Host-specific phenotypic variation of a parasite co-introduced with invasive Burmese pythons.

Invasive Burmese pythons (Python bivittatus Kuhl, 1820) have introduced a lung parasite, Raillietiella orientalis, (Hett, 1915) from the python's native range in Southeast Asia to its introduced range in Florida, where parasite spillover from pythons to two families and eight genera of native snakes has occurred. Because these novel host species present a diversity of ecological and morphological traits, and because these parasites attach to their hosts with hooks located on their cephalothorax, we predicted that R. orientalis would exhibit substantial, host-associated phenotypic plasticity in cephalothorax shape. Indeed, geometric morphometric analyses of 39 parasites from five host species revealed significant variation among host taxa in R. orientalis cephalothorax shape. We observed differences associated with host ecology, where parasites from semi-aquatic and aquatic snakes exhibited the greatest morphological similarity. Morphological analyses of R. orientalis recovered from invasive pythons, native pit vipers, and terrestrial snakes each revealed distinct shapes. Our results suggest R. orientalis can exhibit significant differences in morphology based upon host species infected, and this plasticity may facilitate infection with this non-native parasite in a wide array of novel squamate host species.