Abstract Detail

Systematics

Giraldo, Giovanny [1], Lemmon, Emily [2], Lemmon, Alan R. [2], Cameron, Ken [3].

Genome Size of Vanilloideae, and its Phylogeny Inferred from NextGen Anchored Phylogenomics.

Phylogenetic relationships among genera in tribe Vanilleae (Vanilloideae) remain elusive among various analyses that have addressed this tribe specifically or focused at the family level. One of the reasons why phylogenetic reconstruction of this group has been so difficult is that five of the nine genera of the tribe are achlorophyllous mycoheterotrophs (e.g., unplaced Lecanorchis), and hence are poorly or not at all represented in molecular studies that relied heavily on plastid loci. Interestingly, even the relationships among some photosynthetic genera remain unresolved (e.g., the relationship between South American Epistephium and the clade of New Caledonian endemic genera Clematepistephium+Eriaxis) Through the use of Anchored Phylogenomics via Next Generation DNA Sequencing, we have inferred the phylogenetic relationships of most genera in the Vanilleae tribe using 9261 bp of data from 23 low copy nuclear markers. Our results seem to indicate that Epistephium forms a clade with Clematepistephium + Eriaxis, as well as Lecanorchis. Most earlier studies showed Epistephium to be sister to the entire tribe. Although the relationship of Epistephium to the New Caledonian taxa has been suggested before, this is the first time such a relationship is recovered with high support. The placement of Lecanorchis in the group reflects what would be expected based on the morphology of the flower, as it has a calyculus, an overgrowth of the top of the ovary that is also present in the other three genera of this clade. In addition to phylogenetic reconstruction, we also estimated genome size for most genera of Vanilloideae, since published reports for the subfamily to date have been entirely from Vanilla. Among angiosperms, orchids have the most variable genome size, ranging from 0.33 pg in Trichocentrum maduroi to 55.4 pg in Pogonia ophioglossoides, a member of Vanilloideae. Not only does the subfamily have the largest known genome, but it also contains the largest chromosome number reported for Orchidaceae: Epistephium lucidum (2n= ca. 170). Here we report the genome size for several additional members of Vanilloideae: several species of Vanilla Clematepistephium smilacifolium, Eriaxis rigida, Epistephium duckei, mycoheterothroph Erythrorchis cassythoides, and others. An attempt to obtain C-values from the mycoheterothrophs Pseudovanilla foliata and Lecanorchis kiusiana failed to produce reliable data. Our data shows that there is at least an 18-fold range of genome size in Vanilloideae, from 2.985 pg for Eriaxis rigida to 55.4 pg in Pogonia ophioglossoides. The implications of these findings will be discussed.

1 - University of Wisconsin-Madison, Botany, 430 Lincoln Dr., Madison, WI, 53706, USA
2 - Florida State University
3 - University Of Wisconsin - Madison, Botany, 430 Lincoln Drive, Madison, WI, 53706, USA

Keywords:
Orchidaceae
Systematics
Phyllogenetics.

Presentation Type: Oral Paper
Session: 31, Cooley Awards II
Location: 201/Savannah International Trade and Convention Center
Date: Tuesday, August 2nd, 2016
Time: 1:45 PM
Number: 31002
Abstract ID:681
Candidate for Awards:George R. Cooley Award