A revision of asterogyne (Arecaceae: Arecoideae: Geonomeae)

A taxonomic revision of the neotropical genusAsterogyne Hook. (Arecaceae: Arecoideae: Geonomeae) is presented. The genus is characterized by one autoapomorphic character, the separation of anther thecae by a bifid connective, and the combination of small to medium-sized stems, bifid simple leaf blades, floral pits in bud covered by a rounded upper lip that overlaps a lower lip, and pistillate flowers with staminodial lobes that are displayed in a starlike shape. Five species are recognized in this treatment: one of them (Asterogyne martiana) is widely distributed from Belize in Central America to northern Ecuador, three species (A. ramosa, A. spicata, andA. yaracuyense) are endemic to small areas in the Venezuelan Coastal Range, and one species (A. guianensis) is endemic to eastern French Guiana. The taxonomic history, morphology, reproductive biology, distribution and ecology, intrageneric relationships, and conservation status are reviewed.     

The occurrence and structure of apparently bisexual flowers in the date palm, Phoenix dactylifera L. (Arecaceae)

Individuals of Phoenix dactylifera L. have expanded pistillodes or pseudocarpels in staminate flowers. These pseudocarpels are located in the centre of the male flowers and are surrounded by stamens. The gynoecium has the characteristic three carpellate arrangement commonly found in female date palm flowers. Pseudocarpels from male flower buds can expand into parthenocarpic fruit. Histology of the expanded pistillodes or pseudotarpels is similar to that of normal carpels from pistillate plants. These pseudocarpels lack ovules. Nutrient medium containing 10 mg 1^-1 of 2,4-dichlorophenoxyacetic acid or p-chlorophenylacetic acid and 0.3% activated neutralized charcoal enhanced the development and outgrowth of the pseudocarpels of cultured male flowers.     

Comparative floral structure and systematics in the Asian palm genus Rhapis (Arecaceae,Coryphoideae)

A comparative study of the floral structure in the species of the genus Rhapis (Arecaceae, Coryphoideae, Rhapidinae) is presented. Flowers are mainly unisexual, with three sepals, three petals, 6 stamens or staminodes and three carpels or carpellodes. Some evidences of basal congenital and apical postgenital fusion of the carpels, first time reported in the genus, were observed in the gynoecium. Ovules are basally attached and crassinucellate; they appear to be slightly anatropous. The morphology of the filaments suggests a division of the species into two groups: Rhapis excelsa and R. subtilis exhibit thick and keeled filaments, whereas R. gracilis, R. humilis, R. laosensis, R. micrantha and R. multifida have slender, non-keeled filaments. Relationships of Rhapis with the rest of the genera of Rhapidinae are inferred on the light of floral structure.     

Hair morphology and systematics ofPhysalis (Solanaceae)

Hair morphology was exammed on developing seedlings and mature plants of ten species from five of seven series inPhysalis. The taxonomic importance of hair development and the distribution of hair types then was evaluated with respect to other comparative data. Two classes of hair types were observed, as found in earlier investigations ofSolanum andRhododendron. The first hair class comprises a sequence from unbranched hairs to dendroid-stelliform hairs. Hairs of this class show considerable variability among taxa in size, presence or absence of glandular tips, and presence and degree of branching, and so were useful in making taxonomic comparisons. The second hair class consists of short hairs, each tipped with a multicellular gland. This second hair class was not useful taxonomically because of its lack of variability in morphology and its often rare occurrence on a plant. The taxa studied exhibit distinctive trichome features which serve to distinguish series and, in some cases together with other data, provided new insight into previously enigmatic species relationships.     

Turbellaria Lecithoepitheliata: morphology,systematics, phylogeny

A review of the literature on the world fauna of lecithoepitheliata and Prolecithophora and extensive observations by the author on species of the Prorhynchidae, including cosmopolitan species as well as some endemic to Lake Baikal, and on endemic species of Baicalarctiinae (Prolecithophora) show that the Prorhynchidae and Gnosonesimidae are properly classified in the Neoophora. The morphological similarity of the Prorhynchidae and Prolecithophora proves these taxa are closely related. A hypothesis relating the Lecithoepitheliata Prorhynchidae to primitive prolecithophorans appears to be the only tenable hypothesis on the phylogeny of Lecithoepitheliata. The question of whether the Lecithoepitheliata is monophyletic still needs investigation; more evidence on the phylogeny of the Gnosonesimidae is needed.     

