Abstract Detail

Time to dig: the importance of underground storage organs in plant evolution

Howard, Cody Coyotee [1], Cellinese, Nico [2].

The evolutionary and ecological significance of size in bulbous monocots.

Plants bulbs are modified shoot systems comprised of short internodes with apical bud(s) surrounded by concentric layers of leaf bases and/or bulb scales; however, they are far more complex once we begin to look more closely at their anatomy and morphology. Leaf base and bulb scale size, number, and arrangement can vary greatly within and among clades. Bulb diameter can also vary greatly, with overall bulb size playing a significant role in flower formation and timing, and thus affecting fitness, as well as resource allocation. Despite the importance of bulb size to the overall fitness of an individual, evolutionary and ecological aspects of this trait have been almost completely neglected. Examining over 2500 herbarium vouchers for 116 taxa, we analyzed monocot bulb size in a phylogenetic context in order to test hypotheses related to its evolutionary significance. We found that there are two bulb diameter optima with mean values of 2.3 and 4.2 centimeters. Furthermore, we found that larger bulbs are associated with hysteranthous leafing, a habit where leaves appear separately from flowers. This finding lends some support to previous hypotheses stating that larger bulbs are associated with hysteranthy since plants rely on previously stored resources to flower rather than on photosynthetic output. Also, we see that as bulb size increases, taxa are able to occupy habitats which experience greater rainfall variability and less temperature seasonality. This suggests that larger bulbs can withstand greater differences in annual precipitation due to larger belowground resources; however, they likely require warmer temperatures in order to fully replenish these stores through photosynthesis (i.e. the leaves must remain aboveground longer, thus more exposed to frosts). Lastly, we found that shifts to larger overall bulb size are relatively rare, with only three strongly supported instances of bulb diameter increases: two in Scilloideae (Asparagaceae) and one in the Amaryllidaceae. This work highlights the importance of including often overlooked underground plant organs into ecological and evolutionary studies in order to gain a more complete understanding of plant evolution.

1 - University of Florida, Florida Museum of Natural History, 1659 Museum Rd., Gainesville, FL, 32611, USA
2 - University Of Florida, FLORIDA MUSEUM OF NAT. HISTORY, 1659 Museum Rd, 354 Dickinson Hall, Gainesville, FL, 32611, United States

Keywords:
geophytes
bulbs
monocots
ecology
evolution.

Presentation Type: Colloquium Presentations
Session: CO07, Time to Dig: the importance of underground organs in plant evolution.
Location: Tucson J/Starr Pass
Date: Tuesday, July 30th, 2019
Time: 11:00 AM
Number: CO07009
Abstract ID:271
Candidate for Awards:None