A study of gross morphological and histological syringeal features of true francolins (Galliformes: Francolinus, Scleroptila, Peliperdix and Dendroperdix spp.) and spurfowls ( Pternistis spp.) in a phylogenetic context

Abstract

Most modern taxonomic treatments of francolins consider the 41 currently recognized species as congeneric, forming the largest genus of terrestrial gamebirds (Order Galliformes). Some recent studies, based on molecular, ecological and behavioural characters have challenged this view, suggesting that they comprise two distantly related, monophyletic groups comprising. First, there are ‘true’ francolins’ (grouped within four genera Francolinus, Dendroperdix, Peliperdix and Scleroptila) that are relatively small, ground-roosting birds which give whistling and musical calls. Second are the spurfowls (placed into a single genus Pternistis) which unlike francolins are large birds that generally roost in trees and give raucous and grating calls. This study explores evidence from the gross morphological and histological syringeal anatomy of ‘true’ francolins, spurfowls and their putative sister taxa to test whether differences in syringeal morphology were concordant with an independently generated evolutionary hypothesis. The main syringeal differences found were the presence of shield- versus diamond-shaped tympanum among francolins and spurfowls respectively. The first bronchial half rings are relatively heavily mineralized among francolins except in Dendroperdix sephaena while almost no mineral deposition was observed in these rings among spurfowls. Histologically, francolins generally have a small, rounded pessulus (with the exception of D. sephaena which has a rounded but larger pessulus) contrary to the larger pessulus observed among spurfowls which is rounded and triangular in Pternistis capensis and P. natalensis respectively. Both gross and histological anatomical similarities within, and differences between, francolin and spurfowl syringes support the division of francolins into ‘true’ francolins and spurfowls, and reflects the previously proposed relationships with other sister species. However, as with other aspects of its organismal biology, D. sephaena shows features that are intermediate between francolins and spurfowls.