A systematic study of the Diplazium lonchophyllum complex

A systematic study was undertaken on Diplazium lonchophyllum and other members of the New World tropical D. lonchophyllum complex. Morphological data analyzed by numerical methods and data from gametophytes, spores, stomates, cytology, and distribution were used in assessing taxonomic relationships.

Cluster analysis and principal coordinates analysis were performed on 150 specimens for 25 morphological characters. Results indicated that the specimens could be divided into eight groups which corresponded to species as eventually recognized. Factor analysis revealed that at least four characters which had not been used previously to delineate taxa in this complex were important in separating groups in principal coordinates analysis. Numerical analysis confirmed that the disjunct populations in Louisiana are D. lonchophyllum and do not deserve special recognition. This analysis also resulted in the splitting of D. cristatum into D. cristatum and D. arboreum.

Gametophytes of 12 plants of 1 species and 4 hybrids were studied to observe general growth and morphology. A female to hermaphroditic developmental pattern was common to all samples except one which was initially male. Gametophytes of three collections had distinctive shapes. Gametophytes of one collection exhibited a positive response to antheridiogen, and one exhibited a reverse response to antheridiogen, producing more females and fewer males and hermaphrodites. All samples displayed considerable intra- and inter-populational variability in size, morphology, and sexual development.

Limited results were obtained from studies of spore lengths, spore morphology using SEM, stomate patterns, frond flavonoid chemistry, and cytology. Diplazium werckleanum had distinctive spores and stomate patterns. No flavonoids were detected. Meiotic counts of n > 70 for D. lonchophyllum from Louisiana indicate it is probably a tetraploid.

This study has shown that members in the species pairs which previously were confusing can be easily distinguished using a combination of stable morphological characters. These pairs are D. lonchophyl1um/cristatum and D. lonchophyllum/subsilvaticum. However, further studies are suggested in the complex especially involving D. lonchophyllum/franconis, D. cristatum/arboreum, and D. tablazianum/subsilvaticum.