The Plant Press

Parasitic plants: Important components of biodiversity

From Plant Press, Vol. 22, No. 4, October 2019.

By Marcos A. Caraballo-Ortiz

Parasitic organisms are generally viewed in a negative way because of their ability to “steal” resources. However, they are biologically interesting because their dependency on hosts for survival have influenced their behavior, morphology, and genomes. Parasites vary in their degree of necessity from a host, ranging from being partially independent (hemiparasitic) to being complete dependent (holoparasitic). Some parasites can live independently, but if they find potential hosts, they can use them to supplement their nutritional needs (facultative parasitism).

Laurel dodder (Cassytha filiformis, Lauraceae) twining around the stems of its host (Croton sp., Euphorbiaceae) on Providenciales Island, Turks and Caicos. (photo by M. Caraballo)

Parasitism is not a phenomenon unique to animals, as there are plants parasitic to other plants. Current biodiversity estimates indicate that approximately 4,700 species of flowering plants are parasitic, which account for about 1.2% of the total inferred number of plant species in the world. About half of the known species of parasitic plants belong to a single order, Santalales, which is diverse and mainly composed of hemiparasites. However, parasitism has evolved independently in 11 lineages of angiosperms comprising 27 families, some of them small and consisting of only one species. Parasitic plants have been able to colonize almost every corner of the world (except the polar regions), and many are common in lowlands and disturbed habitats. Only a few parasitic plants yield economically important products such as the sandalwood, obtained from the tropical shrub Santalum album (order Santalales). Other products are local and include traditional medicines, food, and crafts like “wood roses”. Many parasites are also considered agricultural pests as they can impact crops and timber plantations.

Origin and diversification of the sunflower family

From Plant Press, Vol. 22, No. 3, July 2019.

A study that explores the origin and diversification of Asteraceae, the sunflower family, was recently published in Proceedings of the National Academy of Sciences (https://dx.doi.org/10.1073/pnas.1903871116). Asteraceae, composed of an estimated 25,000-30,000 species, accounts for nearly 10 percent of all flowering plants. Global in distribution, the family occupies nearly every type of habitat on Earth and is marked by a complex inflorescence exemplified by the North American sunflower, in which individual flowers are clustered to mimic a single, large flower to lure pollinators. The origins, migration routes, and patterns of diversification that led to the family's ecological success remain unclear.

Floral diversity of tribes in the Asteraceae family. A recent study suggests the family originated in the Late Cretaceous Period in South America and later migrated to Africa where it diversified rampantly. (A) Barnadesieae; (B) Famatinantheae; (C) Stifftieae; (D) Mutisieae; (E) Hecastocleideae; (F) Pertyeae; (G) Cardueae; (H) Vernonieae; and (I) Heliantheae. (Image courtesy of PNAS)

Using phylogenetic analysis of nearly 1,000 genomic locations in around 250 species, Jennifer Mandel (University of Memphis) and colleagues, including Vicki Funk (Smithsonian Institution), found that the family likely originated around 83 million years ago in the Late Cretaceous Period in southern South America. The earliest diversification out of South America may have occurred around 50 million years ago, during a period of dramatic climate change. Subsequently, the family rampantly diversified during the middle-to-late Eocene epoch, 42-37 million years ago, a period marked by global cooling, resulting in more than 95% of existing species.

Biogeographical analysis suggests that the family migrated to North America, south and central Africa, and Asia, with ancestral range estimates suggesting different possible dispersal routes out of South America. Regardless of the route, the family's prolific diversification and global colonization likely began once it reached Africa around 42 million years ago.

According to the authors, the findings illuminate the evolutionary processes underlying the wide reach and vibrant diversity of a major group of flowering plants.

-Adapted from EurekAlert

Designing a state-of-the-art taxonomic research workstation

From Plant Press, Vol. 22, No. 3, July 2019.

As botanists develop more knowledge the science of taxonomy becomes increasingly complex. Between 1753 and 2016, the number of known plant species has risen from about 6,000 to 390,000, an average increase of nearly 1,500 species each year. Over 2,000 new species were discovered in 2015. The number of specimens held globally in herbaria has also increased. There are now over 3,000 herbaria around the world holding nearly 400 million specimens.

A large number of specimens are still being collected and these all need to be identified, digitized and included in revisions, with some undoubtedly being new species. (photo by Elspeth Haston)

Any taxonomist working now therefore has an immense and expensive task of gathering information about the species that they are studying, involving travel to various herbaria or the risk of damage or loss to specimens if they are sent on loan. With about 10-20 percent of flowering plant species still to be described, it is estimated that about half of these have already been collected and are held in herbaria around the world.

