Unit_2.2.3_Origin_and_Evolution_of_Eusocial_Insects

Unit Overview

• Unit Title: Origin and Evolution of Eusocial Insects

• Course: Biology 4415

• Instructor: Dr. Matthew Terry

• University: UTRGV

Eusocial Insects

• Eusocial insects are characterized by their social structure and cooperative behavior.

Hymenoptera

• Definition: An order of insects that includes bees, wasps, and ants.

• Important for understanding the origins of social behavior in insects.

Key Concepts Related to Hymenoptera

• Haplodiploid: A genetic system where males are haploid (one set of chromosomes) and females are diploid (two sets of chromosomes).

• Polyphenism: The phenomenon where a single genotype can produce multiple phenotypes depending on environmental conditions.

Origins of Eusociality

• Multiple origins of eusociality have been observed in different species.

• Intermediate Forms: Studying these forms helps clarify the evolution of complex social behaviors.

Group Selection and Kin Selection

• Group Selection: A theory that emphasizes the role of natural selection at the group level in the evolution of social behaviors.

• Kin Selection: A concept that explains how behaviors that benefit relatives can increase the overall genetic success of a species.

Relatedness in Eusocial Insects

• Visual representations clarify genetic relatedness among individuals in a hive:

  • Diploid female bee (worker)

    • Relatedness to:

      • Own son: 0.5

      • Sister: 0.75

      • Half-sister: 0.375

      • Son of full sister: 0.375

      • Son of half-sister: 0.125

• Diagrams illustrate processes like meiosis and fertilization affecting these relationships.

Maternal Manipulation

• A strategy where the mother influences the fate of her offspring to promote cooperation and social structures within colonies.

Mutualism

• Considered in Hymenoptera, where different species benefit mutually from their interactions, contributing to the evolution of cooperative behaviors.

Isoptera (Termites)

• Order including termites, which share some sociobiological traits with Hymenoptera.

Characteristics of Isoptera

• XX/XY Chromosome System: Different genetic sex determination system compared to Hymenoptera.

• Nutrient Poor Diet: Termites rely on wood and other cellulose materials which are low in nutrients.

Social Structures in Isoptera

• Patch Distribution: How food sources are distributed affects colony dynamics.

• Trophallaxis: The process of sharing food or other fluids among individuals in a colony, enhancing cooperation.

Evolutionary Relationships

• Comparison of Isoptera (termites) with other orders like Dictyoptera, Mantodea, and Blattodea.

• Cryptocercus: Mentioned as a related group illustrating the evolutionary links between termites and roaches.

Inquilines and Mimicry

• Inquilines: Organisms that live in or depend on the nests of eusocial insects.

• Mimicry: The evolutionary phenomenon where one species evolves to resemble another, often for protective purposes.

Maintenance of Eusociality

• Factors that help sustain eusocial structures in insect populations, vital for studying their complex social behaviors.