Island Taxa Research Articles

Fission and fusion in island taxa--serendipity, or something to be expected?

A well-used metaphor for oceanic islands is that they act as 'natural laboratories' for the study of evolution. But how can islands or archipelagos be considered analogues of laboratories for understanding the evolutionary process itself? It is not necessarily the case that just because two or more related species occur on an island or archipelago, somehow, this can help us understand more about their evolutionary history. But in some cases, it can. In this issue of Molecular Ecology, Garrick etal. () use population-level sampling within closely related taxa of Galapagos giant tortoises to reveal a complex demographic history of the species Chelonoidis becki - a species endemic to Isabela Island, and geographically restricted to Wolf Volcano. Using microsatellite genotyping and mitochondrial DNA sequencing, they provide a strong case for C.becki being derived from C.darwini from the neighbouring island of Santiago. But the interest here is that colonization did not happen only once. Garrick etal. () reveal C.becki to be the product of a double colonization event, and their data reveal these two founding lineages to be now fusing back into one. Their results are compelling and add to a limited literature describing the evolutionary consequences of double colonization events. Here, we look at the broader implications of the findings of Garrick etal. () and suggest genomic admixture among multiple founding populations may be a characteristic feature within insular taxa.

Relatedness defies biogeography: the tale of two island endemics (Acacia heterophylla and A.koa).

Despite the normally strong link between geographic proximity and relatedness of recently diverged taxa, truly puzzling biogeographic anomalies to this expectation exist in nature. Using a dated phylogeny, population genetic structure and estimates of ecological niche overlap, we tested the hypothesis that two geographically very disjunct, but morphologically very similar, island endemics (Acacia heterophylla from Réunion Island and A.koa from the Hawaiian archipelago) are the result of dispersal between these two island groups, rather than independent colonization events from Australia followed by convergent evolution. Our genetic results indicated that A.heterophylla renders A.koa paraphyletic and that the former colonized the Mascarene archipelago directly from the Hawaiian Islands ≤1.4 million yr ago. This colonization sequence was corroborated by similar ecological niches between the two island taxa, but not between A.melanoxylon from Australia (a sister, and presumed ancestral, taxon to A.koa and A.heterophylla) and Hawaiian A.koa. It is widely accepted that the long-distance dispersal of plants occurs more frequently than previously thought. Here, however, we document one of the most exceptional examples of such dispersal. Despite c. 18000km separating A.heterophylla and A.koa, these two island endemics from two different oceans probably represent a single taxon as a result of recent extreme long-distance dispersal.

Isolation and characterisation of 36 polymorphic microsatellite markers using 454 sequencing in the bar-shouldered skink, Ctenotus inornatus

We report on the development of 36 novel polymorphic microsatellite markers from the bar-shouldered skink, Ctenotus inornatus. Members in this genus account for up to 20 % of the diverse Australian lizard species. Microsatellite markers were developed to investigate island endemism amongst Kimberley islands taxa. We describe the diversity from 110 adult Ctenotus individuals. Overall, the markers produced between 9 to 40 alleles per locus and observed and expected heterozygosities of 74.6 and 95.7 %, respectively. Due to island endemism, habitat modification by introduced grazing mammals, some urban encroachment and changes in fire regime there has been fragmentation of its range. These microsatellite markers are an important tool for evaluating population genetic information and for prioritising populations for conservation management.

Genetic divergence and population demography of the Hainan endemic Black-throated Laughingthrush (Aves: Timaliidae, Garrulax chinensis monachus) and adjacent mainland subspecies

Geographic variation in the Black-throated Laughingthrush (Garrulax chinensis) is examined to infer the influence of Pleistocene glacial oscillations on the genetic diversity of its subspecies. Mitochondrial evidence suggests that the endemic Hainan Island taxon, G. c. monachus, is monophyletic, whereas its closest continental relatives, G. c. chinensis and G. c. lochmius, are not. Multilocus coalescent analysis based on two mitochondrial and two nuclear intron loci indicates inter-subspecific genetic differentiation during the Pleistocene and substantial post-divergence genetic introgression from G. c. chinensis into G. c. lochmius. In contrast, G. c. monachus experienced no post-divergence gene flow despite occasional land-bridge contact with its continental relatives, suggesting its isolation may have been imposed by ecology as well as geography. It is probably reproductively isolated and should be treated as a distinct species.

