Image credit: Muséum de Toulouse, CC BY-SA 4.0, via Wikimedia Commons
Top-down response to spatial variation in productivity and bottom-up response to temporal variation in productivity in a long-term study of desert ants (2022) Gibb et al., Biology Letters, https://doi.org/10.1098/rsbl.2022.0314
Ecosystem productivity can tell us a lot about how an ecosystem functions. The more productive an ecosystem is, the more life it can support. But productivity doesn’t just affect the diversity or number of species within an ecosystem, it affects how those species interact, from the large carnivores you find at the upper levels, to the plants and bacteria down the ‘bottom’.
Within ecosystems, the strength of a top-down process (something influencing those upper levels) vs. a bottom-up process (something influencing the lower levels) depends on how much primary productivity there is. Primary production occurs when a species makes its own energy instead of eating something else, and when there is a lot of it going around, it often allows the carnivores at the upper trophic levels to suppress the population numbers of herbivores. That means that while a bottom-up process may end up affecting the herbivores, a top-down process (like the hunting of carnivores) might impact the entire ecosystem.
On the other side of the spectrum, when there is little primary productivity, there aren’t usually as many carnivores suppressing the herbivore populations. A bottom-up process will increase herbivore numbers, making these bottom-up processes more important in these low-productivity systems. This is known as the Exploitation Ecosystem Hypothesis (EEH).
Temporally consistent species differences in parasite infection but no evidence for rapid parasite-mediated speciation in Lake Victoria cichlid fish (2020) Gobbin et al., Journal of Evolutionary Biology. https://doi.org/10.1111/jeb.13615
Image Credit: Kevin Bauman, CC BY 1.0
Ecological speciation (see Did You Know?) can be driven by both abiotic (non-living) and biotic (living) factors. The biotic factors that tend to be studied in regards to ecological speciation are antagonistic in nature, such as competition for resources or interactions with predators. However, parasitism is another antagonistic species interaction that is ubiquitous in nature, and therefore might be expected to contribute to ecological speciation via its effects on host-parasite coevolutionary dynamics.
Though a number of studies have investigated the effects of parasites on ecological speciation, little is known about the role of parasites in adaptive radiations, which are bursts of speciation from a single ancestor to many descendent species that then adapt to fill new ecological niches. In other words, an ancestor will be adapted to a specific environment/food types, but its descendants adapt to live in different environments/eat different food. One of the best examples of an adaptive radiation are the Africa lake cichlids, which are the focus of today’s study. The authors wanted to understand if parasites may have contributed to/caused the adaptive radiation seen in African lake cichlids.
Community ecology, as a relatively new discipline, is fraught with challenges. Here, we look at why an hour spent talking about those challenges may make you feel like the PhD student pictured above (Image Credit: Lau Svensson, CC BY 2.0, Image Cropped)
Anyone who has forayed any small distance into academia will probably understand the following quote by Aristotle.
“The more you know, the more you realize you don’t know.”
According to Stewart Lee, participating in further education means embarking on a “quest to enlarge the global storehouse of all human understanding”. This might be true, yet venturing into academia also means that the more answers you learn to challenging scientific questions, the more questions get opened up. It’s the circle of academic life.
When fish like this goby aggregate, the density of their nests can often have a big impact on their success (Image Credit: Laszlo Ilyes, CC BY 2.0, Image Cropped)
Spatial and temporal patterns of nest distribution influence sexual selection in a marine fish (2018) Wong et al.,
Oikos, doi: 10.1111/oik.05058
When we monitor the fluctuations of a population, we often look at vital rates, a huge part of which is reproductive success. The success that males have in siring offspring can be hugely influenced by the density of a population, particularly when it comes to a breeding ground.
Larger males will often outcompete smaller males on such grounds, however in many species these males will often reach reproductive limits, at which point smaller males can benefit. Smaller males may also fare better in less dense populations, where females lack other individuals to compare them to. Our study today looks at variations in reproductive success of a nest-breeding fish species over two levels of density.