Post-Pleistocene differentiation in a Central Interior Highlands endemic salamander

Area of Science:

• Ecology and Evolutionary Biology
• Conservation Genetics
• Amphibian Research

Background:

• Understanding the impact of landscape changes on endemic species with limited dispersal is crucial.
• The Central Interior Highlands (CIH) is an area with high endemism, making it a key region for studying species' ecological and evolutionary history.
• The ringed salamander (Ambystoma annulatum) is an endemic species whose population structure across the CIH requires detailed characterization.

Purpose of the Study:

• To characterize the population genetic structure of the endemic ringed salamander (Ambystoma annulatum) across its distribution in the Central Interior Highlands (CIH).
• To infer the ecological and evolutionary history of Ambystoma annulatum by analyzing its population structure in relation to landscape changes.
• To investigate the influence of geologic history and post-European settlement on the genetic makeup of the species.

Main Methods:

• Sampling of 498 Ambystoma annulatum individuals across the species' distribution.
• Characterization of population genetic structure using nuclear microsatellite markers.
• Analysis of mitochondrial DNA (mtDNA) markers to complement nuclear data.

Main Results:

• Two strongly supported nuclear genetic clusters were identified: a northern cluster (Missouri Ozarks) and a southern cluster (Arkansas/Oklahoma Ozarks and Ouachita Mountains).
• Demographic models estimated population divergence approximately 2,700 years ago, correlating with post-Pleistocene landscape changes in the CIH.
• Limited contemporary gene flow was observed, with genetic differentiation influenced by landscape alterations.

Conclusions:

• The population genetic structure of Ambystoma annulatum is shaped by both ancient geologic history and recent human-induced landscape changes.
• Low mtDNA diversity suggests past population dynamics involving retraction into and expansion from refugial areas during Pleistocene and Holocene climate fluctuations.
• Decreased gene flow in recent times is likely a consequence of habitat fragmentation and alteration following European settlement.