Unveiling the Mysteries of the Enchanted Island - Essay Example

Unveiling the mysteries of the enchanted island “It is not the strongest of the species that survives, or the most intelligent, but the one most responsive to change.” When I read this quote I am sure that 99% of you know who I am talking about and how important that person is. The reason why I am giving this example is that it’s so simple yet the significance is so much greater. I embarked on this incredible journey and my aim was to experience the islands like he did, through his eyes. But many years have passed since his first visit to the islands and we can definitely see the changes of the flora and the fauna and how these changes had an impact on the Archipelagos. Ever since this incredible land was discovered, it has captured the imagination of many. The unique and exotic inhabitants of the island have always mesmerized me. In this document I have endeavored to present an in-depth understanding of the ecosystem of the Galapagos Islands. By the end of this presentation you will have a clear idea about the ecosystem of the Islands and also about flora and the fauna that thrives there. I have documented the necessity for adaptation for the floral and the faunal populations of the islands, their interactions and adaptations. I shall also discuss about the geological formations, introduction and negative impacts of invasive species on the synchronized equilibrium of the Galapagos ecosystem. I consider myself qualified to present such an important documentation to you because, with the help of professional tour guides, I have gained a broad understanding of the culture of Ecuador and they provided me the chance of successfully immerging myself in to their culture. Experiencing the islands from such a close distance, my attention was immediately drawn towards its ecosystem and its plight which lured me to conduct an in-depth research on the issue. I gained a complete understanding of the ecosystem and the threat posed by the invasive species that have been introduced in the islands. I consider that it is necessary for me to share this information with my audience because of the simple fact that they need to understand that there are very fragile and sacred environments in this planet that are worth fighting for. The Galapagos have been a conceptual landmark since its discovery and continues to grant us insight into concepts of evolutionary biology. The true essence of these islands lies in their biodiversity which is under threat; however, researchers believe that Galapagos is standing at cross roads and though the degradation rate is increasing, but with an in-depth understanding of the need for conservation, the biodiversity of the Islands can be restored. I want everyone to appreciate such rare beauty and protect them from further harm and help them maintain their integrity and identity without losing a single species in the process. My central idea is to show the importance of adaptation that occurs in both flora and fauna of the islands and how outside factors can affect the ecology such as geological formations or invasive species. ECOSYSTEM OF THE GALAPAGOS ISLANDS The ecosystem of the Galapagos is among the best studied ecosystems in the world. According to some, the Galapagos Islands are among the most spectacular scientific discoveries. The place was colonized by humans only recently, thus the biodiversity of the Galapagos is still intact .The Galápagos is today one of the best-preserved oceanic archipelagos, where human impacts on many ecological processes are still relatively low (Thornton 1971).Though at present times the Islands are facing a certain extent of degradation which may be replaced via prompt action. It is indeed noticeable that the flora and fauna is impoverished and there is not much variety. The islands provide a fine example of how external factors play a role in evolution of the flora and the fauna that inhabit the Islands. The unique features of the Galapagos are a result of the following factors- geologically new, presence of active volcanoes and successful arrival and establishment of few living species. The flora of the islands closely resembles the flora of the South American mainland from where most plant is believed to have originated. At present there are 560 native plant species that thrive on the island. Out of these about 180 species are endemic. At the species level the plant endemnicity is 32% (Lawesson et al. 1987). These native species came to the islands by natural means such as- floating in the oceans, dispersal through air or by birds. These hardy plants that manage to successfully cross the oceans and establish themselves in the island often had to do so in hostile environment and this led to adaptation in the plants for survival