Michael L. Moody

Evidence of hybridity in invasive watermilfoil (Myriophyllum) populations

Invasions of nonindigenous species have caused ecological devastation to natural communities worldwide, yet the biological bases for invasiveness remain poorly understood. Our studies of invasive watermilfoil (Myriophyllum) populations revealed widespread polymorphisms in biparentally inherited nuclear ribosomal DNA sequences, which were not detected in populations of native North American species. Subclones of the polymorphic regions revealed the occurrence of distinct sequences matching those acquired from both nonindigenous and native North American species. Molecular data demonstrate clearly that invasive watermilfoil populations in North America have resulted from hybridization between nonindigenous and native species. These observations suggest that invasiveness in these aggressive aquatic weeds may be linked to heterosis maintained by vegetative propagation.

Biogeography of discontinuously distributed hydrophytes : a molecular appraisal of intercontinental disjunctions

The extraordinarily wide distributional ranges of aquatic flowering plants have long stimulated phytogeographical discussion. Although aquatic plants occur rarely among the angiosperms, they represent a disproportionately large number of taxa with broad distributions including various intercontinental disjunctions that are manifest even at the species level. Throughout the nineteenth and early twentieth centuries, long‐range dispersal by waterfowl was the prevailing explanation for widespread aquatic plant distributions. This explanation gradually fell into disfavor as biologists raised doubts as to the ability of waterfowl to transport propagules across the extensive transoceanic distances between the continents on which an assortment of aquatic taxa now reside. During the twentieth century, the development of biogeographical displacement theory, i.e., “continental drift,” steadily began to supplant dispersal as the preferred explanation for discontinuous angiosperm distributions. Our study assesses the dispersal/displacement hypotheses from a temporal standpoint using molecular estimates of divergence time for a diverse sample of phylogenetically related aquatic taxa that exhibit discontinuous intercontinental distributions. With few exceptions, we found divergence times that are far too recent to implicate continental drift as a major determinant of discontinuous distributions in aquatic plants. We suggest that long‐distance dispersal by birds should continue to be regarded as a viable explanation for widely disjunct aquatic plant distributions, although such dispersal is likely to have involved a combination of overland as well as transoceanic migratory routes.

Phylogenetic relationships among Acanthaceae: evidence from noncoding trnL-trnF chloroplast DNA sequences

We used sequence data from the intron and spacer of the trnL-trnF chloroplast region to study phylogenetic relationships among Acanthaceae. This region is more variable than other chloroplast loci that have been sequenced for members of Acanthaceae (rbcL and ndhF), is more prone to length mutations, and is less homoplasious than these genes. Our results indicate that this region is likely to be useful in addressing phylogenetic questions among but not within genera in these and related plants. In terms of phylogenetic relationships, Elytraria (representing Nelsonioideae) is more distantly related to Acanthaceae sensu stricto (s.s.) than Thunbergia and Mendoncia. These last two genera are strongly supported as sister taxa. Molecular evidence does not support monophyly of Acanthaceae s.s., although there is strong morphological evidence for this relationship. There is strong support for monophyly of four major lineages within Acanthaceae s.s.: the Acanthus, Barleria, Ruellia, and Justicia lineages as here defined. The last three of these comprise a strongly supported monophyletic group, and there is weaker evidence linking the Ruellia and Justicia lineages as closest relatives. Within the Acanthus lineage, our results confirm the existence of monophyletic lineages representing Aphelandreae and Acantheae. Lastly, within the Justicia lineage, we develop initial hypotheses regarding the definition of sublineages; some of these correspond to earlier ideas, whereas others do not. All of these hypotheses need to be tested against more data.

Systematics of Seagrasses (Zosteraceae) in Australia and New Zealand

Abstract Previous taxonomic treatments of the family Zosteraceae in Australia/New Zealand have recognized Heterozostera tasmanica (monotypic) and four Zostera species all belonging to subgenus Zosterella: Z. capricorni, Z. muelleri, Z. mucronata, Z. novazelandica. Zostera has always been taxonomically problematic in Australia, where researchers have expressed difficulty with species recognition due to vague or inconsistent morphological characters. There also has been a lack of agreement on generic (notably the distinctness of Heterozostera) and subgeneric delimitation. Recent anatomical, developmental, and molecular studies urge a reevaluation of relationships in the family. To clarify the taxonomy of Zosteraceae, we investigated interspecific phylogenetic relationships focusing on Australian species of subgenus Zosterella. We examined material comprising all genera of Zosteraceae (Heterozostera, Nanozostera, Phyllospadix, Zostera), six/seven species of Zostera subgenus Zosterella (including all Australian/New Zealand species), and one of four species of Zostera subgenus Zostera. We conducted phylogenetic analyses of morphological data and DNA sequences from nuclear (ITS) and plastid (trnK intron, rbcL) genomes. Our results indicate two major clades (highly divergent at both morphological and molecular levels) and two subclades (with low morphological and molecular divergence) within Zosteraceae. Little morphological and molecular variation was observed among representatives within the clade of Australian/New Zealand members of subgenus Zosterella, and none provided cladistic support for taxa recognized formerly as separate species. We recommend that Zosteraceae comprise two genera (Phyllospadix, Zostera) with the latter subdivided into three subgenera (Zostera, Zosterella, Heterozostera). Furthermore, Australian/New Zealand representatives of Zostera subgenus Zosterella should be merged within a single species (Z. capricorni) to reflect the inability of morphological or molecular data to effectively delimit additional species in this group. Communicating Editor: Jeff H. Rettig

