Mambelli, S. | Search bioRxiv

bioRxiv2020

Routes to Roots: Direct Evidence of Water Transport by Arbuscular Mycorrhizal Fungi to Host Plants

Arbuscular mycorrhizal fungi (AMF) form symbiotic associations with 80% of surveyed land plant species and are well-recognized for accessing and transferring nutrients to plants1. Yet AMF also perform other essential functions, notably improving plant-water relations2. Some research attributes the role of AMF in plant-water relations solely to enhancing plant nutrition and osmoregulation for plants partnered with AMF3,4,5, while indirect evidence suggests AMF may transport water to plants1,6,7. Here, we used isotopically-labeled water and a fluorescent dye to directly track and quantify water transport by AMF to plants in a greenhouse experiment. We specifically assessed whether AMF can access water in soil unavailable to plants and transport it across an air gap to host plants. Plants grown with AMF that had access to a physically separated 18O-labeled water source transpired twice as much, and this transpired water contained three times as much label compared to plants with AMF with no access to the separated labeled water source. We estimated that water transported by AMF could explain 46.2% of the water transpired. In addition, a fluorescent dye indicated that water was transported via an extracytoplasmic hyphal pathway.

microbiology↗

bioRxiv2019

Stable isotope composition of feathers help track the migratory patterns of Sharp-shinned Hawks (Accipiter striatus) along Western Flyways of North America

The large-scale patterns of movement for the Sharp-shinned Hawk (Accipiter striatus), a small forest hawk found throughout western North America, are largely unknown. However, based on field observations we set out to test the hypothesis that juvenile migratory A. striatus caught along two distinct migration routes on opposite sides of the Sierra Nevada Mountains of North America (Pacific Coast and Intermountain Migratory Flyways) come from geographically different natal populations. We applied stable isotope analysis of hydrogen (H) and oxygen (O) of feathers, and large scale models of spatial isotopic variation (isoscapes) to formulate spatially explicit predictions of the origin of the migrant birds. Novel relationships were assessed between the measured hydrogen and oxygen isotope values of feathers from A. striatus museum specimens of known origin and the isoscape modeled hydrogen and oxygen isotope values of precipitation at those known locations. We used these relationships to predict the origin regions for birds migrating along the two flyways from the measured isotope values of migrants feathers and the associated hydrogen and oxygen isotopic composition of precipitation where these feathers were formed. The birds from the two migration routes had overlap in their natal/breeding origins and did not differentiate into fully separate migratory populations, with birds from the Pacific Coast Migratory Flyway showing broader natal geographic origins then those from the Intermountain Flyway. The methodology based on oxygen isotopes had, in general, less predictive power than the one based on hydrogen. There was broad agreement between the two isotope approaches in the geographic assignment of the origins of birds migrating along the Pacific Coast Flyway, but not for those migrating along the Intermountain Migratory Flyway. These results are discussed in terms of their implications for conservation efforts of A. striatus in western North America, and the use of combined hydrogen and oxygen stable isotope analysis to track the movement of birds of prey on continental scales.

zoology↗