Integrating physiology, population dynamics and climate to make multi‐scale predictions for the spread of an invasive insect: the Argentine ant at Haleakala National Park, Hawaii

Abstract

Mechanistic models for predicting species’ distribution patterns present particular advantages and challenges relative to models developed from statistical correlations between distribution and climate. They can be especially useful for predicting the range of invasive species whose distribution has not yet reached equilibrium. Here, we illustrate how a physiological model of development for the invasive Argentine ant can be connected to differences in micro‐site suitability, population dynamics and climatic gradients; processes operating at quite different spatial scales. Our study is located in the subalpine shrubland of Haleakala National Park, Hawaii, where the spread of Argentine ants Linepithema humile has been documented for the past twenty‐five years. We report four main results. First, at a microsite level, the accumulation of degree‐days recorded in potential ant nest sites under bare ground or rocks was significantly greater than under a groundcover of grassy vegetation. Second, annual degree‐days measured where population boundaries have not expanded (456–521 degree‐days), were just above the developmental requirements identified from earlier laboratory studies (445 degree‐days above 15.9°C). Third, rates of population expansion showed a strong linear relationship with annual degree‐days. Finally, an empirical relationship between soil degree‐days and climate variables mapped at a broader scale predicts the potential for future range expansion of Argentine ants at Haleakala, particularly to the west of the lower colony and the east of the upper colony. Variation in the availability of suitable microsites, driven by changes in vegetation cover and ultimately climate, provide a hierarchical understanding of the distribution of Argentine ants close to their cold‐wet limit of climatic tolerances. We conclude that the integration of physiology, population dynamics and climate mapping holds much promise for making more robust predictions about the potential spread of invasive species.

Relative roles of climatic suitability and anthropogenic influence in determining the pattern of spread in a global invader

“…Climatic suitability sets the abiotic conditions that allow species to establish and spread, and climate matching has been identified as a key factor for invasion of many invasive species (9,30). This is especially true for the Argentine ant, whose occurrence at regional scales is highly constrained by temperature and humidity (25,26,31,32). At local scales, establishment by the Argentine ant in climatically favorable areas is also favored by anthropogenic factors (33,34 In its native range, the abundance and impact of the Argentine ant may be constrained by the presence of highly dominant native ant species in the same subfamily (Dolichoderinae) (18).…”

“…Many studies have examined the distribution and dispersal pathways of this invasive ant (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) and described the range limits at regional and global scales (20,(23)(24)(25)(26)(27)(28). However, most of these studies relied on simple environmental niche models or described the current distribution of the species using only partial records.…”

Modifying climate change habitat models using tree species-specific assessments of model uncertainty and life history-factors

“…Thus, there is some probability that the species currently occupying zones that will have novel climates may be able to adapt to those new conditions in situations of limited competition from species more tolerant of those new conditions. The Australian study however also establishes an additional danger of climate change, that being the concomitant influx and flourishing of invasive plants (Hellmann et al, 2008;Dale et al, 2009;Dukes et al, 2009;Hartley et al, 2010). Also important is the physiological impacts on plant establishment and growth if temperatures increase greatly (as projected under HADhi) while precipitation changes little, resulting in more evaporative loss, and leading to greater physiological stress on the biota (Allen et al, 2010).…”

Mapping the Potential Global Range of the Brown Marmorated Stink Bug, Halyomorpha halys, with Particular Reference to New Zealand

“…Modeling techniques have frequently been used to determine the spread of invasive insects under current environmental conditions [59,60] and under the influence of climate change [32,61,62]. The current study has shown that the use of modeling techniques, particularly combined methods, allows the prediction of potential current and future environmental suitability for an invasive insect, BMSB, in a novel environment, i.e., New Zealand.…”