Conservation Biology S.D. (Lecture 2)

What Are the three components of Biodiversity?

Species Diversity, Genetic Diversity, and Ecosystem Diversity

Species Diversity

All species in an area and the relative abundance of those species

Genetic Diversity

The genetic variability within a species or population

Ecosystem Diversity

The range of different ecosystems in an area and their associations and interactions between and within them

Problems with Calculating S.D.

• Unknown Taxonomic synonyms (a species that has multiple scientific names)

• Most species not yet described

How can we estimate how many unknown species there are?

Species Discovery Rate

Species Concepts

• Biological

• Morphological

• DNA

Biological Species Concept

When a group of individuals can interbreed and produce fertile offspring

Problems:

• organisms considered different species sometimes interbreed successfully

• Hard to determine

• Hard to apply to asexual organisms

• Does not apply fossil species

Reproductive Isolating Mechanisms

Behavior, anatomical, or physiological mechanisms that evolved to either:

1. Prevent fertilization between different species (Prezygotic barriers)

2. Prevent hybrid zygotes from developing normally (Postzygotic barriers)

Morphological Species Concept

When a group of individuals is morphologically distinct from other groups (clustering of phenotypes)

Sometimes called morphospecies

Problems:

• Similar looking individuals can be different species (cryptic species)

• Differently looking individuals can be the same species

Cryptic Species

Species that are very difficult or impossible to tell apart using phenotypic differences

Morphospecies

Species defined by the morphological species concept (look disctinct)

Divergent Evolution

Groups with common ancestors becoming increasingly different over time

Ecotype

Genetically and phenotypically distinct forms of a species

Polyphenism

Changing phenotype in different environmental conditions (ex. seasonal forms)

Metamorphosis

Changing phenotype with life history (ex. reproductive status)

DNA-based Species Concepts

Using similarities in DNA sequences to determine relatedness

Fundamental technique: DNA barcoding

Problems:

• Using different regions of the genome can give varying results

• Uncertainty abt how much genetic variation is necessary to distinguish a group as a species

• Risk of taxonomic inflation

eDNA (environmental DNA)

Using mass-sampling techniques to look for new species and access biodiversity (ex. sampling a pond’s water)

Taxonomic Inflation

Where everything that can be distinguished becomes its own species

Where are the majority of species distributed?

• Tropical forests contain over half the species

• Mediterranean-type environments

• Generally towards the tropics

Latitudinal Diversity Gradient

The increase in species diversity as you move closer to the equator

Climate Stability Hypothesis

Tropic areas have a more stable climate, leading to predictable resources

Diversification rate hypothesis

Tropics have a faster speciation rate

Niche Partitioning

Resource Specialization (ex. parrot fish eating coral)

Elevation diversity gradient

Terrestrial S.D. often increases with moderate increases in elevation, then decreases with further elevation

Aquatic S.D. decreases with increasing depth

Equilibrium Theory of Island Biogeography

Theory built on 2 observations:

1. S.D. on islands is a factor of immigration rate and extinction rate

2. Immigration rate and extinction rate are a factor of island size and isolation

Three major observations regarding island size and isolation that affect immigration and extinction rates

1. Migrating species are more likely often to counter closer islands

2. Migrating species are more likely to encounter larger islands

3. Likely to be more species present on larger islands (species-area relationship)

Target effect

Larger islands will get more immigrant species

Rescue effect

Larger islands will receive more individuals

Distance Effect

Closer islands are more likely to receive immigrant species

Intermediate Disturbance Hypothesis (IDH)

S.D. is maximized in areas with intermediate levels of disturbance

• Not universally accepted

Factors Determining S.D

• Latitude

• Altitude

• Size of habitat

• Level of disturbance

• Primary production

• Distance of habitat from another

Ways to measure S.D.

• Visual Surveys

• Acoustic Surveys

• Camera Traps

• Genetic Material

Species Richness (S)

Number of species in an area

• Simplest measure of S.D.

• Used to develop the concepts if alpha, gamma, and beta diversity

R. H. Whittaker

Used species richness (S) to develop the concepts of alpha, gamma, and beta diversity

Alpha diversity

Number of species per habitat

Gamma diversity

Number of species in a “landscape”

Beta diversity

Measure in the difference in species composition between local areas

What 2 variables help to INCREASE diversity indices?

1. Increasing species evenness

2. Increasing species richness

Simpson’s Diversity Index (D₂)

A Dominance Index that gives more weight to common or numerically dominant species. Rare species will hardly affect the index

Shannon Diversity Index (H’)

An information Index that measures disorder. Species with low number contribute much more than in Simpson’s Diversity

What are 2 Assumptions that are made when analyzing S.D.?

1. All observations were obtained randomly

2. All species in an area were detected

Species Accumulation curve

Curve that shows the proportion of species that you found during a survey