Ancient mitochondrial DNA and morphology elucidate an extinct island radiation of Indian Ocean giant tortoise (Cylindrapsis)

Ancient mitochondrial DNA sequences were used for investigating the evolution of an entire clade of extinct vertebrates, the endemic tortoises (Cylindraspis) of the Mascarene Islands in the Indian Ocean. Mitochondrial DNA corroborates morphological evidence that there were five species of tortoise with the following relationships: Cylindraspis triserrata ((Cylindraspis vosmaeri and Cylindraspis peltastes) (Cylindraspis inepta and Cylindraspis indica)). Phylogeny indicates that the ancestor of the group first colonized Mauritius where speciation produced C. triserrata and the ancestor of the other species including a second sympatric Mauritian form, C. inepta. A propagule derived from this lineage colonized Rodrigues 590 km to the east, where a second within-island speciation took place producing the sympatric C. vosmaeri and C. peltastes. A recent colonization of Réunion 150 km to the southwest produced C. indica. In the virtual absence of predators, the defensive features of the shells of Mascarene tortoises were largely dismantled, apparently in two stages. 'Saddlebacked' shells with high fronts evolved independently on all three islands. This and other features, such as a derived jaw structure and small body size, may be associated with niche differentiation in sympatric species and may represent a striking example of parallel differentiation in a large terrestrial vertebrate. The history of Mascarene tortoises contrasts with that of the Galápagos, where only a single species is present and surviving populations are genetically much more similar. However, they too show some reduction in anti-predator mechanisms and multiple development of populations with saddlebacked shells.

Genetic monogamy in the absence of paternity guards: the Capricorn silvereye, Zosterops lateralis chlorocephalus, on Heron Island

We investigated the genetic mating system of a socially monogamous passerine bird, the Capricorn silvereye Zosterops lateralis chlorocephalus, on an island of the Great Barrier Reef. There were no cases of extrapair paternity (EPP) among 122 offspring from 53 broods detectable by minisatellite or microsatellite DNA fingerprinting. Behavioral observations of paired birds showed that this was not a consequence of efficacious paternity guards and that females did not engage in extrapair copulation (EPC). Frequency of intrapair copulations was also low, with only 14 cases observed during 199 hours of observations of the 11 focal pairs in the fertile periods of females, and this was consistent with anatomical features of the cloacal protuberance in males. In this population, young birds form life-time pair bonds soon after gaining independence but females are obviously not attempting EPC possibly to redress this early mate choice. This is despite the fact that they breed in high density with a synchronous start and asynchronous spread of laying in a protracted season and males do not positively exhibit mate guarding behavior when females are fertile. Our results support high fidelity of socially monogamous birds on islands and are consistent with the hypothesis that sexual selection is reduced where genetic variation in fitness is limited.

A classification of subantarctic Heard Island vegetation

The vascular and bryophyte floras of subantarctic Heard Island were classified using cluster analysis into six vegetation communities: Open Cushion Carpet, Mossy Feldmark, Wet Mixed Herbfield, Coastal Biotic Vegetation, Saltspray Vegetation, and Closed Cushion Carpet. Multidimensional scaling indicated that the vegetation communities were not well delineated but were continua. Discriminant analysis and a classification tree identified altitude, wind, peat depth, bryophyte cover and extent of bare ground, and particle size as discriminating variables. The combination of small area, glaciation, and harsh climate has resulted in reduced vegetation variety in comparison to those subantarctic islands north of the Antarctic Polar Front Zone. Some of the functional groups and vegetation communities found on warmer subantarctic islands are not present on Heard Island, notably ferns and sedges and fernbrakes and extensive mires, respectively.