Update: The way back journey: islands as sources of biodiversity

news and update ISSN 1948‐6596 update The way back journey: islands as sources of biodiversity Until very recently, biogeographers and ecologists considered continents as the main source of biodi‐ versity for islands. This notion of islands as the end of the colonization journey was held mainly for two reasons (Bellemain and Ricklefs 2008). First, species colonizing islands from the mainland may lose dispersal ability making the process of reverse colonization less likely. Second, continen‐ tal populations evolve under intense interspecific competition and a high diversity of predators and pathogens, whereas island taxa usually evolve in a low‐competition environment and in the absence of such natural enemies; this makes mainland habitats more difficult to invade by island popula‐ tions. However, Bellemain and Ricklefs (2008) sug‐ gested that the way back journey to the continent should happen more often than previously thought, and this may be crucial for the mainte‐ nance of biodiversity on continents. A recent study by Hutsemekers et al. (2011), based on population genetic analysis of the spore‐producing moss Platyhypnidium ri‐ parioides from North Atlantic archipelagos, pro‐ vided strong evidence that (i) this bryophyte had not lost dispersal ability in island populations; (ii) the migration rates from continent to islands and vice versa were statistically similar; and (iii) conti‐ nental, instead of island populations, experienced a severe bottleneck during the last glacial maxi‐ mum. According to their analyses, the sea is not a major barrier for migration by island mosses. They did find a geographical pattern in genetic diversity in P. riparioides within the archipelagos of the Azores, Canary Islands, and Madeira, but it was not different from the isolation by distance pat‐ tern found for the Iberian Peninsula and Morocco. Moreover, although present air currents have fa‐ vored island colonization, the emergence of sea‐ mounts in the region may have acted as stepping stones between the archipelagos and the conti‐ nent. The major implications of their findings go beyond the biogeography of spore‐producing plants. Although bryophytes can be regarded as among the best candidates to show reverse colo‐ nization—due to their high dispersal ability and widespread distributions—these results alto‐ gether suggest that islands have the potential to act as refugia. Population size on islands can re‐ main constant in periods of intense disturbance on the continent, and such refugial biodiversity can be the source for recolonization of mainland areas. This link was made by Hutsemekers et al. (2011) by showing that, opposed to what hap‐ pened in the archipelagos, there was a decrease of suitable areas in the Iberian Peninsula during the last glacial maximum, and that island‐ continent air currents might have predominated during the arid phases of the last glaciation. The challenge now is to test for similar patterns for other groups—especially those with active disper‐ sal such as birds, bats and insects—and other ar‐ chipelagos with varying distances to the continent to test the generality of these findings. Testing the ‘way back journey’ and other emerging hypothe‐ ses in oceanic island biogeography has the poten‐ tial not only to improve our understanding about the factors that affect diversity across insular com‐ munities, but also to help the development of a comprehensive new model of biogeography (Heaney 2007). Tadeu Siqueira UNESP – Universidade Estadual Paulista, Departamento de Ecologia, Rio Claro, SP, Brazil. tsiqueira@rc.unesp.br References Bellemain, E. & Ricklefs, R. (2008) Are islands the end of the colonization road? Trends in Ecology and Evolution, 23, 461–468. Heaney, L.R. (2007) Is a new paradigm emerging for oceanic island biogeography? Journal of Bio‐ geography, 34, 753–757. Hutsemekers, V., Szovenyi, P., Shaw, A.J., Gonzalez‐ Mancebo, J.‐M., Munoz, J. & Vanderpoorten, A. (2011) Oceanic islands are not sinks of biodiver‐ sity in spore‐producing plants. Proceedings of the National Academy of Sciences USA, 108, Edited by Marcus Cianciaruso frontiers of biogeography 4.2, 2012 — © 2012 the authors; journal compilation © 2012 The International Biogeography Society

Function-Specific Accelerations in Rates of Sequence Evolution Suggest Predictable Epistatic Responses to Reduced Effective Population Size