purposes. The plants are found on the 4 universally recognized levels of vegetation in the Islands - (Littoral, Dry, Transition and Humid ) which is believed to have been formed owing to the high precipitation on the southern slopes owing to presence of prevailing winds throughout the year. The Littoral zone is present near the coastal regions and has beaches and brackish lagoons. The mangrove trees (Rhizophora mangle, Avicennia germinans, and Laguncularia racemosa) are predominant in the littoral region, while on the slightly drier regions of these zones bushes and grasses that can tolerate salt, thrive. Some of the smaller Islands of the Galapagos are covered entirely by this zone alone. The dry zone is widely distributed in many of the Islands. The zone lies on the northern rain showed portion of the peaks. The only trees that thrive on the dry zone are the cactus plants (Opuntia spp, Jasminocereus thouarsii and Brachycereus nesioticus). Next is the transition zone which receives slightly higher amounts of rain and consists of plant species from both Dry zone and the humid zone. The Humid zone is so named owing to its high humidity. This Humid zone is again divided into sub-categories depending on the rainfall, altitude and soil. The sub-categories are- Scalesia forest (dominated by Scalesia trees), Miconia and Pampa zone (dominated by ferns and sedges). Only the 7 major high Islands of the Galapagos have all of the 4 described zones. The present biodiversity in each of the vegetation zones have adapted to the climatic variations which has resulted in an uneven distribution of plants and vegetation (native, endemic and introduced). The arid zone, characterized by exceptionally dry conditions punctuated by wet El Nino events, hosts the majority of the endemic plants. About 67% of endemic vascular plants are found in this region. Rainfall is lowest on the coast and increases with altitude, especially on the southern slopes of the highest islands (Tye et al. 2002). A total of seven genera of vascular plants are present on the Islands. These plants were isolated from the mainland and had evolved with completely different characteristics to adapt themselves to their new environment. The seven genera are-Darwiniothamnus, Lecocarpus, Macraea, and Scalesia (Asteraceae family), Brachycereus and Jasminocereus (Cactaceae family) and Sicyocaulis (Cucurbitaceae family) Asteraceae form the largest part of the vegetation and are the biggest native plant family. Genus Scalesia is considered as the “Darwin’s finches of the plant world” because they provide a spectacular example for adaptive radiation because about 15 species of this genera are present in different ecological niches on the same Island and differing in growth habits, growth height and multiformity of the leaves. Like the Scalesia genus plants, cacti belonging to the Opuntia genus have also undergone adaptation. Botanists found the presence two absolutely different types of prickly pear cactuses in the Island- the smaller frutescent Opuntia (occurring on smaller islands) and arborescent forms (up to 12 m in height). Opuntia galapageia, Opuntia megasperma and Opuntia saxicola are arborescent while Opuntia insularis and Opuntia helleri are frutescent. Besides endemic Opuntia, researchers have found two more endemic cactus species- Jasminocereus thouarsii and Brachycereus nesioticus. Brachycereus is a pioneer plant that grows on lava. The fauna present on the Island is defined by the flora present. The Galapagos have rich fauna and in terms of numbers of species (1900 native species), invertebrates represent most of the natural terrestrial biodiversity of Galapagos (Peck 1997). The age of the fauna on the islands dates back to 3-4 Ma during the existence of the islands. Genetic studies on the Galapagos and the land iguanas have shown divergence somewhere lesser than 10 Ma. A taxonomical study conducted on the insect population in the Island revealed that out of the 1822 insect species widely available on the land, 1530 are native, 712 are endemic while the rest are introduced. The wide number of endemic insect genera suggests that these insects have been separated from their mainland ancestors for a very long time. The older islands among the Galapagos Espanola and San Cristobal have more endemic insects. Most insects have undergone speciation owing to change of environment and habitat. Some insects have shown loss of eyes and gain in appendage length. Parapatric speciation is noticeable in lycosid spiders, Pterostichus beetles and other cave dwelling insects. The beetle belonging to genus Stomion adapted and diversifies both within and in-between the Galapagos Islands. With the help of molecular morphogeny it has been established that there is a variety of cave-dwelling and non-cave dwelling population