“The Botanists Among Us: Host plant specialization in insects”

It’s been a busy week for me—just two days after doing a presentation on tiger beetles to the Webster Groves Nature Society’s Entomology Group, I gave a talk to the St. Louis Chapter of the Missouri Native Plant Society. As implied by the title, the talk focused on host plant specialization among insects, first covering the major groups of plant-feeding insects and the evolutionary themes involved in adaption to (and away from) plant-feeding, then moving to examples of different types of host plant specificity and highlighting some of the more interesting insects that I’ve encountered (and managed to photograph) over the years.

Like my talk two nights earlier, it was another fun and lighthearted conversation with a highly engaged crowd, and I appreciate the great interest shown by a group that is normally much more focused on plants than on insects. Once again, it was well-attended locally, but for the benefit of those who were not able to attend the meeting in person and that may be interested in this subject, I’ve prepared a PDF version* of the presentation that you can download and peruse at your convenience.

* All content is copyrighted and may not be reproduced or distributed without written consent.

© Ted C. MacRae 2019

Skulls on my desk

Even though I am a scientist working in an organization with hundreds of other scientists, I can lay claim to one true uniquity—I am the only one I know of that has a skull on their desk! Six, actually. They’re not real (sadly), but their impact on most first-time visitors to my office is no less amusing. Typically the first question is, “What are those?”—to which my standard reply is, “Those are former colleagues with which I’ve had problems.” Maybe that is a little mean, but it usually gets a laugh (sometimes nervous). Hey, if somebody doesn’t understand my sense of humor, they’ll have to learn sooner or later.

¹ In anthropology, most of these would actually be called “crania” (skull minus associated mandible) rather than skulls. We can be less pedantic here.

I am, of course, talking about my collection of hominid fossil replicas. Yes, I am an entomologist, but I’ve also had a lifelong fascination with paleoanthropology and human evolution. Actually, I think my broad interest in multiple disciplines is rather typical of those who are drawn to the natural sciences, so it surprises me that there aren’t more scientists where I work with a skull on their desk. After all, this was a common practice among ancient scholars as a reminder of their mortality. My reasons for having skulls on my desk are less philosophical—I just like having replicas of some of paleoanthropology’s most important fossil hominid finds. They are icons of a subject that couldn’t be more relevent—our own origins. Just as nothing in biology makes sense except in the light of evolution, nothing in human society makes sense except in the light of human evolution. The skulls are a reminder of not just who we are, but why we are.


Taung 1, “Taung Child”

Taung 1, "Taung Child"

Taung 1, “Taung Child” (Australopithecus africanus) | Taung, Republic of South Africa, 2.8 mya

The “Taung Child” is thought to be a 3-year-old child representing Australopithecus africanus (which means “southern ape of Africa”). Discovered in 1924, it was the first hominid fossil discovered that, while definitely not a member of our own genus, could still be argued as somewhat human. Nevertheless, it would take another 20 years—once other, adult, specimens were discovered in southern Africa—before A. africanus would begin gaining acceptance in the scientific community.

The significance of the Taung Child was that it provided fossilized evidence of upright, two-legged (bipedal) walking much earlier than expected. Up to that time, it was believed that humans began to walk upright only after they had developed a large brain. Robert Broom, upon arriving in South Africa in 1936 and seeing the Taung Child for the first time, is said to have knelt at the edge of the table and exclaimed, “I behold my ancestor!” It is now thought that A. africanus represents southern African descendents of A. afarensis from east Africa but is not in the direct lineage leading to modern humans. Nevertheless, the Taung Child remains an iconic hominid fossil, especially given the suspected circumstances of its death—attacked and killed by an eagle! Puncture marks at the bottom of its eye sockets resemble those made by the talons and beak of modern eagles, which are known to attack monkeys in Africa today. The skull was also found among eggshells and a mixture of bones from other small animals that could have been preyed upon and show damage resembling that made by modern eagles.


STS 5, “Mrs. Ples”

Australopithecus africanus, "Mrs. Ples," STS-5, Sterkfontein, South Africa, 2.5 mya

STS 5, “Mrs. Ples” (Australopithecus africanus) | Sterkfontein, Republic of South Africa, 2.5–2.1 mya

Discovered in 1948 by Robert Broom, this nearly complete adult A. africanus cranium actually served to convince scientists of the time that the Taung Child was not just a baby chimpanzee whose ape-like features had not yet developed. Broom named the new fossil Plesianthropus transvaalensis and hypothesized that she was a middle-aged female—thus the nickname, “Mrs. Ples.” The fossil is now regarded to represent the same species as the Taung Child, differing chiefly in the adult character of prognathous (forward projecting) jaws, and is also now thought to have belonged to a sub-adult male.

I had the good fortune to see the actual fossil in person on a private tour of the Transvaal Museum’s “Broom Room” during a trip to South Africa in 1999. I wrote about that experience in a guest post at Christopher Taylor’s Catalogue of Organisms titled, Origins – A Day in the Broom Room as follows:

As Dr. Fourie held the cranium for me to look at, I noticed the fossil was about 3.5 feet off the floor—about the presumed height for the species. I suddenly saw Mrs. Ples standing before me in life – a living, breathing being, not an animal, yet not quite human either. I may not have used Broom’s precise words, but I whispered something along those lines to myself as the slender, hairy virtual creature stood before me. The Museum Gift Shop was selling plaster replicas of Mrs. Ples, one of which now sits on the desk in my office. I think about that experience at the Transvaal Museum almost everytime I look at it.


