June 29, 2010

The red squirrel and 20 more endangered UK species


The red squirrel (Sciurus vulgaris) is native to England and was widespread here until about 70 years ago. In the last quarter of the 19th century, the grey squirrel was introduced to various parts of the UK from North America. It has had a devastating impact, replacing the native species whenever the two come into contact and causing significant damage to forestry through its bark-stripping activities. The red squirrel is now confined to the Isle of Wight and the Poole Harbour islands, where there are no grey squirrels, and an area of northern England, mainly in Cumbria and Northumberland, into which grey squirrels are continuing to expand
The Guardian had a slideshow of 21 endangered UK species on their website yesterday, including some of the more cosmopolitan species, like bluefin tuna and the leatherback turtle that get around quite a bit. It's a special set of picutres, illustrated by Sandra Pond, who's work strikes me as very old-fashioned, drawn with the care and love (and anthropomorphism) of illustrators from another time. As I said on Twitter yesterday, it reminds me of the FWS and NPS posters my grandfather tacked to the wall of his hunting cabin in Pennsylvania. Those posters came down long ago, and I wish I had had the sense to as my parents to save them.
Beautiful work.

June 16, 2010

The Little People of Flores

While we're on the topic, here's a nice review of the Homo floresiensis story: "Little People of Flores" from NOVA (auto-plays, below the fold).

