EcoVentures Travel
Safaris and nature tours for discriminating individuals

Arrival and Establishment of Species

We will never know exactly how colonization occurred, such events do not leave any records, but we may speculate about what probably happened.

The ancestors of every plant and animal species on the islands must have arrived from some other part of the world. A thousand kilometers of ocean separate the Galapagos from the mainland. Despite this barrier, a large number of species arrived to the islands. Oceanic volcanic islands such as the Galapagos differ from continental islands in that they never had contact with continental landmasses so any plant or animal now native to the Galapagos must have arrived to the islands from the mainland. These organisms not only survived a hazardous journey and thrived in an unfamiliar environment, but were also able to reproduce successfully, and colonize the islands.

The question that once perplexed biologists was how so many venturesome vagabond species could survive the long journey to the Islands, when many others would surely have perished on their way. Exceptional hardships must have been overcome.

Nonetheless, close scrutiny of the original flora and fauna of remote islands suggests that they were indeed derived by chance from mainland colonies; this is also known as “random dispersal”.

Flotation rafts made of mats of vegetation or other debris, even winds and jet streams could have been some of the means for transporting living organisms or seeds to the newly formed islands.Birds displaced from their traditional migratory routes, or seeds and invertebrates traveling on the feathers and feet of aquatic and semi-aquatic birds, are also considered to be means of transportation.

Of course, species are present in proportion not only to their capacity to disperse, whether actively or passively, but also to their ability to establish themselves after arrival. The need for an appropriate mate in sexually reproducing animals, or a compatible pollinator in out - crossing plants, posed a great challenge for long-term establishment.


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Evolution

The Galapagos islands have often been called “a laboratory of evolution”. There are few places in the world where it is possible to find such an inmense variety of species, both plant and animal, that shows so many degrees of evolutionary changes in such a restricted area.

Once organisms reach oceanic islands they are basically isolated from other landmasses.

If the islands are distant enough from a source, then the colonization of the islands may be considered an almost independent biological unit.

Oceanic islands can have species, which though related to mainland forms, have evolved in different ways from their mainland relatives as a result of their isolation in a different environment. This is a key factor in the island’s evolution.

It is not surprising that Charles Darwin was so struck by the life he found on these islands. Darwin’s Natural Selection is a process by which propagation is converted into change, and species diverge one from the other.

A classic example of adaptive radiation in birds is found in Darwin's finches, which has served generations of evolutionary biologists. A total of 13 species evolved within the Galapagos’ archipelago from a common ancestor whose founding type and source from the American continent has yet to be identified. A single fourteenth species occurs on Cocos Island off Costa Rica, about five hundred miles northeast of the Galapagos. All the finches are closely related and presumably evolved from the same progenitor stock; this is indicated by characteristics shared by all. The word “endemic” refers to organisms, which are found nowhere else in the world due to the fact that they have evolved and remained isolated on a given area and have therefore developed unique characteristics. You will find several species that fall into this classification in the Galapagos.

“Considering the small size of the islands we are surprised by the endless number of native species and their confined range”
Charles Darwin, The voyage of the Beagle.

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Geology of the Islands

The Archipelago is located on the NASCAR Plate, close to the junction with the Cocos Plate. As a result of the spreading of the sea floor (the movement of plates in relation to each other) along the Galapagos Rift and the East Pacific Rise, the islands are moving south and eastbound at a rate of more than 7 cm a year, which may not seem significant but would, over a million years, amount to a slide of 70 km.

Evidence that the plate on which the islands sit is moving eastward lies in that the oldest islands are located in the eastern part of the archipelago. All the volcanic activity that has occurred recently is located in the Western Islands. The “Hotspot Theory” states that in certain places around the earth, there are stationary areas where there is intense heat in the mantle. These hotspots cause the crust to melt in certain places and give rise to volcanoes.

The Galapagos and Hawaii Islands have had mild volcanic eruptions, where volcanic material comes out gently to form large lava rivers instead of explosions.

We could even say that atmospheric erosion hasn’t had time to shape the volcanoes. The lava layers are intact. Nothing seems to be altered either by the sea, wind, or sand.

There isn’t a more attractive place for scientists, researchers, biologists and botanists, than this Archipelago where it’s possible to find life and its millenarian evolution in a primitive state, almost intact and untouched by man.
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Marine Currents and Weather

The Galápagos Islands are situated on the Equatorial line and are exposed to the influence of ocean currents that shape the archipelago’s temperatures.

The climate is pleasant any time of the year and has two defined seasons:

• From June to November: a dry and cool season (average temperatures of 20 degrees centigrade during the day) where mist – a type of rain – is usual. It is the best season to see marine birds nesting.

• From December to May: the hot and humid season (with average temperatures of 28 degrees centigrades) where the tropical heat is moderated by winds from the Pacific. This season is especially favorable for watching marine tortoises and to go diving and snorkeling.

The humidity that evaporates from the sea is concentrated in a inversion layer (300 to 600m above the sea level) and the highest parts of the islands intercepts this layer receive a precipitation in a drizzle form meanwhile the areas above the sea level maintain dry but fresh.

January May: during the warm season southeast winds diminish their strength and warmer waters from the Gulf of Panama are flowing through the islands. The average temperature rises to 25 ° C (77 degrees F). The warmer waters caused the change of season and the archipelago is experiences a tropical climate with blue skies and occasional heavy rains.

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Coastal zone
This zone is always green. It is important to note the ability of some species to tolerate salt, especially the ones located on the border between the sea and land. The type of vegetation in this zone is very diverse. Mangroves are found within the forests and the coves, while vines, weeds, and shrubs, are present on the beaches.