among the Stomion genus of beetles. Bulimulidae is a snail species which is represented by 65 different species in the Galapagos and is a great example of speciation. The snail fauna of the Islands is quite impressive. It consists of 83 indigenous species of which 80 species of snails are endemic to the region. Terrestrial arthropods are found in the arid lowland regions of the islands. Among the non-insect endemic species present on the island, Giant tortoise is perhaps, the most popular, and at present, there are 11 subspecies (compared to previously 14 sub-species) that have adapted to the Island environment. These Giant tortoises are closely related to the smaller bodied tortoises that live in South America (Geochelone chilensis). Researchers believe that the tortoises came to the island (Cristobal and Espanola) by clinging onto driftwood along the Pacific coast and then spread to other Islands. The divergence between the two species- C.chilensis and C.nigra took place some 6-12 million years ago. These tortoises then radiated and adapted to different living conditions in different islands of the Galapagos group of Islands or different parts of an island. Those isolated on one island further sub-divided into more species by restricting flow of gene and adapting to local environmental conditions. In fact there are 4 variations of the same tortoise species in Isabela Islands whose taxonomic relation have been derives using mitochondrial DNA. The tortoises inhabiting each island are different from one another on the basis of their carapace shape. The tortoises with dome shaped carapace are mostly found in those islands that have highlands where there is abundant food to support them while saddleback tortoises are found on the lower regions where vegetation is sparse. Their shell allows them to reach up to the sparse vegetation. Another important endemic species is the iguanas. It is believed that the ancestors of these iguanas originated in either Central or South America and must have been carried to the Islands by strong ocean currents. Even these Iguanas had to adapt to their new environment by changing their eating habits. The Island is home to 19 different bird species of which 50% are endemic and 25% are exclusive to the Galapagos. Most of these birds are migratory and had made their way into the land from Ecuador or Peru. Perhaps the most important example of adaptation in birds is that of the well-known Darwin’s finches and mockingbirds who radiated into several sub-species, however several other birds like cormorants, boobies, penguins and gulls are present. Researchers believe that the flightless cormorants lost its wings through adaptation since there was no predators on the island before, hence the birds did not need their wings to fly. Gradually, their wings became smaller and vestigial. The flightless penguins present in these islands have beaks that are much thinner and different from their counterparts- Magellanic penguins The marine life of the Galapagos is also exotic. The combination of warm tropical water along with the cool waters bought in by the ocean current allows these islands to harbor a great variety of ocean life; however, as a result of the cold waters corals are few. Reefs are present some of the islands. These waters are home to sharks, sea lions, penguins, and seal and to about 306 species of fishes out of which 25% are endemic. The endemic species of fishes are mostly small fishes that prefer to live near the shore. These include blennies, stargazers, drums and brotulas. The presence of the exotic and endemic marine iguana is another unique feature. Hundreds of species of mollusks inhabit the islands and about 185 of the shallow water mollusks are endemic. The interaction between the flora and the fauna present in the islands is extremely important for survival of the involved species. Plants being sessile need to disperse their seeds in order to ensure seed survival and establishment as adult plants. Dispersal interaction is absolutely essential to maintain the biogeography and encourage evolution of the biodiversity in these Islands. Seed dispersal allows plants to occupy newly available niches, avoid competition, find suitable physical conditions for the germination of seeds, expand their area of distribution, and escape high mortality rates close to the parent plant due to shading or a high abundance of natural enemies (Janzen 1971).Most plants like those belonging to Asteraceae, who previously depended on wind dispersal, produced showy ray florets as an adaptation to attract pollinators. These plants depend on the birds and the reptiles of the island for seed dispersal, while the frugivore faunal population depends on the plants for food source. A vivid example of co-evolution is offered by the cactus plants