Bryophytes of Nevada On-line
Bryophytes: the Miniature Forests Overlooked Across Nevada

The bryophytes (mosses, liverworts, and hornworts) are a remarkable group of diminutive land plants that have traditionally been overlooked by plant enthusiasts, academic botanists and resource land managers. These plants are actually all around us, and like lichens; they contribute greatly to ecosystem function. Of the mosses, liverworts, and hornworts, the mosses are the largest group with nearly 15,000 species worldwide. In Nevada we lack a current inventory of bryophytes. The most recent treatment was published back in 1958 and this only addressed the mosses. I believe Nevada may have over 350 species of mosses, but unfortunately there are few mosses from Nevada in herbaria available for study. Mosses, liverworts, and hornworts are placed in the Bryophyta and they represent three distinct evolutionary lineages, the most primitive remnants of the Devonian land plant radiation. Most bryologists (botanists who study bryophytes) specialize either in the study of mosses or the study of liverworts and hornworts since they are actually quite different. The primary reason why few people are familiar with bryophytes is based on the perception that identification of mosses, liverworts, and hornworts is difficult due to their small morphological size and lack of showy features such as flowers or that few easy to use identification guides are available. While this is partly true, the same perceptions of "taxonomic difficulties" have rendered the flowering grasses, sedges and rushes less known at the species level with amateur botanists too. With all of these groups, removing the perception of taxonomic difficulty is simply a matter of learning their novel structural features and associated terminology.

What are the main characters that bryophytes have in common? Collectively, bryophytes lack true roots, stems, and leaves. They have motile sperm that require free water for fertilization, and most importantly, have a dominant gametophyte (haploid phase) generation where the sporophyte (diploid phase) generation is short-lived and attached to the gametophyte. This is just the reverse pattern of the vascular plants where the sporophyte is the dominant generation and the gametophyte is short-lived and inconspicuous. In bryophytes, sexual reproduction occurs on the gametophyte with the result of such reproduction being a sporophyte that produces spores. More important in the life of most bryophytes is asexual reproduction.

Mosses, liverworts, and hornworts can be separated in the field fairly easy. When sporophytes are present on mosses they have a rather rigid stalk (called a seta) that holds the capsule containing spores. The capsule can have a wide variety of shapes and ornamentations. Lining the mouth of the moss capsule are usually minute teeth-like structures collectively called the "peristome". These teeth may assist in spore dissemination. The development of the peristome and the number of teeth present are important features in the circumscription of moss families. Teeth can be either 4, 8,16, 32, or 64 in number. Liverworts on the other hand have short-lived sporophytes. The stalk is not rigid as in mosses, and the spore-producing capsule is also short-lived, usually spherical or oblong in shape and generally dark in color. Liverwort capsules open by longitudinal lines, and thus have no peristome. Hornwort sporophytes have no distinction of a capsule. Rather the entire sporophyte is a columnar structure that grows from its base and loses its spores continuously from the apex. When observing bryophytes in only a vegetative condition, moss "leaves" generally have a midrib called a "costa". This costa may only occur at the base of the leaf, run the entire length or extend beyond the leaf forming a point or awn. The costa is generally observed with a hand lens. The costa is a very important diagnostic feature in keying out mosses. Liverworts can be both thalloid and leafy types. For the leafy liverworts, the leaves always lack a costa and are generally in three ranks, two lateral rows and one ventral row of leaves which is generally considerably smaller, giving the plants a distinctive dorso-ventral symmetry. Liverwort leaves are usually lobed or dissected, a feature lacking in mosses. Liverworts also have spherical "oil bodies" in the leaf cells, which are lacking in mosses. Thallose liverworts and hornworts lack leaves so they do not resemble mosses. Thallose liverworts can be hard to tell in the field from hornworts, but the latter tend to be a greasy blue-green in color due to the symbiotic blue-green algal colonies consistently present within the thallus. The rest of this article will focus on the mosses.

