Orientation and ingestion rates of larval Anopheles albimanus in response to floating particles

Response of fourth-instar larvae of Anopheles albimanus Wiedemann (Diptera: Culicidae) to food and inert particles floating at the water surface was studied. In a choice test, larvae aggregated at powdered organic materials (blood meal, liver powder alfalfa flour and wheat flour) but not at inert materials (kaolin, chalk or charcoal). Larvae responded positively to proteins as well as some carbohydrates, but not to cellulose. Retention of larvae at food sources found by random locomotion was found to be responsible for larval aggregation. Larvae ingested food particles 6–9 times faster than insert particles. The significance of Anopheline feeding behavior in the development of formulations of stomach toxins (bacterial agents) used in larval control is discussed.

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Zusammenfassung Die vorliegende Studie befasst sich mit Verhaltensreaktionen von Anopheles albimanus Viertlarven auf an der Wasseroberfläche schwimmende Partikel. Verteilung und Orientierung der Larven wurde in einer Wahlapparatur quantifiziert. Nach Auftrag von Alfalfamehl, Weizenmehl, Stärke, Blutmehl, Leberpulver und Fischmehl wurde Aggregation der Larven in den beköderten Fächern der Apparatur beobachtet. Sowohl Proteine (Casein) als auch einige Kohlehydrate (Amylose, Amylopectin) lösten Aggregationen der Larven aus. Im Unterschied dazu führte Auftrag von Kreide, Kaolin, Polyaethylenpulver, Talcum oder Cellulose nicht zu Aggregationen. Zur Beschreibung der Entstehung larvaler Aggregationen bei Futterstoffen wurden die Schwimmbewegungen der Larven in Anwesenheit von Weizenmehl als Ködersubstanz quantifiziert. Da keine Attraktion der Larven im Sinne einer gerichteten Schwimmbewegung beobachtet werden konnte, wird geschlussfolgert, dass sofortige Beendung der Suchaktivität der Larven bei zufällig gefundenen Futterquellen für die beobachteten Aggregationen bei organischen Substanzen verantwortlich ist.Die Fressraten der Larven bei Angebot verschiedener Substanzen im Überschuss wurde bestimmt. Larven fülten drei von insgesamt sechs Darmabschnitten innerhalb von 15–30 min bei Angebot von Futtersubstanzen, während die Füllung von nur zwei Darmabschnitten mit inerten Materialien erst nach 90–120 min zu beobachten war. Die Resultate werden in Bezug auf wasseroberflächengebundene Formulierungen von Frassgiften diskutiert. Inerte Trägersubstanzen werden wahrscheinlich wesentlich langsamer aufgenommen als Futtersubstanzen. Da An. albimanus Larven nicht von Futterquellen angezogen werden, ist eine rasche und wirksame Giftaufnahme besonders dann zu erwarten, wenn die gesamte Oberfläche der Brutgewässer mit toxinhaltigen Trägerpartikeln bedeckt werden kann.

     

Late Pleistocene divergence and subsequent population expansion of two closely related fish species, Japanese anchovy (Engraulis japonicus) and Australian anchovy (Engraulis australis)

Climatic oscillations during the Pleistocene ice ages produced great changes in species' geographical distribution and abundance, which could be expected to have genetic consequences. Living in the temperate upwelling zones of the northwestern Pacific, Japanese anchovy (Engraulis japonicus) might have been affected by these severe climatic oscillations. To investigate the effects of Pleistocene climatic changes on the evolution in Japanese anchovy, fragments of 522 bp at the 5' end of mitochondrial DNA control region were sequenced for 241 individuals from 13 localities and 37 individuals of Australian anchovy. Japanese anchovy and Australian anchovy are reciprocally monophyletic and a late Pleistocene transequatorial divergence between the two species was indicated. High levels of haplotype diversity (>0.99) were found for all samples, indicating a high level of genetic diversity. Analyses of molecular variance and the conventional population statistic F(ST) revealed no significant genetic structure throughout the range of Japanese anchovy. Both mismatch distribution analyses and neutrality tests suggested a late Pleistocene population expansion for both Japanese anchovy (79,000-317,000 years ago) and Australian anchovy (45,000-178,000 years ago).     

