THE JEPSON GLOBE a Newsletter from the Friends of the Jepson Herbarium
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THE JEPSON GLOBE A Newsletter from the Friends of The Jepson Herbarium VOLUME 17 NUMBER 3 MARCH 2007 Director’s Column by Brent D. Mishler Bryophyte Biology The bryophytes, with more than 20,000 species worldwide, are the most diverse set of land plants aside from the flowering plants. The group includes three quite distinct lineages (i.e., moss- es, hornworts, and liverworts), some familiar species frequently encountered in mesic forests and along streams, as well as a number of less familiar species of tropical rain forests, arctic tundra, and desert boulders. The bryophytes have an ancient history; Dr. Paul Silva and Dr. Richard L. Moe they are remnant lineages surviving Announcing the Silva Center for Phycological Documentation today from the spectacular radiation of the land plants in the Devonian Pe- From its beginnings in the 19th tradition of Setchell and Papenfuss and riod, some 400-450 million years ago. Century, the University Herbarium has brought to UC a principal role in These three main bryophyte lineages (UC) has emphasized phycological phycological nomenclature. He as- (not monophyletic taken together), plus collections. William Setchell, who was sembled a comprehensive index of algal a fourth lineage (the tracheophytes, i.e., interested in marine algal taxonomy names (the Index Nominum Algarum) the so-called vascular plants), comprise and biogeography, communicated with and a corresponding index of phycolog- the monophyletic embryophytes phycologists worldwide and built up the ical literature (Bibliotheca Phycologica (land plants), arguably one of the most herbarium and library through ex- Universalis). He was a founding mem- important lineages to have arisen in change. Because of his early efforts, UC ber of several national and international earth’s history — they made possible is a repository of much early Europe- phycological societies and has served as an and Japanese phycological literature editor and reviewer throughout his ca- Continued on page 2. as well as type specimens. reer. He is an editor of the International Code of Botanical Nomenclature and ALSO IN THIS ISSUE G. F. Papenfuss, who succeed- is chairman of the Committee for the New Faces in the Herbaria ed Setchell, also promoted a global Nomenclature of Algae. The authors Volunteer Opportunities reach for UC phycology. He was an of numerous taxonomic, bibliographic, enthusiastic advocate of the interchange and nomenclatural compilations have Cal Day 2007 Schedule of phycological information, engaging acknowledged their debt to Silva. Announcements in prolific correspondence and attending Upon his retirement, Silva Weekend Workshops international meetings. established an endowment fund for the Reception and Auction Photos Paul Silva has continued the Continued on page 3. Director’s Column, continued from page 1. to some extent, probably as a retention of traits of early land plants, while these traits were lost in the evolution of larger, more complex, and endohydric tracheophytes. (4) Need for free water for sexual reproduction. Another residual feature of the early land plants shared by mod- ern bryophytes is the constraint imposed by the swimming sperm. Swimming gametes have short dispersal distances, which leads to frequent inbreeding in monoicous species (those with male and female gametangia on the same plant) Polytrichum in full glory (Eric Harris) form below, in hopes of summarizing and lack of sporophyte production in dioicous species (those with male and the colonization of land by animals, how different major lineages have female gametangia on different plants). and evolved an unparalleled diversity of solved the problem of life on land, in (5) The clump as a “super- or- size, structure, chemistry, and function. a way useful for thinking about these ganism.” Many mosses and some Yet, despite their diversity, phyloge- remarkable little plants. liverworts are essentially social or- netic importance, and key roles in the Major differences in bryophyte ganisms like bees or ants. This results ecosystems of the world, study of many biology from tracheophytes include: from the combination of clonal growth, aspects of the biology of bryophytes has (1) Haploid dominance in the poikilohydry, and external water lagged behind that of the larger land alternation of generations. Unlike conduction. The plants in a clump are plants, perhaps because of their small the situation in tracheophytes, the subject to natural selection as a group. size and the few scientists specializing green, vegetative part of the life-cycle Intimate contact of each vegetative cell on them. This is unfortunate because of in bryophytes is haploid. Without with the environment, due to poikilohy- the