Dr. Adler Research Interests

Research Interests

 

There is a growing recognition that the factors determining the distribution and abundance of species, and the evolution of phenotypic traits, can only be understood in the context of multiple interactions.  For example, interactions with antagonists and mutualists have historically been studied independently, although plants are often under simultaneous and potentially conflicting selective pressures exerted by both groups. My research integrates plant-animal interactions across mutualisms and antagonisms, including floral, foliar, and belowground tissues, to arrive at a more complete understanding of how multiple species select on resistance and attractive traits. My approach has combined novel techniques and experimental manipulations in the field with greenhouse and laboratory experiments to dissect aspects of this complex empirical question, and involves studies in both basic and applied systems.

Current and recent projects include:

A. Floral traits mediating disease dynamics

Photo taken by Adler lab

New research is examining the consequences of consuming floral defensive chemicals on parasite loads in Bombus impatiens, the common eastern bumble bee, which is frequently infected by the trypanosome gut pathoge Crithidia bombi. This work is in collaboration with Dr. Becky Irwin (Dartmouth College), Dr. Jay Evans (USDA) and Dr. Phil Stevenson (University of Greenwich and Kew Gardens, UK) and is funded by NSF and USDA. Our initial work found that consumption of a range of secondary compounds significantly reduced pathogen loads (Richardson et al, in review). We used naturally occurring nectar concentrations, and so our work highlights the previously unrecognized importance of nectar chemistry mediating bee-pathogen dynamics. Current research directions include quantifying the frequency and variation in nectar defenses in bee-pollinated wild and agricultural plant species, further understanding the mechanisms by which secondary chemicals reduce pathogen loads, assessing genetic variation in Crithidia sensitivity to secondary compounds, and determining the consequences of pathogen loads and diet on pollination efficiency and yield in crop species.

Photo taken by Scott McArt

Plant diseases are ubiquitous in natural and managed systems. Numerous fungal pathogens infect flowers, causing some of the economically most important plant diseases. Many of the fungal pathogens that infect flowers are vectored by pollinators, but we know surprisingly little about how floral traits mediate interactions with these floral pathogens. Our goal is to determine the traits that influence blueberry infection by the fungus Monilinia vaccinii-corymbosi (mummy berry), which is vectored to flowers by pollinators and is the most important and widespread fungal disease of blueberry in North America. This work has been supported by a USDA postdoctoral fellowship to Dr. Scott McArt, and Lotta Crabtree fellowships to graduate student Matt Boyer. We demonstrated that mummy berry infection causes leaves to emit floral and novel volatiles (McArt and Adler, in prep.), that floral stigma phenolics are correlated with resistance to infection (McArt, Salminen and Adler, in prep.), and that pollinator communities differ with blueberry cultivars (Boyer, McArt, Warren and Adler, in prep.). Our research is shedding new light on how floral traits mediate disease transmission, and providing valuable information on resistance traits that could be used to reduce reliance on fungicides.

B. Floral defenses mediating plant-insect interactions in urban environments

Photo taken by Lynn Adler

The perennial vine Carolina jessamine, or Gelsemium sempervirens, contains alkaloids in all plant parts including corollas and nectar. Dr. Rebecca Irwin of Dartmouth College, Dr. Paige Warren of ECo at UMass-Amherst and I received NSF funding to examine how urbanization changes natural selection on plant attractive and defensive traits via changes in plant-insect interactions. In Raleigh, NC, we found that plants in suburban sites had more floral herbivory, nectar robbing, and heterospecific pollen deposition compared to plants in paired forested sites less than 5 km away (Irwin et al. 2014). We therefore predict that better-defended plants will be selected for in suburban habitats due to greater antagonistic interactions and less beneficial pollinator visits in the suburban compared to forested environment.

In previous work, Dr. Irwin and I examined the consequences of nectar alkaloids for plant fitness via effects on pollinators such as this bumblebee, Bombus bimaculatus, and nectar robbers like the carpenter bee, Xylocopa virginica. We also asked whether traits that make plants attractive to pollinators also make them more susceptible to nectar-robbing, and whether nectar-robbing decreases plant fitness. This research was funded by the National Science Foundation, and has been reviewed in ScienceNow.

 



C. Impacts of herbivory, pollination and integrated pest management in cucurbits

squash

Photo taken by K. Hladun

Several projects in the lab address questions about how herbivores and pollinators interact to affect yield in cultivated cucurbits, and the costs and benefits of phenotypic traits in wild cucurbits. Past and current projects include:

 

Examining how leaf herbivory, root herbivory, mycorrhizae and pollinators interact via a shared host, using cucumber as a model system (L. S. Adler, E. T. Kiers and R. V. Hazzard, USDA NRI, with former postdoc Dr. Nick Barber).

Determining the relative role of pollination and aboveground herbivory by cucumber beetles (Acalymma vittatum) for yield in butternut squash (Cucurbita moschata), and how perimeter trap crops affect yield via interactions with both herbivores and pollinators (L. S. Adler and R. Hazzard, USDA NE-IPM).

Asking how aboveground leaf herbivory and belowground root herbivory by the specialist herbivore, Acalymma vittatum, interact to influence pollination and yield in butternut squash (K. Hladun, funded by the Plant Biology Graduate Program at UMass-Amherst)

Elucidating the fitness costs and benefits of floral scent in Cucurbita texana in the context of attracting pollinators and pollen-feeding herbivores (N. Theis, NSF-DEB)

 

Taken together, these studies focus on the interactive effects of aboveground herbivory, belowground herbivory, floral herbivory, pollination and mycorrhizae on yield in cultivated cucurbits, and on the evolution of resistance and attraction in wild species.

 



D. Correlated defense expression and interactions with pollinating herbivores in Nicotiana 

tobacco flower

Photo taken by L. S. Adler

Genetic correlations between traits, such as the correlated production of defensive compounds in leaves and in nectar, can constrain the ability of plants to evolve optimal solutions to conflicting selection pressures. Furthermore, in many systems herbivores and pollinators are the same species interacting with plants at different points in their life cycle. The genus Nicotiana provides an excellent model system for elucidating how defense trait expression is correlated across leaf and floral tissues, and how interactions with pollinating adults such as Manduca sexta (hawkmoths; tobacco hornworm) feed back to influence subsequent herbivory by larval offspring.

 

 

 

moth

Photo taken by L. Call Gastinger

Nicotiana tabacum and Datura stramonium plants with more or better quality nectar have higher levels of Manduca sexta (tobacco hornworm) oviposition on leaves. If these nectar traits are heritable and if more oviposition leads to plant fitness costs, these results suggest that leaf herbivory may select on the evolution of floral attractive traits.

 


Haustroria

Photo taken by F.M. Adler

A growing number of studies indicate that the expression of attractive and resistance traits are not independent. The expression of nicotine and related alkaloids in nectar and leaves is phenotypically correlated across individual Nicotiana tabacum plants (Adler et al. 2006), and is also correlated across Nicotiana species (Adler et al. 2012). Furthermore, leaf herbivory in N. tabacum induced higher nicotine levels in nectar, indicating that plant-herbivore interactions can alter key traits affecting pollinator preference (Adler et al. 06).