Dennstaedtiaceae

Taxobox
name = Dennstaedtiaceae

Dennstaedtiaceae is one of fifteen families in the order Polypodiales, the most derived families within monilophytes (ferns). It includes the world's most abundant fern, "Pteridium aquilinum" (bracken). Members of the order generally have large, highly divided leaves and have either small, round intramarginal sori with cup-shaped indusia (e.g. "Dennstaedtia") or linear marginal sori with a false indusium formed from the reflexed leaf margin (e.g. "Pteridium"). The morphological diversity among members of the order has confused past taxonomy, but recent molecular studies have supported the monophyly of the order and the family [Smith, A. R., K. M. Pryer, et al. (2006). "A classification for extant ferns." Taxon 55(3): 705-731] . The reclassification of Dennstaedtiaceae and the rest of the monilophytes was published in 2006 [Smith, A. R., K. M. Pryer, et al. (2006). "A classification for extant ferns." Taxon 55(3): 705-731] , so most of the available literature is not updated.

Characteristics

* Terrestrial or scrambling over other vegetation—scandent
* Rhizomes long-creeping, occasionally short-creeping
* Rhizomes bear jointed hairs
* Rhizomes often siphonostelic or polystelic
* Petioles often with epipetiolar buds
* Petioles usually with gutter-shaped vascular strand (open end adaxial)
* Petiole pubescent of glabros
* Blades often large
* Blades often 2-3 pinnate, can be 1-4 pinnate or more divided
* Inducement of hairs, no scales
* Veins free, or forked, or pinnate, rarely vanishing
* Sori near the margin, or submarginal, sometimes fused with the blade to form a cup or pouch or obscured in a recurved portion of the blade margin
* Sori mostly linear, may be discrete
* Indusia linear or cup shaped at blade margin, or reflexed over sori
* Sporangium stalk with 1-3 rows of cells
* Spore tetrahedral and trilete, or reniform and monolete
* Gametophyte green, cordate Characteristics described by Smith et al., and Judd et al. [Judd, W. S., C. C. Campbell, et al. (2008). Plant Systematics: A Phylogenetic Approach. Sunderland, Ma, Sinauer Associates, Inc] [Smith, A. R., K. M. Pryer, et al. (2006). "A classification for extant ferns." Taxon 55(3): 705-731]

Distribution of Genera

Generally, the family is pantropical, but due to the distribution of "Pteridium" (the most wide spread fern genus), Dennstaedtiaceae can be found worldwide [Thomson, J. (2000). "Morphological and Genomic Diversity in the Genus Pteridium (Dennstaedtiaceae)." Annals of Botany 85(Suppl B): 77-99] . "Pteridium" is a well adapted early successional genus, generally described as a weed because of its ease of spread. The spore is light and robust, so it can travel relatively far and colonize open, disturbed environments easily [McGlone, M. S., J. M. Wilmshurst, et al. (2005). "An ecological and historical review of bracken(Pteridium esculentum) in New Zealand, and its cultural significance." New Zealand Journal of Ecology 29(2): 165-184] . "Dennsteadtia" is mostly tropical to warm-temperate, but not well represented in the Amazon or Africa. "Oenotrichia" is in New Caledonia. "Leptolepia" is in New Zealand, Queensland (Australia), and in New Guinea. "Microlepia" is in the Asiatic-Pacific. "Paesia" occurs in tropical America, Asia, and the western Pacific. "Hypolepis" is tropical and south-temperate. "Blotiella" is strongly centered in Africa. "Histiopteris" is generally Malesian, with one pantropic to south-temperate species. [Kramer, K. U. (1990). Dennstaedtiaceae. The Families and Genera of Vascular Plants: Pteridophytes and Gymnosperms. K. Kubitzki, K. U. Kramer and P. S. Green. New York, Springer-Verlag. 1: 81-94]

