The role of nucleocytoplasmic interactions in the genesis of post-zygotic isolation has been given little attention by plant evolutionists. I present evidence from reciprocal crosses, cytoplasmic substitution lines, and cell fusion lines that hybrid weakness and sterility often arise from interactions between the nuclear genome and the chloroplast and mitochondrial genomes. These interactions are much more important in the origin and isolation of species than we appreciate. The strength of the post-zygotic barriers tends to be a function of cytoplasmic divergence. I also review evidence indicating that the properties and evolutionary potential of allopolyploids and diploid hybrid derivatives may be influenced by cytoplasmic factors.

Communicating Editor: John V. Freudenstein

One new species of Herbertus with distinctly verruculose cuticle from Papua New Guinea is described and illustrated: Herbertus streimannii sp. nov. Eight species of Herbertus are present in Australasia and the south Pacific: H. armitanus (Steph.) H. A. Mill., H. circinatus (Steph.) H. A. Mill., H. leratii (Steph.) H. A. Mill., H. longifissus Steph., H. oldfieldianus (Steph.) Rodway, H. pilifer Schiffn., and H. ramosus (Steph.) H. A. Mill. Herbertus huerlimannii H. A. Mill. and H. parisii (Steph.) H. A. Mill. are placed under the synonymy of H. longifissus, H. alpinus (Steph.) E. A. Hodgs. under H. oldfieldianus, H. javanicus (Steph.) S. Hatt. under H. ramosus, and H. setigerus (Steph.) H. A. Mill. under H. leratii. A key to all the species in the region is provided.

Communicating Editor: Alan T. Whittemore

Cladistic analyses based on chloroplast protein coding genes rbcL and rps4, and the chloroplast encoded trnL (UAA) intron were conducted (1) to investigate phylogenetic relationships among basal peristomate mosses, especially the nematodontous mosses (Tetraphidaceae and Polytrichaceae), and the arthrodontous mosses with pleated endostomes (Buxbaumiaceae and Diphysciaceae), and (2) to make inferences on evolution of the peristome. A combined data matrix included 46 taxa and 2206 characters of which 619 were parsimony informative. The results indicate that the basal peristomate mosses, particularly the Tetraphidaceae, Polytrichaceae and Buxbaumiaceae, are paraphyletic. Sister group relationships between the following taxa are newly suggested: Tetraphidaceae and all peristomate mosses; Polytrichaceae and the clade consisting of Buxbaumiaceae, Diphysciaceae, diplolepideous and haplolepideous mosses; Buxbaumiaceae and the clade consisting of Diphysciaceae, diplolepideous and haplolepideous mosses. The following novel inferences on peristome evolution are also suggested: the plesiomorphic condition of the endostome of the arthrodontous peristome was pleated; the pleated endostome has been transformed into a keeled endostome in the diplolepideous/haplolepideous clade; the similarity in cell divisions preceding deposition of secondary peristomial wall material in peristome development is a synapomorphy in the peristomate mosses. The exostome has been independently lost or reduced in the Diphysciaceae, and the diplolepideous/haplolepideous clade.

Communicating Editor: Alan T. Whittemore

Cladistic analyses of Iris included 18 ingroup taxa from series Californicae and two outgroup taxa from series Sibiricae. The internal transcribed spacers and the 5.8S subunit of 18–26S nuclear ribosomal DNA were sequenced to provide phylogenetic information. An analysis of DNA data resulted in five most parsimonious trees that concurred in part with morphological data. Species groups in series Californicae that have been informally proposed by previous workers were not supported in this study. Two species complexes, I. tenax and I. hartwegii, were not monophyletic as currently delineated. Support for several internally resolved clades is low with DNA data, probably due to high levels of homoplasy along some branches. The overall level of variation and sequence divergence is relatively high compared to other infrageneric plant groups.

