Boni C. Cruz

Phylogeny and infrageneric classification of Symplocos (Symplocaceae) inferred from DNA sequence data

Symplocos comprises ∼300 species of woody flowering plants with a disjunct distribution between the warm-temperate to tropical regions of eastern Asia and the Americas. Phylogenetic analyses of 111 species of Symplocos based on the nuclear ribosomal internal transcribed spacer (ITS) region and the chloroplast genes rpl16, matK, and trnL-trnF yielded topologies in which only one of the four traditionally recognized subgenera (Epigenia; Neotropics) is monophyletic. Section Cordyloblaste (subgenus Symplocos; eastern Asia) is monophyletic and sister to a group comprising all other samples of Symplocos. Section Palura (subgenus Hopea; eastern Asia) is sister to a group comprising all other samples of Symplocos except those of section Cordyloblaste. Symplocos wikstroemiifolia (eastern Asia) and S. tinctoria (southeastern United States), both of subgenus Hopea, form a clade that groups with S. longipes (tropical North America) and the species of subgenus Epigenia. The remaining samples of subgenus Hopea (eastern Asia) form a clade. Section Neosymplocos (subgenus Microsymplocos; Neotropics) is well nested within a clade otherwise comprising the samples of section Symplocastrum (subgenus Symplocos; Neotropics). Section Urbaniocharis (subgenus Microsymplocos; Antilles) groups as sister to the clade comprising Symplocastrum and Neosymplocos. The data support the independent evolution of deciduousness among section Palura and S. tinctoria. The early initial divergence of sections Cordyloblaste and Palura from the main group warrants their recognition at taxonomic levels higher than those at which they are currently placed. An inferred eastern Asian origin for Symplocos with subsequent dispersal to the Americas is consistent with patterns from other phylogenetic studies of eastern Asian-American disjunct plant groups but contrary to a North American origin inferred from the earliest fossil occurrences of the genus.

Phylogeny of Caragana (Fabaceae) based on DNA sequence data from rbcL, trnS-trnG, and ITS

Phylogenetic relationships of 48 species of Caragana (Fabaceae: tribe Hedysareae) and one representative each of Astragalus, Calophaca, Halimodendron, and Hedysarum are estimated from DNA sequences of the rbcL gene, trnS-trnG intron and spacer, and ITS region. At least one representative of all five sections and 12 series within Caragana are included. Analyses yielded strongly supported clades corresponding to sections Caragana, Bracteolatae, and Frutescentes. The species of section Jubatae are distributed among three strongly supported clades, i.e., one with the species of section Bracteolatae, another with two species of section Spinosae, and a third as sister to section Frutescentes. All but the last of these six clades are corroborated by at least one unambiguously traced morphological character. The placement of the other four species of section Spinosae are not well supported and lack unambiguous morphological synapomorphies, and the samples of Calophaca and Halimodendron nest within Caragana with weak support.

Reticulate evolution, cryptic species, and character convergence in the core East Asian clade of Gaultheria (Ericaceae)

Phylogenetic relationships of 84 samples representing 30 species in the core East Asian clade of the wintergreen group of Gaultheria (Angiospermae: Ericaceae: Gaultherieae) were estimated from separate and combined DNA sequence data from five genic regions (ITS, matK, rpl16, trnL-trnF, and trnS-trnG) with parsimony, likelihood and Bayesian analyses. Two major clades were recovered, one comprising several sections and series with leaves generally more than 1 cm long [the ser. Leucothoides sensu lato (s.l.) clade] and another comprising the species of ser. Trichophyllae, with leaves generally less than 1 cm long. The ITS region yielded little phylogenetic resolution, whereas in the combined chloroplast analysis the samples from individual morphospecies in both clades were often nonmonophyletic. This was postulated to result from reticulate evolution in the ser. Leucothoides s.l. clade, particularly in two specific cases of hybridization and a crown clade with likely chloroplast capture following localized introgression. In the ser. Trichophyllae clade, such nonmonophyly was largely attributed to cryptic species and character convergence resulting at least partly from extreme morphological reduction. The relatively low-elevation habitats in which the species of the ser. Leucothoides s.l. clade generally grow are thought to have promoted opportunities for sympatry and reticulation, whereas the high-alpine habitats of ser. Trichophyllae are more likely to have spawned isolated populations and narrow endemism. As in other Sino-Himalayan plant groups, overall low sequence divergence and reticulate evolution suggest rapid radiation in the core East Asian clade of Gaultheria.

