MEHLTRETER, KLAUS1* AND MóNICA2 PALACIOS-RIOS. Instituto de Ecología, A.C., 1Departamento Ecología Vegetal, 2Departamento Sistemática Vegetal, Apartado Postal 63, Xalapa 91000, Veracruz, México. - Phenological studies on Acrostichum danaeifolium Langsd. et Fisch. (Pteridaceae, Pteridophyta) on a Caribbean mangrove site of Mexico.
Why does only a few studies on fern phenology exist? Perhaps this is
the consequence of 3 prejudices: 1. Slow growth, 2. No growth or
fertility rhythms as it is believed that ferns grow only under
continually favorable humid conditions, and 3. Independence of
pollinators for fertilization and animal vectors for their dispersal.
Results of these study clearly prove that all 3 prejudices are not
true for the mangrove fern Acrostichum danaeifolium. A
population of 30 individuals was observed along a transect during one
year in La Mancha (19°36’00’’N, 96°22’40’’W), Veracruz, Mexico. The
climate is hot and humid with a dry season from November to March.
Mean annual temperatures fluctuate between 22-26°C and annual
precipitation varies between 1200-1500 mm. The study site is some 300
m from a brackish water lagoon, in the understory of the mangroves,
dominated by Avicennia germinans (Avicenniaceae), where
Acrostichum danaeifolium forms populations of 28.000
individuals per hectare. Phenological measurements were done biweekly.
Individual daily leaf growth can reach up to 6-8 cm during the rainy
season and slows down to 4 cm during the dry season, while the number
of new buds and leaves shows little variation. Plants have a mean
number of 8-10 sterile leaves, develop 1-2 leaves per month and the
age of sterile leaves is around 9 to 12 months. The population was
composed of 35 % of mature plants, which produce 1-3 fertile leaves
only during the rainy season. Fertile leaves are alive for 2-3 months,
so that there are no fertile plants during the dry season. Living
gametophytes were present during the whole year, but especially
abundant during the end of the dry season.
Key words: Acrostichum danaeifolium, ferns, mangrove, Mexico, phenology, Pteridaceae