Did you know that bees evolved from within a group of solitary, carnivorous wasps, approximately 120 million years ago? Today, pollinivory – the consumption of pollen – is a defining feature of bees (aptly named Anthophila; the flower lovers).
In this study, one of the core concepts is the role of the ‘key innovations’ underlying biodiversity patterns. A key innovation is an evolutionary novelty which is believed to contribute to the success of a group. (For example, across all insects, some of the major transitions that are hypothesized to be key innovations include the origin of wings/flight, and the origin of complete metamorphosis.)
Under the traditional definition of innovation, we would predict that a lineage with the key trait is more speciose than related groups lacking this key trait. The switch to pollen feeding has been assumed to be a key innovation of bees: the bees arose from within a group of carnivorous wasps, were able to exploit a new food resource, and today are extremely species rich.
Our finding that not all bees exhibit a high diversification rate challenges conventional thought that the switch to pollinivory is directly responsible for increased bee diversity. We found that some of the earliest-originating bees did not partake in the diversification upswing. These results indicate that pollen feeding was an important evolutionary switch, but does not fully explain the diversity we see today. We postulate that other complementary innovations, such as a generalist host-plant diet, influenced the tremendous diversification of the major bee lineages.
On a broader scale, this study contributes to an area of interest in the insect scientific community, of investigating whether diet shifts to plant-feeding contribute to higher diversity. Pollinivory is a specialized form of herbivory. Classic and contemporary studies have found a general pattern across insects that herbivory increases diversification (i.e., Mitter et al. 1988 & Wiens et al. 2015). We found that the evolutionary shift to plant-feeding contributed to bee diversification, but our results indicate it is not directly responsible for the increase in diversification rates.
The Cornell Chronicle published an article on our paper!
Read it here: Study Challenges Widely Held Assumption of Bee Evolution.
citation: Murray, E.A. Bossert, S., Danforth, B.N. (2018) Pollinivory and the diversification dynamics of bees. Biology Letters, 14, 20180530. DOI: 10.1098/rsbl.2018.0530
The fossil that was thought to be the oldest flying insect (and has been used to interpret and date the origins of flight) may not even be an insect at all! In an interesting turn, a recent publication asserts that the fossil Rhyniognatha hirsti is not the mandible of a flying insect, but is in fact a fragment of a myriapod: specifically, an immature centipede.
In an article published May 30, 2017 in the journal PeerJ, Haug & Haug present evidence that the Devonian fossil R. hirsti (>400 My old) is not a flying insect... or an insect... or even closely related to insects... It is a centipede. The fossil is fragmentary, mainly mandibles and some other rather ambiguous parts connected to it. However, the shape of these mandibles was similar to those of dragonflies and neopterans, which prompted Engel and Grimaldi (2004) to tentatively assign it as a fragment of a flying insect. Now, Haug & Haug use 3D imaging and show remains of what they hypothesize is a myriapod-like head capsule. Also, the putative apodemes are deemed to be glands of ectodermal origin.
The potential misplacement of this fossil has some pretty big implications. The next oldest fossils of flying insects are from the late Carboniferous -- about 80 My after this fossil! That is a huge time difference and affects our interpretation of the origins and evolution of insect flight. Also, many molecular phylogenetic studies have used this as a fossil calibration. For instance, the hexapod dated phylogeny of Misof et al. 2014 incorporated this fossil as a stem calibration for Dicondylia (winged insects + their sister group Diplura), with an age of 411.5 Mya. The reinterpretation of this fossil, if it is accepted, will have wide effects on future work on insect evolution and dating.
As of September 23, there were ~1500 views of the article and no papers citing it, so we'll have to stay tuned for a response!
Engel, M.S. & Grimaldi, D. (2004) New light shed on the oldest insect. Nature 427, 627-630.
Haug, C. & Haug, J.T. (2017) The presumed oldest flying insect: more likely a myriapod? PeerJ, 5, e3402.
Misof, B., Liu, S., et al. (2014) Phylogenomics resolves the timing and pattern of insect evolution. Science, 346, 763-767.
Each year at EvoDay there is a mix of faculty, researchers, postdocs, and grad students who give ~20 minute presentations at the event, addressing an audience of about 100 people. Past themes have been 'Evolution and Conservation' (2016) and 'Evolution and Behavior' (2015).
This year, our aculeate working group was well-represented, as both Bonnie Blaimer (Smithsonian) and I presented our latest work based on phylogenies constructed from ultraconserved elements (UCEs).
Have you heard of 'The Amphioxus Song'? The song is an ode to the lowly lancelet (another name for this organism). Amphioxi are heralded due to their similarity to early chordates, exhibiting characters showing evolutionary development to the vertebrates.
Evolution vs. Creationism. It's a book. And, engendering this interesting read, evolution vs. creationism is still a hot topic and source for controversy in communities across America. Accepting evolution isn't a question for most scientists (~98% accept it), but it is an ongoing debate in the public realm, especially in the context of teaching it in schools.
This post was inspired by "Evolution vs. Creationism: An Introduction" (Scott, 2009). I'd recommend this book to anyone looking to learn about the evolution controversy in America and gain insight on the historical development of the creationist and intelligent design movements. The book: part 1= science, religion, evolution, and creationism; part 2= a history of the creationism/evolution controversy; part 3= excerpts from the literature -- nicely organized with a topic summary and a point-counterpoint format.
