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The evolution of alternative genetic systems in insects
1Department of Entomology, University of Massachusetts, Amherst, Massachusetts 01003, USA. bnormark@ent.umass.edu
Annual Review of Entomology
|September 11, 2002
Summary
Insect genetic systems are classified into three main types: diplodiploidy, haplodiploidy, and thelytoky. The study estimates over 900 independent origins of thelytoky, highlighting frequent evolutionary transitions in insect reproduction.
Area of Science:
- Entomology
- Evolutionary Biology
- Genetics
Background:
- Insects exhibit diverse reproductive strategies, broadly categorized into three primary genetic systems: diplodiploidy (diploid males), haplodiploidy (haploid males), and thelytoky (females only).
- Mixed genetic systems, involving facultative or cyclic transitions between thelytoky and other systems, also exist, adding complexity to insect reproduction.
Purpose of the Study:
- To present a comprehensive classification of insect genetic systems.
- To estimate the number of evolutionary transitions between these different genetic systems throughout insect evolution.
Main Methods:
- Review and synthesis of existing literature on insect genetic systems.
- Phylogenetic analysis and comparative methods to infer evolutionary transitions.
Main Results:
- Obligate thelytoky has evolved independently over 900 times from other systems.
- Transitions to cyclic thelytoky (5 origins) and obligate haplodiploidy (8 origins) are rarer.
- Evidence supports the role of maternally transmitted endosymbionts in the evolution of haplodiploidy.
Conclusions:
- Insect genetic systems demonstrate remarkable evolutionary lability, with frequent origins of thelytoky.
- The evolution of reproductive systems in insects is influenced by factors such as endosymbionts.
- Certain insect groups, like Sternorrhyncha, present unique inheritance systems that challenge current classifications.