The disruption of a keystone interaction erodes pollination and seed dispersal networks, Vitali et al., 2021 Ecology. https://doi.org/10.1002/ecy.3547
Image credit: Ennio Nasi, CC BY 4.0
Ecological communities are incredibly complex networks, made up of interactions between the species that reside in them. To properly understand how these interactions shape a community, researchers have to employ a variety of analytical methods and modelling approaches. This was something that I had to learn to appreciate in my work, because I always thought that studying ecology would involve a lot of time outdoors working with animals. While that does happen (and I spent months outside during my PhD), most of the ecological research I’m familiar with centers on math and statistics.
Using math and statistics to model ecological communities helps us to break down how various organisms are connected with one another. For example, keystone species are organisms that are connected to so many others within a given ecosystem such that any change to their populations will have consequences for the entire community. Understanding the processes that affect these keystone individuals (and all of the organisms linked to them) is vital to predicting how processes such as climate change and invasive species will affect natural communities in the future.
Today’s authors investigated how disruption of an important species interaction affected pollination and seed dispersal networks in Patagonia. A hummingbird species (Sephanoides sephaniodes) is the main pollinator for a mistletoe species (Tristerix corym-bosus), while the mistletoe provides the hummingbird with nectar in the winter. The colocolo opossum (Dromiciops gliroides) is a small marsupial that is vital for the mistletoe, as mistletoe seeds must pass through the opossum’s gut to trigger their germination. Additionally, the opossums defecate many seeds on branches in a “necklace” arrangement, which likely helps the mistletoe to parasitize their plant hosts. These three species are tightly connected to one another, and any reduction in abundance for one species may affect the other two, and even destroy the entire food web.
Species interactions have predictable impacts on diversification (2021) Zeng and Wiens, Ecology Letters. https://doi.org/10.1111/ele.13635
Image Credit: MacNeil Lyons/NPS, CC BY 2.0
No organism on the planet lives in complete isolation from other organisms. Many organisms serve as a food source for others, and even apex predators have to compete for their food. Species interactions like predation, competition, and parasitism directly impact organisms in their daily lives, but there is also a possibility that these same species interactions have had an impact on much longer timescales. That is, species interactions may have had a direct effect on the diversity of life on our planet.
Species interactions have been previously shown to affect diversification rates (see Did You Know?), so the question that today’s authors asked was whether there is a general trend to the effects of species interactions on diversification rates? Specifically, do species interactions with negative fitness (such as being killed by a predator) impacts decrease diversification rates, and do species interactions with positive fitness (such as successfully parasitizing a host) impacts increase diversification rates?
Evolution and maintenance of microbe-mediated protection under occasional pathogen infection (2020) Kloock et al., Ecology and Evolution, https://doi.org/10.1002/ece3.6555
Image Credit: Zeynep F. Altun, CC BY-SA 2.5, Image Cropped
Microbes are everywhere in nature, and I don’t just mean out in the wild. They live inside of every plant and animal, including humans. These microbes can be harmful, beneficial, or do nothing to their hosts. When they help us, microbes take part in what’s called “defensive mutualism”, which is where they help their hosts fight off parasites. Benefiting from this mutualistic relationship depends on whether or not there are parasites around to defend against, as microbial defense mechanisms can harm not only the parasite but also the host itself.
For this symbiotic relationship to continue and not be selected against over time, the benefits of hosting the microbe must outweigh the costs. This is all well and good when there are always a lot of parasites to defend against, but that is not always the case. Today’s authors wanted to test how changes in parasite pressure over time affected the relationship between a defensive microbe and its host.
Image Credit: Pete, CC BY-NC 2.0
Increased reproductive success through parasitoid release at a range margin: Implications for range shifts induced by climate change (2020) MacKay, Gross, & Ryder, Journal of Biogeography, https://doi.org/10.1111/jbi.13795
Predicting the response of organisms to climate change is a challenge for ecologists and wildlife managers alike. Fortunately, some responses are common enough that it is still possible to make fairly accurate predictions about them without too much information. One common response is that of the range shift, whereby a population of organisms facing some alteration (eg. climate change) in their current habitat, making it unfavorable, begin to move to another location. This allows them to track favorable environmental conditions and possibly mitigate any negative effects of climate change.
Sounds easy, right? Just pack it all up and move when things get hard? Well, for some organisms it may be that simple (looking at you, birds), but for others (like trees) it is significantly harder to do so. Trees (and other plants) are limited in that they depend on other organisms or things like wind to help disperse their seeds. Making things even more difficult are plant species that depend on specific pollinators, and in order for a successful range shift to happen trees AND their pollinators have to make the move. Today’s authors wanted to study how relationships between trees and their pollinators changed at the leading edge of a range shift, allowing them to understand how and why trees succeed during a range shift.