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220 results for “Island Ecology”
Data from: Ecological, evolutionary and human-mediated determinants of poeciliid species richness on Caribbean islands
Aim: The theory of island biogeography provides a predictive framework relating species richness to island size and distance from the mainland. However, the theory as originally formulated does not necessarily scale to large islands and continental landmasses that are capable of generating species through in situ speciation (rather than entirely by colonization), nor does it necessarily account for how human introduction of species alters traditional biogeographical patterns. Here, we examine the ecological (colonization and extinction), evolutionary (in situ speciation) and human-mediated (deliberate introductions) determinants of species richness in a taxonomic group that has undergone a radiation on Caribbean islands: live-bearing fishes of the family Poeciliidae. Location: The Caribbean. Methods: We created a database of both native and introduced poeciliid species occurrence on Caribbean islands through literature review, and estimated the number of colonizations versus speciation events on each island using a molecular phylogeny. Linear regression and other statistical tests were used to explore species–area and species–isolation relationships. Results: Species richness on small islands results entirely from colonization and does not significantly increase with island area, whereas on larger islands species richness increases dramatically as a function of area due primarily to in situ speciation. Poeciliid fishes have been introduced widely, both as a by-product of their popularity in the aquarium hobby and as a means of mosquito control. We show that such establishments have occurred disproportionately on islands depauperate in native species, and that introduced species richness is positively correlated with economic interconnectedness (shipping traffic) and human population size. Main conclusions: On large Caribbean islands in situ speciation has elevated the number of poeciliid species beyond that predicted from ecological processes alone. Introduced species significantly alter biogeographical patterns.
Data from: Tracking the history and ecological changes of rising double-crested cormorant populations using pond sediments from islands in eastern Lake Ontario
In the Laurentian Great Lakes region, the double-crested cormorant (Phalacrocorax auritus) has seen a thousand-fold population increase in recent decades. These large colonies of birds now often conflict with socioeconomic interests, particularly due to perceived competition with fisheries and the destruction of terrestrial vegetation in nesting habitats. Here we use dated sediment cores from ponds on islands in eastern Lake Ontario that receive waste inputs from dense colonies of cormorants and ring-billed gulls (Larus delawarensis) to chronicle the population rise of these species and assess their long-term ecological impacts. Modern water chemistry sampling from these sites reveals drastically elevated nutrient and major ion concentrations compared to reference ponds not influenced by waterbirds. Geochemical tracers in dated sediment cores, particularly δ15N and chlorophyll-a concentrations, track waterbird influences over time. Fossil diatom assemblages were dominated by species tolerant of hyper-eutrophic and polluted systems, which is in marked contrast to assemblages in reference sites. In addition to establishing long-term ecological impacts, this multi-proxy paleoecological approach can be used to determine whether islands of concern have been long-term nesting sites or were only recently colonized by cormorant or ring-billed gull populations across the Great Lakes, facilitating informed management decisions about controversial culling programs.
Data from: Polar lakes may act as ecological islands to aquatic protists
A fundamental question in ecology is whether microorganisms follow the same patterns as multicellular organisms when it comes to population structure and levels of genetic diversity. Enormous population sizes, predominately asexual reproduction, and presumably high dispersal due to small body size could have profound implications on their genetic diversity and population structure. Here, we have analyzed the population genetic structure in a lake-dwelling microbial eukaryote (dinoflagellate) and tested the hypothesis that there is population genetic differentiation among nearby lake subpopulations. This dinoflagellate occurs in the marine-derived saline lakes of the Vestfold Hills, Antarctica, which are ice-covered most of the year. Clonal strains were isolated from four different lakes, and were genotyped using AFLP (Amplified Fragment Length Polymorphism). Our results show high genetic differentiation among lake populations despite their close geographical proximity (< 9 km). Moreover, genotype diversity was high within populations. Gene flow in this system is clearly limited, either due to physical or biological barriers. Our results discard the null hypothesis that there is free gene flow among protist lake populations. Instead, limnetic protist populations may differentiate genetically, and lakes act as ecological islands even on the microbial scale.
Data from: Spatial and ecological population genetic structures within two island-endemic Aeonium species of different niche width
The Crassulacean genus Aeonium is a well-known example for plant species radiation on oceanic archipelagos. However, while allopatric speciation among islands is documented for this genus, the role of intra-island speciation due to population divergence by topographical isolation or ecological heterogeneity has not yet been addressed. The aim of this study was to investigate intraspecific genetic structures and to identify spatial and ecological drivers of genetic population differentiation on the island scale. We analyzed inter simple sequence repeat variation within two island-endemic Aeonium species of La Palma: one widespread generalist that covers a large variety of different habitat types (Ae. davidbramwellii) and one narrow ecological specialist (Ae. nobile), in order to assess evolutionary potentials on this island. Gene pool differentiation and genetic diversity patterns were associated with major landscape structures in both species, with phylogeographic implications. However, overall levels of genetic differentiation were low. For the generalist species, outlier loci detection and loci–environment correlation approaches indicated moderate signatures of divergent selection pressures linked to temperature and precipitation variables, while the specialist species missed such patterns. Our data point to incipient differentiation among populations, emphasizing that ecological heterogeneity and topographical structuring within the small scales of an island can foster evolutionary processes. Very likely, such processes have contributed to the radiation of Aeonium on the Canary Islands. There is also support for different evolutionary mechanisms between generalist and specialist species.
