is their lack of ambiguity: Nereocystis luetkeana applies to only one species, allowing confident communication about this species by scientists and professionals no matter where they are in the world—this is the power and beauty of scientific names.
The two parts to the name are informative. The first part is the “generic” or “genus” name and is applied to multiple species when they are closely related—e.g., the lion (Panthera leo) and tiger (Panthera tigris).The second part (e.g., leo) is the “specific” or “species” name and tells you that you’re talking about a lion and not a tiger. Both a genus and a species are required in a scientific name. These names are usually derived from Latin or Greek—which can make them tongue-twisters—and may or may not describe some feature of the species: e.g., the name of the five-rib kelp, Costaria, comes from the Latin costa (a rib), but the sea palm kelp, Postelsia, is named for the Estonian naturalist Postels.
The majority of our seaweeds do not have widely accepted common names. In this guide we include only those common names that we consider to be well established. Our advice is to use the scientific name and attach a descriptive phrase if you find this helpful; for example: Costaria costata, the five-ribbed kelp.
Species of seaweed are classified in a taxonomic hierarchy that reflects their relatedness. This hierarchy is universally applied to all living things and
25
About Seaweeds
some that are not (fossils). For example, Saccharina latissima (sugar kelp), a brown seaweed, is classified as follows:
Kingdom: Chromista. A kingdom is a large grouping of vaguely similar species thought to share a distant common ancestor. Other kingdoms include Animalia and Plantae.
Division: Phaeophyta (brown algae). A division is a slightly smaller group of species thought to share a common ancestor. The animal equivalent to division is phylum. The -phyta suffix designates divisional status. Other divisions include Chlorophyta (green algae) and Rhodophyta (red algae).
Class: Phaeophyceae. Classes designate groups within a division that have significant differences but are closely related. For example, birds and mammals form separate classes within the phylum Chordata (animals with backbones). The -phyceae suffix designates class. Other classes include Chlorophyceae (most green algae) and Bacillariophyceae (the diatoms).
Order: Laminariales. A class is subdivided into orders on the basis of features such as body plan and life cycle. In the brown seaweeds, the order Laminariales (large brown algae, the kelp) have intercalary growth, the Ectocarpales (small filamentous brown algae) have diffuse growth and the Fucales (common brown rockweeds) have apical growth. The -ales suffix designates ordinal status.
Family: Laminariaceae. Orders are subdivided into families on the basis of various features. Earlier, most members of the laminarialean family Alariaceae (the winged kelp) had sporophylls (special blades for spore production) and no branching. Most members of the laminarialean family Lessoniaceae were regularly branched and did not have sporophylls. The Laminariaceae lacked sporophylls and branching. Today, we know those features don’t reflect true relationships and the families of kelp are now defined by molecular DNA differences. The -aceae suffix designates familial status.
Genus: Saccharina. We can define a genus (plural: genera) as a group of closely related species that are usually not interfertile and are distinguished on the basis of some relatively small morphological feature, such as branching pattern. There may be several genera in a family. The generic name is always italicized or underlined.
Species: Saccharina latissima (Linnaeus) C.E. Lane, C. Mayes, L. Druehl and G.W. Saunders. Individuals making up a species are thought to be sexually compatible. Different species within a genus are considered to be sexually
Pacific Seaweeds
26
incompatible or at least sexually isolated. In reality, this sexual criterion is rarely confirmed. Most species recognized today were established on the basis of morphological features prior to our understanding of the significance of interbreeding and sexual isolation. A new twist in defining and distinguishing between species (and higher taxonomic groups) is the application of DNA sequences (e.g., see Biodiversity, the DNA Barcode and the Future of Taxonomy, below). The species name is italicized or underlined. Following the species name are other names (not italicized), which give more information about the species. The “(Linnaeus)” in the species name above tells us that Swedish scientist Carolus Linnaeus was the first to describe this seaweed. He called it Fucus saccharina L. Linnaeus is unique among humans in that he is recognized by the letter L alone. Later, C.E. Lane, C. Mayes, Druehl and G.W. Saunders transferred the species to the genus Saccharina with the species name latissima. “Species” is both singular and plural.
Seaweed names are sometimes presented in this book with single quotes (e.g., ‘R. californica’). These represent species of uncertain taxonomic status: they may be a new species or one already described—more work is needed. Until then, the former name in single quotes is used.
Biodiversity, the DNA Barcode and the Future of Taxonomy
“How many species of seaweeds are there?” is a deceptively simple question we are frequently asked. The answer: many more than we currently know! At the close of 2015 the excellent online database AlgaeBase includes roughly 15,000 seaweed species. This breaks down to roughly 2,000 browns, 6,000 greens and 7,000 reds. Compared to perhaps more familiar groups such as birds (approximately 10,000 species) and mammals (approximately 5,500 species), seaweeds are more diverse. And more mysterious. Scientists predict we will uncover relatively few more birds and only a smattering of new mammals; for seaweeds, we probably have thousands of species left to find.
Identifying seaweeds based on what they look like is difficult, even for experts. Seaweeds have relatively simple bodies—no eyes, flowers, feathers, etc.—and many species have only subtle differences in their appearance. Kelp are the exception, a group of easily identified species, but even here there can be hidden diversity (see Saccharina druehlii, p. 205). Adding to that is the ability of most seaweeds to be “phenotypically plastic”; in other words, the size, shape, number of branches, even colour of an individual
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About Seaweeds
Paul Silva
“On October 4, 1941, we took our first field trip, to Whites Point near San Pedro. I was amazed and even ecstatic at the sight of so many beautiful seaweeds growing on the rocks at low tide. I had gone to the beach innumerable times, but always on sandy shores and never at an extreme low tide. I changed academic pathways immediately, from higher plants to marine algae.”
Paul C. Silva (1922–2014) remembered so clearly when he fell in love. His subsequent illustrious career revolved around service to phycological societies, to the International Botanical Congress and to the University of California, Berkeley, Herbarium, where he was curator of algae for 50 years. He was an expert in nomenclature, the intricate lineages of names and their proper assignment, and his encyclopedic knowledge was generously shared with those who created or changed names of algae. His