Changes in effective population size impinge on patterns of molecular evolution. Notably, slightly deleterious mutations are more likely to drift to fixation in smaller populations, which should typically also lead to an overall acceleration in the rates of evolution. This prediction has been validated empirically for several endosymbiont and island taxa. Here, we first show that rate accelerations are also evident in bacterial pathogens whose recent shifts in virulence make them prime candidates for reduced effective population size: Bacillus anthracis, Bordetella parapertussis, Mycobacterium leprae, Salmonella enterica typhi, Shigella spp., and Yersinia pestis. Using closely related genomes to analyze substitution rate dynamics across six phylogenetically independent bacterial clades, we demonstrate that relative rates of coding sequence evolution are biased according to gene functional category. Notably, genes that buffer against slightly deleterious mutations, such as chaperones, experience stronger rate accelerations than other functional classes at both nonsynonymous and synonymous sites. Although theory predicts altered evolutionary dynamics for buffer loci in the face of accumulating deleterious mutations, to observe even stronger rate accelerations is surprising. We suggest that buffer loci experience elevated substitution rates because the accumulation of deleterious mutations in the remainder of the genome favors compensatory substitutions in trans. Critically, the hyper-acceleration is evident across phylogenetically independent clades, supporting the hypothesis that reductions in effective population size predictably induce epistatic responses in genes that buffer against slightly deleterious mutations.

Multiple lines of evidence support the recognition of a very rare bird species: the Príncipe thrush

The Gulf of Guinea thrush Turdus olivaceofuscus is endemic to the islands of Sao Tome´ (nominate olivaceofuscus) and Pr ´ incipe (subspecies xanthorhynchus). Rela- tionships between the two island taxa, originally described as two different species, are uncertain. This problem has been difficult to resolve due to the scarcity of information from Pr ´ incipe birds. A focused effort to find birds from Pr ´ incipe resulted in new observations, the first records of its song, and in the capture of four individuals, which provided new data for analyses. We obtained additional data from museum specimens. Our analyses indicate that the two populations differ substantially in size, bill shape and bill, eye and leg coloration as well as in several plumage characteristics. In addition, xanthorhynchus utters a low call of a type not previously recorded in the genus Turdus. Genetic evidence corroborates the phenotypic evidence: both taxa constitute clearly independent evolutionary lineages (2368 bp from the mitochondrial markers ND2, ND3 and cytochrome b (cyt-b) from four individuals of each population). Genetic divergence between the taxa (cyt-b: uncorrected: 6.4%; corrected: 8.8%) suggests that they may have been isolated for over 4 Myr. These results support the split of T. olivaceofuscus into two species: Sao Tomethrush T. olivaceofuscus and Pr ´ incipe thrush Turdus xanthor- hynchus. The latter is a very rare species, restricted to the most inaccessible parts of Pr ´ incipe Island. Phylogenetic inference favoured the African thrush Turdus pelios as the closest living relative to the Gulf of Guinea species.

High level of endemism in Haiti's last remaining forests: a revision of Modisimus (Araneae: Pholcidae) on Hispaniola, using morphology and molecules

This study describes the remarkable radiation of Modisimus on Hispaniola. During two short trips to the island, more species have been collected than are known from any comparable area on the mainland. We redescribe three of the four previously known Hispaniolan species, and describe 22 new species. Most Haitian species are local endemics, either of the severely threatened forests in one of the two national parks (La Visite National Park and Macaya Biosphere Reserve) or of their surrounding areas. Phylogenetic analysis indicates that most of these species together represent a species group that is restricted to the paleogeographically distinct southern ‘paleoisland’, and that is otherwise known neither from Hispaniola nor from any other island. Two mitochondrial markers, 16S and cytochrome oxidase I (COI), were sequenced in 21 species to test for their performance as barcoding genes within this group of partly closely related species. Both markers unambiguously corroborated the morphospecies, with small but distinct gaps between the intra- and interspecific genetic distances. The absence of Modisimus in South America argues against colonization of the West Indies over a ‘landspan’ connecting South America to the Greater Antilles. Overwater dispersal is supported by two lines of evidence (unusual radiation and reduced higher-level diversity), but further data (especially time estimates for the separation of mainland and island taxa) are needed to evaluate the third major model, continent–island vicariance as a result of plate tectonics. The species diversity of the genus, combined with the presence of habitat specialists, suggests that this system may have the potential to complement the classic studies on adaptive radiation in Caribbean Anolis lizards.

