Assessing hybridization between non-native <i>Procambarus clarkii</i> (Girard, 1852) and native <i>Procambarus troglodytes</i> (Le Conte, 1855) (Decapoda: Astacidea: Cambaridae) in Atlantic drainages of the southeastern USA

Abstract Crayfishes play important ecological and economic roles in the southeastern USA, with non-native crayfishes threatening many native species. While hybridization of crayfish species is observed in both wild and captive populations for some crayfishes, evidence for hybridization in the genus Procambarus Ortmann, 1905 is limited. The red swamp crayfish (Procambarus clarkii (Girard, 1852)) and the eastern red swamp crayfish (Procambarus troglodytes(Le Conte, 1855)) are two closely related crayfishes native to different basins in the southeastern USA. We used genetic markers to assess the potential for hybridization in these two crayfishes in the North Carolina and South Carolina, USA. A total of 292 specimens were collected with morphological identification distinguishing 134 P. clarkii and 158 P. troglodytes individuals from syntopic (i.e., co-occurring) and allopatric populations. Genetic microsatellite data was used to determine that no individuals were documented as hybrids in our collections and there was no indication of recent or rampant hybridization between P. clarkii and P. troglodytes at any of the sampling locations. A limited laboratory experiment showed successful mating and egg fertilization but failed to produce viable hybrid offspring. Although historical successful hybridization was not documented in our study, mating events between the two species resulting in inviable offspring may be having detrimental ecological consequences for populations of the native P. troglodytes that warrant additional exploration.