Inter-disciplinary Examination of Irrigated Taro Farming on Rurutu, Austral Islands: Sustainable Small-Scale Agriculture in Transition
Worldwide small holder farmers represent democratizing principles within their communities, creating employment and reducing poverty. The sustainability of these practices depends upon their environmental impacts, but these culturally managed landscapes remain understudied. With Dr. Puzey in Biology and Dr. Kahn in Anthropology, I am part of a multidisciplinary team to explore the sustainability of irrigated taro (Colocasia esculenta) farming on Rurutu, French Polynesia. Our integrated anthropological and biological analysis will examine if and how Rurutuan farmers developed sustainable farming practices in the pre-European contact, post-contact, and modern periods. We will examine 1) traditional practices over the longue durée to understand how Rurutuan subsistence farmers created anthropogenic agricultural niches, 2) how these niches might be affected by shifts to non-traditional farming practices, and 3) whether Rurutuan taro varieties represent unique “heirloom” strains in island agricultural systems.
The nectar microbiome: an underexplored third partner in plant-pollinator interactions and evolution
The genomic revolution has revealed incredible microbial diversity everywhere. Plants have a suite of bacteria, fungi and viruses that live in and on them – their microbiome – that can be central for plant health and play a critical role in agriculture. For example, nitrogen fixing bacteria inhabit the roots of soybeans, providing nitrogen; mycorrhizal fungi in roots enhances drought tolerance in crops; and fungi that live on leaves can defend against herbivores. Microbes may also play a key role in plant reproduction by affecting nectar chemistry. Nectar chemistry is an important aspect of reproduction for all flowering plants as nectar is a major reward and attractant for pollinators. Although the vast majority of pollinator research has ignored the nectar microbiome, recent studies illustrate its potential to have indirect effects on plant seed production by changing pollinator behavior. However, studies have yet to link the nectar microbiome directly to changes in plant seed production (i.e., fitness).
Our research aims to fill this gap by exploring the potential for a direct link between the nectar microbiome and seed production in Asclepias syriaca, the common milkweed best known as the primary host plant for the iconic monarch butterfly. All milkweeds have a unique floral anatomy and pollination system: pollen is packaged into a structure called a pollinia that is carried on the legs of insect pollinators from one flower to another. Pollinia must be inserted into the correct structure and submerged in nectar in order for pollen tubes to germinate and grow toward the eggs, and thus, produce seeds. Our preliminary experiments demonstrate that the sugar type (glucose, sucrose, fructose) and concentration of that nectar, as well as the presence of microbes, has a large influence on the success and vigor of pollen tube germination. Our ongoing studies in the field and the lab are exploring the effects of insect visitation on nectar microbial composition and the effect of different microbial taxa isolated from nectar.
Clone or flower? – Uncovering the population consequences of clonal and sexual reproduction in plants
Reproduction in plants is uniquely diverse because most species (estimated 80%) are capable of both sexual and clonal reproduction . Sexual reproduction is the only means by which novel gene combinations can arise, producing the genetic diversity necessary for adaptation and evolution. However, producing flowers, attracting pollinators, producing seeds, and then dispersing them is costly for the plant. Clonal reproduction can be accomplished without mates or using resources to attract pollinators, and clones can even share resources if they are physiologically integrated. However, clonal growth may be detrimental if clones compete for resources, or if offspring do not have sufficient genetic variation to maintain population viability. With dual reproductive strategies and differing consequences, understanding how sexual and clonal reproduction coexist is key to population demography, ecology, and evolution. Despite this, biologists regularly downplay or ignore clonal reproduction in population demography and modeling, omitting a major factor in population dynamics. The goal of our work is to fill this gaping hole in our understanding of plant population dynamics: we propose to investigate the roles of both clonal and sexual reproduction for driving the population growth of an important Virginia native plant, Asclepias syriaca, common milkweed. To do this, we are combining field work to map entire milkweed populations, lab work to identify clones using microsatellites, and Integral Projection Models to uncover the population consequences of clonal and sexual reproduction in milkweeds.