Genetic structure of Gymnures (genus Hylomys; Erinaceidae) on continental islands of Southeast Asia: historical effects of fragmentation

Eustatic sea level changes during Pleistocene climatic fluctuations produced several cycles of connection-isolation among continental islands of the Sunda shelf. To explore the potential effects of these fluctuations, we reconstructed a model of the vicariant events that separated these islands, based on bathymetric information. Among many possible scenarios, two opposite phylogenetic patterns of evolution were predicted for terrestrial organisms living in this region: one is based on the classical allopatric speciation mode of evolution, while the other is the outcome of a sequential dispersal colonization of the archipelago. We tested the applicability of these predictions with an analysis of sequence variation of the cytochrome b gene from several taxa of Hylomys. They were sampled throughout SE-Asia and the Sunda islands. High levels of haplotype differentiation characterize the different island taxa. Such levels of differentiation support the existence of several allopatric species, as was suggested by previous allozyme and morphological data. Also in accordance with previous results, the occurrence of two sympatric species from Sumatra is suggested by their strongly divergent haplotypes. One species, Hylomys suillus maxi, is found both on Sumatra and in Peninsular Malaysia, while the other, H. parvus, is endemic to Sumatra. Its closest relative is H. suillus dorsalis from Borneo. Phylogenetic reconstructions also demonstrate the existence of a Sundaic clade composed of all island taxa, as opposed to those from the continent. Although there is no statistical support for either proposed biogeographic model of evolution, we argue that the sequential dispersal scenario is more appropriate to describe the genetic variation found among the Hylomys taxa. However, despite strong differentiation among island haplotypes, the cladistic relationships between some island taxa could not be resolved. We argue that this is evidence of a rapid radiation, suggesting that the separation of the islands may have been perceived as a simultaneous event rather than as a succession of vicariant events. Furthermore, the estimates of divergence times between the haplotypes of these taxa suggest that this radiation may actually have predated the climatic fluctuations of the Pleistocene. Further refinement of the initial palaeogeographic models of evolution are therefore needed to account for these results.

Effects of fragmentation on genetic diversity in island populations of the Aegean wall lizard Podarcis erhardii (Lacertidae, Reptilia)

Landbridge islands offer unique opportunities for understanding the effects of fragmentation history on genetic variation in island taxa. The formation of islands by rising sea levels can be likened to a population bottleneck whose magnitude and duration is determined by island area and time since isolation, respectively. The Holocene landbridge islands of the Aegean Sea (Greece) were formed since the last glacial maximum and constitute an ideal system for disentangling the effects of island area, age and geographic isolation on genetic variability. Of the many reptile species inhabiting this island system, the Aegean wall lizard Podarcis erhardii is an excellent indicator of fragmentation history due to its widespread distribution and poor over-water dispersal abilities. In this study, we utilize a detailed record of Holocene fragmentation to investigate the effects of island history on wall lizard mitochondrial and nuclear microsatellite diversity. Findings show that the spatial distribution of mitochondrial haplotypes reflects historical patterns of fragmentation rather than geographic proximity per se. In keeping with neutral bottleneck theory, larger and younger islands retain more nuclear genetic variation than smaller, older islands. Conversely, there is no evidence of an effect of isolation by distance or effect of distance to the nearest larger landmass on genetic variability, indicating little gene flow between islands. Lastly, population-specific measures of genetic differentiation are inversely correlated with island area, suggesting that smaller islands exhibit greater divergence due to their greater susceptibility to drift. Taken together, these results suggest that both island area and time since isolation are important predictors of genetic variation and that these patterns likely arose through the progressive fragmentation of ancestral diversity and the ensuing cumulative effects of drift.

Immunological change in a parasite-impoverished environment: divergent signals from four island taxa.