Scientists need to find solutions to making collection information more widely accessible in order to speed up the research process given the scale of the challenges they are facing. In many cases, a high-resolution digital image of the specimen with electronic collection data attached will enable researchers to carry out much of the basic work. By digitizing botanical collections, herbaria can provide these resources to taxonomists in every part of the world.

New heights for bryophytes

From Plant Press, Vol. 22, No. 2, April 2019.

By Julia Beros

From the Smithsonian Castle to the National Museum of Natural History, the fifth floor to the third, the Bryophyte collection at the U.S. National Herbarium has seen many homes, but is now settling into a more permanent and modern residence. With many specimens still in newspaper and shipping boxes, it is high time that these collections get some extra attention. Through a Collections Care and Preservation Fund (CCPF) award for fiscal year 2017, the Department of Botany received funds to curate and rehouse two groups of specimens: the bryophytes and the algal wet collections.

Edgar Mearns, a naturalist and ornithologist, collected more than 3,000 natural history specimens, including this unidentified moss from British East Africa (now Kenya), during the historic Smithsonian-Roosevelt African expedition of 1909-1910. (photo by Miguel Montalvo)

A bit like packing for a big move, Smithsonian contractors Karen Golinski and Zuvayda Abdurahimova have begun to clear out and inventory the bryophyte cases to prepare and accurately evaluate the collections, which include all of the mosses, liverworts, and hornworts. Beginning just this past October, much has already been discovered about the Smithsonian’s long tucked-away bryophytes.

With a legacy set in place by curator emeritus Harold Robinson and his predecessor Bob Ireland, the bryophyte collection has been longing for further curation in the current decade. Though they have not yet been counted, there are an estimated 125,000 total bryophyte specimens in the herbarium, with approximately 10,000 specimens housed in the off-site Museum Support Center in Suitland, Maryland.

Treasures abound among the bryophytes, including a handful of specimens collected by naturalist Edgar Mearns for the Smithsonian-Roosevelt African expedition of 1909-1910 (while Theodore Roosevelt, in search of specimens for the new Natural History Museum, hunted elephants, Mearns, a naturalist and ornithologist, fervently collected more than 3,000 natural history specimens during this historic expedition). Aside from material collected under the auspices of Smithsonian sponsored expeditions such as the Roosevelt Expedition, the bryophyte collection at the US Herbarium also houses a great many exchange vouchers, including numerous specimens from Wilfred Schofield’s many explorations of the Pacific Northwest. For Bryologists across the globe, the information housed at the Smithsonian has been largely shrouded and overlooked because of its inaccessibility and lack of exposure, and thus the collections have been massively understudied, while the research potential in these collections is huge considering that many are still unidentified.

The digitization conveyor project hits 2 million scans

From Plant Press, Vol. 22, No. 1, January 2019.

After three years of production, the Department of Botany is excited to announce that the Botany Digitization Conveyor Belt has reached 2 million scans of botanical specimens this December 2018. This number also coincides with the transcription of 1.5 million conveyor specimen images. Total number of inventoried specimens from the US National Herbarium has now reached over 3 million records, and can be found in our online catalog (https://collections.nmnh.si.edu/search/botany/).

Sarah Evans prepares to scan an herbarium specimen. (Photo by I. Lin)

These landmark figures are the result of very hard work from the Department of Botany and the Smithsonian’s Digitization Program Office staff, in collaboration with the digitization company Picturae. The Botany Conveyor Belt runs five days a week, capturing the images of 3,000-4,000 pressed specimens every day, or one specimen image every 4-6 seconds. Staff are continually preparing, moving, scanning, filing, and repairing botanical specimens for this long-term project.

Euonymus americanus (Celastraceae), just one of the 2 million scanned botanical specimens from the US National Herbarium.

Which plant families can be found in the online catalog? The digitization team has completed a large portion of the dicotyledons, including Asteraceae, Fabaceae, Rubiaceae, Melastomataceae, Acanthaceae, Ericaceae, and many more. The pteridophytes and Cyperaceae are also complete. The team is now working their way through the last third of the dicots, and expect to be 80 percent complete with this group by late spring 2019. The goal is to digitize all pressed specimens in the US National Herbarium within the next three years, funding permitted. Stay tuned for updates in the coming months and years.

Botany website redesign

From Plant Press, Vol. 22, No. 1, January 2019.