Genetic consequences of sequential founder events by an island-colonizing bird

The importance of founder events in promoting evolutionary changes on islands has been a subject of long-running controversy. Resolution of this debate has been hindered by a lack of empirical evidence from naturally founded island populations. Here we undertake a genetic analysis of a series of historically documented, natural colonization events by the silvereye species-complex (Zosterops lateralis), a group used to illustrate the process of island colonization in the original founder effect model. Our results indicate that single founder events do not affect levels of heterozygosity or allelic diversity, nor do they result in immediate genetic differentiation between populations. Instead, four to five successive founder events are required before indices of diversity and divergence approach that seen in evolutionarily old forms. A Bayesian analysis based on computer simulation allows inferences to be made on the number of effective founders and indicates that founder effects are weak because island populations are established from relatively large flocks. Indeed, statistical support for a founder event model was not significantly higher than for a gradual-drift model for all recently colonized islands. Taken together, these results suggest that single colonization events in this species complex are rarely accompanied by severe founder effects, and multiple founder events and/or long-term genetic drift have been of greater consequence for neutral genetic diversity.

Microevolution in island forms: the roles of drift and directional selection in morphological divergence of a passerine bird

Theory predicts that in small isolated populations random genetic drift can lead to phenotypic divergence; however this prediction has rarely been tested quantitatively in natural populations. Here we utilize natural repeated island colonization events by members of the avian species complex, Zosterops lateralis, to assess whether or not genetic drift alone is an adequate explanation for the observed patterns of microevolutionary divergence in morphology. Morphological and molecular genetic characteristics of island and mainland populations are compared to test three predictions of drift theory: (1) that the pattern of morphological change is idiosyncratic to each island; (2) that there is concordance between morphological and neutral genetic shifts across island populations; and (3) for populations whose time of colonization is known, that the rate of morphological change is sufficiently slow to be accounted for solely by genetic drift. Our results are not consistent with these predictions. First, the direction of size shifts was consistently towards larger size, suggesting the action of a nonrandom process. Second, patterns of morphological divergence among recently colonized populations showed little concordance with divergence in neutral genetic characters. Third, rate tests of morphological change showed that effective population sizes were not small enough for random processes alone to account for the magnitude of microevolutionary change. Altogether, these three lines of evidence suggest that drift alone is not an adequate explanation of morphological differentiation in recently colonized island Zosterops and therefore we suggest that the observed microevolutionary changes are largely a result of directional natural selection.

The archaeology of the Peel Island Lazaret: Part 1: Survey

An archaeological survey on Peel Island in Moreton Bay, southeast Queensland, was conducted to assist the conservation planning for the Peel Island Lazaret (PIL), one of a number of institutions housed on the island during the nineteenth and twentieth centuries. The survey revealed a patteming of artefacts across the island as well as landscape modification related to its Aboriginal and European institutional uses.

Monostephanostomum georgianum n. sp (Digenea : Acanthocolpidae) from Arripis georgianus (Valenciennes) (Perciformes : Arripidae) off Kangaroo Island, South Australia, with comments on Monostephanostomum Kruse, 1979 and Stephanostomum Looss, 1899

Monostephanostomum georgianum n. sp. is described from Arripis georgianus off Kangaroo Island, South Australia. It differs from its congeners by the presence of a short second row of oral spines. M. manteri Kruse, 1979 is reported from A. georgianus off southern Western Australia and Kangaroo Island, South Australia and A. trutta off northern Tasmania. It is considered that the other two species, M. yamagutii Ramadan, 1984 and M. krusei Reimer, 1983, should probably be removed from this genus. Two new combinations are formed, M. gazzae (Shen, 1990) n. comb. (from Stephanostomum) and M. mesospinosum (Madhavi, 1976) n. comb. (from Stephanostomum). A key to the four recognised species of Monostephanostomum is given.

