1.2. Species interactions and biodiversity

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From the course by National Research Tomsk State University

Biological Diversity (Theories, Measures and Data sampling techniques)

67 ratings

National Research Tomsk State University

Biological Diversity (Theories, Measures and Data sampling techniques)

67 ratings

The course presents an overview of the theory behind biological diversity evolution and dynamics and of methods for diversity calculation and estimation. We will become familiar with the major alpha, beta, and gamma diversity estimation techniques. Understanding how biodiversity evolved and is evolving on Earth and how to correctly use and interpret biodiversity data is important for all students interested in conservation biology and ecology, whether they pursue careers in academia or as policy makers and other professionals (students graduating from our programs do both). Academics need to be able to use the theories and indices correctly, whereas policy makers must be able to understand and interpret the conclusions offered by the academics. The course has the following expectations and results: - covering the theoretical and practical issues involved in biodiversity theory, - conducting surveys and inventories of biodiversity, - analyzing the information gathered, - and applying their analysis to ecological and conservation problems. Needed Learner Background: - basics of Ecology and Calculus - good understanding of English

From the lesson

Biodiversity and evolution

In this module we will explore the evolution of biodiversity. In particular we will understand what is the web of life and how species interact to coexist.Moreover, we will understand the main processes that allow the evolution of biodiversity and how it is structured and structures itself. Finally, we will review the distribution patterns of biodiversity in macroscale.

1.2. Species interactions and biodiversity6:29

Meet the Instructors

Roberto Cazzolla Gatti
Ph.D., Associate Professor in Ecology and Biodiversity
Biological Diversity and Ecology Laboratory, Bio-Clim-Land Centre of Excellence, Biological Institute

[MUSIC]

Hi guys, welcome back.

This is the second lecture of the course, Biological Diversity, Theories,

Measures, and Data Sampling.

I'd like to begin this lecture with a question for you.

Do you think is it possible to conserve something that change constantly?

I mean, there have been five mass extinction during Phanerozoic, and

one is happening just now.

Extinction increased because of autocatalytic domino effect.

And this is due to the presence of keystone species.

Keystone species are species that are able to build the ecosystem.

So when one keystone species became lost,

become extinct, all the ecosystem is damaged.

The star fish is Pisaster ochraceus is a keystone species in the interdata marine

environment of North America.

This species feeds on the mussel Mytilus californianus.

When scientists removed this keystone species from the environment

the mussel population rapidly increased.

And this explosion completely excluded all the other species in the ecosystem.

This is why the presence of keystone species and

the interaction between species allowed the presence of biodiversity.

Another example of a keystone species is beaver.

Beaver plays a very crucial role in biodiversity.

Thanks to the dam they build and

the pond they create, many other species can survive.

This is why they protect the web life upon which all the ecosystem depends.

I wanted to give you a provocative idea.

Should we consider the evolution, the original species,

or the maintenance of them?

I mean, consider the book of Darwin, which title would be more appropriate?

The Origin of Species by means of natural selection and the preservation of favoured

races in the struggle for life or The maintenance of species by means

of adaptation and the preservation of them by avoiding to struggle for life?

The struggle for existence proposed by Darwin was formalized by Gause's

competitive exclusion principle.

This principle states that if two species share the same niche,

only one of them can survive and the other one would be excluded.

Gause Competitive Exclusion Principle was tested in laboratory,

with only two paramecium species.

Indeed, this principle has never been observed in real nature.

This is why in '98, Connell proposed the idea of close competition past

as a possible reason for observer differentiation in niches.

Competing species can be less fit than species which avoid to compete.

Natural selection can then favor non-competing species.

Their population can increase and those of competing species decrease.

The current differences in each we observe are thus the result of past competition.

At this point we need to specify what is a niche.

The Hutchinsonian niche is an n-dimensional

hypervolume where all dimensions are environmental conditions or resources.

And this condition creates the space where a species can live.

The hypervolume define the multi-dimensional

space of resources such as energy, nutrients and structure.

These resources are available to all the organisms of that species.

So does biodiversity come from competition?

We know that the Interspecific competition reduced

the number of species because of competitive exclusion.

But at the same time, Intraspecific competition increased

the number of species because of carrying capacity.

This also happens to human beings.

In an attempt to clarify competition, Vito Volterra,

James Lotka developed the model of Competition.

This model asks two questions but this very simple model is oversimplified.

These are linear module, it accounts only for two species but

nature is much more complicated.

Not convinced by the competitive principle,

in 1961 ecologist Hutchinson suggested the paradox principle.

The problem, he wrote, that is presented by the phytoplankton is essentially

how it is possible for a number of species to coexist in a relatively isotropic or

unstructured environment all competing for the same sort of materials.

Species are filed under different sets of environmental condition.

This is why if the environment changed sufficiently during time,

no competitor can remain superior to exclude the other species for a long time.

And what happens if environment doesn't change?

Two mechanisms allow to reduce competition and

at the same time guarantee the co-existence of species.

This mechanism is special distribution and biological history.

Dispersal and migration liabilities reduce the competition for space and resources.

And at the same time, the rule and

the niche of a species come from the past interactions.

Even if competition is the most studied interaction in ecology,

models are too simple.

And no real species as unique realize in niche.

We have no proof of competition now, and in the past.

Therefore, we need to move behind extreme line model or competition.

There are some neglected points.

Heterogeneity and environmental variability do matter.

Avoiding the competition in the past allowed the coexistence in the present.

And character displacement amplifies small phenotypic differences during time.

In 2001, Stephen Hubbell proposed the neutral theory

of biodiversity with random vat, speciation, and dispersal.

In this theory, the essential feature is that species are considered all equal or

identical and they have all the same fitness.

Anyway, as the equilibrium theory of island biogeography

proposed by MacArthur Wilson, our both neutral theory

as the main word to have increased the importance of species' niches.

We will discuss it in more detail during next lecture.

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