Data from: Manmade barriers and augmentation drive spatial and temporal trends of genetic diversity and effective population size in a riverine fish

Man-made barriers impede fish movement up and downstream, between the
channel and floodplain, and from marginal habitats to those that promote
survival and reproductive output. Barriers also increase genetic isolation
resulting in loss of genetic variation. Species with drifting eggs and
larvae, like the endangered Rio Grande silvery minnow (Hybognathus
amarus), are especially susceptible to disruptions to demographic and
genetic connectivity. Using archived Rio Grande silvery minnow DNA from 25
temporal collections spanning 38 years, and targeted amplicon sequencing,
we show that unidirectional stream flow and longitudinal position of
populations affect patterns of Ne and genetic diversity. Ne is reduced in
the upstream-most reach (Angostura) and there is a strong correlation
between upstream and range-wide Ne suggesting impacts to the entire
population. In the absence of population augmentation, allelic diversity
was reduced upstream but stocking restored diversity. Long-term genetic
analysis indicates: (1) that there is no longer sufficient spawning and
rearing to maintain natural diversity in the Angostura reach; (2) upstream
movement of adults is insufficient to recover diversity; and/or (3) there
is higher variance in reproductive success in resident fish resulting in
small values of Ne; all consequences of a highly engineered and
disconnected river corridor. Similar impacts are predicted for species
with pelagic life histories in altered rivers, underscoring the need for
fish passage structures that facilitate connectivity and habitat
restoration aimed toward propagule retention in upstream reaches.
Long-term genetic data also show periodic recruitment bottlenecks compound
losses to genetic diversity imposed by river regulation that cannot be
restored by hatchery stocking alone.