Category Archives: Paper of the Week

Bigger is Not Better

Not all GPS coordinate data are created equal, and some of it may actually be meaningless. (Image Credit: Daniel Johansson, CC BY-NC 2.0)

The smartphone fallacy – when spatial data are reported at spatial scales finer than the organisms themselves (2018) Meiri, S., Frontiers of Biogeography, DOI: https://escholarship.org/uc/item/2n3349jg

The Crux

One of the greatest annoyances when using museum specimens, old datasets, or large occurrence databases (such as GBIF) is when the locality of an occurrence is only vaguely described, and the coordinate uncertainty is high; “Norway” or “Indochina” doesn’t really tell you much about where that specific animal or plant was seen. Luckily, the days where such vague descriptions were the best you could get are long gone, as most of us now walk around with a GPS in our pockets, and even community science data can be reported very accurately, and more or less in real-time.

However, we have now encountered the opposite problem: the reported coordinates of organisms are often too precise to be realistic, and in the worst-case scenario, they might be borderline meaningless. The author of this study wanted to highlight how this advance in technology coupled with our eagerness to get more accurate data and results have made us too bold in our positional claims.

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Populations Can’t Grow without Homes

Sea otters are one of many charismatic species found along the California coast, yet recovery doesn’t seem to be helping them. Is it something about their habitat that is preventing population growth? (Image Credit: “Mike” Michael L. Baird, CC BY 2.0)

Gaps in kelp cover may threaten the recovery of California sea otters  (2018) Nicholson et al., Ecography, DOI:10.1111/ecog.03561

The Crux

In the 18th and 19th centuries, the fur trade was a massive industry in North America. As a result, many species were hunted and trapped to near extinction. The California sea otter (Enhydra lutris) was reduced in population to less than 50 total individuals. The enactment of the Internation Fur Treaty allowed the species (and others) to come back from the brink of extinction, and they now number over 3200 individuals and are spread across 525km of the California coast. Interestingly, although the population is recovering, it has not bounced back as quickly as other protected mammals living in the same habitat. The California sea lion, for example, has a maximum population growth rate more than twice that of the sea otter (11.7% compared to 5%).

Despite the remarkable recovery of the species, the sea otters occupy less than a quarter of their historic range and have not expanded along the coast in 20 years. The authors of this paper wanted to investigate what it is about the sea otters and their habitat that is slowing this population’s growth rate and spread along the coast.

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Dingoes May Not Be the Answer to Australia’s Cat Problem

Dingoes are Australia’s largest native predator. but are they capable of suppressing feral cat populations? (Image Credit: Bernard Dupont, CC BY-SA 2.0)

Diet of dingoes and cats in Central Australia: does trophic competition underpin a rare mammal refuge? (2018) McDonald et al., Journal of Mammalogy, DOI:10.1093/jmammal/gyy083

The Crux

Feral cats are a huge problem for wildlife in plenty of continents. However, there’s nowhere they have had quite so severe an effect as in Australia. Mammals between 50g and five kilos have seen huge reductions in numbers, and many species have gone extinct. Yet there are some areas in Australia which appear to present refuges for native mammals, so it’s crucial to understand the mechanisms behind these areas.

The MacDonnell Ranges in South Australia are home to large dingo populations, which prey on the local kangaroo species. Dingoes can also suppress cat populations through direct predation. The purpose of this paper was to investigate to what degree dingo and cat diets overlap, to see whether the presence of dingoes contributes to the formation of a refugee for native mammals.

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If You Can’t Stand the Heat, Get Out of the Pond

Dragonflies like this Western Pondhawk female are particularly vulnerable to warming due to climate change. (Image Credit: Eugene Zelenko, CC BY-SA 4.0)
Simulated climate change increases larval mortality, alters phenology, and affects flight morphology of a dragonfly (2018) McCauley et al., Ecosphere, doi:10.1002/ecs2.2151

The Crux

Climate change is something that we hear about on a daily basis. The dire warnings tend to concern sea levels rising and temperatures varying so much that we have more intense and deadly storms than before, but these are all direct effects of the climate. Another thing that climate change can do is have indirect effects on organisms.

Organisms with complex life cycles spend the juvenile part of their lives in one environment before moving on to the adult stage in another environment. The researchers in this study wanted to know how simulated climate change during the juvenile stage of the organisms lifetime could affect the adult stage.

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Victory May Not Guarantee Survival in Species Conflicts

Spreading of the Australian yabby has led to decreases in other local species. But what happens when these species meet?
Spreading of the Australian yabby has led to decreases in other local species. But what happens when these species meet? (Image Credit: Daiju Azuma, CC BY-SA 2.5)
Insight into invasion: Interactions between a critically endangered and invasive cray fish (2018) Lopez et al., Austral Ecology, doi:10.1111/aec.12654

The Crux

When we talk about invasive species, often the first thing that pops into our minds are things like feral cats, wild pigs, vicious newcomers that wipe out species or transform vast areas. But often what we focus on less are species which arrive and simply outcompete the locals.

The yabby (Cherax destructor) is one such invader. An Australian species, it has been introduced to new waterways through the country and is now threatening other species, including the Falls Spiny Crayfish (Euastacus dharawalus) in eastern New South Wales, Australia. The introduction of the yabby has resulted in a decreasing habitat range for the crayfish, but what sort of mechanisms are causing this? This experiment aimed to document interactions between the two species.

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Battle of the Sexes

If male and female predators like this newt hunt in different places, they may have different effects on prey communities. (Image Credit: Dave Huth, CC BY 2.0)
Sexual dimorphism in a top predator (Notophthalmus viridescens) drives aquatic prey community assembly (2018) Start & De Lisle, Proceedings B, doi:10.1098/rspb.2018.1717

The Crux

Ecology is a scientific discipline focused on the interactions between the biotic (living) and abiotic (non-living) parts of the environment, and within ecology the subdiscipline of community ecology focuses on how these biotic and abiotic parts interact to determine what species live where. When researchers investigate these relationships, they tend to only consider differences between species, instead of differences within a single species. This means that we are missing a big part of the picture, as differences within a single species can outnumber those between multiple species.

One of the most common differences within a species are those between males and females. Depending on the species in question, one sex can be bigger, eat more, live longer, or eat different things, and this can have an effect on the community that the species in question lives in. Despite these many differences between the sexes, there weren’t any direct empirical examples in the scientific literature of these differences affecting community dynamics. The authors of this paper were the first to use an experiment to investigate this phenomenon, using the red-spotted newt (Notophthalmus viridescens), which is an important predator in aquatic communities.

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Too Many Fish on the Sea Floor

When fish like this sand goby aggregate, the density of their nests can often have a big impact on their success
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)
Spatial and temporal patterns of nest distribution influence sexual selection in a marine fish (2018) Wong et al., Oikos, doi: 10.1111/oik.05058

The Crux

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.

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