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Mikania palmata and Mikania wurdackii, endemic to Ecuador and Peru, respectively, are new species. Both are members of section Summikania. Dendroid hairs are reported on the leaves, stems, and capitulescences of M. wurdackii and compared to somewhat similar structures reported elsewhere in the genus only on the cypselae of two Brazilian species.
We used discriminant analysis to assess taxonomic status of three closely related, rare taxa within the cactus genus Escobaria (E. guadalupensis, E. sneedii var. sneedii, and E. sneedii var. leei). These three taxa consist of nine isolated populations; six of these populations consist of morphologically typical specimens (i.e., similar to the type specimen), while three populations are of questionable taxonomic status. We used the six morphologically typical populations (referred to as assigned populations) to derive predictive discriminant functions for each taxon. These discriminant functions were then applied to assigned populations to determine the status and taxonomic boundaries of each taxon, and to the three questionable populations (referred to as unassigned populations) to interpret their taxonomic status. Our model included four predictor variables: number of immature stems, mature stem diameter, number of radial spines, and length of the innermost central spines. Discriminant analysis correctly classified >93% of 186 individuals from the six assigned populations, suggesting a distinct status for each taxon. Applying the predictive discriminant functions to unassigned populations resulted in classifying a large percentage of individuals from each unassigned population into each of two taxa. This suggests that the unassigned populations consist of morphological intermediates, possibly as the result of hybridization. Meiotic chromosome numbers of n = 11 were determined for E. guadalupensis, E. sneedii var. leei, and the three unassigned populations.
Detailed descriptions, habitat preferences, geographic range, and representative specimens are given for the 13 native and two introduced taxa of Acacia subgenus Acacia (approximately the same as Acacia series Gummiferae) that are found in the South American flora. Some of these taxa are wide ranging. Acacia macracantha, A. tortuosa, and A. farnesiana are extremely common in northern South America, whereas A. caven and A. aroma occur throughout much of the southern half of the continent. The remaining species have restricted ranges, being found in relatively small areas. Principal components analysis (PCA) of vegetative and floral features shows that these species form discrete groups in plots of the first three principal components. From these data, most of the species were found to be relatively homogeneous, as indicated by the tight clusters formed in the PCA plots. In contrast, A. macracantha, a species ranging from Florida, south through the Caribbean, into South America, and in Mexico, is highly variable morphologically. The data suggest little gene flow between species. Hybrids are extremely uncommon.
Comparative restriction site mapping of the chloroplast genome of 26 accessions of Acacia plus outgroups (Caesalpinia, Albizia, and Ebenopsis) was carried out to analyze phylogenetic relationships among the subgenera of Acacia and, in particular, within Acacia subgenus Acacia. One or more taxa from each of seven New World species-groups plus two African species of Acacia subgenus Acacia were included in the analysis to generate hypotheses of the evolution and radiation of this group. Restriction maps constructed from data from 11 restriction enzymes yielded 212 informative restriction sites out of a total of 900. Parsimony analysis resulted in a total of 12 most parsimonious trees of 663 steps each. The strict consensus tree and bootstrap and decay indices indicate strong support for monophyly of Acacia subgenus Acacia and provisional support for the paraphyly of Acacia overall. Moderately to strongly supported clades within Acacia subgenus Acacia indicate that the mesically adapted A. macracantha species-group is polyphyletic and may represent lineages with sister group relationships with both the ant-acacias and the more xerically adapted A. farnesiana species-group. A group of Caribbean species was found to be ancestral in Acacia subgenus Acacia and African and South American species were found to be relatively derived with respect to North American species, lending support to a Boreotropical, rather than a Gondwanan, hypothesis of the historical biogeography of Acacia subgenus Acacia.
