Influences of oceanic islands and the Pleistocene on the biogeography and evolution of two groups of Australasian parrots (Aves: Psittaciformes: Eclectus roratus, Trichoglossus haematodus complex). Rapid evolution and implications for taxonomy and conservation

Abstract

The Australasian region is a centre of biodiversity and endemism, mainly based on the tropical climate in combination with the large amount of islands. During the Pleistocene, islands of the Sahul Shelf (Australia, New Guinea, Aru Islands) had been part of the same land mass, while islands within the Wallacea (Lesser Sunda Islands, Moluccas, Sulawesi etc.) remained isolated. We investigated biogeographical avian diversification patterns of two species complexes across the Wallacea and the Sahul Shelf: the Eclectus Parrot Eclectus roratus Wagler, 1832, and the Rainbow Lorikeet Trichoglossus haematodus Linnaeus, 1771. Both species are represented by a large number of described geographical subspecies. We used mitochondrial cytochrome b (cyt b) sequences for phylogenetic and network analysis to detect biogeographic roles of islands and avian diversification patterns. The number of threatened taxa in this region is increasing rapidly and there is an urgent need for (sub-)species conservation in this region. Our study provides first genetic evidence for treating several island taxa as distinct species. In both species complexes similar genetic patterns were detected. Genetic diversification was higher across the islands of the Wallacea than across the islands of the Sahul Shelf. Divergence in E. roratus can be dated back about 1.38 million years ago, whereas in the younger T. haematodus it was 0.80 million years ago. Long distance dispersal was the most likely event for distribution patterns across the Wallacea and Sahul Shelf. The geographic origin of the species-complex Eclectus roratus spp. is supposed to be Wallacean, but for the species-complex Trichoglossus haematodus spp. it is supposed to be non-Wallacean. Trichoglossus euteles, so far considered a distinct species, clearly belongs to the Trichoglossus-haematodus-complex. The only case of sympatry in the complex is the distribution of T. (h.) euteles and T. h. capistratus on Timor, which means a rapid evolution from one ancestor into two distinct species within only 800,000 years. For all other taxa a Checkerboard distribution pattern is present. In this complex, 8 taxa are already treated as separate species (del Hoyo et al. 2014). Based on genetic evidence, the following populations are supported to represent phylogenetic units: (1) N New Guinea (haematodus) incl. Biak (rosenbergii), Bismarck Archipelago (massena), and New Caledonia (deplanchii); (2) Flores (weberi); (3) E Australia (moluccanus) incl. Aru Islands (nigrogularis) and S New Guinea (caeruleiceps); (4) N Australia (rubritorquis); (5) Timor 1st lineage (capistratus) incl. Sumba (fortis); (6) Bali and Lombok (mitchellii); (7) Sumbawa (forsteni); (8) Timor 2nd lineage (euteles). Those 8 phylogenetic units are not identical to the 8 species listed by del Hoyo et al. (2014). Several populations on smaller islands are under decline, a separate species status may lead to a higher conservation status in both species complexes, which are currently listed as “Least Concern”. Eclectus roratus is currently treated as monospecific. Based on genetic evidence, the following populations are suggested being treated as valid species: (1) Sumba (Eclectus cornelia), (2) Tanimbar Islands (E. riedeli), (3) Moluccas (E. roratus), and (4) New Guinea (E. polychloros incl. Aru Islands (E. aruensis), and Solomon Island (E. solomonensis).

Partial replacement of Rainbow Lorikeets Trichoglossus haematodus moluccanus by hybrid lorikeets in Hobart, Tasmania

“…Rainbow Lorikeets observed in this study appeared typical of those native to eastern Australia (Braun et al 2017), consistent with photographs of Tasmanian Rainbow Lorikeets in Gordon (2014). Trapping was effective at reducing their numbers in the study area, but hybrids subsequently became more numerous and diverse in form.…”

“…BirdLife International 2018) as a species restricted to eastern and south-eastern Australia (i.e. T. moluccanus) and by others as part of a species complex that ranges across coastal regions of eastern and northern Australia, as well as islands to the north between Bali and New Caledonia (Braun et al 2017). There is a feral population of the Eastern Rainbow Lorikeet (herein 'Rainbow Lorikeet') around Perth, Western Australia, that began with fewer than 10 birds in the 1960s but reached 8400 by 2005 (Chapman 2005) and now numbers >40 000 (BirdLife Western Australia 2017).…”

DNA Analyses Have Revolutionized Studies on the Taxonomy and Evolution in Birds

“…In Fringilla coelebs, Cyanistes caeruleus, Erythacus rubecula, Regulus regulus, Sylvia melanocephala, and others we could define new island specific subspecies (see references in [29,30]). A similar diversification can be seen on the Island archipelago of the Wallace zone in Australasia [31]. However, if we look at bird population on the Aegean Islands in Greece or Turkey (except for Cyprus), little or no differentiation can be seen [32].…”

Advancing Genetic Methods in the Study of Parrot Biology and Conservation

“…The species is the widely accepted default unit used for evaluating conservation status (e.g., in the IUCN Red List), hence defining species and resolving taxonomic uncertainties by genetic techniques is important for conservation [105]. Active speciation of parrots on islands is most readily evident in Australasia, as shown by the Eclectus roratus and Trichoglossus haematodus complexes [106]. In such cases of dynamic evolution, wider sampling and genetic data of finer resolution are often needed to resolve phylogenetic relationships [107].…”