Using Landscape Genetics Simulations for Planting Blister Rust Resistant Whitebark Pine in the US Northern Rocky Mountains.

Erin L Landguth,Mary F Mahalovich,Zachary A Holden,Samuel A Cushman

doi:10.3389/fgene.2017.00009

Abstract

Recent population declines to the high elevation western North America foundation species whitebark pine, have been driven by the synergistic effects of the invasive blister rust pathogen, mountain pine beetle (MPB), fire exclusion, and climate change. This has led to consideration for listing whitebark pine (WBP) as a threatened or endangered species under the Endangered Species Act, which has intensified interest in developing management strategies for maintaining and restoring the species. An important, but poorly studied, aspect of WBP restoration is the spatial variation in adaptive genetic variation and the potential of blister rust resistant strains to maintain viable populations in the future. Here, we present a simulation modeling framework to improve understanding of the long-term genetic consequences of the blister rust pathogen, the evolution of rust resistance, and scenarios of planting rust resistant genotypes of whitebark pine. We combine climate niche modeling and eco-evolutionary landscape genetics modeling to evaluate the effects of different scenarios of planting rust-resistant genotypes and impacts of wind field direction on patterns of gene flow. Planting scenarios showed different levels for local extirpation of WBP and increased population-wide blister rust resistance, suggesting that the spatial arrangement and choice of planting locations can greatly affect survival rates of whitebark pine. This study presents a preliminary, but potentially important, framework for facilitating the conservation of whitebark pine.

Highlights

Whitebark pine (WBP; Pinus albicaulis) is one of the most intensively studied North American conifers, in part due to its unique relationship with the grizzly bear (Ursus arctos horribilis), Clark’s nutcracker (Nucifraga columbiana), and over 20 other wildlife species (Lorenz et al, 2008), which depend on its seeds for food; it is considered a keystone and foundation species in high elevation forests within its range
One of the primary threats associated with WBP decline is white pine blister rust (WPBR)-an invasive fungal pathogen introduced to the Pacific Northwest of North America around 1910 (Brar et al, 2015)
We developed correlative niche models (CNM; aka species distribution or habitat suitability models; Thuiller et al, 2005; Elith and Leathwick, 2009) for WBP and WPBR using occurrence records to develop a probabilistic model of occurrence based on statistical relationships with climatic, topographic and biophysical variables

Summary

Introduction

Whitebark pine (WBP; Pinus albicaulis) is one of the most intensively studied North American conifers, in part due to its unique relationship with the grizzly bear (Ursus arctos horribilis), Clark’s nutcracker (Nucifraga columbiana), and over 20 other wildlife species (Lorenz et al, 2008), which depend on its seeds for food; it is considered a keystone and foundation species in high elevation forests within its range. Recent declines associated with the spread of mountain pine beetle (MPB; Dendroctonus ponderosae), and the introduced invasive fungal pathogen white pine blister rust (WPBR; Cronartium ribicola) have led to consideration for listing the species. One of the primary threats associated with WBP decline is WPBR-an invasive fungal pathogen introduced to the Pacific Northwest of North America around 1910 (Brar et al, 2015). In the US Northern Rockies, offspring of over 1300 phenotypic selections are under evaluation in support of active restoration by planting proven, rust-resistant seedlings which have a combination of no-spot, needle-shed, bark reaction and shoot resistance mechanisms (Mahalovich and Dickerson, 2004; Greater Yellowstone Coordinating Committee whitebark pine Subcommittee, 2011; Keane et al, 2012, 2016)

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