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Culex quinquefasciatus Say (Diptera: Culicidae), an important vector of West Nile virus (WNV) in the U.S.A., was first detected on the Galápagos Islands (Ecuador) in the 1980s. However, little is known of its ecology, distribution or capacity for arbovirus transmission in the Galápagos. We characterize details of lifecycle (including gonotrophic period), temporal abundance, spatial distribution, vector competence and host‐feeding behaviour. Culex quinquefasciatus was detected on five islands of the Galápagos during 2006–2011. A period of 7–14 days was required for egg–adult emergence; water salinity above 5 ppt was demonstrated to hinder larval development. Blood‐meal analysis indicated feeding on reptiles, birds and mammals. Assessment of WNV vector competency of Galápagos C. quinquefasciatus showed a median infectious dose of 7.41 log10 plaque‐forming units per millilitre and evidence of vertical transmission (minimal filial infection rate of 3.7 per 1000 progeny). The distribution of C. quinquefasciatus across the archipelago could be limited by salt intolerance, and its abundance constrained by high temperatures. Feeding behaviour indicates potential to act as a bridge vector for transmission of pathogens across multiple taxa. Vertical transmission is a potential persistence mechanism for WNV on Galápagos. Together, our results can be used for epidemiological assessments of WNV and target vector control, should this pathogen reach the Galápagos Islands.  相似文献   

3.
On Floreana, the smallest inhabited island in the Galápagos, populations of several species of birds have either been extirpated or, based on anecdotal evidence and small‐scale surveys, are declining. Our objective, therefore, was to conduct a comprehensive survey of landbirds encompassing the entire island during three breeding seasons (2014–2016). We conducted surveys at 59 points in 2014, 257 in 2015, and 295 in 2016. Each survey point was sampled once. We detected 12 species during our surveys. Galápagos Flycatchers, Yellow Warblers, Small and Medium ground‐finches, and Small Tree‐Finches were widely distributed over the entire island. Common Cactus‐Finches and Medium Tree‐Finches had more restricted distributions in the lower or higher parts of the island. Few Dark‐billed Cuckoos (Coccyzus melacoryphus), Paint‐billed Crakes (Neocrex erythrops), Galápagos Doves (Zenaida galapagoensis), and Galápagos Short‐eared Owls (Asio flammeus galapagoensis) were recorded. Small Ground‐Finches and Small Tree‐Finches were found at densities comparable to those on other Galápagos Islands, whereas densities of Galápagos Flycatchers and Yellow Warblers were higher on Floreana than on other islands. Endemic Medium Tree‐Finches were confined to an area of 24 km², mainly in the highlands, but were still widespread and common in their restricted habitat, with the number of territories estimated to be between 3900 and 4700. Of 22 originally occurring landbirds on Floreana, no fewer than 10 species have either been extirpated or are likely to have been extirpated since the arrival of the first human inhabitants. The combined effects of introduced mammals, large‐scale habitat destruction, and direct human persecution were responsible for the extirpation of six species during the 19th century. Three additional species have been extirpated since 1960, likely due to the introduction of the parasitic fly Philornis downsi, and this fly remains a major threat for the remaining bird species. Developing strategies for reducing the impact of these flies on the birds of the Galapagos Islands must be a high priority. In addition, habitat management and restoration, including the control of invasive plants and promotion of native tree species, will be critically important in conserving landbird populations on Floreana.  相似文献   

4.
This article describes a new diatom genus Moreneis from the Yellow Sea sand flats on the west coast of Korea. The new genus is characterized by a unique combination of morphological characteristics, including the shape of the plastids, which have not been previously observed in diatoms. The valve morphology resembles other genera belonging to Lyrellaceae, within which we place this genus. In terms of areolae structure, Moreneis resembles Petroneis and Placoneis; however, it differs from both genera with respect to the raphe system and plastid shape. Cells of Moreneis spp. have a single large plastid appressed to the girdle of the secondary side of the valve, with two lobes extended toward the primary side of the valve. Furthermore, the unique feature of Moreneis frustules is the raphe, which has both external central and apical endings bent in opposite directions. We differentiated four taxa, which we describe as new for science. However, based on our findings, several established species from Navicula should also be formally transferred to Moreneis, including N. alpha Cleve, N. besarensis Giffen, N. epsilon Cleve, N. menaiana Hendey, N. polae Heiden, and N. quadri‐undulata F. Meister. Analysis of published data revealed that species belonging to Moreneis are numerous in tropical marine littoral waters, and in moderate climate zones, especially in the western Pacific, with only a few species occurring in the Mediterranean and Atlantic.  相似文献   