Mosses are divided into three broad groups. The first group of mosses, called the "peat mosses", belong to the genus Sphagnum. There are about 150 species of Sphagnum worldwide with one species is currently documented for Nevada. As the name suggests, peat mosses are generally found in bogs, meadows and wet places such as lake margins. Peat mosses can hold at least 20 times their dry weight in water. In Nevada, Sphagnum must be viewed as relictual, a hold-over from a different climatic time. The second group of mosses, called the "granite mosses", comprise nearly 100 species worldwide. Currently, no granite mosses have been found in Nevada, but this is more likely a function of limited collecting rather than a lack of suitable habitat. Andreaea is the larger of the two genera of granite mosses. These mosses are attached to boulders and rock outcrops and can be easily overlooked because they are generally only a half-inch or less in height. Granite mosses are rather blackish to bronze in color. The capsule of Andreaea is very distinctive, opening by four longitudinal slits. The third group of mosses, called the "true mosses", comprise the overwhelming majority of moss species worldwide. All true mosses have a peristome or are evolutionarily derived from peristome plants. Most mosses encountered in the field will be of this group which is comprised of numerous genera and moss families. The largest moss genus is Bryum with over 1000 described species. Bryum will probably be the largest genus in the moss flora of Nevada too. While sporophytes are useful in identification, they are seldom required. Some mosses produce sporophytes frequently, while other species are rarely seen in this condition. Some of the terminology used in mosses is the same for flowering plants, but the meaning is different. For example, when bryologists say a moss is in good "fruiting condition", they are referring to a moss with abundant sporophytes!

Since mosses lack roots and efficient internal water transport tissues, they have to be able to absorb water directly through cell membranes. Because of this, mosses can be highly susceptible to various pollutants in the environment. Mosses also need to be able to withstand various periods of desiccation. Some mosses have evolved to withstand these dry periods better than others do. Mosses, especially in arid environments like deserts, can go dormant for long periods of time. Once moisture returns, these desiccated mosses rapidly come back to life, uncurl their leaves, green up and begin photosynthesis. This resurrection can actually happen in minutes! Mosses can also grow in very cold temperatures, even when the outside temperatures are near freezing. Thus, despite their delicate structure, many mosses are capable of growing in rather harsh environments.

Mosses occur on a wide variety of substrates from exposed soil, rocks, trunks of trees, to completely aquatic. Each particular moss species occupies a very specific microhabitat. Some species only occur on granite rock, while other species are restricted to marbles and limestones. Specific microhabitats for mosses can range from species only found on various stages of decaying logs while another specialized group of mosses are restricted to animal dung or carcasses. Thus in the study of mosses, knowing the substrates can be a big aid in using keys. A few of the ephemeral (short-lived) species are best seen in late winter or early spring when the rains return to Nevada. Only a few mosses can grow on soils with heavy metals, such as the "copper mosses" in the genus Mielichhoferia. However, the greatest concentration of species will be in more mesic habitats such as stream sides in hardwood and/or conifer forests. Mosses display different rates of colonization on tree trunks due to the development of the bark of the tree and the relationship to its water holding capacity. Bark that exfoliates frequently is usually a poor substrate for mosses. Mosses seem to prefer hardwoods to conifers in most cases when both types of trees are present. In these kinds of forests, mosses play a key function in water regulation. Mosses also provide homes for countless invertebrates.

Many mosses are actually quite large and showy, and with further observation under a hand lens or a dissecting scope will provide a whole new world of botanical beauty, fascination and enjoyment. Mosses are like miniature dense forests upon closer examination. Although only a few inches tall, Climacium dendroides looks like a palm and Dendroalsia abietina resembles a conifer in miniature. It just takes a while to focus at this scale while walking in the woods! Aquatic mosses are spectacular too. The "water mosses" in the genus Fontinalis can reach lengths of up to 2-3 feet! Look for Fontinalis in clear unpolluted streams and creeks. One of the greatest features about mosses is that they can be observed just about at any time of the year. Just stop at a tree or rock covered with mosses, look closely, and you will be surprised just how many different kinds you can separate and recognize by their general appearance, color, texture, size, and shape. Nearly everyone can learn the 25 most common species in their area of the state with a little bit of study. In fact, many moss genera can be recognized relatively quickly with some field training. However, if one wants to learn all of the mosses for a particular region (a county, watershed, or mountain range), then a compound scope will be absolutely necessary. Most of the best diagnostic features for separating one species of moss from another reside in an examination of cellular structures of the leaf. To see these differences, a higher magnification will be required than is possible with just a hand-lens or dissecting scope. Cells in the leaves can have a wide variety of shapes and sizes. The range can be from spherical, diamond-like to long and wavy. Besides the shape and size of the cells (and cells are generally different shaped along the margin, tip or base of the same leaf), cells can also have different ornamentations. Some of these ornamentations look like small wart-like bumps on the cell wall called "papillae". Besides the shape of the cells and their position in the leaf, a cross-section of the leaf highlighting the costa provides additional information on cell arrangement and is very useful in the identification process. So, just like the vascular plants, there are a few large moss genera and some taxonomically challenging groups. In identifying mosses in Nevada, once you have accurately determined the genus, you usually have only a few species to separate in the key to make a final determination of the specimen.

