Comparative Pollen Morphology of the American Myristicaceous Genera Compsoneura and Virola

Abstract

Pollen of the American myristicaceous genera Compsoneura and Virola was studied with light, scanning electron, and transmission electron microscopy. Formal generic pollen descriptions are provided for each of these genera. Study of the pollen of these two genera reveals that they possess a number of similar palynological features, including sulcate apertures, reticuloid to reticulate exine sculpturing that sometimes consists of banded or beaded muri, a columellate interstitium with columellae frequently hanging from the tectum or only weakly attached to the nexine. and tectate-perforate to semitectate pollen grains. Pollen of Compsoneura, however, can be distinguished from that of Virola by (1) its nexine which is generally twice as thick as that in Virola, (2) its consistently more or less solid, nonlamellate nexine, and (3) its consistently inconspicuous intra-exinous, sexinous cavities. Within Compsoneura, pollen of section Coniostele is decidedly more advanced than that of section Compsoneura. Virola exhibits a wide range of exine sculpturing patterns, allowing recognition of three basic pollen types. Species of Pollen Type I have basically tectate-perforate grains although sometimes their pollen may be more or less reticuloid, and the exine surface or muri are usually psilate. Pollen Type II is characterized by tectate-perforate to semitectate grains which have banded to beaded muri, while Type III pollen grains are semitectate-reticulate with psilate muri. This is the fourth paper in a series dealing with the comparative pollen morphology of the family Myristicaceae. In previous papers we have already dealt with the pollen of the Madagascan (Walker & Walker, Grana, in press) and mainland African (Walker & Walker, Amer, J. Bot., 1, in press) genera of Myristicaceae, and with the American myristicaceous genera Dialyanthera, Iryanlhera, and Osteophloeum (Walker & Walker, Amer. 7. Bot., 2, in press). We are concerned in this paper with the pollen of the two remaining genera of American Myristicaceae â€" Compsoneura and Virola. We intend to examine the pollen of the Asian genera of Myristicaceae in subsequent papers.In the most recent revision of the American Myristicaceae, Smith (1938) recognized 8 species of Compsoneura and 38 species of Virola. Since then 2 additional species of Compsoneura and 9 more of Virola have been described, so that at present there are 10 species of Compsoneura and approximately 50 species of Virola. Compsoneura and Virola range from southern Mexico to northern South America, where most of their species occur.After the material and methods section, formal generic pollen descriptions are provided for both of the genera studied. This is followed by a discussion of the palynological features of these two genera, such as aperture type, exine sculptur-* We thank the directors of the following herbaria for allowing us to collect palynological material

Notes on the Pollen Morphology and Phylogeny Restionales and Poales

“…In the Poaceae the tectum and foot layer are perforated by intra-exinous channels running parallel and at right angles to the outer surface (these seem very similar to the 'conspicuous small spherical intra-exinous cavities' described in Myristicaceae by Walker & Walker 1979). These channels have not been observed in any of the other taxa (Fig.…”

Early evolution of angiosperm pollen as inferred from molecular and morphological phylogenetic analyses

“…Nexine stratification scored as foliated (2) rather than (1). Myristicaceae: Walker & Walker (1979, 1980, . Reconstruction of ancestral states for infratectal structure (columellar), tectum (reticulateperforate), nexine stratification (foliated, thus scored 2 rather than 1), and nexine thickness (0/1) is discussed in .…”

The vegetation history of an Amazonian domed peatland

“…Identifications were based on pollen reference slides, the pollen atlases of Roubik and Moreno (1991) and Colinvaux et al (1999), the Neotropical Pollen Database (Bush and Weng, 2006) and other literature (Absy, 1979;Walker and Walker, 1979;Andersson, 1993;Weber et al, 1999;Van Geel, 2001; Nowicke and Takahashi, 2002;Dias Saba, 2007;Burn and Mayle, 2008). Mauritia and Mauritiella are morphologically similar but reference material differs systematically in size between the two genera ( Fig.…”