5.
Aim Large‐bodied vertebrates often have a dramatic role in ecosystem function through herbivory, trampling, seed dispersal and nutrient cycling. The iconic Galápagos tortoises (Chelonoidis nigra) are the largest extant terrestrial ectotherms, yet their ecology is poorly known. Large body size should confer a generalist diet, benign digestive processes and long‐distance ranging ability, rendering giant tortoises adept seed dispersers. We sought to determine the extent of seed dispersal by Galápagos tortoises and their impact on seed germination for selected species, and to assess potential impacts of tortoise dispersal on the vegetation dynamics of the Galápagos. Location Galápagos, Ecuador. Methods To determine the number of seeds dispersed we identified and counted intact seeds from 120 fresh dung piles in both agricultural and national park land. To estimate the distance over which tortoises move seeds we used estimated digesta retention times from captive tortoises as a proxy for retention times of wild tortoises and tortoise movement data obtained from GPS telemetry. We conducted germination trials for five plant species to determine whether tortoise processing influenced germination success. Results In our dung sample, we found intact seeds from > 45 plant species, of which 11 were from introduced species. Tortoises defecated, on average, 464 (SE 95) seeds and 2.8 (SE 0.2) species per dung pile. Seed numbers were dominated by introduced species, particularly in agricultural land. Tortoises frequently moved seeds over long distances; during mean digesta retention times (12 days) tortoises moved an average of 394 m (SE 34) and a maximum of 4355 m over the longest recorded retention time (28 days). We did not find evidence that tortoise ingestion or the presence of dung influenced seed germination success. Main conclusions Galápagos tortoises are prodigious seed dispersers, regularly moving large quantities of seeds over long distances. This may confer important advantages to tortoise‐dispersed species, including transport of seeds away from the parent plants into sites favourable for germination. More extensive research is needed to quantify germination success, recruitment to adulthood and demography of plants under natural conditions, with and without tortoise dispersal, to determine the seed dispersal effectiveness of Galápagos tortoises.  相似文献   

6.
Aim  To infer the most plausible explanations for the presence of 14 species of the Neotropical cucurbit genus Sicyos on the Hawaiian Islands, two on the Galápagos Islands, two in Australia, and one in New Zealand. Location  Neotropics, the Hawaiian and Galápagos archipelagos, Australia and New Zealand. Methods  We tested long‐problematic generic boundaries in the tribe Sicyoeae and reconstructed the history of Sicyos using plastid and nuclear DNA sequences from 87 species (many with multiple accessions) representing the group’s generic and geographic diversity. Maximum likelihood and Bayesian approaches were used to infer relationships, divergence times, biogeographic history and ancestral traits. Results  Thirteen smaller genera, including Sechium, are embedded in Sicyos, which when re‐circumscribed as a monophyletic group comprises 75 species. The 14 Hawaiian species of Sicyos descended from a single ancestor that arrived c. 3 million years ago (Ma), Galápagos was reached twice at c. 4.5 and 1 Ma, the species in Australia descended from a Neotropical ancestor (c. 2 Ma), and New Zealand was reached from Australia. Time since arrival thus does not correlate with Sicyos species numbers on the two archipelagos. Main conclusions  A plausible mechanism for the four trans‐Pacific dispersal events is adherence to birds of the tiny hard fruit with retrorsely barbed spines found in those lineages that underwent long‐distance migrations. The Hawaiian clade has lost these spines, resulting in a lower dispersal ability compared with the Galápagos and Australian lineages, and perhaps favouring allopatric speciation.  相似文献   

