Alicia Toon

The perfect invader: a parthenogenic crayfish poses a new threat to Madagascar’s freshwater biodiversity

In 2007 an unusual crayfish found in food markets in the capital of Madagascar was preliminarily identified as Procambarus ‘Marmorkrebs’: a new world taxa and the only decapod known to reproduce by parthenogenesis. We present information on the identity, distribution and ecology of this recent invader and attempt to evaluate the threat it poses to Madagascar’s biodiversity and to livelihoods. The species appears to be currently limited to the area close to Antananarivo, but is being sold alive on major transport routes. We present molecular evidence of its taxonomic relationships and confirm that the Procambarus present in Madagascar is indeed the parthenogenic taxa. We investigate its reproductive ecology and find Procambarus ‘Marmorkrebs’ to have an extremely high fecundity; more than six times that of the native crayfish Astacoides. The limited evidence we have suggests that this species poses a serious threat to freshwater biodiversity and that it is likely to damage human livelihoods (through its impact on fishing and possibly rice agriculture). More research is urgently needed but in the meantime action is needed to reduce the rate of spread before it is too late.

Multilocus analysis of honeyeaters (Aves: Meliphagidae) highlights spatio‐temporal heterogeneity in the influence of biogeographic barriers in the Australian monsoonal zone

Multilocus studies in phylogenetics and comparative phylogeography have the power to explore a broader spectrum of evolutionary questions than either discipline has alone. To examine the origins of sympatry in a group of closely related birds of mostly mesic eucalypt woodlands in Australia, we reconstructed the relationships among species of Entomyzon and Melithreptus honeyeaters (Aves: Passeriformes: Meliphagidae) using a mitochondrial marker, ND2, and six non‐coding nuclear loci (total 4719 base pairs). By sampling across the geographical range of each species, we studied not only their phylogenetic relationships to each other but also the spatial distribution of their genetic diversity. We tested several biogeographic hypotheses concerning the role of Pleistocene environmental change in Australia. Phylogenetic gene trees support the current understanding of E. cyanotis as the sister to Melithreptus. Non‐monophyly of M. lunatus in Australia’s southern temperate woodlands highlights the need for a revision of systematics within Melithreptus. Phylogeographic analysis of the three northern species in Australia’s monsoon tropics, M. gularis, M. albogularis and E. cyanotis, suggests that the roles of the Carpentarian and Torresian Barriers in shaping geographic structure in each of the species have been more complex and temporally dynamic than earlier morphology‐based arguments of vicariance had suggested. We discuss their roles as ecological filters as well as barriers.

Pleistocene refugia in an arid landscape: analysis of a widely distributed Australian passerine.

While many studies have documented the effect that glacial cycles have had on northern hemisphere species, few have attempted to study the associated effect of aridification at low latitudes in the southern hemisphere. We investigated the past effects that cyclic aridification may have had on the population structure and history of a widespread endemic Australian bird species, the Australian magpie (Gymnorhina tibicen). One thousand one hundred and sixty‐six samples from across its native range were analysed for mitochondrial control region sequence variation and variation at six microsatellite loci. Analysis of mitochondrial control region sequence data indicated monophyletic clades that were geographically congruent with an eastern and western region. The contemporary distribution of east and west clades is nonoverlapping but in close proximity. Populations were estimated to have diverged in the Pleistocene around 36 000 years ago. The putative Carpentarian and Nullarbor arid barriers appear to be associated with the divergence between east and west mainland populations. Nested clade analysis indicated a signature of range expansion in the eastern region suggesting movement possibly inland and northward subsequent to the last period of aridity. The island population of Tasmania was of very recent origin, possibly since sea levels rose 16 000 years ago. Given the east‐west structure, there was no congruence between morphology and recent history of this species indicating a lack of support for morphological taxa. Overall mitochondrial DNA and microsatellite variation suggest that increasing aridity and Pleistocene refugia played a role in structuring populations of the Australian magpie; however, the dispersal ability and generalist habitat requirements may have facilitated the movement of magpies into an almost contiguous modern distribution across the continent. This study supports the idea that Pleistocene aridification played an important role in structuring intraspecific variation in low latitudinal southern hemisphere avian species.

Phylogenetic position, systematic status, and divergence time of the Procarididea (Crustacea: Decapoda).

Bracken, H. D., De Grave, S., Toon, A., Felder, D. L. & Crandall, K. A. (2009). Phylogenetic position, systematic status, and divergence time of the Procarididea (Crustacea: Decapoda). —Zoologica Scripta, 39, 198–212.

High levels of extra-group paternity in a population of Australian magpies Gymnorhina tibicen: evidence from microsatellite analysis

Breeding systems vary widely in birds, from monogamous pairs through to complex group systems where subordinates assist breeding individuals to rear young each season. The Australian magpie varies geographically both in plumage patterns and social organization. Some populations of both eastern and western plumage forms are plural breeders with group size varying from three to over 15 mature individuals. This study used variation at microsatellite loci to determine the level of extra‐group paternity in a population of the western form near Perth in Western Australia. Extra‐group paternity was the highest recorded for any bird species to date (82%) and indicates that few offspring within a territory are sired by the social partner of the female. In addition, the data indicated that nearly 10% of juveniles were not the genetic offspring of any female within their territory, suggesting some intraspecific brood parasitism. Taken together, these findings are remarkable considering the highly territorial nature of the species and the extent of territorial defence practised by all members of the group towards extra‐group conspecifics during daylight hours.

Australia's arid-adapted butcherbirds experienced range expansions during Pleistocene glacial maxima.