Data from: Diversification rates of the "Old Endemic" murine rodents of Luzon Island, Philippines are inconsistent with incumbency effects and ecological opportunity
Diversity-dependent cladogenesis occurs when a colonizing lineage exhibits increasing interspecific competition as it ecologically diversifies. Repeated colonization of a region by closely related taxa may cause similar effects as species within each lineage compete with one another. This may be particularly relevant for secondary colonists, which could experience limited diversification due to competition with earlier, incumbent colonists over evolutionary time. We tested the hypothesis that an incumbent lineage may diminish the diversification of secondary colonists in two speciose clades of Philippine "Old Endemic" murine rodents—Phloeomyini and Chrotomyini—on the relatively old oceanic island of Luzon. Although phylogenetic analyses confirm the independent, non-contemporaneous colonization of Luzon by the ancestors of these two clades, we found no support for arrested diversification in either. Rather, it appears that diversification of both clades resulted from constant-rate processes that were either uniform or favored the secondary colonists (Chrotomyini), depending on the method used. Our results suggest that ecological incumbency has not played an important role in determining lineage diversification among Luzon murines, despite sympatric occurrence by constituent species within each lineage, and a substantial head start for the primary colonists.
Data from: Molecular characterisation of trophic ecology within an island radiation of insect herbivores (Curculionidae: Entiminae: Cratopus).
The phytophagous beetle family Curculionidae is the most species-rich insect family known, with much of this diversity having been attributed to both co-evolution with food plants and host-shifts at key points within the early evolutionary history of the group. Less well understood is the extent to which patterns of host use vary within or among related species, largely because of the technical difficulties associated with quantifying this. Here we develop a recently characterised molecular approach to quantify diet within and between two closely related species of weevil occurring primarily within dry forests on the island of Mauritius. Our aim is to quantify dietary variation across populations and assess adaptive and non-adaptive explanations for this, and to characterise the nature of a trophic shift within an ecologically distinct population within one of the species. We find that our study species are polyphagous, consuming a much wider range of plants than would be suggested by the literature. Our data suggest that local diet variation is largely explained by food availability, and locally specialist populations consume food plants that are not phylogenetically novel, but do appear to represent a novel preference. Our results demonstrate the power of molecular methods to unambiguously quantify dietary variation across populations of insect herbivores, providing a valuable approach to understanding trophic interactions within and among local plant and insect herbivore communities.
Data from: Feed or fight: testing the impact of food availability and intraspecific aggression on the functional ecology of an island lizard
Body size often varies among insular populations relative to continental conspecifics – the 'island rule' – and functional, context-dependent morphological differences tend to track this body size variation on islands. Two hypotheses are often proposed as potential drivers of insular population differences in morphology: one relating to diet and the other involving intraspecific competition and aggression. We directly tested whether differences in morphology and maximum bite capacity were explained by interisland changes in hardness of both available and consumed prey, and levels of lizard-to-lizard aggression among small-island populations. Our study included 11 islands in the Greek Cyclades and made use of a gradient in island area spanning five orders of magnitude. We focused on the widespread lizard Podarcis erhardii. We found that on smaller islands, P. erhardii body size was larger, head height was larger relative to body size, and maximum bite capacity became proportionally stronger. This pattern in morphology and performance was not related to differences in diet, but was highly correlated with proxies of intraspecific aggression – bite scars and missing toes. Our findings suggest that critical functional traits such as body size and bite force in P. erhardii follow the predictions of the island rule and are changing in response to changes in the competitive landscape across islands of different sizes.
FIGURE 10 in Simuliidae (Diptera) of the Solomon Islands: new records and species, ecology, and biogeography
FIGURE 10. Simulium (M.) nr. selwynense, Makira (Santa Cristobal). Penultimate/early lastinstar larva. a, left lateral view. b, pharate pupal gill. c, hypostomal teeth. d, mandible teeth, sensillum, and serrations. e, dorsal view of head, probably female. f, hypostoma and postgenal cleft. g, anal sclerite and circlet of hooks.
FIGURE 5a–c in Simuliidae (Diptera) of the Solomon Islands: new records and species, ecology, and biogeography
FIGURE 5a–c. Simulium (M.) nr. selwynense, Santa Isobel. Lastinstar larvae. a, left lateral views, female upper, male lower. b, dorsal view of female larva head. c, dorsal view of male larva head.
