ferns

Kingdom: Plantae 

     Phylum: Streptophyta (Charophyte green algae & all land plants)

          Class: Equisetopsida (spore-bearing vascular plants)

Ferns are vascular plants that reproduce via spores.  Ferns puzzled early botanists by their lack of seeds or flowers until Wilhelm Hofmeist discovered spores and a unique reproductive strategy of alternating generations.  Spores are cells that can form a new individual without fusing to another reproductive cell.  Their life cycle includes a short gametophyte stage and a longer sporophyte stage.  This is in contrast to the first land plants, the Bryophytes, which have a long gametophyte stage and a transient sporophyte stage in the life cycle.  As a retired reproductive endocrinologist, I was fascinated to learn that some mature ferns exist in haploid or polypoid states. It has been speculated that the ability to undergo polypoidy may be one of ways that ferns respond to environmental stress. 

Evolutionarily, ferns were one or the first vascular plants to emerge on land and after surviving at least four mass extinction events, they are still the second most diverse group of vascular plants on earth, comprising 3 subclasses, 4 orders, >48 families, >319 genera and >12,000 species. Many ferns are tropical. However, ferns have adapted to every continent on earth except for Antarctica. Identifying ferns can be daunting so learning how to identify which genus a fern falls into is a big step towards understanding fern taxonomy.

If Earth's 4.55-billion-year history is compressed into a 24-hour period, the first fossil records of ferns date to about 10:06 PM during the Devonian period.  However, most living ferns today belong to the Order Polypodiales, which developed during the early Cretaceous period around 11:20 pm on the 24-hour clock.  Our human ancestors don't appear until the last minute of this 24-hour Earth history day.

The earth is entering a mass extinction event associated with climate change, which has spurred a global interest in phenology. Phenology is the study of the calendar of life, i.e. when birds migrate, when flowers bloom, etc. Ecosystems are interdependent species of plants, animals, ... that co-evolved into interdependent phenological matches. What we call native species are those that represent this phenological matching. For example, the simultaneous appearance of certain bees and flowers represent a phenological match. Climate change has the potential to shift phenological events and if they occur at different rates, may lead to phenological mismatches. Phenological mismatches have the potential to trigger extinction events within existing ecosystems and spark shifts towards completely different ecosystems. Life always finds a way to adapt to the detriment of some species and the benefit of others. Human activity is contributing to climate change in ways that may threaten our own well-being. Interestingly, we have the ability as citizen scientists to document these ecological shifts. Within the plant world, phenological databases are set up to annotate flowering plants. This may be shortsighted as spore-bearing plants were among the first to evolve and have survived the greatest number of mass extinction events. Walmer Woodlands has therefore initiated a pilot study in partnership with the NC Botanical Garden to demonstrate the value of annotating the phenology of spore-bearing plants. Click here to learn more about this pilot study.

Here is a list of ferns that are growing in Walmer Woodlands.

The American Fern Society also has an excellent page About Ferns