Exoskeletal thinning in Cephalotes atratus ants (Hymenoptera: Formicidae) parasitized by Myrmeconema neotropicum (Nematoda: Tetradonematidae)

Among the shapeshifters: parasite-induced morphologies in ants (Hymenoptera, Formicidae) and their relevance within the EcoEvoDevo framework

As social insects, ants represent extremely interaction-rich biological systems shaped by tightly integrated social structures and constant mutual exchange with a multitude of internal and external environmental factors. Due to this high level of ecological interconnection, ant colonies can harbour a diverse array of parasites and pathogens, many of which are known to interfere with the delicate processes of ontogeny and caste differentiation and induce phenotypic changes in their hosts. Despite their often striking nature, parasite-induced changes to host development and morphology have hitherto been largely overlooked in the context of ecological evolutionary developmental biology (EcoEvoDevo). Parasitogenic morphologies in ants can, however, serve as “natural experiments” that may shed light on mechanisms and pathways relevant to host development, plasticity or robustness under environmental perturbations, colony-level effects and caste evolution. By assessing case studies of parasites causing morphological changes in their ant hosts, from the eighteenth century to current research, this review article presents a first overview of relevant host and parasite taxa. Hypotheses about the underlying developmental and evolutionary mechanisms, and open questions for further research are discussed. This will contribute towards highlighting the importance of parasites of social insects for both biological theory and empirical research and facilitate future interdisciplinary work at the interface of myrmecology, parasitology, and the EcoEvoDevo framework.

The geographic distribution of parasite-induced fruit mimicry in Cephalotes atratus (Formicidae: Myrmicinae)

Parasite distributions fundamentally depend on the distributions of their hosts but may be more restricted than their hosts. Host-parasite symbioses tend to be spatially aggregated, and widely distributed host-parasite relationships are rare. Here, we combine field observations with published collection data to document the current known distribution of the nematode, Myrmeconema neotropicum, which infects the Neotropical canopy ant Cephalotes atratus. We report 6 new records from different Brazilian ecosystems, bringing the total number of independent observations of this interaction to 11. The broad distribution of these data points suggests that M. neotropicum infects C. atratus throughout its geographic range, although possible disturbance effects and specific habitat associations of the interaction remain unknown.