Rapid changes in fish community structure and habitat distribution following the precipitation of lake phosphorus with aluminium

1. Fish community structure and habitat distribution of the abundant species roach, perch and ruffe were studied in Lake Nordborg (Denmark) before (August 2006) and after (August 2007) aluminium treatment to reduce internal phosphorus loading. 2. Rapid changes in fish community structure, abundance and habitat distribution occurred following a decline in in‐lake phosphorus concentrations from 280 to 37 μg P L^?1 and an increase in Secchi depth transparency from 1.1 to 1.9 m (August). The proportion of perch in overnight gill net catches increased, whilst roach decreased, and the average weight of all key species increased. 3. The habitat distribution of perch and roach changed from a high proportion in the upper pelagic and littoral zones in 2006, towards enhanced proportions in the deeper pelagic and profundal zone in 2007. The abundance of large‐bodied zooplankton increased and the abundance of benthic invertebrates decreased in the same period, suggesting that the habitat shift was not induced by food limitation. 4. Ruffe shifted from the littoral and upper profundal zones towards the deep profundal zone, likely reflecting an increased predation risk in the littoral zone and better oxygen conditions in the deep profundal. 5. Our results indicate that enhanced risk of predation in the upper pelagic and the littoral zones and perhaps improved oxygen concentrations in the deeper profundal zone at decreasing turbidity are responsible for the observed habitat shift. The results indicate that fish respond rapidly to changes in nutrient state, both in terms of community structure and habitat use.     

The impact of an ant–aphid mutualism on the functional composition of the secondary parasitoid community

1. Mutualistic and antagonistic interactions, although often studied independently, may affect each other, and food web dynamics are likely to be determined by the two processes working in concert. 2. The structure, and hence dynamics, of food webs depends on the relative abundances of generalist and specialist feeding guilds. Secondary parasitoids of aphids can be divided into two feeding guilds: (i) the more specialised endoparasitoids, which attack the primary parasitoid larvae in the still living aphid, and (ii) the generalist ectoparasitoids, which attack the pre‐pupa of the primary or secondary parasitoid in the mummified aphid. 3. We studied the effect of an ant–aphid mutualism on the relative abundance of these two functional groups of secondary parasitoids. We hypothesised that generalists will be negatively affected by the presence of ants, thus leading to a greater dominance of specialists. 4. We manipulated the access of ants (Lasius niger) to aphid colonies in which we placed parasitised aphids. Aphid mummies were collected and reared to determine the levels of endo‐ and ecto‐secondary parasitism. 5. When aphids were attended by L. niger the proportion of secondary parasitism by ectoparasitoids dropped from 26 to 8% of the total number of parasitised aphids, with Pachyneuron aphidis most strongly affected, while endoparasitoids as a group did not respond. However, among these Syrphophagus mamitus profited from ant attendance becoming the dominant secondary parasitoid, while parasitisation rates of Alloxysta and Phaenoglyphis declined. 6. The shift to S. mamitus as dominant secondary parasitoid in ant‐attended aphid colonies is likely due to the behavioural plasticity of this species in response to ant aggression, and a release from tertiary parasitism by generalist ectoparasitoids. 7. The reduction of secondary parasitism by generalist ectoparasitoids reduces the potential for apparent competition among primary parasitoids with consequences for the dynamics of the wider food web.     

The larval head of Nevrorthidae and the phylogeny of Neuroptera (Insecta)

External and internal head structures of larvae of Nevrorthidae were described in detail. The results were compared to conditions found in other representatives of Neuroptera and the other two neuropterid orders. The cladistic analysis supported the monophyly of Neuroptera, Neuroptera exclusive of Nevrorthidae, Hemerobiiformia, and Myrmeleontiformia. Neuroptera exclusive of Nevrorthidae are supported by the formation of an undivided postmentum and the presence of cryptonephric Malpighian tubules. The highly specialized articulation of the neck (Rollengelenk) and the absence of a salivary duct are autapomorphies of Nevrorthidae. Ithonidae and Polystoechotidae form a clade and are the sister group of the remaining Hemerobiiformia, which are characterized by the complete lack of a gula and a terminal filament of the antenna. Within this lineage, a clade comprising Mantispidae, Dilaridae, Berothidae, and Rhachiberothidae is well supported. Larvae of Myrmeleontiformia are characterized by a complex transformation of head structures, with a hypostomal bridge, a small triangular gula, largely reduced maxillary grooves, and anteriorly shifted posterior tentorial grooves. The slender finger‐like mid‐dorsal apodeme is another autapomorphy of the group. Psychopsidae are placed as the sister group of the remaining Myrmeleontiformia, which are characterized by a conspicuous, protruding ocular region (often less distinct or even absent in Nemopteridae). Ascalaphidae are the sister group of Myrmeleontidae. Larvae of both families share the fusion of the tibia and tarsus in the hind leg. The larval characters analysed were not sufficient for full resolution of the myrmeleontiform and hemerobiiform lineages. The position of several families such as Osmylidae, Sisyridae, and Coniopterygidae remains uncertain. The results are in agreement with an aquatic ancestor of Neuroptera and secondarily acquired terrestrial habits within the lineage (Neuroptera exclusive of Nevrorthidae), and another invasion of the aquatic environment by Sisyridae. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158 , 533–562.     

