Genetic Variability of Alnus cordata (Loisel.) Duby Populations and Introgressive Hybridization with A. glutinosa (L.) Gaertn. in Southern Italy: Implication for Conservation and Management of Genetic Resources

Claudia Mattioni,Marcello Cherubini,Isacco Beritognolo,Alberto Battistelli,Simone Castellana,Francesca Chiocchini,Fiorella Villani

doi:10.3390/f12060655

Claudia Mattioni, Marcello Cherubini + Show 5 more

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https://doi.org/10.3390/f12060655

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Abstract

Alnus cordata (Loisel.) Duby (Neapolitan alder) is an endemic tree species with a restricted distribution range, limited to Corsica and southern Italy. The economic value of its wood, its rapid growth, the tolerance to drought stress and the nitrogen fixation capacity make A. cordata an excellent candidate for breeding, as well as for conservation and management of genetic resources. In this context, we evaluated the genetic variability of southern Italy populations and verified the hybridization capacity with the simpatric species A. glutinosa (L.) Gaertn. Eight pure A. cordata populations, two pure A. glutinosa populations and six mixed A. cordata/A. glutinosa populations located in southern Italy were analyzed using seven microsatellite markers. A low genetic diversity within and among populations was observed, but no inbreeding effects were evident. A variable frequency of F2 interspecific hybrids was observed in most of the mixed populations and few backcross individuals were scored. These results suggest a limited capacity of hybrid individuals to cross back with the parent species, reducing the risk of genetic pollution of A. cordata. This work provides meaningful knowledge for the conservation and management of the endemic species A. cordata, which represents a valuable source of biodiversity to be conserved.

Highlights

Hybridization plays an important role in evolution, speciation and even species extinction [1]
Our study focused on A. cordata, an endemic species in southern Italy, we investigated its genetic variability and the introgression with A. glutinosa, a wide distributed species, which coexist in the same area
We evaluated the genetic diversity of the endemic A. cordata populations in southern

Summary

Introduction

Hybridization plays an important role in evolution, speciation and even species extinction [1]. An increased rate of hybridization with related and more abundant species could represent a threat to the survival of rare and endemic species. Extensive hybridization of a widely-distributed species with endemic ones may result in “genetic swamping” or “demographic swamping” and can wipe out the endemic species [2,3,4]. Several studies have documented the decline of rare plant species due to hybridization phenomena [5,6,7,8,9]. The genus Alnus (Mill.) (Betulaceae), commonly referred as alder, includes monoecious trees and shrubs widely-distributed throughout the temperate zone of the northern. Studies on population genetics and phylogeography have been carried out on different Alnus species, i.e., A. rubra Bong [10,11], A. maritima (Marshall) Muhl. Studies on population genetics and phylogeography have been carried out on different Alnus species, i.e., A. rubra Bong [10,11], A. maritima (Marshall) Muhl. ex

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