Why endemic species?
Trillium decumbens Harb. 2017.
Endemic species are key components of global biodiversity and have been shown to contribute disproportionately to the functional stage of species assemblages and the maintenance of ecosystems. Therefore, understanding the underlying processes affecting endemism and rarity is a critical aspect of ecosystem conservation.
Endemic species play starring roles in conservation planning and are often of particular interest to the public. In addition, endemism is of great interest in the field of rare species biology. Discovering why some species are rare while others are common is central to our understanding of the dynamics of species and communities, and is a fundamental question in ecology.
Endemic species play starring roles in conservation planning and are often of particular interest to the public. In addition, endemism is of great interest in the field of rare species biology. Discovering why some species are rare while others are common is central to our understanding of the dynamics of species and communities, and is a fundamental question in ecology.
Comparisons of seed dispersal effectiveness for sympatric endemic and widespread 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.
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.
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.
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.
species distribution Modeling
Maps illustrating the potentially suitable area predicted by SDM (pink) for a. T. erectum, and b. T. discolor, two species of Trillium native to eastern North America. Areas in green represent the overlap between the known range (delineated with a polygon) and the potentially suitable area.
I test questions about landscape-level processes that impact geographic range sizes using Maxent species distribution modeling (SDM).
SDM 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 the model, we can draw conclusions about the realized vs. fundamental niche, and whether a species' geographic distribution is informed primarily by abiotic, rather than biotic, factors as captured by climate variables. (Manuscript coming soon!)