Complex population history of two Anopheles dirus mosquito species in Southeast Asia suggests the influence of Pleistocene climate change rather than human-mediated effects

Anopheles dirus and Anopheles baimaii are closely related species which feed on primates, particularly humans, and transmit malaria in the tropical forests of mainland Southeast Asia. Here, we report an in-depth phylogeographic picture based on 269 individuals from 21 populations from mainland Southeast Asia. Analysis of 1537 bp of mtDNA sequence revealed that the population history of A. baimaii is far more complex than previously thought. An old expansion (pre-300 kyr BP) was inferred in northern India/Bangladesh with a wave of south-eastwards expansion arriving at the Thai border (ca 135-173 kyr BP) followed by leptokurtic dispersal very recently (ca 16 kyr BP) into peninsular Thailand. The long and complex population history of these anthropophilic species suggests their expansions are not in response to the relatively recent (ca 40 kyr BP) human expansions in mainland Southeast Asia but, rather, fit well with our understanding of Pleistocene climatic change there.     

Phylogeography of Diadophis punctatus: extensive lineage diversity and repeated patterns of historical demography in a trans-continental snake

Dynamic climatic oscillations during the Pleistocene had profound effects on the distributions of species across North America. Although the role of historical climate change on speciation remains controversial, the impact on genetic variation within species has been well documented. We examined mtDNA sequences from the cytochrome b gene (1117 bp) and a portion of the NADH-4 gene (659 bp) for 286 individuals of Diadophis punctatus to infer phylogeographic patterns and population structure and to examine historical demographic patterns in both glaciated and unglaciated regions of North America. We inferred 14 lineages that replace each other geographically across the United States. Several of these lineages appear to be confined to specific habitats (floodplains, grasslands, montane environments) and traverse previously identified genetic barriers for terrestrial vertebrates including the Mississippi and Apalachicola Rivers, the Appalachian Mountains, and the western continental divide. We also observed overlapping ranges between some haplotype groups and several instances of secondary contact associated with ecological transition zones in eastern South Carolina, southern Oklahoma and central California. Within the US, diversification began during the late Miocene and continued into the mid-Pleistocene, suggesting these lineages pre-dated the last glacial maximum. Coalescent and non-coalescent demographic analyses indicate that independent lineages currently occupying previously glaciated or unsuitable areas in eastern, central and western US underwent post-glacial population expansion likely from southern refugia during the late Pleistocene/early Holocene. Conversely, southern lineages display patterns consistent with long-term population stability. Such long-term persistence of genetic structure may be due to the competitive effects between lineages or ecosystem stability in more southern latitudes.     

Distinct population structure for co-occurring Anopheles goeldii and Anopheles triannulatus in Amazonian Brazil

To evaluate whether environmental heterogeneity contributes to the genetic heterogeneity in Anopheles triannulatus, larval habitat characteristics across the Brazilian states of Roraima and Pará and genetic sequences were examined. A comparison with Anopheles goeldii was utilised to determine whether high genetic diversity was unique to An. triannulatus. Student t test and analysis of variance found no differences in habitat characteristics between the species. Analysis of population structure of An. triannulatus and An. goeldii revealed distinct demographic histories in a largely overlapping geographic range. Cytochrome oxidase I sequence parsimony networks found geographic clustering for both species; however nuclear marker networks depicted An. triannulatus with a more complex history of fragmentation, secondary contact and recent divergence. Evidence of Pleistocene expansions suggests both species are more likely to be genetically structured by geographic and ecological barriers than demography. We hypothesise that niche partitioning is a driving force for diversity, particularly in An. triannulatus.     

