Prioritizing conservation seed banking locations for imperiled hemlock species using multi-attribute frontier mapping

Abstract

Hemlock woolly adelgid (Adelges tsugae Annand) (HWA) is an invasive forest insect sweeping across the native range of eastern (Tsuga canadensis [L.] Carr.) and Carolina (Tsuga caroliniana Engelm.) hemlocks, threatening to severely reduce eastern hemlock extent and to push Carolina hemlock to extirpation. HWA poses a significant threat to these eastern US natives, now infesting hemlocks across 19 states and more than 400 counties. For the long-term preservation of the species, ex situ genetic resource conservation efforts such as seed collection, storage, and adelgid-resistant hemlock breeding may all be necessary. To ensure the efficient and effective application of these efforts, it will be necessary to prioritize locations within the native ranges, because it is logistically impossible to apply these efforts to all populations. To build upon 12 years of seed banking for eastern and Carolina hemlock, we applied a novel approach for incorporating multiple dissimilar data sets into a geographic prioritization of areas for the most effective and efficient conservation of genetic diversity. The approach involves integration of geographic information systems with the multi-attribute frontier mapping technique to Electronic supplementary material The online version of this article (identify locations across the ranges of these two imperiled species most in need of conservation actions. Specifically, our assessment incorporated four genetic diversity parameters, a climate component, a measure of population disjunctiveness, a measure of local hemlock abundance, and seed collection density to prioritize areas of eastern and Carolina hemlock occurrence for ex situ gene conservation. For each species, the result was a mapped index of locations prioritized by the combined significance of these factors. For eastern hemlock, this assessment assigned the highest priority to disjunct populations and to some areas within the main-body range. With Carolina hemlock, disjunct northern populations and central main-body locations received the highest prioritization. Our prioritization approach could be applied similarly to other species facing pressure from invasive pests or other environmental threats.

Loss of foundation species revisited: conceptual framework with lessons learned from eastern hemlock and whitebark pine

“…This program prioritizes genetic diversity and long‐term storage of seeds to provide material for future breeding for resistance (Hastings et al. ).…”

Forest health monitoring in transition: Evaluating insect-induced disturbances in forested landscapes at varying spatial scales

“…Simultaneously with direct effects of climate change on tree physiology and growth, indirect effects from the interactions between herbivores and their host trees may have high impacts on forestry (e.g., Logan et al 2003). Ability of different tree species to adapt to expected climate change is still very much unclear (Hamann and Wang 2006;Bolte et al 2007) and severe infestations may inhibit the adaptation (Hastings et al 2017). For example, in case of eastern hemlock (Tsuga canadensis L. Carriere) and Carolina hemlock (Tsuga caroliniana Engelmann), poor seed spreading, slow growth, and environmental preferences are hindering adaptation to climate change together with HWA infestations (Hastings et al 2017).…”

“…Ability of different tree species to adapt to expected climate change is still very much unclear (Hamann and Wang 2006;Bolte et al 2007) and severe infestations may inhibit the adaptation (Hastings et al 2017). For example, in case of eastern hemlock (Tsuga canadensis L. Carriere) and Carolina hemlock (Tsuga caroliniana Engelmann), poor seed spreading, slow growth, and environmental preferences are hindering adaptation to climate change together with HWA infestations (Hastings et al 2017). Furthermore, the low rate of adaptation of tree species to changes, compared to insects, increases forest ecosystems' vulnerability to insect pest outbreaks (García-López and Allué-Camacho 2010).…”

“…Adaptation of invasive species may be very fast during the range expansion (Butin et al 2005). Climate change influence the host species as well, especially the hemlock species (Hastings et al 2017). Combined effects of climate change and HWA infestations may further increase to risk of extinction of the eastern hemlock species (Hastings et.…”

“…2017). Adaptation of eastern and Carolina hemlock is concerning due to their slow growth rate, restricted environmental preferences, and weak seed dispersal (Hastings et al 2017). HWA may benefit from suboptimal conditions for the host species (Niemelä et al 1987;McClure 1997;Morin et al 2009).…”