Floral structure and development in the monoecious palm Gaussia attenuata (Arecaceae; Arecoideae)

Background and Aims

Sexual dimorphism, at both the flower and plant level, is widespread in the palm family (Arecaceae), in contrast to the situation in angiosperms as a whole. The tribe Chamaedoreeae is of special interest for studies of the evolution of sexual expression since dioecy appears to have evolved independently twice in this group from a monoecious ancestor. In order to understand the underlying evolutionary pathways, it is important to obtain detailed information on flower structure and development in each of the main clades.

Methods

Dissection and light and scanning electron microscopy were performed on developing flowers of Gaussia attenuata, a neotropical species belonging to one of the three monoecious genera of the tribe.

Key Results

Like species of the other monoecious genera of the Chamaedoreeae (namely Hyophorbe and Synechanthus), G. attenuata produces a bisexual flower cluster known as an acervulus, consisting of a row of male flowers with a basal female flower. Whereas the sterile androecium of female flowers terminated its development at an early stage of floral ontogeny, the pistillode of male flowers was large in size but with no recognizable ovule, developing for a longer period of time. Conspicuous nectary differentiation in the pistillode suggested a possible role in pollinator attraction.

Conclusions

Gaussia attenuata displays a number of floral characters that are likely to be ancestral to the tribe, notably the acervulus flower cluster, which is conserved in the other monoecious genera and also (albeit in a unisexual male form) in the dioecious genera (Wendlandiella and a few species of Chamaedorea). Comparison with earlier data from other genera suggests that large nectariferous pistillodes and early arrest in staminode development might also be regarded as ancestral characters in this tribe.     

Morphology and development of the female flowers in Geonoma interrupta (Arecaceae)

Morphology and development of the female flowers in Geonoma interrupta are described and compared with other taxa within Arecaceae. Inflorescences are pleiothyrses. Cincinni are immersed in pits and arranged according to the Fibonacci pattern along the rachillae. The gynoecium is composed of three free carpels in early stages and later becomes pseudomonomerous. Two carpels are sterile; they develop to different degrees and are commonly unequal in size. The fertile carpel contains a single, crassinucellate, anatropous ovule. Styles are formed in each carpel. The style of the fertile carpel becomes basifixed as the ovary enlarges. The stigmas remain free and plicate during development and expose unicellular papillae at anthesis. Pollen tube transmitting tracts and a compitum are present in the ventral slits of the stigmas and the postgenitally united styles during anthesis. A septal nectary is formed by incomplete union of the flanks of the carpels at the base of the gynoecium, and nectar is secreted from an epithelium. It is suggested that in Geonoma as a whole, the attraction of pollinators to female flowers is due to a combination of nectar reward and partial mimicry of male flowers.     

Nuclear DNA Amounts in Palms (Arecaceae)

Nuclear DNA amounts are reported for 83 species and 53 genera of palms, covering all of the six subfamilies. 4C DNA contents range between 3.89 and 55.62 pg in diploids, showing an approximate 14.3-fold variation in genome size. Polyploids have DNA contents of up to 156.40 pg/4c which demonstrates a 40.2-fold variation. Diploids with high DNA contents occur in three subfamilies of palms (Coryphoideae, Calamoideae, Arecoideae), and seem to be further restricted to particular tribes or subtribes (Thrinacinae, Borasseae, Lepidocaryeae, Caryoteae, some subtribes of Areceae). Palms from the subfamilies Nypoideae and Phytelephantoideae have the lowest DNA amounts, followed by the Phoeniceae and the Corypheae: Livistoninae from the subfamily Coryphoideae. Although DNA amounts in some genera and subtribes are usually constant, e.g., in Phoenix, Phytelephas, the Livistoninae, Dypsidinae, diploid Butiinae), considerable variation occurs at the diploid level in some large and apparently actively evolving genera such as Chamaedorea, Pinanga, Cenoma and possibly Bactris. Formaldehyde fixation is recommended for palms, as conventional ethanol-acetic acid fixation has proved to be unsuitable for DNA estimation of Feulgen-stained nuclei by microdensitometry, since it can lead to errors up to 2.5-fold in extent. Chromosome counts are reported for 72 of the species studied, of which 42 are new.     

