Species Diversity

Conservation Bio midterm

Biodiversity

defining issue of conservation biology

Species diversity

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

How many species on earth?

about 1.7-1.8 million species described

taxonomic synonym

a species with multiple scientific names

• inflates species estimates

discovery rate

used to estimate the number of undescribed species (20,000 discovered each year)

What is a species

fundamental unit of taxonomy and species diversity (3 common concepts: biological sc, morphological sc, and DNA sc)

taxonomy

science of classifying organisms

Biological species concept

group that can interbreed in the wild and breeding = viable/fertile offspring

biological species are maintained by

reproductive isolating mechanism

behavioral/anatomical/physiological mechanisms that prevent out breeding

• prevent fertilization (pre-zygotic barriers)

• prevention of hybrid zygotes (post-zygotic barriers)

(reduces fitness of parents)

complications with biological species concept

• some organisms can interbreed successfully

• mating is difficult to observe in wild

• hybrids can go undetected

Morphological species concept

a group of individuals that are morphologically distinct from other groups 

• oldest method

• still widely used

Complications with morphological species concept

• similar individuals can be different species

• cryptic species (hard to tell apart with phenotypic differences)

• different looking individuals can be the same species

Divergent evolution

groups with common ancestors are becoming increasingly different over time

ecotype

genetically and phenotypically distinct forms of a species

• typically adapted to different environmental conditions

polyphenism

changing phenotype in different environmental conditions

• ex: seasonal forms

DNA barcoding

analyzing a region of DNA to determine base-pair sequences to identify a species

• use of tissue sample

DNA sequences advantages

• overcomes the limitations of other two concepts

• identification of species from tissue sample

• identification of species from suspected wildlife crime

Complications with DNA sequences

• disagreements with how much genetic difference is needed 

• risk of taxonomic inflation

• using different regions of the genome can give different results 

Scientific name

genus + species

Rules for species names

• genus, species and subspecies name ALWAYS italicized

• genus ALWAYS capitalized

Ecosystem with highest species diversity

Oceans

• 31/35 animal phyla

• 1/3 only found in the ocean

Latitudinal species concept

general increase in species diversity further from the poles

climactic stability hypothesis

tropical = more stable climate seasonally and geologically

• predictable resources

• niche partitioning

Diversification rate hypotheis

tropics have faster speciation rate (how frequently new species arise from existing ones)

• increased reproductive isolation and  mutation rate

elevational diversity gradient

increases with moderate elevation and decreases with further elevation

theory of island biogeography

• island with no species has an increase in immigration at first

• immigration decreases as all possible species colonize the island

• extinction rate is low at first and increases as more species occupy the island

• where rates intersect = species richness equilibrium

migrating species

more likely to encounter

• less isolated islands

• larger islands

species richness on islands

larger on larger islands and lower on smaller ones

disturbance and species diversity

intermediate disturbance hypothesis (IDH)

• a little disturbance is good

Species richness measurement

number of species in a given area

• simplest measurement

RH Whittaker

introduced alpha, beta, and gamma diversity

alpha diversity

• measured species diversity at a local scale

• higher = more species = good

gamma diversity

• number of species in a landscape

• larger scale that includes different ecosystems

• higher = more species = good