NSF-PEET Project in Systematic Bryology

Revision of the Moss Genus Holomitrium Bridel (Dicranaceae).

for fulfillment of a Ph.D. thesis

at Missouri Botanical Garden and University of Missouri- St Louis

Michelle Judith Price

[Currently Under Construction ]

Introduction to Holomitrium

Thesis Committee

Research Objectives

 Holomitrium names list 

 Holomitrium descriptions and keys (example)

Holomitrium images and illustrations (example)

Cladistic morphological analysis

Phylogenetic relationships of Holomitrium,

 Distribution of Holomitrium


Ph. D. Thesis project on Holomitrium (Dicranaceae: Musci). Introduction

Holomitrium is a predominantly tropical moss genus of around 50 species found in Australasia, Africa and the Americas. It is one of the most widespread and morphologically diverse of the epiphytic genera in the Dicranaceae. It is also one of the largest genera in the subfamily Dicranoideae to remain un-revised to date. Holomitrium is most commonly found as a canopy epiphyte in montane forest zones and is distinctive in its long, sheathing perichaetial leaves.

Systematic relationships both within the genus and within the subfamily Dicranoideae will be investigated using morphological cladistic and molecular systematic techniques. Back to TOP

Holomitrium grows as cushions and stems are to 4-5(10) cm in length. Leaves are noticably crisped and curled when dry, spreading when wet. If the plants are fertile they can be easily distinguished by the long, sheathing perichaetial leaves. The genus is tentatively assumed to be monophyletic and is characterized by: 1) long sheathing perichaetial leaves; 2) 16 more or less undivided, fenestrate peristome teeth; 3) pronounced differentiation of cells from lower to upper leaf; 4) well developed alar cells; and 5) entire or crenate to serrate leaf margins.

Preliminary morphological studies have revealed that Holomitrium falls into two main groups based on leaf margin characters. One group from Central America, South America and the Caribbean and one group from Africa and Australasia. These two groups are marked by serrate-crenulate or toothed margins versus entire margins, respectively. The neotropical taxa in Holomitrium are very closely related to two small genera, Eucamptodontopsis and Schliephackea. The relationships between these three genera will be investigated during the course of this work. Back to TOP

Significance: This study will be the first to revise the genus Holomitrium on a global scale and the first to investigate its biogeographical and phylogenetic relationships in detail. The work will contribute to the understanding of a large component of the subfamily Dicranoideae and to the understanding of the systematic relationships both within it and within the Dicranaceae.

 Back to TOP

Thesis Committee

Advisor: Dr. R.E. Magill. Missouri Botanical Garden

Co-advisor: Dr. E. Kellogg. University of Missouri - St. Louis

Dr. Bette Loiselle. University of Missouri - St. Louis

Dr. E. de Silva. University of Missouri - St. Louis

Chairman: Dr. P.M. Richardson. Missouri Botanical Garden/University of Missouri - St. Louis

External advisor: Dr. S.P. Churchill. Missouri Botanical Garden

Back to TOP


Research Objectives


Complete a taxonomic treatment of Holomitrium


Evaluate the Holomitrium - Eucamptodontopsis - Schliephackea relationship


Establish the monophyly of Holomitrium


Complete phylogenetic analyses Holomitrium and closely related genera in the Dicranoideae


Investigate the biogeography of the group


Use phylogenetic tools to investigate character trends and diversification patterns in Holomitrium

Back to TOP

Back to TOP

Original drawing of type specimen of the genus Holomitrium


Back to TOP

Images of Holomitrium (example)

Images taken using PIXERA digital camera linked to PIXERA system software and with a Cannon SLR ESO


Upper leaf cells

Serrate leaf margins

Lower leaf cells

Peristome: Price 07, Ecuador


Crenulate leaf cells (upper leaf)

Entire leaf margin: Price 07, Ecuador

Alar cells

Dwarf male plant: H. arboreum

Back to TOP

Phylogenetic relationships - Holomitrium, the Dicranoideae and the Dicranaceae.

The Dicranaceae belong to a monophyletic group of mosses, the Haplolepideae, consisting five orders of mosses characterized by a particular pattern of peristome development. The Dicranaceae contains over 1000 species and around 50 genera divided among several weakly demarcated subfamilies: Ansiothecioideae, Campylopoideae, Dicranoideae, Meiosiothecioideae, Paraleucobryoideae, Rhabodoweisioideae and Trematioideae (Brotherus 1924; Frahm 1991; Allen 1994). Using two gene regions (ITS and trnL-trnF) the phylogeny of Holomitrium close allies within the Dicranoideae will be reconstructed.

Back to TOP

Michelle Price, Feb 2001