118 posts · 123,065 views
Discussion of all things science with a focus on clarity, rationality and enthusiasm. Discussion topics: Natural Science, Biology, Evolution, Paleontology, Geology, Science Education
Recent research demonstrates that contrary to previous studies nutrient influx of Nitrogen and Phosphorous into coastal forests may contribute to mortality in the highly adapted mangrove trees. In a time of advancing Dead Zones, these findings hasten warnings about the dire consequences of poor-conservation efforts in regards to the world’s starkly limited water resources. ... Read more »
Lovelock, C., Ball, M., Martin, K., & C. Feller, I. (2009) Nutrient Enrichment Increases Mortality of Mangroves. PLoS ONE, 4(5). DOI: 10.1371/journal.pone.0005600
Scientists from Harvard, the Tokyo Institute of Technology and Queens University have published an article in PNAS in which game dynamics are used to model the evolution of cooperative behavior in individuals expressing a range of phenotypic variation.... Read more »
Antal, T., Ohtsuki, H., Wakeley, J., Taylor, P., & Nowak, M. (2009) From the Cover: Evolution of cooperation by phenotypic similarity. Proceedings of the National Academy of Sciences, 106(21), 8597-8600. DOI: 10.1073/pnas.0902528106
In order to evaluate new DNA sequencing technologies and better delineate the phylogeny of the caprinae (goat-antelope subfamily of Bovidae), several scientists from Spain recently extracted and sequenced 6,000 year old DNA from an extinct Balearic Island Cave Goat (Myotragus balearicus).
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Ramírez, O., Gigli, E., Bover, P., Alcover, J., Bertranpetit, J., Castresana, J., & Lalueza-Fox, C. (2009) Paleogenomics in a Temperate Environment: Shotgun Sequencing from an Extinct Mediterranean Caprine. PLoS ONE, 4(5). DOI: 10.1371/journal.pone.0005670
In addition to remembrance ceremonies paying tribute to the men and women of the armed services, Memorial Day has become a day in which Americans head to the great out-of-doors to enjoy friends, family, picnics and nature. With this tradition in mind, I thought it fitting to tell a couple of fish stories. These not so tall-tales are about a couple of good catches from the past year that somehow managed to get away from me.... Read more »
Long, J., Trinajstic, K., & Johanson, Z. (2009) Devonian arthrodire embryos and the origin of internal fertilization in vertebrates. Nature, 457(7233), 1124-1127. DOI: 10.1038/nature07732
With all of the fanfare over human origins and primate evolution the last few days, I thought that it would be appropriate to take a quick look at an article recently published in The American Journal of Physical Anthropology. The article, “Plio-Pleistocene eagle predation on fossil cercopithecids from the Humpata Plateau, southern Angola,” discusses the taphonomic evidence for the taking of primates by predatory bird around the Pliocene/Pleistocene boundary at the renowned Taung site in South Africa – including the taking of a hominin.... Read more »
Gilbert, C., McGraw, W., & Delson, E. (2009) Brief communication: Plio-Pleistocene eagle predation on fossil cercopithecids from the Humpata Plateau, southern Angola. American Journal of Physical Anthropology. DOI: 10.1002/ajpa.21004
...Charles Darwin recognized that phenotypic and ecological similarity existed between species with shared ancestry. This relationship between environmental fit and evolutionary history created a paradox in his mind; if ecologically and genealogically similar, shouldn’t species exhibit the same resource needs and be found coexisting in habitats where those resources are present? But at the same time, shouldn’t direct competition for those resources of mutual necessity push the organisms in different directions and towards acquisition of divergent characteristics?... Read more »
Cavender-Bares, J., Kozak, K., Fine, P., & Kembel, S. (2009) The merging of community ecology and phylogenetic biology. Ecology Letters. DOI: 10.1111/j.1461-0248.2009.01314.x
Throughout the United States native coccinellid populations are on the decline. The primary factor in this decline is most likely the establishment of exotic ladybeetles which compete, and out compete, the locals for vital food resources. For native Florida ladybugs, those food resources are aphids, and with the exception of Neoharmonia venusta, which is a predator of psyllids (jumping plant lice), all of beetles listed above find them quite delicious.... Read more »
Moser, S., & Obrycki, J. (2009) Competition and Intraguild Predation Among Three Species of Coccinellids (Coleoptera: Coccinellidae). Annals of the Entomological Society of America, 102(3), 419-425. DOI: 10.1603/008.102.0310
Though after only a cursory flip through, I find myself rather confused...? The article in hand appears to be of a scientific nature, with an abstract, introduction and discussion section – what’s the deal? Based on recent hype I was of the understanding that Ida was a scarcely clothed partygoer and heiress to the Hilton Hotel chain?