Morphological systematics of Serapias L. (Orchidaceae) in Southwest Europe

We measured morphological characters and relative DNA contents to assess variation and phylogenetic relationships among Serapias species in three populations of each of the 10 putative taxa that occur in Southwest Europe. DNA contents indicated diploidy for most species, except for tetraploid S. lingua and hexaploid S. olbia. Multivariate (discriminant) analyses yielded two main groups: a small-flowered S. parviflora group and a large-flowered S. vomeracea group. Within the S. parviflora group, S. elsae should be considered a large-flowered variation of S. strictiflora. The geographically disjunct S. gregaria and S. strictiflora are probably different taxa. In the S. vomeracea group, analyses suggest that S. neglecta and S. cordigera are closely related. Serapias cordigera from the southwestern coast of the Iberian Peninsula is probably a subspecies, S. perez-chiscanoi was separated from all other species and S. occidentalis was morphologically intermediate between S. cordigera and S. vomeracea, suggesting a hybrid origin, with the latter two taxa as parents.     

Twenty-five years of progress in understanding pollination mechanisms in palms (Arecaceae)

BACKGROUND: With more than 90 published studies of pollination mechanisms, the palm family is one of the better studied tropical families of angiosperms. Understanding palm-pollinator interactions has implications for tropical silviculture, agroforestry and horticulture, as well as for our understanding of palm evolution and diversification. We review the rich literature on pollination mechanisms in palms that has appeared since the last review of palm pollination studies was published 25 years ago. SCOPE AND CONCLUSIONS: Visitors to palm inflorescences are attracted by rewards such as food, shelter and oviposition sites. The interaction between the palm and its visiting fauna represents a trade-off between the services provided by the potential pollinators and the antagonistic activities of other insect visitors. Evidence suggests that beetles constitute the most important group of pollinators in palms, followed by bees and flies. Occasional pollinators include mammals (e.g. bats and marsupials) and even crabs. Comparative studies of palm-pollinator interactions in closely related palm species document transitions in floral morphology, phenology and anatomy correlated with shifts in pollination vectors. Synecological studies show that asynchronous flowering and partitioning of pollinator guilds may be important regulators of gene flow between closely related sympatric taxa and potential drivers of speciation processes. Studies of larger plant-pollinator networks point out the importance of competition for pollinators between palms and other flowering plants and document how the insect communities in tropical forest canopies probably influence the reproductive success of palms. However, published studies have a strong geographical bias towards the South American region and a taxonomic bias towards the tribe Cocoseae. Future studies should try to correct this imbalance to provide a more representative picture of pollination mechanisms and their evolutionary implications across the entire family.     

On the information content of characters in comparative morphology and molecular systematics

A review of the fundamental difference between single molecular-sequence positions, or numerical characters, and complex morphological characters is the subject of this study. It has been found that transformation series of single complex structures contain enough information to allow a priori determination of character order and that rooting of a dendrogram is possible without out-group comparison, while trees based on less-informative characters can usually only be rooted with out-group comparison. Furthermore, the quality of total information used is decisive in discriminating between hypotheses of relationships. Numerical methods for the inference of phylogenies have been found to be useful for high numbers of characters that have only a low information content, while the Hennigian procedure seems to be preferable for complex characters.

Zusammenfassung

Ein fundamentaler Unterschied zwischen der einzelnen Sequenzposition oder auch numerischen Merkmalen und komplexen morphologischen Merkmalen ist ihr Informationsgehalt. Merkmalsreihen komplexer Strukturen enthalten meist genügend Information, um a priori die Bestimmung der Lesrichtung zu ermöglichen. Die Feststellung des Ursprunges eines Dendrogramms ist somit ohne kladistischen Außengruppenvergleich möglich, während Bäume (Topologien), die auf wenig informativen Merkmalen beruhen, allgemein nur mit dem kladistischen Außengruppenvergleich 'gewurzelt' werden können. Die Qualität der insgesamt verwendeten Information ist entscheidend für die Wahl zwischen alternativen Verwandtschaftshypothesen. Numerische Methoden der Rekonstruktion der Phylogenese sind nützlich bei Verwendung einer gro β en Zahl informationsarmer Merkmale; das Hennigsche Verfahren ist für komplexe Merkmale vorzuziehen.     

