The Smithsonian's Global Genome Initiative (GGI) goal is to collect at least one species from half of the genera (estimated 160,000 -200,000) on Earth by 2020. We are looking forward to helping them towards their goal, while learning how to make quality museum vouchers of plant species, seeing a slice of Hawaiʻi’s unique flora, exploring the island, and hopefully answering some of our own conservation and evolutionary questions about Hawaiian plants along the way.
We are collecting members of the Compositae (daisy family or Asteraceae) on Hawaiʻi Island. The Compositae are the world’s second largest family of flowering plants—and Hawaiʻi’s—represented in Hawaiʻi by 91 native species. The Compositae contain some of Hawaiʻi’s most well-known plants, the Silverswords and Bidens, which are famous examples of adaptive radiation (the rapid diversification of species in a single lineage to fill many ecological roles). Species grow in a wide variety of habitats from sea level to the tops of Mauna Kea and Mauna Loa, exhibit unique growth forms, and range from highly abundant to critically endangered with less than 100 individual plants left in the world.
Our first collection was Dubautia plantaginea subspecies plantaginea, a species that is present on most of the main Hawaiian Islands (excluding Niʻihau and Kohoʻolawe), but only found in the Kohala region of Hawaiʻi Island. It grows in mesic (moderate moisture) to wet conditions, and is most common in windward gulches in Kohala which are difficult to access. To avoid helicopter travel, we sampled from an outplanted mesic population in the Koaiʻa Corrdior on the leeward side of Kohala Mountain. Although wild individuals were nearby, we wanted to capture an inflorescence for our vouchers, and only outplanted individuals were flowering.
D. plantaginea is easily identifiable on Hawaiʻi Island by its woody, tree-like growth form, opposite, lanceolate, serrated leaves, and inflorescence characteristic of the aster family (false involucre, heads of many florets, achenes). Different subspecies occur on Maui and Kauaʻi.
With much of the legwork out of the way (supplies and permits), collecting will begin in earnest, and this blog will see regular updates. Discussion will involve voucher collection, the Compositae, and various aspects of natural history in Hawaiʻi.
March 8, 2017
Starting collection for the Global Genome Initiative, we knew there would be challenges. We assumed one of those challenges would be locating rare species, but collecting recently in Hawaiian Volcanoes National Park (HAVO), we had the opposite problem.
Pseudognaphalium sandwicensium is a perennial herb common in disturbed, dry areas throughout Hawaiʻi. Living up to its common name, cudweed, it is abundant and appears in weedy patches along roadsides, such as along Hilina Pali Road, where we were collecting in HAVO.
Although this is the only native Pseudognaphalium in Hawaiʻi, there are three recognized subspecies occurring on Hawaiʻi Island, and we are collecting taxa to the subspecies level.
As we were not familiar with this species and its subspecies, we tried to do our homework. Looking in the Manual of Flowering Plants of Hawaiʻi, the distributions of the three varieties—hawaiiense, kilaueanum, and sandwicensium—overlap. Subspecies hawaiiense is described as being very fragrant with heads loosely arranged within clusters, kilaueanum has shiny involucral bracts and achieves the longest stem length, and subspecies sandwicensium has potentially larger leaves (although all the three ranges exhibit overlap) with glabrate involucre bracts, except at the base.
Unfortunately, these features are not always clear cut in the field: How do you compare “very fragrant” and “loosely arranged heads” if the specimens you examine appear the same and all have the same fragrance and head arrangement? Were two subspecies not there to see these distinguishing features, or were we not being discerning enough?
After examining herbarium specimens and consulting with HAVO’s botanist, it is still hard to be 100% certain about our assessment. In the end, we used stem length to decide our collections were subsp. kilaueanum, but we may need to consult an expert to make sure we collect the other two morphologically recognized subspecies so our vouchers and associated genetic data exhibit the original intent of the subspecies designations.
Sometimes certainty is scarce when trying to compartmentalize life. The Manual of Flowering Plants of Hawaiʻi itself states that certain varieties intergrade, and that, “this complex is in need of careful study, especially since 3 of the 4 distinctive entities have overlapping distributions yet apparently maintain themselves without any visible ecological differences.…”
Although we struggle so far to see these distinctive entities, genetic resources made available through the careful collection of these three subspecies could help confirm isolated populations of verifiable subspecies, or a large, diverse population with high variability and gene flow.
It’s one thing to read about evolution in a textbook, it’s another to see its outcomes firsthand in a couple afternoons. Students in the Advanced Tropical Island Ecology and Evolution Lab are getting that opportunity by exploring the Compositae on Hawaiʻi Island.
Following collection in Hawaiʻi Volcanoes National Park, we now have three members of the genus Dubautia, a member of the adaptive radiation commonly referred to as the Silversword Alliance. A single ancestor from California arriving in the islands approximately 5.2 million years ago radiated to 32 species in the three endemic genera Argyroxiphium, Dubautia, and Wilkesia.
In the park, we collected both Dubautia scabra subsp. scabra and Dubautia ciliolata subsp. ciliolata. It is easy to see the similarities between these two taxa: both are woody shrubs growing in open environments on relatively new lava flows with shared morphological features (see pictures). In fact, hybridization between the two is reportedly common.
What is striking is how different morphologically and ecologically these species are from Dubautia plantaginea (see first post), a species growing up to seven meters tall in forested environments on well-developed soil.
In the following weeks, we will continue to collect more specimens highlighting the diversity of Dubautia, and are looking forward to exploring how well genetic barcodes differentiate between species and subspecies within this genus, the larger Silversword Alliance, and Hawaiian Compositae in general.
April 15, 2017 Collecting above the Clouds
UH Hilo students had the opportunity to follow the Hawaiian Asteraceae to their highest elevations at the end of March, collecting on the slopes of Mauna Kea that still held snow from a winter storm three months earlier.
Rising over 4,200 meters above sea level, Mauna Kea presents an extreme alpine environment: less than 200 millimeters of annual precipitation, extreme temperature swings, high solar radiation, and strong winds.
Our sights were set on three species, two additional examples of the silversword alliance that we have written about before: Dubautia arborea and Dubautia ciliolata subsp. glutinosa, and Tetramolopium humile subsp. humile.
All three taxa have adaptations to cope with the harsh conditions present high on the mountain. D. ciliolata glutinosa and T. humile humile form compact, dwarf shrubs with hairy leaves. While D. arborea can be much taller, it retains hairy leaves and appears to prefer sheltered habitats as elevation increases to protect itself from the wind.
All tissue collections were sent to the Smithsonian, and our first set of genetic information was recently received back. With this initial dataset, students will begin to compare how DNA barcodes that are routinely used to discriminate species outside Hawaiʻi work on Hawaiian Asteraceae.
Questions include how well barcodes discriminate subspecies (D. ciliolata glutinosa vs. D. ciliolata ciliolata), species (Dubautia scabra vs. Dubautia arborea), genera in separate radiations (Dubautia vs. Tetramolopium), and eventually genera in the same radiation (Dubautia vs. Argyroxiphium).
More photos and information on new collections, and observations from our initial molecular data analysis will be shared soon.