Kenneth G. Karol

Profile

From microscopic single-celled species to giant seaweeds many meters long, algae are diverse and ancient organisms that can be found in virtually every ecosystem on earth. For millions of years algae have exerted profound effects on our planet. As primary producers, algae provide food and shelter for many organisms as well as provide a significant percent of the oxygen we breathe. Algae are locally important water quality indicators and globally important sequesters of carbon dioxide, the major greenhouse gas involved in global climate change. Kenneth Karol’s research program strives to incorporate traditional botanical approaches with contemporary molecular biology techniques toward understanding questions ranging from comparative genomics of green plants to species diversity, taxonomy, and systematics in the Characeae, to invasive species biology, and natural history collections.

Evolution of green plants

Green plants are a diverse group of organisms that include green algae and land plants. The number of known species (estimates range from 7,000-22,000) is surely an underestimate of global green algal diversity because many species have only recently been discovered and taxonomic concepts in green algae are changing rapidly. Green algae are distributed on all continents and across virtually every habitat type on Earth and nearly 90% of green algae are freshwater species. They are abundant and play important roles in terrestrial and aquatic habitats, from extremely dry deserts to hypersaline ponds, to coral reefs, and as symbiotic photobionts with lichens and animals. Although recently molecular studies have revealed two major clades of green plants (marine groups and several freshwater lineages in one clade, and several freshwater groups plus land plants in the other), the relationships among major lineages within the green plants are poorly known. Moreover, within the major groups, relationships and monophyly of many traditionally defined subgroups are poorly resolved. Given that land plants inherited their plastids, mitochondria, and basic genetic toolkits from the green algae, the current state of phylogenetic knowledge of green plants makes green algae one of the most important yet understudied branches on the eukaryotic tree of life.

Ken works closely with collaborators, post-docs, and students to resolve large areas of uncertainty in the phylogeny of all major groups of green algae, clarify their relationship to land plants, and compile extensive genomic data sets that are being used to address questions of gene and genome evolution. The phylogeny of green algae is critical to understanding the evolution of form, function and structure in the lineage that gave rise to land plants and is essential to understanding the origin and evolution of the complex derived morphology of land plants and the underlying genetic tool kit that they inherited from their green algal ancestors.

Phylogeny, evolution, and systematics of the Characeae

The Characeae, more commonly known as stoneworts or muskgrasses, are a lineage of green algal macrophytes that have a rich fossil record dating to the Late Silurian (~430 million years old). My research uses both morphological and molecular methods (traditional Sanger and Next-Generation sequencing) to re-evaluate the taxonomy of the Characeae, which are common in freshwater lakes worldwide and are ecologically important as food and habitat for invertebrates and small fish. Characeae have an intricately branched plant body and complex sexual reproduction, and they are considered closely related to the first plants that invaded land some half a billion years ago. Characeae are also used in habitat remediation and are important model organisms in studies of cell biophysics and physiology.

DNA sequence data are being generated from nuclear, plastid, and mitochondrial genes that are being used to revise the current confused classification (Wood and Imahori, 1965). This classification summarizes a large body of diverse work and presents a novel taxonomic treatment for the family but after more than 55 years, this work remains the only worldwide treatment and is controversial. It is founded on gross morphological similarity rather than on shared derived characters. Under this intuitive approach, approximately 400 species of Characeae were reduced to intra-specific ranks (i.e., variety or forma) or submerged into synonymy resulting in just 81 broadly defined species. My long-term goal is to provide critical data for worldwide studies of conservation, diversity and evolution and to produce a robust and stable classification system for this ancient and diverse lineage.

Aquatic invasive species

Freshwater ecosystems are rich in biodiversity, economically important, and increasingly impacted by human activities, including climate change. These systems are considered one of the most threated ecosystem on the planet. Many factors contribute to this including pollution from agriculture, but a major contributing factor to the degradation of freshwater systems is Aquatic Invasive Species (AIS). Aquatic macrophytes, especially members of the Characeae, are vital components of freshwater ecosystems. They provide forage for birds, invertebrates, and fish and are important for colonizing new habitats and stabilizing sediments. Aquatic invasive macrophytes can outcompete native species, alter water chemistry, impede fish spawning and inhibit recreation. Nitellopsis obtusa (Characeae) has a widespread, yet rare distribution in its native range of Asia and Europe. Previously unknown in the New World, the first record of N. obtusa in North America was in the St. Lawrence River in 1971, where it is hypothesized to have been introduced by ballast water from trans-oceanic shipping. Currently, N. obtusa is known from 100’s of lakes from Vermont to Minnesota, including the Great Lakes. My research program is studying the distribution, phenology and genetic landscape of N. obtusa in its native and invasive range not only to minimize further spread but also to achieve effective control measures.

Algae Collections

Collections and curation are the foundation of a strong research program in organismal biology. As storehouses of information for scientists, historians, and conservationists, herbaria document and preserve important aspects of biological diversity toward understanding how this diversity has been affected or altered over time. Herbaria are, thus, indispensable to our understanding of the Earth’s biodiversity. Angiosperms, not surprisingly, dominate most herbarium collections. Freshwater algae are often overlooked by collectors and as a result are grossly underrepresented in most collections. Furthermore, freshwater algal collections have suffered over the last 50 years with fewer phycologists being trained in floristics and taxonomy, and those being trained often study marine algae.

NYBG houses approximately 260,000 historic algae collections, including nearly 5,000 type specimens. Approximately half of these are from North America. Of the remaining half, specimens collected in the Caribbean region and Central and South America predominate. Particularly important collectors represented include T. F. Allen, F. S. Collins, M. A. Howe, and R. D. Wood. The entire collection has been recently curated and assessed with the assistance of NYBG staff, post-doctoral fellows, graduate and undergraduate students, as well as interns and volunteers. The collection is stored in new cabinets with new folders and folder labels. It is filed in a contemporary phylogenetic framework and is reorganized as new phylogenetic results are published and as new collections are added. This collection represents one of the most important algal collections in the world and, with the exception of about 55,000 cyanobacterial specimens, is almost entirely available online (i.e., NYBG Virtual Herbarium and macroalgae.org). Updating annotations and editing the digital catalog is an ongoing process.