June 15, 2010

A hobbit's contemporaries: Biogeography and insular evolution on Flores


ResearchBlogging.org
Painters create networks. The subject of the piece, even if it’s a simple splotch of color, garners the most attention, but without a descriptive background or other kinds of supporting elements to contextualize the portion of the painting where the artist wants you to look, the intended focus is lost. The subject loses a certain clarity of interpretation in the absence of those elements.
Hanneke Meijer and her colleagues are trying to provide that sort of context to Homo floresiensis in this paper from the Journal of Biogeography, noting the importance of the natural history and evolutionary development of other vertebrates on the island of Flores and how this might inform and contextualize the life history of this tiny mystery.
Digging on Flores began in the 1950’s with an archeologist named Theodoor Verhoeven, a Dutch Catholic priest and missionary on the island. He found stone artifacts with the remains of a Stegodon and a “large murid” in those early digs, leading him to conclude that Homo erectus had arrived in the southeast islands of the Sunda archipelago by the early Pleistocene, across Wallace’s Line, which marks a transitional zone between Asia and Australia where organisms from both continents are thought to have mixed and created an area with high levels of endemism. Verhoeven, in his published report of Liang Bua (pictured above), a different site where he began digging in 1965 and found some neolithic remains and artifacts, said, “This cave is extra important.” He was right. It was in this limestone cave that the curious story of Homo floresiensis, the so-called hobbit, began many years later.
As excavations of Liang Bua and other sites progressed, a more complete picture of Flores faunal evolution, ecology and biogeography started to emerge. Though these data span almost a million years of history, there are commonalities, beginning with some of the more typical of other insular environments, a relatively poor diversity of taxa. The oldest records date to over 900,000 years ago, and thus far reveal a very few vertebrates: a tortoise of the Geochalone genus, now extinct, the Komodo dragon and the smallest known species of pygmy Stegodon, S. sondaari, which weighed in around 300 kg (just the tusks of a full grown African elephant can weigh up to 80 kg). Somewhere during the transition of the early to middle Pleistocene the tortoise went extinct, as did S. sondaari, but as the Pleistocene progressed, the proboscidean was replaced by another of the same genus, the larger S. florensis florensis, another immigrant to the island that probably evolved into the contemporary of H. floresiensis, S. florensis insularis. The giant rat Hooijeromys nusatenggera appears in the fossil record of this time as well as another monitor besides the Komodo, Varanus hooijeri, both of which the authors speculate were probably present in earlier time periods, but have smaller more delicate bones resistant to preservation. Alongside these remains stone artifacts from hominins have been found and of course, the very skeletal remains of H. floresiensis.
Based on this history, particularly evidence from the middle to late Pleistocene, the authors are trying to illustrate a Flores where the inhabitants are part of a highly endemic, phylogenetic continuum of species that underlines just how normal this kind of situation is for an isolated island community. S. florensis florensis was a rare vertebrate immigrant, but was filling a vacant niche and evolved into S. florensis insularis. This is supported by the general trend of island proboscideans displaying high levels of endemism and the fact that an entirely different species lived on Timor at the time. H. nusatenggera is very closely related to the extant giant rats on the island, and is probably ancestral to most of them.
As an island system, Flores certainly conforms to the so-called island rule (if such a thing can be said) home to giants rats and dwarf ungulates, adaptive responses to resource limitations, unique niche availability, absence of predators and the dynamics of decreased competition. Changes in body size are observed with other phenomena, such as the reduction of length and fusion of bones in the distal limbs for stability, increased hypsodonty in teeth for a changing diet or an often extreme reduction in brain size (the energetic requirements of nervous tissue is elevated).
But the first founding structure was determined by the geography of the island. Wilson and MacArthur’s Theory of Island Biogeography links the extremity of isolation with the relative richness of species, and the “impoverished” state of Flores historically fits this notion. The oceanic barrier to dispersal is crossed by only the most capable: birds, bats, tortoises, proboscideans, humans, lizards and rodents, which accurately describes what the fossil record shows. Until recently, with the habits of Homo sapiens acting as a mass transit system of dispersal, immigration to the island was a rarity. The composition of insular communities like Flores are described as “disharmonious” because of the structural differences between island and mainland ecosystems, which maintain larger populations and top level, typically mammalian predators. It's important to note (and integral to the authors' argument) that while it's interesting to highlight the oddities of island ecology, Flores is a very normal island community considering its biogeography.
All of this leads up to the subject, the focus of the entire picture: that H. floresiensis, as a part of this community, was the result of the “insular dwarfing of Homo erectus”:
Homo erectus is the prime candidate for the role of ancestor of H. floresiensis, as it was the only hominin present in Southeast Asia in the Pleistocene. Having reached Java by the Early Pleistocene (Swisher et al., 1994; van den Bergh et al., 1996), H. erectus was almost certainly present on Flores by the Middle Pleistocene (Sondaar et al., 1994; Morwood et al., 1998), as evidenced by the artefacts from the site of Mata Menge. Bromham & Cardillo (2007) showed that insular primates conform to the island rule and undergo shifts towards smaller body size in an insular environment. We therefore suggest that after its arrival on Flores, H. erectus followed the evolutionary path towards dwarfism and decreased in body size as a response to the absence of mammalian carnivores and the limited energy resources, as might any large-bodied mammal in an insular setting. Moreover, the observed size decrease in H. floresiensis when compared to H. erectus (c. 52% of H. erectus) falls within the range of other insular primates (Bromham & Cardillo, 2007).
This is largely in response to the cladistic analysis performed by Argue et al. in 2009, who...
...refuted the insular dwarfing hypothesis. However, the loss of derived features in insular evolution introduces a number of homoplasies, which in a cladistic analysis can easily be misconstrued for synplesiomorphies. This would lead to a more primitive position of the island form, exactly as was found by Argue et al. (2009). Given the small difference in tree length between the most parsimonious solution and the one in which H. floresiensis is derived from H. erectus, we find the cladistic analysis unconvincing. A careful evaluation of the characters, to see whether any homoplasies can indeed be attributed to typical insular developments, is needed to resolve this.
In case you’re not up on your plasies, what Meijer et al. are saying is that some of the characteristics of H. floresiensis acquired through insular evolution (homoplasies), such as the “robustness” of their limbs, could be mistaken for more primitive features associated with earlier hominins (synplesiomorphies) and need to be better accounted for in future studies.
In Liang Bua, there are very distinct layers of volcanic ash between the Holocene and Pleistocene layers of sediment, and across that boundary, very different assemblages of organisms. Stegodon and H. floresiensis are thought to have gone extinct around the time of that eruption ~19,000 years ago and as all islands in the area, were eventually replaced by Homo sapiens and their selected companion/invader organisms.
Image by Rosino
Meijer, H., Van Den Hoek Ostende, L., Van Den Bergh, G., & De Vos, J. (2010). The fellowship of the hobbit: the fauna surrounding Homo floresiensis Journal of Biogeography, 37 (6), 995-1006 DOI: 10.1111/j.1365-2699.2010.02308.x

June 9, 2010

Southeast Asia in the Pleistocene, from grassland to rain forest


ResearchBlogging.orgI’ve been trying to keep up with the Gulf situation, so most of my reading of late has been dominated by those details, and the unread numbers in my RSS folders were a little intimidating, but I finally found some time to read some of the papers I’ve earmarked in the past month or so.

