2026 December 10th – 2026 O’Neill Grant Recipients

Ava Joseph & Joaquin Lopez Jr.

Ava Joseph

Presenter Bio

Ava is a second-year Ph.D. student at CalBG/Claremont Graduate
University. She received a B.S. in Genetics & Plant Biology
from UC Berkeley, where her work at the botanical garden and
herbaria fostered an interest in systematics and evolution.
Ava is studying the evolutionary history of two sections of
Astragalus (milkvetches), with the goals of clarifying
relationships in this large and complicated genus and understanding
montane and alpine species diversification. She hopes this research
will provide a replicable workflow for future phylogenetic studies
on Astragalus and inform conservation of vulnerable alpine
populations.

Presentation Title

Montane and Alpine Diversification in a Mega-Genus:
A Systematic and Biogeographical Study of Western North American
Astragalus

Presentation Description

Astragalus is the largest plant genus in the world, with
over 3,200 currently recognized species! Western North America is
a hotspot of Astragalus diversity, yet the evolutionary
relationships here remain largely a mystery. Ava’s research focuses
on a subset of taxa (species and varieties) from two sections:
Cusickiani and Ervoidei. These taxa occur in the Sierra Nevada,
Great Basin, and Rocky Mountains.

In the Southern California Transverse Ranges,
Astragalus whitneyi var. whitneyi and
A. filipes are separated by a significant distance from
their next nearest populations in the Sierra Nevada. These
interesting distributions allow Ava to explore the biogeographic
history of these plants and test hypotheses about their origins.
Ava aims to advance our understanding of montane and alpine
Astragalus diversity in western North America.

Joaquin Lopez Jr.

Presenter Bio

Joaquin Lopez is a third-year Ecology and Evolutionary Biology
Ph.D. student at UCI in the Maria Rebolleda-Gomez Lab. Joaquin is
interested in microbial community assembly and how processes such
as selection from host traits, species interactions, and
environmental conditions shape host-associated microbiomes.

Joaquin’s research focuses on natural variation in
Brassica nigra defense chemistry. He also uses
complementary bottom-up and top-down approaches to microbial
community assembly, including synthetic communities and directed
evolution with bacteria derived from B. nigra rhizospheres,
to investigate how microbial communities form and how their
composition influences plant traits.

Presentation Title

Synthetic Microbial Communities Shape Arabidopsis
Life History Across Abiotic Stress

Presentation Description

Microbial communities influence plant phenotypes by shaping
processes such as nutrient acquisition and stress response.
By altering the costs and benefits of resource allocation, they
are likely to impact life history traits, including growth rate,
reproductive timing, and overall fitness. Yet the specific taxa
and interactions underlying these shifts remain poorly understood,
especially under environmental stress. Here, we examine
microbiome-driven shifts in Arabidopsis thaliana
development under abiotic stress using a synthetic community
(SynCom), isolating the effects of individual microbial taxa.

Guided by the stress gradient hypothesis, we predict stronger
microbial effects on host performance as stress increases.
We tested this by inoculating seedlings with (i) monocultures of
eight bacterial isolates cultured from Brassica nigra
rhizospheres, (ii) a co-culture of all eight isolates, and
(iii) a series of dropout combinations to quantify isolate
contributions and higher-order interactions. Plants were
phenotyped across early development, allowing for a direct
comparison of microbial effects on development under salinity
stress.

In parallel, we characterize bacterial growth responses across a
salinity gradient in vitro to determine how individual isolates
and microbial communities respond directly to environmental
stress. Together, these experiments will help identify microbial
communities with distinct effects on plant development, guiding
their selection for future life-history assays.