Unit_2.2.1_Sociality_and_Eusociality

Unit Overview

• Unit Title: 2.2.1 Sociality and Eusociality

• Course: Biology 4415

• Instructor: Dr. Matthew Terry

• Institution: UTRGV

Introduction to Sociality

Solitary vs. Social

• Critical examination of the differences between solitary and social organisms

• Advantages of Sociality:

  • Increased protection from predators

  • Enhanced foraging success

  • Cooperative care for offspring

  • Improved efficiency in resource use

The Social Spectrum

• Group Living:

  • Ranges from solitary ancestors to highly social organisms

  • Key Terms:

    • Eusociality: A extreme form of social organization

    • Obligate Eusocial: Species that are always eusocial, unable to live solitarily

• Where do Humans fall?

  • Considered more solitary compared to other social species

Forms of Sociality

1. Aggregation

• WEAT: A broad classification used to describe group behaviors in organisms

2. Parental Care

a. Without Nesting

• Examples of species that provide care without a physical nest

b. With Nesting

• Details:

  • Loose Soil: Habitat for nesting

  • Air Pocket: An important feature for developing young

  • Phanaeus vindex:

    • Mating behavior and preparation of brood balls for laying eggs

    • Role of soilcasts in development

c. With Communal Nesting

• Example: Hymenoptera species that showcase this form of parental care

3. Subsociality

• Defined by parents maintaining a close association with offspring but not in a cooperative manner

• Morphological Feature:

  • Frontal horns as an adaptation in some species

4. Quasisociality

• Characteristics:

  • Communal nesting with a single generation

  • All individuals assist in brood rearing

  • All females can lay eggs

5. Semisociality

• Characteristics:

  • Also involves communal nesting and single generation

  • Brood care is cooperative but not all females reproduce

6. Eusociality

• Defining Features:

  • Living in large groups

  • Cooperative care of young

  • Division of reproductive labor

  • Generational overlap among individuals

Eusocial Organisms

Taxonomic Overview

• Phylum: Arthropoda

• Class: Insecta

• Orders with Eusocial Characteristics:

  • Isoptera: ~50 species eusocial

  • Hemiptera: ~6 eusocial species

  • Thysanoptera: Includes some eusocial species

  • Coleoptera: Ambrosia beetles as a notable species

  • Hymenoptera: Ants and bees as predominant eusocial insects

    • ~14,000 species but only 300-400 eusocial

• Subphylum: Crustaceae

• Class: Mammalia

• Notable Eusocial Species:

  • Synalpheus (Snapping shrimp)

  • Family Bathyergidae (Mole rats):

    • 10's of primitively eusocial species

    • Advanced eusocial species include naked mole rat and Damaraland mole rat