CoevolutionCoevolution

•• Reciprocal evolution of two or more species Reciprocal evolution of two or more species involved in a species interaction.involved in a species interaction.

•• Each species involved in a Each species involved in a coevolutionarycoevolutionarydynamic will have adaptations derived from dynamic will have adaptations derived from the species interaction.the species interaction.

Diffuse Coevolution Diffuse Coevolution -- A group of species evolve in response to anotherA group of species evolve in response to anothergroup of species, and vice versa.group of species, and vice versa.

-- fairly common in naturefairly common in nature

OneOne--onon--one Coevolutionone Coevolution-- A single species evolves in response to a secondA single species evolves in response to a secondspecies, and vice versa.species, and vice versa.

-- less common in natureless common in nature

AcaciaAcacia

acacia thornacacia thorn

BeltianBeltian bodiesbodies

Trees (Acacia)1. Large, hollow thorns2. Beltian bodies3. Maintain leaves in dry season

Ants (Pseudomyrmex)1. Aggressive toward all other species2. Feed only on Acacia3. Forage round the clock4. Maintain large colony

(reproduce year-round/multiple queens)

CoevolutionaryCoevolutionary EventsEvents

Experiment conducted by Dan Experiment conducted by Dan JanzenJanzen

ControlControl Ant RemovalAnt Removal((JanzenJanzen 1967)1967)

Immune Function of IntestineImmune Function of Intestine

•• One gram of intestinal contents One gram of intestinal contents contains contains 100 billion100 billion bacteria!bacteria!

•• Your intestine is the largest Your intestine is the largest lymphoid gland in the body, lymphoid gland in the body, secreting 3secreting 3--5 g of antibodies 5 g of antibodies per day.per day.

Intestinal BIntestinal B--cells produce antibodies for pathogens.cells produce antibodies for pathogens.

appendixappendix

Anaerobic BacteriaAnaerobic Bacteria1. Grow best under conditions of your intestine1. Grow best under conditions of your intestine

(e.g., diet, frequency of feeding, and temperature)(e.g., diet, frequency of feeding, and temperature)2. Prevent pathogenic bacteria from colonizing your2. Prevent pathogenic bacteria from colonizing your

intestineintestine

Mammals (e.g., Homo sapiens)Mammals (e.g., Homo sapiens)1. B1. B--1 Lymphocytes to regulate bacterial load1 Lymphocytes to regulate bacterial load2. Specialized regions of intestine (i.e., 2. Specialized regions of intestine (i.e., cecumcecum))

CoevolutionaryCoevolutionary EventsEvents

Coevolution of Pathogens & their HostsCoevolution of Pathogens & their Hosts

•• Pathogens damage tissue and Pathogens damage tissue and consume resourcesconsume resources

•• Host can potentially eliminate Host can potentially eliminate pathogen with its defensespathogen with its defenses

African Sleeping Sickness iscaused by Trypanosoma.

Variable Surface Glycoprotein (VSG)

Mammals (e.g., Mammals (e.g., Homo sapiensHomo sapiens))1. 1. Lymphocytes capable of recognizingLymphocytes capable of recognizing

TrypanosomaTrypanosoma

TrypanosomaTrypanosoma1. 1. FlagellarFlagellar PocketsPockets2. Variable Surface 2. Variable Surface GlycoproteinsGlycoproteins

The most curious part of the thing was, that the trees and The most curious part of the thing was, that the trees and the other things around them never changed their places at the other things around them never changed their places at all: however fast they went, they never seemed to pass all: however fast they went, they never seemed to pass anything. anything. ““I wonder if all of the things move along with us?I wonder if all of the things move along with us?””thought poor puzzled Alice. And the Queen seemed to thought poor puzzled Alice. And the Queen seemed to guess her thoughts, for she cried, guess her thoughts, for she cried, ““Faster! DonFaster! Don’’t try to talk!t try to talk!””

--Lewis Carroll, Lewis Carroll, Through the LookingThrough the Looking--GlassGlass

The Red Queen PhenomenonThe Red Queen Phenomenon