Silencing the genes for dopa decarboxylase or dopachrome conversion enzyme reduces melanization of foreign targets in Anopheles gambiae

The production of melanin is a complex biochemical process in which several enzymes may play a role. Although phenoloxidase and serine proteases are clearly key components, the activity of other enzymes, including dopa decarboxylase and dopachrome conversion enzyme may also be required. We tested the effect of knockdown of gene expression for these two enzymes on melanization of abiotic targets in the mosquito, Anopheles gambiae. Knockdown of dopa decarboxylase and dopachrome conversion enzyme resulted in a significant reduction of melanization of Sephadex beads at 24 h after injection. Knockdown of a third enzyme, phenylalanine hydroxylase, which is involved in endogenous production of tyrosine, had no effect on bead melanization. Quantitative analysis of gene expression demonstrated significant upregulation of phenylalanine hydroxylase, but not the other two genes, following injection.     

Immunostaining for allatotropin and allatostatin-A and -C in the mosquitoes <Emphasis Type="Italic">Aedes aegypti</Emphasis> and <Emphasis Type="Italic">Anopheles albimanus</Emphasis>

Confocal laser-scanning microscopy was used to carry out a comparative study of the immunostaining for three families of neuropeptides, viz., allatostatin-A (AS-A), allatostatin-C (AS-C) and allatotropin (AT), in adult female mosquitoes of Aedes aegypti and Anopheles albimanus. The specific patterns of immunostaining for each of the three peptides were similar in both species. The antisera raised against AT, AS-A, and AS-C revealed intense immunoreactivity in the cells of each protocerebral lobe of the brain and stained cells in each of the ventral ganglia and neuronal projections innervating various thoracic and abdominal tissues. Only the AS-A antiserum labeled immunoreactive endocrine cells in the midgut. The distribution of the peptides supports the concept that they play multiple regulatory roles in both species.This work was supported by NIH grant AI 45545 to F.G.N. and CONACyT G-37186-M to M.H.R.     

Genetic diversity of Microcystis populations in a bloom and its relationship to the environmental factors in Qinhuai River, China

Cyanobacterial blooms, forming massive scum and various cyanotoxins, increasingly spread in a wide range of freshwater ecosystems. One heavy Microcystis bloom occurred in the entire Qinhuai River basin in 2010 summer for the first time. To determine the Microcystis populations and their spatial distributions along Qinhuai River, a molecular approach was applied by sequencing the DNA library based on the internal transcribed spacer sequences of 16-23S rRNA (ITS). The parsimony network (TCS) analysis showed that 9 groups were formed based on the main 24 genotypes, and each group was dominated by one highly represented root sequence. Marked changes in the composition and proportion of the Microcystis ITS genotype were detected from the upper to the lower reaches. The seed sources forming the bloom were probably located at 4 different locations. Furthermore, it was found that pH was the primary factor affecting the spatial distribution of the main genotype group among samples.     

Patterning of geographic variation in Middle Pleistocene Homo frontal bone morphology

A quantitative assessment of the frontal bone morphology of a sample of Middle Pleistocene hominins was undertaken in order to address questions regarding their population structure and evolutionary history. Outline tracings of the frontal bones of forty-seven fossil crania were obtained, and size-standardized measurements were then computed using an Elliptical Fourier analysis of these tracings. Principal component scores of the Fourier harmonic amplitudes were derived and served as a quantitative representation of the morphology of the frontal bone. Morphological, geographical, and temporal distance matrices were then constructed between each pair of fossils. A partial Mantel matrix correlation test was performed between morphological and geographical distance matrices, controlling for temporal distance, in order to determine if the pattern of geographical differentiation in features of the frontal bone of mid-Pleistocene Homo followed that of an isolation-by-distance model of population structure. The results of the partial Mantel tests indicate that the overall patterning of differentiation in the features of the frontal bone cannot best be explained by a population structure shaped by isolation-by-distance. Additionally, various aspects of the frontal bone quantified here follow different patterns of geographical differentiation, suggesting that a mosaic pattern of evolution holds true for characters within one cranial region and not just for those between regions.     

