One cautionary note with this study is that the methods employed (ancestral character evolution) do not permit the inference of trait values that fall outside of the observed range of extant variation. Adding fossils can significantly improve our estimates of the root state but unfortunately in this case there don't seem to be many fossil flowers to parameterize the model.

There's been instances where using only data from extant species can mislead with respect to the hypothesized ancestral state. For one example, see figure 5 in http://onlinelibrary.wiley.com/doi/10.1111/j.1558-5646.2012....

Recently I found TimeTree (http://www.timetree.org/). The tool produces both timelines and timetrees (ancestry) of taxonomies. Both tools provide a nice context of the evolutionary environment. If you click through enough, you can usually get to the underlying research for the data as well.

Try searching for taxons Spermatophyta (seed plants) and Magnoliophyta (flowering plants) and to see the common ancestor of flowering plants.

Isn't there some kind of egg/chicken (flower/insect) problem here? What's the evolutionary benefit of developing a flower unless insects also develop the eyesight and coordination necessary to find nectar in the flower?

* Not all flowers rely on insects for pollination, or any pollinators at all. Many are wind-pollinated or self-pollinating (not that the basal lineage would be asexual).

* Insects do not necessarily rely on eyesight for pollination. Scent, for instance, is a strong attractant.

* Insects need only be driven by a search for food for pollination to work. There is no requirement that they have specialized adaptations for nectar-gathering. Elaborate floral structures that require these adaptations evolved over time, along with their pollinators.

* One common flaw in evolutionary/adaptive thinking is assuming that efficient solutions must be present from the outset of an adaptive trait. Incidental effects that provide only the slightest increase in fitness can easily be fixed in a population.

Most importantly, though, this is really an investigation about structure. This is a common theme in plant development; many plant structures are highly analogous. Understanding the basal state of floral structures informs studies one the gene regulatory networks that control plant shape. For some context, I'd take a look at the well-characterized MADS-box genes. https://en.wikipedia.org/wiki/ABC_model_of_flower_developmen...

I think you're mostly listing ways that both insect and flower could survive before they both developed specific adaptations that aid in their mutual interaction. But I feel like the more satisfying answer is that very gradual changes in both species can eventually lead to two species that appear to be extremely codependent.

In this case, I would guess that even the tiniest proto-flowers that resulted from random mutations could just so happen to be discovered by insects with the tiniest random mutations that led them there.

Not really. Some plants reproduce via wind action. The original "flower" might not have looked much like a flower - it might simply have been a receptacle to catch pollen blowing in on the wind and/or a location where pollen was produced.

At that point anything that happened to brush past could pickup pollen then accidentally deposit it in a female flower somewhere else. Even a tiny advantage would escalate. You can imagine things like nectar originally being an accidental thinning of cell walls, allowing sap (or the equivalent) to leak out inside the flower purely as a side-effect of the flower's development. Attracting insects would be a further accidental side-effect but a beneficial one.

I'm not saying this is how flowers and pollenating insects evolved, merely that there are plenty of plausible scenarios that require nothing but random chance and the re-purposing of existing structures.

A failure of human imagination is no argument against evolution.

There seems to be no chicken/egg problem here. Insects, and specifically the spore-feeding ones as well as the flying ones appeared before flowers. Once we have the picture of insects gliding/flying from cone to cone feeding on the spores - flower+nectar comes as an obvious evolution.

IANAB. It's weird that it's so complex. I was expecting something very simple like https://en.wikipedia.org/wiki/Bougainvillea https://www.google.com/search?q=Bougainvillea+flower&tbm=isc... that has only three petals that look like colored leaves.

This isn't the 'first flower'. This is the first flower that is the most recent common ancestor of all flowering plants. There are a lot of more primitive flowers that lead up to this which are also common ancestors, but not the most recent, as well as a lot of dead ends that didn't leave any ancestors.

if you compare it to a gymnosperm (the dominant plants before angiosperms), like, say, the structure of a pine cone but unfolded/unwrapped a bit, the reconstruction in this paper may seem more obvious.