Microbes, similar to plants and animals, exhibit biogeographic patterns. However, in contrast with the considerable knowledge on the island biogeography of higher organisms, we know little about the distribution of microorganisms within and among islands. Here, we explored insular soil bacterial and fungal biogeography and underlying mechanisms, using soil microbiota from a group of land-bridge islands as a model system. Similar to island species-area relationships observed for many macroorganisms, both island-scale bacterial and fungal diversity increased with island area; neither diversity, however, was affected by island isolation. By contrast, bacterial and fungal communities exhibited strikingly different assembly patterns within islands. The loss of bacterial diversity on smaller islands was driven primarily by the systematic decline of diversity within samples, whereas the loss of fungal diversity on smaller islands was driven primarily by the homogenization of community composition among samples. Lower soil moisture limited within-sample bacterial diversity, whereas smaller spatial distances among samples restricted among-sample fungal diversity, on smaller islands. These results indicate that among-island differences in habitat quality generate the bacterial island species-area relationship, whereas within-island dispersal limitation generates the fungal island species-area relationship. Together, our study suggests that different mechanisms underlie similar island biogeography patterns of soil bacteria and fungi.
- NSF-PAR ID:
- 10387310
- Date Published:
- Journal Name:
- Communications Biology
- Volume:
- 5
- Issue:
- 1
- ISSN:
- 2399-3642
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Aim Nitrogen (N)‐fixing plants are an important component of global plant communities, but the drivers of N‐fixing plant diversity, especially in temperate regions, remain underexplored. Here, we examined broad‐scale patterns of N‐fixing and non‐fixing plant phylogenetic diversity (PD) and species richness (SR) across a wide portion of temperate North America, focusing on relationships with soil N and aridity. We also tested whether exotic species, with and without N‐fixing symbiosis, have fewer abiotic limitations compared with native species.
Location USA and Puerto Rico.
Time period Current.
Major taxa studied Vascular plants, focusing on N‐fixing groups (orders Fabales, Fagales, Rosales and Cucurbitales).
Methods We subset National Ecological Observatory Network (NEON) plant plot data from all sites along two axes (N fixing–non‐N fixing and native–exotic), calculating plot‐level SR, PD and mean pairwise phylogenetic distance (MPD). We then used linear mixed models to investigate relationships between diversity values and key soil measurements, along with aridity, temperature and fire frequency.
Results Aridity was the sole predictor of proportional phylogenetic diversity of N fixers. The SR of N fixers still decreased marginally in arid regions, whereas native N‐fixer MPD increased with aridity, indicative of unique lineages of N fixers in the driest conditions, in contrast to native non‐N fixers. The SR of both native N fixers and non‐N fixers increased in low‐N soils. Aridity did not affect SR of exotic non‐N fixers, unlike other groups, whereas exotic N fixers showed lower MPD in increasingly high‐N soils, suggesting filtering, contrary what was found for native N fixers.
Main conclusions Our results suggest that it is not nitrogen, or any soil nutrient, that has the strongest effect on the relative success of N fixers in plant communities. Rather, aridity is the key driver, at least for native species, in line with empirical results from other biomes and increased understanding of N fixation as a key mechanism to avoid water loss.
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1038/s42003-022-04133-x
