A Flower Trapped in Amber

Photo by George Poinar [SOURCE]

Thanks to a 30 year old collection of amber tucked away in the drawers of a museum, we now have the first fossil record of the asterid lineage. Discovered in the Dominican Republic back in 1986, this particular chunk of amber contains a tiny flower about a centimeter in length. The preservation is astounding, allowing researchers to accurately identify this as a member of the genus Strychnos.

The asterid lineage contains many orders that we would be familiar with including Gentianales, Lamiales and Solanales. It is highly derived yet poorly represented in the fossil record. Because of the challenges associated with accurately dating amber, scientists estimate that this flower is somewhere between 15 - 45 million years old. To put this in perspective, North and South America were not even connected at this point in time. What's more, the details preserved in these amber deposits are allowing researchers to piece together what the forest in this region would have looked like.

These fossils show that this forest "contained a distinct canopy layer composed of legumes such as algarroba (Hymenaea protera), cativo (Prioria spp.) and nazareno (Peltogyne spp.), with emergent trees like caoba (Swietenia; Meliaceae) extending through the canopy. The subcanopy and understory were represented by royal palms (Roystonea) and figs (Ficus; Moraceae). The shrub layer included other types of palms as well as acacias. Grasses like pega-lega (Pharus) and bambusoids (Alarista) colonized the forest floor. Orchids, bromeliads, ferns and vines covered the trees, and various lianas were also part of this tropical forest."

Pretty amazing for bits and pieces of solidified tree sap. This particular flower has been named Strychnos electri, a now extinct species. However, the morphological characteristics show that this particular genus as well as the asterid lineage were already well established at this time. Discoveries such as this are offering highly detailed windows into the past, which allows us to better understand flowering plant evolution and ecosystem change.

Photo Credit: George Poinar

Further Reading:
http://www.nature.com/articles/nplants20165

Carnivores in Amber

Carnivorous leaves from Eocene Baltic amber. (A) Overview of the leaf enclosed in amber showing the adaxial tentacle-free side in slightly oblique view and stalked glands at the margin and on the abaxial side; arrowhead points to the exceptional long tentacle stalk with several branched oak trichomes attached. (B) Overview of the leaf enclosed in amber, showing abundant tentacles on the abaxial side. (C) Margin of abaxial leaf surface with tentacles of different size classes and nonglandular trichomes [SOURCE]

Carnivorous plants are marvels of evolution. Adapting to nutrient poor conditions, these botanical curiosities have evolved myriad ways of capturing and digesting prey. For all of their extant diversity, the fossil record of carnivorous plants over the eons is pretty much non existent save for some highly contentious fossils from China as well as some fossilized seeds of the aquatic carnivore, Aldrovanda. However, a recent discovery out of Russia changes everything. Beautifully preserved in amber, we now have the first conclusive fossil evidence of a carnivorous plant.

The amber was found in a mine in Russia and is estimated to be between 35 and 47 million years old, during an epoch known as the Eocene. Inside are beautifully preserved leaves of what seems to be a species of Roridula. The leaves clearly show specialized stalked glands with a pore at the tip. The researchers who discovered the amber also found evidence of the sticky secretions that were used to capture its prey.

Overviews showing the tentacle-free adaxial surface and tentacles along the leaf margins (B & C). (D) Partial leaf tip showing different size classes of stalked glands. [SOURCE]

The resemblance of these leaves to the leaves of extant Roridula is uncanny. Modern Roridula do not directly digest their prey. Instead, they rely on a symbiotic relationship between a species of bug, which lives on the leaves without getting stuck. The bugs hunt down and eat trapped insects. As they eat, the bugs defecate and it is their nitrogen-rich feces that the plants absorb for sustenance. It is quite possible that the fossilized Roridula also relied on these insects as well, though no direct evidence of this was found. 

The most interesting aspect of this discovery is its location. Today, Roridula is found only in South Africa. Its presence in Russia hints at a historic distribution that is much wider than previously thought. It has long been assumed that Roridula is a neoendemic to South Africa, with the family having arisen there and nowhere else. This discovery now shows Roridula to be a paleoendemic, once having a much wider distribution but currently restricted to South Africa. This discovery is an excitingly huge step in our understanding of carnivorous plant evolution. 

Morphological comparison of the carnivorous leaf fossils from Baltic amber (Left) and extant Roridula species (Right). (A and B) Leaf tip ending in a sole tentacle. (C and D) Stalked glands of different size classes. (E and F) Hyaline unicellular nonglandular trichomes. (G and H) Epidermal cells and stomata. (I–L) Multicellulartentacles. (A, C, E, and G) (I and J). (B, D, K, and L) R. gorgonias. [SOURCE]

Photo Credit: Alexander R. Schmidt, University of Göttingen

Further Reading: [1]