SK 48, “Paranthropus crassidens

SK 48 "Paranthropus crassidens" (Paranthropus robustus) | Swartkrans, South Africa, 1.8-2.0 mya

SK 48, “Paranthropus crassidens” (Paranthropus robustus) | Swartkrans, Republic of South Africa, 1.8–1.5 mya

While Robert Broom was excavating in South Africa, he recognized that the fossils he was finding represented two distinct morphs—a “gracile” form now encompassed by A. africanus, and a more “robust” form that he described in 1938 as Paranthropus robustus. SK 48, discovered by Broom and Robinson in 1952, was until recently the most complete example of this latter type. The term “robust” refers not to the size of the body, but rather the characters of the skull that include a prominent sagittal crest and robust zygomatics and mandible with large, thickly enameled post-canine dentition. These features provide extra space for chewing muscles and larger molar surfaces—adaptations linked to a powerful chewing complex designed for processing tough, fibrous foods. Paranthropus robustus appears to have been a dead end taxon, being the last of the robust australopithecines and having no apparent descendants. It seems to have been a contemporary of early representatives of the genus Homo—our genus—in southern Africa (tempting speculation on what might have happened to them!).

This was another of the fossils I saw first hand during my visit to the Broom Room, and the plaster replica purchased from the Museum gift shop sits alongside Mrs. Ples on the desk in my office.


OH 5, “Nutcracker Man”/”Zinj”

KNM OH5, "Nutcracker Man" (Paranthropus boisei) | Olduvai Gorge, Tanzania, 1.8 mya

OH 5, “Nutcracker Man”/”Zinj” (Paranthropus boisei) | Olduvai Gorge, Tanzania, 1.8 mya

When it comes to fossil hominids, Olduvai Gorge in Tanzania is easily among the most famous of sites, and of the fossils found at Olduvai Gorge, OH 5 “Nutcracker Man” is easily the most famous. Discovered in 1959 by Mary Leakey, it was originally classified as a new genus and species, Zinjanthropus boisei, but is now accepted as a member of the genus Paranthropus. It is thought to represent a derived, “hyper-robust” species descended from P. aethiopicus (see “The Black Skull” below), which lived in east Africa a million years earlier. Like its congeneric contemporary in southern Africa (P. robustus), Nutcracker Man appears to have died out with no living descendents.

The discovery of Nutcracker Man (sometimes called “Zinj” in reference to its original genus name) brought the “robust” morph, typified until then by P. robustus, to a new level of robusticity: wide, outward-flaring zygomatic arches that projected forward of the nasal opening to form a dished-shape face, a large sagittal crest atop the skull, and a massive lower jaw. These traits no doubt allowed plenty of room and attachment for the huge chewing muscles needed for its diet. If features such as this aren’t enough to justify a nickname like Nutcracker Man, surely the megadont cheek teeth—up to four times the size of our own—will seal the deal!


KNM-WT 17000, “The Black Skull”

KNM-WT 17000, “The Black Skull” (Paranthropus aethiopicus) | West Turkana, Kenya, 2.5 mya

KNM-WT 17000, “The Black Skull” (Paranthropus aethiopicus) | West Turkana, Kenya, 2.5 mya

The “Black Skull” is actually one of the more recent hominid fossil finds. Discovered in 1985 by Alan Walker, it was originally classified as Paranthropus boisei—the same species as “Nutcracker Man.” However, the Black Skull is nearly a million years older than Nutcracker Man and apparently shares some characters with the even older Australopithecus afarensis (“Lucy” being its most famous member). All three of these forms lived in east Africa, though at different times, and the Black Skull was eventually deemed to represent yet another distinct taxon—Paranthropus aethiopicus (described some time earlier, but from only a partial lower jaw). It is the earliest known member of the genus, and the Black Skull remains the only known skull representing the species. Paranthropus aethiopicus likely gave rise to the later P. boisei in east Africa and P. robustus in southern Africa.

The Black Skull isn’t as robust as Nutcracker Man, but it is my favorite robust australopithecine fossil because… it’s BLACK! How cool. Actually the skull started out white, just like any other bone prior to fossilization, and developed its dramatic dark blue-black color as a result of the manganese-rich soil in which it spent the past two and a half million years.


KNM-WT 15000 “Turkana/Nariokotome Boy”

KNM-WT 15000, "Nariokotome/Turkana Boy" (Homo ergaster) | Nariokotome, West Turkana, Kenya, 1.6 mya

KNM-WT 15000, “Turkana/Nariokotome Boy” (Homo ergaster) | Nariokotome, West Turkana, Kenya, 1.6 mya

The “Turkana Boy” skull is actually part of a remarkably complete skeleton excavated in 1984 by Richard Leakey and colleagues. Some regard Turkana Boy as a representative of Homo erectus, the first human to migrate out of Africa into Eurasia, while others consider the African populations to represent the distinct taxon, H. ergaster. One of paleoanthropology’s most contentious topics is whether modern humans evolved only from H. ergaster in Africa (the second “out-of-Africa”) or locally from H. erectus populations (including H. ergaster) throughout the Old World (“multiregionalism”). Molecular data seems to favor the former, but the latter has passionate adherents. Of all the skulls sitting on my desk, this one alone can be regarded as a possible near-direct ancestor!

Turkana Boy is not only remarkable by the completeness of its skull, but also the astonishing 90% coverage of the complete skeleton that results when bilateral symmetry is used to fill missing bone. Such completeness is extraordinarily rare among fossil hominids, and it has provided a wealth of information about the body size, shape, and growth rates of H. ergaster. The skeleton is thought to have belonged to a boy 12 or 13 years of age, measuring 5’3″ tall and weighing 106 lbs at the time of death. Interestingly, the pelvis reveals a greater ability to run than modern humans, while other bones more closely resemble those of Australopithecus. The long, slender body seems to be an adaptation to the hot, dry climate that existed in Africa.


