Abstract Detail

Anatomy and Morphology

Bullock, Madison [1], Simonin, Kevin [2], Cantley, Jason [2].

Morphological adaptations within a young adaptive radiation of Hawaiian Chenopodium (Amaranthaceae).

Chenopodium oahuense is the sole species of Chenopodium in the Hawaiian Archipelago and generally inhabits a variety of xeric habitats including rocky sea cliffs, sandy beaches, and dry to mesic forests. However, as this taxon is morphologically variable across these habitats, a number of additional taxa have previously been split from and eventually recombined into a diverse C. oahuense. The Cantley Lab at San Francisco State University is in the process of describing a novel subspecies, Chenopodium oahuense subsp. ilioensis, from the northwestern portion of Moloka‘i. This taxon differs from the typical form of C. oahuense by its smaller, succulent leaves, smaller seed size, and prostrate to scandent habit. Local botanists recognized that these characters were likely significant enough to distinguish this subspecies from C. oahuense s.l. across the rest of the Hawaiian Archipelago and therefore wish to formally suggest that this taxon should be listed as Federally Endangered per IUCN (2012) criteria. The primary aim of this study is to add to important taxonomic work in separating C. oahuense subsp. ilioensis through landmark analysis, leaf outline analysis, and shape feature analysis of both herbarium and live specimens. Preliminary data from three populations of C. oahuense s.l. and three C. oahuense subsp. ilioensis populations suggest that all populations exhibit some form of leaf heteroblasty: juvenile plants generally have larger leaves that begin to significantly decrease in size as plants age into flowering adults. However, it is not clear if this change is due to environmental factors such as decreased precipitation as flowering in adults more or less corresponds to a dry summer season across the archipelago. Moreover, the heteroblastic change in individuals of C. oahuense subsp. ilioensis is much more pronounced. Adult leaf morphology of C. oahuense subsp. ilioensis leaves is smaller, thicker, and succulent, whereas juvenile leaves are quite similar to C. oahuense s.l. leaves from across the archipelago. We hope this study will help to further document age dependent leaf heteroblasty for C. oahuense across the archipelago and detail the remarkable morphological transition in C. oahuense subsp. ilioensis. In turn, these data may allow for a better understanding of important evolutionary adaptations occurring in small succulent leaves of a windswept sea cliff environment and provide insight into the morphology and evolutionary diversity of a newly described taxon.

1 - San Francisco State University, Department of Biology, 1600 Holloway Avenue, San Francisco, CA, 94132, USA
2 - San Francisco State University, Department of Biology, 1600 Holloway Avenue, Hensill Hall, San Francisco, CA, 94132, USA

Keywords:
Chenopodium oahuense
new subspecies
Morphometrics
leaf morphology
speciation
Chenopodium
heteroblasty
Hawaiian Islands.

Presentation Type: Poster
Session: P, Anatomy and Morphology Posters
Location: Virtual/Virtual
Date: Monday, July 27th, 2020
Time: 5:00 PM Time and date to be determined
Number: PAM003
Abstract ID:445
Candidate for Awards:None