Nevada bryology is still a great field of study for amateurs and professionals alike. Currently there is no "bryoflora" for the Silver State but a new catalogue of Nevada mosses is in the planning stages by this author and Dr. Lloyd Stark at UNLV. Just 30 years ago, there were only around 160 mosses recorded for Nevada. It is my prediction that there are at least 200 mosses in Nevada just waiting for some botanist to document their presence in the state. Yes, additional mosses are yet to be located in Nevada and from time to time, a new moss species will need to be described and published as new to science. The distribution and range of moss species in the state is also a fascinating subject. Some mosses have only been collected a few times in Nevada or currently known from only a single occurrence while other species are common and widespread. What factors affect the distribution of mosses in the state? When one considers the extremely small size of a moss spore and the potential for long distance dispersal by wind, one might conclude that moss distributions would be more uniform across a climatic gradient. Actually, this appears not be the case. It must indeed be a rare event for a spore to not only get to a particular locality, but land in a habitat and substrate that is suitable for germination and eventual establishment. Spores are also generally short-lived, so these factors must make the establishment phase highly problematic. If germination of the spore actually occurs, that species may not be able to survive long enough or tolerate the level of desiccation received for that particular locality. Some moss populations or colonies may actually be relictual as a result of climate change, restricted now in Nevada to small geographical regions or habitats, which contain a suite of microsite features for its survival. Many mosses occurring in North America have wide distribution ranges but occur as isolated disjunct populations. In this way, many mosses are "rare or uncommon in Nevada but more common elsewhere". However, we do have a few endemic mosses in Nevada. Some of these species are rare and localized such as Didymodon nevadensis restricted to gypsum soils in Clark County. Sometimes, areas with great species diversity in flowering plants also harbor a rich moss flora. As a general rule, the regions of Nevada with a wide diversity of climatic and rainfall patterns, habitats, elevation, geology, and plant communities should also have a diverse moss flora. Because rainfall availability and desiccation stresses are linked, the moss flora of Nevada is likely to be more species rich in the mountains than in the drier regions within the Mojave Desert. However, we lack a good representation of moss collections throughout Nevada to determine where the species rich areas for mosses occur or a good understanding of moss rarity in Nevada.