Thanks to all who participated in ID Challenge #22. I have to admit how surprised and impressed I am about how many of you seem to be as interested in and up to date on human evolution as I. Congratulations to perennial BitB challenge master Ben Coulter, who takes the win with 63 pts. Dennis Haines (61 pts) and Mike Baker (60 pts) complete the podium, and honorable mentions go to Sam Heads (58 pts) and tandemtrekking (57 pts).

Copyright © Ted C. MacRae 2013

An elegant living fossil…

In the insect world, hyperdiversity is the norm. More than a million species are known, and perhaps several million more await discovery. Beetles alone represent nearly a quarter of the earth’s described biota, with one genus (Agrilus in the family Buprestidae) bursting at the seams with more than 3,000 described species (Bellamy 2008). Biodiversity gone wild! While birders routinely field identify (and list) a majority of the birds they see to species, most insect enthusiasts are happy if they can simply identify their subjects to family—in most cases still leaving several hundred to several thousand possibilities for species identification. Even trained entomologists usually can identify only a tiny fraction of the insects they see and remain just as clueless about the vast majority of insects they encounter that don’t represent one of their limited number of study groups.

Pelecinus polyturator female | Wayne Co., Missouri

Pelecinus polyturator female | Wayne Co., Missouri

 Of course, that doesn’t mean field identification is impossible for all insects—certain groups such as butterflies, dragonflies, and tiger beetles lend themselves to field identification due to their relatively large size, bright colors, and distinctive markings. Many would also include the aculeate hymenopterans (i.e., “stinging” wasps and bees) among those groups for these same reasons. However, the vast majority of hymenopterans belong to a multitude of families characterized by tiny, parasitic species that seem (to this coleopterist’s eyes) to differ only in bafflingly minute details of wing venation and tibial spurs. (Honestly, I couldn’t tell you the difference between Tanaostigmatidae and Tetracampidae if my life depended on it!) Nevertheless, there are a small handful of parasitic hymenopterans in North America that are instantly recognizable due to their giant size (2 or more inches in length)—namely, Megarhyssa spp. (giant ichneumons) and the species shown in this post, Pelecinus polyturator (American pelecinid). Pelecinus polyturator is the only North American member of the family Pelecinidae, which itself contains only two additional species that are restricted to Mexico and Central/South America. It wasn’t always this way—fossils assignable to the family and representing 43 species in a dozen genera have been found as far back as the early Cretaceous (121–124 mya) across North America, Europe, and Asia (Grimaldi & Engel 2005). Surely this represents just the tip of the iceberg of Mesozoic and early Cenozoic pelecinid diversity, making today’s three species the last representatives of a once great lineage—”living fossils”¹ some might say.

¹ To ward off any scolding I might get from evolutionary purists, I get it; there is no such thing as a living fossil (except the T. rex skeleton in the movie “Night at the Museum”). I know that all species alive today have the same amount of evolutionary history behind them and are, if not from more immediate ancestors, highly derived compared to earlier life forms. I will admit that the term has become a bit overused as pseudoscientific shorthand for branding an organism as ‘primitive’ (another term which tends to raise hackles); however, I don’t see the problem with its use as informal reference to relatively ancient groups, usually more diverse in the past and now represented by only a few species. Innocuous shorthand is all it is.

This elegant female, recognizable by her extraordinarily narrowly elongate abdomen (males have a somewhat shorter abdomen that is widened at the end), was seen back in July 2011 as she flew to a blacklight and landed on nearby foliage in a mesic bottomland forest in southeastern Missouri’s Ozark Highlands. I have seen females on occasion over the years but have not yet seen a male, which are increasingly rare in more northern latitudes of the species distribution. I missed the focus a bit on this photo (and also the other half-dozen or so shots that I took)—photographing an active subject at night on elevated foliage without a tripod is difficult to say the least! Nevertheless, after post-processing it’s a decent photograph. If you are wondering why it took me so long to post it, that’s because only recently have I gained the confidence to “clean up” poorly exposed photos where the subject and/or substrate on which they are resting is so distractingly littered with debris as this:

Yuk!!!

Yuk!!!

Compare the original photo here to the final photo above it—how many post-processing tools can you detect the use of? 🙂

REFERENCES:

Bellamy, C. L. 2008. World catalogue and bibliography of the jewel beetles (Coleoptera: Buprestoidea), Volume 4: Agrilinae: Agrilina through Trachyini. Pensoft Series Faunistica 79:1–722.

Grimaldi, D. and M. S. Engel. 2005. Evolution of the Insects.Cambridge University Press, New York, xv + 755 pp.

Copyright © Ted C. MacRae 2013

The 2nd-oldest Known Myrmicine Ant

Among the 20 or so insects represented in the Green River Formation (GRF) fossils that I currently have on loan, this rather obvious ant (family Formicidae) is the only one that is firmly assignable to the order Hymenoptera (wasps, bees and ants). This is not surprising, as hymenopterans are not well represented among GRF insect fossils. In fact, of the 300+ insect species that have been described from GRF deposits (Wilson 1978), more than two-thirds belong to just three orders—Diptera (flies), Coleoptera (beetles) and Hemiptera (true bugs). Hymenoptera, on the other hand, comprise only 4% of GRF fossils (Dlussky & Rasnitsyn 2002). I presume these numbers are more a result of taphonomic (fossil formation) bias than a true reflection of insect diversity in western North America during the Middle Eocene (47–52 mya).

cf. Myrmecites rotundiceps | fossil impression from the Green River Formation (45 mya, middle Eocene)

cf. Myrmecites rotundiceps (length = 6.7 mm).