Communicating Editor: James F. Smith

Separate and combined analyses of morphology, rps16, and rbcL data were conducted on a total of 27 Alstroemeriaceae species including 23 Alstroemeria, three Bomarea, and Leontochir. We wished to examine the monophyly of Alstroemeria and Bomarea as well as explore the phylogenetic position of Leontochir and two controversial monotypic genera segregated from Alstroemeria: Schickendantzia and Taltalia. Monophyly of the Chilean and Brazilian Alstroemeria species were explored. The results support monophyly of the family. Alstroemeria and Bomarea are both monophyletic with the former genus being more strongly supported. Bomarea and the monotypic genus Leontochir form a clade distinguished from Alstroemeria by a set of morphological characters. Bomarea could not be defined by morphological characters without including Leontochir. Resolution within Alstroemeria is only weakly supported and formal subdivisions should not be made until the Brazilian members are revised and/or more appropriate phylogenetic markers at the species level have been found. Alstroemeria graminea or A. pygmaea never appear in a position that makes their segregation from Alstroemeria possible (as Taltalia and Schickendantzia, respectively), without making Alstroemeria paraphyletic. The resolution best supported in this study divides Alstroemeria into subclades roughly corresponding to geography: a clade from northern Chile, a clade from central Chile, and a clade containing the Brazilian species. Most of the trans-andean species could not be unambigously placed by this study.

Communicating Editor: James F. Smith

The phylogenetic position of the Lampranthus group (Ruschioideae, Aizoaceae), with particular emphasis on the large genus Lampranthus, was studied using DNA sequences from the trnL-trnF region of the chloroplast genome, the nuclear ribosomal internal transcribed spacer (ITS) region and the 5S non-transcribed spacer (NTS). Phylogenies of 59 species in 29 genera of succulent Aizoaceae, including two species from subfamily Mesembryanthemoideae, are presented. Due to an inadequate number of informative sites within the Ruschioideae (31 for trnL-trnF; 49 for ITS), the trnL-trnF and ITS regions are found to be unsuitable for phylogenetic investigations at the specific and generic level. The 5S spacer proves useful at the generic level, but fails to reveal well-supported phylogenies above the generic level. Combined analyses of all three gene regions show that Lampranthus N.E.Br. in its present circumscription is not monophyletic. A “core” of species of Lampranthus is well supported with numerous species of Lampranthus more closely related to other genera. At a higher taxonomic level, the data also do not support a monophyletic Lampranthus group. Circumscription of informal groups within the Ruschioideae, including the Lampranthus group, has mainly been based on the shared presence of a particular type of fruit. Fruits of the Lampranthus group are characterized by long, diverging expanding keels, broad valve wings and the absence of a closing body. The present data implies that this fruit type is homoplasious.

Communicating Editor: Alan T. Whittemore

Tamarix is a taxonomically difficult Old World genus that has become naturalized and invasive in the Americas and Australia. We examine the morphology and taxonomic history of 12 putative U.S. invasive Tamarix species, and investigate current invasions using chloroplast and nuclear sequence data. We test molecular phylogenetic hypotheses regarding the relationships of putative invasive taxa, and conclude that there are four invasive entities in the U.S., two of which are T. aphylla and T. parviflora. The sequence data also identify an invasive entity consisting of genetically indistinguishable T. ramosissima and T. chinensis, and another consisting of genetically indistinguishable T. gallica and T. canariensis. There is evidence of introgression between T. ramosissima, T. canariensis, and T. gallica, which is a likely source of confusion in the identification of some Tamarix invasions.

Communicating Editor: Jeff H. Rettig

Using rbcL plastid DNA sequences, we evaluated monophyly and relationships of the genera of Crossosomataceae, which are a small group of shrubs from North America and Mexico: Crossosoma, Apacheria, Glossopetalon (Forsellesia), and Velascoa. Morphological characters that correspond to the phylogenetic patterns were examined. The analysis consisted of two steps. In the first, we analyzed the sequences of representatives of the four genera with those of over 500 species of eudicots. Based on these results, a second, restricted analysis with 25 taxa was conducted. Crossosomataceae are monophyletic and the four genera fell into a well-supported clade with representatives of Stachyuraceae and Staphyleaceae. Characters that mark Crossosomataceae are: microphyllous leaves (less than 5 cm long), solitary flowers with an apocarpous ovary and hypanthium, ventrally dehiscent follicles, and seeds with a fimbriate or irregular aril. A brief description of the family and an identification key for the genera are presented.

Communicating Editor: John V. Freudenstein

A phylogenetic analysis of Harpullia (two incompletely-known species excluded, Conchopetalum and Majidea as outgroups) based on morphological characters resulted in five most parsimonious cladograms. These cladograms and the strict consensus cladogram show a few polytomies. Only a few branches have relatively high Decay Indices. The strict consensus cladogram indicates that Harpullia is monophyletic (five synapomorphies) and does not support the existing subgeneric classification. Thus, it is advisable to refrain from any subgeneric classification. The historical biogeographic pattern confirms the one already found for eight other genera of Sapindaceae. Harpullia originated on the New Guinean—Australian plate and from there dispersal and speciation occurred towards New Caledonia and Southeast Asia main land.

