Treeline shifts in the Ural mountains affect soil organic matter dynamics

Historical photographs document that during the last century, forests have expanded upwards by 60–80 m into former tundra of the pristine Ural mountains. We assessed how the shift of the high‐altitude treeline ecotone might affect soil organic matter (SOM) dynamics. On the gentle slopes of Mali Iremel in the Southern Urals, we (1) determined the differences in SOM stocks and properties from the tundra at 1360 m above sea level (a.s.l.) to the subalpine forest at 1260 m a.s.l., and (2) measured carbon (C) and nitrogen (N) mineralization from tundra and forest soils at 7 and 20 °C in a 6‐month incubation experiment. C stocks of organic layers were 3.6±0.3 kg C m^?2 in the tundra and 1.9±0.2 kg C m^?2 in the forest. Mineral soils down to the bedrock stored significantly more C in the forest, and thus, total soil C stocks were slightly but insignificantly greater in the forest (+3 kg C m^?2). Assuming a space for time approach based on tree ages suggests that the soil C sink due to the forest expansion during the last century was at most 30 g C m^?2 yr^?1. Diffuse reflective infrared spectroscopy and scanning calorimetry revealed that SOM under forest was less humified in both organic and mineral horizons and, therefore, contained more available substrate. Consistent with this result, C mineralization rates of organic layers and A horizons of the forest were two to four times greater than those of tundra soils. This difference was similar in magnitude to the effect of increasing the incubation temperature from 7 to 20 °C. Hence, indirect climate change effects through an upward expansion of forests can be much larger than direct warming effects (Δ0.3 K across the treeline). Net N mineralization was 2.5 to six times greater in forest than in tundra soils, suggesting that an advancing treeline likely increases N availability. This may provide a nutritional basis for the fivefold increase in plant biomass and a tripling in productivity from the tundra to the forest. In summary, our results suggest that an upward expansion of forest has small net effects on C storage in soils but leads to changes in SOM quality, accelerates C cycling and increases net N mineralization, which in turn might stimulate plant growth and thus C sequestration in tree biomass.     

Ancient DNA sequences point to a large loss of mitochondrial genetic diversity in the saiga antelope (Saiga tatarica) since the Pleistocene

Prior to the Holocene, the range of the saiga antelope (Saiga tatarica) spanned from France to the Northwest Territories of Canada. Although its distribution subsequently contracted to the steppes of Central Asia, historical records indicate that it remained extremely abundant until the end of the Soviet Union, after which its populations were reduced by over 95%. We have analysed the mitochondrial control region sequence variation of 27 ancient and 38 modern specimens, to assay how the species’ genetic diversity has changed since the Pleistocene. Phylogenetic analyses reveal the existence of two well‐supported, and clearly distinct, clades of saiga. The first, spanning a time range from >49 500 ¹⁴C ybp to the present, comprises all the modern specimens and ancient samples from the Northern Urals, Middle Urals and Northeast Yakutia. The second clade is exclusive to the Northern Urals and includes samples dating from between 40 400 to 10 250 ¹⁴C ybp. Current genetic diversity is much lower than that present during the Pleistocene, an observation that data modelling using serial coalescent indicates cannot be explained by genetic drift in a population of constant size. Approximate Bayesian Computation analyses show the observed data is more compatible with a drastic population size reduction (c. 66–77%) following either a demographic bottleneck in the course of the Holocene or late Pleistocene, or a geographic fragmentation (followed by local extinction of one subpopulation) at the Holocene/Pleistocene transition.     

