Abstract Detail

Hybrids and Hybridization

Caton, Tara [1], Jordon-Thaden, Ingrid [2], Cantley, Jason [1], Martine, Chris [1].

Ex situ hybridization of two cryptically dioecious Solanum (Solanaceae) species from NT Australia clarifies vague species boundaries.

Botanists have recognized problematic species boundaries among the functionally dioecious spiny solanums of northern Australia for decades. Of the ca. 15 species in this group, the Northern Territory sandstone endemic Solanum asymmetriphyllum stood out as one of the most morphologically distinct until its sister species, S. sejunctum, described in 2006. While molecular work supports that these two taxa are likely sister (and not the same) species, our work recently discovered that interspecific crosses leads to fruit and seed set, and a high germination rate for an F₁ hybrid generation. This study investigated the F₁ hybrids and made morphological and genetic comparisons of the two parent species plus the two hybrid crosses of opposite maternal parentage. Morphometric analyses included vegetative and reproductive characteristics and determined an equal number of characters favoring both parental species, exhibiting an intermediate hybrid morphology, or possessing a unique hybrid effect. Genetic analyses included a species-determining restriction enzyme digestion pattern assay of the sporopollenin precursor gene CYP703, chromosomal ploidy level determination, and use of Genomic in situ Hybridization (GISH) to determine patterns of genomic inheritance. The species-determining assay determined that the two species are distinct, the hybrids have a mixed pattern of digestion, and an included herbarium sample of a putative wild occurring hybrid (labeled as S. asymmetriphyllum, but resembling an intermediate form with S. sejunctum) suggests that wild hybrids can occur or a new species should be realized. Chromosomal squashes indicated that both species and all hybrids maintain the same base number (2n=24) and that allopolyploidy had not occurred. Results from GISH analyses showed a mixed pattern of genomic inheritance on chromosomes. All of these data better clarify the evolutionarily close relationship between S. asymmetriphyllum and S. sejunctum and solidify their position as distinct species. The ability for the two species to form hybrid offspring into the F₁ and F₂ generations suggests that they are recently diverged; and some outcomes of the study infer that the speciation of S. sejunctum may have occurred as a result of a single population becoming geographically isolated during periods of climate change via a vicariance event or some long distance dispersal event. Defining these species boundaries better guide conservation efforts for their small population sizes, especially of S. sejunctum, which only occurs isolated on one sandstone monolith.

1 - Bucknell University, Biology Department, 1 Dent drive, Lewisburg, PA, 17837
2 - University of California Berkeley, 1001 Valley Life Sciences Building, Berkeley, CA, 94720

Keywords:
Hybrids
hybridization
Australia
genetics
Solanum.

Presentation Type: Poster
Session: P, Hybrids and Hybridization Posters
Location: Exhibit Hall/Savannah International Trade and Convention Center
Date: Monday, August 1st, 2016
Time: 5:30 PM This poster will be presented at 6:15 pm. The Poster Session runs from 5:30 pm to 7:00 pm. Posters with odd poster numbers are presented at 5:30 pm, and posters with even poster numbers are presented at 6:15 pm.
Number: PHB002
Abstract ID:246
Candidate for Awards:Genetics Section Poster Award