This study from the Journal of Biogeography attempts a new method to assemble the paleoecology and paleoenvironment of Southeast Asia in the late Pleistocene and runs a lengthy comparison against the results of previous studies, corroborating the evidences. The interest in reconstructing these environments is largely generated from more recent discoveries of hominins that lived there in the Pleistocene. Data regarding hominin-mammal interactions is important and can be used to determine evolutionary nuances. If the environments in which these hominins lived can be interpreted, it can give us more details about how they lived, how they continued to disperse and even give scientists better clues as to where remains and artifacts can be found.

June 4, 2010

Congratulations in order, and a look at how scientific ideas can inspire art

Yesterday, Heather received word that one of her recent drawings, Remediation I would be included in the Metro Montage at the Marietta-Cobb Museum of Art. Obviously, big congrats are in order. I’m incredibly proud of her and her work and thankful every day that she chooses to share her talent and her life with me.
The piece is the first of a series of similar compositions that picture animals on floating islands of habitats yanked from the earth that are connected to one another via human structures. Despite its name, however, Remediation I had a predecessor at TVG.
Back in February, as Tai Shan and Mei Lan were being rounded up to be shipped back to China, I found a paper reviewing experimental mapping of the giant panda’s fragmented habitat along certain mountain ranges and explored the possibility of creating corridors between forest patches in order to increase gene flow and keep the patch populations from becoming so small that recovery is impossible. I asked Heather if she could illustrate the post after we chatted about fragmentation concepts for a while and this is what she drew:

Remediation I is pictured below. It’s far too big to scan, so please excuse the relatively poor quality; we need a better camera.

It’s a perfect example of how scientific ideas can become artistic ones and how the ideas that enter our heads can be stripped of context and completely refigured. We start with a research paper, the summation of years of rigorous study that constructs (or represents, however you want to look at it) a system of interlocking parts that can be transposed to a different framework completely and be thematically represented in an image. The image inspires other, more complicated images that comprise a series and the series inspires a whole new set of images that constitute another theme, but were obviously informed by their predecessors. It’s not a closed system, however. Running concurrently is the constant stream of daily information that can add context and nuance. Four months later, Heather is crafting the last of the Remediation series and putting the final conceptual touches on its child, a completely new take on a multi-faceted theme.
It started with a paper, moved through a review and an illustrated blog post and ended up on framed paper which will ultimately sit on a wall in a gallery for the summer. It’s not often that I actually break down process on this site, but this was far too good of an example to pass up.
My love of science has directly informed my own creativity. Scientific concepts challenge your perspective, force you to be more analytical, to take apart and reassemble, to focus on pieces and segments and then to pull back as you line them up into something more formidable. The process of transposing that I described above, which Heather implements in these works, is all about moving frameworks that can be applied in very different situations. As I've said numerous times before, it fascinates me, these tenuous threads between conceptual paths, different in application and purpose, but not so different with the context removed.
Don't walk away with the impression that I'm trying to relay some sort of silly equivalence like "science is art and art is science"; it's more of a matter of attempting to refute the impulse to elevate one above another, or to comfortably lean, to one side or the other, of that often brightly drawn academic line between disciplines.

June 2, 2010

Lot

The asphalt was cracked down the long center and spottily filled with tar, a jagged black line through the parking lot. She walked that line as a child, arms straight out to her sides, swaying, tentatively stepping one foot over another. It was the only repair the city had done in fifteen years, that tar patch; the lot was rife with similar damage, splintered and cragged in places, chunks of pebbly asphalt turned up and over. She ran her fingers over the tar, and looking closely as she did, saw fractures throughout, felt them rough against the grain of her fingerprints. It was an illusion, the rich smoothness of the tar, like cooled – once molten – rock. When she was a child it was a hot vein through a barren waste. She could feel the heat through her jellies with each lingering step, careful not to fall to one side or another, an inflated concern that evaporated, along with the unspoken rules, as soon as she stumbled.
A year ago Pam’s sister found her sitting in the lot, alone and in the dark, lit by the streetlamp above. Her sister spoke sharply and Pam complied, shuffling back to the apartment, taking what she needed and playacting regret. That was the last time Pam left by herself. Tonight would be the last time in another year.
But not for another hour or so. The sun crowned the sparse treetops yet, and it was too early to dread her sister’s long walk to the lot. The night would be cold and whisper chill before long, but she was dressed nice and warm, and tucked herself inward, hugging her legs tightly against her chest. As the light waned, she would watch the long black tar line slowly fade until the lamp above her clicked, preserving a segment of the crack in a circle of fluorescence.