FIGURE 7 in Simuliidae (Diptera) of the Solomon Islands: new records and species, ecology, and biogeography
FIGURE 7. Simulium (G.) rhopaloides n. sp. Guadalcanal. Early last instar larva, Holotype. a, left lateral view. b, pharate pupal gill. c, hypostomal teeth. d, mandible teeth, sensillum, and serrations. e, dorsal view of head. f, hypostoma and postgenal cleft. g, anal sclerite and circlet of hooks.
FIGURE 4 in Simuliidae (Diptera) of the Solomon Islands: new records and species, ecology, and biogeography
FIGURE 4. Simulium (M.) nr. selwynense, Rendova, New Georgia Islands. Lastinstar larva. a, left lateral view. b, pharate pupal gill. c, hypostomal teeth. d, mandible teeth, sensillum, and serrations. e, dorsal view of head. f, hypostoma and postgenal cleft. g, anal sclerite and circlet of hooks.
FIGURE 1 in Simuliidae (Diptera) of the Solomon Islands: new records and species, ecology, and biogeography
FIGURE 1. Bougainville (PNG) and the Solomon Islands. The 200m bathymetric contour is indicated. Numbers and letters associated with islands are number of recognised species and subgenus (M = Morops, G = Gomphostilbia).
FIGURE 5 in Simuliidae (Diptera) of the Solomon Islands: new records and species, ecology, and biogeography
FIGURE 5. Simulium (M.) nr. selwynense, Santa Isobel. Lastinstar larvae. d, pharate pupal gill. e, hypostomal teeth. f, anal sclerite and circlet of hooks. g, hypostoma and postgenal cleft. h, mandible teeth, sensillum, and serrations.
FIGURE 9a–c in Simuliidae (Diptera) of the Solomon Islands: new records and species, ecology, and biogeography
FIGURE 9a–c. Simulium (M.) nr. pohaense, Malaita. Last instar larva. a, left lateral view, male. b, dorsal view, female larva head. c, dorsal view, male larva head.
FIGURE 3 in Simuliidae (Diptera) of the Solomon Islands: new records and species, ecology, and biogeography
FIGURE 3. Simulium (G.) noroense, New Georgia, New Georgia Islands. Penultimate instar larva. a, left lateral view. b, pharate pupal gill. c, hypostomal teeth. d, mandible teeth, sensillum, and serration. e, dorsal view of head. f, hypostoma and postgenal cleft. g, anal sclerite and circlet of hooks.
FIGURE 2 in Simuliidae (Diptera) of the Solomon Islands: new records and species, ecology, and biogeography
FIGURE 2. Simulium (G.) noroense, Kolumbangara, New Georgia Islands. Penultimate instar larva. a, left lateral view. b, pharate pupal gill. c, hypostomal teeth. d, mandible teeth, sensillum, and serration. e, dorsal view of head. f, hypostoma and postgenal cleft. g, anal sclerite and circlet of hooks.
FIGURE 11 in Simuliidae (Diptera) of the Solomon Islands: new records and species, ecology, and biogeography
FIGURE 11. Localities of new Simuliidae material from the Solomon Islands. a, Stream near Ringgi, Kolumbangara, New Georgia Islands. b, Upper Sakumbare River, New Georgia, New Georgia Islands. c, Upper Toropi River, Rendova, New Georgia Islands (J. Polhemus in background). d, Garana River (3 km inland), Santa Isabel. e, Charovuga River, Guadalcanal. f, Aluta River, cascade, Malaita (R. Englund in background). g, Puepue River, Makira.
FIGURE 8 in Simuliidae (Diptera) of the Solomon Islands: new records and species, ecology, and biogeography
FIGURE 8. Simulium (G.) hiroshii, Malaita. Female adult. a, left lateral view. b, frontal view of head. Specimen in alcohol.
FIGURE 9d–h in Simuliidae (Diptera) of the Solomon Islands: new records and species, ecology, and biogeography
FIGURE 9d–h. Simulium (M.) nr. pohaense, Malaita. Last instar larva. d, pharate pupal gill. e, hypostomal teeth. f, anal sclerite and circlet of hooks. g, hypostoma and postgenal cleft. h, mandible teeth, sensillum, and serrations
FIGURES 58–62 in New data on geometroid moths (Lepidoptera: Geometroidea: Uraniidae and Geometridae) from Sakhalin and Moneron islands with notes on their taxonomy distribution and ecology
FIGURES 58–62. Genitalia of Geometridae from Sakhalin. 58—Abraxas niphonibia, 59–60—Acasis exviretata, 61—Trichopteryx hemana, form A, 62—T. hemana, form B. 58, 60— female genitalia, 59, 61, 62—male genitalia (a—genital segment, b—aedeagus). Scale—1 mm.
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