Turning Up the Heat on a Hotspot: DNA Barcodes Reveal 80% More Species of Geometrid Moths along an Andean Elevational Gradient.

Gunnar Brehm,Robert K Colwell,Paul D N Hebert,Marc-Oliver Adams,Lars Möckel,Florian Bodner,Konrad Fiedler,Katrin Friedemann,Jesus E Maldonado

doi:10.1371/journal.pone.0150327

Abstract

We sampled 14,603 geometrid moths along a forested elevational gradient from 1020–3021 m in the southern Ecuadorian Andes, and then employed DNA barcoding to refine decisions on species boundaries initially made by morphology. We compared the results with those from an earlier study on the same but slightly shorter gradient that relied solely on morphological criteria to discriminate species. The present analysis revealed 1857 putative species, an 80% increase in species richness from the earlier study that detected only 1010 species. Measures of species richness and diversity that are less dependent on sample size were more than twice as high as in the earlier study, even when analysis was restricted to an identical elevational range. The estimated total number of geometrid species (new dataset) in the sampled area is 2350. Species richness at single sites was 32–43% higher, and the beta diversity component rose by 43–51%. These impacts of DNA barcoding on measures of richness reflect its capacity to reveal cryptic species that were overlooked in the first study. The overall results confirmed unique diversity patterns reported in the first investigation. Species diversity was uniformly high along the gradient, declining only slightly above 2800 m. Species turnover also showed little variation along the gradient, reinforcing the lack of evidence for discrete faunal zones. By confirming these major biodiversity patterns, the present study establishes that incomplete species delineation does not necessarily conceal trends of biodiversity along ecological gradients, but it impedes determination of the true magnitude of diversity and species turnover.

Highlights

Changing patterns in plant and animal communities along elevational gradients have interested biogeographers and macroecologists since Humboldt’s pioneering studies in the Andes 200 years ago
Our study evaluates the impact of using differing species delineation methods to examine patterns of species richness and turnover in geometrid moths along an elevational gradient in Ecuador
This study reinforces earlier evidence for the unmatched species richness of geometrid moths in southern Ecuador. [47] recognized 1266 species in southern Ecuador based on morphological studies, while [8] raised the total to 1445 putative species

Summary

Introduction

Changing patterns in plant and animal communities along elevational gradients have interested biogeographers and macroecologists since Humboldt’s pioneering studies in the Andes 200 years ago. It was long assumed that species richness would decline monotonically with elevation, reflecting decreases in temperature and primary productivity [1] species richness has been shown to peak at intermediate elevations in 70% of past investigations [1, 2]. The dominance of hump-shaped richness patterns was long overlooked due to confounding area effects [3] and because richness often peaks at relatively low elevations but not at the lowest sites as, for example, in dung beetles [4] and ants [5]. [6] found a different pattern in the Andes of southeastern Ecuador: Richness and diversity of geometrid moths showed no change along an elevational gradient from 1020m to 2677m. It has become evident that the study area in Ecuador represents, to date, the most species-rich region for geometrid moths worldwide, with the latest regional count at 1445 species [8]

Methods

Results

Conclusion