Hybridization of Tamarix ramosissima and T. chinensis (saltcedars) with T. aphylla (athel) (tamaricaceae) in the southwestern USA dertermined from DNA sequence data

Morphological intermediates between Tamarix ramosissima or T. chinensis (saltcedars) and T. aphylla (athel) were found recently in three locations in the southwestern USA, and were assumed to be hybrids or a previously unreported species. We sequenced chloroplast and nuclear DNA from putative parental and hybrid morphotypes and hybrid status of morphological intermediates was supported. Chloroplast data suggest that the seed source for these hybrids is T. aphylla. Invasive T. aphylla genotypes found in Australia match those found in the USA. Seed was collected from one of the hybrids, and a low percentage of it was viable. This hybrid combination has not been previously reported in the USA or the native ranges of the species. Although populations of this novel Tamarix hybrid appear to be uncommon at present, both parental species are considered invasive (saltcedars in North America; athel in Australia), and it is possible that more aggressive hybrid genotypes could be produced. Therefore, natural resource managers concerned with the potential spread of non-native species should be aware of the existence of these plants and monitor their future spread.