Monophyletic origin and unique dispersal patterns of domestic fowls.

With the aim of elucidating in greater detail the genealogical origin of the present domestic fowls of the world, we have determined mtDNA sequences of the D-loop regions for a total of 21 birds, of which 12 samples belong to red junglefowl (Gallus gallus) comprising three subspecies (six Gallus gallus gallus, three Gallus gallus spadiceus, and three Gallus gallus bankiva) and nine represent diverse domestic breeds (Gallus gallus domesticus). We also sequenced four green junglefowl (Gallus varius), two Lafayette's junglefowl (Gallus lafayettei), and one grey junglefowl (Gallus sonneratii). We then constructed a phylogenetic tree for these birds by the use of nucleotide sequences, choosing the Japanese quail (Coturnix coturnix japonica) as an outgroup. We found that a continental population of G. g. gallus was the real matriarchic origin of all the domestic poultries examined in this study. It is also of particular interest that there were no discernible differences among G. gallus subspecies; G. g. bankiva was a notable exception. This was because G. g. spadiceus and a continental population of G. g. gallus formed a single cluster in the phylogenetic tree. G. g. bankiva, on the other hand, was a distinct entity, thus deserving its subspecies status. It implies that a continental population of G. g. gallus sufficed as the monophyletic ancestor of all domestic breeds. We also discussed a possible significance of the initial dispersal pattern of the present domestic fowls, using the phylogenetic tree.

Decrements in auditory responses to a repeated conspecific song are long-lasting and require two periods of protein synthesis in the songbird forebrain.

Earlier work showed that playbacks of conspecific song induce expression of the immediate early gene ZENK in the caudo-medial neostriatum (NCM) of awake male zebra finches and that this response disappears with repeated presentations of the same stimulus. In the present study, we investigated whether repetitions of a song stimulus also elicited a decrement in the electrophysiological responses in the NCM neurons of these birds. Multiunit auditory responses in NCM were initially vigorous, but their amplitude decreased (habituated) rapidly to repeated stimulation, declining to about 40% of the initial response during the first 50 iterations. A similar time course of change was seen at the single unit level. This habituation occurred specifically for each song presented but did not occur when pure tones were used as a stimulus. Habituation to conspecific, but not heterospecific, song was retained for 20 h or longer. Injections of inhibitors of protein or RNA synthesis at the recording site did not affect the initial habituation to a novel stimulus, but these drugs blocked the long-term habituation when injected at 0.5-3 h and at 5.5-7 h after the first exposure to the stimulus. Thus, at least two waves of gene induction appear to be necessary for long-lasting habituation to a particular song.