Rodger C. Evans

Angiosperm phylogeny based on matK sequence information

Plastid matK gene sequences for 374 genera representing all angiosperm orders and 12 genera of gymnosperms were analyzed using parsimony (MP) and Bayesian inference (BI) approaches. Traditionally, slowly evolving genomic regions have been preferred for deep-level phylogenetic inference in angiosperms. The matK gene evolves approximately three times faster than the widely used plastid genes rbcL and atpB. The MP and BI trees are highly congruent. The robustness of the strict consensus tree supercedes all individual gene analyses and is comparable only to multigene-based phylogenies. Of the 385 nodes resolved, 79% are supported by high jackknife values, averaging 88%. Amborella is sister to the remaining angiosperms, followed by a grade of Nymphaeaceae and Austrobaileyales. Bayesian inference resolves Amborella + Nymphaeaceae as sister to the rest, but with weak (0.42) posterior probability. The MP analysis shows a trichotomy sister to the Austrobaileyales representing eumagnoliids, monocots + Chloranthales, and Ceratophyllum + eudicots. The matK gene produces the highest internal support yet for basal eudicots and, within core eudicots, resolves a crown group comprising Berberidopsidaceae/Aextoxicaceae, Santalales, and Caryophyllales + asterids. Moreover, matK sequences provide good resolution within many angiosperm orders. Combined analyses of matK and other rapidly evolving DNA regions with available multigene data sets have strong potential to enhance resolution and internal support in deep level angiosperm phylogenetics and provide additional insights into angiosperm evolution.

Phylogeny and classification of Rosaceae

Phylogenetic relationships among 88 genera of Rosaceae were investigated using nucleotide sequence data from six nuclear (18S, gbssi1, gbssi2, ITS, pgip, and ppo) and four chloroplast (matK, ndhF, rbcL, and trnL-trnF) regions, separately and in various combinations, with parsimony and likelihood-based Bayesian approaches. The results were used to examine evolution of non-molecular characters and to develop a new phylogenetically based infrafamilial classification. As in previous molecular phylogenetic analyses of the family, we found strong support for monophyly of groups corresponding closely to many previously recognized tribes and subfamilies, but no previous classification was entirely supported, and relationships among the strongly supported clades were weakly resolved and/or conflicted between some data sets. We recognize three subfamilies in Rosaceae: Rosoideae, including Filipendula, Rubus, Rosa, and three tribes; Dryadoideae, comprising the four actinorhizal genera; and Spiraeoideae, comprising Lyonothamnus and seven tribes. All genera previously assigned to Amygdaloideae and Maloideae are included in Spiraeoideae. Three supertribes, one in Rosoideae and two in Spiraeoideae, are recognized.

Phylogeny of subtribe Pyrinae (formerly the Maloideae, Rosaceae): Limited resolution of a complex evolutionary history

Generic relationships in the Pyrinae (equivalent to subfamily Maloideae) were assessed with six chloroplast regions and five nuclear regions. We also plotted 12 non-molecular characters onto molecular phylogenies. Chloroplast DNA trees are incongruent with those from nuclear regions, as are most nuclear regions with one another. Some of this conflict may be the result of hybridization, which occurs between many genera of Pyrinae in the present and may have occurred in the past, and duplication of nuclear loci. Sequence divergence between genera of Pyrinae, which is significantly less than that between genera of another large clade in Rosaceae, the Rosoideae, is concentrated in terminal branches, with short internal branches. This pattern is consistent with an ancient, rapid radiation, which has also been hypothesized from the fossil record. Even with about 500,000 bp of sequence, our results resolve only several small groups of genera and leave much uncertainty about phylogenetic relationships within Pyrinae.

