Mushrooms and Other Fungi

The George Washington Memorial Parkway is home to lush forests, teeming wetlands, and verdant meadows. However, none of these spectacular ecosystems would function without the vital roles filled by the fungal community. This enigmatic group of organisms not only possess an incredible level of diversity in both form and function, but also plays a key role in maintaining the health and diversity of plant and animal communities.

Although they may superficially resemble plants, fungi occupy a separate taxonomic kingdom, "fungi." During their long, but ongoing, evolution; the ancestors of fungi diverged from the ancestors of plants sometime around one billion years before present, and from animals only slightly more recently. In addition to true fungi, there are also fungus like organisms that (through convergent evolution) have evolved a lifestyle similar to that of fungi; such as slime moulds, and a group of organisms represented by the microorganism that causes potato blight disease in potato crops.

A billion years of evolution has produced many unique features that characterize fungi. Two of their most important features pertain to the way in which fungi grow, and the composition of their chromosomes. Firstly, fungi exhibit two distinct forms of growth. They can grow as hyphae, which are a series of branching root-like filaments that expand by dividing behind the leading tip of individual hypha. The mass formed by these branching hyphae is termed the mycelium. Fungi can also grow as free living yeasts, which grow by fission of individual cells. A few fungi, called "Dikaryotic Fungi" are even capable of switching between these two types of growth. Secondly, the cells of fungi contain haploid nuclei. Unlike the cells of plants and animals (excluding special reproductive cells), fungal cells only contain half the organism's chromosomes at any given time. Despite these unique characteristics; fungi, much like animals, are incapable of producing their own food, and must obtain their food by absorbing it from their environment. Whether it's from the soil, or from the dead or living tissues of plants, animals, or even other fungi, the search for energy continues to drive the evolution of fungi within our ecosystems.


What Lives Here

Since they first appeared a billion years ago, fungi have undergone an impressive degree of speciation. The legacy of their evolution can be found in the five living phyla within the kingdom fungi, all of which are represented within the ecosystems of the George Washington Memorial Parkway.

Chytrids live in close association with water, and can be found in almost any body of water within our parks, as well as in damp soil. Chytrids are unique among fungi due to the fact that their zoospores (single-celled seeds or larvae) are free swimming and are capable of "searching" for an appropriate location to encyst and grow. In this park chytrids are inconspicuous decomposers of dead organic matter, or as parasites of plants and freshwater invertebrates. The chytrids familiar to most people are the ones that cause the black crusts that occasionally show up on grocery store potatoes, and the invasive chytrid that has been implicated in the devastating worldwide loss of amphibians.

These fungi are closely associated as symbiotes of plants, and can be found growing between and into the root cells of herbaceous plants. Like the chytrids, they are highly inconspicuous, but play an important role in maintaining the health of park ecosystems.

The Zygomycota are a group of fungi typically associated with unpleasant images of animal feces and rotting fruit. Some species of Zygomycota are able to grow at unusually high temperatures (about 600C) associated with compost piles. Many Zygomycota are important parasites of insects, and are capable of causing spectacular crashes in their host populations.

Basidiomycota are probably the phylum of fungi familiar to most people when they picture a fungus, since they produce the familiar mushrooms. Many species in the Basidiomycota are symbiotes with large forest trees, making them important to the overall health of forest ecosystems. Many others are decomposers growing in the soil or on decaying logs. A few are virulent pathogenic parasites that cause many plant diseases.

The Ascomycota are the most diverse and speciose phylum of fungi found in this park, occupying an enormous variety of niches within our ecosystems. They fill everything from decomposers of organic material, to parasites or symbiotes of plants and insects. They can even be found growing harmlessly as yeasts within the respiratory tracts of humans and other animals. Lichens, which are ubiquitous on exposed rock, usually contain an Ascomycete fungus as partner in the relationship.


Finding Fungi

A bioblitz sponsored by the George Washington Memorial Parkway in 2006 turned up 55 different species of mushrooms; representing a tiny fraction of the possible number of species present in the park. The best times to find and observe fungi are between late spring and mid fall, preferably after a recent rainstorm. If you're looking to identify individual species, it helps to also identify what they are growing on or near.

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