Tag Archives: reproduction

If It Ain’t Broke, Don’t Fix It

Image Credit: Goutham89, CC BY-SA 4.0

The evolution of crocodilian nesting ecology and behavior (2020) Murray et al., Ecology and Evolution, https://doi.org/10.1002/ece3.5859

The Crux

One goal of evolutionary ecology is to understand the links between microevolution and macroevolution, meaning evolution in the short term (multiple generations) and how that scales up to the long term (millions of years). In macroevolution, a group of organisms is thought to be successful if it not only exists for a long period of time, but if it also boasts a large number of species. With those criteria in mind, crocodilians (alligators, crocodiles, gharials, and caimans) are one of the most successful lineages to have ever existed on the planet. Though they may not be the most diverse group of organisms with only 25 species, they have been around for about 100 million years. To put that into perspective, dinosaurs went extinct about 65 million years ago, meaning that the crocodilians not only lived with dinosaurs, but they survived the mass extinction that the dinosaurs didn’t.

This longevity as a lineage raises some questions as to what it is about the crocodilians that made them so successful, when their cousins the dinosaurs died out. An interesting aspect of crocodilians is that there is very little variation among these organisms, as they are all generalist carnivores, live aquatic lives, exhibit mating vocalizations, their sex is determined by the temperature of their eggs (see Did You Know?), and they care for their eggs and young. Despite these similarities, there are some notable differences in the reproductive ecology and behavior of the different species, specifically how they build and care for their nests. Because of these differences, the authors of today’s study asked if variation in how crocodilians reproduce may have been the cause of their success.

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Should We Conserve Hybrids?

Image Credit: Carol M. Highsmith, CC BY 2.0, Image Cropped

The ultimate goal of species conservation is to preserve a species’ existence in the natural world. To effectively do this, we must know the extent of “species” that we want to conserve. That may sound simple, but the concept of hybridisation can blur the lines of where one species begins and another ends beyond recognition.

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Subspecies – Do We Need Them?

Image Credit: billp1969, Pixabay licence, Image Cropped

You might have come across the word “subspecies” when reading about biodiversity, but what does the term actually mean? And do we really need a more precise classification beyond species? There is unfortunately no consensus about this. Ask 5 biologist and you’ll get at least 10 different answers. So let’s have a look at why it’s such a complicated issue.

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Why Warmer Winters Don’t Always Help Geese

Image Credit: MaxPixel, CC0 1.0, Image Cropped

Contrasting consequences of climate change for migratory geese: Predation, density dependence and carryover effects offset benefits of high-arctic warming (2019) Layton-Matthews et al., Global Change BiologyDOI: 10.1111/gcb.14773

The Crux

Most of us know that climate change will bring warmer, shorter winters to most parts of the world. For many species in areas like the Arctic, it would be easy to interpret this as a good thing – plants grow earlier, so animals get more food, right? Naturally it’s never that simple. Many herbivorous species have evolved in sync with climate cycles so that their reproduction peaks when food becomes available. If season start dates change, these species may not be able to change their own cycles in time. Additionally, what happens if populations of their predators suddenly boom?

Today’s authors wanted to know what role a warming climate played in the population fluctuations of migratory barnacle geese (Branta leucopsis).

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How Different is Too Different?

This Peruvian warbling-antbird must walk a fine line between being different enough from its competitors to reproduce successfully, while staying similar enough to be able to recognize and outcompete the same competitors (Image Credit: Hector Bottai, Image Cropped, CC BY-SA 4.0).

Range-wide spatial mapping reveals convergent character displacement
of bird song (2019)
Kirschel et al., Proc B, https://dx.doi.org/10.1098/rspb.2019.0443

The Crux

In nature, many different organisms can be found in a single location, and sometimes those organisms are closely related to one another. When this happens, classical evolutionary theory predicts that these closely related species should differ in some ways, so as to differentiate members of their own species from others and avoid the costs associated with breeding with a mate that will not produce any viable offspring. This is called character displacement, and there are many examples of this in nature where two different species may be very similar when they live in different places (allopatry), but when they live in the same place (sympatry) they will differ in appearance, behavior, or the exact part of the local habitat that they live in (see Niche Partioning below).

A specific form of character displacement, called agonistic character displacement, occurs when traits or behaviors associated with competition differ between closely related species living in the same area. This is thought to reduce the costs of wasting energy on competing with an organism that you don’t really “compete” with. Agonistic character displacement can, however, result in greater similarity of traits when similar species live together, but previous studies in this area have not accounted for other causes of this similarity. Today’s authors wanted to do just that. Read more

Bringing Back the Wolverine

The Swedish government changed tactics at the end of the 20th century, giving incentives to farmers when there were successful wolverine reproductions in their area

The Swedish government changed tactics at the end of the 20th century, giving incentives to farmers when there were successful wolverine reproductions in their area (Image Credit: Vojtěch Zavadil, CC BY-SA 3.0, Image Cropped)

Paying for an Endangered Predator Leads to Population Recovery (2015) Persson et al., Conservation Letters, https://doi.org/10.1111/conl.12171

The Crux

Humans have a long history of driving dangerous predators out of their backyard. Wolves and wolverines have been driven out of different parts of Europe at different points in history at the behest of farmers looking to protect their livelihood, and the Tasmanian Tiger was driven to extinction for the same reason. But with the realisation that these predators bring enormous ecosystem benefits, governments have been searching for ways to bring about co-existence between predators and locals.

This study looks at a scheme introduced by a Swedish government in 1996, where reindeer herders had previously been compensated for any wolverine related losses. The new scheme introduced compensation for successful wolverine reproductions in the area. Persson et al. decided to have a look at how it fared.

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