North American Glyptodontines (Xenarthra, Mammalia) in the Upper Pleistocene of northern South America

The Glyptodontidae is one of the most conspicuous groups in the Pleistocene megafauna of the Americas. The Glyptodontinae were involved in the Great American Biotic Interchange (GABI) and their earliest records in North America are about 3.9 Ma, suggesting an earlier formation of the Panamanian landbridge. Taxonomically it is possible to recognize two Pleistocene genera of Glyptodontinae:Glyptodon (ca. 1.8 – 0.008 Ma), restricted to South America, andGlyptotherium (ca. 2.6 – 0.009 Ma), including records in both North and Central America. Here we present the first report of the genusGlyptotherium in South America, from the Late Pleistocene of several fossil localities in Falcón State, northwestern Venezuela. A comparative analysis of the material, represented by cranial and postcranial parts, including the dorsal carapace and caudal rings, suggests a close affinity withGlyptotherium cylindricum (Late Pleistocene of Central Mexico). This occurrence in the latest Pleistocene of the northernmost region of South America Supports the bidirectional faunal migration during the GABI and the repeated re-immigration from North America of South American clades, as has been reported in other members of the Cingulata (e.g., Pampatheriidae).      

Genetic diversity and population divergence in fragmented habitats: Conservation of Idaho ground squirrels

The Idaho ground squirrel, which consists of a northern (Spermophilus brunneus brunneus) and a southern subspecies (S. b. endemicus), has suffered from habitat loss and fragmentation, resulting in a reduction in both numbers and geographic range of the species. The northern Idaho ground squirrel (NIDGS) is listed as a threatened subspecies under the Endangered Species Act, and the southern Idaho ground squirrel (SIDGS) is a candidate. Because Idaho ground squirrel populations are small and often isolated, they are susceptible to inbreeding and loss of genetic diversity through drift. This research evaluates levels of genetic diversity and patterns of population divergence in both subspecies of Idaho ground squirrels. We hypothesized that NIDGS would exhibit lower genetic diversity and greater population divergence due to a longer period of population isolation relative to most SIDGS populations. Genetic diversity and divergence were quantified using 8 microsatellite loci. Contrary to expectations, SIDGS populations exhibited consistently lower levels of microsatellite diversity. Additionally, NIDGS exhibited only modest divergence among populations, while divergence levels among SIDGS populations were highly varied. Preliminary evaluations of mitochondrial DNA diversity and structure revealed lower diversity in NIDGS and some differences in gene flow that warrant further study. Based on our results, we suggest different management strategies for the two subspecies. Habitat restoration appears to be the most desirable conservation strategy for NIDGS populations. In contrast, low genetic diversity observed in SIDGS may warrant supplementation of isolated populations through translocations or captive breeding to mitigate further loss of genetic variability.     

High evolutionary divergence of the 5.8S ribosomal DNA in Mimulus glaucescens (Scrophulariaceae)

Ribosomal DNA sequences for the ITS 1, 5.8S, ITS 2 and adjoining regions of the 18S and 25S were obtained from Mimulus glaucescens (Scrophulariaceae) via cloned PCR products. The spacer sequences were completely unrelated to other plant taxa, although spacer lengths were approximately the same. Interestingly, the Mimulus 5.8S sequence was much more divergent than other higher-plant rDNA sequences. Consideration of the secondary structure of the 5.8S rRNA shows that most of the changes in Mimulus are compensatory and preserve the basic secondary structure of the mature RNA molecule.     

Determinants of spatial distribution in a population of the subalpine butterfly Oeneis chryxus

Summary This paper describes temporally varying determinants of the spatial distribution of adults in an insect population and the relationship between that distribution and the mating system. Male Oeneis chryxus butterflies were distributed nonrandomly throughout a sloping Colorado meadow divided horizontally by a dirt road into an upper and lower slope. Over an eight-year period of intensive study, the proportion of males located on the road, the upper slope, and the lower slope varied as a function of population size and sex ratio. In each year, more than half of the male population aggregated on sections of the road in a distinct and recurring pattern that was not correlated with the distribution of any food resource or thermal regime. Females were usually extremely scarce and not distributed in any pattern apparent from the few observations of them. Areas densely occupied by males were associated with visual landmarks. We hypothesize that the male distribution is determined by a pattern of movement of receptive females toward these landmarks. The road offers a thermally favorable environment with an unobstructed view in which to await the passage of scarce females. The mating system in this population has several lek-like features and supports the prediction that landmark mating is a favored strategy under conditions of female scarcity and wide dispersal of resources.     