7.
We report eight novel microsatellite loci for Colpocephalum turbinatum, a parasitic louse of the endangered Galápagos hawk (Buteo galapagoensis). Two island populations of C. turbinatum (N = 30) were genotyped for each locus. We found between two and 12 alleles per locus, polymorphic information content from 0.268 to 0.798, observed heterozygosity from 0.067 to 0.667 and no linkage disequilibrium was detected between loci. These markers will be useful in understanding contemporary gene flow of C. turbinatum among islands in the Galápagos and in understanding transmission dynamics between B. galapagoensis hosts, within and between social groups. Because this louse is unusually widespread among avian host taxa, parasitizing at least 53 bird species in the Falconiformes, Strigiformes and Columbiformes, these markers are likely to be useful outside the context of the Galápagos Islands.  相似文献   

8.
The deposition of siliceous valves during asexual reproduction of the pennate diatom, Navicula cuspidata Kütz., is described with emphasis on the cytoplasmic components involved. The events accompanying valve secretion are similar to those already known from other pennate species. After mitosis, the microtubule centre (MC) moves to the center of the cleavage furrow where silica deposition is initiated inside a tubular silicalemma, and it remains associated with the prospective central nodule during valve growth. Microtubules (MTs), emanating from the MC, run parallel to the prospective raphe and together with the raphe fibres, appear to be involved with raphe development. Multiple raphe fibres occupy the maturing raphe fissure, in contrast to the single fibre of Pinnularia viridis, P. maior and Hantzschia amphioxys. The fibers exhibit a periodic substructure and are often opposed to the silicalemma where they may inhibit silica deposition and control the shaping of the raphe fissure. In contrast with the above species, in N. cuspidata MTs are clustered strictly opposite the raphe and lose their association with the MC which degenerates before the valves are mature. The primary role of MTs may be the stabilization of the cytoplasmic region where initial silicification occurs. Mitochondria and endoplasmic reticulum are not involved in molding valve growth in this species. Evidence for vesicle involvement in silica transport and deposition was limited. The possible contributions provided by comparative studies on the ultrastructure of valve morphogenesis towards elucidating the control of valve formation and the taxonomy of diatoms are discussed briefly.  相似文献   

9.
Galápagos hawks (Buteo galapagoensis) are one of the most inbred bird species in the world, living in small, isolated island populations. We used mitochondrial sequence and nuclear minisatellite data to describe relationships among Galápagos hawk populations and their colonization history. We sampled 10 populations (encompassing the entire current species range of nine islands and one extirpated population), as well as the Galápagos hawk's closest mainland relative, the Swainson's hawk (B. swainsoni). There was little sequence divergence between Galápagos and Swainson's hawks (only 0.42% over almost 3kb of data), indicating that the hawks colonized Galápagos very recently, likely less than 300,000 years ago, making them the most recent arrivals of the studied taxa. There were only seven, closely related Galápagos hawk haplotypes, with most populations being monomorphic. The mitochondrial and minisatellite data together indicated a general pattern of rapid population expansion followed by genetic isolation of hawk breeding populations. The recent arrival, genetic isolation, and phenotypic differentiation among populations suggest that the Galápagos hawk, a rather new species itself, is in the earliest stages of further divergence.  相似文献   

10.
This study puts together genetic data and an approximate bayesian computation (ABC) approach to infer the time at which the tree Geoffroea spinosa colonized the Galápagos Islands. The genetic diversity and differentiation between Peru and Galápagos population samples, estimated using three chloroplast spacers and six microsatellite loci, reveal significant differences between two mainland regions separated by the Andes mountains (Inter Andean vs. Pacific Coast) as well as a significant genetic differentiation of island populations. Microsatellites identify two distinct geographical clusters, the Galápagos and the mainland, and chloroplast markers show a private haplotype in the Galápagos. The nuclear distinctiveness of the Inter Andean populations suggests current restricted pollen flow, but chloroplast points to cross‐Andean dispersals via seeds, indicating that the Andes might not be an effective biogeographical barrier. The ABC analyses clearly point to the colonization of the Galápagos within the last 160 000 years and possibly as recently as 4750 years ago (475 generations). Founder events associated with colonization of the two islands where the species occurs are detected, with Española having been colonized after Floreana. We discuss two nonmutually exclusive possibilities for the colonization of the Galápagos, recent natural dispersal vs. human introduction.  相似文献   