The National Museum of Natural History has launched a new website at https://naturalhistory.si.edu/. The new visitor-focused site works on both desktop and mobile screens, integrates with multiple Smithsonian-wide systems, and has improved accessibility and adherence to current accessibility standards and requirements. The new Museum website includes a redesign to the research department webpages, including the Department of Botany—now found at https://naturalhistory.si.edu/research/botany.

Botany homepage navigation begins with the orange circle in the lower left of the screen. Click on this and you see “Botany” with a subordinate list of choices:

• About
• Research
• Collections Access
• Resources
• Opportunities
• News and Highlights
• Staff
• Contacts

Navigation of the newly redesigned Department of Botany website at https://naturalhistory.si.edu/research/botany begins with the orange circle on the left of the screen.

The About page presents a short history of the U.S. National Herbarium and the Department of Botany. Research dives into the current research specialties of the Botany Curators, organized by geographic, taxonomic, and other special interests. Examples include Guiana Shield, Hawaiian Islands, West Indies, Lianas and Climbing Plants of the Neotropics, Onagraceae, and Zingiberales.

If you are looking for specimens, images, loans, or access to the Herbarium, visit Collections Access. The Resources page provides digital resources, nomenclatural tools (Index Nominum Genericorum, Appendices I-VII of the International Code of Nomenclature for algae, fungi, and plants), and access to newsletters and journals (Contributions from the U.S. National Herbarium, Smithsonian Contributions to Botany).

The Opportunities page offers information for the visiting researcher, such as how to find and apply for travel awards, fellowships, internships, and volunteer positions. The News and Highlights page will focus on the latest events and other activities sponsored by the department, such the Smithsonian Botanical Symposium.

If you are looking for a staff member of the Department of Botany, visit the Staff page. The Department’s mailing address, phone number, fax number, and email address is available on the Contacts page.

Asexuality as a detour, not a dead end

From Plant Press, Vol. 22, No. 1, January 2019.

By Kathryn Picard

Historically, asexuality has been seen by evolutionary biologists as a short-term solution to a long-term problem, with any temporary competitive advantages derived from eschewing sex eventually overshadowed by the absence of mechanisms to increase genotypic diversity. Yet, despite its ostensible limitations, asexuality is a widespread reproductive strategy, especially among ferns where it is generally manifested as apomixis.

Reproductive mode data is available for only a few fern lineages, thus the relative abundance of apomictic species is likely underestimated. Adiantopsis asplenioides (Pteridaceae, Polypodiales) is the first reported apomictic species for the genus.

Apomictic ferns deviate from the typical fern sexual life cycle in two ways: 1) the production of unreduced spores through meiosis, and 2) the development of an adult fern (sporophyte) from the somatic tissue of the free-living gametophyte without the fusion of sperm and egg. For the few fern lineages that have been adequately studied, approximately 10% of species have been found to be apomicts. Across angiosperms, the incidence of apomixis is markedly lower, with fewer than 1% of species understood to exhibit this reproductive mode. With both the potential evolutionary pitfalls of asexuality and the broad disparity between ferns and angiosperms in mind, it seems only natural to ask why apomixis has played such an outsized role in fern diversification.

Reproductive mode and ploidy level are important life history characters that can inform phylogenetic studies and taxonomic revisions of fern taxa. This is particularly true in groups where homoplasy due to shared ecological habits can mask—or, alternatively, falsely suggest—hybridization and/or speciation. Yet, for the overwhelming majority of fern specimens housed in herbaria, these data are not available. The primary goal of my postdoctoral work is to apply classical spore analysis techniques to the fern collections in the United States National Herbarium to establish both reproductive mode and ploidy level estimates for the most diverse fern order, Polypodiales.

Comprising approximately 80% of extant fern species, the Polypodiales lineage is distributed globally and exhibits myriad morphologies corresponding to an equally broad range of ecological habits. Unifying these otherwise disparate taxa is the generally consistent production of 64 spores per sporangium in sexually reproducing individuals. By contrast, apomictic individuals produce half the number (usually 32, but sometimes 16) unreduced spores per sporangium, allowing for the relatively easy discrimination between sexual and asexual individuals. Furthermore, as spore size is positively correlated with genomic content, we can use mean spore diameter to estimate ploidy level for closely related species (and sometimes genera), thus providing insight into the distribution of polyploidy—which is often associated with apomixis—across ferns.

By The Numbers: Digitization Edition

From Plant Press, Vol. 21, No. 4, October 2018.

As the Department of Botany approaches digitizing its 2 millionth specimen later this year, it’s worth noting some important numbers and figures in its effort to digitize the United States National Herbarium’s collection of nearly 5 million specimens.

