March 11, 2021

5:00pm Zoom

EcoEvoPub Seminar Series
Department of Ecology and Evolutionary Biology, UCLA

" Graduate Student Presentations "

Kelcie Chiquillo

Department of Ecology and Evolutionary Biology, UCLA, Barber Lab

“A seagrass that invaded two seas drives its own success by both harming native seagrasses and benefiting from that harm” 

1. Species interactions can determine the success of invasive species, making understanding the outcome of these interactions critical for predicting their spread. One framework for predicting invasion success is understanding whether an invader is a driver of its own success or a passenger of community change.
2. We conducted mesocosm experiments in both the Caribbean and Mediterranean testing the outcome of interactions between the invasive  stipulaceaand native seagrasses (Syringodium filiforme and Cymodocea nodosa, respectively). Mesocosms were intact cores with species grown either together or alone. In the Mediterranean, an added reduced density together treatment tested for density effects.
3. In both locations, the invasive plant grew faster with the native than when alone, while also negatively affecting the native. In the Caribbean,  stipulaceaincreased by 5.6 ± 1.0 SE shoots in the Caribbean when grown with the native seagrass, with concurrently greater amounts of both above and belowground biomass. When alone, growth decreased by -0.8 ± 1.6 SE shoots. The opposite pattern occurred for S. filiforme where it only gained shoots when alone (+3.6 ± 0.5 SE) and lost them when with the invasive (-3 ± 3.0 SE), again with similar patterns for biomass. In the Mediterranean, the invasive grown with the native increased shoots (+3.7 ± 1.3 SE) and had greater above and belowground biomass. In contrast, the native C. nodosa did better when grown alone (+1.7 ± 0.4 shoots) and this pattern is similar in all metrics. Further, growth in the Mediterranean, was density-dependent for both species, suggesting considerable intraspecific competition.
4. Combined, these results suggest that a seagrass that invaded two seas drives its own success by both harming native seagrasses and benefiting from that harm. Although it is well documented that invasive species can have negative impacts on natives, our study represents a novel example of native species facilitating the success of an invasive in both its historic invasive range and a newly invaded range, providing one possible mechanism for the widespread success of this invasive species.

Marvin Browne

Department of Ecology and Evolutionary Biology, UCLA, Sack Lab

“Prediction and Ecological Consequences of Variation in Leaf Drought Traits”

Among the many constituents of a plant’s environment, water dictates the functionality of most of a plant’s physiological processes. Therefore, it is imperative to clarify how plants acquire, retain, utilize, and lose water to understand how these organisms will perform in a changing environment. My work takes several key steps toward enhancing our capacity to predict plant water status using physically mechanistic relationships and clarifying the ecological implications for the distribution of drought tolerance among individuals, individuals of a given community and across ecosystems. First, I will discuss our noninvasive method predicting key leaf water status metrics: water mass per area(WMA), relative water content(RWC) and leaf water potential(Ψ_leaf). Typical methods for measuring these variables require the excision of tissues and lab analysis, either gravimetric in the case of WMA and RWC, or using the Scholander pressure chamber or psychrometry for Ψ_leaf, and thus measurement of plant water status has often been limited to relatively low throughput and small study scales. Second, I will highlight the importance of intraspecific variation in pressure volume curve parameters, critical traits influencing drought tolerance, and account for this variation to better constrain predictions of leaf water potential. Lastly, I will illustrate the importance of intraspecific variation under drought stress. Overall, this work will examine tested broad trends of drought tolerance relationships across scales in light of intraspecific variation.