Oligocene odyssey: Molecular phylogenetic analyses describe the origin and diversification of freshwater Gammarus in eastern North America

Aim: Members of the amphipod genus Gammarus have served as an excellent model for testing biogeographic hypotheses given the number of species within the genus and its unique history, with multiple taxa transitioning from marine to freshwater environments independently. However, while attention has been placed on Palearctic Gammarus, little is known about members in the Nearctic. Given trends observed within the genus, Gammarus from eastern North America (ENA) may represent another independent lineage, likely reaching the continent using a heretofore unknown pathway. We investigate the phylogenetic and evolutionary history of Gammarus spp. in this region.
Location: eastern North America
Taxon: Gammarus
Methods: Sequence data for two nuclear and two mitochondrial loci were obtained for 75 individuals, four of which are newly sequenced. Based on a concatenated dataset, phylogenetic trees were reconstructed using both Maximum likelihood and Bayesian inference. Bayesian trees were time-cali..., , , # Oligocene odyssey: Molecular phylogenetic analyses describe the origin and diversification of freshwater Gammarus in eastern North America

[https://doi.org/10.5061/dryad.905qfttvd](https://doi.org/10.5061/dryad.905qfttvd)

## Description of the data and file structure

Included here are raw tree files in either newick or nexus formats from all tree-building methodologies undertaken (IQTREE, MRBAYES, BEAST), results of the RASP analysis, and a concatenated sequence alignment, generated by SEQUENCEMATRIX.

### Files and variables

#### File: Cannizzaro\_and\_Berg\_ENA\_BEAST\_annotated.nexus

Description: Annotated BEAST tree.

#### File: Cannizzaro\_and\_Berg\_ENA\_Alignment\_Concatenated.nex

Description: Concatenated sequence alignment (nexus format)

#### File: Cannizzaro\_and\_Berg\_ENA\_ML\_tree.newick

Description: Raw Maximum-likelihood tree file from IQTREE

#### File: Cannizzaro\_and\_Berg\_ENA\_Mrbayes.newick

Description:Raw Bayesian tree file from MRBAYES

#### File: Canni...,