Communicating Editor: Matt Lavin

Phylogenetic analysis of Macromeria based on 35 morphological characters produced a single most parsimonious tree that supports the monophyly of the genus. The phylogeny supports previous evaluations of relationships among species, and the resulting clades often connect sister taxa that are geographically proximate. Mapping of corolla size onto the phylogeny indicates that floral size has changed many times within the genus, and that the very large corolla size in southern populations of Macromeria viridiflora has been derived from a smaller-flowered ancestor.

Communicating Editor: John V. Freudenstein

Pollen and seed morphological data refute that Borreria hockii (R.D. Congo, Katanga) is synonymous to Spermacoce thymoidea (Southwest Angola, Huila). For the former, the necessary combination Spermacoce hockii is given; Spermacoce homblei, described from Katanga, is shown to be synonymous. The name Spermacoce thymoidea was also used for Zambian material from Mwinilunga that represents in fact a new species, Spermacoce stipularis, also collected from central Angola and Katanga. Spermacoce stipularis mainly differs from Spermacoce thymoidea in the presence of an elaiosome and in the type of pollen grain, and from Spermacoce hockii in the more slender and taller habit, the absence of heterophylly, and the smaller flowers. The value of the characters used in the taxonomy of the genus Spermacoce is briefly reviewed with special emphasis on the importance of seed and pollen data. The three species are restricted to high plateaus of the Zambezian regional center of endemism; they are geoxylic plants, a life form very common in the grass savannahs of these plateaus. Further comments on the ecology of the plateaus and their endemism are also provided.

Communicating Editor: James F. Smith

Two new Rubiaceae species, Robbrechtia grandifolia and R. milleri from Madagascar are described. Clearly belonging to the tribe Pavetteae, the species possess an unusual combination of characters (sheathing stipules with intrapetiolar lobes, young shoots and inflorescence parts covered with copious colleter exudate, long-tubed flowers with a well-developed calyx, a bilobed stigma and unilocular fruits with a single, deeply ruminate seed) that makes the establishment of a new genus, Robbrechtia, necessary. Detailed descriptions, illustrations and distribution data of the new taxa are given. The characters of the genus are evaluated and compared to those of the other representatives of the tribe Pavetteae.

Communicating Editor: Fred R. Barrie

Phylogenetic relationships among 75 species of Lentibulariaceae, representing the three recognized genera, were assessed by cladistic analysis of DNA sequences from the plastid rps16 intron and the trnL-F region. Sequence data from the two loci were analyzed both separately and in combination. Consensus trees from all analyses are congruent, and parsimony jackknife results demonstrate strong support for relationships both between and within each of the three demonstrably monophyletic genera. The genus Pinguicula is sister to a Genlisea-Utricularia clade, the phylogenetic structure within this clade closely follows Taylor's recent sectional delimitations based on morphology. Three principal clades are shown within Utricularia, with the basal sections Polypompholyx and Pleiochasia together forming the sister lineage of the remaining Utricularia species. Of the fundamental morphological specializations, the stoloniferous growth form apparently arose independently within Genlisea and Utricularia three times, and within Utricularia itself, perhaps more than once. The epiphytic habit has evolved independently at least three times, in Pinguicula, in Utricularia section Phyllaria, and within the two sections Orchidioides and Iperua (in the latter as bromeliad tank-epiphytes). The suspended aquatic habit may have evolved independently within sections Utricularia and Vesiculina. Biogeographic optimization on the phylogeny demonstrates patterns commonly associated with the boreotropics hypothesis and limits the spatial origin of Lentibulariaceae to temperate Eurasia or tropical America.

Communicating Editor: Matt Lavin

Genetic relationships of Mimulus michiganensis comb. et stat. nov., formerly known as M. glabratus var. michiganensis, and two related species that have been implicated in its origin, M. glabratus var. jamesii and M. guttatus, were studied using random amplified polymorphic DNA (RAPD) markers. Genetic similarities were calculated based on the RAPD data using Jaccard's coefficient and used to construct a UPGMA phenogram. All individuals of M. michiganensis were highly similar to each other and formed a distinct cluster in the phenogram. This cluster was nested among the individuals of M. glabratus var. jamesii, and the resulting cluster was, in turn, nested within the individuals of M. guttatus. These findings, in agreement with earlier morphological and crossing studies, support the elevation of the taxon in rank from variety to species; accordingly, the new combination M. michiganensis was established. No evidence was found to support earlier hypotheses of a role of M. guttatus in the origin of M. michiganensis through hybridization with M. glabratus var. jamesii or through direct ancestry via an aneuploidy event. The results are consistent with a close relationship between M. michiganensis and M. glabratus var. jamesii.