Ants in particular have been poorly represented by GRF deposits. Only four named species were known until Dlussky & Rasnitsyn (2002) reviewed available GRF fossils and increased the number to 18 (15 described as new, one older name placed in synonymy). Diagnoses, line drawings, and keys to all covered subfamilies, genera and species provide one of the best treatments to GRF insect fossils that I’ve come across. According to that work, the fossil in these photos seems comparable to the description and illustration given for Myrmecites rotundiceps, a unique fossil with the general appearance of ants in the subfamily Myrmicinae but differing from all known Eocene and New World fossil ants by its very short, two-segmented waist. The only difference I noted was size—6.7 mm length for my fossil versus 5.5 mm for the holotype (see figure below). Of course, I’m more comfortable identifying extant Coleoptera than extinct Formicidae, so I contacted senior author Gennady M. Dlussky to see if he agreed with my opinion. He graciously sent the following reply:

I agree that specimen on your photo is very similar to Myrmecites rotundiceps. It is larger (holotype is 5.5 mm long), but it may be normal variability. I cannot see another differences.

Myrmecites rotundiceps, holotype (Gennady & Rasnitsyn 2002)

Myrmecites rotundiceps Gennady & Rasnitsyn 2002, holotype (reproduced from Gennady & Rasnitysyn 2002)

If correctly assigned, M. rotundiceps is the second oldest known member of the subfamily Myrmicinae—the oldest being Eocenidris crassa from Middle Eocene Arkansas amber (45 mya). In fact, the only older ant fossil of any kind in North America is Formicium barryi (Carpenter) from Early Eocene deposits in Tennessee (wing only). [Edit: this is actually the only older Paleocene ant fossil—there are some Cretaceous-aged fossils such as Sphecomyrma freyi (thanks James Trager).] Since myrmicine fossils of comparable age are lacking from other parts of the world, this might suggest a North American origin for the subfamily; however, it could also be an artifact of incomplete knowledge of ants from older deposits in other parts of the world. Myrmicine ants make their first Eurasian appearance in Late Eocene Baltic amber deposits (40 mya) and become more numerous in North America during the early Oligocene (Florissant shales of Colorado, 33 mya). (Dlussky & Rasnitsyn (2002) consider the Middle–Late Eocene ant fauna to represent the beginnings of the modern ant fauna, with extant genera becoming numerous and extinct genera waning but still differing by the preponderance of species in the subfamily Dolichoderinae over Formicinae and Myrmicinae.

IMG_1919_enh_1080x720

USA: Colorado, Rio Blanco Co., Parachute Creek Member.

The photo above shows the entire fossil-bearing rock (also bearing the putative orthopteran posted earlier).

My thanks to Gennady Dlussky and James Trager for offering their opinions on the possible identity of this fossil.

REFERENCES:

Dlussky, G. M. & A. P. Rasnitsyn. 2002. Ants (Hymenoptera: Formicidae) of Formation Green River and some other Middle Eocene deposits of North America. Russian Entomological Journal 11(4):411–436.

Wilson, M. V. H. 1978. Paleogene insect faunas of western North America. Quaestiones Entomologicae 14(1):13–34.

Copyright © Ted C. MacRae 2012

BitB Does CoO

STS 5 ('Mrs. Ples') | Australopithecus africanus - Sterkfontein, South Africa

Although my fondness for beetles is well known, I also have an inordinate fondness for systematics.  For this reason, Catalogue of Organisms by Christopher Taylor has long been high on my ‘must read’ list.  While there are no limits to the taxa – extant or extinct – that he writes about, one can be sure that whatever subject he picks, it will be comprehensively covered and richly referenced.  One of his more popular features is ‘Name the Bug’ (“bug” being any group of organisms, not just insects), where readers are invited to identify a featured organism and provide evidence to support their answer.  Points may be earned (and even usurped) in this free-for-all competition, with series winners eligible to request a post on the taxon of their choosing or write a guest post of their own.  As the most recent winner of this competition, I have chosen the latter and written a post called Origins – A Day in the Broom Room.  It’s about paleoanthropology, human evolution, and a personal experience with some of the field’s most iconic fossils.  I know these are subjects far outside my normal fare, but I hope you’ll take a look anyway and I thank Chris for letting me elbow my way onto his site for a while.  While you’re there, be sure check out the rest of the fine content on CoO – it might end up on your ‘must read’ list as well.



Copyright © Ted C. MacRae 2011

Carnival of Evolution #22

In my fifth blog carnival hosting gig, I am honored and priviledged to present Carnival of Evolution #22.  I’ve always considered this to be the most cerebral of the blog carnivals that I follow, and this month’s submissions have once again lived up to the high standards that I have come to expect – 26 submissions by 19 of the best evolution bloggers out there.  I suggest we all pour ourselves a glass of brandy, settle into our armchairs, and enjoy an evening of thought-provoking erudition.

Human & Primates

Andrew Bernardin at 360 Degree Skeptic presents an evolutionary psychology piece in his post, Less Visible Forms of Social Power | 360 Degree Skeptic. Are humans an exuberantly affiliative species, like the bonobo, or is our nature essentially hierarchical? Or both? (Not to mention the impressively variety of forms that hierarchies can take.)

