Cryptic species in putative ancient asexual darwinulids (Crustacea, Ostracoda)

Area of Science:

• Evolutionary biology
• Genetics
• Zoology

Background:

• Asexual reproduction in taxa prevents the application of the classic Biological Species Concept.
• Investigating species boundaries in ancient asexual ostracods is crucial for understanding their evolutionary history.

Purpose of the Study:

• To apply the evolutionary genetic (EG) species concept to identify species boundaries and cryptic diversity in ancient asexual ostracods.
• To compare the utility of mitochondrial COI and nuclear ITS2 DNA sequences for detecting cryptic species.

Main Methods:

• Utilized DNA sequencing of the mitochondrial COI gene and the nuclear ITS2 region.
• Employed the K/θ method and the General Mixed Yule Coalescent (GMYC) model to detect cryptic species.
• Analyzed five morphospecies from the ostracod genera Penthesilenula and Darwinula.

Main Results:

• Confirmed species existence in all five darwinulid morphospecies, revealing substantial cryptic diversity.
• Identified up to seven cryptic species within Penthesilenula brasiliensis and five to six within Darwinula stevensoni.
• Observed that cryptic species generally align with continental distributions and can coexist locally.

Conclusions:

• The evolutionary genetic (EG) species concept effectively recognizes species and cryptic diversity in ancient asexual ostracods.
• Mitochondrial COI gene sequences proved more effective than ITS2 for identifying cryptic species in this group.
• The discovery of extensive cryptic diversity significantly expands biodiversity estimates for asexual ostracods, prompting further research into speciation drivers beyond geographic isolation.