Collecting mosses for study and identification is very simple. No plant press in necessary, in fact, it is best not to press mosses flat like we do with vascular plants. Why? Because as mosses loose water from the single layer of cells that forms the leaves, many species have distinctive appearances and shapes as they dry. Leaves as they desiccate can have a particular curling, arching, or twisting shape which are very useful as diagnostic features in moss keys. If pressed too flat, some of these distinctive features can be altered giving the moss an unnatural appearance when dried. To collect a moss sample, simply place a small piece of moss (no more than the amount to cover a 3"x 5" card) and place in an envelope or small paper bag to air dry. Most mosses can be dried in a few days. Key is to have them in a place where air can circulate over the specimens. A simple collection packet can be folded from a piece of 8 1/2" x 11" piece of paper. Plastic bags, while very useful for collecting vascular plants, should be avoided since mosses instead of drying can grow abnormally and also mold. Regardless if one uses paper packets or small paper bags, important ecological information must be obtained while in the field. Such attributes include such information as substrate (on soil, kind of rock, type of tree), habitat (plant association), and moisture (dry, moist, wet). These data are either noted on the collection packet/bag or by placing all of the key information and location data in a field notebook. This information will be essential when keying out the specimen and in preparing labels. The most important thing is good and accurate record keeping that adds to the scientific value of any collected specimen. Once dried, mosses are nearly indestructible. When you are ready to study a dried specimen under the microscope, just remove a very small sample of the moss with forceps and dip it in warm to hot water for a couple of seconds and it will plump up and look as good as new! Mosses are not glued on herbarium sheets like vascular plants either. They are simply placed in small packets of good quality cotton paper with a label glued on the front packet flap. They are generally stored like filing cards in a shoebox and filed alphabetically by the scientific name. The labels look just like those prepared for vascular plants and contain all of the key attributes (date, detailed location, latitude/longitude, substrate, habitat, collector, collector number etc.). Maintaining a personal moss herbarium is quite easy. Duplicate specimens, where available, should be sent to a major institution so other researchers can study them too. The nearest herbaria to the state of Nevada that have large bryophyte collections include the California Academy of Sciences in San Francisco and U.C. Berkeley to the west and the Missouri Botanic Garden in St. Louis to the east. The largest bryophyte collection in the USA resides at the New York Botanic Garden. Perhaps a NNPS member will locate a moss species heretofore unknown for Nevada in the pursuit of learning some of the mosses in his/her area. The distribution and range of many bryophytes in Nevada is poorly known due to the large gaps in areas where bryophyte collecting has actually occurred. Our knowledge of species distributions for the Nevada bryoflora is about where the vascular flora was nearly 100 years ago! Yes, you could really make a great contribution to Nevada bryology by making moss collections for scientific study.

There are a few popular and less technical moss identification books or manuals available to get started in this new adventure of botanical study. One illustrated popular guide recommended although not developed specifically for Nevada is Mosses, lichens and ferns of Northwest North America by Dale Vitt et al. It is a good photographic field guide. This book has color photos for many mosses that occur in Nevada. However, this field guide will not allow you to identify all of the mosses you may encounter in Nevada. Moss floras on the other hand attempt to address all of the taxa for a particular region and these floras generally have more detailed and accurate illustrations, especially cellular structures of the leaves, which are useful when comparing features among closely related taxa. A really good illustrated glossary of bryological terms has recently been published titled Mosses and other bryophytes: an illustrated glossary by Bill and Nancy Malcolm published in 2000. The moss floras currently available and applicable for most of Nevada are Moss Flora of the Pacific Northwest by Elva Lawton published in1971 and Mosses: Utah and the West by Seville Flowers published in 1973. Both are well illustrated. The Lawton moss flora will work very well for the higher elevations in Nevada whereas the Flowers moss flora is probably best for the entire state, especially the arid regions.

There is also a great need for moss photographs of publication quality that can be used in developing an illustrated guide to the mosses of Nevada. I challenge all of the professional and amateur photographers in Nevada to canvass the slopes in search of mosses to photograph. Because of their small size, plane of view, and diffuse lighting especially in forested environments, it will take some different techniques to capture the beauty of mosses on film. A very small sample of the photographed moss should also be collected so that an accurate identification of the photos can be made. Contact the author regarding the identification of your best photographs for possible inclusion toward a photographic field guide of Nevada mosses.

If you really would like to learn more about bryophytes and obtain a first-hand experience in identifying them, then I suggest one consider taking a bryophyte class such as those offered as part of the "Weekend Workshop Series" by the Jepson Herbarium, U. C. Berkeley. This is a great way to add bryophytes to your knowledge base. Another option is attending a field trip where an introduction to bryophytes will be the featured attraction. So the next time you are hiking, take a few moments to stop and look at these other forests. You will be surprised at just how much of Nevada’s botanical beauty you have been missing!

Jim Shevock is a research associate in the Department of Botany, California Academy of Sciences in San Francisco. His interest in Nevada mosses began while conducting the field work for a bryoflora of Death Valley National Park of which portions of the park occur in Esmeralda and Nye counties. He also works for the National Park Service, Pacific West Region, Oakland CA. Jim can be contacted by email at jim_shevock [at] nps [dot] gov

This page is part of the
Bryophytes of Nevada On-line
web site, with content contributed by
Dr. Lloyd Stark
Plant Ecologist, Bryologist and Assistant Professor
University of Nevada at Las Vegas
and
James R. Shevock
University of California, Berkeley, and
California Academy of Sciences, San Francisco
and hosted by the
Nevada Natural Heritage Program
on the
State of Nevada web server