Category Archives: Ecology

Going a long way with your mouth open to new tastes

by Piter Kehoma Boll

Everybody knows that human activities have driven our environment toward an unfortunate situation. The most popular forms of human impact include pollution, deforestation and overexploitation of natural resources, but certainly an important factor in remodeling ecosystems is the invasion of species.

While humans move around the world, they carry many species with them, either intentionally or not, an some of them establish successfully in the new environment, while others do not. But what makes some species become successful invaders while other are unable to do so?

It is clear for some time that having a broad niche, i.e., a broad tolerance in environmental conditions and a broad use of resources is very important to succeed in invading a new habitat. Food niche breadth, i.e., the amount of different food types one can ingest, is among the most important dimensions of the niche influencing the spread of a species.

I myself studied the food niche breadth of six Neotropical land planarians in my master’s thesis (see references below) and it was clear that the species with the broader niche are more likely to become invasive. Actually, the one with the broadest food niche, Obama nungara, is already an invader in Europe, as I already discussed here.

obama_marmorata_7

A specimen of Obama nungara from Southern Brazil that I used in my research. Photo by myself, Piter Kehoma Boll.*

But O. nungara has a broad food niche in its native range, which includes southern Brazil, and likely reflected this breadth in Europe. But could a species that has a narrow food niche in its native range broaden it in a new environment?

A recent study by Courant et al. (see references) investigated the diet of the African clawed frog, Xenopus laevis, that is an invasive species in many parts of the world. They compared its diet in its native range in South Africa whith that in several populations in other countries (United States, Wales, Chile, Portugal and France).

Xenopus_laevis

The African clawed frog Xenopus laevis. Photo by Brian Gratwicke.**

The results indicated that X. laevis has a considerable broad niche in both its native and non-native ranges, but the diet in Portugal showed a greater shift compared to that in other areas, which indicates a great ability to adapt to new situations. In fact, the population from Portugal lives in running water, while in all other places this species prefers still water.

We can conclude that part of the success of the African clawed frog when invading new habitats is linked to its ability to try new tastes, broadening its food niche beyond that from its original populations. The situation in Portugal, including a different environment and a different diet, may also be the result of an increased selective pressure and perhaps the chances are that this population will change into a new species sooner than the others.

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References:
Boll PK & Leal-Zanchet AM (2016). Preference for different prey allows the coexistence of several land planarians in areas of the Atlantic Forest. Zoology 119: 162–168.

Courant J, Vogt S, Marques R, Measey J, Secondi J, Rebelo R, Villiers AD, Ihlow F, Busschere CD, Backeljau T, Rödder D, & Herrel A (2017). Are invasive populations characterized by a broader diet than native populations? PeerJ 5: e3250.

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The warmer the dangerouser, at least if you are a caterpillar

by Piter Kehoma Boll

Scientist all over the world agree that species diversity is higher at the tropics than at polar regions, i.e., the closer you get to the equator, more species you will find. But apart from making food webs more entangled, does it increase the overall number of interactions that species experience? Afterall, despite the increase in species richness, the population size usually decreases. For example, while there are hundreds of different tree species in the Amazon forest, the number of individuals of each species is much lower than the number of individuals of a species in a temperate forest in Europe.

In order to test whether an increase in species richness would also mean an increase in biotic interactions, a group of ecologists all over the world engaged in a worldwide experiment using nothing else but small fake caterpillars made of plasticine. The small models were placed in different areas from the polar regions to the equatorial regions and the number of attacks that they suffered were counted and grouped according to the type of predator, which was usually identifiable based on the marks left on the models.

170518143812_1_900x600

A fake caterpillar in Tai Po Kau, Hong Kong. Photo by Chung Yun Tak, extracted from ScienceDaily.

The results indicate that there is indeed an increase in predation rates towards the equator, as well as towards the sea level. Areas close to the poles or at high elevations have a smaller number of interactions. But even more interesting was the revelation that this change is really driven by small predators, especially arthropods such as ants. The rate of attacks by birds and mammals was fairly constant across the globe.