FLORAL ONTOGENY AND MORPHOLOGY IN SUBFAMILY SPIRAEOIDEAE ENDL. (ROSACEAE)

“Spiraeoideae,” as traditionally circumscribed, contain the greatest diversity of floral organ morphology of any of the four subfamilies in the Rosaceae. Comparisons of mature floral morphology in 10 spiraeoid genera demonstrate that genera in this subfamily exhibit many floral character states present in the other three subfamilies. Inflorescence development, gynoecium initiation and development, ovule development and morphology, and obturator position all exhibit considerable variation in these taxa. Inflorescences vary from simple and racemose to multibranched and cymose. Gynoecial appendages can be initiated as independent primordia or from a shallow gynoecial ring primordium. Placentation occurs on the ventral margin of the ovary locule and includes apotropic ovules inserted near the base (Porteranthus and Vauquelinia), apotropic and pleurotropic ovules inserted the entire length or midway (Kageneckia and Physocarpus), and apically inserted epitropic ovules (Aruncus, Chamaebatiaria, Holodiscus, Lyonothamnus, Sorbaria, and Spiraea). Associated with the ovules of almost all genera is an obturator that may comprise cells of the funiculus or cells of both the funiculus and locule margin. These results corroborate those of other studies that suggest that the “Spiraeoideae” are an artificial, polyphyletic group.

PHYLOGENETIC ANALYSIS OF HEPATOZOON SPECIES (APICOMPLEXA: ADELEORINA) INFECTING FROGS OF NOVA SCOTIA, CANADA, DETERMINED BY ITS-1 SEQUENCES

Species of Hepatozoon are apicomplexan parasites infecting tetrapod vertebrates and hematophagous arthropods. Two species, Hepatozoon catesbianae and Hepatozoon clamatae, have been described inhabiting the erythrocytes of bullfrogs and green frogs. A number of characteristics typically used to distinguish between members of this genus are shared between these 2 species, prompting speculation as to whether or not these organisms are in fact distinct species. To test the species distinction, bullfrogs and green frogs were captured at various sites across Nova Scotia, blood samples were collected, and DNA was extracted from samples containing parasites. The internal transcribed spacer 1 (ITS-1) from geographically diverse samples of both species was amplified by PCR, sequenced, and analyzed. ITS-1 sequences from the 2 species revealed single-nucleotide polymorphisms at 6 sites. Phylogenetic analysis of these molecular data and cytopathological features place isolates of each species in separate monophyletic groups. Comparison of the ITS-1 sequences between isolates from Nova Scotia and Ontario revealed that ITS-1 sequences of H. catesbianae from a previous study were mischaracterized as being those of H. clamatae. Phylogenetic data based on molecular variation and cytopathological features from this study provide the strongest evidence to date supporting the distinction between these 2 species.

Floral Ontogeny and Morphology in Gillenia (“Spiraeoideae”) and Subfamily Maloideae C. Weber (Rosaceae)

A comparison of floral development in Gillenia (Rosaceae subfamily “Spiraeoideae”) with that in seven genera in subfamily Maloideae was undertaken to ascertain similarities between Maloideae and Gillenia floral development, as well as to ascertain the developmental basis for variation in mature Maloideae floral morphology. The analysis also sought information regarding the initiation and development of the syncarpous hypanthial ovary that is encountered in the majority of Maloideae taxa. While most taxa in this study initiated 20 stamens in three pentamerous whorls, flowers of Chaenomeles and Mespilus each initiated more than three whorls of stamens. Development of the gynoecium in all taxa was preceded by a ring primordium in the Maloideae and a flat‐topped primordium in Gillenia. Individual gynoecial units formed on these primordia and in all taxa except Cotoneaster remained connate throughout development. Except in Gillenia, intercalary growth beneath the common insertion point of the gynoecial primordia and adjacent hypanthium is responsible for adnation of the ovary wall and hypanthium observed in mature flowers. Ovule initiation and development for most taxa, including Gillenia, results in a pair of collateral, anatropous, and apitropic ovules, each associated with a funicular obturator. Two ovules were also initiated collaterally in Mespilus and Crataegus, but in these genera they subsequently become superposed. Multiple ovule primordia are initiated in Chaenomeles and Sorbus, but only Chaenomeles had more than two ovules at maturity. The results of this study are discussed in terms of previous studies of floral development in the Rosaceae and previous hypotheses regarding the origin of subfamily Maloideae from a Gillenia ancestor.

