Abiotic effects of fragmentation lead to changes in fungal community structure

Michelle H. Hersh, Biology, Sarah Lawrence College, Bronxville, NY, Dirk Baker, Campbell Scientific, Inc., Logan, UT and Cathy Collins, Biology, Bard College, Annandale-on-Hudson, NY

Background/Question/Methods
Habitat fragmentation is an important driver of changes in species diversity and ecosystem function, and a growing concern in light of increased development and sprawl. Small patches can have more extreme temperature ranges, lower soil moisture, and higher light levels. These abiotic changes can alter plant community structure and diversity in small patches. However, abiotic effects of fragmentation on microbial communities are less well understood. We explored how fragmentation affects fungal communities residing in plant seeds. Seed-associated fungi can be an important cause of juvenile plant mortality and can help maintain plant diversity via negative feedbacks. We tested the hypotheses that soil moisture and temperature are more variable in small patches, and seed-associated fungal community structure is dependent on host identity, patch size, temperature, and soil moisture. In an experimentally fragmented habitat in Lawrence, KS, USA, we buried seeds of seven plant species for one year in different landscape locations (large patch edge, large patch interior, small patch, matrix), while collecting continuous soil temperature and moisture data. Fungi were cultured from seeds and identified using DNA barcoding. We used PERMANOVA to test whether host species identity, landscape location, and soil moisture and temperature predicted fungal community composition.
Results/Conclusions
Soil moisture and soil temperature were spatially structured in our experimentally fragmented landscape. We included mean and range soil temperature and moisture over the year of burial in analyses. As predicted, soil moisture variability was lowest in the interior of large patches, and temperature variability was highest in the matrix. Contrary to our predictions, soils in small patches were not significantly warmer or more variable than patch interiors. To date, we have sequenced 863 fungal cultures. Mean range in annual soil temperature (Pseudo-F = 2.82; P<0.001) and mean soil moisture (Pseudo-F = 2.48; P<0.01) were significant predictors of fungal community composition. After accounting for these environmental variables, fungal community composition differed according to host seed species (Pseudo-F=2.88; P<0.001) and landscape location (edge, interior, small patch, or matrix; Pseudo-F=1.42; P<0.05). Neither landscape location, average moisture, or temperature variability predicted fungal richness (P>0.05). This work indicates that fragmentation could have direct and indirect effects on fungal community structure. The changes in seed-associated fungal community structure in response to fragmentation could have subsequent effects on plant community structure and diversity.