Such an evidence on the importance of arthropod predators at the tropics may make us reevaluate our ideas on the evolution of species in such places, as the main concern for small herbivores such as caterpillars in tropical forests may not be birds, but ants. And this means a completely different way to evolve defense strategies.

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ResearchBlogging.orgReference:

Roslin, T., Hardwick, B., Novotny, V., Petry, W., Andrew, N., Asmus, A., Barrio, I., Basset, Y., Boesing, A., Bonebrake, T., Cameron, E., Dáttilo, W., Donoso, D., Drozd, P., Gray, C., Hik, D., Hill, S., Hopkins, T., Huang, S., Koane, B., Laird-Hopkins, B., Laukkanen, L., Lewis, O., Milne, S., Mwesige, I., Nakamura, A., Nell, C., Nichols, E., Prokurat, A., Sam, K., Schmidt, N., Slade, A., Slade, V., Suchanková, A., Teder, T., van Nouhuys, S., Vandvik, V., Weissflog, A., Zhukovich, V., & Slade, E. (2017). Higher predation risk for insect prey at low latitudes and elevations Science, 356 (6339), 742-744 DOI: 10.1126/science.aaj1631

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Obama invades Europe: “Yes, we can!”

ResearchBlogging.orgby Piter Kehoma Boll

This information was known by me and some other people for quite a while, but only recently has caught attention of the general public. Obama is the newest threat in Europe.

No, I’m not talking about the president of the United States. I’m talking about a land flatworm whose name is  Obama nungara.

obama_marmorata_7

This is the magnificent Obama nungara. This specimen is from Brazil and looks particulary yellowish due to the strong light of the camera flash. Photo by Piter Kehoma Boll.*

It has been a while since a new invasive land flatworm started to appear in gardens of Europe, especially in Spain and France and eventually elsewhere, such as in the United Kingdom. It was quickly identified as being a Neotropical land planarian and posteriorly as belonging to the genus Obama, whose name has nothing to do with Barack Obama, but is rather a combination of the Tupi words oba (leaf) and ma (animal) as a reference to the worm’s shape.

obama_nungara

When you find Obama nungara in your garden, it will look much darker, like this one found in the UK. Photo by buglife.org.uk

At first it was thought that the planarian belonged to the species Obama marmorata, a species that is native from southern Brazil, but molecular and morphological analyses revealed it to be a new species. Actually, much of what was called Obama marmorata in Brazil was this new species. Thus, it was named nungara, which means “similar” in Tupi, due to its similarity with Obama marmorata.

obama_marmorata

This is Obama marmorata, the species that O. nungara was originally mistaken for. Photo by Fernando Carbayo.**

Measuring about 5 cm in length, sometimes a little more or a little less, O. nungara is currently known to feed on earthworms, snails, slugs and even other land planarians. Its impact on the European fauna is, however, still unknown, but the British charitable organization Buglife decided to spread an alert and many news websites seem to have loved the flatworm’s name and suddenly a flatworm is becoming famous.

Who said flatworms cannot be under the spotlight? Yes, they can!

See also: The Ladislau’s flatworm, a cousin of Obama nungara.

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References:

Álvarez-Presas, M., Mateos, E., Tudó, À., Jones, H., & Riutort, M. (2014). Diversity of introduced terrestrial flatworms in the Iberian Peninsula: a cautionary tale PeerJ, 2 DOI: 10.7717/peerj.430

Boll, P., & Leal-Zanchet, A. (2016). Preference for different prey allows the coexistence of several land planarians in areas of the Atlantic Forest Zoology, 119 (3), 162-168 DOI: 10.1016/j.zool.2016.04.002

Carbayo, F., Álvarez-Presas, M., Jones, H., & Riutort, M. (2016). The true identity of Obama (Platyhelminthes: Geoplanidae) flatworm spreading across Europe Zoological Journal of the Linnean Society, 177 (1), 5-28 DOI: 10.1111/zoj.12358

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Friday Fellow: Elegant sunburst lichen

by Piter Kehoma Boll

Bipolar and Alpine in distribution, occurring in both Arctic and Antarctic regions, as well as on the Alps and nearby temperate areas, the elegant sunburst lichen (Xanthoria elegans) is a beautiful and interesting creature. As all lichens, it is formed by a fungus associated with an alga.

