Ground-Dwelling Arthropod Communities of a Sky Island Mountain Range in Southeastern Arizona, USA: Obtaining a Baseline for Assessing the Effects of Climate Change.

Wallace M Meyer,Jeffrey A Eble,Paul E Marek,W Eugene Hall,Jeff Henkel,Ryan Mcinroy,Sandra L Brantley,Reilly B Mcmanus,Kimberly Franklin,Wendy Moore,Carl A Olson,Emmanuel M Bernal Loaiza,Richard C Brusca,Darren Ward

doi:10.1371/journal.pone.0135210

Abstract

The few studies that have addressed past effects of climate change on species distributions have mostly focused on plants due to the rarity of historical faunal baselines. However, hyperdiverse groups like Arthropoda are vital to monitor in order to understand climate change impacts on biodiversity. This is the first investigation of ground-dwelling arthropod (GDA) assemblages along the full elevation gradient of a mountain range in the Madrean Sky Island Region, establishing a baseline for monitoring future changes in GDA biodiversity. To determine how GDA assemblages relate to elevation, season, abiotic variables, and corresponding biomes, GDA were collected for two weeks in both spring (May) and summer (September) 2011 in the Santa Catalina Mountains, Arizona, using pitfall traps at 66 sites in six distinct upland (non-riparian/non-wet canyon) biomes. Four arthropod taxa: (1) beetles (Coleoptera), (2) spiders (Araneae), (3) grasshoppers and crickets (Orthoptera), and (4) millipedes and centipedes (Myriapoda) were assessed together and separately to determine if there are similar patterns across taxonomic groups. We collected 335 species of GDA: 192/3793 (species/specimens) Coleoptera, 102/1329 Araneae, 25/523 Orthoptera, and 16/697 Myriapoda. GDA assemblages differed among all biomes and between seasons. Fifty-three percent (178 species) and 76% (254 species) of all GDA species were found in only one biome and during only one season, respectively. While composition of arthropod assemblages is tied to biome and season, individual groups do not show fully concordant patterns. Seventeen percent of the GDA species occurred only in the two highest-elevation biomes (Pine and Mixed Conifer Forests). Because these high elevation biomes are most threatened by climate change and they harbor a large percentage of unique arthropod species (11–25% depending on taxon), significant loss in arthropod diversity is likely in the Santa Catalina Mountains and other isolated mountain ranges in the Southwestern US.

Highlights

Rising concentrations of greenhouse gasses in the atmosphere are leading to increasing global temperatures and changes in the hydrological cycle [1]
High elevation montane species, which are often endemic to a single mountain range, are vulnerable to climate change [4,5,6,7] because populations tend to be small, isolated from other source populations, climatically restricted, and unable to move to higher elevations upon reaching the summit of the mountain [8,9,10]
For each arthropod group we address the following questions: (1) How are ground-dwelling arthropod (GDA) assemblages distributed in relation to biomes? (2) How do assemblages vary between spring/May and summer/September? (3) What proportion of the species is restricted to a single biome? And, (4) What proportion of the species is only found in high elevation biomes where populations have a higher probability of extinction due to climate change? This is the first detailed investigation of GDA distributions in the Catalina Mountains, or any Sky Island range in the Southwest

Summary

Introduction

Rising concentrations of greenhouse gasses in the atmosphere are leading to increasing global temperatures and changes in the hydrological cycle [1]. High elevation montane species, which are often endemic to a single mountain range, are vulnerable to climate change [4,5,6,7] because populations tend to be small, isolated from other source populations, climatically restricted, and unable to move to higher elevations upon reaching the summit of the mountain [8,9,10]. As a result, these species and populations are especially prone to extirpation or extinction. Documenting the diversity and distribution of montane species, which establishes a baseline for future comparisons and studies that track how species respond to climate change, is vital to making informed decisions concerning the preservation and management of biodiversity

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Results

Conclusion