11.
Periphytic diatoms are potentially powerful indicators of environmental change in climatically‐sensitive high latitude regions. However, only a few studies have examined their taxonomic and ecological characteristics. We identified and enumerated diatom assemblages from sediment, rock, and moss habitats in 34 ultra‐oligotrophic and highly transparent lakes and ponds on Victoria Island, Arctic Canada. The similar limnological characteristics of the sites allowed us to examine the influence of habitat, independent of water chemistry, on the diatom assemblages. As is typical in shallow arctic water bodies, benthic taxa, including species of Achnanthes, Caloneis, Cymbella, Navicula, and Nitzschia, were most widely represented. Minor gradients in our measured environmental variables did not significantly explain any variance in diatom species, but there were marked differences in diatom assemblages among sites. Pond ephemerality seems to explain some diatom variation, because aerophilic taxa such as Achnanthes kryophila Petersen and A. marginulata Grunow were dominant in shallow sites that had undergone appreciable reductions in volume. We identified several taxa that exhibited strong habitat preferences to sediment, moss, or rock substrates and also found significant differences (P < 0.01) in diatom composition among the three habitats. In comparisons with three similar diatom surveys extending over 1200 km of latitude, we determined that surface sediment assemblages differed significantly (P < 0.001) among all regions examined. Diatom species diversity was inversely related to latitude, a result likely explained by differences in the lengths of growing seasons. These data contribute important ecological information on diatom assemblages in arctic regions and will aid in the interpretation of environmental changes in biomonitoring and paleolimnological studies.  相似文献   

12.
Within most island archipelagos, such as the Galápagos, similar ecological gradients are found on geographically isolated islands. Species radiations in response to these ecological gradients may follow different scenarios being (i) a single habitat specialization event followed by secondary colonization of each ecotype on the different islands or (ii) repeated and parallel habitat specialization on each island separately. This latter scenario has been considered less likely as gene flow might hamper such ecotypic differentiation. At least for the Galápagos, the extent to which this process is involved in species radiations remains yet poorly understood. Within the wolf spider genus Hogna, seven species are described that can be divided into three different ecotypes based on general morphology and habitat preference i.e. species that inhabit the pampa vegetation in the highlands, species that occur in coastal dry habitats and one generalist species. Comparison of the species phylogeny based on one mitochondrial (COI) and one nuclear (28S) gene fragment convincingly demonstrates that ‘pampa’ and ‘coastal dry’ species evolved in parallel on the islands Santa Cruz and San Cristóbal. Despite the observation that allozymes analysis indicated that each species forms a distinct genetic cluster, phylogenetic divergence within these species complexes was very low and paraphyletic and most likely due to hybridization rather than incomplete lineage sorting, as demonstrated for the Santa Cruz species complex. This suggests that within‐island speciation occurred under low levels of gene flow. Species phylogeny in general did not follow the progression of island emergence as a molecular clock analysis suggested that island endemic species may have diverged after as well as before the emergence of the islands. This represents the first clear example of parallel and within‐island speciation because of habitat specialization on the Galápagos and that such divergence most likely occurred under historic gene flow.  相似文献   

13.
Human activity has facilitated the introduction of a number of alien mammal species to the Galápagos Archipelago. Understanding the phylogeographic history and population genetics of invasive species on the Archipelago is an important step in predicting future spread and designing effective management strategies. In this study, we describe the invasion pathway of Rattus rattus across the Galápagos using microsatellite data, coupled with historical knowledge. Microsatellite genotypes were generated for 581 R. rattus sampled from 15 islands in the archipelago. The genetic data suggest that there are at least three genetic lineages of R. rattus present on the Galápagos Islands. The spatial distributions of these lineages correspond to the main centers of human settlement in the archipelago. There was limited admixture among these three lineages, and these finding coupled with low rates of gene flow among island populations suggests that interisland movement of R. rattus is rare. The low migration among islands recorded for the species will have a positive impact on future eradication efforts.  相似文献   

