The context-dependent symbiosis in marine and terrestrial tropical systems
Symbiotic relationships between microbes and host animals and plants are ubiquitous in terrestrial and marine environments. Yet, we are just beginning to understand and characterize the nuanced nature of these relationships, particularly in tropical environments. Symbioses represent a continuum, from beneficial to detrimental for the host. These relationships are not fixed in time and space, rather they are highly context dependent. A commensal symbiont can become pathogenic when a host’s health or nutritional status changes. Mutualisms can break down because, in the absence of sanctions, partners cheat. Pathogenic symbionts can benefit a host if they do more harm to a host’s competitors than the host itself. Additionally, the suite of symbionts inhabiting a given host are not fixed spatiotemporally and microbial symbionts interact with one another and can have synergistic or opposing effects on host fitness. Moreover, environmental changes linked to anthropogenic activities affect the nature and dynamics of host-symbiont relationships in ways that remain poorly known. We brought 14 experts (seven terrestrial and seven marine) to STRI for a one-day symposium and a three-day workshop. The proposed experts were selected to capture ecological and evolutionary biology and a range of symbiotic systems, make meaningful contributions to a synthesis paper and highlight novel approaches. Without foundational science on terrestrial and marine symbionts, we cannot understand which factors drive the maintenance of diversity, speciation, and biogeochemical cycles in our tropical forests and oceans, nor can we project future responses to human driven changes to land and climate.