Phylogenetic Relationships among Acanthaceae: Evidence from Two Genomes

Abstract We used sequence data from the nuclear ribosomal internal transcribed spacer (nr-ITS) region, both alone and in combination with data from the intron and spacer of the trnL-trnF chloroplast (cp) region, to study phylogenetic relationships within the large tropical and subtropical family Acanthaceae. Substitution rate in the nr-ITS region is nearly twice that of the trnL-trnF cp region, and more than twice the rates of other cp loci that have been sequenced for members of Acanthaceae (i.e., rbcL, ndhF). In terms of phylogenetic relationships, the hypothesis based on ITS was largely congruent with the trnL-trnF results. Exceptions are Crossandra pungens and the two Acanthus species, which are placed enigmatically by nr-ITS data. The combined analysis provides strong support for a single hypothesis of relationships among Acanthaceae sensu stricto (s.s.) and their closest relatives. 1) Elytraria (representing Nelsonioideae) is more distantly related to Acanthaceae s.s. than Thunbergia and Mendoncia. 2) These last two genera are sister taxa and together are the sister group of Acanthaceae s.s. 3) Acanthaceae s.s. are monophyletic. 4) There are at least four major monophyletic lineages within Acanthaceae s.s.: the Acanthus, Barleria, Ruellia, and Justicia lineages. 5) These four lineages are related as follows: {Acanthus lineage [Barleria lineage (Justicia + Ruellia lineages)]}. 6) Within the Justicia lineage, there are at least five monophyletic sublineages, related as follows: {Odontonema sublineage [Stenostephanus sublineage (Henrya sublineage {Dicliptera + New World Justicia sublineages})]}. Communicating Editor: Jeff Rettig

A phylogenetic analysis of Hydrangeaceae based on sequences of the plastid gene matK and their combination with rbcL and morphological data

DNA sequences of the plastid gene matK were used alone and in combination with rbcL and morphological data in analyses of phylogenetic relationships in Hydrangeaceae. A suggested relationship of Hydrostachys to Hydrangeaceae was examined, but the maximum parsimony analyses of the matK data and the data set that combines matK and rbcL place Hydrostachys outside of Hydrangeaceae. The DNA sequence data sets both alone and in combination produced congruent results. A Jamesia + Fendlera clade (= subfamily Jamesioideae) was the sister of the rest of the family (= subfamily Hydrangeoideae). Two tribes, Philadelpheae and Hydrangeeae, are recognized in Hydrangeoideae. Philadelpheae included three primary clades: (1) Philadelphus + Carpenteria, (2) Deutzia + Kirengeshoma, and (3) Fendlerella + Whipplea. Relationships in Hydrangeeae remain poorly resolved. A Cardiandra + Deinanthe clade was placed robustly as the sister of the rest of the Hydrangeeae only in analyses in which matK sequences were combined with other data. Broussaisia, Decumaria, Dichroa, Pileostegia, Platycrater, and Schizophragma were nested among species of Hydrangea. Relationships in this Hydrangea clade (the most inclusive monophyletic group that included species of Hydrangea) were poorly resolved, except for the monophyly of (1) Decumaria, Pileostegia, and Schizophragma; (2) Broussaisia, Dichroa, Hydrangea hirta, and Hydrangea macrophylla; (3) Platycrater, Hydrangea involucrata, and Hydrangea aspera; and (4) Hydrangea anomala and Hydrangea section Cornidia. Conflict between the morphological and matK data weaken support for the monophyly of both Philadelpheae and the Hydrangea clade; however, the addition of the morphological data strengthens support for Hydrangeoideae, Hydrangeeae, and the sister group relationship of the Hydrangea clade and Cardiandra + Deinanthe.