and Darwin’s finches. Prickly pears form the staple diet of the finches which in turn help in the dispersal of seeds. Nectar and kernels of the cacti provide nutrition to the plant. The size and hardness on the cactus fruits on which the finches depend on for food and the shape and hardness of their beaks have evolved simultaneously. The herbivore and the competitive interaction among the herbivores was a direct result of the radiation adaptation of the cactus and also on availability of food resources. The giant tortoises with high vaulted carapaces could feed on the cacti, utilizing their long necks. In fact even Darwin himself while on his visit to this group of islands reported the interaction between the different vegetation with the Giant tortoises. He reported that the tortoises that lived on islands with little or no water and with limited amount of food fed on cactuses while those tortoises living on higher grounds where there is enough water and food sources fed on grasses, berries and lichen. This shows adaptive interaction between the flora and the fauna. The process of evolution is very delicate and the phrase “survival of the fittest” can be best described on these islands. Geological formations for example play a big role in the process of growth and evolution. GEOLOGICAL FORMATIONS AND CONSEQUENT ADAPTATIONS Similar to all other Archipelagos of the world, the Galapagos too, are of volcanic origin; however it is the youngest Archipelago. In fact the oldest islands are not more than 5 million years old. Thirteen major lands and hundreds of rocky outcropping make up the Galapagos Islands. Each of the Islands is a result of a volcanic eruption except for Isabela Island which is a result of six volcanic activities. Most of the Galapagos Islands lie on the Nazca plate. The islands like most mid-ocean islands are made up of Basalt. At present the Nazca plate is drifting in the southern direction away from the Pacific plate and the Cocos plate. During collisions, the Nazca plate is forced into the mantel giving rise to volcanic eruptions which gave rise to present geological features of the Islands. Basalt which when compared to other lava types is much more fluid. Thus, there are formations of geological structures which are formed by the lava and the continuous action of rain and persistent coastal waters which provide a trial background for evolution where only those who can adapt will be able to survive. Lava canes and pit craters are formed as the hot lava flows and the top is cooled off and during the end of the eruption, the lava drains away leaving a hollow crater. Such classic craters are visible at Los Gamelos in the highlands of Santa Cruz. High lava cones are also formed. Lava which comes out from vents and edges, other than that of the main volcano, tend to localize at a few spots along the fissures giving rise to cone like structures. Such cone like structures is clearly visible at Isla Bartolome adjacent to the Santiago Island. Since the islands have unique geological features the flora and fauna of the islands had to adapt for survival. Most of these formations are used by birds and other terrestrial animals as nesting and breeding grounds. During my hiking expedition on Sierra Negra I made an observation that the Galapagos hawks and finches chose high altitude environments for nesting and hunting purposes. The volcanic eruptions of the Galapagos affect the soil in a positive manner. The volcano ash and basalt lava form very rich soil, in fact the Galapagos volcanic soil is among the richest soil on earth. The nutritious and rich volcanic soil provides the plants with all the necessary nutrients thereby facilitating growth of a wide variety of vegetation. Thus the vegetation also adapted them to the soil. INTRODUCED AND INVASIVE SPECIES Invasive species are a threat to any ecosystem because they disturb the equilibrium that had already been established but in case of archipelagos they pose a far severe threat because the organisms that evolve in these archipelagoes face different selective pressures than those faced by mainland organisms, thus they are very strongly affected by invasive species. These species-poor island communities evolve under low pressure from competitors and natural enemies, rendering island ecosystems especially vulnerable to the introduction of exotic species (for a review (Van Leeuwen et al. 2005). Many of these species are introduced intentionally while some arrive accidentally via ships and planes. Since the Islands have become a fishing and tourist hot-spot the chances of introduction of unwanted species have also risen. Browsing and trampling by herbivorous mammals, predation by ants or mammals, virulent diseases and frequent and intense fires are some of the forces that can change the ecosystems (Loope, et al. 1988). In case of plants, change in nutrient cycling can drastically affect a particular ecosystem. Several researchers have studied impacts of introduced and invasive species according to which at least eight plant species are endangered and one extinct and among the animal population, 19 are extinct while 74 more are critically endangered. Feral goats, pigs, dogs, cats, rats, and many other species have altered ecosystem characteristics and driven endemic species, such as several species of the Galapagos tortoise, to extinction (Mauchamp 1997). Feral goats (Capra hircus) were deliberately abandoned by humans and the population grew so fast that today all islands of the Galapagos have to face problems induced by this invasive species. The feral goats quickly adapted to the new climate and environment and they can thrive on little or almost no food and water for several days. These goats feed on all types of plants (Acacia, Bursera graveolens etc) which other species are also dependent upon; overfeeding may induce a domino effect resulting into eradication of a number of other species like finches and iguanas. Giant tortoises have also been outcompeted in grazing on the grassland by the goats and a declination in their numbers had been noticed owing to shortage of food. This is detrimental to the food chain because Galapagos hawk are dependent for food on the eggs of the tortoises, and if owing to food scarcity, the tortoises die out or move, there is sure be negative impact on the hawk population as well. The goats also caused damage to the top soil while feeding on the vegetation because since the vegetation held the soil together, the rain storms could now easily wash the top soil in absence of vegetation. But, this was not all; the goats have a relatively small gestation period which means that they produce twice a year. This led to drastic increase in the goat population in the Islands. Similar problems of invasion were faced with invasive species of pigs and donkeys. Another study showed the negative influence of invasive species on the native population. Introduction of rats (Rattus spp.) and house mice (Mus musculus) are considered responsible for a significant number of extinctions and ecosystem changes on islands worldwide (Towns et al. 2006). Ship rats inhabit about 35 islands in the Galapagos. These rats feed on the eggs and new-born chicks of petrels (Oceanodroma Tethys and Oceanodroma castro) who colonize in the highlands of Santa Cruz, Santiago and Isabela islands, thereby reducing the fertility percentage of these birds. Ship rats also fed on the eggs of the endemic giant tortoise (Geochelone elephantopus ephippium) and were responsible for drastic declination in their numbers until the rats were controlled. Mice are presently found on 12 islands and inflict much damage on the vegetation. They dig around the roots of the cactus (Opuntia echios) thereby reducing the plant’s stability owing to which the plant often gets water logged and perishes. 750 vascular plants have been introduced into the Island among which a few have turned invasive and are causing harm to the native biota. These plants were intentionally introduced for agricultural and horticultural purposes. These invasive trees have the capability to transform their habitat and establish population where vegetation was previously not possible. Blackberry vegetation is one the most aggressive invasive plant species that are posing threat to the Galapagos. They compete with endemic plant species for water and minerals. In the 1970’s, Hill Blackberry (Rubus niveus) was introduced in the Islands of Santa Cruz, Santiago and Isabela. At first they were introduced for harmless agricultural purposes alone. Owing to the seed dispersal by mockingbirds this plant species spread to other Islands also affecting vegetation. R.niveus has the ability to produce fruit within three months and seeds can remain in dormant stage for many years till the onset of favorable conditions. They invaded all vegetation lands and formed thick dense branch growth which gradually replaced natural vegetation and posed threat to many endemic plant species. R. niveus and other invasive plants have depleted the population of Scalesia pedunculata forest at Los Gemelos, Sta. Cruz Island. (Renteria & Buddenhagen, 2006). Some studies have also shown that since invasive species transform the environment, they create a platform for growth of other invasive species. The red quinine tress (Cinchona pubescens) was introduced in the Galapagos in the 1940’s and it became invasive, covering over 11000 ha in the Santa Cruz Island alone. It gradually spread to neighboring islands as well. It destroyed vegetation by forming thick canopies which subsequently prevented sunlight and stopped 70% of the