An elegant sunburst lichen growing on a rock in the Alps. Photo by flickr user Björn S...*

An elegant sunburst lichen growing on a rock in the Alps. Photo by flickr user Björn S…*

The elegant sunburst lichen grows on rocks and usually has a circular form and a red or orange color. Growing very slowly, at a rate of about 0.5 mm per year, they are useful to estimate the age of a rock face by a technique called lichenometry. By knowing the growth rate of a lichen, one can assume the lichen’s age by its diameter and so determine the minimal time that the rock has ben exposed, as a lichen cannot grow on a rock if it is not there yet, right? This growth rate is not that regular among all populations. Lichens growing closer to the poles usually grow quickly because they seem to have higher metabolic rates to help them survive in the colder climates.

Beside its use to determine the age of a rock surface, the elegant sunburst lichen is a model organism in experiments related to resistance to the extreme environments of outer space. It has showed the ability to survive and recover from exposures to vacuum, UV radiation, cosmic rays and varying temperatures for as long as 18 months!

Maybe when we finally reach a new inhabitable planet, we will find out that the elegant sunburst lichen had arrived centuries before us!

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References:

Murtagh, G. J.; Dyer, P. S.; Furneaux, P. A.; Critteden, P. D. 2002. Molecular and physiological diversity in the bipolar lichen-forming fungus Xanthoria elegans. Mycological Research, 106(11): 1277–1286. DOI: 10.1017/S0953756202006615

Wikipedia. Xanthoria elegans. Available at: < https://en.wikipedia.org/wiki/Xanthoria_elegans >. Access on June 30, 2016.

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Biological fight: Should we bring mammoths back?

by Piter Kehoma Boll

Everybody knows the amazing large animals that are found in Africa and Southeast Asia. Elephants, giraffes, rhinos, hippos, horses, lions, tigers… such large creatures, mostly mammals, are usually called megafauna, the “large fauna”.

Mammals as big as the African bush elephant once roamed the Americas. Photo by flickr user nickmandel2006*.

Mammals as big as the African bush elephant once roamed the Americas. Photo by flickr user nickmandel2006*.

The Americas once had an astonishing megafauna too, full of mastodons, mammoths, giant sloths, giant armadillos and sabertooth tigers. Nowadays it is restricted to some bears and jaguars. What happened to the rest of them? Well, most went extinct at the end of the Pleistocene, around 11,ooo years ago.

South America once had mammals as big as an African bush elephant. Picture by Dmitry Bogdanov** (dibgd.deviantart.com)

South America once had mammals as big as an African bush elephant, such as the giant sloth. Picture by Dmitry Bogdanov** (dibgd.deviantart.com)

As humans already inhabited the Americas by this time, it was always speculated if humans had something to do with their extinction. It is true that nowadays hundreds, thousands of species are endangered due to human activities, so it is easy to think that humans are the best explanation for their extinction, but 10 thousands years ago the number of humans on the planet was thousands of times smaller than today and our technology was still very primitive, so it is unlikely that we could hunt a species to extinction by that period… if we were working alone.

No, I’m not talking about humans cooperating with aliens! Our sidekick was the famous climate change. Periods of extreme warming during the pleistocene seem to have had a strong impact on the populations of many large mammals and, with the aid of humans hunting them down and spreading like an invasive species, the poor giants perished.

Le Mammouth by Paul Jamin

Le Mammouth by Paul Jamin

This happened more than 10 thousand years ago, TEN THOUSAND YEARS.