Dramatic declines of native Hawaiian avifauna due to the human-mediated emergence of avian malaria and pox prompted an examination of whether island taxa share a common altered immunological signature, potentially driven by reduced genetic diversity and reduced exposure to parasites. We tested this hypothesis by characterizing parasite prevalence, genetic diversity and three measures of immune response in two recently-introduced species (Neochmia temporalis and Zosterops lateralis) and two island endemics (Acrocephalus aequinoctialis and A. rimitarae) and then comparing the results to those observed in closely-related mainland counterparts. The prevalence of blood parasites was significantly lower in 3 of 4 island taxa, due in part to the absence of certain parasite lineages represented in mainland populations. Indices of genetic diversity were unchanged in the island population of N. temporalis; however, allelic richness was significantly lower in the island population of Z. lateralis while both allelic richness and heterozygosity were significantly reduced in the two island-endemic species examined. Although parasite prevalence and genetic diversity generally conformed to expectations for an island system, we did not find evidence for a pattern of uniformly altered immune responses in island taxa, even amongst endemic taxa with the longest residence times. The island population of Z. lateralis exhibited a significantly reduced inflammatory cell-mediated response while levels of natural antibodies remained unchanged for this and the other recently introduced island taxon. In contrast, the island endemic A. rimitarae exhibited a significantly increased inflammatory response as well as higher levels of natural antibodies and complement. These measures were unchanged or lower in A. aequinoctialis. We suggest that small differences in the pathogenic landscape and the stochastic history of mutation and genetic drift are likely to be important in shaping the unique immunological profiles of small isolated populations. Consequently, predicting the impact of introduced disease on the many other endemic faunas of the remote Pacific will remain a challenge.

Spurious or Island Effect? A Response to J. A. Pérez-Claros and J. C. Aledo's Comment on “Morphological Evolution Is Accelerated among Island Mammals”

In their comment [1], Perez-Claros and Aledo claimed that the main result of accelerated evolution in island mammals, compared with their mainland relatives, is not well supported by the data and analyses presented in [2]. They raise two points: the first refers to a long-standing methodological debate regarding the study of evolutionary rates and the second refers to the quality of the dataset in [2]. Haldane [3] first proposed the unit darwin to calculate rates of morphological evolution in fossil taxa. Since then, there has been much controversy on the relevance of the darwin as a measure of evolutionary rates [4]. First, evolutionary rates in darwins that are calculated over the largest time intervals are necessarily lowered, because they average periods of rapid change with periods of slow change or stasis, and they can also include fluctuations in the direction of change [4]. Second, because evolutionary rates are dependent on the time interval over which they are measured, rates measured over different time intervals cannot be compared without taking into account the time interval over which they were calculated (i.e., temporal scaling), which is often done by plotting rates against time intervals on a log-log graph. This is equivalent to plotting a ratio (rate) against its denominator (time interval), which produces a negative correlation and may be a mathematical artifact that has been dubbed “the spurious effect” [5,6]. Despite these two important caveats, rates in darwins are still useful to compare similar or different lineages evolving at similar or different times and places [7]. More importantly, these concerns simply do not affect the results presented in [2], because the conclusions were solely based on the comparison of the elevation of the two regression lines. The extent to which the “spurious effect” influences the slopes of the regression is not of direct relevance to the question of whether mammals evolve faster on islands [2]. In fact, there is no reason to believe that such a bias will introduce a systematic difference among the mainland and island groups compared in [2]. Given this, it is unlikely that the “spurious effect” can be evoked to explain the differences in the island–mainland comparison. Another more-specific point raised by Perez-Claros and Aledo concerns the data that was assembled to test the theory and upon which the conclusions were based in [2]. Perez-Claros and Aledo indicate that the analysis is no longer significant when re-performed on a subset of the data. This is true, but it is easy to reduce the range of data to a point where the relation is no longer significant. Is it relevant to test a theory on a subset of data that represents less than half of the data and only 16% on a log scale (or 0.15% on a natural scale) of the original range of time intervals? I contend that their analysis reduces the dataset to such an extent that it is no longer meaningful to address the evolutionary question at hand. The data made available in [2] represent, to date, the largest dataset ever assembled on morphological rates of evolution in mammal species, fossil and recent. Yet, the data are unbalanced, with an over-representation of island taxa for the smallest time intervals, and an over-representation of mainland data for the largest time intervals. This issue was already addressed [2, page 0002], and readers are referred to the original paper for more details. In the future, as more data become available, the conclusion in [2] may be either validated or challenged, but for the time being, the difference in elevation between the two regression lines is statistically significant and is the most robust for time intervals below 20,000 y. Morphological evolution is faster in island mammals over these time intervals, when compared with that of mammals evolving on the mainland.