On the information content of characters in comparative morphology and molecular systematics

A review of the fundamental difference between single molecular-sequence positions, or numerical characters, and complex morphological characters is the subject of this study. It has been found that transformation series of single complex structures contain enough information to allow a priori determination of character order and that rooting of a dendrogram is possible without out-group comparison, while trees based on less-informative characters can usually only be rooted with out-group comparison. Furthermore, the quality of total information used is decisive in discriminating between hypotheses of relationships. Numerical methods for the inference of phylogenies have been found to be useful for high numbers of characters that have only a low information content, while the Hennigian procedure seems to be preferable for complex characters.     

Pattern of morphological variation and diversity of Cocos nucifera (Arecaceae) in Mexico

The pattern of morphological variation of Cocos nucifera in Mexico was statistically and numerically evaluated. Forty-one populations were analyzed, using 17 morphological fruit characters. Principal components and cluster analyses indicated four main groups of coconut populations that showed high similarity with four different genotypes recently imported into Mexico from areas that could be the origin of Mexican coconut populations. These four genotypes were evaluated with regard to the lethal yellowing disease in Jamaica and showed a differential susceptibility. Therefore it is possible to speculate upon a difference in susceptibility of the Mexican genotypes. The analysis of correlation between morphological and geographical distances showed a high positive correlation that supports: (1) historical evidence that indicates early introductions of coconut from different regions of the world, (2) that on both coasts of Mexico two different patterns of dispersal were involved: continuous and in jumps. Collectively these results suggest that the impact of the lethal yellowing disease on coconut populations will vary depending on the specific area and the origin of its coconuts.     

A systematic histological study of palm fruits. V. Subtribe Archontophoeniciae (Arecaceae)

Pericarp histology in the Archontophoenicinae provides little to characterize the subtribe as a whole, revealing instead two separate trends with parallels in other subtribes of the Areceae. The data support a close relationship among the three genera occurring in New Caledonia:Chambeyronia, Actinokentia, andKentiopsis, in which there is a complex endocarp consisting of short, oblique fibrous bundles embedded in a thick mantle of brachysclereids, and a loose endocarp of heavily fibrous, flattened vascular bundles adjacent to a relatively thin locular epidermis. The data also support a close relationship between the two genera of the New Zealand/Tasman Sea region:Hedyscepe andRhopalostylis, in which the pericarp is more or less fibrous throughout, with purely fibrous bundles in the outer pericarp and heavily fibrous vascular bundles in the inner pericarp. These results confirm relationships revealed by other morphological data.Archontophoenix appears to be most like the New Caledonian genera in its pericarp structure, with a similar mantle of short fibrous bundles embedded in a a mantle of brachysclereids in the outer pericarp, although it differs significantly in other aspects of morphology and anatomy.     

蝗虫分子系统学研究进展

本文从遗传多样性、近缘种鉴别以及分子进化和系统发育重建 3个方面综述了蝗虫分子系统学的研究进展。     

A systematic histological study of palm fruits. IV. Subtribe Oncospermatinae (Arecaceae)

Pericarp histology in the Oncospermatinae reveals distinctive characters at the generic level but no unique characters at the subtribal level. Pericarp structure is diverse but parallels the diversity found in other subtribes of the Areceae. The subtribe appears to be divisible into two distinct groups: one in which sclereids alone provide the primary protective barrier in the outer fruit and one in which fibrous bundles, some-times in combination with brachysclereids, form the outer barrier. This division of the subtribe supports similar conclusions derived from morphological data.     

A systematic histological study of palm fruits. VI. Subtribe Linospadicinae (Arecaceae)

The pericarp structure of representative species of the four genera of the subtribe Linospadicinae is described and compared. Tissues found in the pericarp of this group are similar to those found in other subtribes of the Areceae, with no characters unique to the subtribe and nothing to suggest its closest affinities. The four genera, as well as each species examined, do show distinctive pericarp features, however.Laccospadix andLinospadix are similar, both with a single series of fibrous, bundles and an outer series of prominent raphide-bearing cells dominating the pericarp. In bothHowea andCalyptrocalyx, a complex exocarp forms from a series of fibrous bundles and brachysclereids, but each genus has other distinctive characters.Howea has vascular bundles in the exocarp zone, an outer series of raphide-bearing cells, and a conspicuously thickened locular epidermis. Based on a limited sample of four species, raphide-bearing cells appear to be always interior to the exocarp inCalyptrocalyx, and the locular epidermis is thin.