wind disturbances in the southeastern u.s.
Monochamous titillator, a common Cerambycid species in the southeastern U.S.
Wind disturbances such as hurricanes and tornadoes are natural and critical disturbance agents in the southeastern U.S. However, the frequency and intensity of these events is thought to be increasing with climate change.
As a member of the Gandhi Lab at UGA, I focused on the impacts of two specific wind disturbance events on populations and community assembly of subcortical woodboring beetles, which colonize dead and dying trees following bark beetle infestations. These events included Hurricane Michael (2018) in pine forests of Florida and Georgia, and an EF1 tornado in pine forests of southeastern North Carolina (2019).
In these systems, I characterized and quantified community composition of woodboring beetles (Cerambycidae and Buprestidae). Wood-boring beetles (e.g. Longhorned beetles and jewel beetles) play important roles in forest succession, wood decomposition, and pollination, and are a food source for many species of birds and mammals. Most wood-boring beetles pose little economic threat to human activities, but several species, including the Asian longhorn beetle (Anoplophora glabripennis), the southern pine sawyer (Monocamous spp.), and the emerald ash borer (Agrilus planipennis), can severely disrupt natural forest ecosystems and impair ecosystem services. Following a major disturbance event and/or epidemic outbreaks of bark beetles (Curculionidae: Scolytinae), Cerambycids and Buprestids can exacerbate tree mortality and further decrease plantation wood quality.
Although no longer a formal member of the Gandhi Lab, these projects are ongoing.
As a member of the Gandhi Lab at UGA, I focused on the impacts of two specific wind disturbance events on populations and community assembly of subcortical woodboring beetles, which colonize dead and dying trees following bark beetle infestations. These events included Hurricane Michael (2018) in pine forests of Florida and Georgia, and an EF1 tornado in pine forests of southeastern North Carolina (2019).
In these systems, I characterized and quantified community composition of woodboring beetles (Cerambycidae and Buprestidae). Wood-boring beetles (e.g. Longhorned beetles and jewel beetles) play important roles in forest succession, wood decomposition, and pollination, and are a food source for many species of birds and mammals. Most wood-boring beetles pose little economic threat to human activities, but several species, including the Asian longhorn beetle (Anoplophora glabripennis), the southern pine sawyer (Monocamous spp.), and the emerald ash borer (Agrilus planipennis), can severely disrupt natural forest ecosystems and impair ecosystem services. Following a major disturbance event and/or epidemic outbreaks of bark beetles (Curculionidae: Scolytinae), Cerambycids and Buprestids can exacerbate tree mortality and further decrease plantation wood quality.
Although no longer a formal member of the Gandhi Lab, these projects are ongoing.
Comparisons of seed dispersal effectiveness in Trillium congeners
Ants dispersing seeds of Trillium catesbaei Elliot. 2016.
In flowering plants, rarity may be associated with dispersal syndromes. To test this hypothesis, I compared seed dispersal effectiveness (SDE) for co-occurring endemic and common congeners of Trillium, perennial understory herbs found throughout deciduous forests of the southeastern US.
Trilliums are myrmecochores (their seeds are dispersed by leaf litter ants), so I quantified metrics of ant-mediated seed dispersal observed in the field and measured in the laboratory to determine if aspects of SDE differed for endemic-common Trillium species pairs. This work was published in The American Journal of Botany (2018).
Trilliums are myrmecochores (their seeds are dispersed by leaf litter ants), so I quantified metrics of ant-mediated seed dispersal observed in the field and measured in the laboratory to determine if aspects of SDE differed for endemic-common Trillium species pairs. This work was published in The American Journal of Botany (2018).
Seed chemistry and disperser preference
An A. picea worker disperses a seed. 2016.
In ants, preference for food items can be detected through "cafeteria" experiments where two items are offered simultaneously. In myrmecochorous ants (those that disperse seeds), preference is likely shaped by physical and/or chemical attributes of seeds, including weight, length, width, or the ratio of elaiosome (a seed-coat derived appendage) to seed. Chemical cues, particularly oleyl-containing compounds, stimulate ants to carry food items to nests and have been shown to explain ant preference for myrmecochore seeds of low nutritional value. However, nutritional quality likely also impacts ant preference.
To test whether ants display a preference for endemic or widespread Trillium congeners, I performed cafeteria experiments using captive ant colonies. To parse out the underlying mechanisms driving preferences, I used gas- and liquid-chromatography mass spectrometry to characterize seed chemical profiles. This research was published in Ecology & Evolution (2020).
To test whether ants display a preference for endemic or widespread Trillium congeners, I performed cafeteria experiments using captive ant colonies. To parse out the underlying mechanisms driving preferences, I used gas- and liquid-chromatography mass spectrometry to characterize seed chemical profiles. This research was published in Ecology & Evolution (2020).
Ecological niche Modeling (enm)
Miller et al. (2021).
Using a combination of ENM and beta regression models, I tested whether reproductive life history traits relating to biotic factors and seed dispersal explain differences in the proportional occupancy of the fundamental niche for 21 species of Trillium in eastern North America. This work was recently published in Diversity and Distributions.
ENM is a means of approximating the fundamental niche by statistically relating values of climate and remote sensing variables across a species' known range to a larger spatial extent. By comparing the proportional occupancy of the potentially suitable area predicted by ENM, we can draw conclusions about the realized vs. fundamental niche, and whether a species' geographic distribution is informed primarily by abiotic factors, or by a combination of abiotic and biotic factors.
We found that Trillium species' occupancy of their predicted suitable range can be explained by flower type and other reproductive life history traits, indicating that biotic and dispersal factors play a large role in determining the geographic distributions of these species.
ENM is a means of approximating the fundamental niche by statistically relating values of climate and remote sensing variables across a species' known range to a larger spatial extent. By comparing the proportional occupancy of the potentially suitable area predicted by ENM, we can draw conclusions about the realized vs. fundamental niche, and whether a species' geographic distribution is informed primarily by abiotic factors, or by a combination of abiotic and biotic factors.
We found that Trillium species' occupancy of their predicted suitable range can be explained by flower type and other reproductive life history traits, indicating that biotic and dispersal factors play a large role in determining the geographic distributions of these species.
