How ants have an "economic spectrum" of roles and resource management, and what it teaches scientists about ecosystems.
A July study by Heloise Gibb and ten other researchers proposes an economic spectrum based on ants, inspired by the "leaf economics spectrum" that has been researched for decades. The complexities of eusociality make ant colonies a great model for organisms' interactions with the environment. Ecological strategies are often considered akin in value to the periodic table in chemistry. Furthering an understanding of different niches helps ecologists understand the roles each organism serves; this is vital as ecosystems lose native species and invasives find new homes due to human activity.
The leaf economics spectrum covers how plants put resources into their leaves and specialize leaves for different purposes according to environmental needs. Some leaves have quick resource returns but are worse for investing, and vice versa. Most ants and plants live relatively stationary lives, thus making it easier to observe how they invest their resources into survival and reproduction. Some interesting parallel trends are noted; ants with larger colonies create proportionately fewer, but larger alates, and plants have a similar strategy with seeds. Larger body reserves allow queens to produce more workers in founding. Some ants can achieve larger colonies while having smaller queens with "dependent" founding, or budding, where workers assist new queens in establishing colonies (think species like Linepithema humile). Defense is another important factor, often through features like foul compounds or thorns in plants, and seen in a myriad of forms in ants; spines, stings, supermajors, and nest structure are just some examples. However, defensive traits take extra resources, and species are even known to lose them—such as the supermajor caste from most Pheidole that evolved it—in favor of reserving resources (Rajakumar et al., 2012). Polydomy (multiple nests) and polygyny (multiple queens) are highlighted as traits that can help defend colonies from predators and pathogens, but the trade-off is that these colonies cannot optimally reproduce in more variable, sparse, or harsh environments.
Even features that seem incomparable such as leaves versus roots have some parallels in ants, such as how workers can serve to forage for food and to store the food with their social stomachs. Plants have varying root designs often associated with their level of reliance on mycorrhizal fungi, and a similar spectrum is seen in mandible and clypeus development in ants relative to their husbandry (honeydew farming through aphids and other bugs) and hunting specializations. There are also ants that directly work with fungi, such as fungus-farming ants and those that use fungi to create nest structures with debris.
With the diverse nature of ants and plants and their sessile lifestyles, both can be strong and easily observable indicators of ecological strategies. Emphasis is put on future research to collect a variety of data on ants, not just taxonomically but also on physiology, environmental conditions, diets, and lifespans. Many traits are hard or expensive to research, but getting a full picture is core to interpreting ecological strategies.