Phylogeny of Symplocos Based on DNA Sequences of the Chloroplast trnC-trnD Intergenic Region

Abstract Phylogenetic analysis of 74 species of Symplocos was conducted with DNA sequence data from the chloroplast trnC-trnD intergenic region. Maximum parsimony and Bayesian inference trees are consistent with those of a previous study based on combined data from the nuclear ribosomal ITS region and the chloroplast regions rpl16, matK, and trnL-trnF. The inclusion of 21 phylogenetically informative indel characters from trnC-trnD resulted in greater maximum parsimony resolution and clade support than with these characters excluded. A combined five-gene-region (trnC-trnD, ITS, rpl16, matK, and trnL-trnF) analysis based on a data set with complete sequence data is almost completely concordant with that of the combined four-gene data set, and displays higher resolution and overall clade support (in some cases 20 to > 30 bootstrap percentage points). The data indicate monophyly for only one subgenus (Epigenia) and four sections (Barberina, Cordyloblaste, Neosymplocos, and Urbaniocharis) of Symplocos; the other three subgenera (Symplocos, Hopea, and Microsymplocos) and tested sections (Bobu, Palaeosymplocos, and Symplocastrum) will require recircumscription to accord with the principle of monophyly. Supermatrix and supertree analyses were conducted to provide phylogenetic estimates based on all 107 available Symplocos samples with sequence data from at least two of the five gene regions. The supermatrix consensus tree is completely consistent with that from the combined five-gene estimate based on complete sequence data, whereas the supertree consensus differs from these trees in two regions of the topology. The supermatrix consensus also displays greater clade resolution than the supertree consensus. The aligned trnC-trnD data set exhibits a lower percentage of parsimony-informative characters than those based on matK and rpl16 sequences. The length, organization, and relative sequencing ease of trnC-trnD in Symplocos nonetheless confirm the utility of this region for phylogenetic estimation in flowering plants, as previously described.

Phylogeny of Cercis based on DNA sequences of nuclear ITS and four plastid regions: implications for transatlantic historical biogeography.

The disjunct genus Cercis has been used to test models of Northern Hemisphere historical biogeography. Previous phylogenetic estimates employing DNA sequences of the ITS region and (in one study) those of ndhF recovered a well supported clade of North American and western Eurasian species that was nested within a paraphyletic group of Chinese species. Resolution and clade support within the tree were otherwise low and the monophyly of Cercis canadensis was uncertain. Here we conduct a phylogenetic analysis of Cercis with a higher number of regions (ITS, ndhF, rpoB-trnC, trnT-trnD, and trnS-trnG) and samples than in previous studies. Results corroborate the initial divergence between the Chinese species Cercis chingii and the rest of the genus. Support is newly found both for a clade of the two North American species as sister to the western Eurasian species, and for the monophyly of C. canadensis. As in a previous study, divergence between North American and western Eurasian Cercis was estimated as mid-Miocene (ca. 13 million years ago), and the ancestor in which this divergence occurred was inferred to be xerophytic. Contrary to previous studies, however, our data infer strictly east-to-west vicariance. The timing of the transatlantic divergence in Cercis is too recent to be explained by a postulated continuous belt of semi-arid vegetation between North America and Europe in the Paleogene, suggesting instead the presence of a Miocene North Atlantic corridor for semi-arid plants. In the absence of strong evidence from other sources, the possibility that Cercis has been able to quickly adapt from mesophytic antecedents to semi-arid conditions whenever the latter have arisen in the Northern Hemisphere can be considered a plausible alternative, although parsimony optimization renders this scenario two steps longer.

Phylogeny of Sinojackia (Styracaceae) Based on DNA Sequence and Microsatellite Data: Implications for Taxonomy and Conservation

BACKGROUND AND AIMS The genus Sinojackia consists of eight species, all endemic to China. All species of Sinojackia are endangered or threatened owing to poor recruitment within populations. Information on molecular phylogenetics is critical for developing successful conservation strategies for this genus. METHODS Combined DNA sequence data from the nuclear ribosomal internal transcribed spacer regions and plastid psbA-trnH intergenic spacer and microsatellite data were used to infer a phylogeny of the genus. KEY RESULTS Parsimony analysis of the combined sequence data and multivariate analysis based on fruit characters indicated that Sinojackia dolichocarpa is monophyletic and genetically well separated from the other Sinojackia species, thus supporting its rank at the generic level as Changiostyrax. Phylogenetic relationships within Sinojackia sensu stricto are unresolved from the combined sequence data. A UPGMA dendrogram based on seven microsatellite loci of 96 individual plants yielded a first-diverging cluster of all individuals of S. microcarpa. The remaining species form another cluster without any definitive patterns corresponding to current species circumscriptions, suggesting either extensive hybridization or incipient speciation. CONCLUSIONS The results suggest that there are too many species recognized within Sinojackia sensu stricto, but this must be further assessed with comprehensive morphological and taxonomic revisionary work. The implications of the phylogenetic data for conservation are discussed.

