Lecture 11 - Species

Question 1

What is the debate of weather species are real?

Answer 1

Are species a reality of nature or are they simply theoretical constructs of the human mind

Many biologists agree that discrete groups are real but there is a disagreement on whether such entities constitute species and how best to define them

Question 2

What purposes does the species concept need to be operational?

Answer 2

1. to enable us to classify organisms systematically
2. to correspond to discrete groups of organisms present in nature
3. to help understanding how discrete entities arise in nature
4. to represent the product of evolutionary history
5. to be applicable to the largest possible variety of organisms

Question 3

Morphological (or typological) species concept

Answer 3

Individuals are members of the species if sufficiently conform to certain morphological characters or type, that are essential fixed properties

Question 4

Biological species concept

Answer 4

Group of actually or potentially interbreeding populations which are reproductively isolated from other such groups

Question 5

How many species concepts are there

Answer 5

over 25

Question 6

In the morphological species concept what might the morphological differences between species be down to?

Answer 6

Some phenotypic differences may be down to reproductive isolation and others to adaptive differences related to the environment

Question 7

Limitations of the morphological species concept with examples

Answer 7

1. Variations among populations of the fixed type e.g. white and blue forms of snow goose, born to the same mother, represent polymorphism within the same species
2. Identify an arbitrary stage when individuals are different enough to be considered species, geographic isolation, e.g. when do cats become different species
3. Morphologically indistinguishable species (sibling species) e.g. European mosquito is a cluster of six sibling species but only one transmits malaria also saccaromyces cerevisiae 8 different species that have very different uses for humans

Question 8

Limitations of the biological species concept with examples

Answer 8

1. It is only applicable to sexual outcrossing organisms, so it does not apply to parthenogenetic organisms, and bacteria
2. it is limited to a short interval of time and does not apply to fossils
3. sometimes difficult to apply to some intermediate cases. e.g. narrow hybrid zone for European crows, carrion and hooded crows can have some gene exchange also there is broad sympatric hybridisation of the grey oak and gambels oak with the hybrids being intermediate
4. difficult to apply to geographically isolated populations

Question 9

Why do most humans use the biological species concept

Answer 9

It actually does work for extant species

Humans find it intellectually challenging the problem of how reproductive isolation arise within one species, and has connections to infertility

It is possible to tackle how reproductive isolation evolves for example using hybrids and modern molecular tools

Question 10

Phylogenetic species concept 1

Answer 10

A basal cluster of organisms that is diagnosably distinct from other such clusters, and within which there is a parental pattern of ancestry and descent

Question 11

Phylogenetic species concept 2

Answer 11

The smallest exclusive monophyletic group of common ancestry

Question 12

Example of how the phylogenetic species concept and biological species concept differ?

Answer 12

The phylogeny of mother Greya Sp. based on mitochondrial DNA sequence data.

The Californian population is more closely related to G.mitellae than it is to other geographic populations fo the same biological species

Question 13

How much does the classification of the biological and morphological species concept differ?

Answer 13

There is not a lot of variation

Question 14

What are the 3 different types of isolating barriers?

Answer 14

Pre-mating barriers

Post-mating pre-zygotic barriers

Post zygotic barriers

Question 15

Pre-mating barriers

Answer 15

factors that prevent the transfer of the gamete to member of the other species

Question 16

Post-mating pre-zygotic barriers

Answer 16

gamete transfer occurs but the zygote is not formed

Question 17

Post-zygotic barriers

Answer 17

Hybrid

Question 18

What are the two types of pre-mating barriers?

Answer 18

Behavioral isolation and ecological isolation

Question 19

Behavioral isolation

Answer 19

Involves differences that lead to lack of cross-attraction between members of the same species

Question 20

Ecological isolation

Answer 20

The isolating barriers are based on differences in species adaptations to local environment

Question 21

Three difference types of ecological isolation?

Answer 21

1. Habitat isolation
2. Temporal (allochronic) isolation
3. Pollinator isolation

Question 22

Habitat isolation

Answer 22

Spatial separation during breeding seasons

Question 23

Temporal (allochronic) isolation

Answer 23

Different breeding time

Question 24

Pollinator isolation

Answer 24

Differential interaction with pollinators

Question 25

Behavioral isolation: different pheromones

Answer 25

Pheremones can be volatile compounds that serve as a wide-range chemical signal, or contact pheromones perceived at close range or by contact

For example, the European corn borer Ostrinia nubilalis (moth) females from different races produce different blends of the cis and trans isomers of the same pheromones

Question 26

Behavioral isolation : different visual signals in Courtship

Answer 26

Female shops around for the best male and the male appearance must continually evolve

Question 27

Behavioral isolation: different acoustic signals in courtship

Answer 27

There are differences in morphologically indistinguishable species of green lacewings that prevent them from mating

Question 28

What are the two types of habitat isolation

Answer 28

Microspatial isolation

Macrospatial isolation

Question 29

Microspatial isolation

Answer 29

Members of two species occupy the same general area but their reproductive encounters are reduced because they are adapted (or prefers) different ecological niches

Question 30

Macrospatial isolation

Answer 30

Members of two species cannot interbreed because their habitats are allopatric

Question 31

Example of microspatial isolation

Answer 31

Plants can be microspatially isolated using different niches in a single habitat for example soil moisture

Host-specific insects that exploit different nutritional resources, two species of ladybird beetle mate exclusively on its own host plant

Question 32

Example of macrospatial isolation

Answer 32

Grillus pennysylcanicus prefers loamy soils and the grillus firmus prefers sandy soils which are found very far from each other

Question 33

Example of temporal isolation

Answer 33

The north American periodical circadias have different life cycles: 13 years and 17 years

They live in the same area but they arise at different times so the opportunity to mate happens only once in every 221 years.

Question 34

An example highlighting the importance of mating seasons

Answer 34

The fall field cricket reaches reproductive isolation in autumn

The spring field cricket reaches reproductive isolation in spring

They therefore never meet to mate

Question 35

Example for different breeding timings

Answer 35

Drosophila persimilis breed in the morning

drosophila pseudobscura breed in the evening

Question 36

What is an example of pollinator isolation

Answer 36

Nearly all of the 750 species of figs are pollinated by different wasp species

Question 37

Isolation of the monkeyflower

Answer 37

Two species of monkey flowers with different anthers and nectar volumes

Separated by there difference in pollinators

When in a lab they can form a hybrid and therefore pollinators are the only reproductive barrier