Vocal dialects in parrots: patterns and processes of cultural evolution

Abstract

Vocal dialects have fascinated biologists for over 50 years. This mosaic pattern of geographic variation in learned vocalizations was first described in a songbird, and since that time, most studies investigating dialects have focused on songbird species. Here we examine patterns of geographic variation in the calls of a different group of vocal learning birds, the parrots (Order Psittaciformes). We summarize the growing literature on vocal variation in parrots, and complement this review with a survey of variation in the genus Amazona using calls from sound libraries. We find strikingly similar patterns to those previously found in songbirds. Over 90% of parrots examined in the literature, and 69% of Amazona species surveyed, showed geographic variation consistent with a propensity to share local call types. This trait is evolutionarily labile and widespread; within Amazona most clades contained species with and without geographic variation, and most major lineages of parrots include representatives with dialects. We found little support for the long-standing hypothesis that dialects isolate populations and thus generate genetic differences among populations. Instead, most studies support the idea that dialects are maintained by social benefits of matching local call types, a finding that has implications for the management of captive and endangered populations. Considerable scope remains for studies that experimentally test hypotheses for the exact nature of these benefits, as well as studies that employ comparisons among species, to understand how the interplay between ecology, social dynamics and vocal learning capacities produces different patterns of variation across the parrots.

The rise and fall of dialects in northern elephant seals

“…In some cases, geographical variation is maintained by assortative mating through female choice, which contributes to reduced gene flow between different populations [12,14,15] and eventually leads to speciation [4,16]. In other instances, dialects may be adaptive to varying social or ecological landscapes, and continue to diverge between populations over time [17,18]. Alternatively, dialects may arise as epiphenomena of other evolutionary processes (e.g.…”

Subspecies in the Sarus Crane Antigone antigone revisited; with particular reference to the Australian population

“…lower than today [74], permitting development of a savanna corridor that extended both north and south of the equator across the Sunda plain [75], much of which would have been lost by rising sea levels at the start of the Holocene (about 10,000 years ago). In an Australian context, this corridor [76] would have ended not far north of the Pleistocene Lake Carpentaria, around which it is thought there would have been savannas structurally similar to those used by Sarus Cranes in northern Australia. It is also true that lower sea levels would have narrowed the distance between the Philippines, Borneo/Peninsula Malaya (via Palawan) and Indochina [77] and hence potentially also brought A. a luzonica and A. a. sharpii into closer proximity.…”

Low Geographic and Subspecific Variation in the Loud Call of the Widespread and Phenotypically Cryptic Northern Lesser Galago (Galago senegalensis) Suggests Taxonomic Uniformity

“…Geographic variation and dialects in vocalizations have been described within many species of vertebrates (e.g., Anura [Velásquez, 2014]; Psittaciformes [Brigham and Cebek, 1989]; Cetacea [Ford, 1991]; Chiroptera [Wright and Dahlin, 2018]; Rodentia [Slobodchikoff et al, 1998]). Intraspecies variation arises when differences in acoustic structure are larger among populations than within populations.…”