Chloroplast DNA Restriction Site Variation Research Articles

Systematic Implications of Chloroplast DNA Variation in the Genus Microseris (Asteraceae: Lactuceae)

Chloroplast DNA restriction site variation was examined for all 16 species of Microseris, using 22 restriction endonucleases, filter hybridization experiments, and comparative mapping procedures. Mutations were scored relative to other genera of the subtribe Microseridinae, and related genera of the tribe Lactuceae. A total of 115 restriction site mutations was detected, 78 of which were phylogenetically informative. A single most parsimonious cladogram was constructed which indicates three major lines of evolution within the genus. The morphologically distinct annual M. lindleyi was found to be the most divergent and forms the basal lineage within the genus. Forty-three mutations separate annual and perennial species of the genus, whose average sequence divergence is 0.7%. The parentage of the allotetraploid species M. heterocarpa was confirmed, utilizing cpDNA and nuclear ribosomal DNA variation. Evaluation of relative rates of cpDNA evolution indicates that generation time is not responsible for unequal rates of cpDNA in different lineages. The results also suggest that a taxonomic reevaluation of Microseris at the subgeneric level is war- ranted. Microseris D. Don is comprised of 16 species

A phylogenetic analysis of chloroplast DNA restriction site variation inPoaceae subfam.Pooideae

A phylogenetic analysis was conducted on chloroplast DNA restriction site variation in 34 genera of grasses (familyPoaceae), including 28 genera from subfam.Pooideae (representing tribesAveneae, Brachypodieae, Bromeae, Meliceae, Poeae, Stipeae, andTriticeae) and representatives of three other subfamilies,Arundinoideae, Oryzoideae, andPanicoideae. Analyses of all 34 genera always distinguishedPooideae as monophyletic, regardless of which nonpooid genus functioned as outgroup; six separate analyses of all 28 pooid genera, each including one of the six nonpooid genera as outgroup, resolved five identically-constituted clades withinPooideae (in four cases), or (in the other two cases) yielded results that were less well resolved, but not in conflict with those of the other four analyses. The four best-resolved analyses distinguishedMeliceae as the earliest diverging lineage withinPooideae, andStipeae as the next. Above the point of divergence ofStipeae is a dichotomy between supertribeTriticodae (including tribesBrachypodieae, Bromeae, andTriticeae), and a clade comprisingPoeae andAveneae. The analysis supports some tribal realignments, specifically the assignment ofBriza, Chascolytrum, Microbriza, andTorreyochloa toAveneae, andArctagrostis, Catabrosa, andSesleria toPoeae. The analysis also suggests that the pooid spikelet (i.e., glumes shorter than lemmas and florets two or more) is plesiomorphic inPooideae, and that spikelets with one floret, and those with glumes longer than the first lemma, each have evolved more than once withinPooideae. Results also indicate that small chromosomes and chromosome numbers based on x=c. 10−12 are plesiomorphic withinPooideae. Alternative states of these characters (chromosomes large, chromosome numbers based on x=7) are interpreted as synapomorphies or parallelisms of clades that includeTriticodae, Aveneae, andPoeae. Lanceolate lodicule shape may be a synapomorphy of the clade that includesStipeae, Triticodae, Aveneae, andPoeae, and loss of lodicule vascularization a synapomorphy of the entirePooideae.