ABSTRACT In recent decades, the microbiota has emerged as a key driver of biological functions in metazoans, and nematodes are no exception. Advances in genomic technologies have enabled detailed exploration of nematode–microbiota interactions, revealing compelling insights. However, much of our current understanding is derived from studies on the model organism Caenorhabditis elegans , where the microbiota's role in shaping host phenotypes and genotypes has been extensively characterized. These studies have uncovered the selective pressures influencing the function, structure, and assembly of the microbiota, highlighting the dynamic interplay between nematodes and their associated microbial communities. Despite these findings, the ecological and evolutionary implications of the microbiota in nematodes remain underappreciated. Emerging evidence indicates that the microbiota can modulate nematode life‐history traits and mediate trade‐offs among fitness components. Moreover, mechanisms such as horizontal gene transfer from bacteria have been shown to alter nematode phenotypes and genotypes, facilitating adaptation to novel or challenging environments. In this review, we integrate life‐history theory into the nematodes–microbiota interactions, offering a framework to identify the mechanisms driving phenotypic variation in nematodes. Understanding these processes is essential for uncovering the evolutionary and ecological bases of metazoan diversification, with the microbiota acting as a crucial source of phenotypic and genetic variability.
Trejo‐Meléndez et al. (Fri,) studied this question.