There’s a new kid on the blog, and Chadrick Lane jumps right into fray with his inaugural post at The Ancestral Mind.  In Ancestral Mind in the Twitterverse: Discovering the information age through evolution, he recounts the magical feeling of visiting the Smithsonian Natural History Museum’s David H. Koch Hall of Human Origins, prompting him to ask “How is it that we have gone from a common ancestor with chimpanzees to a blogging, social networking, moon walking, singing and dancing species in just around 6 million years?” An impressive first post!

I was sure I’d receive multiple submissions dealing with the news of a potential new extinct human species, deduced from mitochondrial DNA sequence generated from a 40,000 year old finger bone found in a cave in a region of Siberia from which the remains of modern humans and Neanderthals have also been found.  David Winter, however, enjoys a monopoly on this topic with his post, Does a forty thousand year old finger point to another human species? at The Atavism.  David reminds us that inferring species boundaries is a tricky business, and the mtDNA sequences are not, in and of themselves, proof that the finger belonged to a member of a third human species.  In fact, it might be a Neanderthal after all – how?  David explains why.

At The Primate Diaries, Eric Michael Johnson discusses Cultural Transmission in Chimpanzees.  The origin, maintenance, and transmission of cultural traits in human populations is both a fascinating and difficult subject for anthropologists.  Though lacking obvious cultural traditions such as clothing or cuisine, nonhuman primates also have culture.  An example is the Kibale Forest chimpanzees, which use sticks to get at honey in fallen logs, while Budongo Forest chimpanzees use chewed leaves as sponges to collect the same thing.  Findings of a study to understand why some societies have more unique cultural traits than others, recently published in PLoS ONE, suggest this may have something to do with the number of females (with impressionable youngsters) present within a given society.

From Madeleine Begun Kane at Mad Kane’s Humor Blog comes this gem in her post, South African Pinot’s Too Pricey? Blame The Baboons:

Though South African wine can be fine,
There’s a threat to each grape growing vine.
Cuz baboons enjoy feeding
On grapes. Their fave eating
Is prized pinot noir — that’s the whine.

Adaptations

Jason Goldman at The Thoughtful Animal presents a post on a FIFTY YEAR LONG study of captive silver foxes in Russia in his post, The Russian Fox Study.  It is his favorite study of animals EVER, perhaps because the experimental foxes were more eager to hang out with humans, whimpered to attract attention, and sniffed and licked their caretakers. They wagged their tails when they were happy or excited.  Does that sound like Fido?

At Mauka to Makai, Kelsey Abbott discusses a male beetle (yeah, beetles!) with a penis so long and flexible that he has to sling it over his shoulder to keep it safe in her post Shouldering: Penis Extraction in Rove Beetles.  As titillating as it sounds, the post is really about the behavioral adaptations that this male rove beetle has employed to deal with such extreme genitalia.  The male is highly motivated (in the evolutionary sense) to follow a specific “penis extraction protocol” carefully, otherwise it will end up in a tangled mess (shudders!) and his chances with other ladies will be shot.

Zen Faulkes at NeuroDojo discusses a paper in PloS ONE by Sol et al. (2010) in his post Are big brains better for long trips? He notes that the authors found, as expected, that migratory birds tended to have smaller (and, thus, more energetically efficient) brains than non-migratory birds.  However, what is the direction of causality?  Read it and find out.

At Out walking the dog, Melissa Cooper discusses Mastodons in Manhattan: How the Honey locust Tree Got Its Spikes, noting that the formidible thorns of the honey locust tree are remnants of its co-evolution with giant herbivores – namely the browsing mastodons and woolly mammoths that roamed North America (including Manhattan) until somewhere between 6,000 and 11,000 years ago. The mastodons are gone, but the tree has not yet lost the adaptation, which now seemingly function only to puncture truck tires rather than deter proboscidean tongues.

Evolution of Sex

Genetic tests have revealed the secret sex life of a tiny poison dart frog species that lives in the Peruvian rain forests, GrrlScientist discusses at Living the Scientific Life in the post, Made for Each Other: Evolution of Monogamy in Poison Frogs.  Remarkably, it turns out that these frogs are monogamous, but the reason is surprising: it’s all about the size of the pools that their tadpoles mature in. This is the best evidence yet that just a single cause can affect evolution of a major life history trait, e.g. a species’ mating system.  GrrlScientist also discusses new research that shows evidence for cryptic mate choice in Gulf pipefish in her post, Size Matters — Bigger is Better, Even for Male Pipefish at Maniraptora: Tastes Like Chicken. This is supported by two observations. First, males that mate with larger (“more desirable”) females raise broods that have a higher survivorship. Second, embryo success in consecutive broods is negatively correlated. These observations show that males preferentially invest their limited resources into raising broods produced by “more desirable” females.

Microorganisms

At Skeptic Wonder, Psi Wavefunction recounts the excitement of getting to ramble on about protists for a whole twenty minutes in her post, Excavates and Rhizarians: A talk for phylogeny course.  Presentations on each taxon included!  She then admits a certain weakness for ciliates – not just for their insane cell and genomic organisation, or their bizzarely complicated morphology, or even their epi- and endosymbionts.  No, what really tickles her about this group is that many of them WALK!  See how in her post, Sunday Protist — Aspidisca: Walking ciliates with scrambled genomes

Shuna Gould at Lab Rat looks at the evolution of two-component sensor (TCS) systems in her post, How The Animal Lost Its Sensor, and discusses a few reasons why they may no longer be present in animals.  Widely used by bacteria to detect and respond to changes in both their outside and internal environments, but only nominally used by archaea and hardly at all by eukaryotes, it may be that TCSs originated in bacteria and spread by horizontal gene transfer to both archaea and eukaryotes.  Once eukaryotes developed a nuclear membrane, no further transfers took place, while in bacteria TCSs continued to diversify.

