Alternative explanations for rising dissolved organic carbon export from organic soils

Since 1988, there has been, on average, a 91% increase in dissolved organic carbon (DOC) concentrations of UK lakes and streams in the Acid Waters Monitoring Network (AWMN). Similar DOC increases have been observed in surface waters across much of Europe and North America. Much of the debate about the causes of rising DOC has, as in other studies relating to the carbon cycle, focused on factors related to climate change. Data from our peat‐core experiments support an influence of climate on DOC, notably an increase in production with temperature under aerobic, and to a lesser extent anaerobic, conditions. However, we argue that climatic factors may not be the dominant drivers of DOC change. DOC solubility is suppressed by high soil water acidity and ionic strength, both of which have decreased as a result of declining sulphur deposition since the 1980s, augmented during the 1990s in the United Kingdom by a cyclical decline in sea‐salt deposition. Our observational and experimental data demonstrate a clear, inverse and quantitatively important link between DOC and sulphate concentrations in soil solution. Statistical analysis of 11 AWMN lakes suggests that rising temperature, declining sulphur deposition and changing sea‐salt loading can account for the majority of the observed DOC trend. This combination of evidence points to the changing chemical composition of atmospheric deposition, particularly the substantial reduction in anthropogenic sulphur emissions during the last 20 years, as a key cause of rising DOC. The implications of rising DOC export for the carbon cycle will be very different if linked primarily to decreasing acid deposition, rather than to changes in climate, suggesting that these systems may be recovering rather than destabilising.     

Linkage disequilibrium and natural selection for mimicry in the Batesian mimic Hypolimnas misippus (L.) (Lepidoptera: Nymphalidae) in the Afrotropics

On two occasions, on opposite sides of the African continent (Cape Coast, Ghana, and Dar es Salaam, Tanzania), high adult population densities in the polymorphic butterfly Hypolimnas misippus (a presumed mimic of Danaus chrysippus) were followed by linkage disequilibrium in combinations of fore‐ and hindwing colour patterns. On both occasions, disequilibrium was caused by significant changes in morph frequencies favouring rarer and more mimetic forms. Recaptures were too few for analysis at Dar, although the changes there took place within a single generation and must have been the result of differential survival. Recapture rate data and survival rate estimates at Cape Coast support the hypothesis that selective predation was responsible, as does the observation of synchronous linkage disequilibrium at Dar in the model D. chrysippus, indicating parasitic mimicry. There was clear selection for the perfection of mimicry for forewings at Dar and for hindwings at Cape Coast. Disequilibrium is also reported for two other sites, Legon (Ghana) and Boksburg (South Africa) and, in all four sites, it was associated with an increase in the most mimetic forms. New chemical evidence is presented to support the contention that D. chrysippus is a defended model. Although all the evidence leads to the conclusion that H. misippus is a Batesian mimic of D. chrysippus, many questions remain, particularly with regard to the identity of predators, the episodic nature of selective predation events, and their apparent lack of lasting and significant impact on overall gene frequencies. We conclude that H. misippus presents both challenges and opportunities for studies on mimicry, and we suggest that linkage disequilibrium can be a useful generic indicator for Gestalt predation on polymorphic prey. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 180–194.     

Comparative Immunology of Selected Wild Types,Varieties and Mutants of Chlamydomonas*

SYNOPSIS. Rabbit antisera to strains of different mating types of Chlamydomonas moewusii and to one strain of C. eugametos were tested against strains of C. reinhardti, C. eugametos, and C. moewussi, and against strains of 2 varieties and 6 mutant types of C. moewusii. Technics of double diffusion, absorption, and immunoelectrophoresis revealed marked serological differences between the sexually incompatible, distinct genetic species C. moewusii and C. reinhardti. Less distinct serological differences were resolved between C. moewusii and the so-called “species”C. eugametos, which is sexually compatible with the former, thus reconfirming the conspecificity between the 2 strains as suggested by Gowans. Marked serological differences were noted between C. moewusii and 2 of its varieties (C. moewusii var. tenuichloris and C. moewusii var. rotunda) which constitute 2 additional genetic species because of sexual incompatibility between themselves and with C. moewusii. Wild types and certain mutants of C. moewusii were compared serologically and could be distinguished on this basis. Strains of different mating types as well as certain mutant strains (e.g., paralyzed flagella, flagella-less, twins and monsters) could be differentiated serologically altho differences were often very subtle. Some antigens were common to organisms tested.     

Animal Migrations: Endangered Phenomena

Current conservation research focuses on diminishing speciesdiversity, minimal viable populations, and on the successivedemise of habitats and populations that leads species to extinction.In this paper we utilize the monarch butterfly's remarkablemigration and overwintering biology as a paradigm of a new conservationtheme: endangered phenomenon. An endangered phenomenon is aspectacular aspect of the life history of an animal or plantspecies involving a large number of individuals that is threatenedwith impoverishment or demise; the species per se need not bein peril, rather, the phenomenon it exhibits is at stake. Weenvision the near future with increasing numbers of speciesreduced in range and so constrained in numbers that they canno longer exhibit these characteristic spectacles.     

The Cochlear Duct of Lizards and Snakes

The gross morphology of the cochlear ducts of approximatelyhalf (150) of the living genera of lizards and a third (130)of the living genera of snakes have been studied. The differencesin the structure of the cochlear duct are related to both theacoustical capacities and the taxonomic relationships of certainlizards and snakes. The cochlear duct of lizards consists offairly well joined lagenar and limbic portions. By contrast,the cochlear duct of snakes consists of a lagenar sac somewhatconstricted from the limbus. Each family of lizards has a morphologicallycharacteristic cochlear duct, but taxonomic relationships areindicated by certain anatomical similarities. The cochlear ductof snakes is more primitive than that of lizards, and, unlikelizards, does not exhibit marked specializations of its variousparts. Differences in morphology of the cochlear duct in snakesare much more related to habitat than family. The limbus andpapilla basilaris of snakes regardless of family, are most elongatedin bin rowing species, are only moderately elongated or ovoidin terrestrial species, and are small or reduced in certainarboreal and aquatic species.     

Importance of consumptive and non-consumptive prey mortality in a coupled predator–prey system

1. Laboratory experiments were completed to identify the mechanisms by which the predatory flatworm, Dugesia tigrina , imposes mortality on its Aedes aegypti and Daphnia magna prey. Feeding trials were completed in glass microcosms which contained one of three – nine densities of small or large individuals of each prey species.
2. Mortality by Dugesia on small and large Aedes followed a type II functional response, whereas the mortality of Daphnia resembled a type III functional response. Prey mortality imposed by Dugesia consisted of consumptive and non-consumptive elements. Non-consumptive mortality occurred when prey individuals trapped in mucus trails subsequently died but were not ingested.
3. Additional experiments were conducted to quantify consumptive (capture followed by ingestion) and non-consumptive mortality (death not followed by ingestion).
4. Consumptive mortality followed a type II functional response for small and large individuals of both prey species, whereas non-consumptive mortality increased with prey density, although the relationships differed with prey species and size. The non-consumptive mortality of large Daphnia increased at an accelerating rate with prey density and exceeded consumptive mortality at intermediate prey abundances. In contrast, non-consumptive mortality of small Aedes and small Daphnia was lower than consumptive mortality and either increased with prey density at a decelerating (small Aedes ) or accelerating (small Daphnia ) rate.
5. These results suggest that the importance of consumptive and non-consumptive mortality to total prey mortality needs to be considered when modelling predator–prey dynamics.