Modulation of pigment profiles of Calothrix elenkenii in response to environmental changes

Cyanobacteria are versatile tetrapyrrole synthesizers that can regulate their tetrapyrrole content and composition in response to environmental signals. The present investigation analyses the interplay between light and dark regimes (continuous light, light-dark cycles (16:8) and continuous darkness) and aerobic, air-tight, and anaerobic environments (argon-enriched), on the relative composition of various pigments and growth attributes of Calothrix elenkenii as a prelude to exploiting C. elenkenii's bioindustrial potential as a source of pigments. Incubation in an anaerobic environment stimulated hormogonia formation and induced colouration/thickening of cells. Aerobically grown cultures of Calothrix, under continuous illumination produced the maximum amount of total phycobiliproteins and sugars, although chlorophyll accumulation and nitrogenase activity were highest in the light-dark environment. However, the beta-carotene content was observed to vary under anaerobic conditions with different light-dark regimes. This C. elenkenii strain can be a valuable source of pigments under optimized environmental conditions.     

Status and structure of the griffon vulture (Gyps fulvus) population in Crete

Griffon vulture (Gyps fulvus) population surveys were conducted during 1996–2002 in the island of Crete (Greece) to document population status and structure. Fieldwork was carried out during the breeding period when birds could be monitored in their colonies. Total population size was estimated at 379 individuals (range = 341–417) with adult birds comprising 63%. The breeding population was estimated at 141 pairs, which were distributed on an average in 23 colonies per year (range = 16–30) while the mean number of breeding pairs that laid eggs was 98 (range= 64–126). Crete thus supports the largest insular population of the species in the world and hosts 70–80% of the breeding population of the species in Greece. Population density was estimated at 6.9 individuals/100 km², 2.6 breeding pairs/100 km² and 1.8 nesting pairs/100 km². The average home range of an occupied colony (i.e., breeding group) was estimated at ca. 204 km² producing a theoretical foraging range of 8 km radius around the breeding cliff. No trends in the total number of individuals and breeding pairs appeared to exist, although significant differences in population size of individual colonies occurred between the years. The majority of the population was concentrated in small-sized colonies, which showed a low occupancy rate. The number of abandoned sites and the colonization of new ones could represent a shift of breeding pairs to alternative colonies provoked by local food abundance and conspesific attraction.     

Internal Repetition and Intraindividual Variation in the rDNA ITS1 of the <Emphasis Type="Italic">Anopheles punctulatus</Emphasis> Group (Diptera: Culicidae): Multiple Units and Rates of Turnover

The rapid divergence of repetitive sequences makes them desirable markers for phylogenetic studies of closely related groups, provided that a high level of sequence homogeneity has been maintained within species. Intraspecific polymorphisms are found in an increasing number of studies now, and this highlights the need to determine why these occur. In this study we examined intraindividual variation present in the first ribosomal internal transcribed spacer (ITS1) from a group of cryptic mosquito species. Individuals of the Anopheles punctulatus group contained multiple ITS1 length variants that ranged from 1.2 to 8.0 kb. Nucleotide and copy number variation for several homologous internal repeats is common, yet the intraspecific sequence divergence of cloned PCR isolates is comparable to that of other mosquito species (~0.2–1.5%). Most of the length variation is comprised of a 5′-ITS1 repeat that was identified as a duplication of a conserved ITS2 region. Secondary structure conservation for this repeat is pronounced and several repeat types that are highly homogenized have formed. Significant interspecific divergence indicates a high rate of evolutionary change for this spacer. A maximum likelihood tree constructed here was congruent with previous phylogenetic hypotheses and suggests that concerted evolution is also accompanied by interpopulation divergence. The lack of interindividual differences and the presence of homogenized internal repeats suggest that a high rate of turnover has reduced the overall level of variation. However, the intraindividual variation also appears to be maintained by the absence of a single turnover rate and the complex dynamics of ongoing recombination within the spacer. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Intraspecific Concerted Evolution of the rDNA ITS1 in Anopheles farauti Sensu Stricto (Diptera: Culicidae) Reveals Recent Patterns of Population Structure

