Invasive Stink Bugs and Related Species (Pentatomoidea)

262 Invasive Stink Bugs and Related Species (Pentatomoidea)

this bug in new areas worldwide. In addition, the realized climate niches of the introduced United States
and European populations were different from that of the native Asia population, with the introduced
populations only occupying partial climate space of the native Asia population (Zhu et al. 2012) (Figure
4.5). These results suggest the climate space was unfilled in the introduced populations; there might be
much suitable climate space available for this bug in the North America and Europe, which contributes
to the continued population expansion in new areas.
Niche models were calibrated on the native Asia areas and transferred onto the global extent using
both Maxent and GARP. Maxent is a machine-learning technique that predicts species’ distribution by
integrating detailed environmental variables with species occurrence data; it follows the principle of
maximum entropy and spreads out probability as uniformly as possible but is subject to the caveat that
it must match empirical information such as known presence; the Maxent models were developed using
the linear, quadratic, and hinge functions to avoid the problem of over-fitting. Although Maxent has
appeared superior to GARP in some previous studies, careful assessments of model quality showed no
significant differences between the two. Recent studies suggested using multiple algorithms to infer a
consensus estimate of niche dimensions.
At the global scale, the high climate suitable areas at risk of invasion by Halyomorpha halys include
latitudes between 30°–50° including northern Europe, northeastern North America, southern Australia,
and the North Island of New Zealand. Angola in Africa and Uruguay in South America also showed high
climate suitability (Zhu et al. 2012) (Figure 4.6). Attention should be paid to the high-suitability areas

Maxent

GARP

FIGURE 4.5 (See color insert.) Potential distribution of Halyomorpha halys worldwide based on ecological niche modeling.
Niche models were calibrated on the native Asia and transferred onto the global using Maxent and GARP, dark green suggests
high suitability, light green indicates low suitability (modified from Figure 6 and Supplemental Materials 1 in Zhu et al. 2012).