Crop-to-wild hybridization in cherries-Empirical evidence from Prunus fruticosa.

Lenka Macková,Tomáš Urfus,Petr Vít

doi:10.1111/eva.12677

Lenka Macková, Tomáš Urfus + Show 1 more

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https://doi.org/10.1111/eva.12677

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Abstract

Crop cultivation can lead to genetic swamping of indigenous species and thus pose a serious threat for biodiversity. The rare Eurasian tetraploid shrub Prunus fruticosa (ground cherry) is suspected of hybridizing with cultivated allochthonous tetraploid P. cerasus and autochthonous diploid P. avium. Three Prunus taxa (447 individuals of P. fruticosa, 43 of P. cerasus and 73 of P. avium) and their hybrids (198 individuals) were evaluated using analysis of absolute genome size/ploidy level and multivariate morphometrics. Flow cytometry revealed considerable differentiation in absolute genome size at the tetraploid level (average 2C of P. fruticosa = 1.30 pg, average 2C of P. cerasus = 1.42 pg, i.e., a 9.2% difference). The combination of methods used allowed us to ascertain the frequency of hybrids occurring under natural conditions in Central Europe. The morphological evaluation of leaves was based upon distance‐based morphometrics supplemented by elliptic Fourier analysis. The results provided substantial evidence for ongoing hybridization (hybrids occurred in 39.5% of P. fruticosa populations). We detected homoploid introgressive hybridization with alien P. cerasus at the tetraploid level. We also found previously overlooked but frequent triploid hybrids resulting from heteroploid hybridization with indigenous P. avium, which, however, probably represent only the F1 generation. Although both hybrids differ in ploidy, they cannot be distinguished using morphometrics. Hybrids are frequent and may endanger wild populations of genuine P. fruticosa via direct niche competition or, alternatively or in addition, via introgression at the homoploid level (i.e., genetic swamping). The cultivation of cherries thus substantially threatens the existence of genuine P. fruticosa.

Highlights

Human activities significantly contribute to the reduction in global plant diversity (e.g., Frankham, Ballou, & Briscoe, 2010)
We addressed the following questions: (a) Do ploidy level and absolute genome size correlate with patterns of morphology and delimit Prunus taxa on a large spatial scale? (b) What is the frequency of hybrids under natural conditions? and (c) May the presence of hybrids indicate that populations of P. fruticosa are under threat from hybridization? To find answers to these questions, we collected fresh plant material in natural populations, estimated their nuclear DNA content using flow cytometry and employed distance-based morphometrics together with elliptic Fourier analysis to describe the variation in short-shoot leaves
Absolute genome size/ploidy level estimation coupled with morphometrics allowed us to identify the Prunus species and hybrids concerned

Summary

Introduction

Human activities significantly contribute to the reduction in global plant diversity (e.g., Frankham, Ballou, & Briscoe, 2010). Studied phenomena such as degradation accompanied by fragmentation of natural habitats usually cause changes in the distribution of species, including extinction events or invasions (Corlett, 2016). 1996; Todesco et al, 2016). Besides invasive taxa (e.g., Hejda, Pyšek, & Jarošík, 2009), hybridization with commercial crops poses a significant threat to indigenous species (Ellstrand, Prentice, & Hancock, 1999). The potential repercussions of hybridization have been repeatedly demonstrated (Todesco et al, 2016). Even though commercial crops are ubiquitous, the topic of crop-to-wild hybridization has been addressed by relatively few empirical studies (e.g., Aerts et al, 2013; Arrigo et al, 2011)

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