Genetic differences among Cedrela odorata sites in Bolivia provide limited potential for fine-scale timber tracing

Kathelyn Paredes-Villanueva,Frans Bongers,Ivo Laros,Jan Bovenschen,Pieter A Zuidema,G Arjen De Groot

doi:10.1007/s11295-019-1339-4

Kathelyn Paredes-Villanueva, Frans Bongers + Show 4 more

Open Access

https://doi.org/10.1007/s11295-019-1339-4

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Abstract

Illegal trade of tropical timber leads to biodiversity and economic losses worldwide. There is a need for forensic tools that allow tracing the origin of timber and verifying compliance with international and national regulations. We evaluated the potential for genetic tracing of Cedrela odorata, one of the most traded neotropical timbers, within Bolivia. Using a set of seven microsatellites (SSRs), we studied the spatial distribution and genetic diversity and tested whether populations show sufficient genetic discrimination for timber tracing at a national level. Cambium and leaves were sampled from 81 C. odorata trees from three sites, at 268–501-km distance. To explore genetic differentiation, Bayesian clustering and principal component analysis (PCA) were employed. To infer the origin of samples, we conducted kernel discriminant analysis (KDA) based on a PCA that included all alleles and a manual assessment of site-unique alleles. The PCA showed three distinct genetic clusters, but only one of them corresponded with one of the sampled sites. The KDA based on allele frequency had a 33.7% mean classification error, with a considerably lower error (8.2%) for the site which matched with one genetic cluster. The blind test on unique alleles led to a similar classification error (30%). The occurrence of multiple genetic clusters within sites suggests that Bolivian C. odorata populations contain several parental lines, resulting in limited potential for forensic tracing at a national level. Based on our findings, we recommend for additional sampling across the spatial range of C. odorata within the country to support the development of forensic techniques for this species.

Highlights

Illegal logging and illegal timber trade is a worldwide environmental problem, resulting in biodiversity and economic loss
We addressed the following questions: (1) Do the study sites represent distinct genetic groups and follow a spatial pattern across the species distribution? (2) To what extent does this genetic structure allow successful timber tracing at regional and nationwide scale? We expected to find a pattern of isolation by distance in which genetic differentiation increases with geographical distance, allowing us to differentiate between sites of origin (Wright 1943)
The mean observed heterozygosity (Ho) was lower than the mean He in all three sampling sites, resulting in a positive fixation index (Fis) for especially Cobija and Rurrenabaque (0.14 and 0.11, respectively), suggesting inbreeding or Wahlund effects due to spatial genetic structure within populations. This is in line with the results of the STRUCTURE analysis (Figs. 2 and 3; blue, red, and yellow dots), showing the presence of multiple genetic clusters in these populations

Summary

Introduction

Illegal logging and illegal timber trade is a worldwide environmental problem, resulting in biodiversity and economic loss. The control of harvesting and trade of timber species has been carried out based on certificates with declared origin. These systems have been weakened by the frequent use of false declarations of species and geographic origin as these documents are prone to be falsified. To effectively combat fraud in illegal logging and trade, there is a need for forensic techniques that use timber properties as DNA fingerprint to independently verify the origin in both local and international markets (Degen 2007; UNODC 2016)

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