Soil microbial communities are enormously diverse, with at least millions of species and trillions of genes unknown to science or poorly described. Soil microbial communities are key
components of agriculture, for example in provisioning nitrogen and protecting crops from pathogens, providing overall ecosystem services in excess of $1000bn per year. It is important to know how humans are affecting this hidden diversity. Much is known about the negative consequences of agricultural intensification on higher-organisms, but almost nothing is known about how alterations to landscapes affect microbial diversity, distributions and processes. We
review what is known about spatial flows of microbes and their response to land use change, and outline nine hypotheses to adva
nce research of microbiomes across landscapes. We hypothesise that intensified agriculture selects for certain taxa and genes, which then “spill over” into adjacent unmodified areas and generate a halo of genetic differentiation around agricultural fields.
Consequently, the spatial configuration and management intensity
of different habitats combines with the dispersal ability of individual taxa to determine the extent of spillover, which can
impact the functioning of adjacent unmodified habitats. When land
scapes are heterogeneous and dispersal rates are high, this
will select for large genomes that allow exploitation of multiple habitats
, a process that may be accelerated through horizontal gene transfer.
Continued expansion of agriculture will increase genotypic similarity,
making microbial community functioning increasingly variable
in human
-
dominated landscapes
, potentially also impacting
the consistent provisioning of
ecosystem services
.
While the resulting economic costs have not been calculated, it is
clear
that
dispersal dynamics of microbes
should
be
taken into consideration
to ensure that
ecosystem functioning and services are maintained in
agri
-
ecosystem mosaics
.