Abstract Aim To reassess the relationships between Tarentola geckos from the Cape Verde Islands by including specimens from all islands in the range. To determine the variation within forms by sequencing over 400 specimens, thereby allowing the discovery of cryptic forms and resolving some of the issues raised previously. This extensive sampling was also used to shed light on distributions and to explain genetic diversity by comparing the ages and ecological and geological features of the islands (size, elevation and habitat diversity).Location The Cape Verde Islands: an oceanic archipelago belonging to the Macaronesian biogeographic region, located around 500 km off Senegal.Methods A total of 405 new specimens of Tarentola geckos were collected from nine islands with very different geological histories, topography, climate and habitats. Mitochondrial cytochrome b (cyt b) gene and 12S rRNA partial sequences were obtained and analysed using phylogenetic methods and networks to determine molecular diversity, demographic features and phylogeographic patterns.Results The phylogenetic relationships between all known forms of Cape Verdean Tarentola specimens were estimated for the first time, the relationships between new forms were assessed and previously hypothesized relationships were re‐examined. Despite the large sample size, low intraspecific diversity was found using a 303‐bp cyt b fragment. Star‐like haplotype networks and statistical tests suggest the past occurrence of a rapid demographic and geographical expansion over most of the islands. Genetic variability is positively correlated with size, elevation and habitat diversity of the islands, but is not linearly related to the age of the islands. Biogeographical patterns have, in general, high concordance with phylogenetic breaks and with the three eco‐geographical island groups. Volcanism and habitat diversity, both tightly linked with island ontogeny, as postulated by the general dynamic model of oceanic island biogeography, as well as present and historical size of the islands appear to be the main factors explaining the genetic diversity of this group.Main conclusions The Tarentola radiation was clarified and is clearly associated with the geological and ecological features of the islands. Two factors may account for the low intraspecific variation: (1) recent volcanic activity and high ecological stress, and (2) poor habitat diversity within some islands. More studies are needed to align taxonomy with phylogenetic relationships, whereas GIS modelling may help to predict precise species distributions.

The Galapagos Islands are among the most important nesting areas for the green sea turtle, Chelonia mydas, in the eastern Pacific Ocean. In addition, the coastal waters of this oceanic archipelago host many important feeding areas for this species, although little is known about green turtle feeding ecology at these sites. The goal of this study was to identify and quantify the most important items in the diet of the green turtle at the foraging grounds of Bahia Elizabeth, Caleta Derek and Punta Nuñez. Our analysis was based on 65 oesophageal samples from turtles captured in 2006 and 2007. We compared spatial and seasonal composition of diet using non-metric multidimensional scaling analysis (MDS) and analysis of similarity (ANOSIM). Green turtle diet was composed mainly of the algae species Ulva lactuca, Polysiphonia sp., Hypnea sp. and Dictyota sp., and the red mangrove Rhizophora mangle. Turtles also consumed animal matter, mainly cnidarians, albeit to a lesser extent. Content of turtle diets was different among feeding grounds and seasons. The ANOSIM showed that diet composition can differ between foraging grounds using presence/absence of diet items. Even though U. lactuca was the most abundant algae consumed in both seasons, changes in species richness of algae were found between both sampling events, with diet during the warm season more varied than the cold season (χ2 = 16.84, df = 6; P < 0.05).

Abstract: The study of distinct biogeographic demarcations has played a pivotal role in our understanding processes responsible for patterns of species distributions and, importantly, the role of geologic processes in promoting biotic diversification. Biogeographic barriers such as Wallace's line have been shown to be the result of old geologic processes shaping ancient faunal or floral diversification events. Based on distributions of birds, bats, reptiles, plants, and invertebrates we identify a distinct biogeographic disjunction in Vanuatu, a geologically nascent oceanic archipelago. We discuss mechanisms contributing to this concordant pattern across these disparate taxonomic groups in light of geologic history, ocean currents, vegetation, soil, and bioclimatic data, and propose the name Cheesman's line to indicate the faunal and floral discontinuity between the northern and southern islands of Vanuatu.

Divergence times and colonization of the Canary Islands by Gallotia lizards

Additive partitioning as a tool for investigating the flora diversity in oceanic archipelagos

Biogeographers study all patterns in the geographic variation of life, from the spatial variation in genetic and physiological characteristics of cells and individuals, to the diversity and dynamics of biological communities among continental biotas or across oceanic archipelagoes. The field of island biogeography, in particular, has provided some genuinely transformative insights for the biological sciences, especially ecology and evolutionary biology. Our purpose here is to review the historical development of island biogeography theory during the 20th century by identifying the common threads that run through four sets of contributions made during this period, including those by Eugene Gordon Munroe (1948, 1953), Edward O. Wilson (1959, 1961), Frank W. Preston (1962a,b), and the seminal collaborations between Wilson and Robert H. MacArthur (1963, 1967), which revolutionized the field and served as its paradigm for nearly four decades. This epistemological account not only reviews the intriguing history of island theory, but it also includes fundamental lessons for advancing science through transformative integrations. Indeed, as is likely the case with many disciplines, island theory advanced not as a simple accumulation of facts and an orderly succession of theories and paradigms, but rather in fits and starts through a reticulating phylogeny of ideas and alternating periods of specialization and reintegration. We conclude this review with a summary of the salient features of this scientific revolution in the contest of Kuhn's structure, which strongly influenced theoretical advances during this period, and we then describe some of the fundamental assumptions and tenets of an emerging reintegration of island biogeography theory.

Abstract Aim It is well established that many groups of plants and animals have undergone long‐distance dispersal, but the extent to which this continues beyond initial colonization is largely unknown. To provide further insight into the frequency of gene flow mediated by long‐distance dispersal, we investigated the origins of the fern Asplenium hookerianum on the Chatham Islands, and present a review of the contribution of molecular data to elucidating the origins of this archipelago’s biota.Location Chatham Islands and New Zealand. A. hookerianum is scarce on the Chatham Islands but common in New Zealand, some 800 km to the west.Methods We compared chloroplast trnL–trnF DNA sequence data from Chatham Islands’A. hookerianum with extensive phylogeographic data for this genetically variable species in mainland New Zealand.Results Our sequencing revealed the presence of two haplotypes in Chatham Islands’A. hookerianum. These haplotypes differed by four mutational events and were each more closely related to haplotypes found in New Zealand than to each other.Main conclusions Despite the rarity of A. hookerianum on the Chatham Islands, its populations there appear to derive from at least two long‐distance dispersal events from New Zealand, these possibly originating from different areas. We suggest that long‐distance transoceanic dispersal, and the gene flow it can mediate, may be more common than is generally appreciated.

The littorinid genus Echinolittorina is of global distribution on rocky shores in topical latitudes, but in terms of the number of sympatric species and of phylogenetic diversity the genus reaches is greatest richness in the western Atlantic biogeographic region. The systematics of Echinolittorina in the western Atlantic have been controversial, owing to both intraspecific variability and convergence in traditional taxonomic characters of the shell and radula, and also to lack of anatomical descriptions. As a result of recent molecular studies the species can now be defined. Detailed morphological descriptions are provided here for the ten known living species, including details of shell, operculum, pigmentation of headfoot, reproductive anatomy, spermatozoa, egg capsules and radulae. Diagnoses include reference to mitochondrial gene sequences (COI). A key is based on shells, opercula, penial shapes and geographical distributions, and includes all other littorinid species (members of genera Littoraria, Cenchritis and Tectarius) found in the western Atlantic region, to avoid confusion. Based on molecular phylogenetic analysis, the ten species are assigned to four subgenera: Fossarilittorina, Lineolittorina n. subgen., Amerolittorina n. subgen. and Echinolittorina. One new species is described: E. placida n. sp. from the Gulf of Mexico. One name change is proposed: E. jamaicensis (C.B. Adams, 1850) replaces Nodilittorina riisei (Mörch, 1876), N. glaucocincta (Mörch, 1876) and N. mordax Bandel & Kadolsky, 1982. It is confirmed that the forms previously discriminated as Nodilittorina tuberculata (Menke, 1828) and N. dilatata (d’Orbigny, 1842) belong to a single species, E. tuberculata (Menke, 1828). These five ‘species’ of ‘Nodilittorina’ were diagnosed solely by striking differences in their radulae in a previous taxonomic study, but it is here shown that this variation is intraspecific, although the cause is unknown. New COI sequences are included in a phylogenetic analysis to support this conclusion. Full synonymies are given for all taxa, and the taxonomic, evolutionary and ecological literature reviewed. Distribution maps are based on examination of 1091 samples and on reliable literature records. The biogeography of the western Atlantic marine region is discussed, based on the ten distribution maps, emphasizing the mutual isolation of the Gulf of Mexico, Caribbean Sea, Brazilian mainland and Brazilian oceanic archipelagos, and the significance of the contrast between oceanic and continental distribution patterns. In E. mespillum there is a conspicuous polymorphism of shell colour with a geographical pattern, and mimicry is suggested. The natural distribution of E. placida n. sp. is on the sparse rocky outcrops of the southern Gulf of Mexico, but following the widespread construction of sea walls along the sedimentary coastline of the Gulf since the late nineteenth century, this species has spread for 4500 km around the Gulf, to Florida and as far as North Carolina in about 100 years. Occasional black shells are found within populations of normally variegated Echinolittorina species, which has not been recorded in congeners from other oceans.

Oceanic islands of volcanic origin have a narrow shelf and a steep slope that should lead to considerable spatial overlap among coastal and oceanic fauna. During six pelagic surveys in the Canarian archipelago, Eastern Central Atlantic, over 65,000 fishes belonging to 211 species were collected at depths between 8 and 1035 m. The mesopelagic families of the lanternfishes (Myctophidae) and the bristlemouths (Gonostomatidae) accounted for about 50% of all specimens. By multivariate classification and ordination methods four different assemblages associated with mesopelagic, epipelagic–oceanic or coastal habitats could be identified. Two of these assemblages were coastal, differing in the proportion of meso- and epipelagic species. These data indicate intense horizontal migrations of mesopelagic fishes (mainly Myctophidae) into the neritic realm and increased interactions between coastal and oceanic habitats. Alpha diversity indices were higher and dominance was lower in oceanic habitats compared to the coastal realm. No marked differences among oceanographically similar areas of the entire archipelago were found. Beta diversity as a measure of similarity among sites or samples revealed variabilities between areas south of Gran Canaria and Fuerteventura islands. A considerable heterogeneity in species distribution was found off SE Fuerteventura in an area with high hydrographic variability. Therefore, both topography and hydrography are important factors influencing the distribution and abundance of pelagic fishes in this oceanic archipelago.

One island group suggested to be an exception to the species–area Relationship is the Vanuatu Archipelago, a group of 13 large and 80 small islands in the southwest Pacific Ocean. To test the hypothesis that the lizard fauna of the Vanuatu Archipelago does not meet the predictions of the species‐area relationship, and thus is depauperate, we compare diversity among several island groups in the southwest Pacific: Fiji, the Loyalty Islands, New Caledonia, Samoa, the Solomon Islands, Tonga, and Vanuatu. We found that the lizard diversity of Vanuatu meets the pattern of diversity predicted by the species‐area relationship. The Solomon Islands, the largest and least isolated oceanic archipelago considered, has the greatest species diversity and endemism of the oceanic islands. Inclusion or exclusion of island groups based on factors such as geologic history or faunal source affects the strength of the relationship between diversity, area, and history of emergence, and influences perceptions of diversity within individual archipelagos. In addition to island size, factors such evolutionary time scale, speciation, and archipelago complexity influence species richness on islands.

Oceanic archipelagos are considered hot-spots of biodiversity because they harbor unique biota with a high level of endemicity. However, the endemic biodiversity of oceanic islands is very vulnerable to extinction. In recent decades, intensive exploitation of these territories and human-mediated introduction of alien species have posed unprecedented threats to the long-term survival of the endemic contingent. The very limited population genetic information available until now for the 28 Canarian endemic Echium taxa has hindered the development of conservation strategies for the ca. 25% of them that are under threat. In this paper, we analyze the levels and distribution of genetic isozyme diversity in 23 natural populations of three endangered endemics of restricted distribution (E. acanthocarpum, CR; E. onosmifolium ssp. spectabile, EN; and E. callithyrsum, VU), and two endemics of wide distribution and in principle free of threat (E. decaisnei and E. onosmifolium). Our results reveal high levels of genetic variability in all these taxa that have plausibly been reached despite a predominance of selfing. They also point out a high incidence of inbreeding in the reproductive dynamics of populations and suggest the potential value of hybridisation processes in shaping the genetic makeup of these species. Among-population differentiation, as estimated by Gst, and genetic distances within taxa are low overall, but they do support the current taxonomic separation between the two subspecies of E. onosmifolium and do not furnish evidence that the current status of the endangered species may be attributed to genetic factors. We use the genetic parameters to suggest some guidelines to help implement a conservation strategy of these taxa.

Factors that influence speciation rates among groups of organisms are integral to deciphering macroevolutionary processes; however, they remain poorly understood. Here, we use molecular phylogenetic data and divergence time estimates to reconstruct the pattern and tempo of speciation within a widespread and homogeneous bird family (white-eyes, Zosteropidae) that contains an archetypal "great speciator." Our analyses show that the majority of this species-rich family constitutes a clade that arose within the last 2 million years, yielding a per-lineage diversification rate among the highest reported for vertebrates (1.95-2.63 species per million years). However, unlike most rapid radiations reported to date, this burst of diversification was not limited in geographic scope, but instead spanned the entire Old World tropics, parts of temperate Asia, and numerous Atlantic, Pacific, and Indian Ocean archipelagos. The tempo and geographic breadth of this rapid radiation defy any single diversification paradigm, but implicate a prominent role for lineage-specific life-history traits (such as rapid evolutionary shifts in dispersal ability) that enabled white-eyes to respond rapidly and persistently to the geographic drivers of diversification.

Are the IUCN standard home-range thresholds for species a good indicator to prioritise conservation urgency in small islands? A case study in the Canary Islands (Spain)

Abstract Aim To explore the determinants of island occupancy of 48 terrestrial bird species in an oceanic archipelago, accounting for ecological components while controlling for phylogenetic effects.Location The seven main islands of the Canary archipelago.Methods We obtained field data on population density, habitat breadth and landscape distribution in Tenerife, Fuerteventura and La Palma, aiming to sample all available habitats and the gradient of altitudes. In total, 1715 line transects of 0.5 km were carried out during the breeding season. We also reviewed the literature for data on occupancy, the distance between the Canary Islands and the nearest distribution border on the mainland, body size and endemicity of the 48 terrestrial bird species studied. Phylogenetic eigenvector regression was used to quantify (and to control for) the amount of phylogenetic signal.Results The two measurements of occupancy (number of occupied islands or 10 × 10 km UTM squares) were tightly correlated and produced very similar results. The occupancy of the terrestrial birds of the Canary Islands during the breeding season had a very low phylogenetic effect. Species with broader habitat breadth, stronger preferences for urban environments, smaller body size, and a lower degree of endemicity had a broader geographical distribution in the archipelago, occupying a larger number of islands and 10 × 10 UTM squares.Main conclusions The habitat‐generalist species with a tolerance for novel urban environments tend to be present on more islands and to occupy a greater area, whereas large‐sized species that are genetically differentiated within the islands are less widespread. Therefore, some properties of the ranges of these species are explicable from basic biological features. A positive relationship of range size with local abundance, previously shown in continental studies, was not found, probably because it relies on free dispersal on continuous landmasses, which may not be applicable on oceanic islands.

There is little information on introduced European rabbit populations in the Canary Islands, an oceanic archipelago close to the north-west coast of Africa. Seasonal changes in rabbit abundance have important consequences for the management of this species. The study involved spotlight counts of wild rabbits over 3 years to characterize patterns of seasonal abundance through time and across insular biotopes. There were more rabbits at the beginning of summer than in late autumn or early winter in all years and biotopes. Coastal biotopes had more rabbits than had other biotopes, probably because of good grass cover, a factor associated with rabbit abundance. There was no seasonal change in rabbit abundance among biotopes. Adjusting hunting seasons to seasonal variations in rabbit abundance could be used to control populations of this species.

New Zealand biogeography has been dominated by the knowledge that its geophysical history is continental in nature. The continental crust (Zealandia) from which New Zealand is formed broke from Gondwanaland ca 80 Ma, and there has existed a pervading view that the native biota is primarily a product of this long isolation. However, molecular studies of terrestrial animals and plants in New Zealand indicate that many taxa arrived since isolation of the land, and that diversification in most groups is relatively recent. This is consistent with evidence for species turnover from the fossil record, taxonomic affinity, tectonic evidence and observations of biological composition and interactions. Extinction, colonization and speciation have yielded a biota in New Zealand which is, in most respects, more like that of an oceanic archipelago than a continent.

ECOLOGY The equilibrium theory of island biogeography, developed in the 1960s by MacArthur and Wilson, has been the principal reference point for ecologists investigating how the dynamic processes of colonization, speciation, and extinction affect biodiversity in insular habitats. However, the theory has been less successful when applied to longer-term evolution on oceanic islands, where geological dynamics such as erosion come into play. Whittaker et al. have developed a general dynamic model (GDM) that takes account of the humped trend in an oceanic island's carrying capacity over its entire life span. The model generates predictions about the biotic properties (species diversity, rates of speciation and extinction) of oceanic islands that fit snugly with data from oceanic archipelagoes, including the Hawaiian islands and the Galapagos (shown above) among others. By unifying evolutionary and ecological time scales and processes in a single theoretical framework, the GDM adds to the understanding of island biology. — AMS J. Biogeogr. 35 , 977 (2008).

Neurodevelopmental effects of maternal nutritional status and exposure to methylmercury from eating fish during pregnancy

Abstract Aim Oceanic islands represent a special challenge to historical biogeographers because dispersal is typically the dominant process while most existing methods are based on vicariance. Here, we describe a new Bayesian approach to island biogeography that estimates island carrying capacities and dispersal rates based on simple Markov models of biogeographical processes. This is done in the context of simultaneous analysis of phylogenetic and distributional data across groups, accommodating phylogenetic uncertainty and making parameter estimates more robust. We test our models on an empirical data set of published phylogenies of Canary Island organisms to examine overall dispersal rates and correlation of rates with explanatory factors such as geographic proximity and area size.Location Oceanic archipelagos with special reference to the Atlantic Canary Islands.Methods The Canary Islands were divided into three island‐groups, corresponding to the main magmatism periods in the formation of the archipelago, while non‐Canarian distributions were grouped into a fourth ‘mainland‐island’. Dispersal between island groups, which were assumed constant through time, was modelled as a homogeneous, time‐reversible Markov process, analogous to the standard models of DNA evolution. The stationary state frequencies in these models reflect the relative carrying capacity of the islands, while the exchangeability (rate) parameters reflect the relative dispersal rates between islands. We examined models of increasing complexity: Jukes–Cantor (JC), Equal‐in, and General Time Reversible (GTR), with or without the assumption of stepping‐stone dispersal. The data consisted of 13 Canarian phylogenies: 954 individuals representing 393 taxonomic (morphological) entities. Each group was allowed to evolve under its own DNA model, with the island‐model shared across groups. Posterior distributions on island model parameters were estimated using Markov Chain Monte Carlo (MCMC) sampling, as implemented in MrBayes 4.0, and Bayes Factors were used to compare models.Results The Equal‐in step, the GTR, and the GTR step dispersal models showed the best fit to the data. In the Equal‐in and GTR models, the largest carrying capacity was estimated for the mainland, followed by the central islands and the western islands, with the eastern islands having the smallest carrying capacity. The relative dispersal rate was highest between the central and eastern islands, and between the central and western islands. The exchange with the mainland was rare in comparison.Main conclusions Our results confirm those of earlier studies suggesting that inter‐island dispersal within the Canary Island archipelago has been more important in explaining diversification within lineages than dispersal between the continent and the islands, despite the close proximity to North Africa. The low carrying capacity of the eastern islands, uncorrelated with their size or age, fits well with the idea of a historically depauperate biota in these islands but more sophisticated models are needed to address the possible influence of major recent extinction events. The island models explored here can easily be extended to address other problems in historical biogeography, such as dispersal among areas in continental settings or reticulate area relationships.

González, J. A., C. Montes, J. Rodríguez, and W. Tapia. 2008. Rethinking the Galapagos Islands as a complex social-ecological system: implications for conservation and management. Ecology and Society 13(2): 13. https://doi.org/10.5751/ES-02557-130213