Digestive performance in five Mediterranean lizard species: effects of temperature and insularity

Temperature sensitivity of digestive processes has important ramifications for digestive performance in ectothermic vertebrates. We conducted a comparative analysis of temperature effects on digestive processes [gut passage times (GPTs) and apparent digestive efficiencies (ADEs)] in five lacertid lizards occurring in insular (Podarcis erhardii, P. gaigeae), and mainland (P. muralis, P. peloponnesiaca, Lacerta graeca) Mediterranean environments. GPTs were negatively correlated to temperature with mainland taxa having 10-20% longer GPTs than island taxa. In contrast to previous studies that estimate ADEs using bomb calorimetry, we compare ADEs by analyzing discrete efficiencies for lipids, sugars and proteins at three temperature regimes (20, 25, and 30 degrees C); each of these categories produces different results. ADEs for lipids and sugars showed a monotonic increase with temperature whereas ADEs for proteins decreased with temperature. Island taxa had consistently higher ADEs than their mainland counterparts for lipids and for proteins but not for sugars. They are characterized by superior energy acquisition abilities despite significantly shorter GPTs. Their increased digestive performance relative to the mainland species appears to allow them to maximize energy acquisition in unproductive island environments where food availability is spatially and seasonally clustered.

Island Biogeography and Evolution: Genetic Divergence and Speciation of Island Taxa

Island Biogeography and Evolution: Genetic Divergence and Speciation of Island Taxa

Prehistoric decline of genetic diversity in the nene.

The nene (or Hawaiian goose, Branta sandvicensis) once occurred on most of the main Hawaiian Islands (1), but by Captain Cook’s arrival in 1778, nene were found only on the island of Hawaii (2). A decline that began in the 1800s reduced the nene population to fewer than 30 individuals by the middle of the 20th century (2). Nene currently have extremely low levels of genetic variation (3). We questioned whether this low genetic variation resulted from the recent population decline or was a natural consequence of living on islands (theory and empirical evidence indicate that island taxa should and do have lower genetic variability than mainland ones) (4). Here we report an assessment of genetic variation in samples of nene on the island of Hawaii from four time periods (Fig. 1): 26 extant captive and wild birds, 14 historical museum specimens (collected between 1833 and 1928), 16 bones from archaeological middens [radiocarbon dated at 160 to 500 radiocarbon years before present (rybp)], and 14 bones from paleontological sites (500 to 2540 rybp). We analyzed DNA sequence variation in the mitochondrial control region (CR), following very strict methodologies to avoid and detect contamination in ancient samples (5). We found no variation across 847 nucleotide sites among extant nene (haplotype diversity, H 5 0) and designate this sequence as haplotype RH. For the ancient samples, we obtained sequences of 217 sites from the highly variable left domain of the CR and 92 sites from the less variable right domain (6). Unexpectedly, only one museum specimen sequence differed from the RH haplotype (E1, Fig. 1B), and all archaeological bones (sampled from eight different caves) possessed RH. Only the paleontological nene exhibited levels of CR variation typical of geese (5): six individuals had RH and eight had one of six additional haplotypes (Fig. 1B). H was 0.802 (multinomial lower 95% CI 5 0.67) in the paleontological sample, but only 0.067 (upper 95% CI 5 0.26) in the archaeological and museum specimen samples combined (6). Thus, our results indicate that the nene populations on Hawaii lost most of their mitochondrial DNA (mtDNA) variability long before their historic population decline. Monte Carlo simulations run for 150 generations (about 600 years) suggest that the most likely explanation is a prehistoric population bottleneck (6). A reduction of H from 0.80 to 0.26 in populations of varying size (500 to 10,000) can only occur if the populations decline to fewer than 270 females (for a rate of decline of r 5 20.01) or to fewer than 20 females (for r 5 20.05). In addition, in the absence of population decline, an improbably large selection coefficient of 0.10 would be required to change RH frequency from 0.43 to 0.97 over 150 generations. Our radiocarbon chronology (Fig. 1A) suggests that the nene’s loss of genetic variability took place during a period of prehistoric human population growth (900 to 350 years ago), when settlements expanded into marginal ecological zones (7). Radiocarbon dates (1, 5, 8) indicate that the extirpation of the nene on Kauai and the extinction of at least five of the nine large ground-dwelling Hawaiian birds (1) occurred during this time period. Ecological changes associated with human settlement are assumed to have caused the extinctions (1) and apparently caused a dramatic reduction in genetic diversity in the nene on Hawaii as well. Ultimately, we must ask why the nene population on Hawaii could escape prehistoric extinction while many other Hawaiian birds did not. Cultural changes may have created better conditions for nene, such as more open habitat, while at the same time warfare may have created noman’s-lands safer for wildlife. Prohibitions by ruling elites (kapu) may have protected the birds, and it is possible that they were even brought under domestication or semidomestication. Paleontological studies have shown how broadly devastating the impact of prehistoric humans was on insular organisms, as most vividly shown by the total extinction of hundreds of species (1). Our findings demonstrate that these prehistoric influences may still be reflected in the genetic makeup of insular species that survived until the present, many of which, like the nene, are endangered. In addition, we have confirmed that at least one islanddwelling species, the nene, did not always have the low genetic variability predicted by its history as an island taxon (4).

Evolutionary exposition from plumage pattern in African Accipiter

Louette, M. 2000. Evolutionary exposition from plumage pattern in African Accipiter. Ostrich 71 (1 & 2): 45–50. Plumage characteristics were superficially taken into account by Wattel (1973) for his division of the genus Accipiter; Savalli (1995) formulated hypotheses to explain plumage colouration evolution in birds in general. I examine here variation of plumage coloration and pattern in the 14 African species of Accipiter, in order to evaluate their phylogenetic and/or functional values. I study isolated populations in this respect: — A.francesae: the derived Comoro Islands taxa are remarkably different from the Madagascar stock in the disappearance of adult sexual dimorphism and by the ‘reversion’ to an ancestral juvenal pattern. — A. tachiro: the derived Pemba Island taxon is more colourful in adult plumage than the Tanzanian savanna-dwelling stock. The Bioko Island taxon derived from Cameroonian forest stock and is only slightly different therefrom. Juvenal plumage is remarkably variable among central African forest races, supposedly because in sympatry with other Accipiter species, the juvenile needs to be recognised by conspecifics. From a general examination of the African species it appears that: — Adults can be dimorphic (cryptic females) or monomorphic (both sexes colourful or both sexes cryptic). Bright adult plumage serves sexual attraction: in dense environment better visibility of bright colour is on balance advantageous over crypsis. — Juvenal plumages are mostly highly cryptic; ventrally, the basal colour occurs in two phases within species and the pattern is variable among species: it can be streaked, barred or spotted. In most African Accipiter certain bright colours present in the adult are announced in the juvenile plumage. It is assumed that the cryptic juvenal plumage serves to minimise harassment by territorial adults, but in some species, the juvenile resembles the adult female, the reason for this mimicry is not yet established. Juvenal and adult plumages being subject to rapid evolutionary change, they seem to be of limited use in phylogeny.

Plumage polymorphism in Terpsiphone and the rule of island drabness

Plompen, W. 2000. Plumage polymorphism in Terpsiphone and the rule of island drabness. Ostrich 71 (1 & 2): 316. Many related bird species differ through their conspicuous plumage coloration characteristics. On islands, birds often have a drabber plumage coloration than their mainland counterpart. This rule is regarded as the main evidence for the species recognition hypothesis, because on islands mostly only one species per genus is present. In the absence of congeners there may be no benefit from a species specific badge, with drabness as a result. However drabness as such is not predicted by this species recognition hypothesis. In fact the only selective pressure caused by a species recognition mechanism, works in sympatry. Therefore on an island with no related species present, the elaborate coloration that originated in the mainland situation, is allowed to evolve in any sense, or may even not evolve at all. Taking this all together, if under the. species recognition hypothesis island taxa may evolve at random with respect to colouration, and island drabness is a well known phenomenon, then an additional mechanism inherent to the island situation is needed, that causes the degradation of any bright plumage colouration. As a consequence, island drabness in itself does not provide any information at all on the original mechanism that caused plumage elaboration on the mainland.

Systematic affinities of island and mainland populations of the Dunnart Sminthopsis griseoventer in Western Australia: data from allozymes and mitochondrial DNA

The systematic affinities of Boullanger Island and Western Australian mainland populations of the Grey-bellied Dunnart Sminthopsis griseoventer were investigated using allozyme electrophoresis and phylogenetic analysis of a 404 bp region of the mitochondrial DNA (mtDNA) control region. Forty-six allozyme loci were screened for variation and found to be monomorphic in S. griseoventer from both Boullanger Island and one mainland population. Low levels of variation were also detected in the control region sequence, with just one haplotype observed among eight island individuals and three haplotypes among 10 mainland individuals, each differing at between two and four nucleotide sites (0.5?1.0% divergence). Phylogenetic analyses using maximum parsimony of control region sequence from mainland and island taxa, and four species of the "murina complex", S. aitkeni, S. murina, S. gilberti and S. dolichura, indicated that the island and mainland taxa formed a monophyletic group to the exclusion of the other "murina complex" species, but were paraphyletic at the level of the individual haplotypes. These results are consistent with the hypothesis that mainland and island populations of S. griseoventer comprise a single species, and suggest that there has been no long-term barrier to gene flow between these populations. Analyses of molecular variation provided evidence the island population represents a separate management unit for conservation, but are insufficient to determine whether there has been inbreeding or a recent bottleneck in the island population.

Mitochondrial DNA phylogeny of Brimstone butterflies (genusGonepteryx) from the Canary Islands and Madeira

Part of the mitochondrial Cytochrome Oxidase I gene was sequenced for seven species ofGonepteryx(Pieridae) butterflies. Four of the species are island endemics inhabiting the Canary Island archipelago and Madeira. The remaining three are European and African conspecifics. Sequence data were analysed phylogenetically by maximum parsimony and maximum likelihood methods. The resulting trees were used to deduce Canarian species» ancestry, sequential inter-island colonization and systematics. They suggest African ancestry for the Canary Island taxa and a colonization pattern, within the archipelago, compatible with the geological ages of the islands and other Canarian fauna: a colonization sequence from Africa to Tenerife and Gomera, followed by Tenerife to La Palma. The molecular phylogeny indicated that there are three Canarian endemics,G. cleobule,G. palmaeandG. eversifrom Tenerife, La Palma and Gomera, respectively.

HISTORICAL BIOGEOGRAPHY OF WEST INDIAN VERTEBRATES

▪ Abstract The vertebrate fauna of the West Indies (1262 species) exhibits high levels of endemism and has a taxonomic composition characteristic of more isolated oceanic islands. Many groups that are widespread on the mainland are absent in the islands, and some of those present are characterized by large adaptive radiations. The growing fossil record of West Indian vertebrates, including mid-Tertiary amber fossils (considered here to be 20–30 million years old), indicates that this pattern of reduced higher-taxon diversity has persisted for a long period of time. Phylogenetic relationships of nonvolant groups display a strong South American influence, whereas volant groups (birds and bats) and freshwater fish show closer ties with Central and North America. Molecular estimates of divergence times between island taxa and their mainland counterparts indicate a Cenozoic origin (within the last 65 million years) for nearly all groups examined. Together, data from different sources point to an origin by overwater dispersal for a large majority of the vertebrate fauna. The prevailing current direction, from southeast to northwest, and the wide scattering of estimated times of origin suggest that much of the nonvolant fauna arrived by flotsam carried from the mouths of major rivers in northeastern South America. Spatial relationships, especially considering low sea levels during the Pleistocene, appear to better explain the routes of colonization taken by the volant fauna and freshwater fish. Caribbean geologic history does not preclude an origin by late Mesozoic vicariance for several possibly ancient groups, although an early Cenozoic arrival by dispersal also cannot be discounted. An integrative approach to historical biogeography is shown to be more insightful than the current trend in the field, cladistic biogeography, which places prime emphasis only on phylogenetic relationships.