The Bacteria of a Fig Microcommunity.

UNLABELLED

Understanding the biotic drivers of diversity is a major goal of microbial ecology. One approach towards tackling this issue is to interrogate relatively simple communities that are easy to observe and perturb. Figs (syconia) of the genus represent such a system. Here, we describe the microbial communities of figs, which are associated with the nematode (the sister species of the genetic model system). In 2019, 38 figs (across 12 plants in Taiwan) were dissected, and metadata such as foundress wasp number and nematode occupancy were collected for each fig. Suspensions derived from interior fig material and fig surface washes were prepared for 16S microbial metabarcoding. Over 3,000 OTUs were detected, and microbial communities were dominated by members of , , and . Although microbial communities of fig exteriors and interiors can be distinguished, levels of microbial alpha diversity were comparable across these areas of the fig. Nematodes likewise had no detectable impact on microbial alpha diversity, although nematodes were associated with a modest change in microbial community composition. A handful of OTUs (associated with the genera , , and ) revealed potential differential abundance among figs varying in nematode occupancy. Additionally, foundress wasp number was negatively correlated with microbial alpha diversity. These findings set the stage for future studies that directly test the role of nematode and wasp occupancy on microbial communities, as well as investigations that probe nematode-microbe interactions through laboratory experiments. Taken together, these results constitute a fundamental step in characterizing the natural microbial communities of figs and nematodes.

IMPORTANCE

Unraveling why different species live in different places is a longstanding open question in ecology, and it is clear that interspecific interactions among species are a major contributor to species distributions. figs are a useful system for ecological studies because they are relatively simple microcosms where characterizing animal community composition of multiple samples is straightforward. Additionally, , a close relative of the genetic model system, thrives in figs. Here, we tie 16S microbial metabarcoding to nematode and wasp occupancy data to understand the causes of bacterial community composition in figs. We found that microbial composition, but not total diversity, varies among fig surface and interiors. Likewise, we found that nematode occupancy impacts microbial composition but not alpha diversity. Moreover, we show that as the number of foundress wasps increases, the microbial alpha diversity decreases. Finally, we identified OTUs that are potentially associated with nematode occupancy. Taken together, these results represent a key step in describing a microcommunity wherein ecological genetic hypotheses can be tested, as well as one that can potentially reveal the roles of uncharacterized genes in established model systems.