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Far away from the pressures and established order of continents, on islands the initial species that colonize can proliferate and radiate to fill niches that otherwise are occupied by other organisms. A species blown onto an island can seed the new lands with hundreds of potential radiations with bizarre and wonderful forms. Like many other archipelagos across the world, the Mossfells are no strangers to this phenomenon.
However, before the story of current life begins, we must go back to the beginning. The Mossfell Islands emerged roughly 22.1 million years off the coast of North America. Since then it has experienced several waves of colonization from the mainland. The fossil record for the initial period of colonization is unfortunately scarce. The rapid and gradual erosion of the islands has destroyed many of the earliest remains, while the acidic volcanic soils often did not provide organic tissues the precise conditions for preservation. Instead, researchers must often use techniques such as molecular paleontology and phylogenetic analysis to determine how and when endemic island species diversified from mainland relatives. Thankfully the few fossils found in lava tubes and volcanic caves have been relatively well preserved. Due to these techniques, we have been able to determine what species first arrived to the islands and the subsequent patterns of colonization.
A few members of the initial wave of colonists to the Mossfells. Top Center: a basal cardinal, Top Left: a basal finch, Top Right: a neotropical parrot, Center: an ancestral snapping turtle, Bottom Left: a pond slider, Bottom Center: a blue-tailed skink
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The (Estimated) First Wave
During the first few million years, the islands were colonized by little more than hardy mosses, grasses, and seabirds. Once these first plants created primordial soils there came larger weeds such as dandelions, clovers, and ragweed. Further along came trees such as mulberries, palmettos, mangroves, and pines. Around 15.4 million years ago, the Lonely Bob seamount was a flourishing and vibrant island. Further along the volcanic chain, the emergent scrub slopes of Nishsystir started to become pleasant plains.
It was during this time period (20.1-15.4 mya) that several bird species colonized the islands. This was spearheaded by the aforementioned seabirds such as gulls, frigate birds, and plovers. Aside from a few lineages, these seabirds largely remained tied to the coast and did not radiate into inland niches. Another group of birds that colonized the islands at this time were wayward Passeriformes - also known as songbirds. They quickly adapted to the growing forests on the islands. With bountiful resources, many began to shed their ability to fly and became ground-dwelling. Others gained accessible prey and became fearsome mesopredators.
Birds were not the only organisms to gain a foothold during this first wave. Many reptiles found great success at colonizing the early islands. Snapping turtles, pond sliders, and skinks all arrived around 17 million years ago. These reptiles would quickly diversify over a variety of habitats on the islands from rocky crevasses to the coral lagoons. Like the birds before them, many grew to immense sizes.
Lastly, many insect species likely made their way to the islands around this time such as cicadas, grasshoppers, various varieties of fruit flies, sand fleas, and bumble bees. The first wave ended roughly around the Middle-Miocene disruption with the introduction of true parrots (Psittaciformes) to the islands. Genetic analysis performed on Carolina Parakeet specimens indicates that parrots likely arrived on the islands later than other bird species, roughly around 14.1 million years ago.
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The Second Wave
The second wave occurred as the earth began a transition to a much colder world. Roughly 11 million years ago, the Islands of St. James and St. Anne had ceased volcanism and both Tyrkimani and Neffannafjall were volcanic hotspots. During this time, water levels began to drop between islands. This resulted in species which had developed in relative isolation from each other to interacting and competing with one another. These new interactions, combined with a change in climate, spelled disaster for several lineages of birds and reptiles. This would pale in comparison to the impact the latest group of colonists would have.
The oldest mammalian fossils, found in lava tubes on St. James islands, have been dated as far back as 10.6 million years ago. These were determined to be microbats related to little brown bats. These ancestors quickly established themselves as nighttime predators, similar to their mainland cousins, but would eventually radiate into a surprising amount of niches. Quickly afterwards, two archaic mammalian families - the opossums and solenodons - found themselves established on the islands. Likely castaways from coastal forests of North America and the Caribbean, scant fossil evidence on St. Anne indicates that it didn't take long for these mammals to make short work of many endemic reptiles and flightless birds. It is likely the arrival of mammals 10 million years ago robbed much of the fauna on the Mossfells of their expected island tameness. As the climate chilled and tropical weather gave way to boreal forests, mammals quickly gained an advantage over reptiles across the islands from steppe mountains to cold-weather bogs.
Finally, the last large group of animals to arrive were wayward ground sloths at the start of the Pliocene. Due to their exceptional swimming skills these giants were quickly able to colonize the archipelago. However due to environmental constrains they quickly lost their immense sizes.
Mammalian members of the second wave to the Mossfells. Top: the ground sloth Megalonyx, Left: a microbat relative of the little brown bat, Right: a slender solenodon, Bottom: a Virginia opossum.
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The Third Wave?
Throughout the last 12,000 years many new plant and animal colonists have found their way to the Mossfells. While human colonists have had a presence (albeit a sporadic one) on the Mossfell Islands, not all of these new colonists owe their presence to human settlement. Based on archeological evidence, the Shearpoint culture is thought to have introduced crops such as maize, squash, and beans around 10,000 years ago along with turkeys and beach mice. After their disappearance many other birds such as Canada geese, blue herons, and red tail hawks all found themselves on the islands.
With the arrival of the Norse in the 11th century, many domesticated and potentially invasive species were introduced such as Norway rats, dogs, pigs, cats, and sheep. Crops such as wheat and barely also were brought over. Into the modern day, many more species have found their way to the island, most of which were brought deliberately as pets or game. These include Roe deer, red foxes, alligators, wallabies, racoons, squirrels, and pigeons. Almost all of the newest arrivals of this "Third Wave" have cause incredible harm to the existing flora and fauna. It is very likely that if these new arrivals are not controlled, irreparable damage to the existing ecosystems of the Mossfells will be the end result.
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