**8. Concluding remarks**

Despite the current appearance of human-disturbing habitats, especially in those islands that are inhabited, where this survey took place, the Galápagos Archipelago are the world's most pristine, best preserved and protected, tropical oceanic island ecosystem where more than the 95% of the land area in the islands is part of the Galápagos National Park [55].

The present work is a first approach to the study of the yeasts biodiversity and occurrence in the Galápagos Islands and Mainland Ecuador. The data herein presented show, nevertheless, some interesting relationships in both environments. Adaptation to the new conditions as well as the disharmony in term of biodiversity between both ecosystems appears to be aligned to the situation of some macro organisms such as plants. We have found a coincidence of 31% of the yeast species between the explored islands and the mainland; remarkably, 30% of plant species represented in the Galápagos Islands has also been registered in mainland. We could not proof endemism in the present work.

Endangered plant species may also put in danger some insects associated to those endemic plants, since the insect-plant associations generates different degrees of dependence. Studies carried out between 2001 and 2002 showed that 19 endangered plant species exhibit a range of interactions (with different degrees) with 108 different insect species that use the plants as refugee or food. The study carried out by [56] shows that 77% of the insects are endemic. From our studies, insects have shown to be the second source of yeasts biodiversity after flowers. Moreover, studies focused on insect-yeast interactions, have shown a remarkable role of insects acting as "wet nurses" for yeasts during certain periods during the year [57]. Consequently, some yeast species could be endangered along with their hosts who have a tight mutualism relationship with the endangered plant species.

To date, two novel yeast species collected in this survey were already described (i.e. *Saccharo‐ mycopsis fodiens* and *Kodamaea transpacifica*). Both yeasts species were isolated from nitidulid beetles in ephemeral flowers of *Ipomoea* sp. and *Datura* sp. These species are regarded as biomarkers for ancient migrations of Polinesyan sailors, who took the sweet potato plants (*Ipomoea* sp.) from the Andes (currently Ecuador and Peru) and introduced them into Polynesia and beyond [58].

In this chapter we have developed a new ecological approach by means of a mathematical model which is useful for a better understanding of the adaptability of yeasts as well as the specialization degree of these microorganisms in Ecuadorian ecosystems. The data herein processed will be completed in future expeditions, but constitutes a base for the upcoming ecological studies of the yeasts in the Galápagos Islands and Ecuadorian Mainland. The mathematical model shows an inverse correlation between the "Index of Specialization" (*Si* ) and the "Index of Abundance" (*Ia*). Moreover, it can be seen that the trend is towards the specialization since 70 out of 104 yeasts species analyzed (c.a. 67%) showed a *Si* between 0.92 to 0.53, which means that they were isolated from a maximum of three out of seven ecosystems and a maximum of three out of nine substrates; 30 yeast species (c.a. 29%) showed an inter‐ mediate *Si ,* between 0.18 and 0.47, meaning that these yeasts species were found in a maximum of six different ecosystems and six different substrates; finally, only four yeast species (c.a. 4%) showed a very low *Si ,* between 0.02 and 0.11, which means that these species were found in up to seven ecosystems and nine substrates analyzed. These four yeast species are considered the more generalist and exhibit the highest adaptability, but represents a minority in the complete pool of yeast species studied. The total number of ecosystems analyzed was seven and the total number of substrates studied were 10. No yeast species were found in all the 10 substrates.

**Figure 5.** Curve of adaptability of the yeasts species studied in Mainland Ecuador and four Islands in the Galápagos

Analyzing this curve it is possible to infer that the higher the slope, the more specialized is the yeast species and vice versa. This kind of modeling is useful to have a general understanding of the behavior of yeast species in the ecosystems. As the information of new collects and characterization of yeasts is updated in the data base of the CLQCA this model will become

Despite the current appearance of human-disturbing habitats, especially in those islands that are inhabited, where this survey took place, the Galápagos Archipelago are the world's most pristine, best preserved and protected, tropical oceanic island ecosystem where more than the

The present work is a first approach to the study of the yeasts biodiversity and occurrence in the Galápagos Islands and Mainland Ecuador. The data herein presented show, nevertheless, some interesting relationships in both environments. Adaptation to the new conditions as well as the disharmony in term of biodiversity between both ecosystems appears to be aligned to the situation of some macro organisms such as plants. We have found a coincidence of 31% of the yeast species between the explored islands and the mainland; remarkably, 30% of plant species represented in the Galápagos Islands has also been registered in mainland. We could

95% of the land area in the islands is part of the Galápagos National Park [55].

Archipelago.

more robust and accurate.

226 Biodiversity - The Dynamic Balance of the Planet

**8. Concluding remarks**

not proof endemism in the present work.

Moreover, we have found that in the Galápagos Islands the percentage of yeast species that are colonizing a single substrate is about a 30% higher than the correspondent figure in mainland (Figure 4). We can hypothesize that in mainland the ecosystems have had much more exchanges along the natural history, furthermore, the yeasts species were able to adapt to a wider range of substrates. In the Galápagos archipelago, a rather young group of volcanic islands, the exchange as well as the opportunity to colonize new substrates and—in evolu‐ tionary terms—to adapt to new micro environments, has been certainly lower than in the interconnected mainland ecosystems. In other words, we can see that adaptability of yeasts in mainland and the archipelago is clearly different.

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

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Undoubtedly there is much work to do in order to attain a better understanding on ecology of yeasts in the archipelago, since the sampling was done in 4 of the 21 islands. Future expeditions may focus on substrates such as flowers, insects and rotten vegetal matter, in order to fill the shortfalls from the previous collections, such as more novel yeast species as well as endemic species from the Galápagos Islands.
