Avian Hybridization and Allopatry in the Region of the Einasleigh Uplands and Burdekin-Lynd Divide, North-eastern Queensland

Abstract

The Einasleigh Uplands and Burdekin-Lynd Divide comprise an elevated section of the Great Dividing Range in north- eastern Queensland. About twenty avian species of eucalypt forest, woodland and grassland habitats have range gaps, hybrid zones or stepped size-clines in the region of these uplands. Species and species-pairs with a discontinuous or partly discontinuous range include the Lemon-bellied Flycatcher Microeca flavigaster, Restless Flycatcher Myiagra inquieta, White-gaped Honeyeater Lichenostomus unicolor, Yellow Honeyeater Lichenostomus flavus, Fuscous/Yellow-tinted Honeyeaters Lichenostomus fuscus/flavescens, Bar-breasted Honeyeater Ramsayornis fasciatus, Crimson Finch Neochmia phaeton, Star Finch Neochmia ruficauda and Chestnut-breasted Mannikin Lonchura castaneothorax. Those with a hybrid zone are the Squatter Pigeon Petrophassa (Geophaps) scripta, Pale-headed Rosella Platycercus adscitus, Brown Treecreeper Climacteris picumnus, Black-chinned Honeyeater Melithreptus gularis, Striated Pardalote Pardalotus striatus and Black-throated Finch Poephila cincta. Stepped size-clines or sharp morphological changes occur in the Brown Goshawk Accipiter fasciatus, Barking Owl Ninox connivens, Masked Owl Tyto novaehollandiae, Tawny Frogmouth Podargus strigoides and Laughing Kookaburra Dacelo gigas. Though some of the hybrid zones and steps might have been produced by nearby geographical barriers consisting of low rainfall salients, the upland-divide is an active barrier at present. A cooler climate in the upland-divide now, and presumably in past times, appears to be the cause of present and past range gaps because relevant habitats are continuous throughout north-eastern Queensland. Two taxa, Accipiter fasciatus and Melithreptus gularis, might each be composed of two species; because the small (didimus) and large (fasciatus) forms of A. fasciatus possibly both occur in tropical Australia throughout the year rather than only in winter when the large form is presumed to be a southern migrant; and the evidence for hybridization between the altitudinal vicariant forms gularis and laetior is equivocal. Most geographical barriers between isolated avian populations on the Australian mainland to consist of arid or low-rainfall belts extending to the coast but other cold upland sections of the Great Dividing Range besides the Einasleigh Uplands and Burdekin-Lynd have operated as barriers. These include the McPherson Range and Blue Mountains-Snowy Mountains chain.