A model of range expansions during glacial maxima (GM) for cold-adapted species is generally accepted for the Northern Hemisphere. Given that GM in Australia largely resulted in the expansion of arid zones, rather than glaciation, it could be expected that arid-adapted species might have had expanded ranges at GM, as cold-adapted species did in the Northern Hemisphere. For Australian biota, however, it remains paradigmatic that arid-adapted species contracted to refugia at GM. Here we use multilocus data and ecological niche models (ENMs) to test alternative GM models for butcherbirds. ENMs, mtDNA and estimates of nuclear introgression and past population sizes support a model of GM expansion in the arid-tolerant Grey Butcherbird that resulted in secondary contact with its close relative--the savanna-inhabiting Silver-backed Butcherbird--whose contemporary distribution is widely separated. Together, these data reject the universal use of a GM contraction model for Australias dry woodland and arid biota.

A new synthesis of the molecular systematics and biogeography of honeyeaters (Passeriformes: Meliphagidae) highlights biogeographical and ecological complexity of a spectacular avian radiation

The passerine family Meliphagidae (the honeyeaters) comprises 175–180 species in 40–50 genera. It is an iconic element of the Australo‐Papuan avifauna and also occurs in Indonesia and on remote Pacific Ocean islands. Building on previous molecular studies that have pioneered a renewed understanding of the familys circumscription and systematics, we present an updated phylogenetic and systematics synthesis of honeyeaters derived from 112 mostly Australian, New Guinean and Wallacean species‐ and subspecies‐rank taxa aligned across 9246 positions spanning four mitochondrial and four nuclear genes. We affirm many of the recent changes advocated to the groups genus‐level systematics and offer some further refinements. The groups radiation appears to coincide broadly with the aridification of Australia in the Miocene, consistent with the time of origin of diversification of extant lineages in several other groups of Australian organisms. Most importantly, the complexity of the biogeography underlying the groups spectacular radiation, especially within Australia, is now apparent. Foremost among such examples is the robust evidence indicating that multiple, independent lineages of honeyeaters, including several monotypic genera, are endemic to the Australian arid zone, presumably having diverged and evolved within it. Also apparent and warranting further study are the phenotypic diversity among close relatives and the remarkably disjunct distributions within some clades, perhaps implying extinction of geographically intermediate lineages. Given such complexity, understanding the evolution of this radiation, which has thus far been intractable, relies on integration of molecular data with morphology, ecology and behaviour.

Discordance between morphology and genetic structure among three plumage forms of the Australian Magpie

Abstract The present study examined the extent of gene flow and population genetic structure among the highly sexually dimorphic form of the Australian Magpie (Gymnorhina tibicen dorsalis) which is restricted to the southwestern corner of the continent, and neighbouring plumage forms in north-western and eastern Australia. A phylogenetic break in the mtDNA haplotype phylogeny was evident between all western and all eastern plumage forms. The inference is that dispersal between eastern and western Australia is limited by large areas of unfavourable habitat, which isolate the two plumage forms. In contrast, there is no evidence of historic genetic structure among plumage forms in Western Australia and so their distributions are not explained by historical isolation and independent evolution. The results are consistent with a primary origin hypothesis for the plumage differences between the varied and western black-back forms of the Australian magpie.

Are lice good proxies for host history? A comparative analysis of the Australian magpie, Gymnorhina tibicen, and two species of feather louse

Parasites have been recently advocated as useful proxies for unravelling a complex evolutionary history of a host. In the present study, two species of feather lice, Brueelia semiannulata and Philopterus sp. were analysed for mitochondrial variation and compared to mitochondrial and nuclear variation in their host, the Australian magpie Gymnorhina tibicen. Phylogenies constructed using maximum likelihood methods revealed geographic structuring for both species of feather lice and host. Our genetic analysis shows concordance of east–west structure between host and Philopterus sp. indicating that it is an informative proxy for host history. Analysis of the Philopterus sp. phylogeny also suggested cryptic structuring within the eastern magpie population that had not been previously realized through genetic analysis of the host. B. semiannulata however, did not show congruent phylogeographic structuring with the host. Rather than showing an east–west split between lineages, the phylogeny of B. semiannulata showed north–south geographic structuring. It is postulated that this incongruence may be due to ecological habitat differences and/or the dispersal ability of B. semiannulata.

Molecular systematics of two enigmatic genera Psittacella and Pezoporus illuminate the ecological radiation of Australo-Papuan parrots (Aves: Psittaciformes).

The platycercine parrots of Australia, usually recognized as the Platycercinae or Platycercini, are the broad-tailed parrots and their allies typified by the rosellas Platycercus spp. Debate concerning their circumscription has most recently centerd on the position of four genera, Neophema, Neopsephotus, Pezoporus and Psittacella, the last two having never been adequately included in sequence-based analyses. We use broad taxon sampling, mitochondrial and nuclear DNA sequence data from seven independent loci (two linked mitochondrial loci and six nuclear loci), and both gene tree and species tree approaches to reconstruct phylogenies and so determine the systematic placement all four genera. Analyses of two data sets, one of 48 taxa and five loci and one of 27 taxa and the same five plus three additional loci produced broadly congruent and consistently well-resolved phylogenies. We reject placement of any of these four genera within core platycercines. Pezoporus is closely allied to Neophema and Neopsephotus. These three genera are the likely sister group to core platycercines and we advocate their recognition as a subfamily. Psittacella is the sole extant representative of a lineage that branched very early in the history of Australo-Papuan parrot fauna and is not closely related to any of the mostly south-east Asian and Indonesian psittaculine taxa with which it is more often linked. We present a revised view of the extraordinary phylogenetic, phenotypic and ecological diversity that is the adaptive radiation of Australo-Papuan parrots. Finally, our analyses highlight the likely paraphyly of Mayrs (2008) Loricoloriinae.