In Africa, elephants and large carnivores are well known for their importance in structuring communities, especially due to their trophic interactions that shape other populations. The extinct American megafauna most likely had the same impact on the ecosystem. As a result, suggestions to restore this extinct megafauna has been proposed, either by cloning some of the extinct species or, more plausibly, by introduced extant species with a similar ecological role.

Svenning et al. (2015) review the subject and argue in favor of the reintroduction of megafauna to restore ecological roles lost in the Pleistocene, an idea called “Pleistocene rewilding” or “trophic rewilding”, as they prefer. They present some maps showing the current distribution of large mammals and their historical distribution in the Pleistocene, which they call “natural”. They also propose some species to be introduced to substitute the ones extinct, including replacements for species extinct as long as 30 thousand years ago. Now is this a good idea? They think it is and one of the examples used is the reintroduction of wolves in the Yellowstone National Park. But wolves were not extinct for millenia there, neither are they a different species that would replace the role of an extinct one.

A wolf pack in Yellowstone National Park

A wolf pack in Yellowstone National Park

Rubenstein & Rubenstein (2016) criticized the idea, arguing that we should focus on protecting the remaining ecosystems and not trying to restore those that were corrupted thousands of years ago. They also argue that using similar species may have unintended consequences. Svenning et al. answered that this is mere opinion and that a systematic research program on trophic rewilding should be developed. The reintroduction of horses in the New World and its non-catastrophic consequences is another point used to respond to the critiques.

So what’s your opinion? Should we bring mammoths, mastodonts, giant sloths and sabertooth tigers back? Should we introduce elephants and lions in the Americas to play the role that mastodonts and smilodonts had?

My opinion is no. The idea may seem beautiful, but I think it is actually fantastic, too fabulous and sensational. Horses may have come back to the Americas without bringing destruction, but we cannot be sure with anything, even with several theoretical and small-scale studies. We all know how often introducing species goes wrong, very wrong. Look at poor Australia and Hawaii, for instance. Furthermore, those giant mammals went extinct TEN THOUSAND YEARS AGO. Certainly ecosystems have adapted to their extinction. Life always finds a way. There are worse threats to those ecosystems to be addressed, such as their eminent destruction to build more cities and raise more cattle and crops.

Get over it. Mammoths are gone. Let’s try to save the elephants instead, but without bringing them to the Brazilian cerrado. They don’t belong there. They belong in the African savannah.

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References:

Rubenstein, D. R.; Rubenstein, D. I. From Pleistocene to trophic rewilding: A wolf in sheep’s clothing. PNAS, 113(1): E1. DOI: 10.1073/pnas.1521757113

Svenning, J-C.; Pedersen, P. B. M.; Donlan, C. J.; Ejrnæs, R.; Faurby, S.; Galetti, M.; Hansen, D. M.; Sandel, B.; Sandom, C. J.; Terborgh, J. W.; Vera, F. W. M. 2016. Science for a wilder Anthropocene: Synthesis and future directions for trophic rewilding research. PNAS, 113(4): 898-906. DOI: 10.1073/pnas.150255611

Svenning, J-C.; Pedersen, P. B. M.; Donlan, C. J.; Ejrnæs, R.; Faurby, S.; Galetti, M.; Hansen, D. M.; Sandel, B.; Sandom, C. J.; Terborgh, J. W.; Vera, F. W. M. 2016. Time to move on from ideological debates on rewilding. PNAS, 113(1): E2-E3. DOI: 10.1073/pnas.1521891113

Wade, L. 2016. Giant jaguars, colossal bears done in by deadly combo of humans and heat. Science News. DOI: 10.1126/science.aag0623

Wade, L. 2016. Humans spread through South America like an invasive species. Science News. DOI: 10.1126/science.aaf9881

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Friday Fellow: Blue whale

by Piter Kehoma Boll

We’ve talked about the cutest and the leggiest, so now it’s time to introduce the largest, at once.

I think most of us know already that the largest animal ever is our beloved blue whale, Balaenoptera musculus. It can reach 30 m in length and weigh more than 180 tonnes. It’s really big, but probably not as big as many people think. There are some popular legends, like that the heart of a blue whale is the saze of a car or that a human could swim inside its aorta, which are not actually true.