Importance of colour in the reaction of passerine predators to aposematic prey: experiments with mutants of Pyrrhocoris apterus (Heteroptera)

Persistent questions concerning the warning coloration of unpalatable insects address whether the bright aposematic colour itself or its combination with a species-specific dark pattern is the key factor in their protection against insectivorous birds, and how chromatic polymorphism originates and is maintained in aposematics. In the present study, these questions were tested experimentally, using the birds Parus major , Parus caeruleus , Erithacus rubecula , and Sylvia atricapilla as predators, and chromatically polymorphic firebug Pyrrhocoris apterus : red wild form, white, yellow, and orange mutants (all four of them with the same black melanin pattern, the mutants differing in colour of pteridine pigments only) and the nonaposematic brown-painted wild form as prey. The results show that a specific colour is essential for the birds to recognize the specific aposematic prey; the melanin pattern is not sufficient. White mutants were no better protected than nonaposematic firebugs; red wild-type and orange mutants were equally well protected against all bird species; and the reaction of birds to yellow mutants was species-specific. An evolutionary scenario of 'recurrent recessive mutations' is formulated to explain the origin of colour polymorphism in some aposematics.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 88 , 143–153.     

A eutherian mammal from the Early Cretaceous of Russia and biostratigraphy of the Asian Early Cretaceous vertebrate assemblages

Prokennalestes abramovi n.sp. is described based on M2 from the upper Barremian-middle Aptian (Early Cretaceous) Mogoito locality in Transbaikalia, Russia. It differs from the Mongolian species of Prokennalestes (Khoboor, early Albian) by a combination of one primitive character (steeper and shorter lingual slopes of the paracone and metacone), one more derived character (larger size), and some characters of uncertain polarity (small preparastyle, lack of labial cuspules along the ectoflexus). P. abramovi n.sp. is the oldest eutherian mammal so far described, and its discovery extends the known geological range of Eutheria by 10-15 Ma. The Tsagantsabian land-vertebrate biochron can be defined by a dominance of sinemyid turtles; the Khukhtekian by a dominance of macrobaenids.     

Cranial anatomy of the stem salamander Kokartus honorarius (Amphibia: Caudata) from the Middle Jurassic of Kyrgyzstan

The cranial anatomy of the stem salamander Kokartus honorarius, from the Middle Jurassic of Kyrgyzstan, is redescribed in detail on the basis of all available material using conventional methods and high‐resolution computed microtomography. In contrast to previous interpretations, the skull is characterized by posteriorly positioned external nostrils, the presence of an internarial fenestra between the premaxillae, the maxillae are not shortened, the overlapping of the frontal by the nasal and the parietal by the frontal, a dentate vomer, a dentate pterygoid with a long, strongly arcuate and anteromedially orientated anterior process, the absence of a fontanelle between frontals and pineal pit on the ventral surface of the frontals, and an inferred unique attachment of the adductor mandibulae internus to the lateral border and ventral ridge of the frontals and parietals. Kokartus is closely related to Karaurus and both these taxa constitute the monophyletic taxon Karauridae, which forms the sister group of crown‐group salamanders (Urodela). Karaurids were neotenic forms and neoteny was probably the ancestral life history strategy of salamanders. The morphological analysis of Kokartus supports the current phylogenetic hypothesis that Permian amphibamids (including branchiosaurids) are the closest relatives of salamanders amongst known non‐lissamphibian temnospondyls. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 161 , 816–838.     

Parental role division predicts avian preen wax cycles

Previous studies have shown that preen wax composition in some sandpipers shifts from the usual monoesters to diesters during the breeding season, possibly to reduce the ability of mammalian predators to find nests using olfactory cues. To investigate further the relationship between incubation and wax secretion, we examined seven sandpiper species with different incubation patterns (species in which both sexes incubate, in which only males incubate and in which only females incubate). During the breeding period, diester preen wax was secreted almost exclusively by the incubating sex in species with uniparental incubation, and by both sexes in species with biparental incubation. These findings suggest that diester preen waxes have a function that is directly related to incubation. Unexpectedly, in female-incubating Curlew Sandpiper Calidris ferruginea and Buff-breasted Sandpiper Tryngites subruficollis , some males also secreted diester preen waxes during the breeding period. This suggests that some males may in fact incubate, that these waxes may be a remnant from their evolutionary past when both sexes incubated, or that males need to be olfactorally cryptic because they are involved in the making of nest scrapes. The seasonal pattern of preen wax composition was also studied in captive male, female and female-mimicking male ('faeder') Ruff Philomachus pugnax . Captive female Ruff changed preen wax composition from monoesters to diesters in the spring despite the fact that no incubation took place. This suggests that circannual rhythms rather than actual incubation behaviour may trigger the shift to diester waxes. All captive male Ruff, including the faeders, continued to secrete monoesters, supporting the hypothesis that only the incubating sex secretes diesters.     

Identification of Microtubule-Organizing Centers in Interphase Melanophores of Xenopus Laevis Larvae In Vivo

The morphological characteristics of microtubule-organizing centers (MTOCs) in dermal interphase melanophores of Xenopus laevis larvae in vivo at 51-53 stages of development has been studied using immuno-stained semi-thick sections by fluorescent microscopy combined with computer image analysis. Computer image analysis of melanophores with aggregated and dispersed pigment granules, stained with the antibodies against the centrosome-specific component (CTR210) and tubulin, has revealed the presence of one main focus of microtubule convergence in the cell body, which coincides with the localization of the centrosome-specific antigen. An electron microscopy of those melanophores has shown that aggregation or dispersion of melanosomes is accompanied by changes in the morphological arrangement of the MTOC/centrosome. The centrosome in melanophores with dispersed pigment exhibits a conventional organization, and their melanosomes are situated in an immediate vicinity of the centrioles. In melanophores with aggregated pigment, MTOC is characterized by a three-zonal organization: the centrosome with centrioles, the centrosphere, and an outlying radial arrangement of microtubules and their associated inclusions. The centrosome in interphase melanophores is presumed to contain a pair of centrioles or numerous centrioles. Because of an inability of detecting additional MTOCs, it has been considered that an active MTOC in interphase melanophores of X. laevis is the centrosome. We assume that remaining intact microtubules in the cytoplasmic processes of mitotic melanophores (Rubina et al., 1999) derive either from the aster or the centrosome active at the interphase.     

Reactions of passerine birds to aposematic and non-aposematic firebugs (Pyrrhocoris apterus ; Heteroptera)

In spite of the existence of many experimental studies on the function of warning coloration in insects, little is known about the universality of reactions of different predators towards a particular warning signal. Reactions of nine passerine bird species, namely Parus major , Parus caeruleus , Aegithalos caudatus , Erithacus rubecula , Turdus merula , Sylvia atricapilla , Fringilla coelebs , Carduelis chloris and Emberiza citrinella , to the firebug Pyrrhocoris apterus wildtype (brachypterous adults) and its artificially obtained (painted) brown non-aposematic variant were compared. Most insectivorous birds (great tits, blue tits, robins and blackcaps) distinguished between aposematic and non-aposematic bugs, attacking the former less often. Partly granivorous buntings and finches did not distinguish between them, and attacked both variants equally. As all the birds were caught in the wild, the results can be interpreted in terms of the presence of a higher proportion of experienced individuals among insectivorous than among omnivorous species. Two insectivorous species differed from others. The heaviest blackbird attacked and killed aposematic as well as non-aposematic firebugs, and, in contrast, the lightest long-tailed tit avoided both variants. © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 78 , 517–525.     

O-Methylation of L-dopa in Melanin Metabolism and the Presence of Catechol-O-Methyltransferase in Melanocytes

O-Methylation of L-dopa was investigated as a possible regulatory mechanism in melanin metabolism. The methylation product of L-dopa, 3-O-methoxytvrosine was detected in extracts of cultured human melanocytes. The enzyme catechol-O-methyltransferase is responsible for this O-methylation and that of the dihydroxyindolic intermediates of melanogenesis. The enzyme is present in melanocytes in its soluble and membrane-bound isoforms. Immuno-electron microscopy suggests the presence of the membrane-bound enzyme in the endoplasmic reticulum. This localization may indicate a role of catechol-O-methyltransferase in protecting the melanocyte against reactive dihydroxyphenolic intermediates of melanogenesis leaking from the melanogenic compartments. On the other hand, the O-methylation of L-dopa may serve as a regulatory point in melanogenesis during early stage of tyrosinase processing in the endoplasmic reticulum.