SPECIES, ways to distinguish them

Exam 2 Lecture 12

UIC BioS 101 Nyberg

SPECIES

Many types of information are used to describe, delimit and separate species

Speaker Notes:

Distinctions among types is increasingly based on molecular phylogeny.

Exam 2 Lecture 12

UIC BioS 101 Nyberg

Reading Assignment

Chapter 26 Speciation
Species, taxa, kinds and types all have similar meanings.
Sometimes ‘species’ is used in field other than biology.

Speaker Notes:

Exam 2 Lecture 12

UIC BioS 101 Nyberg

What is a species?

Species is a name for a group of individuals that share many features.
- Your own dog has a name, a breed is a group of individuals similar enough to each other (and different from others) to get a name.
- In modern biology, a species name, ie,dog, groups all individuals that can potentially produce offspring together.

Speaker Notes:

The potential future unity is difficult to evaluate in the present as it is dependent on events in the future.

Exam 2 Lecture 12

UIC BioS 101 Nyberg

Species typically have many populations, often spatially distinct

Individuals of the species are rarely found everywhere within the mapped range.
Populations of a species are often separate for long times.
- Considered aquatic organisms- lakes and ponds are typically isolated.
Isolation leads to distinctness thru accumulation of neutral allelic variation.

Speaker Notes:

Patchiness is a term used to describe discrete, isolated populations.

Exam 2 Lecture 12

UIC BioS 101 Nyberg

Species have limited geographic ranges

Speaker Notes:

In practice the place that an individual is found is used in conjunction with morphology in most cases.

The geographic range of some species has changed fairly dramatically in historic times.

Exam 2 Lecture 12

UIC BioS 101 Nyberg

Continuity of Populations

It makes sense to include individuals in all populations which share an evolutionary future as well as a past into a single species.
The past can be studied, but the future is harder to predict.
Human movements of species to new places disrupts natural patterns.

Speaker Notes:

The world is becoming more uniform from place to place than it was in the past.

Exam 2 Lecture 12

UIC BioS 101 Nyberg

Limits of continuity in time

Two genes with a single difference can be traced backward thru time until they coalesce (=fuse) at a particular time, the time a mutation created the new sequence.
Species are not so simply distinguished, though we draw them that way in a phylogeny, where one lineage instantly becomes two at a node.

Speaker Notes:

Within a single line individuals separated by a long time can/should be considered different species.

Exam 2 Lecture 12

UIC BioS 101 Nyberg

Species Concepts

Technology has changed how we think of species. From old to recent we consider:
Morphospecies Concept
Biological Species Concept
Phylogenetic Species Concept

Speaker Notes:

Exam 2 Lecture 12

UIC BioS 101 Nyberg

Okanagana balli is the scientific name of the prairie cicada

Speaker Notes:

This species is restricted to original prairie habitats. The right picture is of a mating pair.

Exam 2 Lecture 12

UIC BioS 101 Nyberg

Rosa carolina is the scientific name of the Pasture rose

Speaker Notes:

The most common plant at the Woodworth Prairie

Exam 2 Lecture 12

UIC BioS 101 Nyberg

The Morphospecies Concept

Humans are a visual species and applying visual criteria is a ‘natural’ way to distinguish types.
Morphological features can be seen and preserved in dead individuals.
Preserved individuals in museums provided a reference collection, fostering commonality in name usage.

Speaker Notes:

We no longer need a whole dead individual to have DNA.

Exam 2 Lecture 12

UIC BioS 101 Nyberg

Morphospecies usefulness

Using morphology to define species enables one to name species that are extinct.
Morphological criteria can be applied to all individuals regardless of reproduction.
Degrees of separation are naturally recognized, including subspecies, varieties and breeds, but emphasis is always on TYPES.

Speaker Notes:

Different ways of defining species will lead to different names for some specimens.

Exam 2 Lecture 12

UIC BioS 101 Nyberg

Subspecies and varieties

Subspecies and varieties are finer levels of distinction than species.
Different subspecies within the same species are expected to be able to mate and produce offspring.
Subspecies are always differentiated based on morphology.

Speaker Notes:

There are no clear, agreed upon distinctions among subspecies, races & varieties.

