Phylogenetic analysis of seven WRKY genes across the palm subtribe Attaleinae (Arecaceae) [corrected] identifies Syagrus as sister group of the coconut.
BACKGROUND
The Cocoseae is one of 13 tribes of Arecaceae subfam. Arecoideae, and contains a number of palms with significant economic importance, including the monotypic and pantropical Cocos nucifera L., the coconut, the origins of which have been one of the "abominable mysteries" of palm systematics for decades. Previous studies with predominantly plastid genes weakly supported American ancestry for the coconut but ambiguous sister relationships. In this paper, we use multiple single copy nuclear loci to address the phylogeny of the Cocoseae subtribe Attaleinae, and resolve the closest extant relative of the coconut.


RESULTS
We present the results of combined analysis of DNA sequences of seven WRKY transcription factor loci across 72 samples of Arecaceae tribe Cocoseae subtribe Attaleinae, representing all genera classified within the subtribe, and three outgroup taxa with maximum parsimony, maximum likelihood, and Bayesian approaches, producing highly congruent and well-resolved trees that robustly identify the genus Syagrus as sister to Cocos and resolve novel and well-supported relationships among the other genera of the Attaleinae. We also address incongruence among the gene trees with gene tree reconciliation analysis, and assign estimated ages to the nodes of our tree.


CONCLUSIONS
This study represents the as yet most extensive phylogenetic analyses of Cocoseae subtribe Attaleinae. We present a well-resolved and supported phylogeny of the subtribe that robustly indicates a sister relationship between Cocos and Syagrus. This is not only of biogeographic interest, but will also open fruitful avenues of inquiry regarding evolution of functional genes useful for crop improvement. Establishment of two major clades of American Attaleinae occurred in the Oligocene (ca. 37 MYBP) in Eastern Brazil. The divergence of Cocos from Syagrus is estimated at 35 MYBP. The biogeographic and morphological congruence that we see for clades resolved in the Attaleinae suggests that WRKY loci are informative markers for investigating the phylogenetic relationships of the palm family.
Meerow
Alan W
AW
USDA-ARS-SHRS-National Germplasm Repository, Miami, Florida, United States of America. alan.meerow@ars.usda.gov
Noblick
Larry
L
Borrone
James W
JW
Couvreur
Thomas L P
TL
Mauro-Herrera
Margarita
M
Hahn
William J
WJ
Kuhn
David N
DN
Nakamura
Kyoko
K
Oleas
Nora H
NH
Schnell
Raymond J
RJ
D028023:Arecaceae / Q000235:genetics*; D001499:Bayes Theorem; D005075:Biological Evolution; D003059:Cocos / Q000235:genetics*; D004247:DNA / Q000378:metabolism; D017343:Genes, Plant; D005843:Geography; D016013:Likelihood Functions; D018895:Microsatellite Repeats; D008957:Models, Genetic; D015233:Models, Statistical; D010802:Phylogeny; D018515:Plant Leaves / Q000378:metabolism; D017422:Sequence Analysis, DNA; D014157:Transcription Factors / Q000378:metabolism
D014157:Transcription Factors; D004247:DNA