Systematics of Vallisneria (Hydrocharitaceae)

Abstract Morphology, species delimitation, and interspecific relationships were evaluated in a phylogenetic context in the aquatic monocotyledon genus Vallisneria using a combination of morphological and molecular (nrITS, rbcL, trnK 5′ intron) data. Contrary to previous studies that recognized few species worldwide, we distinguished 12 species by molecular data, and an additional 2–3 species by morphological differences within groups that were invariant at the molecular level. Two new Vallisneria species ( V. australis , V. erecta ) are formally described. Other potentially novel species were detected from the cultivated material examined but require further study to elucidate their taxonomic status. Phylogenetic analyses indicated that vittate (caulescent) species (including Maidenia rubra) are not basal, but nested between two groups of rosulate (rosette) species. To preserve Vallisneria as monophyletic, a new combination is made ( V. rubra ) that accommodates the transfer of M. rubra to Vallisneria. Several taxonomic characters associated with the stigma morphology of pistillate flowers were found to represent suites of features related to pollination. In most cases, these character suites corresponded to a particular arrangement of filaments in the staminate flowers. The precise geographical origin of Vallisneria remains difficult to determine. However, we conclusively documented the presence of the Old World V. spiralis in Texas (United States), which constitutes the first authentic record of this nonindigenous species in North America.

Systematics of the Aquatic Angiosperm Genus Myriophyllum (Haloragaceae)

Abstract The angiosperm genus Myriophyllum (Haloragaceae) is among the most species-rich genera of aquatic core-eudicots. Myriophyllum has a cosmopolitan distribution with its center of diversity in Australia (> 37 endemics). The widespread invasive species of the genus (M. aquaticum, M. heterophyllum, and M. spicatum) have drawn attention from international natural resource managers. Myriophyllum species are notoriously difficult to identify using vegetative morphology alone, which commonly is all that is available for these highly clonal plants. The relationships among taxa have been difficult to determine with suspected parallelisms in sex expression, sepal and petal loss, and reduced stamen number. A molecular phylogenetic approach was taken to examine relationships among taxa and to employ molecular markers for the reliable identification of Myriophyllum species. This study included ≈ 80% of the known Myriophyllum species. Both nrDNA ITS and cpDNA matK and trnK data were used to examine phylogenetic relationships among species. The nrDNA ITS data proved highly variable and could differentiate between all but one species pair examined. These analyses also uncovered multiple cryptic species among Australian complexes. Phylogenetic results support major realignments in the subgeneric classification including a recombination for the rare monotypic genus Meziella, which was nested within Myriophyllum. Here we present the new combinations and taxa Myriophyllum subgenus Meziella , sections Pectinatum and Pelonastes , subsections lsophylleae and Nudiflorum with the new combination Myriophyllum trifidum to accommodate the former monospecific genus Meziella.

Phylogenetic relationships of Loasaceae subfamily Gronovioideae inferred from matK and ITS sequence data.

Members of subfamily Gronovioideae are distinctive among Loasaceae in their androecial and gynoecial simplicity. The four genera of the subfamily differ, however, in chromosome number, floral novelties, and pollen exine sculpturing, which led to suggestions that the Gronovioideae were polyphyletic. Phylogenetic analyses based on sequences of the chloroplast gene matK and the internal transcribed spacer region (ITS) of nuclear rDNA have been conducted using parsimony and maximum likelihood methods to assess the monophyly of Gronovioideae and to determine the sister group relationships of gronovioid genera. The results show Gronovioideae are monophyletic and placed as the sister to Mentzelia. Within Gronovioideae, Petalonyx is sister to a clade consisting of Cevallia, Gronovia, and Fuertesia. Among the remaining Loasaceae, subfamily Mentzelioideae, as originally circumscribed, is paraphyletic. Subfamily Loasoideae is placed as the sister to the Gronovioideae-Mentzelia clade.

Phylogenetic systematics and character evolution in the angiosperm family Haloragaceae

The poorly known Haloragaceae R. Br. (Saxifragales) are highly diverse in habit (small trees to submerged aquatics) and labile in floral merosity (2-4), both uncommon among the core eudicots. This family has a cosmopolitan distribution, but taxonomic diversity is concentrated in Australia. An explicit phylogenetic approach has not previously been utilized to examine relationships or character evolution in this family. We used molecular evidence from nrDNA ITS and cpDNA trnK and matK regions under both Bayesian and parsimony analyses to address phylogenetic relationships. Combined molecular analyses defined a monophyletic Haloragaceae with the woody genera (Haloragodendron, Glischrocaryon) sister to the rest. Relationships among many genera were well resolved, with genera as currently delimited generally well supported, although there were notable exceptions; a new genus (Trihaloragis) is recognized, and the aquatic genus Meionectes is again distinct from Haloragis. Three new species combinations are also recognized. There are multiple (two or three) origins of the submerged aquatic habit in the family and potentially an intermediate reversal to the terrestrial habit, neither previously demonstrated in a core eudicot family using an explicit phylogenetic hypothesis. Ancestral character analyses suggest two origins of trimerous flowers and multiple reductions to dimerous flowers throughout Haloragaceae.