Hemlock woolly adelgid niche models from the invasive eastern North American range with projections to native ranges and future climates

Abstract

The hemlock woolly adelgid (Adelges tsugae Annand-HWA) is invasive in eastern North America where it causes extensive mortality to hemlock communities. The future of these communities under projected climate change is an issue of landscape ecological interest and speculation. We employed the MaxEnt algorithm with the random subset feature selection algorithm (RSFSA) in creating HWA niche models. Final models were ensembles of 12 statistically best models with six predictors each. Out of 119 climatic, topographic, and soil variables, 42 were used in at least one final model. Soil features, followed by climate and topographic features, were most common in selected models. The three most important variables among all models were November potential evapotranspiration, slope, and percent Ochrepts soil. The potential distributions of HWA within eastern North America were projected under historical and four future climate scenarios for 2050 and 2070 under low and high CO2 emissions. The mean of the minimum values for the minimum temperature of the coldest month from the 12 MaxEnt model projections in eastern North America was-15.8°C. This value was close to-15°C, the extreme minimum temperature found for both HWA occurrence points and previously reported HWA cold temperature limits. These results indicate that HWA may be close to equilibrium distribution in eastern North America under current climate. We also reverse-casted the eastern North American MaxEnt model back onto the HWA native ranges in eastern Asia and western North America. The projections match best with native ranges in Asian islands, such as Japan, and the Cascade Mountains in western North America. Statistically significant HWA range shifts of 221-468 km northwards and 110-164 km eastwards were projected by the 12 models for 2050-2070. The 2070 high CO2 emission scenario models projects HWA suitability throughout most of the northern range of eastern hemlock.

Distribution, phenology, and land cover preference risk assessments of four South-Central US milkweeds (Asclepias spp.) important for monarch butterflies

“…WorldClim indices (Bradie and Leung 2016), including the SuppClim and AET/PET indices, supporting our previous ndings (Tracy et al 2018(Tracy et al , 2019Kantola et al 2019b). This is the rst study to nd that soil taxa are important variables for niche modeling of milkweeds, with soil taxa variables highly ranked in niche models of all four South-Central US species.…”

“…The RSFSA revealed that subsets of six to eight of 95 variables were optimal for maximizing performance of MaxEnt models of the four milkweed species. Tracy et al (2019) and Kantola et al (2019b) also found that six and eight variables was an optimal subset size for MaxEnt models using RSFSA with large sets of 80 and 119 variables, respectively. Consistent with previous niche modeling studies using RSFSA, we found signi cantly improved values of AUC psa and AICc bg for selected models over random models, but over tting was only sometimes improved (Tracy et al 2018(Tracy et al , 2019Kantola et al 2019b).…”

“…Tracy et al (2019) and Kantola et al (2019b) also found that six and eight variables was an optimal subset size for MaxEnt models using RSFSA with large sets of 80 and 119 variables, respectively. Consistent with previous niche modeling studies using RSFSA, we found signi cantly improved values of AUC psa and AICc bg for selected models over random models, but over tting was only sometimes improved (Tracy et al 2018(Tracy et al , 2019Kantola et al 2019b). We found that AUC psa criterion reduced over tting in more RSFSA replications than the AICc bg criterion, as found by Kantola et al (2019b), but the AICc bg criterion can yield lower over tting with RSFSA in some cases (e.g., Tracy et al 2018), or the two criteria may be equal in e cacy with regards to over tting (Tracy et al 2019).…”

Microbiome Variation Across Two Hemlock Species With Hemlock Woolly Adelgid Infestation

“…The HWA does not appear to harm hemlock species within its native range of Asia and northwestern North America (Oten et al, 2014). However, in the mid 20th century, the HWA arrived in the eastern United States (USA) with the introduction of ornamental hemlocks, and it has since spread from northern Georgia to southern Nova Scotia (Kantola et al, 2019). Hemlock loss can have ecosystem-level effects owing to their foundational role in some eastern mixed hardwood forests.…”

Ecological Niche Modeling to Calculate Ideal Sites to Introduce a Natural Enemy: The Case of Apanteles opuntiarum (Hymenoptera: Braconidae) to Control Cactoblastis cactorum (Lepidoptera: Pyralidae) in North America

“…A strategy developed to select appropriate sites for the natural enemy’s liberation based on prioritizing its environmental requirements could increase the success of biological control agents [ 32 ]. Ecological niche modeling is a tool widely used for estimating environmental suitability for organisms, building ecological models for successful prediction in specific geographic areas of interest [ 33 , 34 , 35 , 36 ]. In this study, we calculated the ecological niche model for A. opuntiarum and C. cactorum to define regions of environmental suitability and determine niche overlap for the purpose of predicting areas of successful establishment of this parasitoid in North America.…”