Michael A. Vincent

Stem diversity, cauline domatia, and the evolution of ant–plant associations in Piper sect. Macrostachys (Piperaceae)

Plants possess a variety of structures that harbor ant nests, and the morphology of these domatia determines the nature of ant-plant mutualisms in a given plant species. In this study, we report on the differences in anatomy between myrmecophytes of Piper, which are regularly excavated by an obligate ant mutualist (Pheidole bicornis) and nonmyrmecophytes of Piper, which consistently have solid stems. Stems of excavated plant species lacked outward evidence of modification; however, striking anatomical differences were apparent between hollow-stemmed species before excavation and the remainder of the solid-stemmed species studied. Prior to excavation by ants, stems of myrmecophytes were characterized by strongly heterogeneous piths in which a large, central area had relatively large cells lacking intracellular crystals with a periphery of smaller cells containing numerous crystals. The domatium excavated by the ants was restricted to the large-celled region. This is the first report of the absence of crystals in ant-excavated portions of stems of myrmecophytes. Cauline domatia became lined with 3-8 cell layers of suberized wound tissue, which may have an impact on nutrient absorption by Piper myrmecophytes.

Phylogenetic Patterns, Evolutionary Trends, and the Origin of Ant—Plant Associations in Piper section Macrostachys: Burger’s Hypotheses Revisited

In Flora Costaricensis, William Burger of the Field Museum in Chicago considered eight of the Piper species that occur in Costa Rica to make up the P. obliquum complex, and six additional species to be closely allied to it (Fig. 9.1; Burger 1971). Piper calcariformis, an additional species assignable to the P. obliquum complex, was later described by Tebbs (1989). Although Burger did not apply a system of infrageneric classification in Flora Costaricensis (1971), these 15 species of the P. obliquum complex and its allies represent all of the Costa Rican members of Piper sect. Macrostachys (Miq.) C.DC. Besides discussing the relationships between species, Burger (1972) also made hypotheses concerning evolutionary trends among the Costa Rican Piper species. In addition, he was among the first to note that certain Piper species have a tendency to support associations with ants. All known obligate ant-plants among New World Piper are found within the P. obliquum complex and its allies. In this chapter, we revisit Burger’s hypotheses regarding systematic relationships and evolutionary hypotheses, and explore the evolution of ant-plant associations more fully in the broader context of Piper sect. Macrostachys using a molecular phylogenetic approach.

Systematics, Taxonomy, and the New Flora of the Bahamian Archipelago

A history of botanical exploration in the Bahama Archipelago is given, and is presented in three sections. The first section begins with the earliest botanical collections in 1700 by Thomas Walker and describes, in chronological order, botanical collections made up to 1920, when Britton and Millspaugh published the first Bahama flora. The second section chronicles botanical research in the archipelago after 1920, up until the publication by Correll and Correll of the Flora of the Bahama Archipelago in 1982. The third section describes plant research in the archipelago between 1982 and the present day. Following a brief rationale for the need for a new flora, the present research toward the flora is discussed, and an example of changes in the flora since 1982 is presented, with changes in the fern flora tabulated.ResumenSe da una historia de la exploración botánica en el archipiélago de Bahamas, y se presenta en tres secciones. La primera sección comienza con las colecciones botánicas más tempranos en 1700 por Thomas Walker y describe, en orden cronológico, las colecciones botánicas hizo hasta 1920, cuando Britton y Millspaugh publicaron la primera flora Bahama. La segunda sección de la crónica de la investigación botánica en el archipiélago a partir de 1920, hasta la publicación por Correll y Correll de la Flora del archipiélago de Bahamas en 1982. La tercera sección describe la investigación de plantas en el archipiélago entre 1982 y la actualidad. Después de una breve justificación de la necesidad de una nueva flora, se discute la investigación actual hacia la flora, y un ejemplo de los cambios en la flora desde 1982 se presenta, con los cambios en la flora de helechos tabulados.

Akanthomyces johnsonii, a saprophytic synnematous hyphomycete

Pistillaria johnsonii is transferred to the anamorph genus Akanthomyces and redescribed and illustrated from herbarium specimens and cultures. The species produces white indeterminate synnemata with phialidic conidiogenous cells and catenate ameroconidia, and occurs on decaying leaves and herbaceous litter, often in association with species of Botryosporium.

EFFECTS OF THE PYRIDAZINONE HERBICIDE SANDOZ 6706 (METFLURAZON) ON PIGMENTATION OF FUNGI

The herbicide Sandoz 6706 (metflurazon) inhibits carotene biosynthesis and allows photobleaching of chlorophyll in light-grown green plants. To explore its effects in non-photosynthetic organisms, the influence of metflurazon on pigmentation of nine soil-inhabiting fungi, representing a broad taxonomic spectrum, was investigated. Metflurazon treatment reduced observable intensity of pigmentation in many of these fungi. In the yeast Rhodotorula glutinis, herbicide treatment decreased /-carotene concentrations and increased the levels of phytoene, a colorless precursor of /-carotene. These results suggest that, in this yeast, metflurazon either inhibits a phytoene dehydrogenase or prevents end-product inhibition of phytoene production. Thus, one mechanism of action of the herbicide in R. glutinis is similar to that proposed for some photosynthetic organisms.

A New Taxonomy For Trifolium variegatum and Its Relatives

Abstract Two related species of Trifolium L. endemic to western North America, T. variegatum Nutt. s. l. and T. polyodon Greene, are studied. Multivariate analyses and morphological differences suggest that three species should be recognized instead of two. Trifolium variegatum is divided into two species: T. appendiculatum Lojac. and T. variegatum. Trifolium appendiculatum (including T. rostratum Greene) is a large-flowered species endemic to California and southern Oregon. Trifolium variegatum is found throughout western North America and remains the most diverse, but is now circumscribed by a consistent floral morphology. Trifolium polyodon is restricted to the Monterey peninsula and has distinctive calyx lobe teeth; its circumscription remains unchanged.

A NEW COMBINATION IN TRIFOLIUM VARIEGATUM (FABACEAE)

Abstract A new combination, Trifolium variegatum var. geminiflorum is proposed, and a key is provided for varieties of T. variegatum.