intrinsic scientific interest of these the genetic benefits of dominance, dry, lends itself to interplant chemical plants. I would like to summarize here genes acting in the gametophyte are communication via pheromones, and a little of what we do know about their presumably subject to relatively severe extreme sensitivity to chemicals in the biology, as an encouragement for you to selection. This affects reproductive bi- environment, including pollutants. get to know them better. ology as well, e.g., selfing in a bryo- (6) Heavy reliance on asexual One might assume, to start with, that phyte has very different implications reproduction. Due to the difficulty of bryophytes are biologically like their (complete homozygosity) than selfing achieving fertilization, many bryo- larger cousins, just smaller versions. in a diploid. phytes have evolutionarily lost func- But, is this a reasonable assumption? (2) Extensive phenotypic plas- tional sexuality. Many kinds of asexual In what ways does bryophyte biology ticity. Studies have shown that bryo- propagules have evolved, and most differ from that of the larger tracheoph- phytes tend to have very high amounts vegetative cells of the plant can prolif- ytes? The short answer: in almost every of morphological and physiological erate. Because bryophytes grow from way possible! The groups didn’t evolve plasticity. This may compensate for the an apical cell, somatic mutation allows on different planets, but their differences demonstrated low levels of ecotypic genetic variation even within clones. could almost make you think they did. differentiation in bryophyte species, (7) Small stature and the occupa- They certainly adopted very different even between widely different lati- tion of microhabitats. Small size, lack approaches to being a land plant on this tudes. of roots, and poikilohydry means that planet. Many aspects need much more (3) Poikilohydry and desicca- bryophytes are in a close relationship study, but what is known about bryo- tion-tolerance. Poikilohydry is the with only their immediate microenvi- phyte biology suggests that in general rapid equilibration of the plant’s water ronment. Over geological time, they are the bryophytes differ in most ways in content to that of the surrounding en- less influenced by climatic change their genetics, physiology, ecology, vironment, while desiccation toler- than larger organisms, and linger in and evolution from tracheophytes. I ance is the ability of a plant to recover refugial habitats. will go through these contrasts in list after being air-dry at the cellular lev- el. All bryophytes have these abilities (8) Less selection pressure from the 2 Director’s Column, continued from page 2. Silva Center, continued from page 1. Second Edition of The Jepson biotic component of the environment University Herbarium to ensure that Manual than from the physical component. UC’s role in the phycological world Treatments for public viewing avail- Vagility and establishment abilities will be perpetuated. The endowment able at: of bryophytes are relatively poor. brings into being the Silva Center for http://ucjeps.berkeley.edu/jepson- Available substrates are not filled in Phycological Documentation, which manual/review/ has the goals of continuing to track the most mesic and xeric environments Please forward any comments you publication of algal names and taxo- (although they may be in some hydric may have about these treatments to the nomic information, and to make that environments). The presence of oth- Scientific Editor, Dr. Thomas Rosatti er bryophytes nearby often appears information conveniently available. beneficial to growth through enhanced Silva’s indexes can now be reached via ADOXACEAE: SAMBUCUS, the Internet (see http://ucjeps.berkeley. VIBURNUM water-holding capacity, rather than a ARACEAE: LANDOLTIA, LEMNA, source of competition. edu/INA.html). SPIRODELA, WOLFFIA, WOLFFIELLA (9) Relatively slow evolutionary BETULACEAE: ALNUS, BETULA, rates in morphology. The fossil record The first Silva Curator of Phy- CORYLUS of bryophytes indicates that ancient cological Documentation will be Dr. BURSERACEAE: BURSERA CALY- Richard Moe, who has a strong back- CANTHACEAE: CALYCANTHUS forms are very similar to modern ones. CISTACEAE: CISTUS, HELIANTHE- Biogeographically, bryophytes tend to ground in marine phycology and has MUM, TUBERARIA follow the same historical patterns of developed broad interests in electronic CONVOLVULACEAE: IPOMOEA disjunction as tracheophytes, but at a publication, databases, and Internet DIPSACACEAE: DIPSACUS, SCABIO- technology. SA lower taxonomic level. This may in- FOUQUIERIACEAE: FOUQUIERIA dicate that developmental constraints GERANIACEAE: GERANIUM play an unusually important evolu- GUNNERACEAE: GUNNERA tionary role. JOIN US! LENTIBULARIACEAE: PINGUICU- LA, UTRICULARIA