Halyomorpha halys (Stål) 263
around the world, especially in developed areas with intensive trade activity with Japan, Korea or China.
Strict quarantine inspection must be taken in these areas because commercial interchange might facili-
tate new invasions. In the United States, the models successfully identified the current disjunct distribu-
tion pattern of this bug, including successful anticipation of specific counties in Oregon, California (not
shown), and Washington (Zhu et al. 2012) (Figure 4.6). Because some central states also showed high
suitability for this bug, populations may be able to form a continuous distribution in the United States.
This prediction was consistent with the observed population of H. halys in the United States. Recently,
adults were intercepted continuously in Florida from the highly suitable area in the central Atlantic
States. However, nymphs and eggs never have been found, suggesting this bug has not established popu-
lations in Florida (Julieta Brambila, personal communication; see Acknowledgments). This, most likely,
is due to the unsuitable climate in southeastern United States. Nevertheless, one must keep in mind that
the ENMs seek to identify suitable climate space for species but without consideration of biotic interac-
tions or dispersal ability. Many factors influence successful establishment of non-indigenous species into
a community and depends on existing species composition and richness, competitors, predators, food
availability, human footprint, and climatic similarity, compared with the source areas.
In 2016, Zhu et al. (2016) used our understanding of niche filling and current data on the distribution of
Halyomorpha halys to look at intraspecific variation in realized niche filling and unfilling and the impact
FIGURE 4.6 (See color insert.) Niche models for Halyomorpha halys based on native Asia extent and transferred onto
the United States using Maxent. Dark green represents high suitability, light green indicates low suitability. Model was
built using 6 variables, white and black dots represent the 95 occurrences for model calibration and the remaining for model
evaluation (modified from Figure 3 in Zhu et al. 2012).