Molecular Systematics of the Cashew Family (Anacardiaceae)

• Main Author: Pell, Susan Katherine
• Other Authors: Michael Stine
• Format: Others
• Language: en
• Published: LSU 2004
• Subjects: Plant Biology (Biological Sciences)
• Online Access: http://etd.lsu.edu/docs/available/etd-04152004-101232/

Anacardiaceae Lindl., the cashew family, is an economically important, primarily pantropically distributed family of 82 genera and over 700 species. This family is well known for its cultivated edible fruits and seeds (mangos, pistachios, and cashews), dermatitis causing taxa (e.g., Comocladia, Metopium, Semecarpus, Toxicodendron, etc.), and lacquer plants (Toxicodendron and Gluta spp.). The taxonomy of Anacardiaceae has not been thoroughly investigated since Engler established the currently used five tribal classification system over 100 years ago. This study evaluated evolutionary relationships of the family using nrDNA and cpDNA sequences. The first part of the study investigated the evolutionary position of Anacardiaceae in relation to closely allied families within the order Sapindales. DNA sequence data for the chloroplast trnL intron and 3 exon, and the intergenic spacer between trnL and trnF (trnLF) of Anacardiaceae, Burseraceae, Julianiaceae, Pistaciaceae, Podoaceae, Rutaceae, and Sapindaceae were generated to reconstruct phylogenetic relationships of these families. Julianiaceae, Pistaciaceae, and Podoaceae were all nested within Anacardiaceae. The sister group of Anacardiaceae is Burseraceae. To understand intergeneric relationships within Anacardiaceae, phylogenies were constructed from sequences of three chloroplast loci (matK, trnLF, and rps16), using maximum parsimony and maximum likelihood as the optimality criteria. Based on these reconstructions and current knowledge of morphological and anatomical attributes of the Anacardiaceae, the subfamilies of Takhtajan, Anacardioideae (including tribes Anacardieae, Dobineae, Rhoeae, and Semecarpeae) and Spondioideae (including tribe Spondiadeae), were reinstated. Taxon distributions were mapped onto the phylogeny and the resulting biogeographic patterns were presented as evidence for the complex biogeographical history of the cashew family. Chloroplast (trnLF) and SSU nrDNA (ITS and ETS) loci were sequenced to delimit the generic boundaries and biogeographical history of the Madagascan/African genus Protorhus. These findings resulted in the recognition of a new Madagascan endemic genus, Abrahamia Randrianasolo ined., segregated from Protorhus. From age estimates of the Sapindales, the isolation of Madagascar, and the phylogeny of the African/Madagascan clade of Anacardiaceae, it is unlikely that vicariance played a role in the evolution of Madagascan Anacardiaceae. One possible scenario based on phylogenetic reconstruction is that Anacardiaceae was dispersed over water between Africa and Madagascar a minimum of three times.