Communicating Editor: Thomas G. Lammers

Sequence data from the nrDNA external transcribed spacer (ETS) were generated to help resolve questions about the evolution of Machaeranthera left unanswered by previous analyses of chloroplast DNA (cpDNA) restriction site data and nrDNA ITS sequence data. Combined ITS and ETS (nrDNA) evidence agreed with cpDNA evidence in supporting a close relationship between Oönopsis and M. tanacetifolia. Nuclear rDNA evidence also supported an alliance between M. sections Blepharodon and Sideranthus. The nrDNA evidence provided greater support for the relationships of M. gypsitherma, M. heterophylla, M. stenoloba, and M. viscida than earlier analyses of ITS sequence data, reinforcing earlier conclusions that these species have experienced reticulate evolution. Finally, nrDNA evidence provided strong support for a group consisting of M. bigelovii, M. canescens, M. gypsitherma, and M. riparia. The relationships that nrDNA evidence supported for these four species conflicted substantially with those supported by cpDNA evidence. The many instances of conflict between cpDNA and nrDNA suggest that the evolution of Machaeranthera has been complex and may have involved as many as seven separate occurrences of reticulate evolution.

Communicating Editor: James F. Smith

Tageteae consist of approximately 216 New World species with a center of diversity in the Mexican highlands. The present study uses DNA sequences of the internal transcribed spacer region of nuclear ribosomal DNA and the 3′ end of the ndhF gene from the chloroplast to assess phylogenetic relationships within the tribe. Although trees from the two molecular makers are not completely congruent, both data sets provide support for the recognition of 21 genera of Tageteae. The combined data set generates a well-resolved tree with strong support for the monophyly of all but three genera. Tagetes is paraphyletic because Adenopappus and Vilobia are nested within the genus. Porophyllum is shown to be polyphyletic and P. tridentatum and P. crassifolium are recognized as belonging to a newly described genus Bajacalia. Two new combinations, B. tridentata and B. crassifolia, are proposed. Additionally, a new species Bajacalia moranii B. L. Turner, is described. The other species of Porophyllum examined are nested within or formed a sister group to Pectis. Dyssodia sensu lato is not monophyletic and its segregate genera should be recognized. The DNA phylogenies also support the transfer of Dyssodia jelskii into Schizotrichia, resulting in the new combination S. jelskii. The recognition of Pectis as a separate subtribe is also not supported. The lack of support for subtribal groupings and the small size of the Tageteae argue against formal recognition of subtribes. Chromosomal and biogeographic data correspond well with the combined molecular phylogeny. The phylogeny suggests that the Tageteae probably originated in Mexico and that there have been at least three independent introductions into South America. Chromosome numbers are quite variable within the tribe but are consistent within clades. The ancestral base chromosome number for the Tageteae is most likely x = 12 and there have been several episodes of aneuploid reduction in the evolution of the tribe.

Communicating Editor: John V. Freudenstein

The internal transcribed spacer (ITS) region of nuclear ribosomal DNA was sequenced in 36 samples representing 16 of the 17 species of Lasthenia. Phylogenetic analysis supported the monophyly of only section Hologymne whereas other sections are paraphyletic or polyphyletic. Species of section Baeria together with L. leptalea (section Burrielia) form a well supported clade. Samples of L. californica (section Baeria) form two clades representing geographically separated populations in a north-south pattern. Section Burrielia is polyphyletic and the ITS data suggest that different species of this section are more closely related to taxa of either sections Baeria or Ptilomeris. The monotypic section Platycarpha shares a close affinity with some species of section Ptilomeris. Species of section Ptilomeris formed two clades. One clade includes L. burkei, L. conjugens and L. fremontii supporting a close relationship among these species as previously recognized. The remaining species of section Ptilomeris form a well supported clade together with L. microglossa (section Burrielia). The basal position of L. glaberrima of section Lasthenia suggests that the ancestor to the genus may have been a self-compatible annual species with n = 5 and confined to wet habitats, a hypothesis that contradicts previous suggestions.

Communicating Editor: Alan T. Whittemore