Floral Ontogeny and Morphology in Subfamily Amygdaloideae T. & G. (Rosaceae)

Relationships within the Amygdaloideae have long been a point of discussion in Rosaceae systematics. Oemleria, a monotypic genus, has been removed from the Amygdaloideae because of its five‐pistillate gynoecium since all other genera have a single pistil. Exochorda, with its capsular fruit, has traditionally been placed in Spiraeoideae. Nevertheless, recent phylogenetic analyses of wood anatomy and rbcL sequence variation have demonstrated that both Exochorda and Oemleria should be included in an expanded Amygdaloideae. Comparisons of floral ontogeny in Prunus, Oemleria, and Exochorda, and the mature morphology of these genera and Prinsepia, support inclusion of Oemleria and Exochorda in Amygdaloideae. Inflorescence development demonstrates a close relationship between Exochorda and Oemleria. Gynoecium development in Exochorda and Oemleria is similar in some ways to that of some members of the Maloideae. All genera have a pair of collateral, bitegmic ovules, each of which is associated with an obturator that is composed of cells of the ventral margin of the locule.

Characterization of early floral damage by cranberry tipworm ( Dasineura oxycoccana Johnson) as a precursor to reduced fruit set in rabbiteye blueberry ( Vaccinium ashei Reade)

The cranberry tipworm, Dasineura oxycoccana, is an important insect pest of rabbiteye blueberries, Vaccinium ashei, in the southeastern United States, with annual losses from infestation and damage exceeding

Lace plant ethylene receptors, AmERS1a and AmERS1c, regulate ethylene-induced programmed cell death during leaf morphogenesis.

20 million USD. Using rabbiteye flowers from a range of developmental stages, we examined floral tissues microscopically to determine specific areas targeted by D. oxycoccana, as well as the impact of oviposition and larval feeding. Our results indicate that oviposition by D. oxycoccana occurs early in the growing season, as larvae were found exclusively between bracts of expanding inflorescences and the base of developing flowers. When bracts were removed, tissue necrosis resulting from larval feeding was found encompassing the calyx tube region near the pedicel. Such damage potentially leads to premature floral bud abscission, or aesthetically compromised fruit when mature. In the field, evidence of D. oxycoccana infestation would be undetectable until overlying bracts had abscised, and damage had already progressed to an extreme state.

Honey bee-collected pollen in agro-ecosystems reveals diet diversity, diet quality, and pesticide exposure

The lace plant, Aponogeton madagascariensis, is an aquatic monocot that forms perforations in its leaves as part of normal leaf development. Perforation formation occurs through developmentally regulated programmed cell death (PCD). The molecular basis of PCD regulation in the lace plant is unknown, however ethylene has been shown to play a significant role. In this study, we examined the role of ethylene receptors during perforation formation. We isolated three lace plant ethylene receptors AmERS1a, AmERS1b and AmERS1c. Using quantitative PCR, we examined their transcript levels at seven stages of leaf development. Through laser-capture microscopy, transcript levels were also determined in cells undergoing PCD and cells not undergoing PCD (NPCD cells). AmERS1a transcript levels were significantly lower in window stage leaves (in which perforation formation and PCD are occurring) as compared to all other leaf developmental stages. AmERS1a and AmERS1c (the most abundant among the three receptors) had the highest transcript levels in mature stage leaves, where PCD is not occurring. Their transcript levels decreased significantly during senescence-associated PCD. AmERS1c had significantly higher transcript levels in NPCD compared to PCD cells. Despite being significantly low in window stage leaves, AmERS1a transcripts were not differentially expressed between PCD and NPCD cells. The results suggested that ethylene receptors negatively regulate ethylene-controlled PCD in the lace plant. A combination of ethylene and receptor levels determines cell fate during perforation formation and leaf senescence. A new model for ethylene emission and receptor expression during lace plant perforation formation and senescence is proposed.