Chromosomal evolution of the house mouse, Mus musculus domesticus, in the Aeolian Archipelago (Sicily, Italy)

We describe the chromosomal evolution of the metacentric populations of the house mouse, Mus musculus domesticus , which constitute the Robertsonian System of Aeolian Islands (Sicily, Italy). Eighty-nine specimens from all the seven islands that form the Archipelago were cytogenetically examined. The analysis shows the presence of 4 Rb races with a large number of shared metacentric chromosomes: 2 n  = 36 on Panarea, 2 n  = 34 on Alicudi, 2 n  = 26 on Lipari and Stromboli, and a different 2 n  = 26 race on Vulcano. On Salina and Filicudi, the standard karyotype was found. Polymorphism was only found in a population on Panarea Island and this population shares no metacentrics with the other races. The distribution of metacentrics among the races and the comparison between the Aeolian metacentrics and those found in the 97 previously documented metacentric populations allows us to formulate a hypothesis of chromosomal evolution for the Aeolian Robertsonian system. Six of the twelve metacentric chromosomes found in the Aeolian Islands come from localities outside the archipelago. The evolutionary model highlights how the chromosomal races originated inside the Archipelago and involve several factors, such as formation in situ of metacentrics, zonal raciation and, whole arm reciprocal translocation. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 194–202.     

Nocturnal resource defence in aphid‐tending ants of northern Patagonia

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Effect of selective planktivory by fry of Rhamdia sapo (Pimelodidae: Pisces) on zooplankton community structure

SUMMARY.

• 1 The direct and indirect effects of predation by larval fish (Rhamdia sapo) on zooplankton in rearing tanks are analysed. Rhamdia sapo larvae showed an unusual species-selectivity for Acanthocyclops robustus, the main invertebrate predator present.
• 2 Acanthocyclops robustus populations were markedly reduced, presumably as a direct consequence of species-selective removal. Other zooplanktonic prey were not significantly affected by R. sapo predation.
• 3 Rotifers increased in tanks with fish, but this was not related to herbivorous crustacean variables (biomass, mean weight, abundance and species composition). On the contrary, rotifer biomass was negatively correlated with some A. robustus variables (biomass and mean weight of adults + copepodites and nauplii biomass). Thus, the rotifer increase appears to be an indirect effect of predation on A. robustus by R. sapo larvae.

     

Germination of seeds in Jussiaea suffruticosa

Seeds of Jussiaea suffruticosa reach high germination percentagesonly when exposed to long periods of continuous illumination.The light reaction may be repeatedly reversed by short exposuresto red and far red light, thus being mediated by the phytochromesystem. Seeds also germinate at high percentages if exposedto various cycles of 1 hr light and 24 hr of darkness at 20°C.If the temperature in the periods of darkness is raised up to30°C or lowered to 10°C the promotive effect of lightis inhibited. High temperatures (35°C) during imbibitionhave a promotive effect, whereas a pure O₂ atmosphere decreasesthe response to light. KNO₃ and kinetin enhance the responseto light but do not provoke germination in the dark. Only ifseed coats are punctured or removed does germination in thedark occur. (Received January 14, 1969; )     

Ecological and environmental footprint of 50 years of agricultural expansion in Argentina

Agriculture expanded during the last 50 years from the Pampas to NW Argentina at the expense of natural forests and rangelands. In parallel, productivity was boosted through the increasing application of external inputs, modern technology and management practices. This study evaluated the impact of agricultural expansion between 1960 and 2005 by assessing the implications of land use, technology and management changes on (i) carbon (C), nitrogen (N) and phosphorous (P) stocks in soil and biomass, (ii) energy, C, N, P and water fluxes and (iii) water pollution, soil erosion, habitat intervention and greenhouse gas (GHG) emissions (impacts). Based on different data sources, these issues were assessed over～1.5 million km² (63% of Argentina), involving 399 political districts during three representative periods: 1956–1960, 1986–1990 and 2001–2005. The ecological and environmental performance of 1197 farming system types was evaluated through the AgroEcoIndex model, which quantified the stocks, fluxes and impacts mentioned above. Cultivation of natural ecosystems and farming intensification caused a noticeable increase of productivity, a strengthening of energy flux, an opening of matter cycles (C, N, P) and a negative impact on habitats and GHGs emission. However, due to the improved tillage practices and the application of less aggressive pesticides, erosion and pollution risk are today lower than those of the mid‐20th century. The consistency of some assumptions and results were checked through uncertainty analysis. Comparing our results with international figures, some impacts (e.g. soil erosion, nutrient balance, energy use) were less significant than those recorded in intensive‐farming countries like China, Japan, New Zealand, USA, or those of Western Europe, showing that farmers in Argentina developed the capacity to produce under relatively low‐input/low‐impact schemes during the last decades. [Correction added after online publication 4 October 2010: In the first sentence of the Abstract, NE was corrected to NW.]     

Latitudinal patterns and regionalization of plant diversity along a 4270‐km gradient in continental Chile

According to the global latitudinal diversity gradient, a decrease in animal and plant species richness exists from the tropics towards higher latitudes. The aim of this study was to describe the latitudinal distribution patterns of Chilean continental flora and delineate biogeographic regions along a 4270‐km north–south gradient. We reviewed plant lists for each of the 39 parallels of continental Chile to build a database of the geographical distribution of vascular plant species comprising 184 families, 957 genera and 3787 species, which corresponded to 100%, 94.9% and 74.2% of the richness previously defined for Chile, respectively. Using this latitudinal presence–absence species matrix, we identified areas with high plant richness and endemism and performed a Cluster analysis using Jaccard index to delineate biogeographic regions. This study found that richness at family, genus and species levels follow a unimodal 4270‐km latitudinal distribution curve, with a concentration of richness in central Chile (31–42°S). The 37th parallel south (central Chile) presented the highest richness for all taxonomic levels and in specific zones the endemism (22–37°S) was especially high. This unimodal pattern contrasts the global latitudinal diversity gradient shown by other studies in the Northern hemisphere. Seven floristic regions were identified in this latitudinal gradient: tropical (18–22°S), north Mediterranean (23–28°S), central Mediterranean (29–32°S), south Mediterranean (33–37°S), north temperate (38–42°S), south temperate (43–52°S) and Austral (53–56°S). This regionalization coincides with previous bioclimatic classifications and illustrates the high heterogeneity of the biodiversity in Chile and the need for a reconsideration of governmental conservation strategies to protect this diversity throughout Chile.     

Pupal colour dimorphism in a desert swallowtail (Lepidoptera: Papilionidae) is driven by changes in food availability,not photoperiod

1. The swallowtail butterfly Battus polydamas archidamas Boisduval, 1936, exhibits polyphenism for pupal coloration (green and brown). It is distributed across arid regions with winter rains and is monophagous on Aristolochia plants, which emerge after the winter rains and dry out the during summer. Thus, day length does not covary positively with host plant productivity. It was hypothesised that pupal colour was driven by food availability, not photoperiod. The benefits of pupal coloration matching the colour of pupation sites in terms of field survival were also investigated to evaluate the adaptive value of pupa colour. 2. Larvae were reared under a factorial array of two photoperiods (LD 10:14 h and LD 14:10 h) and two food availability regimes (leaves ad libitum and available every other day) to assess the frequency of green and brown pupae. Field survival of green and brown pupae was quantified in three commonly used habitats that differ in background coloration (cacti, rocks and shrubs). 3. Food availability determined pupal colour. Larvae in the ad libitum regime resulted mostly in green pupae, while those with restricted food were mostly brown. In contrast, photoperiod did not influence pupal colour. Survival probability of pupae placed on cacti was higher than those placed on rocks and shrubs, and the lowest predation risk across habitats was for green pupae on cacti. 4. Food availability plays a major role in the seasonal polyphenism for pupal colour of specialist butterflies inhabiting arid environments with winter rains.     

14C-Translocation in Kalanchoe pinnata at two Different Stages of Development

Mayoral, M. L. and Medina, E. 1985. ¹⁴C-translocation in Kalanchoepinnata at two different stages of development.—J. exp.Bot. 36: 1405–1413 Translocation of ¹⁴C-compounds from mature leaves was measuredin plants of Kalanchoe pinnata to determine the interactionbetween plant age and CAM phase when CO² is taken up. Matureleaves of 4 and 12 month old plants were fed with ¹⁴CO² eitherduring CAM phase 1 (midnight) or at the beginning of CAM phase4 (early afternoon). Export of ¹⁴C activity from source leaves,and distribution of ¹⁴C activity in soluble and insoluble compoundswas measured both in source leaves and sink organs. In 4 monthold plants 4 d were needed to export 76% of total ¹⁴C activityincorporated during CAM phase 1, while leaves labelled at thebeginning of CAM phase 4 exported 44% of total ¹⁴C activityafter 4 h, and 80% after 24 h. In both cases the major fractionof total radioactivity translocated was found in the roots inthe form of neutral sugars. Differences in translocation patternsare due to distribution of ¹⁴C in the source leaves, 96 % of¹⁴C taken up during CAM phase 1 is found in the insoluble fractionat the end of the subsequent phase 3, while 93 % of total radioactivitytaken up at the beginning of phase 4 is found in the solublefraction at the end of this phase. In 12 month old plants labelledduring phase 1 very little translocation could be detected atthe end of phase 3, while only 20% of total radioactivity wastranslocated from leaves labelled during phase 4 and measured4 h later. ¹⁴C activity in the older leaves had a similar distributionin soluble and insoluble fractions as the one determined inthe younger plants. Ability to translocate carbon compoundsfrom source leaves during phase 3 was shown by loading matureleaves at dawn with ¹⁴C-sucrose. Here again, mature leaves ofyounger plants showed faster translocation of radioactivitythan those of older plants Key words: Kalanchoe, crassulacean acid metabolism, translocation, sink, source relationships     

Population genetics and the conservation status of the threatened Iberian steppe grass Puccinellia pungens (Pau) Paunero (Poaceae)

Puccinellia pungens (Pau) Paunero is a narrowly endemic grass found in two continental saline lagoons of north-eastern Spain. This rare plant has been classified as 'at risk of extinction' in several national and European catalogues of endangered species. Recent demographic studies indicate that population sizes greatly exceed several million individuals, challenging that threat category. Our genetic analysis, based on allozymes, has shown that in spite of the large population sizes, very low levels of genetic variation were found in P. pungens . Genetic variation was similar in most populations, but the largest, Gallocanta lagoon as a whole, had less variation (35% polymorphic loci, 1.4 alleles/locus, H _T = 0.038) than the more restricted Royuela range (45% polymorphic loci, 1.5 alleles/locus, H _T = 0.056), suggesting a recent population expansion of the Gallocanta populations from few founder lines. The low genetic distances among populations also suggest a recent divergence. The low genetic variation observed cannot be explained fully by eventual clonal spread and rare seedling establishment in the hypersaline environment. This low variation seems to result from extreme recent population bottlenecks as a consequence of habitat conversion to agricultural fields. In the light of our data, it seems unlikely that reinforcement of populations could increase the genetic diversity of the populations. Hence, conservation efforts should focus on avoiding further habitat loss of this endangered steppe grass species.  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 154 , 269–281.