Photo Credit: Howard Falcon-Lang, Royal Holloway University of London

What you are looking at here is the oldest fossil evidence of the genus Pinus. Now, conifers have been around a long time. I mean really long. Recognizable members of this group first came onto the scene sometime during the late Triassic, some 235 million years ago. Today, one of the most species-rich genera of conifers are those in the genus Pinus. They dominate northern hemisphere forests and can be found growing in dry soils throughout the globe. For such a commonly encountered group, their origins have remained a bit of a mystery.

The fossil was discovered in Nova Scotia, Canada. Unlike the rocky fossils we normally think of, this fossil was preserved as charcoal, undoubtedly thanks to a forest fire. The degree of preservation in this charcoal specimen is astounding and provides ample opportunity for close investigation.

I mentioned that this fossil is old. Indeed it is. It dates back roughly 133 –140 million years, which places it in the lower Cretaceous. What is remarkable is that it predates the previous record holder by something like 11 million years. Even more remarkable, however, is what this tiny fossil can tell us about the ecology of Pinus at that time.

Firstly, the leaf scars indicate that this tree had two needles per fascicle. This implies that the genus Pinus had already undergone quite the adaptive radiation by this time. If this is the case, it pushes back the clock on pine evolution even earlier. Another interesting feature are the presence of resin ducts. In extant species, these ducts secrete highly flammable terpenes, which would have potentially promoted fire.

Species that exhibit this morphology today often utilize an ecology that promotes devastating crown fires that clear the land of competition for their seedlings. Although more evidence is needed to confirm this, it nonetheless suggests that such fire adaptations in pines were already shaping the landscape of the Cretaceous period. All in all, this fossil is a reminder that big things often come in small packages.

Photo Credit: Howard Falcon-Lang, Royal Holloway University of London

Further Reading:

http://bit.ly/1QP85zm

Photo by Petr Kosina licensed under CC BY-NC 2.0

What you are looking at here is not just a pile of discarded leaves. It is indeed a living plant. Would you believe me if I told you that it is a distant relative of pines, spruces, larches and firs? It's true! This right here is Welwitschia mirabilis, a representative of an ancient lineage of gymnosperm!

Welwitschia is endemic to the Namib Desert of Africa. It is hard to picture any plant living in such a dry area. In some years it never even rains. Welwitschia persists despite this fact. It tends to grow in watercourses and outcrops, thus enabling it to gather what precious little rain does fall. It has a deep taproot suggesting that it relies heavily on ground water. The leaves of Welwitschia also have high amounts of stomata on both surfaces enabling it to absorb water directly from the fog that regularly blows through when colder air currents mix with hot air from the desert.

For a long time it was believed that Welwitschia represented true neoteny, which is the retention of juvenile characteristics into adulthood. It was thought that Welwitschia was nothing more than a sexually mature seedling with exaggerated cotyledons. This idea was later abandoned when Martens showed that Welwitschia do develop further than the seedling stage. What really happens is the apical bud, which is responsible for vertical growth in plants, dies quite early on in development. In essence, Welwitschia has lost its "head."

I was not kidding when I said that Welwitschia is a gymnosperm. Once sexual maturity is reached, cones are produced. Individual plants are either male or female and unlike many of its relatives, Welwitschia is not wind pollenated. Instead it relies on insects to transfer pollen from male cones to female cones.

Probably the most remarkable aspect of Welwitschia ecology is its longevity. Individual plants can live well over 1000 years. Some individuals are estimated at around 2000 years old! In such a harsh desert environment, persistence is the key to survival for Welwitschia.

Photo Credit: Petr Kosina

Further Reading:
http://www.jstor.org/discover/10.2307/2442386…

http://www.plantzafrica.com/plantwxyz/welwitschia.htm