It's almost impossible to find a good photo of the entire body of a blue whale. Afterall, it's huge and lives underwater!

It’s almost impossible to find a good photo of the entire body of a blue whale. Afterall, it’s huge and lives underwater!

But what else can we say about the blue whale? It is a rorqual, a name used to designate whales in the family Balaenopteridae and, as all of them, its main and almost exclusive food is krill, a small crustacean very abundant in all oceans. And krill needs to be abundant in order to provide the thousands of tonnes that all whales in the oceans need to eat every day. A single blue whale eats up to 40 million krill in a day, which equals to roughly 3.5 tonnes. A blue whale calf (young) is born measuring around 7 m in length and drinks around 500 liters of milk per day!

Blue whales were abundant in nearly all oceans until the beginning of the 20th century, when they started to be hunted and were almost extinct. Nowadays, the real population size is hard to estimate, but may encompass as few as 5,000 specimens, much less than the estimated hundreds of thousands in the 19th century. Due to such a drastic reduction in the population, the blue whale is currently listed as “endangered” in IUCN’s Red List.

But let's see a blue whale in all of its blueness.

But let’s see a blue whale in all of its blueness.

Occasionally, blue whales can hybridize with fin whales (Balaenoptera physalus) and perhaps even with humpback whales (Megaptera novaeangliae), a species classified in a different genus! Some recent genetic analyses, however, indicate that the Balaenoptera genus is polyphyletic and the blue whale may become known as Rorqualus musculus.

Different from other whales, blue whales usually live alone or in pairs, but never form groups, even though they may sometimes gather in places with high concentrations of food.

Like other cetaceans, especially other baleen whales, the blue whale sings. The song, however, is not as complex and dynamic as the ones produced by the related humpback whale. An intriguing fact that was recently discovered is that the frequency of the blue whale song is getting lower and lower at least since the 1960s. There is no good hypothesis to explain this phenomenon yet, but several ones have been proposed, such as the increase in background noise due to human activities or the increase in population density due to the decrease in whaling.

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References:

Hassanin, A.; Delsuc, F.; Ropiquet, A.; Hammer, C.; van Vuuren, B. J.; Matthee, C.; Ruiz-Garcia, M.; Catzeflis, F.; Areskoug, V.; Nguyen, T. T.; Couloux, A. 2012. Patter and timing of diversification of Cetartiodactyla (Mammalia, Laurasiatheria), as revealed by a comprehensive analysis of mitochondrial genomes.  Comptes Rendus Biologies, 335: 32-50.

Mellinger, D. K.; Clark, C. W. 2003. Blue whale (Balaenoptera musculus) sounds from the North Atlantic. Journal of the Acoustical Society of America, 114(2): 1108-1119.

Wikipedia. Blue whale. Available at: <https://en.wikipedia.org/wiki/Blue_whale&gt;. Access on January 27, 2016.

 

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The tegu lizard and the origin of warm-blooded animals

ResearchBlogging.org by Piter Kehoma Boll

Warm blood is the popular way to refer to endothermy, the ability that certain animals have to maintain a high body temperature by the use of heat generated via metabolism, especially in internal organs. Mammals and birds are the only extant groups in which all representatives are endothermic, but some fish also have this feature.

Tunna fish are truly endoothermic fish, similar to mammals and birds.

Tunna fish are truly endothermic fish, similar to mammals and birds. Photo by opencage.info**

In order to maintain a high body temperature, endothermic animals need a much higher amount of daily food than ectothermic animals (the ones that rely on environmental sources to adjust their body heat). There must be, therefore, a considerable advantage in endothermy to explain such a increased consumption of resources. The advantages include the ability to remain active in areas of low temperature and an increase in efficienty of enzimatic reactions, muscle contractions and molecular transmission across synapses.

