Knowing the past to predict the future: land‐use change and the distribution of invasive bullfrogs

Biological invasions and land‐use changes are two major causes of the global modifications of biodiversity. Habitat suitability models are the tools of choice to predict potential distributions of invasive species. Although land‐use is a key driver of alien species invasions, it is often assumed that land‐use is constant in time. Here we combine historical and present day information, to evaluate whether land‐use changes could explain the dynamic of invasion of the American bullfrog Rana catesbeiana (=Lithobathes catesbeianus) in Northern Italy, from the 1950s to present‐day. We used maxent to build habitat suitability models, on the basis of past (1960s, 1980s) and present‐day data on land‐uses and species distribution. For example, we used models built using the 1960s data to predict distribution in the 1980s, and so on. Furthermore, we used land‐use scenarios to project suitability in the future. Habitat suitability models predicted well the spread of bullfrogs in the subsequent temporal step. Models considering land‐use changes predicted invasion dynamics better than models assuming constant land‐use over the last 50 years. Scenarios of future land‐use suggest that suitability will remain similar in the next years. Habitat suitability models can help to understand and predict the dynamics of invasions; however, land‐use is not constant in time: land‐use modifications can strongly affect invasions; furthermore, both land management and the suitability of a given land‐use class may vary in time. An integration of land‐use changes in studies of biological invasions can help to improve management strategies.     

Comparative ecology of the six albatross species breeding on the Crozet Islands

Six species of albatrosses breed sympatrically at the Crozet Islands. The population size, masses and measurements of adults, nesting habitats and coloniality, laying, hatching and fledging dates, duration of incubation and brooding shifts are compared. The growth of chicks, diets and feeding methods of the six species are reviewed. Their distribution in the south Indian Ocean is described in relation to the feeding frequency of chicks. Various aspects of ecological isolation among the species are analysed. Overlaps exist in the timing of breeding in the small albatrosses and to a lesser extent in their diet. Differences in the foraging zones at sea appear to be the most important factor in reducing interspecific competition. It is shown that the effective division of resources results from a relative scarcity of resources around the Crozet Islands. Finally the close interrelationship between foraging strategy, breeding biology, diet, chick growth and breeding frequency in the small albatrosses is demonstrated.     

CONSÉQUENCES DE L'ALIMENTATION ARTIFICIELLE SUR LE DÉVELOPPEMENT LARVAIRE DE LA TEIGNE DU POIREAU,ACROLEPIOPSIS ASSECTELLA

L'importance des pressions de sélection au cours des premières générations, dans des élevages en alimentation artificielle, est mise en évidence par l'étude de souches d 'Acrolepiopsis assectella Zeller soumises à des changements de régime alimentaire. l'évolution du taux de survie et de la durée du développement des larves a été suivie pendant les premières générations après le changement, et ultérieurement contrôlée au cours de plusieurs années d'élevage dans les mêmes conditions. Le taux de survie semble atteindre assez rapidement un équilibre, dont le niveau n'est pas indépendant de l'aliment consommé, tandis qu la durée du développement larvaire devient identique pour toutes les souches dès la quatrième génération. Ces phénomènes semblent correspondre à une adaptation des insectes à leurs conditions d'élevage, qui provoquent une sélection dans les populations d'origine.     

Changes of DNA Ligases in Chick Neural Retina as a Function of Age

In the course of chick neural retina development, several forms of DNA ligase have been found. During embryonic life the major DNA ligase activity that is found at seven days is form I (8.2 S) which gradually decreases and disappears by 14 days after incubation, whereas form II (6.2 S) increases to reach a maximum at the time of hatching. Form II then decreases reaching a constant level by Day 7 and from that time new slow sedimenting forms also appear (forms III and IV). Form III (2 S) is first detectable at seven days and increases up to 90 days, whereas form IV (3 S) is the only form detected in the 17- and 18-month-old and also in the 5-year-old birds. These four forms display different elution patterns on phosphocellulose column chromatography. They also differ in their thermal stability and sensitivity towards N-ethylmaleimide.     

A survey of elephants (Loxodonta africana) in the Kahuzi-Biega National Park lowland sector and adjacent forest in eastern Zaire

There has been considerable uncertainty about the abundance estimation of Loxodonta africana within tropical lowland moist forests in Zaire. We surveyed a 15,570 km² area within the forests of eastern Zaire using transect sampling methods and estimated the elephant population to be 3720 (range 2300–5000) individuals. Dung pile densities were significantly different between adjacent settlement, deep forest, and deep forest core strata, with the most remote area harbouring the highest density. Evidence of elephant poaching was encountered throughout the survey area suggesting that elephant populations continue to be at severe risk.     

