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.     

Cultural Evolution

SYNOPSIS. Culture is made possible by the existence of mechanismsof learning and communication. Because of it, we can profitfrom the experience and ideas of others. It is convenient toinclude in it tools, technologies, and all culturally transmittedbehaviors. At least from an evolutionary point of view, theyshare common mechanisms. It is also becoming increasingly clearthatanimals share with us potential for cultural adaptation, whichis however much more highlydeveloped in humans, as shown forinstance, by the extension of human brain areas that are involvedin control of hand and phonation organs. To understand how culture evolves one can make resort to modelsthat map reasonably well after the necessary substitutions,into those that havebeen useful in biology. A major differencethat one finds is in mechanisms of transmission, which are muchmore varied in culture than in biology. Parent-child (vertical)transmission is present in both. An "infectious" (horizontal)mechanism is characteristic of cultural transmission, but ispractically absent in the genetic case. Other mechanisms oftransmission are reviewed, along with their evolutionary consequences.The variety of these mechanisms can make culture extremely fastand flexible, and there are the great advantages of culturaladaptation vs. genetic adaptation by natural selection, or vs.physiological adaptations (which are relatively fast but highlyspecific: for instance, tanning under exposure to UV). But culturecan also be extremely conservative. Also, some cultural transmissionmechanisms allow heterogeneitybetween individuals to persist,others tend to make populations extremely homogeneous. The study of culture from an evolutionary point of view is young,but very promising.     

Foraging behaviour and time allocation of chick-rearing Razorbills Alca torda at Græsholmen, central Baltic Sea

A new type of bird-borne data logger, which stores data from flight and depth sensors at pre-set intervals, was used to investigate the foraging pattern and diving behaviour of chick-rearing Razorbills Alca torda breeding on the islet of Græsholmen (central Baltic Sea, Denmark). The instruments recorded all relevant events in the 35 foraging trips accomplished by six different individual birds; a seventh bird, equipped with a direction recorder, provided information on directional preferences exhibited on seven different trips. A foraging trip usually consisted of a number of flights interrupted by a small number of dives probably performed to explore the site for prey availability. True foraging occurred during the last stops in the outbound trip, after which the bird returned to the nest with a single flight or a sequence of a few flights. The duration of nocturnal trips was significantly longer than diurnal trips, possibly due to a preference for the familiar marine environment shown by birds when they are not 'on duty' in the nest. The majority of dives consisted of V-shaped dives in which birds descend to a maximum depth and then start ascending. A clear diurnal variation of the dive depth, which never exceeded 43 m, was recorded. Our results show that the new types of recording devices can be used to answer basic questions about the foraging strategies of marine birds.     

Distribution, density, diet and productivity of the Scops Owl Otus scops in the Italian Alps

The Scops Owl Otus scops is probably the least known European owl. We surveyed Scops Owls in the Trento region (6200 km²) of the central–eastern Italian Alps between 1995 and 2003 and we intensively monitored a subpopulation in a 50‐km² plot between 2000 and 2003. In the whole region, we found 81 territories concentrated in 21, low‐elevation 100‐km² quadrats. Most territories were associated with villages surrounded by extensively managed grassland (79%), arid areas with rocky outcrops and xerophytic vegetation (12%) and/or large urban areas and parks (6%). In the 50‐km² plot, density varied between 52 and 64 territories/100 km² annually. Territories were either solitary or clumped in loose colonies of 2–7 pairs. In contrast to previous studies, most nests used for laying were in holes and cracks of buildings (95%, n = 20). This may have been favoured by thermal and foraging advantages, but also involved some costs, such as predation by domestic cats and collision with cars. Median laying date was 29 May (n = 16) and the mean number of fledged young was 1.37 (n = 30), 1.95 (n = 21) and 2.00 (n = 20) per territorial, breeding and successful pair, respectively. The diet was dominated by grasshoppers of the family Tettigoniidae. Compared to previous studies, this population showed medium to high density and low productivity. The species seems to be dependent on traditional, extensive agro‐pastoralism and the main conservation threats include habitat loss through land abandonment and consequent forest expansion, which are probably best halted through subsidy schemes. From our results and published data, we estimate the population of the Scops Owl in the Italian Alps at 230–500 territories. There is an urgent need for further data on this largely overlooked species, especially from its Mediterranean strongholds.     

Competition for foraging resources and coexistence of two syntopic species of Messor harvester ants in Mediterranean grassland

1. Diet composition of two syntopic species of Messor seed‐harvester ants (M. wasmanni Krausse and M. minor André) was evaluated during different periods over the year (May, July, October), by analysing food type (plant parts and species) and food size (weight, length, width). Morphological traits of foragers (head width and femur length) considered important features promoting diet partitioning were measured. 2. We used two robust randomisation algorithms (RA2 and RA3), adopted in niche overlap studies, to check for random vs non random utilisation of resources at intra‐ and interspecific level for the different periods. 3. Analyses showed high levels of overlap in the diet of the two species and no evidence of interspecific competition during most of the activity season. In particular, there was an aggregated use of resources in summer, whilst niche partitioning and evidence of competition when resources decreased in autumn. Intraspecifically, no evidence of competition was found. 4. Results suggest two different mechanisms for minimising competition: when food resources are abundant (summer), ants collected the same plant species but selected different sizes; when food resource is scarce (autumn), ants foraged on different plants. 5. The importance of different factors (morphological, behavioural, ecological) possibly affecting competition and coexistence are discussed.     

Immune Reactivity following Poly I·Poly C Treatment in Mice

POLYINOSINIC-polycytidylic acid (poly I·poly C) and other synthetic double stranded RNAs are known to be potent inducers of interferon¹, to enhance humoral^2,3 and cellular^3,4 immune responses and to exert a protective action against viral¹ and bacterial infections⁵ and tumours⁶. In addition to these protective effects, however, deleterious characteristics such as pyrogenicity in rabbits⁷ and toxicity in other species⁸ have been described. We show here that poly I·poly C can also produce either enhancement or depression of the immune response to sheep red blood cells (SRBC) depending on the time of injection of the polyribonucleotides in relation to antigenic stimulation.     

Common Bean (Phaseolus vulgaris L.) Mutants Defective in Root Nodule Formation: II GENETIC ANALYSIS

Genetic analysis of crosses between two induced, ineffectivelynodulating mutants of common bean, NOD238 and NOD109, revealedthat their mutated nodulation phenotype is under the controlof the same locus in both mutants. The two mutants also resultedallelic for poor pod fertility, the other trait common to themutants. F₁ plants from crosses with their wild types nodulatedeffectively and had wild type pod fertility. Ineffective nodulationand poor pod fertility traits co-segregated in the F₂generationin which plants with the mutant nodulation and pod fertilityphenotypes represented 12.5% of the total population. Analysisin F₃confirmed that these plants were homozygous for both mutatedcharacters. The results indicated both mutant traits studiedare determined by a single recessive allele, named sym-2, whoseinheritance is negatively affected by its pleiotropic effecton pod fertility determining a deficit of ineffectively nodulatingcombinations. In an allelism test with the non-nodulating mutantof common bean NOD125 it was found that ineffective nodulationis controlled at a different locus and that the two loci arenot linked. Key words: Phaseolus valgaris, nitrogen fixation, nodulation mutants, genetics