We examined the intraindividual variation present in the first ribosomal internal transcribed spacer (ITS1) of Anopheles farauti to determine the level of divergence among populations for this important malarial vector. We isolated 187 clones from 70 individuals and found regional variation among four internal tandem repeats. The data were partitioned prior to analysis given the presence of a paralogous ITS2 sequence, called the 5'-subrepeat, inserted in the ITS1 of most clones. A high level of homogenization and population differentiation was observed for this repeat, which indicates a higher rate of turnover relative to the adjacent 'core' region. Bayesian analysis was performed using several substitutional models on both a combined and a partitioned data set. On the whole, the ITS1 phylogeny and geographic origin of the samples appear to be congruent. Some interesting exceptions indicate the spread of variant repeats between populations and the retention of ancestral polymorphism. Our data clearly demonstrate concerted evolution at the intraspecific level despite intraindividual variation and a complex internal repeat structure from a species that occupies a continuous coastal distribution. A high rate of genomic turnover in combination with a high level of sequence divergence appears to be a major factor leading to its concerted evolution within these populations.     

Occurrence of Theropithecus sp. in the Late Villafranchian of Southern Italy and implication for Early Pleistocene "out of Africa" dispersals

Three cervical vertebrae of a large primate have been identified in the revision of the faunal assemblage collected during the late '70s from fissure fillings in the area known as Pirro Nord in southern Italy. By size the three vertebrae are comparable to the large fossil species Theropithecus oswaldi, however we prefer here to attribute the remains to Theropithecus sp. The Pirro Nord Theropithecus represents the second finding outside of Africa of this genus in association with Megantereon whitei, after the site of 'Ubeidiya. The biochronology of Pirro Nord faunal assemblage demonstrates that the arrival into Europe of Theropithecus occurred earlier than thought: in the range of approx 1.6-1.3 Ma. The identification of an European "African assemblage" (Theropithecus associated with Megantereon whitei) has consequences for interpretation of an "out of Africa" (genus Homo) event around the Plio-Pleistocene transition.     

Influence of climate and community composition on the population demography of pasture species in semi-arid Australia

Substantial recruitment of Callitris glaucophylla in woodland, Sclerolaena birchii in cleared woodland, and Astrebla lappacea in grassland is related to catastrophic events of the past century in the form of interactions between climate, the impact of European land use (sheep, cattle, rabbits) and the rabbit myxoma epizootic. The direct effect of rainfall on the demography of these species and its indirect effect through competition via suites of accompanying plant species are examined. Major long-term changes in plant populations are generated by extreme sequential events rather than by random isolated events. One of the most potent climatic agents for change in eastern Australia is the El Niño/Southern Oscillation phenomenon.     

A time series and geographical analysis of population dynamics of the red-backed vole in Hokkaido,Japan

Summary A time series and geographical analysis of the long term (25-years and 16-years) census data of the red-backed vole, Clethrionomys rufocanus bedfordiae, populations in Hokkaido, Japan was carried out. Eighty seven populations from all over Hokkaido were grouped into the following 4 types according to their flucturation patterns: type A: low density-constant type; type B: medium density-gradual increase type; type C: medium density-wavy change type; type D: high density-large amplitude type. The border between type B and type C was not clear. Although the distribution of the fluctuation types did not show any geographical cline, the high density type (type D) occurred in limited areas where the winter was severe and spring came later and almost all the populations in the Oshima peninsula were the low density type (type A). The most common type of population in Hokkaido, type C, greatly fluctuated from year to year with the maximum density level/the minimum one being over 10. The periodicity of the peak years was not statistically significant, although peaks often occurred at 3 or 4 year intervals. The population grew from spring to autumn in almost all years so that the pattern of the seasonal change was qualitatively constant. The population density levels in spring were not significantly different between peak years and others, while those in autumn were greatly different between them, so that the population growth rates from spring to autumn were variable from year to year. This differential pattern was also found between high and low density areas.