Sideritis L. subgenus Marrubiastrum (Lamiaceae) comprises 24 species of Macaronesian endemic perennials. The constituent taxa encompass a wide array of life forms that have exploited all ecological zones present in the Macaronesian archipelagos of Madeira and the Canary Islands. Though recently revised, an explicit phylogeny of the subgenus is still lacking. This group is especially intriguing because it exhibits the largest aneuploid series ever reported in oceanic island plants. The present study uses a chloroplast DNA restriction site analysis to elucidate the pattern of evolution within and among the islands. The insular taxa form a strongly supported monophyletic group, indicating a single colonization of Macaronesia. Monophyly of the sections is not supported. Integrating geographical and ecological distribution with the cpDNA phylogeny reveals a pattern of diversification within the islands consistent with adaptive radiation. Most other Macaronesian plant groups studied thus far have diversified by inter-island colonization between similar ecological zones. An analysis of chromosome number suggests a bimodal pattern of chromosomal change in the island subgenus, with one clade showing a decreasing aneuploid series and a second clade exhibiting aneuploid increase. The rate of change appears markedly amplified relative to that of the continental subgenus. This extreme level of chromosomal diversity stands in stark contrast to a general pattern of chromosomal stasis in island plants.
Chloroplast DNA (cpDNA) restriction site maps for 113 species of Apiaceae (Umbelliferae) and the allied families Araliaceae and Pittosporaceae were constructed for two enzymes and examined for variation in position of JLB, the junction between the large single copy and inverted repeat regions that is typically contained within the ribosomal protein S10 operon. With the exception of one large clade in Apiaceae subfamily Apioideae, all species possess a JLB indistinguishable from that found in the vast majority of angiosperms. Within this large clade, however, at least one expansion and seven different contractions of the IR relative to the tobacco JLB were detected, each ranging in size from ∼1–16 kb. Five of the junction shifts are parsimony informative, and three support major clades delimited in earlier phylogenetic studies. In light of cladograms based on previous studies of restriction site and DNA sequencing data, the IR appears to have expanded and contracted a minimum of ten times during the evolution of Apioideae, with several presumably identical size variants occurring in parallel. The frequency and large size of JLB shifts in Apioideae cpDNAs are unprecedented among angiosperms, indicating that the subfamily represents a model system to study the mechanisms leading to large-scale expansions and contractions of the IR.
The plant family Commelinaceae displays a wide range of variation in vegetative, floral, and inflorescence morphology. This high degree of variation, particularly among characters operating under strong and similar selective pressures (i.e., flowers), has made the assessment of homology among morphological characters difficult, and has resulted in several discordant classification schemes for the family. Phylogenetic relationships among 40 of the 41 genera in the family were evaluated using cladistic analyses of morphological data. The resulting phylogeny shows some similarity to the most recent classification, but with some notable differences. Cartonema (subfamily Cartonematoideae) was placed basal to the rest of the family. Triceratella (subfamily Cartonematoideae), however, was placed among genera within tribe Tradescantieae of subfamily Commelinoideae. Likewise, the circumscriptions of tribes Commelineae and Tradescantieae were in disagreement with the most recent classification. The discordance between the phylogeny and the most recent classification is attributed to a high degree of convergence in various morphological characters, particularly those relating to the androecium and the inflorescence. Anatomical characters (i.e., stomatal structure), on the other hand, show promise for resolving phylogenetic relationships within the Commelinaceae, based upon their agreement with the most recent classification.
Nucleotide sequence data from the chloroplast genome from the non-coding trnL-trnF intron and spacer corroborate previous suggestions about the monophyly of the African Restionaceae. These data, combined with a morphological character set, show that neither Staberoha nor Ischyrolepis are basal to the African Restionaceae but rather are embedded in the Restio clade. There is strong support for a basal dichotomy that separates the woody nut Willdenowia clade from the soft nut and capsular Restio clade. However, the resolution within these two clades is poor, possibly suggesting recent radiation. The monophyly of the genera Elegia, Staberoha, Thamnochortus, Ischyrolepis, Cannomois, and Ceratocaryum is corroborated (albeit on very small sample sizes), but Chondropetalum, Restio, Calopsis, Hypodiscus, Anthochortus and Willdenowia are shown to be para- or polyphyletic. Dovea, Askidiosperma, Rhodocoma, Platycaulos, Mastersiella, Hydrophilos, and Nevillea are either monotypic, or have been represented by a single species in this analysis, and consequently their monophyly cannot be evaluated. It is evident that despite massive generic redelimitations in the family 15 years ago, more changes will have to be made in order to establish a taxonomy of monophyletic genera.