History of Classification

Dennstaedtiaceae was previously considered the only family the order Dennstaedtiales. Dennstaedtiaceae now contains the previously defined families Monachosoraceae Ching, Pteridiaceae Ching, and Hypolepidaceae Pic. Serm. [Smith, A. R., K. M. Pryer, et al. (2006). "A classification for extant ferns." Taxon 55(3): 705-731] . Before Smith's [Smith, A. R., K. M. Pryer, et al. (2006). "A classification for extant ferns." Taxon 55(3): 705-731] classification in 2006, Dennstaedtiaceae was a poly- and para- phyletic family [Wolf, P. G. (1997). "Evaluation of atpB Nucleotide Sequences for Phylogenetic Studies of Ferns and Other Pteridophytes." American Journal of Botany 84(10): 1429-1440] [Hasebe, M., P. G. Wolf, et al. (1995). "Fern Phylogeny Based on rbcL Nucleotide Sequences." American Fern Journal 85(4): 134-181] [Wolf, P. G. (1995). "Phylogenetic Analyses of rbcL and Nuclear Ribosomal RNA Gene Sequences in Dennstaedtiaceae." American Fern Journal 85(4): 306-327] , containing genera that now are classified within Lindsaeaceae and Saccolomataceae, and with the family Monachosoraceae arising from within the Dennstaedtiaceae clade [Smith, A. R., K. M. Pryer, et al. (2006). "A classification for extant ferns." Taxon 55(3): 705-731] . The nonmonophyletic nature of Dennstaedtiaceae (pre-2006 classification) was proved and supported by multiple molecular studies. Dennstaedtiaceae as now classified is supported as monophyletic, but the relation of the genera within the family have not yet been fully clarified [Wolf, P. G. (1995). "Phylogenetic Analyses of rbcL and Nuclear Ribosomal RNA Gene Sequences in Dennstaedtiaceae." American Fern Journal 85(4): 306-327] .

Interesting Species within Dennstaedtiaceae

Dennsteadtiaceae species and genera are usually known for their weedy nature (i.e. "Pteridium" spp., "Hypolepis" spp., "Paesia" spp.), but some species are grown ornamentally ("Blotiella" spp., "Dennstaedtia" spp., "Hypolepis" spp., "Microlepia" spp.) [Mabberley, D. J. (1997). The Plant-Book, Cambridge University.] . The fiddleheads/crosiers of "Pteridium aquilinum" have been known to be eaten, but they contain carcinogens, so this practice is not prevalent [Judd, W. S., C. C. Campbell, et al. (2008). Plant Systematics: A Phylogenetic Approach. Sunderland, Ma, Sinauer Associates, Inc.] .
The rhizomes of "Pteridium esculentum" were consumed by the Maori during their settlement of New Zealand in the 13th century, but no longer are a part of the Maori diet [McGlone, M. S., J. M. Wilmshurst, et al. (2005). "An ecological and historical review of bracken(Pteridium esculentum) in New Zealand, and its cultural significance." New Zealand Journal of Ecology 29(2): 165-184] . The rhizomes of "Pteridium esculentum" contain about 50% starch when they grow in loose rich soil, at relatively deep depths [McGlone, M. S., J. M. Wilmshurst, et al. (2005). "An ecological and historical review of bracken(Pteridium esculentum) in New Zealand, and its cultural significance." New Zealand Journal of Ecology 29(2): 165-184] . The rhizomes were a staple in the diet because once dried, the rhizomes were very light (perfect for traveling) and would keep for about a year as long as they remained dry [McGlone, M. S., J. M. Wilmshurst, et al. (2005). "An ecological and historical review of bracken(Pteridium esculentum) in New Zealand, and its cultural significance." New Zealand Journal of Ecology 29(2): 165-184] . The leaves and spores of the "Pteridium esculentum" are associated with toxins and carcinogens, and have been known to cause stock (cattle, sheep, horses, pigs) to sicken [McGlone, M. S., J. M. Wilmshurst, et al. (2005). "An ecological and historical review of bracken(Pteridium esculentum) in New Zealand, and its cultural significance." New Zealand Journal of Ecology 29(2): 165-184] .

References