Ok, well maybe Ida isn’t all that, but I must admit, based on the photographs glanced so far, “daddy likes what he sees.” Talk about sexy…
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Franzen, J., Gingerich, P., Habersetzer, J., Hurum, J., von Koenigswald, W., & Smith, B. (2009) Complete Primate Skeleton from the Middle Eocene of Messel in Germany: Morphology and Paleobiology. PLoS ONE, 4(5). DOI: 10.1371/journal.pone.0005723
Starting in the 1940’s, Angelo Siciliano pioneered the cultural meme of “brawn over brains” and actively encouraged the males of one mammalian species - Homo sapiens - to pack on muscle in order to win over rivals for the affection of potential mates. However, lost to Charles Atlas was the possibility that the iconic “97-pound weakling,” which he vowed to aid through a rigorous program of dynamic-tension, may have been capable of achieving success on his own, independently of an increased body size. Key to such success would be to avoid the gauntlet of bullying sand-kickers altogether thereby reducing the necessity for brute force, and rather than investing in mail order fitness regimens, to instead turn the “chump to a champ” through allotting resources to two key areas - growing-up fast and getting to the female first! Thanks to the vector of modern media, Angelo’s meme is still infectious today (among populations of H. sapiens) and has probably met with some limited success; however there are several species that have found competitive advantage in strategies other that those associated with an increased body size – one such animal is the redback spider of Australia.The redback, Latrodectus hasselti, is a polyandrous species in which intrasexual selection relies less on choosey females and more on males competing for access to un-mated –“virgin” - females. Virgins are preferred by the male redbacks because, as with many other spiders, the males introduce a post copulatory plug to the female following sex, this has the effect of decreasing the likelihood of secondary male suitors successfully transferring genetic material – to have the best probability of forwarding their germ line to future generations, male redbacks seek out virgins. The virgin status of redbacks is identified by the males through a pheromone signal emitted by the female; within hours of mating, these chemo-signals cease being produced and the female becomes less attractive as a potential mate. Typically, sexually mature males of the species, having converged on the virginal pheromone, will find themselves geographically amassed at the female’s web with as many as five other males vying for mating access. When this occurs, the males combatively engage each other until a single victor remains. To the victor goes the mate.When it comes down to brute force, generally the male with the best weapons, most strength or greatest mass has the advantage in combat. This polyandrous scenario is familiar to most, but generally images of big horn sheep ramming each other, or gladiatorial deer with interlocked antlers are called to mind; the spiders are little different… Little different - except for an alternative intrasexual strategy to which some males find themselves better adapted.By way of sexual and natural selection, some male redbacks have decided that because of the dynamic between pheromone signaling, male-to-male competition and copulatory plugs, that it may be better to focus more on being the first to achieve sexual maturity via rapid development than to spend extra effort and time in growing to a larger size. In this way they would have first access to females, avoid web-sparring with males and because of the pheromones, even discourage rivals post copulation. Even Charles Atlas could respect that! KASUMOVIC, M., & ANDRADE, M. (2009). A change in competitive context reverses sexual selection on male size Journal of Evolutionary Biology, 22 (2), 324-333 DOI: 10.1111/j.1420-9101.2008.01648.x... Read more »
KASUMOVIC, M., & ANDRADE, M. (2009) A change in competitive context reverses sexual selection on male size. Journal of Evolutionary Biology, 22(2), 324-333. DOI: 10.1111/j.1420-9101.2008.01648.x
The “hole-in-the- head” frog (Huia cavitympanum) - so called because of its recessed ear drums- resides in hillside forest ecosystems of Borneo and Southeast Asia at elevations between 250 and 1000 meters. It is unique among the Ranidae for its ability to vocalize and hear ultrasound calls – well outside of the human range of hearing. ... Read more »
Arch, V., Grafe, T., Gridi-Papp, M., & Narins, P. (2009) Pure Ultrasonic Communication in an Endemic Bornean Frog. PLoS ONE, 4(4). DOI: 10.1371/journal.pone.0005413
The region of the Middle East referred to as “Levant” includes modern day Israel, Palestine and Jordon, and there are few places on earth more intensely studied by archaeologists than the birthplace of monotheistic religion. In addition to yielding a vast record of human occupation, culture and war, the archaeological sites within this region also document the decimation of several mammalian species. A couple of days ago (April 29), several Israeli scientists published an article in PLoS One in which they identified human driven overkill as the primary cause of regional extinction in several species of ungulates.
