Shrubs frequently have positive interactions with annuals in desert ecosystems. This facilitative effect has been seen repeatedly with plant density, but the effect of shrubs on flowering is less studied. Shrubs also impact other species that interact with annuals, including both herbivores and pollinators. These direct and indirect interactions exist in a complex network that we attempt to tease apart through both manipulation and observation.
Positive interactions are key to many systems worldwide. Foundation species such as shrubs are able to benefit other taxa through various mechanistic pathways. The canopy of these species is also an structural agent, able to reduce light intensity and temperature variation experienced by vertebrates. But, do the instances of animal near a shrub increase as temperature and light intensity increase? Can artificial shelters be as good as shrubs when comes to lowering the variation in the above parameters? Disturbances such as land use and climate change are the current reality of many regions. To be able to artificially restore these systems post-disturbance while new vegetation is grown is thus key.
Positive interactions between plant and animal species have been reported in most ecosystems globally. Most literature that looks at these interactions, particularly in arid ecosystems, reports the facilitative interactions occurring between shrub and animal species. With these types of interactions being present, one begs to question; does the density of these foundational shrub species have a relationship with the animal abundance present near them? That being said, understanding this relationship could potentially be used for remediation efforts, for many of the animal species using these shrubs.
For access to my March 2020 Progress report presentation click here
Positive interactions between plants and animals create habitat infrastructure on which many species rely, especially when the promotion of foundation species is involved. Mutualistic interactions between plants and birds (like pollination or seed dispersal) are dependent on both plant and bird phenology or cyclic/seasonal changes. However, phenology is plastic as photoperiod and temperature largely determine flowering & fruiting for plants and migration & breeding for birds. As our climate changes and habitats degrade, we must understand what interactions are at risk. That’s why, in this study, we examined the relationships between birds, their community, their behavior, and their microhabitat associations.
Follow this link to view my progress report presentation for March 2020, or follow this link to view the slide deck of the presentation.
As a team, we are discussing the fine-scale grain of sampling for estimating annual-annual plant interactions in deserts. We are particularly interested in the Mojave Desert to examine pollinator-herbivore interactions with annuals that are mediated by the other immediately adjacent congeneric species. Here is a brief compilation of key papers examining this challenge.
Publications describing the fine-scale annual plant neighbourhood concept
One of the most powerful approaches for understanding biological invasions by non-native species is to examine ecological patterns and processes in both the native and non-native ranges of invasive species. Here’s a great article on the subject:
The number of articles published on biological invasions has increased exponentially over the last 20 years, but biogeographically explicit studies replicated in the native and non-native ranges of invasive species are still VERY rare. This hampers our mechanistic understanding of the invasion process and therefore our ability to explain, predict, and manage biological invasions.
Bromus rubens (i.e., red brome) invasion in the Mojave Desert provides a great opportunity to address this knowledge gap. We are planning to examine the individual and joint effects of shrub facilitation and post-dispersal seed predation on the abundance of B. rubens in its native (Israel) and non-native (California and Nevada) ranges. This experiment is broadly interesting because it allows us to test the relative importance of the effects of two fundamental biotic interactions on two continents. Here’s a cartoon of our experimental design:
Solid circles represent functional exclosures that effectively exclude seed predators; dashed circles represent non-functional exclosures that admit seed predators. Note the control treatment that monitors recruitment from seed banks. This is a full-factorial design that crosses shrub facilitation (open vs. shrub microsites) with seed predation (functional vs. non-functional exclosures). Pretty cool.
We will replicate this setup at 5 shrub-open pairs per site at 6 sites across the Mojave (GPS coordinates are preliminary):
We will replicate the experiment at 5 sites in the Negev Desert of Israel with the help of Dr. Merav Seifan of the Ben Gurion University of the Negev. She rocks! Site locations and GPS coordinates in Israel are forthcoming.
The biogeographic contrast of the effects of seed predation can be considered a test of the enemy release hypothesis, which has only been examined once in the context of seed predation:
In collaboration with Professor Katie O’Meara, an architect, Professor Zaitchik, an Earth Scientist, and researcher Claire Moriarty, we are examining the use of drones to map keystone species in extreme environments such as cushion plants in Patagonia or shrubs in deserts. This is just a pilot experiment (haha, get it), and we need a graduate student for 2020 to dig in and ground-truth the metrics we will derive from imagery. The focus will be structure and architecture in natural systems.
York Science Fellow Dr. Jacob Lucero and international collaborator Dr Merav Seifan are launching into 2020 with an ambitious experiment in Israel and California. The purpose is to explore the relative importance of provenance of a highly invasive species of bromus in the deserts of California by comparing performance and key interactions in its home range, Israel, and in its introduced range, California. This is a new direction from previous work published in NeoBiota entitled ‘The dark side of facilitation: native shrubs facilitate exotic annuals more strongly than native annuals’ that demonstrated a very significant effect of bromus on local plant community dynamics.