What is the distinction in the different types of evolutionism?
Theistic, agnostic, and materialist evolutionists. Members of all categories accept evolution as operating under natural laws of nature. Theistic evolutionists -- for instance, Catholics and mainstream Protestants -- are those who hold belief in a higher being who is involved at some level in the course of evolution. Agnostics are uncertain about the reality of God, but aren't too dogmatic about their beliefs. Materialist evolutionists include humanists and atheists, who believe supernatural forces do not exist.
Scientists can accept evolution yet still hold religious beliefs.
Scientists can be methodologically naturalistic evolutionists who are concurrently theists. Put simply, this means they carry out their research under the assumption that answers can only come from the material, natural world. This applies to both origin science (singular events) and operation science (recurring events tested by experimentation). The supernatural cannot be invoked, because if non-testable, supernatural forces are allowed, then the work would no longer be in the realm of science.
teaching evolution in grades K-12
The book shines in its detail of judicial rulings that have led up to our states' current laws on teaching evolution in the classroom. Here's how it brings a recent South Dakota bill (SB 55) into context.
Senate Bill 55 (link to South Dakota legislature site)
Purpose: protect the teaching of certain scientific information.
Content: "No teacher may be prohibited from helping students understand, analyze, critique, or review in an objective scientific manner the strengths and weaknesses of scientific information presented in courses being taught which are aligned with the content standards established pursuant to § 13-3-48" [state code governing state education standards revision cycle & contents].
Status: bill has passed the Senate and has gone to the House. Currently deferred until Feb. 13, 2017.
Status update [Feb 17]: after being deferred again, it's been scheduled for hearing on Feb. 22.
Status update [Feb 22]: the bill has been defeated.
On Feb 22, a motion was passed (11-4-0) to defer SB 55 to the 41st Legislative Day. Because there are only 40 legislative days this year, this effectively kills the bill. Some opponents of the bill were listed on the South Dakota legislative website. Among others, they included representatives from the SD school board, the Sierra Club, and the Presentation Sisters (nuns with a mission in education).
So why is there concern over this bill? The wording makes it sound like a good thing. And maybe the intention is noble. But, from previous rulings on intelligent design and the evolution curriculum, there is precedence demonstrating how a judge may determine that the bill is actually meant to weaken science instruction, not strengthen it.
Historical background: In America, we have a tradition of free speech. We also have a decentralized educational system, and a decentralized religious history which has contributed to a theological divide in regional churches. State legislatures repeatedly introduce laws requiring evolution is taught with caveats, such as putting 'warning' stickers on textbooks or giving equal time to intelligent design.
A few court cases:
The famous 1935 Scopes Monkey Trial in Dayton, Tennessee pitted the fundamentalist William Jennings Bryan against Clarence Darrow, who was defending John T. Scopes for teaching evolution in the public schools. Scopes lost. Antievolution laws remained. The amount of evolution in textbooks decreased for the next two decades and conflicts ensued when evolution was revived in the 1950's.
A landmark ruling was the Supreme Court case Lemon v. Kurtzman 1971, which all creationism cases since have cited. It applies a three-part test to determine if the law violates the Establishment Clause of the First Amendment. To wit, a bill must have a secular purpose, must not either promote or inhibit religion, and must not create undue entanglement between government and religion.
The 1980's saw the onslaught of equal time legislation in 27 states; bills that required equal time to be given to evolution and creationism. Only two states passed them into law -- Arkansas and Louisiana -- and both were eventually overturned (McLean v. Arkansas and Edwards v. Aguillard). McLean declared that creation science failed as a science, and Edwards ruled on the Establishment Clause. However, Edwards suggested loopholes, recognizing that teachers could "supplant the present science curriculum with the presentation of theories, besides evolution, about the origin of life."
More recently, a case in Pennsylvania: Kitzmiller v. Dover 2005. A policy was introduced by the school board that would require that teachers read a disclaimer about "Darwin's Theory of Evolution" and state that it is not a fact, and students must be instructed to "keep an open mind". Teachers must also have the intelligent design textbook, "Of Pandas and People" available for students to reference. In the end, Judge Jones gave a complete victory to the plaintiffs and declared Dover's educational policies to be unconstitutional. However, Kitzmiller is not precedential outside of its district.
Returning to the bill at hand, we can use these cases to adduce how the South Dakota Senate Bill 55 could be construed as antievolution (or, antiscience).
Again, the bill: "No teacher may be prohibited from helping students understand, analyze, critique, or review in an objective scientific manner the strengths and weaknesses of scientific information presented in courses being taught ..."
The book "Evolution vs. Creationism" illuminated these arguments. I hope I've shed some light on why there is concern over SB 55, and how the important goal of instilling critical thinking skills in children may in actuality be language used with the intention to promote intelligent design and encourage an antievolution message.
Creationist Graffiti? A recent trip to a state park in Ithaca showed someone had decided to revise geologic history. The "past two million years" was replaced with "past many years" and the age when the glaciers melted was altered from 12,000 to 4,000 years ago, presumably because the earth could not be over 12,000 years old.
reference: Scott, E. C. (2009). Evolution vs. creationism: An introduction (Vol. 62). Univ of California Press.
Covering topics of phylogenetics and systematics.