Spontaneous hybridization among invasive Poaceae in Hawai‘i: Chloris × pseudosagrana nothosp. nov. and Cenchrus × peregrinus nothosp. nov.

During grass surveys across the islands of Hawai‘i in 2022, two novel hybrids among non-native Poaceae were found growing on roadsides. Spontaneous hybridization was observed among Chloris barbata and C. divaricata on O‘ahu and among Cenchrus clandestinus and C. setaceus on Hawai‘i island. Morphological evidence initially suggested these plants may be hybrids and molecular analysis using the ITS and rpl32-trnL regions confirmed that the plants are hybrids and identified their parentage. These hybrids are named Chloris × pseudosagrana nothosp. nov. and Cenchrus × peregrinus nothosp. nov. No developed seeds could be found on either of these hybrids and they are suspected to be sterile F1 hybrids. The occurrence of hybridization events among other non-native species are also discussed.