Data from: Biogeographic variation of distance-dependent effects in an invasive tree species

1.Plant pathogens and herbivores can maintain forest diversity by reducing
survival of tree seedlings close to conspecifics. However, how
biogeographic variation in these natural enemies affects such
distance‐dependent processes is unknown. Because invasive plants escape
ecologically important enemies when introduced to a new range,
distance‐dependent mortality may differ between their native and
introduced ranges. 2. Here, we test whether the invasive tree Triadica
sebifera escaped distance‐dependent mortality when introduced to the US
from China, and examine the roles of natural enemies in native and
introduced ranges. In both US and China, we performed field surveys along
with field and greenhouse experiments with field collected soils and soil
sterilization treatments. 3. In field surveys and the field experiment,
insect damage on T. sebifera seedlings decreased with distance to
conspecific trees in the native range (China) but damage was low at all
distances in the introduced range (US). In the greenhouse experiment
testing the effects of soil pathogens, T. sebifera seedling mortality
decreased with soil distance from conspecific trees in both ranges but
distance‐independent mortality was higher in native range soils. 4. Our
findings indicate that both insect herbivores and the soil biota
contribute to distance‐ dependent effects on T. sebifera in its native
range. They suggest, however, that plants may more readily escape
herbivore than soil biota distance‐dependent effects when introduced to a
new range and so herbivores, rather than soil pathogens, contribute more
strongly to biogeographic variation in distance‐dependent effects. These
results highlight the importance of considering species biogeographic
variation in distance‐dependent effects and teasing apart the roles that
different natural enemies play when studying species coexistence,
community diversity, and biological invasions.