Biology

“There’s more to eggshells than meets the eye,” says GrrlScientist at Living the Scientific Life in her post, presents Ancient DNA Isolated from Fossil Eggshells May Provide Clues to Eggstinction of Giant Birds.  An international team of scientists just published a paper demonstrating for the first time that fossil eggshells are a rich source of ancient DNA.  Using a newly developed method, the team isolated ancient DNA from a 19,000-year-old emu eggshell, an extinct species of giant moa, the enigmatic elephant bird from Madagascar, and two other extinct species. However, attempts to isolate DNA from a 50,000-year-old flightless Australian Thunderbird failed because the DNA was too fragmented.  No – cloning these long-extinct birds is not likely.

Origins

At Evolving Thoughts, John Wilkins wonders how replicators  can evolve (replicators being genes, or if not then any part or section of a process that meets Dawkin’s criteria of longevity, fecundity and copying-fidelity) in his post, Thermodynamics, and the origin of replicators « Evolving Thoughts.  However, John takes exceptions with Dawkin’s view on the origin of replicators: “to posit that some molecule just acquired the capacity to replicate is to posit a scientific miracle. It’s a bit like suggesting that a molecule might just acquire the ability to act as a transistor. I do not like scientific miracles – they strike me as an admission of failure.”

Lucas at Thoughtomics admits he is an animal.  In his post, On the Origin of Animals, he discusses a Nature paper published last month by a team of researchers that used the conserved expression of mircoRNAs to piece together information about the most recent common ancestor of all Bilateria – the great-great grandmother of almost all animals, expected to have lived somewhere between 600 and 550 million years ago.  Since the evolution of Bilateria coincides with the evolution of many complex tissue types, microRNAs have the potential to be a great source of evidence for their evolution, and the team found microRNAs that were more or less specific for almost any tissue type present across the range of taxa studied.   Move over HOX genes!

Evolutionary Theory

With a book titled, What Darwin Got Wrong, it might surprise you to learn that lead author Jerry Foder is a teacher of philosophy and not evolution.  The premise of the book is that the “theory of natural selection” – as Foder calls it – cannot be true, but Bjørn Østman at Pleiotropy, in his post, The damned field of biology and the cursed theory of evolution, considers it to be nothing but “non peer-reviewed tripe”.  Listen to the hour-long interview with Foder if you don’t have time to read his book and decide for yourself.

In addition to her unicellular musings above, Psi Wavefunction at Skeptic Wonder also argues In defense of constructive neutral evolution – Part I.  This is the first of a 3-part post that addresses neutral evolution and its (mis)understanding compared to the flashier but probably overused explanations of adaptive evolution.  “In short, selection acts probabilistically, not absolutely”.

Population dynamics of cheaters are interesting, since cheaters generally benefit when their numbers are low but don’t when they become too numerous.  Lucas Brouwers at Thoughtomics discusses a paper that studied cheaters among bacteria in his post, Wolves, Bacteria and Cheaters.  Population dynamics between cheaters and cooperators are much easier to study in prokaryotes than in animals, since genes and molecules involved in the cooperative behaviour are more easily identified and manipulated.  Read what the authors of the study found…

At Culturing Science – biology as relevant to us earthly beings, Hannah Waters discusses two organisms that don’t fit into the 5-Kingdom classification that we all (at least the older among us) grew up with in her post, Photosynthetic Evolution: how 2 organisms gained or lost the ability to eat sunshine. The first is about microorganisms that were once photosynthetic — and thus evolved with the cyanobacteria and plants — but no longer go through photosynthesis.  The second is about a sea slug that has developed the ability to photosynthesize, or harvest energy from the sun.  Imagine the stories that all the other uncategorized protists out there have to tell!

At Deep Thoughts and Silliness, Bob O’Hara reviews a paper by Venditti et al. (2009, Nature) in his post, Branch Lengths and Species, that looks at the time between speciation events (i.e. the time a species spends as a single species, before it splits) as a way to infer something about the processes that lead to speciation.  The authors conclude that speciation is a random event: there is nothing intrinsic to the species (such as its age) that makes it more or less likely to speciate.  However, Bob has some methodological concerns about the paper – I’ll let him explain!

Alexander Bisignano at The Chromosome Chronicles discusses the potential that in silico models of evolution have over in vivo models in his post, Modeling Evolution in vitro and in silico.  In the computer, DNA can be substituted for by self replicating computer code that undergoes changes/rearrangement. Resources can be simulated by computer memory or RAM. The actions of competing and reproducing are executed by self-replicating code as they compete to take up more of the computer’s memory.  These in silico models of evolution allow for many generations to occur within a short period of time, thereby bypassing the main impediment to the study of in vivo models; however, whether these digital organisms are real beings will require more thought and ethical debate.

Eric Michael Johnson at The Primate Diaries discusses a paper by Harvard Medical School physician and researcher J. Wes Ulm that investigates the legacy of ideas that formed the basis of laissez-faire social Darwinism in his post, Social Darwinism and the “Cachet of the Cutthroat”. Despite their misuse by conservatives and economists for the past century and a half, Darwin’s ideas may be exactly what are needed to address some of our dire political and economic problems. 

Politics & Science

“Embargoes do not serve the best interests of science or scientists because they deny access to embargoed literature to those people — science blog writers — who are most likely to invest the greatest amount of time and energy into writing the story accurately and in an engaging way for the public,” says GrrlScientist at Living the Scientific Life in her post Goddam, But I Hate Embargoes.  “Since a fair number of science blog writers are scientists themselves, they have the knowledge to present these stories to the public and they also have a vested interest in making sure the science is being reported clearly and accurately. Even if embargoes are a necessary evil — and I remain unconvinced that they are — how they’re applied and dealt with is certainly not uniform, and pretending otherwise is just plain disingenuous.”