Exam 2 Lecture 12

UIC BioS 101 Nyberg

Why abandon Morphospecies?

There are large morphological changes in development of individual and between sexes, so morphology is not effective at identifying biological continuity.
Single morphospecies have been found composed of multiple lineages separated by millions of years.

Speaker Notes:

Exam 2 Lecture 12

UIC BioS 101 Nyberg

Biological Species Concept

Reproductive isolation is the criteria that distinguish species. It is based on continuity and potential sharing.
- Individuals that mate and produce offspring should be in the same species even they don’t look alike.
- While theoretically strong this idea is difficult to apply in practice.

Speaker Notes:

The relationships of populations within species is difficult to evaluate.

Exam 2 Lecture 12

UIC BioS 101 Nyberg

Why abandon Biological Species Concept?

Many objects we want to classify can not be mated (fossils, dead specimens, etc.)
The biological species criteria applied to individuals with apomictic reproduction or obligate selfers creates too many ‘species’.
Matings between particular individuals may be unable to produce fertile offspring, even when they are obviously in same species?

Speaker Notes:

If the answer to the question is YES, then individuals are in same species.

Exam 2 Lecture 12

UIC BioS 101 Nyberg

Phylogenetic Species Concept

DNA sequence information:
- Can be obtained from small amounts of tissue, there is no need for living individuals.
- Measuring similarity of sequences is fairly straightforward.
- Programs for generating a phylogeny from sequences are available.
Large numbers of individuals can be processed by individuals with low levels of training.

Speaker Notes:

In some ways using phylogeny is closer to biological species, but the existence of long-term polymorphisms complicates the analysis.

Exam 2 Lecture 12

UIC BioS 101 Nyberg

Phylogenetic species concept limitations

The level of difference necessary to be a different species is not well defined, and it likely to vary among groups.
Polymorphisms within species are not always recent, so large differences can persist in individuals that can mate.

Speaker Notes:

Conflicts of Species Concepts

Speaker Notes:

This is a case where two different approaches lead to different answers.

Exam 2 Lecture 12

UIC BioS 101 Nyberg

Spatial Relations of Populations

Allopatric
- Populations living in different places.
- If there is no contact, they are obviously going their separate ways.
- Eventually, the separateness will lead to genetic distinctness.

Sympatric
- Populations that live in the ‘same place’ at the ‘same time’.
Sympatric Speciation
- Environmental change that selects for two different types.
- Special kinds of mutation which generate instant isolation.

Speaker Notes:

Exactly what criteria are needed to qualify as ‘sympatric’ are not well defined.

Exam 2 Lecture 12

UIC BioS 101 Nyberg

Histories of Populations -splitting

Both Merging and Splitting occur.
A population can be split into two (or more) populations by geological events.
The splitting of a population is described as vicariance.

Speaker Notes:

Vicariance in Big Bird

Speaker Notes:

Flightless birds differentiated after being isolated by continental drift.

Exam 2 Lecture 12

UIC BioS 101 Nyberg

Histories of Populations -merging

Populations that were spatially separated can become overlapping, when one or more of the populations expands.
This is called secondary contact.
Sometimes the populations unite into a single species.
Sometimes the hybrids are less viable than either populations.

Speaker Notes:

Hybrid Zone in Warblers

Exam 2 Lecture 12

UIC BioS 101 Nyberg

Speaker Notes:

My interpretation is that these two species are a single geographically differentiated species that were considered separate because polymorphism is so visual.

Exam 2 Lecture 12

UIC BioS 101 Nyberg

Species Conclusion

Biological populations are differentiated at all possible levels. This means that there is no single definition of “species” that will work for all people in all circumstances.
Our recognition of species (taxa) also reflects the distinctions people feel are valuable, what is special.

Speaker Notes:

Atoms and molecules are attributes of nature that people have to accept. Species are partially attributes of nature and partly what people understand as distinct.

Exam 2 Lecture 12

UIC BioS 101 Nyberg

Vocabulary

Taxa, taxon
Subspecies
Biological species concept
Morphospecies concept
Reproductive isolation

Phylogenetic species
Allopatric
Sympatric
Vicariance
Hybrid zone

Speaker Notes: