Tropical fruitflies (Diptera: Tephritidae) of the Krakatau Archipelago in 1990 and comments on faunistic changes since 1982

Three of the Krakatau islands, in Sunda Strait, some 40 km from both Java and Sumatra, are believed to have been totally devastated by the famous cataclysmic eruption of 1883. The fourth, Anak Krakatau, is an emergent volcanic island which rose from Krakatau's submerged 1883 caldera in 1930, suffered a self-devastating eruption in 1952/3 and several severely damaging ones since then. In 1990 the tephritid fauna was monitored on all the islands with Steiner traps. Nine species were found, five of which appeared to have been found by Yukawa in 1982 (Yukawa 1984) using similar methods and lures, when he noted a total of six species. As in 1982, the fauna in 1990 was characterized by the numerical dominance ofBactrocera albistrigata (de Meijere) although this appeared to be less marked than in 1982 andBactrocera papayae Drew & Hancock appeared to have increased in relative numbers. The distribution of three species over the islands of the archipelago had increased and four species not found in 1982 were present. Rakata, Krakatau's remnant and by far the largest and highest island, carried seven species (six in 1982), Sertung three (two in 1982), Panjang four (one in 1982) and Anak Krakatau four (one in 1982). Capture rates were lower than in 1982 but still higher than those obtained on the Javan mainland in 1982. There was a marked difference between the tephritid faunas of Anak Krakatau's two forelands, which were at different stages of biotic succession.     

Historical arthropod diversity patterns direct rehabilitation targets for Robben Island,South Africa,a continental island in a biodiversity hotspot

Island species are susceptible to extinction through disturbances such as habitat transformation. Due to the small size and isolation of islands, species have limited options for refuges and recolonization, making their rehabilitation a conservation priority. Robben Island is a continental island, isolated from the mainland ca. 15 000 years ago, and has been degraded by humans and alien species for nearly 400 years. Mainland areas with similar vegetation should be good reference sites for the biological restoration of the island due to historical connectedness. However, very little information exists as to which species were lost. Here we aim to identify the best mainland sites to use as reference sites for Robben Island based on remaining arthropod diversity on the island. Sites found to be most similar in terms of arthropod diversity to Robben Island were sites north of Robben Island (Elandsbaai and Dwarskersbos) rather than the geographically closest locations. These sites therefore represent ideal reference sites for biological restoration of the island. We do not suggest the reintroduction of species from these localities, but rather Robben Island should be restored to match their vegetation height and cover.     

The recovery of coral genetic diversity in the Sunda Strait following the 1883 eruption of Krakatau

Surveys of microsatellite variation show that genetic diversity has largely recovered in two reef-building corals, Pocillopora damicornis and Seriatopora hystrix (Scleractinia: Pocilloporidae), on reefs which were decimated by the eruption of the volcano Krakatau in 1883. Assignment methods and gene flow estimates indicate that the recolonization of Krakatau occurred mainly from the closest upstream reef system, Pulau Seribu, but that larval input from other regions has also occurred. This pattern is clearer in S. hystrix, which is traditionally the more dispersal-limited species. Despite these observed patterns of larval dispersal, self-recruitment appears to now be the most important factor in supplying larvae to coral populations in Krakatau. This suggests that the colonization of devastated reefs can occur quickly through larval dispersal; however, their survival requires local sources of larvae for self-recruitment. This research supports the observation that the recovery of genetic diversity in coral reef animals can occur on the order of decades and centuries rather than millennia. Conservation measures aimed at sustaining coral reef populations in Krakatau and elsewhere should include both the protection of upstream source populations for larval replenishment should disaster occur as well as the protection of large adult colonies to serve as local larval sources.     

Pollinating fig wasps: genetic consequences of island recolonization

The levels of genetic diversity and gene flow may influence the long-term persistence of populations. Using microsatellite markers, we investigated genetic diversity and genetic differentiation in island (Krakatau archipelago, Indonesia) and mainland (Java and Sumatra, Indonesia) populations of Liporrhopalum tentacularis and Ceratosolen bisulcatus, the fig wasp pollinators of two dioecious Ficus (fig tree) species. Genetic diversity in Krakatau archipelago populations was similar to that found on the mainland. Population differentiation between mainland coastal sites and the Krakatau islands was weak in both wasp species, indicating that the intervening 40 km across open sea may not be a barrier for wasp gene flow (dispersal) and colonization of the islands. Surprisingly, mainland populations of the fig waSPS may be more genetically isolated than the islands, as gene flow between populations on the Javan mainland differed between the two wasp species. Contrasting growth forms and relative 'immunity' to the effects of deforestation in their host fig trees may account for these differences.     

How important were stepping stones in the colonization of Krakatau?

In theory, one factor determining the rate and nature of the assembly of island biotas is the presence or absence of stepping stone islands, yet no field studies have demonstrated stepping stone function in practice. Krakatau, in Sunda Strait, is about equidistant from Java and Sumatra. Sebesi lies about half way between Krakatau and Sumatra, but no island intervenes between Krakatau and the nearest coast of Java. We assess the evidence that Sebesi has acted as an important stepping stone for Krakatau's recolonization since the devastating 1883 volcanic eruption. About a quarter of Krakatau's resident land birds, two-fifths of its reptiles, bats and land molluscs, and about two-thirds of its termites, pteridophytes, butterflies and spermatophytes are unknown on Sebesi, evidently having colonized without stepping stone involvement. Identifiable Sumatran taxa do not outnumber identifiable Javan ones on Krakatau, nor do historical distribution records indicate movement from Sebesi to Krakatau in animal groups. Krakatau's biota is not a subset of Sebesi's in predominantly anemochorous or thallassochorous plant groups, butterflies, reptiles or bats, and is only marginally so in termites. It is a subset in predominantly zoochorous spermatophyte groups, except Ficus species, and in birds and land molluscs. Comparison with a weaker stepping stone candidate, Panaitan, provides no evidence for a stepping stone role for Sebesi in butterflies or termites. We discuss the dispersal and establishment constraints on colonization by the groups involved, and conclude that, overall, Sebesi had little impact as a stepping stone. Instead, it is more probable that divergence of the environments of the two islands has led to an increasingly independent recolonization of Krakatau.  © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 77 , 275–317.     

Population size and molecular evolution on islands

The nearly neutral theory predicts that the rate and pattern of molecular evolution will be influenced by effective population size (Ne), because in small populations more slightly deleterious mutations are expected to drift to fixation. This important prediction has not been widely empirically tested, largely because of the difficulty of comparing rates of molecular evolution in sufficient numbers of independent lineages which differ only in Ne. Island endemic species provide an ideal test of the effect of Ne on molecular evolution because species restricted to islands frequently have smaller Ne than closely related mainland species, and island endemics have arisen from mainland lineages many times in a wide range of taxa. We collated a dataset of 70 phylogenetically independent comparisons between island and mainland taxa, including vertebrates, invertebrates and plants, from 19 different island groups. The rate of molecular evolution in these lineages was estimated by maximum likelihood using two measures: overall substitution rate and the ratio of non-synonymous to synonymous substitution rates. We show that island lineages have significantly higher ratios of non-synonymous to synonymous substitution rates than mainland lineages, as predicted by the nearly neutral theory, although overall substitution rates do not differ significantly.     

The role of animals in the colonization of the Krakatau Islands by fig trees (Ficus species)

Abstract. Since the biologically extirpating eruption of Krakatau (Sunda Strait) in 1883, Rakata (Krakatau's remnant) and two closely adjacent islands, Sertung and Panjang, have been colonized by over 200 species of vascular plants. They now carry species-poor mixed tropical forest, including some twenty-three species of Ficus . Data on the sequence of colonization over the last century by twenty-four Ficus species, twenty-three species of volant frugivores, and by agaonid fig-wasps, presumably from the large islands of Java and Sumatra, each some 44 km distant, are summarized. The potential of the volant frugivores as dispersers of fig seeds is assessed, the pollination problems involved in the colonization of islands by figs are reviewed and patterns of colonization by fig species and by their bird and bat dispersers are identified and discussed.
In 1930 a new island, Anak Krakatau, emerged from Krakatau's submerged caldera. This active volcano suffered a self-sterilizing eruption in 1952/1953 and has been colonized, under considerable constraint from its own volcanic activity, probably largely from the (selected) species pool present on Rakata, Sertung and Panjang, 2–4 km away. Its vegetation is at an earlier successional stage (grassland and Casuarina woodland) than that of the three older islands, and in 1992 the Casuarina woodland was in an early stage of transition to mixed forest. The colonization of Anak Krakatau by Ficus species, agaonid wasps and volant frugivores over a critical decade (1982–92) is reviewed, including preliminary assessments of the effects of pollinator limitation on four pioneer fig species and indications of a possible effect of the presence of avian raptors, particularly the peregrine falcon, on fig colonization and forest diversification.     

Patterns of island treeline elevation – a global perspective

Treeline research has strongly focused on mountain systems on the mainland. However, island treelines offer the opportunity to contribute to the global framework on treeline elevation due to their island‐specific attributes such as isolation, small area, low species richness and relative youth. We hypothesize that, similar to the mainland, latitude‐driven temperature variation is the most important determinant of island treeline elevation on a global scale. To test this hypothesis, we compared mainland with island treeline elevations. Then we focused 1) on the global effects of latitude, 2) on the regional effects of island type (continental vs oceanic islands) and 3) the local effects of several specific island characteristics (age, area, maximum island elevation, isolation and plant species richness). We collected a global dataset of islands (n = 86) by applying a stratified design using GoogleEarth and the Global Island Database. For each island we extracted data on latitude and local characteristics. Treeline elevation decreased from the mainland through continental to oceanic islands. Island treeline elevation followed a hump‐shaped latitudinal distribution, which is fundamentally different from the mainland double‐hump. Higher maximum island elevation generated higher treeline elevation and was found the best single predictor of island treeline elevation, even better than latitude. Lower island treeline elevation may be the result of a low mass elevation effect (MEE) influencing island climates and an increasingly impoverished species pool but also trade wind inversion‐associated aridity. The maximum island elevation effect possibly results from an increasing mass elevation effect (MEE) with increasing island elevation but also range shifts during climatic fluctuations and the summit syndrome (i.e. high wind speeds and poor soils in peak regions). Investigating islands in treeline research has enabled disentangling the global effect of latitude from regional and local effects and, at least for islands, a comprehensive quantification of the MEE.     

Genetic and ecological differentiation in the endemic avifauna of Tiburón Island

Tiburón Island is a land‐bridge island in the Gulf of California, separated from mainland Sonora by 3 km. The shallow channel (13 m) separating the island and mainland is thought to have formed 10 000 years ago. Although the majority of avian resident species are not taxonomically differentiated, six species are represented by endemic subspecies (cactus wren, gila woodpecker, black‐tailed gnatcatcher, Gambel's quail, canyon towhee, northern cardinal), of which all but one (black‐tailed gnatcatcher) possess a pallid, ash‐gray coloration compared to those on the mainland. We compared mtDNA sequences of five of the endemic subspecies (we lacked samples of northern cardinal) and one more widespread subspecies (verdin) present on the island from sequences previously published for mainland populations. For most populations, we discovered no genetic differentiation between the island and the mainland, thus questioning the taxonomic validity of the endemic subspecies. The canyon towhee and the verdin showed significant mitochondrial DNA differentiation, although neither was reciprocally monophyletic. We modeled the ecological niche for the mainland populations of the study species (plus the curve‐billed thrasher, which was studied earlier) and determined if species’ occurrence on the island was predicted. We found no ecological differences for the four species that showed no genetic differences and one of the species that did (verdin). In contrast, some ecological differentiation was detected for the canyon towhee and the curve‐billed thrasher. We conclude that the ecological differences leading to paler plumages in Tiburón Island endemics are sufficiently subtle as to not be discovered in our ecological models, although they are likely influenced by variation in rainfall, temperature and the vegetation. In addition, the black‐tailed gnatcatcher is not paler, and therefore might respond to different ecological variables. We simulated sequence data and showed that if the populations on Tiburón Island have been isolated for 10 000 years, there ought to be greater differences than we observed for black‐tailed gnatcatcher, Gambel's quail, cactus wren, and gila woodpecker, suggesting that there has been gene flow connecting the mainland and island populations. If so, then the paler coloration of these Tiburón Island subspecies (excluding black‐tailed gnatcatcher) has been maintained by natural selection despite gene flow. In any case, the pale coloration apparently evolved within the past 10 000 years.     

Ant communities on small tropical islands: effects of island size and isolation are obscured by habitat disturbance and ‘tramp’ ant species

Aim Comparisons among islands offer an opportunity to study the effects of biotic and abiotic factors on small, replicated biological communities. Smaller population sizes on islands accelerate some ecological processes, which may decrease the time needed for perturbations to affect community composition. We surveyed ants on 18 small tropical islands to determine the effects of island size, isolation from the mainland, and habitat disturbance on ant community composition. Location Thousand Islands Archipelago (Indonesian name: Kepulauan Seribu) off Jakarta, West Java, Indonesia. Methods Ants were sampled from the soil surface, leaf litter and vegetation in all habitat types on each island. Island size, isolation from the mainland, and land‐use patterns were quantified using GIS software. The presence of settlements and of boat docks were used as indicators of anthropogenic disturbance. The richness of ant communities and non‐tramp ant species on each island were analysed in relation to the islands’ physical characteristics and indicators of human disturbance. Results Forty‐eight ant species from 5 subfamilies and 28 genera were recorded from the archipelago, and approximately 20% of the ant species were well‐known human‐commensal ‘tramp’ species. Islands with boat docks or human settlements had significantly more tramp species than did islands lacking these indicators of anthropogenic disturbance, and the diversity of non‐tramp species decreased with habitat disturbance. Main conclusions Human disturbance on islands in the Thousand Islands Archipelago promotes the introduction and/or establishment of tramp species. Tramp species affect the composition of insular ant communities, and expected biogeographical patterns of ant richness are masked. The island with the greatest estimated species richness and the greatest number of unique ant species, Rambut Island, is a forested bird sanctuary, highlighting the importance of protected areas in preserving the diversity of species‐rich invertebrate faunas.     

Stand Biomass and Tree Mortality from Permanent Forest Plots on Krakatau,Indonesia, 1989–19951

Forest closure on the three original Krakatau Islands (Panjang, Rakata, and Sertung) took place ca 1930, about 50 yr after the apparent sterilization of the islands due to volcanic eruptions. Two permanent forest plots were established on each of these islands in 1989. A full enumeration of these plots, of two additional Rakata plots, and of two “mainland”plots from the Ujung Kulon National Park, West Java, was undertaken in 1992. These data provide the first estimates of aboveground biomass from Krakatau. The values reported for Krakatau are below the local West Javan figures, with considerable variation occurring within the islands. In 1992, the fourth Krakatau island, Anak Krakatau, began an eruption sequence which continued through the study period, depositing ash on the study sites of Panjang and Sertung. A further partial survey of these plots in 1994–1995 revealed a significant increase in mortality since the volcanic activity recommenced, with an increase in deaths of larger stems. Although Rakata has not been influenced directly by volcanism, three sites surveyed on Rakata in 1994–1995 have experienced increased tree mortality, in two cases as a consequence of storm damage and in particular, of lightning strikes. Stand dynamics on Krakatau thus appear to be strongly influenced by episodic environmental disturbance with varying degrees of dependence on the volcanic activity of Anak Krakatau.     

Species delimitation and the origin of populations in island representatives of Phylica (Rhamnaceae)

Abstract Relationships between the closely related island species of Phylica (Rhamnaceae) and a mainland species, P. paniculata , were elucidated using amplified fragment length polymorphisms (AFLPs). Parsimony, neighbor joining, and principal coordinate (PCO) analyses indicated that each of the species studied is distinct. AFLPs were also useful in elucidating the genetic relationships and possible infraspecific origins of different island populations in the Atlantic and Indian Oceans. Phylica nitida on Réunion is likely to have been derived from P. nitida on Mauritius. Although the sampling on New Amsterdam is not extensive, the data are also consistent with the hypothesis that P. arborea on New Amsterdam was derived from a single colonization of P. arborea from Gough Island. Similarly, the Gough Island population appears to have been derived from a single colonization event, but it is so distinct from those on Tristan da Cunha, that there may have been two separate dispersals to Gough and Tristan/Nightingale from different lines of the mainland progenitor. There is also evidence of a recolonization from Gough to Tristan da Cunha. Thus, Phylica arborea is capable of repeated long distance dispersal, up to 8000 km, even though the fruits and seeds are not of a type normally associated with this phenomenon.     

Insect biogeography in the south-western Sea of Korea with comments on the insect fauna of Kwanmae Island

The insect species richness of each island in the south‐western Sea of Korea was considered on the background of the equilibrium theory. The species number of insects on Kwanmae Island in the present study (140 species) was much higher compared with a previous survey. Based on a literature survey of island biota surveys published in the 1980s, of 47 islands, the lowest species number (12 species) was on Kwanmae Island, and the most diverse insect fauna (254 species) was on Baekryong Island. The mean species number of surveyed islands was approximately 54 (53.96 with a standard deviation of 46.95). The median species number was 38 with a skew of +2.56. Insects, including the orders Odonanta, Orthoptera, Hemiptera, Lepidoptera, Coleoptera, Hymenoptera and Diptera, occurred on 32 of the 47 surveyed islands, and had an occurrence rate of more than 0.68. This indicates that these insects are distributed widely on the islands in the south‐western Sea of Korea. The species number showed a significant linear relationship with both area of an island and its distance from the mainland (P < 0.05), with an extremely low determinant coefficient (r² = 0.13 for area vs species number and r² = 0.28 for distance vs species number). Other factors tested in the study failed to show a significant relationship with species number. A multiple‐regression model established using area and distance as independent variables showed significant relationship with species number, with a relatively higher determinant coefficient (r² = 0.70, P < 0.05). We present possible explanations to explain the difference between estimated and observed species number in Kwanmae Island.     

Are island and mainland biotas different? Richness and level of generalism in parasitoids of a microlepidopteran in Macaronesia

Island communities are exposed to several evolutionary and ecological processes that lead to changes in their diversity and structure compared to mainland biotas. These phenomena have been observed for various taxa but not for parasitoids, a key group in terms of community diversity and functioning. Here we use the parasitoid communities associated with the moth Acroclita subsequana (Lepidoptera: Tortricidae) in the Macaronesian region, to test whether species richness differs between islands and mainland, and whether island parasitoid faunas are biased towards generalist species. Host larvae were collected on several islands and adjacent mainland, carefully searched for ectoparasitoid larvae and dissected to recover any endoparasitoids. Parasitoids were classified as idiobionts, which usually have a wide host range (i.e. generalists), or koinobionts that are considered specialists. Mainland species richness was lower than expected by chance, with most of the species being koinobionts. On the other hand, island communities showed a greater proportion of idiobiont species. Overall parasitism rates were similar between islands and mainland, but islands had higher rates of parasitism by idiobionts than expected by chance, and mainland areas showed the highest koinobiont parasitism rates. These results suggest that island parasitoid communities are dominated by generalists, in comparison to mainland communities. Several hypotheses may explain this pattern: (1) generalist parasitoids might have better dispersal abilities; (2) they may be less constrained by ‘sequential dependencies’; and (3) island parasitoids probably have fewer competitors and/or predators, thus favouring the establishment of generalists. New studies including multiple hosts, other habitats, and/or more islands are necessary to identify which of these processes shape island parasitoid communities.     

Source pools and disharmony of the world's island floras

Island disharmony refers to the biased representation of higher taxa on islands compared to their mainland source regions and represents a central concept in island biology. Here, we develop a generalizable framework for approximating these source regions and conduct the first global assessment of island disharmony and its underlying drivers. We compiled vascular plant species lists for 178 oceanic islands and 735 mainland regions. Using mainland data only, we modelled species turnover as a function of environmental and geographic distance and predicted the proportion of shared species between each island and mainland region. We then quantified the over‐ or under‐representation of families on individual islands (representational disharmony) by contrasting the observed number of species against a null model of random colonization from the mainland source pool, and analysed the effects of six family‐level functional traits on the resulting measure. Furthermore, we aggregated the values of representational disharmony per island to characterize overall taxonomic bias of a given flora (compositional disharmony), and analysed this second measure as a function of four island biogeographical variables. Our results indicate considerable variation in representational disharmony both within and among plant families. Examples of generally over‐represented families include Urticaceae, Convolvulaceae and almost all pteridophyte families. Other families such as Asteraceae and Orchidaceae were generally under‐represented, with local peaks of over‐representation in known radiation hotspots. Abiotic pollination and a lack of dispersal specialization were most strongly associated with an insular over‐representation of families, whereas other family‐level traits showed minor effects. With respect to compositional disharmony, large, high‐elevation islands tended to have the most disharmonic floras. Our results provide important insights into the taxon‐ and island‐specific drivers of disharmony. The proposed framework allows overcoming the limitations of previous approaches and provides a quantitative basis for incorporating functional and phylogenetic approaches into future studies of island disharmony.     

Nestedness in island faunas: novel insights into island biogeography through butterfly community profiles of colonization ability and migration capacity

Aim To relate variation in the migration capacity and colonization ability of island communities to island geography and species island occupancy. Location Islands off mainland Britain and Ireland. Methods Mean migration (transfer) capacity and colonization (establishment) ability (ecological indices), indexed from 12 ecological variables for 56 butterfly species living on 103 islands, were related to species nestedness, island and mainland source geography and indices using linear regression models, RLQ analysis and fourth‐corner analysis. Random creation of faunas from source species, rank correlation and rank regression were used to examine differences between island and source ecological indices, and relationships to island geography. Results Island butterfly faunas are highly nested. The two ecological indices related closely to island occupancy, nestedness rank of species, island richness and geography. The key variables related to migration capacity were island area and isolation; for colonization ability they were area, isolation and longitude. Compared with colonization ability, migration capacity was found to correlate more strongly with island species occupancy and species richness. For island faunas, the means for both ecological indices decreased, and variation increased, with increasing island species richness. Mean colonization ability and migration capacity values were significantly higher for island faunas than for mainland source faunas, but these differences decreased with island latitude. Main conclusions The nested pattern of butterfly species on islands off mainland Britain and Ireland relates strongly to colonization ability but especially to migration capacity. Differences in colonization ability among species are most obvious for large, topographically varied islands. Generalists with abundant multiple resources and greater migration capacity are found on all islands, whereas specialists are restricted to large islands with varied and long‐lived biotopes, and islands close to shore. The inference is that source–sink dynamics dominate butterfly distributions on British and Irish islands; species are capable of dispersing to new areas, but, with the exception of large and northern islands, facilities (resources) for permanent colonization are limited. The pattern of colonization ability and migration capacity is likely to be repeated for mainland areas, where such indices should provide useful independent measures for assessing the conservation status of faunas within spatial units.     

Phenotypic evolution of dispersal-enhancing traits in insular voles

Evolutionary theory predicts that in metapopulations subject to rapid extinction–recolonization dynamics, natural selection should favour evolution of traits that enhance dispersal and recolonization ability. Metapopulations of field voles (Microtus agrestis) on islands in the Stockholm archipelago, Sweden, are characterized by frequent local extinction and recolonization of subpopulations. Here, we show that voles on the islands were larger and had longer feet than expected for their body size, compared with voles from the mainland; that body size and size-specific foot length increased with increasing geographical isolation and distance from mainland; and that the differences in body size and size-specific foot length were genetically based. These findings provide rare evidence for relatively recent (less than 1000 years) and rapid (corresponding to 100–250 darwins) evolution of traits facilitating dispersal and recolonization in island metapopulations.     

Legacy or colonization? Posteruption establishment of peregrine falcons (Falco peregrinus) on a volcanically active subarctic island

How populations and communities reassemble following disturbances are affected by a number of factors, with the arrival order of founding populations often having a profound influence on later populations and community structure. Kasatochi Island is a small volcano located in the central Aleutian archipelago that erupted violently August 8, 2008, sterilizing the island of avian biodiversity. Prior to the eruption, Kasatochi was the center of abundance for breeding seabirds in the central Aleutian Islands and supported several breeding pairs of peregrine falcons (Falco peregrinus). We examined the reestablishment of peregrine falcons on Kasatochi by evaluating the genetic relatedness among legacy samples collected in 2006 to those collected posteruption and to other falcons breeding along the archipelago. No genotypes found in posteruption samples were identical to genotypes collected from pre‐eruption samples. However, genetic analyses suggest that individuals closely related to peregrine falcons occupying pre‐eruption Kasatochi returned following the eruption and successfully fledged young; thus, a genetic legacy of pre‐eruption falcons was present on posteruption Kasatochi Island. We hypothesize that the rapid reestablishment of peregrine falcons on Kasatochi was likely facilitated by behavioral characteristics of peregrine falcons breeding in the Aleutian Islands, such as year‐round residency and breeding site fidelity, the presence of an abundant food source (seabirds), and limited vegetation requirements by seabirds and falcons.     

Genetic and phylogenetic consequences of island biogeography

Abstract.— Island biogeography theory predicts that the number of species on an island should increase with island size and decrease with island distance to the mainland. These predictions are generally well supported in comparative and experimental studies. These ecological, equilibrium predictions arise as a result of colonization and extinction processes. Because colonization and extinction are also important processes in evolution, we develop methods to test evolutionary predictions of island biogeography. We derive a population genetic model of island biogeography that incorporates island colonization, migration of individuals from the mainland, and extinction of island populations. The model provides a means of estimating the rates of migration and extinction from population genetic data. This model predicts that within an island population the distribution of genetic divergences with respect to the mainland source population should be bimodal, with much of the divergence dating to the colonization event. Across islands, this model predicts that populations on large islands should be on average more genetically divergent from mainland source populations than those on small islands. Likewise, populations on distant islands should be more divergent than those on close islands. Published observations of a larger proportion of endemic species on large and distant islands support these predictions.