incident photoactive radiation and increased precipitation formation leading to death of the plants lying below the canopy. This plant species decreased the genetic diversity of other endemic plants by almost 50%. Since, the plant formed canopies and left the ground bare, another invasive plant Stachys agrarian, flourished under the canopy. Before quarantine measures were taken, several harmful insects’ species had already entered the Islands unintentionally. Many of this species are potential invasive species and can replace native species. Two fire ants species (Wasmannia auropunctata and Solenopsis geminata) are aggressive and have been seriously affecting native invertebrates and also interfering in the nesting habits of birds as well as tortoises. Two recently introduced wasp species (Polistes versicolor and Bachygastra lecheguana) have been predating upon insects which also form a part of the diet of the finches. If the wasps continue feeding on the insects, the insect-eating finches would gradually starve and may eventually become extinct. Some invasive insect species like Icerya purchase attacks 61 species of native plants like Scalesia etc and can cause death of the plants. Disease outbreaks have also been noticed owing to introduction of new species. Humans recently introduced a few domestic birds and the captive population of poultry birds in the Galapagos developed fatal bird diseases (Marek’s disease and Newcastle’s disease) Conclusion As I come towards the end of my research, I would like to remind you about the most important points of my documentation. The ecosystem interaction of the Galapagos Islands is very closely knit one owing to the low genetic diversity; The system being almost interdependent on one another, a change is one of the elements will hamper the entire cycle, therefore care must be taken to maintain the uniqueness of the ecosystem. The flora and the fauna present on the islands have flourished on their own through necessary adaptation and continue to adapt to the ever changing environment of the active Volcano Islands. Next, the negative effects of invasive species must be understood well. The way in which they interact with the established ecosystem and then gradually alter it thereby disturbing the equilibrium needs to be kept in mind. One must be become aware as to how unintentional introduction maybe prevented. The core intention of this presentation is to make you realize the uniqueness of such valuable ecosystems and the immediate need to protect it. The beauty of the Galapagos lies in its exoticness and adaptive viability. The synchronized ecosystem which have established through rigorous adaptation is being threatened by invasive species. Once destroyed, we can never retrieve what is lost and thus we must understand the importance of protection. I would like to conclude my presentation by quoting our two favorite tour guides that we all hold dear. “It is very important to preserve the wildlife and vegetation in the Archipelagos. There are many endangered species that are facing extinction such as the giant tortoises and we have to work together to preserve this environment so that our grandchildren will be able to see what are we seeing now – Julio”. “Don’t forget to brush your teeth! – Javier.” REFERENCES Janzen, D.H. "seed predation by animals." Annual Review of Ecology and Systematics 2 (1987): 465-492. Web. Lawesson, J.E. "An updated and annotated check list of the vascular plants of Galápagos Islands." Reports from the Botanical Institute, University of Aarhus 16 (1987): 1-74. Print. Leeuwen, V. "Native or introduced? Fossil pollen and spores may say. An example from the Azores Islands." Neobiota 6 (2005): 27-34. Web. Loope, L.L. "Comparative conservation biology of oceanic archipelagoes: Hawaii and the Galápagos." BioSciences 38 (1988): 272-282. Web. Mauchamp, A. "Threats from Alien species in the Galapagos islands." Conservation Biology 11 (1997): 260-263. Print. Peck, S.B. "The species-scape of Galapagos organisms." Noticias de Galapagos 58 (1997): 18- 21. Web. Rentaria, J.L, and C. Buddenhagen. "Invasive plants in the Scalesia pedunculata forest at Los Gemelos, Santa Cruz, Galapagos." Galapagos Research 64 (2006): 31-35. Web. Thornton, I W. B. Darwins Islands: A Natural History of the Galápagos. Garden City, N.Y: Published for the American Museum of Natural History [by] Natural History Press, 1971. Print. Towns, D.R, I.A Atkinson, and C.H Daugherty. "Have the harmful effects of introduced rats on islands been exaggerated?" Biological invasion 8 (2006): 863-891. Web Tye, A. "Outstanding terrestrial features of the Galapagos archipelago. In: Bensted-Smith R, ed." Biodiversity Vision for the Galapagos Islands. Puerto Ayora: Charles Darwin Foundation and World Wildlife Fund, 2002. 12-23. Print. Read More