What makes a species?
.The famed AMNH scientist Ernst Mayr proposed the most widely known species definition or concept as ““groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups” By this logic, new species arise when populations are separated across space and time AND some isolating mechanisms evolve such that these separate groups - once members of the same species - can no longer successfully interbreed
Thankfully there is a buffet of species concepts (26 by one author’s count!) for young upstart evolutionary biologists like Sophia and Nancy to chose from ( and to critique)
Sophia and Nancy are wading through the morass of species concepts under the mentorship of herpetologist, David Kizirian, as part of a study to revise the taxonomy of the genus Dinodon, a snake with several species found across Asia. In David’s words, Dinodon’s taxonomy “is a mess.” Within the genus, there are some species that should be 2 and 2 species that should be one. Take for example a 2013 paper co-written by AMNH curator, Dr. Frank Burbink. He discovered that Dinodon was a paraphyletic group. In other words, the Dinodon genus represented a group of species whose members were descended from a common ancestor (good taxonomy) but left out some species who were classified under different genera (bad taxonomy). So Sophia and Nancy will be using morphological traits to see if the taxonomy of Dinodon can be improved. On this quest, the need to define what species concept they are using especially if they stumble across any new, hidden species.
A frequent theme of my SRMP blogs is how little we know. Usually I find that very uplifting (there will always be a quest for knowledge!), but not in the case of the Burmese Star Tortoise.
Very little is know about the ecology of this endangered tortoise because there are so few to be studied. As of the early 2000s, Burmese Star Tortoises (found only in Myanmar) were believed to be extinct in the wild. Over-harvesting, driven in part by the international pet trade, is largely responsible. Therefore, in 2007, remaining tortoises were captured and brought to special “head-start” facilities to be bred with the hope of one day reestablishing a viable, wild population.
A captive population that started with fewer than 20 tortoises is currently over 8,000 in 4 assurance colonies in Myanmar. And now, conservationists are starting to release these captive-bred tortoises back into the wild; however, before they do, all tortoises need to pass a health check. But how can you tell a turtle is healthy?
Dr. Suzanne Macey and her students Ariana and Michelle are working with a colleague, Dr. Bonnie Raphael, from the Wildlife Conservation Society (aka, the Bronx Zoo), to review the results from pathogen and hematological data that has been collected on these tortoises since 2013. Hematological screening can be used to flag problems like anemia, dehydration, or signs of prolonged infection. Those individual tortoises with immediate poor diagnoses, obviously receive medical treatment. Those that are cleared are considered for release.
Ariana and Michelle are taking a step back and are investigating the health of the captive head-start population as a whole. By analyzing the existing data, they are using statistical models to uncover patterns that can lead to creating better health standards for this poorly understood tortoise. E.g., what is a normal white blood cell count for a healthy tortoise? Do critical thresholds vary with sex or at the different head-start facilities? Vets don’t have this information, but the creation of “wellness” health standards for these tortoises is crucial for their future releases. This is why they need the results of Suzanne, Michelle, and Ariana’s study.
Jade, I mean Jadeite
Prior to my visit to Rondi’s lab, I thought Jade was Jade. Ah, there is no boundary to my ignorance.
“Jade” is a common name shared by two unrelated mineral forms. There’s nephrite Jade (think most traditional Chinese carvings) which can be found all throughout Russia and China. Then there’s Jadeite which is exceedingly rare and found in Guatemala and Burma.
