Systematics of neotropical Psiguria (Cucurbitaceae) : identifying low-copy nuclear markers, molecular phylogenetics, and taxonomic revision

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Title: Systematics of neotropical Psiguria (Cucurbitaceae) : identifying low-copy nuclear markers, molecular phylogenetics, and taxonomic revision
Author: Steele, Pamela Roxanne
Abstract: Psiguria Arn . is a small genus of Neotropical vines in the Cucurbitaceae that grows in both wet and dry tropical forests from southern Mexico to Paraguay , and on Caribbean islands . The genus is estimated to be very young with natural history characteristics that have contributed to confusing species circumscriptions . The unique relationship of plants in the group with their butterfly pollinators makes Psiguria an interesting and important genus in tropical ecosystems . Both molecular and morphological approaches were used to investigate the monophyly of Psiguria , to elucidate the number of species in the genus , to discover sister relationships , and to identify characteristics for delineating species . Toward that end , an intensive screening of 141 primer combinations in search of phylogenetically informative low -copy nuclear markers was conducted along with a molecular phylogenetic analysis and a complete taxonomic revision of Psiguria . From the screening study , three potentially phylogenetically informative low -copy nuclear markers were discovered for Psiguria , 11 were found to be potentially useful in rosids , and 32 in other angiosperms . DNA sequences for eight chloroplast intergenic spacers (ndhF -rpL32 , ndhC -trnV , rps16 -trnQ , trnS -trnG , psbZ -trnM , psbM -trnD , rpoB -trnC , and psbE -petL ) , ITS , and the nuclear serine /threonine phosphatase intron were obtained for 70 samples of Psiguria plus 14 outgroups . Phylogenetic analyses support the monophyly of Psiguria and a sister relationship between P . umbrosa and P . warscewiczii . In the final chapter , two reviews on the genus are presented – one encapsulating the nomenclatural history , and one summarizing 35 years of ecological and natural history studies . In addition , morphological characters were databased , descriptions were written , and maps of geographic distribution were produced for all species . Considering both molecular and morphological data , six species of Psiguria are defined . To distinguish those species missing identifiable morphological characters , a set of DNA barcodes was developed . At least four chloroplast regions are required to differentiate species (ndhC -trnV , rps16 - trnQ , rpoB -trnC , and ndhF -rpL32 ) . Because of the absence of many morphological characters , two taxonomic keys are presented – one using male flowers , and the other using the set of DNA barcodes along with consistent leaf characteristics and geographic distribution .
URI: http : / /hdl .handle .net /2152 /6657
Date: 2009-10-23

Citation

Systematics of neotropical Psiguria (Cucurbitaceae) : identifying low-copy nuclear markers, molecular phylogenetics, and taxonomic revision. Doctoral dissertation, The University of Texas at Austin. Available electronically from http : / /hdl .handle .net /2152 /6657 .

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