Dienstag, 15. Januar 2013

The Genus "Cladonia"

Mosses aren't the only organisms, which can best be examined during the winter, when most of the higher plants are in hibernation. Lichens can also be viewed at this time particularly well and so I want to write about a lichen this time. Specifically, it isn't one species but three from the Genus Cladonia. These three species are Cladonia furcata (Huds.) Schrat.; Cladonia foliacea (Huds.) Wild. and last but not least Cladonia fimbriata (L.) Fr.

As is said it before, all of these species belong to the Genus Cladonia, which belongs to the Cladoniaceae family. The Cladoniaceae are part of the order Lecanorales. There are approximately 350 different species within the Genus Cladonia. The habitus of these species can vary greatly, because they are rich in shape.

1) Cladonia furcata (Huds.) Schrat.

The first lichen, I want to show you is Cladonia furcata. In German, this species is known as “Gabel-Flecht” (Fork-Lichen) or “Gabel-Säulenflechte”. Unfortunately, I haven't found a common English name.

C. furcata - habitus

This species have to different Thalli (“bodies”): a primary Thallus and a secondary Thallus. The primary Thallus of this lichen is flattened and have a leaf-like shape with a lobbed margin. It's about 4 millimeters long and 3 millimeters wide and lies directly on the substrate

C. furcata - habitus

On this primary Thallus, the secondary Thallus grows. In Botany, the secondary Thallus is called Podetia (Sing.: Podetium) and is typical for many lichens of the Genus Cladonia. It has the shape of small, upright growing branches. In the case of C. furcata, the podetia are richly branched, what gives them an fork-like habitus. This is also the reason for the name of the species. All in all, the Lichen have a foliose or spongy habitus, which reminds a little bit to a small coral.

C. furcata - Podetia

In both cases, the Thalli can vary greatly in color, what also depends a little bit on the substrate on which the lichen grows. The color may range from a deep, dark green to a silver-gray or brown.

Like the most Lichens, C. furcata also has cup-like Apothecia (Sing. Apothecium) for reproduction. These are the fruit bodies of the lichen, where the Asci (Sing. Ascus), the tubular spore-bearing cells are located. With C. furcata, the Apothecia are at the end of the branches (podetia). They have a dark-brown color.

C. furcata - grows often between mosses

C. furcata is distributed worldwide and can be found on every continent (except Antarctica). It grows on different substrates and can be found mostly between mosses but also on the pure soil. In some cases, it also grows on rotten wood.

It should also be noted that some ingredients of C. furcata may be able to kill cancer cells. Especially at leukemia cells, this effect was observed. Because of this, the species has some value for cancer researchers.

2) Cladonia foliacea (Huds.) Wild./ Cladonia convoluta (Lam.) Anders.

The second Lichen is Cladonia foliacea (Huds.) Wild. In German, this plant is known as “Blättrige Cladonie”. Again, I didn't found an English name but the Latin name means something like “folios Cladonia”.

C. fasciola - beneath a bush

Please note: The Taxon Cladonia foliaceae is very similar to another Taxon named Cladonia convoluta (Lam.) Anders. The boundaries between these to Taxa are blurred and together, they form a single, taxonomical complex. For simplicity, I will remain with the name “Cladonia foliaceae” but keep this fact in mind.

C. furcata - a dense tufe on a slope

The Thallus of this lichen grows flattened on the soil and reaches heights between 1 and 3 centimeters. However, it's not uncommon, when several lichens overlap and form a dense turf. The Thallus is deeply lobbed and divided into several, leaf-like structures. Their dorsal site have an olive-green color, while the ventral side is yellowish or white. In many cases, however, the “leaves” are folded and so, the ventral side points up.

C. furcata - Thallus. Yoe can see the bright, ventral site

In contrast to other lichens from the Genus Cladonia, C. foliacea have only short and inconspicuous Podetia and even Apothecia are rare to find, because the species propagates vegetative primary.

C. fasciola - Closer look

The complex of C. convoluta / C. foliacea is native to Europe but some sub-species can also be found in the United States, Siberia, the Middle East and even Australia (almost all C. foliacea). The main areal of C. foliacea is Scandinavia, while the main areal of C. convoluta is Spain. In between, the transition between these two species is blurred.

The species grows in a temperate climate and likes bight places. So, it can be found on rocky slopes, clearings and dry meadows. It prefers a nutrient-poor soil.

3) Cladonia fimbriata (L.) Fr.

The last lichen, which I want to show you, is C. fimbriata. The German name of this species is “Trompetenflechte”, what means “Trumpet lichen” in English. The Latin suffix “fimbriata” means “fringed”.

C. fimbriata - habitus

As with the Thallus of C. furcata, the Thallus of C. fimbriata is subdivided into a primary and a secondary thallus. The primary Thallus is between 6 and 4 millimeters long and consists of small, leaf-like lobes, which lie flat on the substrate.

C. fimbriata - habitus(here you can see the trumpet-shaped

The primary Thallus is very inconspicuous in contrast of the Podetia of the secondary Thallus. These are between 2 and 3 centimeters long and are about 1 millimeter in diameter. They have cup-like tips (4 millimeters in diameter), which give the podetia the look of a trumpet. This is, of course, also the reason for the name “trumpet lichen”.

C. fimbriata - in a wood. Note the long Podetia
(Photo taken by Christopher Schwerdt)

Both Thalli have a gray-green to slight green color and a rough, surface, which is broken in many places. In Lichenology, these cracks are called Sorals (Sing.: Soral) and serve the vegetative propagation. Through them, a lichen can give off small packages (so called Soredia) of hyphae and algae and multiply so without fertilization.

C. fimbriata - primary thallus

The small Apothecia are located within the cups and have a brown color. However, they are very uncommon. because the lichen reproduce mostly through the Soredia.

C. fimbriata can be found in the temperate regions of the northern and southern Hemisphere. It grows on shady places and sandy soils. Some grew places are woods, tree trunks, mosses and also rocks. The species is very common in Europe and easily recognized by its trumpet-shaped podetia.

4) Epiologue

So, I hope, that I was able to give you a basic overview about the Genus Cladonia and three of its species. In the next weeks, I will also take a closer look at the biology of lichens, what is also very interesting. This weekend, I will participate in a field trip about lichens and mosses at the Ruhr-University of Bochum; organized by the “Botanischer Verein Bochum” . Maybe I will able to show you some new species after that.

Please note: The third  picture of Cladonia fimbriata were taken by Christopher Schwerdt. I have his permission to use these pictures in my blog. Please also visit his homepage www.schwerdtfisch.net

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