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April 26, 2013

Eukaryote origins, cicadas, and silkworm sex

Gene similarity networks provide tools for understanding eukaryote origins and evolution
"multiple signatures of the chimerical origin of Eukaryotes as a fusion of an archaebacterium and a eubacterium that could not have been observed using phylogenetic trees... archaebacterial repertoire has a similar size in all eukaryotic genomes whereas the number of eubacterium-derived genes is much more variable"

Independent divergence of 13- and 17-y life cycles among three periodical cicada lineages "at any given location, up to three distinct species groups (Decim, Cassini, Decula) with synchronized life cycles are involved... life-cycle synchronization of invading congeners to a dominant resident population enabled escape from predation" [OK, but why not 7 and 11 years?]

Transgene-based, female-specific lethality system for genetic sexing of the silkworm, Bombyx mori

Neo-sex chromosomes and adaptive potential in tortricid pests "fusion between an ancestral Z [sex] chromosome and an autosome corresponding to chromosome 15 in the Bombyx mori reference genome... conferring insecticide resistance and clusters of genes involved in detoxification of plant secondary metabolites under sex-linked inheritance"

April 17, 2013

High-school student undermines our "famine-food longevity" hypothesis, maybe

Back in 2009, I suggested that, to the extent that organic foods provide greater health benefits, this might be due to tradeoffs with reproduction. See my original post for a more-detailed explanation. Since then, I've seen at least one paper on a diet that increases both longevity and reproduction in some species, but there were no data on the timing of reproduction, which is key to our hypothesis.

This week, however, high school student Ria Chhabra and colleagues published a paper in PLoS One reporting both greater longevity and increased egg-laying at all ages, in fruit flies fed various organic foods. It's not inconceivable that some conventionally-grown produce could be so poor, nutritionally, that it would reduce both lifespan and reproduction. But their data seem inconsistent with our hypothesis that organic-vs-conventional differences were mainly differences in toxins (synthetic in conventional, natural in organic) and that natural toxins mainly acted as environmental cues, switching physiology towards longevity at the expense of reproduction.

I'd like to see this experiment repeated by a different lab, however, before drawing firm conclusions. There are a couple of strange things in their data. First, as noted in the paper, survival curves for Drosophila are usually sigmoidal, whereas theirs are more linear. Also, their peak egg-laying rate was reportedly at an age of 1 day. Other studies I've seen show essentially no egg-laying that early, with peaks at day 5 or so. See this paper or this open-access one.

April 15, 2013

YouTube videos go fungal...

...or whatever we call over 100 but fewer than 1000 views.

This page has links to an interview Michael Joyce did with me at the end of my week-long visit to the International Rice Research Institute, as well as the five lectures I gave there (plus audience questions and discussion).

Also still available are:
* a 60-second AAAS story on my most-cited paper.
* a video of my keynote talk at the Applied Evolution Summit
* a lower-quality video of a talk on Evolutionary Tradeoffs as Agricultural Opportunities
* an audio interview with science writer Carl Zimmer

Or, you can find an updated list of my publications, with links to many of them, here.

April 12, 2013

This week's picks

Here are some papers that look interesting this week. See also my Darwinian Agriculture blog

Stable isotope evidence of meat eating and hunting specialization in adult male chimpanzees "sex differences in food acquisition and consumption may have persisted throughout hominin evolution, rather than being a recent development"

New World cattle show ancestry from multiple independent domestication events "pre-Columbian introgression of genes from African cattle into southern Europe"

Key role for a glutathione transferase in multiple-herbicide resistance in grass weeds "When the black-grass A. myosuroides (Am) AmGSTF1 was expressed in Arabidopsis thaliana, the transgenic plants acquired resistance to multiple herbicides"

Potential shortfall of pyramided transgenic cotton for insect resistance management "results from 21 selection experiments with eight species of lepidopteran pests indicates that some cross-resistance typically occurs between Cry1A and Cry2A toxins."

The Upper Limb of Australopithecus sediba "use of the forelimb primarily for prehension and manipulation appears to arise later, likely with the emergence of Homo erectus" [There are several articles on A. sediba in this issue.]

Achieving the triple bottom line in the face of inherent trade-offs among social equity, economic return, and conservation "three very different case studies in California (United States), Raja Ampat (Indonesia), and the wider Coral Triangle region (Southeast Asia). We show that equity tends to trade off nonlinearly with the potential to achieve conservation objectives, such that similar conservation outcomes can be possible with greater equity, to a point."

Decreased water flowing from a forest amended with calcium silicate "An unexpected outcome of the Ca amendment was a change in watershed hydrology; annual evapotranspiration increased by 25%, 18%, and 19%, respectively, for the 3 y following treatment before returning to pretreatment levels. "

Responses of Mn2+ speciation in Deinococcus radiodurans and Escherichia coli to γ-radiation by advanced paramagnetic resonance "extreme radiation resistance of D. radiodurans cells cannot be attributed to SodA"

April 8, 2013

Fake journals and conferences in NYT

Conferences that invite people at random, for money, are bad enough. Those that mimic real conferences are worse. The New York Times reports that people signed up for Entomology-2013, sponsored by "The OMICS Group", mistaking it for the scientific-society-sponsored Entomology 2013. I've discussed this problem before. The NYT article also discusses fake "scientific journals" that publish garbage for money. Since real journals vary in quality, and many charge authors for some of the cost of publication, it may sometimes be hard for people outside the field to tell the difference.

Real scientists publish in journals with scientific-sounding names, but publication in a scientific-sounding journal is no guarantee that the conclusions are correct or that the author is a real expert.

April 5, 2013

Tradeoff-free longevity?

I have argued that understanding evolutionary tradeoffs is key to improving agriculture and increasing longevity.

For example, in 2009 I discussed a paper showing that food deprivation extends lifespan of C. elegans nematode worms by delaying their reproduction. I've seen other papers claiming to extend lifespan without reducing reproduction, but those papers have ignored possible effects on timing of reproduction. In a growing population, reproducing later reduces fitness, because your offspring are added to a larger gene pool. On the other hand, if the population is decreasing...

But a recent paper in PNAS reports that chemicals called ascorides (thought to be used as a crowding cue) increase the lifespan of C. elegans, without an apparent reproductive cost. Treated animals produced at least as many offspring as controls, at all ages. I don't understand this result. If there's no tradeoff, why haven't they evolved to turn on this response all the time, even without the crowding cue?

In humans, though, "Exceptional longevity is associated with decreased reproduction." That was the conclusion of a 2011 paper. They found that Ashkenazi Jewish centenarians (average age ~100 years) averaged 2.0 children, while a control group (parents of their children's spouses and friends, who died in their 70's) averaged 2.5 children. The centenarians also reproduced later in life (28-32 vs. 26-30). So, is it worth having 0.5 fewer children, to live 30 more years? Natural selection apparently doesn't think so.

April 2, 2013

Carnival of Evolution

Interesting stuff at Synthetic Daisys, but links would be good!