Eastern banded killifish (Fundulus diaphanus diaphanus) in Lake Michigan and connected watersheds: The invasion of a non-native subspecies

Biological invasions can produce severe ecological impacts at both large spatial scales between distantly related species and also smaller spatial scales between conspecifics. We investigated here a potential intraspecific invasion within Lake Michigan and adjacent waters. Banded killifish (Fundulus diaphanus) experienced population increases and spread into novel habitats over recent decades in this region, but managers and policy makers were uncertain if these fish were native western banded killifish (F. d. menona) or instead an invasion by non-native eastern banded killifish (F. d. diaphanus). We applied mitochondrial DNA (mtDNA) barcoding and population genetic analyses to investigate the identity of these fish. We found that new banded killifish populations were the eastern subspecies, including mtDNA haplotypes from the remote mid-Atlantic region, suggesting some introductions from anthro-pogenic pathways (e.g., live bait trade) rather than only spread from connected, downstream waters (e.g., Lake Erie). Further, population genetic analyses identified eastern banded killifish in our focal region as having low genetic diversity relative to their native range, and relative to western banded killifish pop-ulations. Lastly, we found non-native eastern banded killifish were associated with Lake Michigan and connected waters, rather than isolated kettle lakes, and primarily occurred at clearer sites potentially affected by dreissenid mussel invasions. More research is needed on the causes and consequences of east-ern banded killifish invasions in Lake Michigan and adjacent waters, including an emphasis on their risk to the conservation of western banded killifish.& COPY; 2023 International Association for Great Lakes Research. Published by Elsevier B.V. All rights reserved.

Automated summary

This study examined a potential intraspecific invasion in Lake Michigan and adjacent waters. It found that new populations of banded killifish were the eastern subspecies, with lower genetic diversity compared to the western subspecies. Non-native eastern banded killifish were predominantly found in clear sites affected by dreissenid mussel invasions, highlighting the potential risk to the conservation of the native western banded killifish.