For years, Dr. George Harlow, Curator in Earth and Planetary Sciences at AMNH has been studying jadeite from the Guatemala Suture Zone, the boundary between the North American and Caribbean tectonic plates. This former subduction zone marks places on the earth where two plates meet and collide. Oceanic plates (most of the Caribbean plate) are made of denser rock than that of the continental crust and sink beneath the other. Water carried down with oceanic crust is heated and hydrates certain rocks to form serpentine minerals. Jadeite is formed by the passing of this fluid through and over parent rocks. (NOTE: Add Youtube video of George https://www.youtube.com/watch?v=TWofncaF2Ds)
Jadeite most commonly takes a hue of green; however, may include a variety of colors including pink, lavender and blue (Note: Add a picture of an Olmec head made of jadeite). Jadeite is fairly well studied, but something known as black jade that is found in close proximity to jadeite. Scientists don’t know from what parent rock it was derived or what that transformation process looked like. Knowing how a mineral forms can unlock clues to the evolution of the earth’s crust. Therefore black jade is like finding a blank page in the Earth’s history book. Khakima, Carlos, Rosa and Rondi are attempting to fill in the blanks studying black jade of the Guatemala Suture Zone
The process of understanding how black jade formed requires careful observation with a high powered petrographic microscope. The team are scanning thin slices of these rocks to find evidence of the original rock prior to it being altered by and recrystallized from fluids: they are looking for sections in the rocks without small fluid droplets trapped inside minerals, and for chemical zoning (areas with evidence of the mineral growth) to map the changes that black jade experienced from its parent rock to final form.
The secrets of the inner ear
Peel back your skin & muscles and peer past your skull and you’d find three very important little semi-circular canals that make up your inner ear. These canals control your balance and aide in motion – and are the key to Brian Shearer, Elise, and Diana’s investigation of extant and extinct primate locomotion.
A micro-CT scanner allows you to penetrate a skull (and other things) without the very invasive and destructive process of physically opening up a skull. X-ray light is bombarded at the specimen. Bones reflect these x-rays differently according to their density, a phenomenon that allows for the creation of a three dimensional computer model. With this model or 3-D scan, bones are differentiated based on their density.
In their search for the semi-circular canal, Elise and Diana slowly e-dissolve their 3-D skull models leaving behind only the densest bones: ghostly teeth and the petrous, one of the densest bones in the human body and the bone that supports the semicircular canals.
Once located, Elise and Diana, start the process of rendering or digitizing the canals. Going layer-by-layer in this 3-D model they trace the canals’ outline and contours. When completed, the team will measure the size, volume, and the orientation of each canal, metrics that correlate with modes of primate location. For example, more perpendicular angle of orientation is associated with faster swinging in primates know for their brachiation (aka arm swinging locomotion).
The team hopes to explore the form of these semi-circular canals in both juveniles and adults across several extant (living) primates. In the end, better understanding the relationship between the form of the semicircular canals and locomotion in extant species may help paleontologist understand how extinct primates got around – simply by looking to its inner ear.
It’s a very humbling experience to hold a chondrite (aka a meteorite containing chondrules). Never mind that you are holding something from outer space. You are also holding one of the oldest objects in the solar system (~4.5 billion year old). And its study can unlock many mysteries into how our solar system formed.
Meteorites are rocks originating from space (e.g., an asteroid, the moon, etc.). Possibly less familiar is the chondrule. Chondrules are tiny, circular grains of minerals formed in the protosolar nebula (a molecular cloud swirling around our proto-sun) by the rapid melting of accreting dust. The chondrite is composed of inclusions (i.e. chondrules) embedded in matrix, a fine-grained mixture of minerals. In many cases, chondrules are surrounded by a “rim” of fine-grained material that resembles the matrix but has different textural and compositional properties.
The question is when and where did the rims form? In the solar nebula or later in our solar system’s history? The answer is important to understanding the origins of the earliest solids and how our solar system evolved. Kim Fendrich, along with Vivian, Nathanael and Annie used an electron microprobe to map the meteorite’s elemental composition and are using Adobe Illustrator to process these maps and characterize the various features within them.
Specifically, they will categorize the inclusions and quantify their abundance, measure the size and distribution of rims, and observe chemical relationships between the various components. They are doing so in search of meaningful correlations that may help clarify the accretionary processes that took place during the early stages of solar system formation.