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Tsahar, E., Izhaki, I., Lev-Yadun, S., & Bar-Oz, G. (2009) Distribution and Extinction of Ungulates during the Holocene of the Southern Levant. PLoS ONE, 4(4). DOI: 10.1371/journal.pone.0005316
In addition to merging sci-fi art with the reality of science ('tagged ant' image below), researchers at the School of Biological Sciences within the University of Bristol have demonstrated that the ‘irrationality’ associated with contextual decision making is avoided in the ant Temnothorax albipennis as it chooses between alternative nesting sites.
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Great news - local management of water quality and other factors may significantly contribute to the survivability of coral reefs that have been negatively impacted by climate change.
A massive bleaching event took place on the Great Barrier Reef approximately three years ago and devastated a huge number of inshore reefs, but the corals made an unprecedented comeback – in only a year’s time!
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Diaz-Pulido, G., McCook, L., Dove, S., Berkelmans, R., Roff, G., Kline, D., Weeks, S., Evans, R., Williamson, D., & Hoegh-Guldberg, O. (2009) Doom and Boom on a Resilient Reef: Climate Change, Algal Overgrowth and Coral Recovery. PLoS ONE, 4(4). DOI: 10.1371/journal.pone.0005239
A lengthy introduction during the initial post on this topic (available Here) contrasted a harmonious view of nature with the perspective of nature as a series of oppositional organisms struggling to gain a competitive edge over rivals. As a model of this outlook, the ecotone boundaries between various sets of differing plant communities were offered as a case study. More specifically, the prairie, savanna and hardwood hammock ecosystems of the Big Cypress Preserve were forwarded along with the proposition that members of these communities actively challenged each other for limited resources. In staging this proposition the question was asked, “Why don’t trees invade - and take over – the prairie communities currently occupied by grasses?” After eliminating the likelihood that densely growing stands of grass crowded-out young saplings by denying them access to sunlight, cyclic wildfire were explained and presented as an alternative explanation. Moving forward with this production, a profile of one of the previously introduced characters is in order – the conifer tree Pinus elliotti.
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Beckage, B., Gross, L., & Platt, W. (2006) Modelling responses of pine savannas to climate change and large-scale disturbance. Applied Vegetation Science, 9(1), 75. DOI: 10.1658/1402-2001(2006)9[75:MROPST]2.0.CO;2
Gazing across the tranquil landscape of the Big Cypress Preserve, nature seems to be in balance, unchanging and at peace - picturesque beyond any poetic description. Here, anthropogenic throngs of sharply angled concrete and glass edifices suspend their battle for roadside dominance and yield themselves to a sea of sparsely treed savanna, rolling prairies of grass, and randomly scattered islands of thickly vegetated hammocks; the perfect environment for a relaxing stroll, a picnic, or even a quick nap. All may appear calm within this enchanting panorama; however, the perceived tranquility is but a chimera. A mere illusion of serenity resulting from shortfalls in the ability of Homo sapiens’ photoreceptors to see beyond the narrow range of the electromagnetic spectrum called visible light, an inability to hear sound outside of 22000 Hertz, and the failure of the human olfactory system to nose its way into the vast chemo-landscape of pheromones and other volatile chemicals in which it is continuously assailed. If the sensory apparatus of Homo sapiens was keener - more finely calibrated – the landscape of the Big Cypress would appear very different.
