A Revision of the Pantropical Moss Genus Leucophanes Brid.

About this book

Language: English

The species of the pantropical genus Leucophanes are characterized by a whitish-green appearance, mainly corticolous, turf-forming habit; multistratose structure of the leaf; production of leaf-tip gemmae, and short branching systems. A definition of leaf structure is based primarily on comparative morphology of young and adult leaves, perigonial bracts, and scale leaves of Leucophanes and those of the related genera Exodictyon, Exostratum, Arthrocormus, and Syrrhopodon. The leaf is a complex organ composed of a costa (with stereids, guide cells and hyalocysts) and a multistratose lamina. The multistratose lamina is considered to be composed of two sections, a basal unistratose, hyaline area and a multistratose section with a central layer of quadrangular chlorophyllous cells (living photosynthetic elements), the chlorocysts, arranged in a net-like pattern and surrounded, on each surface, by one or more layers of porose hyaline cells (devoid of protoplasm at maturity), the hyalocysts. Growth-habit and structural features displayed by the gametophytes of Leucophanes are considered adaptations for water retention. It is most likely that the life-form characteristic of the genus developed in relation to environmental stresses imposed by the corticolous habit in seasonally dry tropical forests.

Three subgenera, twelve species and six subspecies are recognized. Important characters in defining these taxa include leaf apex, shape and arrangement of chlorocysts as observed in surface view, size and shape of hyalocysts, composition of the multistratose lamina as seen in cross-sections (layers of hyalocysts, stereids and guide cells), pore size on the transverse walls, sexual condition, perichaetial leaves, and peristome and spore ornamentation.

Leucophanes is distributed in the tropical and subtropical areas of the world, particularly in central Africa, Malesia, Southern ]apan, Australia, the islands of the tropical Pacific and the Neotropics. There are two centers of species diversity, one in Africa and the other in Malesia and adjacent areas. Of these, Africa has the highest number of endemics with five species, while Malesia has two. The species are able to grow on both acidic and basic substrata. An active radiation to littoral forests appears to have taken place in some species, e.g., L. glaucum and L. octoblepharioides, while others appear to be strictly elements of inland tropical rain forests.

The genus is hypothesized to have originated in Laurasia (Southeast Asia) as early as the Lower to Upper Cretaceous. Its present day distribution reflects not only its paleohistory but also its efficient dispersal capabilities.

Contents

LIST OF TABLES 11
LIST OF FIGURES 11

I. INTRODUCTION 17

Historical Review 18

II. MATERIALS AND METHODS 31

Nomenclature 31
Taxonomic Concepts 32
Descriptions 33
Line drawings and Scanning Electron Microscope 34
Habitat 34
Geographical Distribution 35
Specimens Examined 36

III. HABITATOFLEUCOPHANES 36

IV. PLANT AND ANIMAL INTERACTIONS 40

V. EVOLUTIONARY ASPECTS 42

1. Relationships of Leucophanes with other members of the
Calymperaceae 42
2. Geographical History of Leucophanes 51

VI. TAXONOMIC TREATMENT 54

LEUCOPHANES 54
Key to Subgenera of Leucophanes 57
Key to Species and Subspecies of Leucophanes 58
SUBGENUS LEUCOPHANES 62
Leucophanes octoblepharioides 62
Subspecies octoblepharioides 67
Subspecies meijeri 68
Subspecies whittieri 69
Leucophanes angustifolium 69
Leucophanes milleri 74
Leucophanes seychellarum 77
Leucophanes serratulum 79
Leucophanes rodriguezii 81
Leucophanes molleri 84
Leucophanes unguiculatum 88
Leucophanes hildebrandtii 90
Leucophanes renauldii 92

SUBGENUS LEIONOTUS 95
Leucophanes candidum 95

SUBGENUS TRACHYNOTUS 100
Leucophanes glaucum 101

Subspecies glaucum 105

Subspecies nukahivense 106

Subspecies vittii 107

APPENDIX 1 109
APPENDIX 2 110

SPECIMENS EXAMINED 111
LITERATURE CITED 127
INDEX 135

Customer Reviews