HOWARTH, DIANELLA G1* and DAVID A BAUM2. 1Harvard University Herbaria, 22 Divinity Ave, Cambridge, MA 02138, USA; 2Dept of Botany, University of Wisconsin, 430 Lincoln Dr., Madison, WI, 53706, USA. - Comparing three variable nuclear intron regions and nrDNA ITS to determine the phylogenetic history and a possible hybrid origin in a closely related Hawaiian clade in Scaevola (Goodeniaceae).
Nuclear intron regions are becoming a promising source of variation in
studying closely related species for which ITS data are often
inconclusive. We have shown the phylogenetic utility of two such
introns, the third intron of Nitrate Reductase (NIA) and the second
intron of Leafy (LFY), in seven closely related Hawaiian endemic
Scaevola species (Goodeniaceae). The location of these introns
is conserved across Angiosperms, and they are often large (>1kb). In
Scaevola, these two introns contain considerably more parsimony
informative variation (2.8% in NIA and 3.6% in LFY) than in either ITS
(1.6%) or Glyceraldehyde 3-Phosphate Dehydrogenase (G3PDH) (0.4%). We
compared multiple accessions of each of seven species of
Scaevola (S. chamissoniana, S. coriacea, S. gaudichaudiana,
S. gaudichaudii, S. kilaueae, S. mollis, and S. procera)
for each of these four nuclear regions. The sequences from all four
loci were congruent across five of the seven species (excluding S.
kilaueae and S. procera). Importantly, the overall
phylogenetic relationships of these five species only became apparent
when all four regions were combined. This combined matrix demonstrates
the effectiveness of utilizing multiple regions when attempting to
elucidate closely related species relationships. Additionally, through
comparing these data we show that two species, S. procera and
S. kilaueae, are sharing alleles across taxa, resulting in
incongruence between loci. We hypothesize that S. procera is
the result of a homoploid hybridization event between S.
gaudichaudii and S. mollis.
Key words: Hawaiian Islands, nuclear introns, Scaevola (Goodeniaceae)