Fern evolution, new study

This 10 October 2014 video from the USA says about itself:

Digging for Fern Fossils: Saint Clair, Pennsylvania

Collecting Carboniferous fossil plant specimens at an old coal strip mine in PA.

Another video used to say about itself:

Immortalized Fossil Fern Reveals Evolutionary Standstill

A remarkably preserved, 180-million-year-old fossilized fern has been unearthed in Sweden.

The fern was in such pristine condition that its tiny cellular parts were intact, according to a study detailed today (March 20 2017) in the journal Science.

And it turns out, not much has changed for the family of ferns in the last 180 million years.

“The genome size of these reputed living fossils has remained unchanged over at least 180 million years — a paramount example of evolutionary stasis,” the authors wrote in the paper.

Ferns are some of the most primeval plants; they first appeared in the fossil record nearly 360 million years ago. But many modern ferns got their start in the Cretaceous Period, when flowering plants emerged.

The newfound Jurassic Period fossil fern was uncovered in Korsaröd, Sweden, in a bed of volcanic rock. The specimen, which measures 2.3 inches (5.8 centimeters) long and 1.6 inches (4.1 cm) wide, was so exquisitely preserved that its cytoplasm (the gel-like substance that fills a cell), nuclei and chromosomes were still intact and visible under a microscope. The plant cells were in different stages of cell division.

The fossilized plant was likely preserved when minerals in the superheated, salty water oozing from a crack in the earth, called a hydrothermal brine seep, rapidly crystallized, freezing the plant in time while it was still alive.

By measuring the delicate subcellular parts, the team found the nuclei of the ancient plants were virtually the same size as those in a modern living relative, Osmundastrum cinnamomeum, or the cinnamon fern. The number of chromosomes and the DNA content also seemed to match closely with the modern fern.

The findings suggest this ancient fern hasn’t lost or gained much genetic material over the last 180 million years, a remarkably long period to go without much evolutionary change, the authors wrote.

According to Live Science.

From the University of Turku in Finland:

Fern fossil data clarifies origination and extinction of species

July 6, 2017

Throughout the history of life, new groups of species have flourished at the expense of earlier ones and global biodiversity has varied dramatically over geologic time. A new study led by the University of Turku, Finland, shows that completely different factors regulate the rise and fall of species.

“Previously, the debate has been about whether biodiversity is regulated mainly by the interaction between species or the external environment,” explains researcher and leader of the study Samuli Lehtonen from the Biodiversity Unit of the University of Turku.

In order to test these competing views, Lehtonen compiled a group of top researchers from Finland, Sweden, Switzerland and the United States. The researchers focused on the diversity of ferns and the factors that influenced it during the past 400 million years. Ferns have survived no less than four mass extinctions and during their extremely long evolutionary history, the dominant fern groups have changed repeatedly.”

“Thanks to the rich fern fossil data and a large amount of DNA information from living species, we were able to test multiple competing evolutionary models for the first time by using new analytical methods,” says Professor Alexandre Antonelli from the Gothenburg Global Biodiversity Centre (GGBC) who participated in the study.

The observed variation in the fern diversity was compared with the variation in other groups of plants and in the environment, such as continental drift and climate changes. The results show that changes in the environment strongly influence extinctions but surprisingly not the origination of new diversity. Instead, the formation of new fern species is accelerated when the fern diversity is low (e.g. after mass extinctions). The study suggests that origination of new species is mainly a neutral process in which the probability of speciation increases when diversity is low.

“Factors affecting extinction and origination of species are surprisingly different, with past climate change having the highest impact on extinction but not on originations,” notes researcher Daniele Silvestro from the GGBC who developed the mathematical model used in the study.

The old competing hypotheses seem to explain different sides of the same problem, making arguing about them pointless, unless extinctions and originations are studied separately.

With crowdfunded support, researchers have sequenced the first two fern genomes ever. Their results include the discovery of an ancient gene transfer and novel symbiosis mechanisms: here.

A tiny fern — with each leaf the size of a gnat — may provide global impact for sinking atmospheric carbon dioxide, fixing nitrogen in agriculture and shooing pesky insects from crops. The fern’s full genome has now been sequenced: here.