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Nordlund, D., & Lewis, W. (1976) Terminology of chemical releasing stimuli in intraspecific and interspecific interactions. Journal of Chemical Ecology, 2(2), 211-220. DOI: 10.1007/BF00987744
Mitochondrial DNA from twelve Neanderthal fossil assemblages was sequenced, compared and correlated with morphological data from fossil skulls, limbs and dentary remains to render evidence for multiple demes of Neanderthals from across Asia and Europe.... Read more »
Fabre, V., Condemi, S., & Degioanni, A. (2009) Genetic Evidence of Geographical Groups among Neanderthals. PLoS ONE, 4(4). DOI: 10.1371/journal.pone.0005151
Several mammalian families have been identified from the Aptian formation (where the current fossil was found), most of which are believed to represent species endemic to Australia; however one family – the Ornithorhynchidae – have also been found in Argentina.... Read more »
Beck, R., Godthelp, H., Weisbecker, V., Archer, M., & Hand, S. (2008) Australia's Oldest Marsupial Fossils and their Biogeographical Implications. PLoS ONE, 3(3). DOI: 10.1371/journal.pone.0001858
During the course of constructing a “Tree of Life” based on more than 120 gene sequences and fifty-five different species, a group of scientists led by Gert Wörheide of Munich have reached two conclusions; one, all Porifera (sponges) share a common sponge-like ancestor, and two, that ancestor did not give rise to the Bilateria.... Read more »
Shubin, N., Tabin, C., & Carroll, S. (2009) Deep homology and the origins of evolutionary novelty. Nature, 457(7231), 818-823. DOI: 10.1038/nature07891
Impressive brain imagery of a 300-million year old fish…
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Pradel, A., Langer, M., Maisey, J., Geffard-Kuriyama, D., Cloetens, P., Janvier, P., & Tafforeau, P. (2009) Skull and brain of a 300-million-year-old chimaeroid fish revealed by synchrotron holotomography. Proceedings of the National Academy of Sciences, 106(13), 5224-5228. DOI: 10.1073/pnas.0807047106
If one were to draw a line depicting the rate of average global speciation or evolutionary novelty produced over the last billion years, this linear representation would certainly have a spike near the geologic time of the Cambrian Explosion. By about 500 million years ago, all present day phyla (i.e. body-plans, or animal “designs”) had representative species on the planet (with the exception of Bryozoa), including that of the most abundant animal and second-most abundant organism overall found on earth today (following only bacteria) - the arthropods. The challenges these arthropods overcame in their journey from the sea to a terrestrial existence were both immense and varied. In a recent article published in Geology, James W. Hagadorn and Adolf Seilacher find clues to one arthropod’s strategy to overcome the obstacles of dehydration and desiccation as it makes the transition landward. Within the Orthoquartzites of the Elk Mound Group in central Wisconsin, a type of ichnofossils called Protichnites tell a tale of behavioral adaptation and evolution. Protichnites are trace fossils that display two parallel lines of tracks with a linear depression at the center. The parallel lines are essentially rows of footprints aligned towards the animal’s direction of travel. Carefully examined, these lines can be used to translate and interpret gait. In the case of the currently examined Elk Mound fossils, “the deeper impressions made by the rear pair of walking legs (i.e., the “pushers”) repeat symmetrically, in the same rhythm as the shell marks. This suggests synchronous movement of leg pairs, similar to modern Limulus and eurypterids, rather than the alternating gait reflected in tracks of crustaceans, scorpions, and insects.” Photos from Referenced Article The linear depression at the center of the Protichnites fossils is thought to be remnant drag marks from a tail. When turning, the arthropod’s tail swings outward from the direction of the turn, like a pendulum; these “wide turns” can provide biomechanical clues describing the gait of the animal.One set of fossils studied by the authors, later named Protichnites eremite (eremite = Hermit), displayed a medial depression with irregular characteristics. “Instead of following the midline, its markings consist of oblique impressions that are always offset and shingled to the left side. It is unlikely that this represents an individual or population of individuals characterized by a malformed tail, because similar trackways of different widths occur on the same bedding plane and because such trackways occur on more than one horizon. Because there are no pushback hills on the rear sides of the oblique ‘tail’ impressions, it is also unlikely that this asymmetry reflects a behavioral strategy, in which the tail was bent sideways in order to assist in locomotion.”If the irregular tail marks don’t represent a morphological malformation or provide evidence for locomotion, then what do they indicate, what’s the diagnosis? According to Hagadorn and Seilacher, “the impressions resemble the touch marks of a high-spired, dextrally coiled shell” similar to that carried by modern day hermit crabs.The conclusion reached by the researchers is that the arthropods, while in transition to a terrestrial existence, probably “still left the water only for short durations, crawling around on the wet sand flats during low tides.” These intertidal sand flats proved ideal for promoting the growth of thin microbial films on which the light-footed arthropods left tracks and trails that later fossilized. Using modern hermit crabs as an analog, the authors surmised that, “with their cuticular exoskeletons and stiff appendages, arthropods were particularly well preconditioned for terrestrialization. Nevertheless their early pioneers still required special adaptations, such as large body sizes and the use of foreign shells, to minimize water loss.” Transporting a shell on their back buffered the arthropods from arid conditions, but at the same time altered their gait to such an extent that we can read it in the fossils today.Hagadorn, J., & Seilacher, A. (2009). Hermit arthropods 500 million years ago? Geology, 37 (4), 295-298 DOI: 10.1130/G25181A.1... Read more »
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