Production of mosquitoes in rainwater tanks and wells on Yorke Island, Torres Strait: Preliminary study

The Torres Strait in northernmost Queensland, Australia, is subject to periodic outbreaks of dengue. A large outbreak of dengue 2 in 1996-97 affected five islands, resulting in 200 confirmed cases. On most of the affected islands, rainwater tanks were a common breeding site for vector mosquitoes. Rainwater tanks, wells and household containers filled with water are the most common breeding sites for dengue mosquitoes (Aedes aegypti), the primary vector of dengue in Queensland. We report on surveys conducted in February 2002 to measure the productivity of rainwater tanks and wells on Yorke Is. (Torres Strait), the first time the productivity of rainwater tanks has been measured in Australia. Of 60 rainwater tanks sampled, 10 had broken screens. Using a sticky emergence trap, 179 adult mosquitoes were collected, consisting of 63 Aedes scutellaris and 116 Culex quinquefasciatus. One unscreened tank produced 177 (99%) of the adults. A plankton net was used to sample 16 wells; 12 positive wells yielded 111 immature (larvae and pupae) mosquitoes, consisting of 57% and 43% Ae. scutellaris and Cx. quinquefasciatus, respectively. The apparent displacement of Ae. aegypti by Ae. scutellaris is discussed. Measures to reduce the likelihood of future dengue outbreaks are recommended.

Spatial distribution of vectors of Ross River virus and Barmah Forest virus on Russell Island, Moreton Bay, Queensland

We used a network of 20 carbon dioxide- and octenol-supplemented light traps to sample adult mosquitoes throughout Russell Island in southern Moreton Bay, south-east Queensland. Between February and April 2001, an estimated 1365 564 adult female mosquitoes were collected. In contrast to an average catch of 9754 female mosquitoes per trap night on Russell Island, reference traps set on Macleay Island and on the mainland returned average catches of 3172 and 222, respectively. On Russell Island, Ochlerotatus vigilax (Skuse), Coquillettidia linealis (Skuse), Culex annulirostris Skuse and Verrallina funerea (Theobald), known or suspected vectors of Ross River (RR) and/or Barmah Forest (BF) viruses, comprised 89.6% of the 25 taxa collected. When the spatial distributions of the above species were mapped and analysed using local spatial statistics, all were found to be present in highest numbers towards the southern end of the island during most of the 7 weeks. This indicated the presence of more suitable adult harbourage sites and/or suboptimal larval control efficacy. As immature stages and the breeding habitat of Cq. linealis are as yet undescribed, this species in particular presents a considerable impediment to proposed development scenarios. The method presented here of mapping the numbers of mosquitoes throughout a local government area allows specific areas that have high vector numbers to be defined.

Morphological shifts in island-dwelling birds: The roles of generalist foraging and niche expansion

Passerine birds living on islands are usually larger than their mainland counterparts, in terms of both body size and bill size. One explanation for this island rule is that shifts in morphology are an adaptation to facilitate ecological niche expansion. In insular passerines, for instance, increased bill size may facilitate generalist foraging because it allows access to a broader range of feeding niches. Here we use morphologically and ecologically divergent races of white-eyes (Zosteropidae) to test three predictions of this explanation: (1) island populations show a wider feeding niche than mainland populations; (2) island-dwelling populations are made up of individual generalists; and (3) within insular populations there is a positive association between size and degree of foraging generalism. Our results provide only partial support for the traditional explanation. In agreement with the core prediction, island populations of white-eye do consistently display a wider feeding niche than comparative mainland populations. However, observations of individually marked birds reveal that island-dwelling individuals are actually more specialized than expected by chance. Additionally, neither large body size nor large bill size are associated with generalist foraging behavior per se. These latter results remained consistent whether we base our tests on natural foraging behavior or on observations at an experimental tree, and whether we use data from single or multiple cohorts. Taken together, our results suggest that generalist foraging and niche expansion are not the full explanation for morphological shifts in island-dwelling white-eyes. Hence, we review briefly five alternative explanations for morphological divergence in insular populations: environmental determination of morphology, reduced predation pressure, physiological optimization, limited dispersal, and intraspecific dominance.