The hidden diversity of the potato cyst nematode Globodera pallida in the south of Peru.

Romain Thevenoux,Eric Grenier,Laurent Folcher,Magali Esquibet,Didier Fouville,Josselin Montarry

doi:10.1111/eva.12896

Abstract

Our knowledge of the diversity of potato cyst nematodes in their native areas still remains patchy and should be improved. A previous study based on 42 Peruvian Globodera pallida populations revealed a clear south to north phylogeographic pattern, with five well‐supported clades and maximum diversity observed in the south of Peru. In order to investigate this phylogeographic pattern more closely, we genotyped a larger collection of Peruvian populations using both cathepsin L gene sequence data and a new set of 13 microsatellite loci. Using different genetic analyses (STRUCTURE, DAPC), we consistently obtained the same results that led to similar conclusions: the presence of a larger genetic diversity than previously known suggesting the presence of cryptic species in the south of Peru. These investigations also allowed us to clarify the geographic borders of the previously described G. pallida genetic clades and to update our knowledge of the genetic structure of this species in its native area, with the presence of additional clades. A distance‐based redundancy analysis (dbRDA) was also carried to understand whether there was a correlation between the population genetic differentiation and environmental conditions. This analysis showed that genetic distances observed between G. pallida populations are explained firstly by geographic distances, but also by climatic and soil conditions. This work could lead to a revision of the taxonomy that may have strong implications for risk assessment and management, especially on a quarantine species.

Highlights

Species delimitation is still a challenging area in the field of biology and more precisely in taxonomy and systematic science
Previous investigations carried out on G. pallida populations sampled along the Andean Cordillera in Peru have revealed a phylogeographic pattern from south to north, with five distinct clades (Picard, Sempere, & Plantard, 2007), and high nucleotide divergence (10%–11% based on cytochrome B sequencing) between populations belonging to the southern and northern clades (Picard et al, 2007)
As previously shown, a clear genetic structure in this area, linked to the geographic and pedoclimatic conditions

Summary

| INTRODUCTION

Species delimitation is still a challenging area in the field of biology and more precisely in taxonomy and systematic science. Previous investigations carried out on G. pallida populations sampled along the Andean Cordillera in Peru have revealed a phylogeographic pattern from south to north, with five distinct clades (named I–V) (Picard, Sempere, & Plantard, 2007), and high nucleotide divergence (10%–11% based on cytochrome B sequencing) between populations belonging to the southern and northern clades (Picard et al, 2007) This first study on the genetic diversity of G. pallida was conducted on a limited population set (44 along a 3000-km transect (Picard et al, 2007; Plantard et al, 2008)), and made use of a set of seven microsatellite loci available at that time. Thanks to the increase in the number of populations from South Peru investigated and to the use of two different genotyping tools with different tempos of evolution, our objectives were (a) to explore the geographic distribution of G. pallida, G. rostochiensis or G. ellingtonae in South Peru and (b) to reinvestigate more in-depth the genetic diversity of G. pallida in its native area

| MATERIALS AND METHODS

Findings

| DISCUSSION