This study shows that surface temperature affects ant nest architecture, confirming its status as extended phenotype and highlighting its flexibility over time, which has in turn consequences on soil porosity.

Moving beyond the distinction between the bright and dark sides of termites to achieve sustainable development goals.

Termites are amongst the main macroinvertebrate decomposers in tropical ecosystems and they exert additional impacts through the creation of biostructures (mounds, galleries, sheetings, etc.) with different soil physical and chemical properties, thereby impacting positively on numerous ecosystem services for humankind. Unfortunately, this positive or 'bright' role of termites is often overshadowed by their 'dark' side, that is, their status as pests threatening agriculture and constructions. This article assesses advances in our knowledge of the impact of termites on several sustainable development goals (SDGs 1 'no poverty', 2 'zero hunger', 3 'good health', 9 'innovation', 11 'sustainable cities', 13 'climate action' and 15 'life on land'). Finally, using the Indian myth of Valmiki as a parable, we illustrate that a reconciliation between the termite's dark and bright sides is needed if we want to reduce our dramatic impact on biodiversity and more generally achieve SDGs.

Linking Termite Feeding Preferences and Soil Physical Functioning in Southern-Indian Woodlands.

Termites are undoubtedly amongst the most important soil macroinvertebrate decomposers in semi-arid environments in India. However, in this specific type of environment, the influence of termite foraging activity on soil functioning remains unexplored. Therefore, this study examines the link between the quality of litter and the functional impact of termite feeding preferences on soil properties and soil hydraulic conductivity in a deciduous forest in southern India. Different organic resources (elephant dung: "ED", elephant grass: "EG", acacia leaves: "AL" and layers of cardboard: "CB") were applied on repacked soil cores. ED appeared to be the most attractive resource to Odontotermes obesus, leading to a larger amount of soil sheeting (i.e., the soil used by termites for covering the litter they consume), more numerous and larger holes in the ground and a lower soil bulk density. As a consequence, ED increased the soil hydraulic conductivity (4-fold) compared with the control soil. Thus, this study highlights that the more O. obesus prefers a substrate, the more this species impacts soil dynamics and water infiltration in the soil. This study also shows that ED can be used as an efficient substrate for accelerating the infiltration of water in southern-Indian soils, mainly through the production of galleries that are open on the soil surface, offering new perspectives on termite management in this environment.