Carpological analysis of Phoenix (Arecaceae): contributions to the taxonomy and evolutionary history of the genus

Authors: RIVERA, DIEGO - Universidad De Murcia; OBON, CONCEPCION - Miguel Hernandez University; GARCIA-ARTEAGA, JOAQUIN - Miguel Hernandez University; EGEA, TERESA - Miguel Hernandez University; ALCARAZ, FRANCISCO - Universidad De Murcia; LAGUNA, EMILIO - Instituto Nacional De Investigaciones Forestales Y Agropecuarias (INIFAP); CARRENO, ENCARNA - Universidad De Murcia; JOHNSON, DENNIS - Consultant; Krueger, Robert; DELGADILLO, JOSE - Universidad Autonoma De Baja California; RIOS, SEGUNDO - Universidad De Alicante

Submitted to: Botanical Journal of the Linnean Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/23/2014
Publication Date: 4/22/2014
Publication URL: http://handle.nal.usda.gov/10113/60753
Citation: Rivera, D., Obon, C., Garcia-Arteaga, J., Egea, T., Alcaraz, F., Laguna, E., Carreno, E., Johnson, D., Krueger, R., Delgadillo, J., Rios, S. 2014. Carpological analysis of Phoenix (Arecaceae): contributions to the taxonomy and evolutionary history of the genus. Botanical Journal of the Linnean Society. 175:74-122.

Interpretive Summary: Seed morphology of modern. archaeological, and fossil Phoenix species were studied in order to assess the taxonomic usefulness for studying systematics and evolutionary history of the genus. Nine modern Phoenix species had characteristic seeds and were assigned to morphotypes, whereas other modern species could not be differentiated by seed characteristics alone. There was a continuum between the fossil, archaeological, and modern Phoenix species. Archaeological and some fossil Phoenix species could be assigned to modern morphotype groups. Some fossil species fell into the same morphotype as P dactylifera. The analysis suggests that there were two ancestral groups of P dactylifera, one in the Eastern Mediterranean region and the other in the Western Mediterranean region.

Technical Abstract: The main purpose of this study was, first, to analyze the morphology of seeds of Phoenix spp. and relevant cultivars and to assess the taxonomic value of the information generated as a means of studying the systematics and evolutionary history of the genus Phoenix. We then analyzed seed morphological diversity in P. dactylifera, supported by morphotypes shared with fossil and/or archaeological materials, to advance the knowledge of the origins, history and biogeography of one of the most important cultivated palm species. The other objective was to develop a methodology for assigning different commercial seed samples and archaeological materials to determined morphotypes as a tool for their identification at the species level. Three hundred and sixty-four seed samples (3920 seeds) were analyzed: 304 samples of modern Phoenix spp. (including five herbarium type specimens and eight type icons), 51 archaeological samples and nine fossil seed samples and subsamples. Information was systematized in a crude matrix with 364 units representing seed samples and 67 descriptors. Descriptors are frequencies, in percentage, for each of the 41 qualitative states and of the 26 classes that were recognized for the quantitative parameters. Analyses proceeded sequentially, starting with modern samples consisting of type specimens and botanically verified specimens. Eight species show characteristic seeds and are clearly assigned to morphotypes [P. acaulis, P. canariensis s.s., P. paludosa, P. reclinata, P. roebelenii, P. rupicola, P. sylvestris and P. theophrasti (excluding populations from Datça, Turkey)]; the other taxa are not clearly separated on the basis of the seed morphology alone. In parallel, fossil and archaeobotanical samples were analyzed. There is no clear separation between fossil and archaeological samples, between different periods of the archaeological samples or geographical origins. Combination of modern, fossil and archaeological seed results in the same analysis revealed that it is possible to allocate archaeological and fossil materials to morphotypes shared with modern living Phoenix spp. All archaeobotanical samples could be classified in groups with modern seed samples. The assignment of archaeobotanical samples was made, mainly, to morphotypes of P. dactylifera. However, some samples were assigned to morphotypes of P. reclinata, P. caespitosa, P. atlantica, P. theophrasti, P. pusilla and P. canariensis. Archaeological seeds were not allocated to group 19, containing the samples of P. sylvestris, P. iberica and the Miocene fossil P. bohemica. It appears that species such as P. theophrasti, P. canariensis, P. caespitosa and P. reclinata formerly had a much wider area of distribution. The morphology of two of the three Eocene samples (Phoenicites occidentalis and Phoenix hercynica) is that of P. dactylifera. Attribution and dating of these samples need to be carefully reviewed. Apparently the great diversity of P. dactylifera date morphotypes during the Neolithic was followed, during the Chalcolithic and the Bronze Age, by a remarkable constriction (bottleneck) in terms of morphological variability, which slowly recovered from the Iron Age onwards. With the currently available evidence, we cannot exclude a group ancestral to P. dactylifera in the Persian Gulf, related to the eastern chlorotype. In parallel, another group ancestral to P. dactylifera may exist in the western Mediterranean, including P. iberica, related to the western chlorotype.