Effects of Blue Light on the Vertical Colonization of Space by White Clover and their Consequences for Dry Matter Distribution

The morphology of white clover is very sensitive to the lightenvironment, especially to the ratio of red:far-red light andto photon irradiance. However, less is known about the effectsof blue light on clover morphogenesis. Cuttings of white cloverwere grown for 56 d in two controlled chambers receiving lightwith similar photosynthetic efficiency and phytochrome photoequilibriumstate but different levels of blue light: some plants were grownunder orange light (very low blue light, 0.02 µmol m^-2s^-1)or under white light containing blue light (83 µmol m^-2s^-1).Other plants were switched from white light to orange lightorvice versa,after 30 d. The absence of blue light modifiedthe growth habit of clover and raised the laminae in the upperlayer of the canopy by increasing petiole length, and petioleangle from the horizontal, and by raising stolons above theground surface. Moreover, the absence of blue light had no effecton total leaf area and total dry weight per plant, but increasedthe leaf area and biomass of petioles of the main axis. Largerpetioles and laminae were associated with the allocation ofmore dry weight to the petiole at the same petiole thicknessbut with thinner laminae. These results indicate that a decreasein blue light is involved in the perception of, and adaptationto, shading by the plant.Copyright 1997 Annals of Botany Company Biomass allocation; blue light; growth habit; leaf area; light quality; photomorphogenesis; Trifolium repensL.; white clover     

Genome size evolution and polyploidy in the Daphnia pulex complex (Cladocera: Daphniidae)

Genome size was estimated in 49 clones of the Daphnia pulex complex from temperate and subarctic locations using flow cytometry and microsatellite DNA analyses. Significant genome size differences were found in diploid species belonging to the two genetically distinct groups (the pulicaria and the tenebrosa groups), with clones from the tenebrosa group having genome sizes 22% larger than those in the pulicaria group. Combined flow cytometry and microsatellite DNA analyses revealed that nearly all polyploid clones in the D. pulex complex are triploid and not tetraploid, as was previously suggested. Sequencing analyses of the ND5 gene to position clones in their respective clades within the D. pulex complex have uncovered three triploid clones of Daphnia middendorffiana with a D. pulex maternal parent. This result was unexpected because Daphnia pulicaria has always been identified as the maternal parent of these hybrid polyploid clones. Triploid clones likely owe their origins to interactions between sexual and asexual populations. Further interactions in the tenebrosa group have generated tetraploid clones but these events have been rare.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 68–79.     

Sex pheromones and trail‐following pheromone in the basal termites Zootermopsis nevadensis (Hagen) and Z. angusticollis (Hagen) (Isoptera: Termopsidae: Termopsinae)

In the context of an evolutionary study of the chemical communication in termites, sex pheromones and trail‐following pheromones were investigated in two Termopsidae, Zootermopsis nevadensis and Z. angusticollis. In these species, in which the presence of sex‐specific pheromones has been demonstrated previously, the chemical structure of the female sex pheromone has now been identified as (5E)‐2,6,10‐trimethylundeca‐5,9‐dienal and the male sex pheromone as (+)‐ or (?)‐syn‐4,6‐dimethyldodecanal. The amount of sex pheromone was estimated at 5–10 ng per individual in females and 2–5 ng in males. Because these two sympatric species do not differ in their pheromonal chemical composition, reproductive isolation is probably mediated chiefly by differences in dispersal flight chronology. The trail‐following pheromone was shown to be composed of the same compound as the male sex pheromone, that is syn‐4,6‐dimethyldodecanal. The compound syn‐4,6‐dimethyldodecanal was 10 times more active than the racemic (+/?)‐syn + (+/?)‐anti‐4,6‐dimethyldodecanal in eliciting trail‐following. The amount of syn‐4,6‐dimethyldodecanal was estimated at 0.1–0.5 ng per pseudergate. Regarding the phylogenetic aspects, the nature of the female sex pheromone of Zootermopsis is structurally akin to the trail‐following pheromone of Mastotermes darwiniensis of Mastotermitidae and Porotermes adamsoni and Stolotermes victoriensis of Termopsidae. Interestingly, the nature of the trail‐following pheromone of the Termopsinae Zootermopsis is clearly different from that of the Porotermitinae P. adamsoni and the Stolotermitinae S. victoriensis, which mirrors recent molecular data on the paraphyly of Termopsidae. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 519–530.     

Holothurians (Echinodermata) from Marion and Prince Edward Islands: new and little-known species

Two new species Mesothuria edwardensis sp.n. and Paradota marionensis sp.n., and four little-known species Cucumaria kerguelensis Théel, 1886, Cladodactyla crocea croceoides (Vaney, 1908), Psolidium incertum (Théel, 1886) and Synallactes challengeri (Théel, 1886) of holothurians are described from Marion and Prince Edward Islands.