Anthropogenic habitat fragmentation is a key driver of biodiversity loss, especially in urban centers. While studies have analyzed fragmentation effects on macro-organisms, we are just beginning to understand these effects on microbial “hidden players” whose ecosystem services can span multiple levels of biological organization. Our study uses the highly fragmented South Florida Pine Rockland ecosystem to describe the effects of fragmentation on two vital, poorly-understood microbial communities (soil and phyllosphere microbiomes) and their consequences for the plants and herbivores with whom they interact. First, we conducted quantitative herbivory surveys and characterized phyllosphere microbiomes of six native plant species in 15 Pine Rockland fragments. Additionally, we collected soil from 14 Pine Rockland fragments to characterize their microbiomes and test their effects on native plant performance. We sowed seeds from 3 native Pine Rockland plant species in the presence and absence of microbiomes from each of the 14 fragments (14 fragments x2 microbial treatments x3 replicates x 3 species). We measured germination and plant performance parameters, such as leaf growth and specific leaf area. The phyllosphere and soil microbiomes were characterized using 16S and ITS barcode regions targeting bacteria and fungi (respectively).
Results/Conclusions
Analysis of plant herbivory data shows that species interactions between plants and herbivores vary with degree of habitat connectivity. Our results demonstrate that different types of herbivory within and between plant species can differ in strength and direction of their relationship with habitat connectivity. For example, leaf mining increased in Passiflora suberosa with increasing connectivity (F2,99=2.99, p=0.057) while Chromolaena odorata showed the inverse (F2,33=10.0, p<0.01). Additionally, preliminary analysis of soil microbial effects on plant performance indicated live soils increased leaf growth (up to 190% greater; z=7.41, p<0.01) and decreased days to germination (up to 55% faster; z=-5.11, p<0.01) in most species. Further, fragment area and connectivity of soil sources influenced leaf growth and germination rates. These relationships also vary in strength and direction depending on plant species identity. Our results suggest that habitat fragmentation has complex effects on species interactions between and among both macro-organisms and microorganisms. This work will inform our general understanding of complex, native microbiomes and provide some of the first insight into how fragmentation’s impact on microbial communities affects species interactions and primary production.