Announcements

GrrlScientist reminds us about her new twitter feed that announces science, environment, nature and medical blog carnivals to the public by providing links to the twitter feed and email for carnival hosts/managers to send URLs to.  She is seeking community comments for how to make this feed work most effectively for this community.

I hope you’ve enjoyed this edition of Carnival of Evolution. The May edition of will be hosted at Evolution: Education and Outreach – posts can be submitted using this handy blog carnival submission form.  You can find past issues at the home site and blog carnival index pageNOTE: hosts are needed for June and beyond – if you’ve never hosted a blog carnival, here’s your chance.  If you have, you know how to do it, so why not share your expertise.  Send an email to Bjørn if you’re interested.

Copyright © Ted C. MacRae 2010

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A “Really” Big-headed Tiger Beetle

Megacephala megacephala 3rd-instar larva. Photo © Artur M. Serrano.

In my recent summary of the latest issue of the journal Cicindela, I included a scan of the cover of that issue and its stunning image of the 3rd-instar larva of Megacephala megacephala¹ from Africa.  This otherwordly-looking, four-eyed beast was photographed with jaws agape at the entrance to its burrow in Guinea Bissau by Dr. Artur M. Serrano (University of Lisbon, Portugal).  I was grateful for his permission to post a scan of this spectacular image; however, he did even better and sent me high-resolution images of not only the larva (above) but the adult (below) as well.  This species is one of 13 assigned to the genus—presently restricted to Africa (though not always, see discussion below), where they are usually found in savanna-type habitats and are active during the crepuscular and nocturnal periods (Werner 2000).

¹ An example of a tautonym, i.e. a scientific binomen in which the genus and species names are identical. Familiar tautonymic binomina include the gorilla (Gorilla gorilla), green iguana (Iguana iguana), and European toad (Bufo bufo). Tautonyms are expressly prohibited in plant nomenclature (see Article 23.4 of the International Code of Botanical Nomenclature) but are permitted and, in fact, quite common in zoological nomenclature; Wikipedia lists 51 mammals, 82 birds, 15 reptiles & amphibians, 54 fish, and 33 invertebrates (though not Megacephala megacephla!).

Megacephala megacephala adult. Photo © Artur M. Serrano.

For those of you who see a strong resemblance by this species to another tiger beetle I featured recently, Tetracha floridana (Florida Metallic Tiger Beetle), this is not merely a coincidence.  Megacephala and Tetracha are quite closely related, and in fact the two genera, along with a handful of other closely related genera, are at the center of one of the longest-standing disputes in tiger beetle taxonomy (Huber 1994).  The genus Megacephala was established by Latreille (1802) for the species pictured here (originally described as Cicindela megacephala Olivier).  As additional taxa were found in Africa, Australia and the Western Hemisphere and assigned to Megacephala, several workers attempted to divide the genus into multiple genera (with New World taxa being assigned to Tetracha and a few other mostly South American genera); however, there was little agreement on how these genera should be defined and on what characters they should be based.  The debate was effectively swept under the rug in the early 20th Century when Walter Horn, one of the most influential cicindelophiles of all time, accepted a monotypic Aniara based on the strange South American species A. sepulcralis but reunited the world’s remaining taxa within the single genus Megacephala in his world catalogue (Horn 1910).  Horn’s use of Megacephala as a catch-all genus was followed by subsequent workers for almost a full century until Huber (1994) once again proposed restricting Megacephala to certain of the African species and resurrecting the genus Tetracha for the bulk of the New World fauna.  He also urged additional analyses to resolve the status of the remaining generic names and their composition, which subsequently saw increasing use as subgenera of Megacephala² and later as genera.

² Thus, as type-species for the genus, the species featured here became known as Megacephala (Megacephala) megacephala (Werner 2000)—a triple tautonym that translates to the “Big-headed, Big-Headed, Big-Headed” tiger beetle!  Perhaps it’s best that I’m not an African tiger beetle specialist; I probably would have been unable to resist the temptation to resurrect M. senegalensis and assign it as a subspecies of M. megacephala, just so I could refer to the nominate form as Megacephala (Megacephala) megacephala megacephala!

The reversal of Horn’s concepts now appears to be complete, with all seven former subgenera of Megacephala formally being accorded full generic status (Naviaux 2007). This classification is strongly supported by molecular analysis of nuclear 18S and mitochondrial 16S and cytochrome oxidase gene sequences (Zerm et al. 2007), with the resulting dendrogram indicating three monophyletic clades corresponding to the African/Palearctic (Megacephala and Grammognatha, respectively),  Western Hemisphere (Aniara, Metriocheila, Phaeoxantha and Tetracha) and Australian (Australicapitona and Pseudotetracha) genera³.  The African/Palearctic clade was found to occupy a basal position in the tree, while the Western Hemisphere and Australian clades were more derived.  These data support the hypothesis that the early evolution of the megacephalines took place during the break-up of the ancient Gondwana megacontinent, which began about 167 million years ago (middle Jurassic period) and sequentially disconnected Africa from South America and Australia.

³ One striking deviation from the current classification, however, was the support for nesting the single Aniara species within Tetracha, a placement that renders Tetracha paraphyletic and, thus, requires either its division into multiple genera or the sinking of Aniara as a distinct genus. The support for this placement was quite strong and mirrored the results of a broader molecular phylogenetic study of tiger beetles based on full-length 18s RNA data (Galian et al. 2002). The authors concede that this puzzling placement is not corroborated by numerous morphological, ecological and ethological characters that distinguish Aniara from all known Tetracha species.

