Tag Archives: seed dispersal

Bad Neighbors

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

The Crux

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.

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Predator Poop Propagating Plant Persistence

Image Credit: Rene Rauschenberger, Pixabay licence, Image Cropped

An omnivorous mesopredator modifies predation of omnivore-dispersed seeds (2021) Bartel & Orrock, Ecosphere, https://doi.org/10.1002/ecs2.3369.

The Crux

The evolution of different methods of seed dispersal has played a huge role in shaping plant diversity and distribution. Earlier plants could only use the water or wind to disperse their offspring, but eventually plants evolved the ability to harness the movement of animals, letting their seeds disperse often further and more efficiently than before.

Seeds are also a vital form of food for many species, including small rodents and insects. Larger animals too, including wild boars, bears, and coyotes who will get stuck into berries when there’s plenty around. This leads to them leaving berry seeds mixed in with their faeces. We might be deterred by the idea of picking dinner out of another animals poop, but many of those rodents and insects don’t mind.

But what about when those faeces are from one of your predators? Do you still want that seed, or should you get the hell out of an area clearly inhabited by a threat to your livelihood? The answers to these questions can determine which seeds get left where, which in turn can determine where plants end up taking root and spreading to. That’s the focus of today’s study.

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