Data supporting: Drivers of individual-based, antagonistic interaction networks during plant range expansion

1. Range expansion in plant populations, especially at the colonization
front, can be either limited by disproportionately large effects of
antagonistic interactions or facilitated by their release. How the
strength of antagonistic interactions changes along successional gradients
during range expansion is still poorly documented, especially when diverse
assemblages of plant antagonists (rodents, invertebrates, and birds)
combine within interaction networks. 2. We study the changes in
individual-based, predispersal seed-pulp predator networks along a
colonization gradient in a rapidly-expanding Juniperus phoenicea
population in Doñana National Park (SW Spain). Additionally, we analysed
the role of individual plant traits and neighbourhood attributes in
network configuration by using Exponential Random Graph Models. 3. Seven
seed-pulp consumer animal species varied significantly in their frequency
of interaction and prevalence. While invertebrate species were well
established in old and intermediately mature stands, greenfinch (Chloris
chloris) was dominant at the colonization front. Variable species roles
and spread of interactions among individual plants generated changes in
the configuration of interactions during plant expansion. 4. Individual
plant traits strongly determined the topology of these networks, although
with differences between stands. Increasing individual crop size and seeds
per cone increased the interaction odds of individual plants, while seed
viability showed the opposite effect. The network topology at the
colonization front appeared less driven by individual traits, possibly
because of the short interaction history of this recently established
area. The disproportionately large effect of C. chloris in these
recently established stands, potentially resulted in large seed losses
during range expansion. 5. Synthesis.  Turnover of
antagonistic interactions, characterized the colonization front, resulting
in more heterogeneous interaction strengths among individual plants. We
found no evidence for a complete or sizeable antagonistic release
of J. phoenicea at the colonization front promoting this rapid
expansion. It becomes necessary to explore interactions with seed
dispersers to understand how antagonistic and mutualistic plant-animal
interactions balance during range expansion. Our study highlights the
importance of an individual-based approach in understanding how
interactions are structured and driven in natural changing landscapes.