REFERENCES

Galián J., J. E. Hogan and A. P. Vogler. 2002. The origin of multiple sex chromosomes in tiger beetles. Molecular Biology and Evolution 19:1792–1796.

Horn, W.  1910.  Coleoptera Adephaga, Fam. Carabidae, Subfam. Cicindelinae.  In P. Wytsman (editor).  Genera Insectorum.  Fascicle 82a.  Desmet-Vereneuil, Brussels, Belgium, pp. 105–208.

Huber, R. L.  1994.  A new species of Tetracha from the west coast of Venezuela, with comments on genus-level nomenclature (Coleoptera: Cicindelidae).  Cicindela 26(3/4):49–75.

Latreille, P. A. 1802. Histoire Naturelle, Générale et Particulière des Crustacés et des Insectes. Paris: F. Dufart 3 xii 13 + 467 pp.

Naviaux R. 2007. Tetracha (Coleoptera, Cicindelidae, Megacephalina): Revision du genre et descriptions de nouveaus taxons. Mémoires de la Société entomologique de France 7:1–197.

Werner, K.  2000.  The Tiger Beetles of Africa (Coleoptera: Cicindelidae).  Volume 1.  Taita Publishers, Hradec Kralove, Czech Republic, 191 pp., 745 figures.

Zerm, M., J. Wiesner, J. Ledezma, D. Brzoska, U. Drechsel, A. C. Cicchino, J. P. Rodríguez, L. Martinsen, J. Adis and L. Bachmann.  2007.  Molecular phylogeny of Megacephalina Horn 1910 tiger beetles (Coleoptera: Cicindelidae).  Studies on Neotropical Fauna and Environment 42(3):211–219.

Copyright © Ted C. MacRae 2009

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Ship-timber beetle

Atractocerus brevicornis

One of the more unusual, and enigmatic, beetles that I encountered in South Africa was this beetle in the pantropical genus Atractocerus.  Placed in the family Lymexylidae (ship-timber beetles), species in this genus look less like beetles than they do large flying ants or strange damselflies due to their highly reduced elytra that expose their greatly elongated abdomen and leave the hind wings uncovered.  The hind wings also are unusual in that they are held fan-like in repose rather than folded as in most other beetles.  Atractocerus brevicornis is the only species in the genus found in Africa (Scholtz & Holm 1985).

Adults are attracted to light at night, as was this individual that came to our ultraviolet light at Geelhoutbos farm below the Waterberg Range in Limpopo Province. Nothing is known about the biology of Atractocerus, but larvae of other genera are reported to bore into hardwoods and palm stems (Picker et al. 2002). Larvae of the genera Lymexylon and Melittomma are believed to form symbiotic associations with ambrosia fungi that grow on the walls of their galleries (Young, 2002).  Adult females deposit fungal spores in a sticky matrix when they lay their eggs, and the hatching larvae carry the spores into wood on their bodies.  The large eyes of Atractocerus, however, suggest a predatory lifestyle. The common name of the family originates from a northern European species that has in the past been a destructive pest of ship timbers.

Atractocerus species are rarely encountered and therefore, not well studied. Their evolutionary history is still unknown; however, the oldest known lymexylid fossil is a very primitive member of the genus Atractocerus preserved in 100 myo Burmese amber (Grimwold & Engel 2005). Thus, the lineage containing these beetles had already appeared by the mid-Cretaceous and may have originated as early as the Jurassic, a fact that has earned them the moniker “living fossils.” These beetles were once thought to be among the most primitive of all Coleoptera – their simple wing venation, almost undifferentiated antennae and tarsi, and naked abdomen being likened to a supposed neuropteran common ancestor. Most authors now consider the family to be most closely related to the cucujiform groups Cleroidea and Cucujoidea (Wheeler 1986, Young 2002), although some have placed it in the Elateriformia near the Lampyridae based on wing venation. Scholtz and Holm (1985) accepted a cucujiform placement but related the group to the Styopidae (twisted-winged parasites), apparently due to the similarity of their highly reduced forwings.  At the same time, they acknowledged the many morphological and behavioral differences between the two groups, the latter itself being the subject of much evolutionary debate due to disagreement about whether the reduced forwings of male stylopids are truly homologous to the elytra of Coleoptera (some have even suggested homology with the halteres of Diptera that were switched from the metathorax to the mesothorax as a result of homeotic mutation). Most authors now place this latter group in the separate order Strepsiptera.

REFERENCES:

Grimaldi, D. and M. S. Engel. 2005. Evolution of the Insects. Cambridge University Press, New York, xv + 755 pp.

Picker, M., C. Griffiths and A. Weaving. 2002. Field Guide to Insects of South Africa. Struik Publishers, Cape Town, 444 pp.

Scholtz, C. H. and E. Holm (eds.). 1985. Insects of Southern Africa. Butterworths, Durbin, South Africa, 502 pp.

Wheeler, Q. D. 1986. Revision of the genera of Lymexylidae (Coleoptera: Cucujiformia). Bulletin of the American Museum of Natural History 183:113-210.

Young, D. K.  2002. 71. Lymexylidae Fleming 1821, pp. 261-262.  In: R. H. Arnett and M. C. Thomas [eds.], American Beetles, Volume 2, Polyphaga: Scarabaeoidea Through Curculionoidea, CRC Press, Boca Raton,880 pp.

Copyright © Ted C. MacRae 2009

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