Black and Gray Frame

Lecture 9 Animal Behavior: Phylogenies and Determining the Origins of Behaviors

Evolutionary questions

Origin of trait

Why have some traits have spread and persisted while others have disappeared?

Phylogenies

What is a phylogeny?

Phylogenies

How constructed?

Use traits

Morphological characters

Molecular

Fossils

Which trait is more important?

Phylogenies

What does it mean to resolve a phylogeny?

Example of 2 phylogenies resolved and unresolved with mtDNA.

Unresolved

Resolved

Mimics

Original

How resolved?

Traits evolve over different time scales

Molecular clocks

MtDNA

Nuclear DNA

SNPs and junk DNA (within DNA)

Traits which are selected for/against can change rapidly

Problem: how do you know it isn't selected for?

Molecular vs Morphological Phylogenies

Comparison of the subgenera of Polistes phylogeny obtained by Carpenter's 1996 morphological study (Fig. 2.8) and the phylogeny obtained in the present study, including all morphological and molecular characters. Species included from each subgenus are listed in Table 1.

Arvalo et al. BMC Evolutionary Biology 2004 4:8 doi:10.1186/1471-2148-4-8

Morphological

Morphological and Molecular

Fossil vs Extant
Morphological Phylogenies

Two phylogenies, one using with characteristics from fossils (Dr. Michael Caldwell)

Is a resolved phylogeny right?

Not necessarily!

Observed patterns of occurrence of traits over evolutionary time

Convergent evolution

multiple occurrence of eye structure

Divergent evolution

Selected traits change rapidly

Concept

Certain traits arise by co-opting machinery for another trait

(similar to exaptation)

How determine the origin of a trait?: Bower building style

Bower birds

Males construct bowers to attract females

Several species of bower birds

Different construction

How determine the origin of a trait? Bower building style

Several species of bower birds

Different construction of bowers

How determine the origin of a trait? Bower building style

Compare occurrence among species in a phylogeny constructed with other characters

Independent test

Supports origin of bower on forest floor

How determine the origin of a trait?: Preference for long fin

Behavior: test response of organisms to character not in the phylogeny

Artificial character trigger ancestral response?

How determine the origin of a trait? Preference for long fin

Ancestor (no fin)

Modern day species (no fin)

Derived species (fin)

How determine the origin of a trait? Preference for long fin

How determine the origin of a trait? Preference for long fin

Seemingly likely originof fin preference

How determine the origin of a trait? Preference for long fin

Test whether females of extant species prefer males with fins

They do!

Conclusion preference for fish fins arose before ancestral species:

Seemingly likely originof fin preference

Origin of fin preferencesupported by data

How determine the origin of a trait? Crests on birds

Behavior: test response of organisms to character not in the phylogeny

Artificial character trigger ancestral response?

Crests are not found in species

Determining the Origins of Behaviors

Existing least auklet males:

Test males w/crests:

Determining the Origins of Behaviors

Results of female preference

These don't exist!

Determining the Origins of Behaviors

Results of female preference

Conclusion: preference is ancestral

These don't exist!

Sensory exploitation

Males exploiting non-sexual triggers of female for reproduction

Cichlid fish (guppies)

Orange fruits

rare

Lots of energy (which is in demand)

Some orange spotted males (must eat food to acquire pigments)

Females with higher rate of pecking at orange disk

Have higher preference for orange males

Suggests males are exploiting female trigger

Summary

Phylogenies

Dependence on traits

How resolve

Observed patterns of trait occurrence

Methods of determining Origin of traits

Comparative phylogenies

Style of bowers made by Bower birds

Test for residual ancestral preferences

Fish Fin

Bird crests

Concept: Sensory Exploitation

Selection (find orange fruits), males (orange spots)