A Black Spot on Our Record: Invasion History of the Nonnative Blackspotted Topminnow (Fundulus olivaceus) in the Spring River Subbasin of Kansas, with a Comparison to Long-Term Trends in Prevalence of Blackstripe Topminnow (Fundulus notatus)

The Blackspotted Topminnow (Fundulus olivaceus) is not native to the Spring River subbasin (SRS) of Kansas, where it was first collected from Shoal Creek in the early 2000s. To date, little is known concerning the contemporary prevalence of Blackspotted Topminnow in the SRS of KS, or how prevalence of the closely related Blackstripe Topminnow (Fundulus notatus) in the SRS has varied since Blackspotted Topminnow invaded this system. To evaluate the contemporary prevalence of the Blackspotted Topminnow in the KS SRS, we sampled 55 sites using backpack electrofishing and seining during 2017-2020. We then compared long-term trends in occupancy and relative abundance of the Blackspotted and Blackstripe Topminnows in the KS SRS using four separate datasets collected during 1962-1964, 1993-1995, 1995-2013, and our contemporary dataset from 2017-2020. Between species comparisons of temporal trends were made for the entire SRS of KS, and for physiographic regions within the SRS that differed in habitat characteristics and Blackspotted Topminnow presence. In our contemporary survey, we detected the Blackspotted Topminnow at 11% of sites (6/55), including four Shoal Creek sites and two sites in the Spring River below Empire Lake. Blackstripe Topminnow prevalence was relatively stable in the SRS during 1962-2020, where it was most widespread and abundant within streams of the Cherokee Lowlands and Osage Cuestas. In contrast, between the 1995-2013 and 2017-2020 time periods Blackstripe Topminnow exhibited a declining trend in prevalence within the Ozark Plateau where it was sympatric with the Blackspotted Topminnow. This decline was not observed in the Ozark Plateau where Blackspotted Topminnow was absent. Declining Blackstripe Topminnow prevalence may be due to negative biotic interactions (e.g., competition; hybridization) with the Blackspotted Topminnow, or could be the result of unquantified environmental variation. Regardless, our research showed that the Blackspotted Topminnow is now an established nonnative in the SRS of KS. Consequently, further research of this species is necessary to determine how the invasion process proceeds regarding continued spread and potential concomitant ecological impacts.