The origin of endothermy is still a matter of debate and several hypothesis have been erected. The main ones are:

1. A migration from ectothermy to inertial homeothermy and finally endothermy.

According to this hypothesis, animals that were initially ectothermic grew in size, becoming inertially homeothermic, i.e., they retained a considerable constant internal body temperature due to the reduced surface area in relation to the their volume. Lately, selective pressures forced those animals to reduce in size, which made them unable to sustain a constant internal temperature and therefore their enzimatic, muscular and synaptic efficiency became threatened. As a result, they were forced to develop an alternative way to maintain a high body temperature and acquired it through endothermy.

Initially considered a plausible explanation due to the body size of the ancestors of mammals in fossil record, new phylogenetic interpretations caused a complete mix of large-bodied and small-bodied animals, so that currently fossils don’t support this idea anymore.

2. A large brain heating the body

The brain in endothermic species produces much more heat than any other organs. This led to the assumption that maybe a large brain generating heat was the responsible for the later development of full endothermy. However, evidence from both exant and extinct species point to the opposite. It seems more reasonable that a large brain evolved after endothermy and not the opposite.

3. A nocturnal life needs more heat

This idea states that the development of endothermy happened as a way to allow animals to be active during the night. The fact that most primitive mammals appear to have been nocturnal seems to support this hypothesis, but in fact many extant nocturnal mammals actually have a lower body temperature than diurnal mammals. Other aspect that counts against this hypothesis is that the ancestors of mammals already showed evidences of an increase in body temperature despite the fact that they most likely were not nocturnal.

4. Heat to help the embryos to develop

As you may know, in many ectothermic vertebrates, such as reptiles, eggs need to be incubated at a constant temperature in order to develop adequately. Endothermy, therefore, could have evolved as a way to allow parents to incubate the eggs themselves and have a higher control on temperature stability. One fact that support this theory is the dual role of thyroid hormones in reproduction and in the control of metabolic rate.

Endothermy may have evolved to incubate eggs at a constant temperature.

Endothermy may have evolved to incubate eggs at a constant temperature. Photo by Bruce Tuten**

5. Aerobic capicity leading to the heating of internal organs

According to this hypothesis, endothermy evolved after the increase of aerobic capacity, i.e., the first thing to happen was to increase the ability of muscles to consume oxygen in order to release energy, which helped the animal to move faster, among other things. This increased aerobic capicity was attained by increasing the number of mitochondria in muscle cells, which led to higher body temperature in the muscules and consequently a higher visceral temperature. Despite fossils indicating that mammal ancestors developed morphological adaptations indicating increased aerobic capacity, it is not possible to afirm that endothermy was not already present in those species.

Very recently, it has been found that the tegu lizards (Salvator merianae) from South America increase their body temperature during the reproductive season, achieving as much as 10°C above the environment temperature at night. Thus, it seems that they are able to increase heat production and heat conservation in ways similar to the ones used by fully endothermic animals.

The tegu lizard Salvator merianae is a facultative endotherm.

The tegu lizard Salvator merianae is a facultative endotherm. Photo by Jami Dwyer.

As such an increase in body temperature happens during the reproductive cycle, it supports the hypothesis of endothermy evolving to assist the development of embryos, as explained above. Also, it indicates that ectotherms may engage in temporary endothermy and perhaps permanent endothermy may have evolved by using this path.

Further studies on the tegu lizards are needed to clarify this interesting phenomenon and expand our knowledge on endothermy evolution in mammals and birds.

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References:

Kemp, T. (2006). The origin of mammalian endothermy: a paradigm for the evolution of complex biological structure Zoological Journal of the Linnean Society, 147 (4), 473-488 DOI: 10.1111/j.1096-3642.2006.00226.x

Tattersall, G., Leite, C., Sanders, C., Cadena, V., Andrade, D., Abe, A., & Milsom, W. (2016). Seasonal reproductive endothermy in tegu lizards Science Advances, 2 (1) DOI: 10.1126/sciadv.1500951

Wikipedia. Endotherm. Available at: <https://en.wikipedia.org/wiki/Endotherm&gt;. Access on February 1, 2016.

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