Analysis of three plastid DNA sequences for a broad sampling of Amaryllidaceae resolve the American genera of the Amaryllidaceae as a clade that is sister to the Eurasian genera of the family, but base substitution rates for these genes are too low to resolve much of the intergeneric relationships within the American clade. We obtained ITS rDNA sequences for 76 species of American Amaryllidaceae and analyzed the aligned matrix cladistically, both with and without gaps included, using two species of Pancratium as outgroup taxa. ITS resolves two moderately to strongly supported groups, an Andean tetraploid clade, and a primarily extra-Andean “hippeastroid” clade. Within the hippeastroid clade, the tribe Griffineae is resolved as sister to the rest of Hippeastreae. The genera Rhodophiala and Zephyranthes are resolved as polyphyletic, but the possibility of reticulation within this clade argues against any re-arrangement of these genera without further investigation. Within the Andean subclade, Eustephieae resolves as sister to all other tribes; a distinct petiolate-leafed group is resolved, combining the tribe Eucharideae and the petiolate Stenomesseae; and a distinct Hymenocallideae is supported. These Andean clades are all at least partially supported by plastid sequence data as well. We infer from our data that a great deal of the diversity of the family in the Americas is recent, and that the American Amaryllidaceae may have been reduced to peripheral isolates some time after its initial entry and spread through the Americas. While the sister relationship of the American and Eurasian clades might argue for a Boreotropical origin for the family in America, the cladistic relationships within the American clade based on ITS do not provide any further support for this or any other hypothesis of the family's entry into America. The new tribe Clinantheae is described (four genera: Clinanthus, Pamianthe, Paramongaia, and Pucara), and the lorate-leafed species of Stenomesson are transferred to Clinanthus.
The phylogenetic relationships of 29 genotypes representing 12 species of the genus Corylus (Betulaceae) were investigated using sequences of the internal transcribed spacer regions of the nuclear ribosomal DNA and the chloroplast matK gene. The two genes gave different results. The ITS region in Corylus yielded only 22 informative characters. Nevertheless, several clades in Corylus were resolved: the shrub species C. avellana, C. maxima, C. americana, and C. heterophylla; another group of shrub species C. cornuta, C. californica, and C. sieboldiana; and the tree species C. colurna, C. chinensis, and C. jacquemontii which formed a paraphyletic group. Corylus ferox formed the basal-most branch of the Corylus clades. The strict consensus tree was congruent with the results of interspecific hybridization relationships and morphological classification. The matK sequence yielded only 10 informative characters. Two clusters appeared on the strict consensus tree, one with Asian and European species, and the other with North American species. However, this classification based on matK sequences was not in agreement with currently accepted taxonomic classification, and the paucity of informative characters precludes more definitive inferences from the matK data.
Nyctaginaceae are a small family of mainly New World tropical and subtropical trees, shrubs, and herbs. To date phylogenetic relationships within the family have not been examined. This study provides the first phylogenetic hypothesis of relationships within Nyctaginaceae tribe Nyctagineae based on sequence data from both nuclear (ITS) and chloroplast (accD 5‘coding region and intergenic region between the rbcL and accD genes). Morphological characters are also discussed as they relate to the phylogeny inferred using molecular data. Results suggest that neither Acleisanthes nor Selinocarpus is monophyletic but that together they comprise a monophyletic lineage. The genus Mirabilis is strongly supported as monophyletic, but the monophyly of two of its sections is suspect. Morphology generally agrees with the molecular data and in some instances reinforces clades weakly supported by nuclear and chloroplast data. Further sampling will help clarify relationships of these genera within Nyctaginaceae.