Phylogenetic Analysis of the Wintergreen Group (Ericaceae) based on Six Genic Regions

Abstract Previous phylogenetic studies based on DNA sequence data from the genic regions ndhF, matK, atpB—rbcL (cpDNA) and ITS 2 (nrDNA) strongly support the monophyly of the wintergreen group (Ericaceae: Gaultherieae: Diplycosia, Gaultheria, Tepuia) and have assessed the relationships of its major clades. Other studies that include additional genic regions have been limited to two clades corresponding to various sections or series within Gaultheria. Here we expand both the number of species (from 42 to 104) and genic regions (chloroplast matK, ndhF, rpl16, trnL—trnF, trnS—trnG, and the complete ITS region) to further assess phylogenetic relationships in the wintergreen group. With the additional data we detected several areas of incongruence between the trees from the nuclear and combined chloroplast analyses, including a topologically deep conflict involving G. procumbens. Such incongruence likely originated from reticulation events, long considered to have influenced the evolution of various lineages in Gaultheria. We also detected a duplication, possibly nuclear-encoded, of the matK region in one of the Australian/New Zealand lineages. A combined six-gene analysis, in which taxa involved in the conflicting topologies were excluded, yielded higher support values for several early-diverging clades. The monophyly of both Diplycosia and Tepuia is corroborated, as is the successive nesting of Tepuia, G. section Hispidulae (both placements of which have newfound strong support), G. ser. Gymnobotrys, and Diplycosia. Whereas several sections or series with more than one species in the most recent classification of Gaultheria are supported as circumscribed (i.e. G. section Amblyandra and series Hispidulae, Myrtilloideae, and Trichophyllae), others comprise species from two to several different clades.

Hybridization between two oil-secreting orchids in South Africa

Natural hybrids among the specialized terrestrial oil-secreting orchids of South Africa are extremely rare even where multiple closely related species co-occur. We found putative hybrids between Pterygodium catholicum Sw. and P. acutifolium Lindl., two closely related oil-secreting orchids that lack morphological barriers to inter-breeding. The purpose of this study was to confirm the parentage of the putative hybrids using molecular data from one nuclear (ITS) and two plastid (matK-trnK and trnL/F introns) DNA regions. Phylogenetic analyses of sequences as well as nucleotide substitution patterns of the putative hybrids, putative parents, and their closest relatives were consistent with a hypothesis of hybridization. We suggest that the hybrids were the result of visits to both orchids by a single species of oil-collecting bee during a brief period of flowering overlap. These results suggest that the rarity of hybrids between these orchids is due to factors other than genetic incompatibility.

Early Phylogenetic Divergence of Gynodioecious Species Warrants the Recognition of Subseries in Styrax Series Valvatae

Abstract In Styrax (Ericales: Styracaceae), gynodioecy is known or likely in ten species. A previous morphological analysis of the genus placed these species into a single highly derived clade within S. series Valvatae. In contrast, DNA sequence data from the nuclear ribosomal internal transcribed spacer (ITS) region yielded two distinct gynodioecious clades within the series, one (South American species) as sister to the rest of S. series Valvatae, the other (S. obtusifolius only; Cuba) as phylogenetically nested within a clade of otherwise hermaphroditic species. Here we test these contrasting phylogenetic placements with analyses that include the plastid ndhF-rpl32-trnL, trnL-trnF, trnS-trnG, and trnV-ndhC genic regions in addition to ITS. Results strongly corroborate the phylogenetic positions of the two gynodioecious clades based on ITS data alone. Clade-specific ITS-plastid phylogenetic discordance provides evidence for hybridization and suggests a pattern of reticulate evolution among some of the southern Brazilian species of the series. Our results agree with the prior evidence for convergent evolution among the gynodioecious species associated with floral reduction. Based on our results and long-standing precedent, we re-confer formal taxonomic recognition on the South American gynodioecious clade by dividing S. series Valvatae into two new subseries, Styrax subseries Latifoli and Foveolaria.