Patterns of Diversity in the Symbiotic Mite Assemblage of the Mountain Pine Beetle, Dendroctonus Ponderosae Hopkins

Sneha Vissa,Danielle Malesky,Javier E Mercado,Richard W Hofstetter,Wayne Knee,Maya L Evenden,Boyd A Mori,Derek A Uhey

doi:10.3390/f11101102

Abstract

The mountain pine beetle, Dendroctonus ponderosae (Coleoptera: Scolytinae), is an economically important bark beetle species with a wide geographic range spanning from the southwestern United States into northern Canada. This beetle causes extensive tree mortality to 13 pine species. Mites (Acari) are common and abundant symbionts of mountain beetles that may influence their fitness through positive and negative interactions. We present a unique assessment of the mite associates of mountain pine beetles using measures of alpha and beta diversity. We sampled phoretic mites from five beetle populations: Arizona, Colorado, South Dakota, Utah (USA), and Alberta (Canada) that varied in host tree species, local climate, and beetle population level. We collected 4848 mites from 8 genera and 12 species. Fifty to seventy percent of beetles carried mites in flight with the highest mite loads occurring in middle and southern populations; decreasing in northern populations. Mite assemblages (i.e., both richness and composition) varied along a south to north latitudinal gradient and were driven by species turnover (i.e., species replacement). Differences in mite composition increased with distance between populations. We discuss climatic variation, environmental filtering, and host tree differences as factors that could affect differences in mite composition between beetle populations and discuss implications for functional shifts. Our results could represent a model for estimating diversity patterns of mite symbionts associated with other major insect pests in coniferous forest systems.

Highlights

Forests face increased pressure from insect pests, such as bark beetles (Coleoptera: Scolytinae) [1,2,3]
A total of 4848 mites were collected across all sampled mountain pine beetle populations (Table 1)
Distant mountain pine beetle populations have different symbiotic mite assemblages despite some commonalities reflected in species overlap

Summary

Introduction

Forests face increased pressure from insect pests, such as bark beetles (Coleoptera: Scolytinae) [1,2,3]. Bark beetle impacts can be severe as they actively damage tree phloem tissue and vector phytopathogens, resulting in large events of tree mortality [4,5]. Forests 2020, 11, 1102 beetle, Dendroctonus ponderosae Hopkins, has been responsible for tree mortality across more than 30 million hectares of forest in western North America in the last decade [4,5]. Constrained by temperature, a warming climate has allowed the mountain pine beetle to expand its habitable range to higher elevations and its geographic distribution northward [6,7,8]. The mountain pine beetle colonizes 13 pine species of which it most commonly attacks lodgepole pine Lawson) [9], and more recently, jack pine (Pinus banksiana Lamb.) [7,10]

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