Joshua trees at LiveScience

Over at LiveScience, my collaborator Chris Smith describes the research we've done so far on the interaction between Joshua trees and their pollinators:

First, the match between the Joshua tree flowers and the moths' ovipositors suggested that coevolution might have molded the relationship between the plant and the pollinator. Second, because the plants are completely dependent on the moths for reproduction, the differences in the flowers might have caused Joshua trees to split into two different species.

Yucca brevifolia in Tikaboo Valley, Nevada. Photo by jby.

Pollination before flowers

Which came first, the pollinator or the pollinated? An article in this week's Science suggests that a diverse group of insects may have been drinking nectar and pollinating plants millions of years before the appearance of modern flowering plants [$-a].

Panorpis communis, a modern scorpionfly species, and a sketch of ancient, pollinating scorpionflies. Photo by JR Guillaumin; sketch from Ollerton and Coulthard (2009).

Prior to the origins of modern flowering plants, or angiosperms, in the early-middle Cretaceous period, most of the diversity of land plants were gymnosperms. These plants are characterized by "naked seeds" -- reproductive organs exposed to the air, where the wind can catch pollen and carry it from one plant to fertilize the ovules of another. In a world dominated by gymnosperms, the thinking used to be, animal pollinators were mostly unnecessary.

The new paper by Ren et al. challenges this idea with the description of a set of fossilized scorpionflies, all of which have strikingly long probosces that are clearly suited to sucking up liquid. The earliest of these fossils are from the Jurassic, tens of millions of years before the flowering plants began to diversify. In modern insects, sucking mouthparts like the ones described are associated with two kinds of feeding: drinking pollen, and drinking blood. To determine which was most likely in this case, Ren et al. performed energy-dispersive spectroscopy on the best-preserved fossil, and found no sign of the elevated levels of iron in the proboscis that would result from the residue of blood meals. This suggests that the scorpionflies were drinking nectar, or something like it.

Nectar has one major function in plants: to attract insects. Ant-protected plants reward their ants with nectar, and flowering plants use nectar to lure animal pollinators close enough to pick up or drop off pollen. If these ancient scorpionflies were, in fact, living on nectar, Ren et al. reason they were probably pollinating contemporary plants, which were all gymnosperms. The authors identify a diverse list of candidate host plants, including seed ferns and a relative of the modern ginkgo, whose reproductive structures were (1) too well-sheltered for efficient wind pollination or (2) included tubular structures similar to those that modern plants use to guide nectar-feeding pollinators. Finally, the authors point out, many modern gymnosperms produce "ovular secretions" that are very similar to the nectar produced by angiosperms.

As a neontologist, I'm often amazed how much can be told from million-years-old fossils -- who knew there was a way to test for residual blood in a fossilized proboscis? At the same time, Ren et al. connect some mighty scattered dots to build their hypothesis. The real clincher is that it seems mighty unlikely that animal pollination would be rare in a world that already has both flying insects and pollen-producing plants. Animal pollination is much more efficient than wind pollination, and if there's one constant in evolutionary history, it's that living things rarely miss an opportunity like that.

References

Ollerton, J., & Coulthard, E. (2009). Evolution of animal pollination. Science, 326 (5954), 808-9 DOI: 10.1126/science.1181154

Ren, D., Labandeira, C., Santiago-Blay, J., Rasnitsyn, A., Shih, C., Bashkuev, A., Logan, M., Hotton, C., & Dilcher, D. (2009). A probable pollination mode before angiosperms: Eurasian, long-proboscid scorpionflies. Science, 326 (5954), 840-7 DOI: 10.1126/science.1178338

Invasive species not so bad?

Over on Slate, Rebecca Tuhus-Dubrow says some conservation biologists are starting to question the importance of preventing species invasions:

Certainly, they say, non-native plants and critters can be terribly destructive—the tree-killing gypsy moth comes to mind. Yet natives such as the Southern Pine Beetle can cause similar harm. The effects of exotics on biodiversity are mixed. Their entry into a region may reduce indigenous populations, but they're not likely to cause any extinctions (at least on continents and in oceans—lakes and islands are more vulnerable). Since the arrival of Europeans in the New World, hundreds of imports have flourished in their new environments.

Tuhus-Dubrow cites the case of Tamarisk in the U.S. Southwest -- an aggressive introduced shrub that has also ended up providing important nesting sites for the endangered southwestern willow flycatcher.

The fact of the matter is that human-introduced species can eventually integrate into an ecological community; once they do it's hard to get them out, and problematic as to whether it's a good idea. In Australia, dingoes helped extirpate many other large predators when they were introduced by the first humans to arrive on that continent -- and now they're critical to controlling other, later-introduced mammal species.

(Thanks to Ephraim Zimmerman for point this one out to me!)

Invasive pest, or critical flycatcher habitat? Maybe both. Photo by Anita363.

Defense, or Social Security?

Mike Konczal considers the effect of breaking Defense Department spending out as a separate line item on pay stub tax witholding statements, alongside Social Security and Medicare. If citizens saw a number for military alongside social spending, they might make more informed choices about the relative values of each.

How much of your two weeks work cycle would you like to spend working to keep a global military hegemony going? I’d probably want to clock it out around my first coffee break on Monday (which is fairly early), but that’s me.

Some pacifists withhold a portion (or all) of their Federal taxes in protest against military spending, and there's even a campaign to let people opt out of funding the military on their tax forms. Maybe Konczal's idea would be a good alternative?

"France's answer to James Bond"

Shades of Clouseau, but this still looks like I'd enjoy it way too much.



DVD on Amazon

Carnival of Evolution #17 at Adaptive Complexity

Over at Adaptive Complexity, Michael White has just compiled the 17th monthly Carnival of Evolution. Marking the 150th anniversary of the publication of The Origin of Species (November, 1859), Michael structures submitted posts into a "virtual voyage of the Beagle." Topics range from the sexual habits of our ape-like ancestors* to a highly optimistic study predicting that the frequency of the creationist meme in the United States will drop to 0% by 2050.

* Which habits might, I think, explain why we never invite them round to tea.

Berry Go Round #21 at Beetles in the Bush

Ted MacRae has a fine round-up* for the 21st monthly Berry Go Round, the bontanical blog carnival. And he notes that BGR needs a badge. Must ... resist ... urge ... to spend afternoon futzing with Inkscape.

Photo by jby.

*Including a set of nested footnotes that would make David Foster Wallace blush.