14.
We isolated and characterized 10 novel dinucleotide microsatellite loci from the Galápagos sea lion (Zalophus californianus wollebaeki) and tested their amplification utility in four further otariid species (Zalophus californianus californianus, Arctocephalus gazella, Arctocephalus australis and Eumetopias jubatus) and three phocid species (Hydrurga leptonyx, Halichoerus grypus and Phoca vitulina). All of the loci amplified polymorphic polymerase chain reaction (PCR) products in at least three species other than the Galápagos sea lion. These markers will be useful for studies of pinniped mating systems, genetic structure and genetic diversity.  相似文献   

15.
The endemic large carpenter bee, Xylocopa darwini Cockerell, was the only known pollinator to the Galápagos Archipelago but as early as 1964 locals also spoke of the “dwarf bee of Floreana”. We report the presence of the wool carder bee, Anthidium vigintiduopunctatum Friese, on the island of Floreana and use a species distribution model to predict its distribution in the archipelago. We found that this species has the potential to invade almost one-third the surface area of the Galápagos Archipelago, primarily in low arid areas. Given that wool carder bees are uncommonly collected, we discuss whether this species is a previously undetected native bee or a recent adventive species to the Galápagos.  相似文献   

16.
Notes on the Poaceae of the Robinson Crusoe (Juan Fernández) Islands, Chile, Brittonia 54: 154–163. 2001.—Poaceae in the Robinson Crusoe (=Juan Fernández) Islands number 53 species in 32 genera, of which 9% of the species are endemic, 9% indigenous, and 81% adventitious. The endemic taxa (and their conservation status) are:Agrostis masafuerana (rare),Chusquea fernandeziana (not endangered),Megalachne berteroana (not endangered),M. masafuerana (not endangered), andPodophorus bromoides (extinct).Megalachne andPodophorus are endemic genera. Comparisons with Poaceae in the Bonin and Volcano Islands, Canary Islands, Galápagos Islands, and Hawaiian Islands show different levels of endemism: number of endemic taxa, respectively, 5, 10, 12, 40; percent specific endemism, 8, 6, 21, 19. No endemic genera occur.Anthoxanthum odoratum, Avena barbata andHordeum murinum are noxious weeds in the Robinson Crusoe Islands. Many adventives are shared among floras of the archipelagos, with the highest ties of Robinson Crusoe being to the Canaries (53% of total Poaceae known in Juan Fernández) and the Hawaiian Islands (47%). Low levels of adventives occur within the Bonin (5%) and Galápagos (7%) Islands. In contrast, there are many endemic genera of Asteraceae in these same archipelagos: Bonin and Volcano Islands (1), Canary Islands (8), Galápagos Islands (5), and Hawaiian Islands (6); percent of specific endemism is also higher (20, 53, 54 and 56, respectively). Hypotheses for greater levels of endemics among oceanic island Asteraceae include more efficient dispersal mechanisms by wind and birds, animal pollination systems that result in greater degrees of geographic populational genetic isolation, and a vascular cambium that offers enhanced growth-form evolutionary opportunities.  相似文献   

17.
Since nobody has witnessed the arrival of early plant colonists on isolated islands, the actual long‐distance dispersal (hereafter LDD) has historically been a matter of speculation. In the present study, we offer a new approach that evaluates whether particular syndromes for LDD (i.e. the set of traits related to diaspore dispersal by animals, wind and sea currents) have been favourable in the natural colonization of the Galápagos Islands by plants. Dispersal syndromes of the 251 native genera (509 angiosperm species) presently acknowledged as native were carefully studied, combining data from floristic lists of the Galápagos Islands, diaspore traits, characteristics of continental relatives and our own observations. We used these genera (and occasionally infrageneric groups) as the working units to infer the number of introductions and colonists. A final number of native plants was inferred and analysed after correcting by pollen records of six species from six genera previously considered exotic (palaeobotanical correction). The number of early colonists was also corrected by incorporating information from the few (n= 12) phylogenetic studies of genera from both the Galápagos Islands and the Americas (phylogenetic correction). A total of 372 colonization events were inferred for the native flora using the latest check‐list. The proportions of native colonists grouped into five categories were: endozoochory 16.4%, epizoochory 15.7%, hydrochory 18.6%, anemochory 13.3%, and unassisted diaspores 36.0%. These figures did not vary significantly on analysing only the 99 genera that include endemic species in order to rule out any human‐mediated introductions. Irrespective of the roles of the different agents involved in LDD, diaspores with no special syndrome for LDD (unassisted diapores), such as many dry fruits, have been successful in reaching and colonizing the Galápagos archipelago. This finding leads us to suggest that unpredictable and so far unknown LDD mechanisms should be further considered in the theory of island biogeography.  相似文献   

