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  • Author or Editor: Erin Tripp x
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The potential for natural hybridization to occur between non-native, invasive species and closely related native species is of interest to biologists, conservationists, and land managers, particularly in regions such as the southeastern United States where numerous non-native species have become serious environmental pests. To explore this potential between the invasive plant species Ruellia simplex and the closely related, sympatric Ruellia caroliniensis, we conducted a study of reproductive crossability and hybrid viability. Results indicate that the production of interspecific hybrids is possible, but only in one direction (i.e., with R. caroliniensis as the maternal parent). Artificial hybrids were weak, slow-growing, and sterile. These data suggest that it is unlikely that R. caroliniensis × R. simplex hybrids could invade the gene pool of native R. caroliniensis. We also characterized hybrids at the molecular level by sequencing parents plus F1 progeny for the nuclear ribosomal internal transcribed spacer (ITS) + 5.8S region. All hybrid genotypes formed a strongly supported clade with the maternal parent, Ruellia caroliniensis. Within this clade, hybrid individuals were not differentiable from maternal genotypes. We then examined general plant morphology of hybrid individuals and the two parents. Unlike results from the molecular characterization, there was a strong signal of hybrid intermediacy from this morphological work. We conclude that morphology but not molecular sequence data (from nrITS) can be used to distinguish the two parents and their F1 hybrids.

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