The female postabdomen and internal genitalia of the basal moth genus Agathiphaga (Insecta: Lepidoptera: Agathiphagidae): morphology and phylogenetic implications

The female postabdomen of Agathiphaga vitiensis terminates in a telescope‐type extensible oviscapt with an apial ‘oviscapt probe’ composed of fused segments behind VIII. Exceptionally within the Lepidoptera two pairs of long ‘anterior apophyses’ arise from segment VIII, from the dorsum and venter. Agathiphaga has the most elaborate postabdominal musculature recorded from female Lepidoptera, comprising 24 muscle sets of which nine may be family autapomorphies. Apophysis musculature does not permit unambiguous homologizing of the single anterior apophysis in Lepidoptera–Glossata with either the dorsal or ventral pair in Agathiphaga, but is compatible with an interpretation of the glossatan anterior apophyses as a composite formation. Nine muscle sets shared with rhyacophilid caddisflies are ascribed to the amphiesmenopteran ground plan. The spermathecal duct represents an intermediate stage between the simple type present in Micropterigidae and the ‘two‐compartment type’ characteristic of almost all other Lepidoptera. The spermatheca has no lagena. The bursa copulatrix is small and simple. Accessory glands are very large, simple sacs. There are 40 + ovarioles per ovary. A terminal cloaca is extremely short. The numerous ovarioles potentially support a sister‐group relationship between Agathiphagidae and all other Lepidoptera, whereas the spermathecal duct histology supports the alternative conservative placement of the family as sister group of all nonmicropterigid Lepidoptera. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 159 , 905–920.     

Biogeography meets conservation: the genetic structure of the endangered lycaenid butterfly Lycaena helle (Denis & Schiffermüller, 1775)

Cold‐adapted species are thought to have had their largest distribution ranges in central Europe during the glacial periods. Postglacial warming caused severe range shifts of such taxa into higher latitudes and altitudes. We selected the boreomontane butterfly Lycaena helle (Denis & Schiffermüller, 1775) as an example to demonstrate the genetic effects of range changes, and to document the recent status of highly fragmented remnant populations. We analysed five polymorphic microsatellite loci in 1059 individuals sampled at 50 different localities scattered over the European distribution area of the species. Genetic differentiation was strong among the mountain ranges of western Europe, but we did not detect similarly distinct genetic groups following a geographical pattern in the more eastern areas. The Fennoscandian populations form a separate genetic group, and provide evidence for a colonization from southern Finland via northern Scandinavia to south‐central Sweden. Species distribution modelling suggests a large extension of the spatial distribution during the last glacial maximum, but highlights strong retractions to a few mountain areas under current conditions. These findings, combined with our genetic data, suggest a more or less continuous distribution of L. helle throughout central Europe at the end of the last ice age. As a consequence of postglacial warming, the species retreated northwards to Fennoscandia and escaped increasing temperatures through altitudinal shifts. Therefore, the species is today restricted to population remnants located at the mountain tops of western Europe, genetically isolated from each other, and evolved into genetically unique entities. Rising temperatures and advancing habitat destruction threaten this wealth of biodiversity. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 155–168.     

A new cardiid bivalve from the Pliocene Baklan Basin (Turkey) and the origin of modern Ponto‐Caspian taxa

Abstract: We present the first record of the cardiid genus Monodacna from the Pliocene of Anatolia, Turkey. Monodacna imrei sp. nov. was found in the Pliocene Killik Formation from the western margin of the Baklan Basin, in very marginal brackish to freshwater lacustrine deposits. The new record extends the stratigraphic range of the modern Ponto‐Caspian genus back into the Pliocene and adds to earlier evidence that modern Ponto‐Caspian taxa originated in the Pliocene of south‐western Turkey.     

Trends and uncertainties in Siberian indicators of 20th century warming

Estimates of past climate and future forest biomass dynamics are constrained by uncertainties in the relationships between growth and climatic variability and uncertainties in the instrumental data themselves. Of particular interest in this regard is the boreal-forest zone, where radial growth has historically been closely connected with temperature variability, but various lines of evidence have indicated a decoupling since about the 1960s. We here address this growth-vs.-temperature divergence by analyzing tree-ring width and density data from across Siberia, and comparing 20th century proxy trends with those derived from instrumental stations. We test the influence of approaches considered in the recent literature on the divergence phenomenon (DP), including effects of tree-ring standardization and calibration period, and explore instrumental uncertainties by employing both adjusted and nonadjusted temperature data to assess growth-climate agreement. Results indicate that common methodological and data usage decisions alter 20th century growth and temperature trends in a way that can easily explain the post-1960 DP. We show that (i) Siberian station temperature adjustments were up to 1.3 °C for decadal means before 1940, (ii) tree-ring detrending effects in the order of 0.6–0.8 °C, and (iii) calibration uncertainties up to about 0.4 °C over the past 110 years. Despite these large uncertainties, instrumental and tree growth estimates for the entire 20th century warming interval match each other, to a degree previously not recognized, when care is taken to preserve long-term trends in the tree-ring data. We further show that careful examination of early temperature data and calibration of proxy timeseries over the full period of overlap with instrumental data are both necessary to properly estimate 20th century long-term changes and to avoid erroneous detection of post-1960 divergence.     

The approximate entropy of the electromyographic signals of tremor correlates with the osmotic fragility of human erythrocytes

Background  

The main problem of tremor is the damage caused to the quality of the life of patients, especially those at more advanced ages. There is not a consensus yet about the origins of this disorder, but it can be examined in the correlations between the biological signs of aging and the tremor characteristics.     

Comparative neuroanatomy suggests repeated reduction of neuroarchitectural complexity in Annelida

Background

Paired mushroom bodies, an unpaired central complex, and bilaterally arranged clusters of olfactory glomeruli are among the most distinctive components of arthropod neuroarchitecture. Mushroom body neuropils, unpaired midline neuropils, and olfactory glomeruli also occur in the brains of some polychaete annelids, showing varying degrees of morphological similarity to their arthropod counterparts. Attempts to elucidate the evolutionary origin of these neuropils and to deduce an ancestral ground pattern of annelid cerebral complexity are impeded by the incomplete knowledge of annelid phylogeny and by a lack of comparative neuroanatomical data for this group. The present account aims to provide new morphological data for a broad range of annelid taxa in order to trace the occurrence and variability of higher brain centers in segmented worms.

Results

Immunohistochemically stained preparations provide comparative neuroanatomical data for representatives from 22 annelid species. The most prominent neuropil structures to be encountered in the annelid brain are the paired mushroom bodies that occur in a number of polychaete taxa. Mushroom bodies can in some cases be demonstrated to be closely associated with clusters of spheroid neuropils reminiscent of arthropod olfactory glomeruli. Less distinctive subcompartments of the annelid brain are unpaired midline neuropils that bear a remote resemblance to similar components in the arthropod brain. The occurrence of higher brain centers such as mushroom bodies, olfactory glomeruli, and unpaired midline neuropils seems to be restricted to errant polychaetes.

Conclusions

The implications of an assumed homology between annelid and arthropod mushroom bodies are discussed in light of the 'new animal phylogeny'. It is concluded that the apparent homology of mushroom bodies in distantly related groups has to be interpreted as a plesiomorphy, pointing towards a considerably complex neuroarchitecture inherited from the last common ancestor, Urbilateria. Within the annelid radiation, the lack of mushroom bodies in certain groups is explained by widespread secondary reductions owing to selective pressures unfavorable for the differentiation of elaborate brains. Evolutionary pathways of mushroom body neuropils in errant polychaetes remain enigmatic.     

Earlier onset of the spring phytoplankton bloom in lakes of the temperate zone in a warmer climate

The decoupling of trophic interactions is potentially one of the most severe consequences of climate warming. In lakes and oceans the timing of phytoplankton blooms affects competition within the plankton community as well as food–web interactions with zooplankton and fish. Using Upper Lake Constance as an example, we present a model‐based analysis that predicts that in a future warmer climate, the onset of the spring phytoplankton bloom will occur earlier in the year than it does at present. This is a result of the earlier occurrence of the transition from strong to weak vertical mixing in spring, and of the associated earlier onset of stratification. According to our simulations a shift in the timing of phytoplankton growth resulting from a consistently warmer climate will exceed that resulting from a single unusually warm year. The numerical simulations are complemented by a statistical analysis of long‐term data from Upper Lake Constance which demonstrates that oligotrophication has a negligible effect on the timing of phytoplankton growth in spring and that an early onset of the spring phytoplankton bloom is associated with high air temperatures and low wind speeds.