18.
The breeding strategies of 52 Galápagos Islands angiosperms from 30 families were examined. Controlled pollinations were performed to determine if self-incompatiblity was more prevalent than previously thought, thus acting as an enforcer of outcrossing, or if instead, both dioecism and self-incompatibility are poorly represented and self-compatibility is the rule. The plants tested were located in each of the seven major vegetation zones on the southern slope of Isla Santa Cruz. Fruit and seed yields were compared between tagged but uncovered flowers (controls) and others that were subjected to various manipulations. Of the 52 species studied, one was dioecious, 11 yielded inconclusive results, and the remaining 40 showed self-compatibility. All but three of the latter group also demonstrated automatic self-pollination. This study suggests that on the Galápagos Islands hermaphroditic and dioecious plants occur in relatively the same proportions as found in their mainland source areas. Of the two hermaphroditic breeding strategies considered in this study, self-compatibility and self-incompatibility, the former is highly represented in the Galápagos flora.  相似文献   

19.
Aim The aims of this study were (1) to investigate whether the two growth forms of Darwiniothamnus Harling (Asteraceae) originated from the colonization of a single ancestor, (2) to identify the closest relative(s) of Darwiniothamnus, and (3) to review molecular phylogenies from other plant groups to infer the origin of Galápagos endemics. Location Darwiniothamnus is endemic to the Galápagos Islands. Methods All putative relatives of Darwiniothamnus plus 38 additional species were included. Nucleotide sequences of the internal transcribed spacers of the nuclear ribosomal DNA were used for Bayesian and parsimony analyses. Results Darwiniothamnus is polyphyletic. Two species (D. lancifolius (Hook. f.) Harling and D. tenuifolius (Hook. f.) Harling) are woody shrubs that usually grow to 1–2 m in height; they belong to a clade composed of species otherwise restricted to the Caribbean. These two species are sister to Erigeron bellidiastroides Griseb., a herbaceous species endemic to Cuba. The third species (D. alternifolius Lawesson & Adsersen) is a perennial herbaceous plant, woody at the base and reaching only up to 50 cm in height. It is sister to two Chilean (Coquimbo–Valparaiso region) species that also have a perennial herbaceous habit: E. fasciculatus Colla and E. luxurians (Skottsb.) Solbrig. They are placed in an assemblage restricted to South America. The review of previous molecular phylogenetic studies revealed that two of the endemic genera and endemic species of three non‐endemic genera have their closest relatives in South America. Endemic species belonging to three non‐endemic genera have sister species in North America or the West Indies. One endemic genus and endemic species in three non‐endemic genera have sister taxa with a widespread continental distribution, or their molecular phylogenies yielded equivocal results. Main conclusions The flora of Galápagos has affinities with both North America (including the Antilles) and South America. Darwiniothamnus exhibits both patterns: two species of this genus are sister to a taxon endemic to Cuba, supporting a connection between the Cocos plate and the West Indies; the third species, D. alternifolius, provides a link with the Coquimbo–Valparaiso region, suggesting a biogeographical connection between the Nazca plate and southern South America.  相似文献   

20.
Five microsatellite loci were isolated from the Galápagos caterpillar hunter Calosoma granatense. Polymorphism ranges from four to 14 alleles, and observed and expected heterozygosities range from 0.138 to 0.889 and 0.197–0.902, respectively. Cross‐amplification of the developed primers was successful in the related species C. leleuporum.  相似文献   

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