9

The number of full time staff at work on the rapid digitization project,
which began in October 2015.

120

The number of plant families digitized.
The list of inventoried plant groups is available online.

225,000

The number of specimen folders completed.
The botany collections can be searched online.

 

Untangling Indian Hemp

From Plant Press, Vol. 21, No. 4, October 2018.

By Nora Frankel

Plants have always been an integral part of human material history. This may be no surprise to a botanist, but for me, it is sometimes still a revelation. As a conservator, it is my job to understand the material as well as the intangible properties of cultural heritage items so that I can ensure their preservation. Plants became my focus while completing a two-year postgraduate Andrew W. Mellon Fellowship in Textile Conservation at the Smithsonian Institution National Museum of the American Indian (NMAI) Cultural Resources Center (CRC) in Suitland, Maryland. Working with textile conservator Susan Heald (NMAI), physical scientist Thomas Lam (Museum Conservation Institute), and Marcelo R. Pace (National Museum of Natural History’s Department of Botany), I have been studying identification of certain plants used for fibers throughout North America’s northeast woodlands. This region encompasses the Great Lakes, New England, and southern Ontario and Quebec, and has been home to a diversity of culture groups including the Anishinaabe, Haudenosaunee (Iroquois), Abenaki, and Lenape.

• Nora Frankel in the Botany Plant Anatomy Laboratory microtoming embedded plant fibers. (photo by Stanley Yankowski)

While several types of plant fibers are used in the woodlands, I focused on fibers extracted from the primary phloem (pericyclic fibers) of herbaceous plants and secondary phloem of the inner bark of certain tree species. In textile terminology, these are referred to as “bast” fibers, and include the more familiar linen from flax (Linum usitatissimum L.), as well as hemp (Cannabis sativa L.), ramie (Boehmeria nivea L. Gaudich.), and jute (Chorchorus spp.). Although many different species have been used for textiles in North America, identification is difficult, and fibers are sometimes grouped under the misnomer “Indian hemp.” This is a common name for several species from the Apocynaceae family, but has also been used to describe any plant fiber from North America. Being neither Cannabis nor from India, this terminology can be confusing, and was part of the impetus for this study.

Twined Potawatomi bag with indigenous bast fibers, dyed commercial wool fibers, and hide (NMAI 2/7533).

Cuatrecasas Travel Award Recipient Examines Nyctaginaceae Anatomy

From Plant Press, Vol. 21, No. 4, October 2018.

Israel Lopes da Cunha Neto, a doctoral student from the University of São Paulo, Brazil, is a recipient of a 2018 Jose Cuatrecasas Travel Award. He visited the US National Herbarium in August to work on his project, “Diversity and evolution of the vascular system in Nyctaginaceae.” His research aims at integrating data on the ontogeny and anatomy of the vascular system of Nyctaginaceae stems within a phylogenetic context in order to understand its development, diversity, distribution, and evolution.

Israel Lopes da Cunha Neto at work in the Plant Anatomy Lab studying Nyctaginaceae anatomy. (photo by Stanley Yankowski)

During Cunha Neto’s visit, he examined, sampled, and carried out anatomical analysis of wood specimens from the Nyctaginaceae family obtained from the Wood Collection of the Smithsonian’s National Museum of Natural History stored in the Museum Support Center (MSC) in Suitland, Maryland. He selected 46 of the 130 Nyctaginaceae specimens to sample. While working in the Plant Anatomy Lab under the supervision of Stanley Yankowski, he sectioned, stained, and mounted slides of the samples, which are now part of the US slide collection. At the University of São Paulo, Cunha Neto will continue to work on the remaining specimens that he did not process during his visit, and he will send duplicate slides back to NMNH. This objective also included analysing microslides from the US wood collection, both from Nyctaginaceae and other related families from the order Caryophyllales.

Another objective of Cunha Neto’s visit was to study the Nyctaginaceae collection of pressed specimens to familiarize himself with plants he had not collected, enrich his database and select localities for his forthcoming field trips to collect fresh material for anatomical studies. With proper authorization, he sampled stem portions from 14 voucher specimens, which will also be useful for his anatomical study.

Cunha Neto is grateful for his visit and remarks that his research experience abroad “added immense benefits to [his] dreamed career as a botanist, and to [his] aspiration of becoming a distinguished researcher in the field of Botany.” He feels that this opportunity has contributed to the knowledge of the Nyctaginaceae flora both anatomically and phylogenetically.