**An Overview of the Yeast Biodiversity in the Galápagos Islands and Other Ecuadorian Regions**

Enrique Javier Carvajal Barriga, Patricia Portero Barahona, Carolina Tufiño, Bernardo Bastidas, Cristina Guamán-Burneo, Larissa Freitas and Carlos Rosa

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/58303

**1. Introduction**

One of the most emblematic natural regions for studies of evolution and biodiversity in the world is the Galápagos Islands, which is the inspiring environment where the naturalist Charles Darwin was moved to propose what eventually became Theory of the Origin of Species launched in the 19th Century.

This Archipelago has been formed by subaquatic volcanic activity around 5 million years ago. The plant and animal populations settled on this group of 21 islands and 107 rocks and islets were introduced mainly by the sea currents and winds that reached the emerging lands in this equatorial region of the sea.

The study of plants and endemic species of animals has fascinated biologists for decades. Giant turtles, finches, marine and terrestrial iguanas and boobies have been the center of studies, as well as other birds and flora of the region. Many adaptations and evolution evidences were found in the macrobiota adapted to the particular environments of each island in the archipelago.

However, not much attention was paid to the microorganisms and, in particular, to yeast biodiversity in the islands. In 2009 in an effort to address this scientific shortfall, a prospective study was started by Ecuadorian-Brazilian-Spanish team that visited four human-inhabited islands (i.e. Floreana, San Cristóbal, Santa Cruz and Isabela).

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The substrates chosen by the researchers were mainly flowers from *Datura* and *Ipomoea* genera, as well as *Opuntia* fruits and leaves. Moreover, unique substrates like endemic tree's exudates or even giant turtle's and marine iguana's feces were also taken. Flowers, insect, fungus and rotten vegetal matter was also part of the substrates chosen by the expeditionaries.

non-represented families of plants are: Palmaceae, Anacardiaceae, Meliaceae, Labiatae,

An Overview of the Yeast Biodiversity in the Galápagos Islands and Other Ecuadorian Regions

http://dx.doi.org/10.5772/58303

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In the Galapagos Archipelago the diurnal temperature varies from 5°C in the windward side of the islands, to 10°C in the leeward sides [2]. The annual range is from 11 to 12°C; while during the warm season (from December to June) the temperature reaches 29°C. In August,

Because of the equatorial location of the islands, there are only two seasons readily distin‐ guishable, where the rainy weather coincides with warm period (December to June) and the dry, cooler season from July to November, which is a period characterized as mostly foggy

In terms of rainfall, the whole archipelago receives less than 750 mm per year; this is due to the geographical situation of the islands which are in the dry zone of the Pacific Ocean.

The islands where the yeast expedition was carried out in October 2009 (during the dry season), are all inhabited by human populations. These four islands: Isabela, Floreana, Santa Cruz and San Cristóbal have littoral zones as well as high zones which exhibit very clear differences in plant species. The zones of the higher elevations such as Sierra Negra volcano are mostly rocky and sterile, where only a few *Opuntia* sp. individuals are seen. In contrast the higher zones of Floreana, Santa Cruz and San Cristóbal all of them exhibit a green cover and even agricultural

The list of plants occurring in the littoral zone is small and differs less from a list of plants from a comparable mainland zone [3]. As for the vegetation in this zone, there is a lack of plant species in the sheer cliffs or basalt rocks rising from the sea to 10 or more meters. In Santa Cruz Island there is a predominant and extended area of "palo santo" *Bursera graveolens*, in a rather

There are also arid zones located immediately inland from the littoral zones, where vegetation is xerophytic which remain even up to 80 to 120 m height but sometimes much higher reaching up to 300 m. Predominant genus in this zone are *Opuntia*, *Jasminocereus* and *Brachycereus* which share the spaces with small leaved and spiny shrubs and trees. Most interestingly for yeast communities which "prefer" to degrade vegetal matter is the fact that annual herbs prosper during the wet season, providing a green cover which lasts for several weeks. After that period, the biomass from the green blanket dies and degrades: a micro ecological niche which offers a great opportunity of growth for yeasts and other microorganisms. *Datura* and *Ipomoea* species both of them introduced by human in undetermined times, are frequently found in this zone

In the transition zone the plant communities are frequently evergreen with ample leaves which provides with a green landscape to this zone. There is possible to find out some epiphytic

zones where a number of introduced species are being cultivated.

Scrophulariaceae, Orchidiaceae, Acanthaceae, Melastomataceae and Bromeliaceae[1].

**2.1. Climate**

and overcasted [3].

**2.2. Vegetation zones**

xerophytic vegetation environment.

as well as in the transition zone.

the upper limit is about 19°C [3].

The resulting prospection yielded more than 800 yeast isolates. Most of those yeasts have been identified by sequencing of the LSU or the 26S rDNA gene. Among the yeasts recovered, there are several novel yeast species such as *Saccharomycopsis fodiens* and *Kodamaea transpacifica*, and other hitherto non described ones.

About 31% of the yeast biota in the islands is coincident with the species found in Ecuador mainland. Most of the yeast species are hitherto not found in the mainland since 2006 when the Catholic University Yeasts Collection (CLQCA) initiated its identification, characterization and preservation activities, devoted to yeast. Currently this yeasts collection represents the most complete deposit of wild species from Ecuador.

A comparison between the yeast biodiversity in the islands with the yeasts biodiversity in Ecuadorian mainland is done in this chapter in order to draw a first line of understanding of the adaptability, biogeography and interaction of species in an insular territory located about 1000 Km from the nearest South American mainland coasts.

Moreover, an overview of the yeast biodiversity of mainland Ecuador's ecosystems is ad‐ dressed in this chapter in order to establish the comparisons and the extent in which the closest mainland has had influence in current microbial (yeast) biodiversity in this relatively recently formed archipelago in the Pacific Ocean.
