Predicted warming and browning affect timing and magnitude of plankton phenological events in lakes: a mesocosm study

1. Aquatic ecosystems in Northern Europe are expected to face increases in temperature and water colour (TB) in future. While effects of these factors have been studied separately, it is unknown whether and how a combination of them might affect phenological events and trophic interactions. 2. In a mesocosm study, we combined both factors to create conditions expected to arise during the coming century. We focused on quantifying effects on timing and magnitude of plankton spring phenological events and identifying possible mismatches between resources (phytoplankton) and consumers (zooplankton). 3. We found that the increases in TB had important effects on timing and abundance of different plankton groups. While increased temperature led to an earlier peak in phytoplankton and zooplankton and a change in the relative timing of different zooplankton groups, increased water colour reduced chlorophyll‐a concentrations. 4. Increased TB together benefitted cladocerans and calanoid copepods and led to stronger top‐down control of algae by zooplankton. There was no sign of a mismatch between primary producers and grazers as reported from other studies. 5. Our results point towards an earlier onset of plankton spring growth in shallow lakes in future with a stronger top‐down control of phytoplankton by zooplankton grazers.     

Geographic patterns of diversification: an example with ectoparasitic insects

On any spatial scale, the species composition of a taxonomic group often departs from a phylogenetically random subset drawn from the pool of species available on a higher scale. Analysis of the uneven representation of related lineages in different assemblages can reveal the action of various forces shaping their diversification. For any assemblage, unequal diversification among lineages can be estimated using diversity skewness, an index of the balance of a phylogenetic tree whose values increase with increasing differences in diversification rates among tree branches. We tested for geographical patterns in the diversity skewness of flea assemblages parasitic on small mammals in 26 distinct geographic localities from the Palaearctic and 15 from the Nearctic. Overall, diversity skewness of the Nearctic flea assemblage was unexpectedly high compared to that of the global flea fauna, whereas that of the Palaearctic did not depart from the expectations of a null model. On a smaller scale, the diversity skewness of local flea assemblages was sometimes lower, sometimes higher, but, in most of the 41 localities, it did not differ significantly from that of random subsets taken from the species pool available on the larger spatial scale (either the world fauna or that of the biogeographical realm, i.e. Palaearctic or Nearctic). More importantly, among Palaearctic assemblages, diversity skewness increased with increasing latitude and/or decreasing mean air temperatures. The different patterns observed in the Palaearctic and Nearctic may be in part due the fact that flea diversification appears to have been more intense in the former than the latter, and to differences between them in relief and glacial history. Temperature‐driven speciation rates may well explain the latitudinal gradient in diversity skewness in the Palaearctic. The results illustrate the action of various biogeographical processes in shaping the uneven differentiation of flea lineages on different spatial scales. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 807–814.     

Genome size as a determinant of growth and life-history traits in crustaceans

Genome size varies tremendously both within and among taxa, and strong correlations between genome size and various physiological and ecological attributes suggest that genome size is a key trait of organisms, yet the causalities remains vague. In the present study, we tested how genome size is related to key physiological and ecological properties in five large orders of crustaceans: Decapoda, Cladocera, Amphipoda, Calanoida, and Cyclopoida. These span a wide range in sizes, habitats and life-history traits. To some extent, genome size reflected phylogenetic footprints but, generally, a very wide range in genome size was found within all orders. Genome size was positively correlated with body size in Amphipoda, Cladocera, and Copepoda, but not for Decapoda in general. This could indicate that the evolution of body size occurs mainly by changing cell size for the three first orders, whereas it is more attributed to cell numbers for Decapoda. Cladocera, with direct development and a high growth rate, have minute genomes compared to copepods that possess a more complex life history, whereas, within Decapoda and Amphipoda, developmental complexity is not related to genome size. The present study suggests that, within the crustaceans, selection for a wide variety of life-history strategies has led to widely different genome sizes.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 393–399.     

Molecular data and species distribution models reveal the Pleistocene history of the mayfly Ameletus inopinatus (Ephemeroptera: Siphlonuridae)1

1. We investigated the Pleistocene and Holocene history of the rare mayfly Ameletus inopinatus EATON 1887 (Ephemeroptera: Siphlonuridae) in Europe. We used A. inopinatus as a model species to explore the phylogeography of montane, cold‐tolerant aquatic insects with arctic–alpine distributions. 2. Using species distribution models, we developed hypotheses about the species demographic history in Central Europe and the recolonisation history of Fennoscandia. We tested these hypotheses using mitochondrial cytochrome oxidase I (mtCOI) sequence data and compared our genetic results with previously generated microsatellite data to explore genetic diversity distributions of A. inopinatus. 3. We observed old lineages, deep splits and almost complete lineage sorting of mtCOI sequences among mountain ranges. These results support a periglacial survival, i.e. persistence at the periphery of Pleistocene glaciers in Central Europe. 4. There was strong differentiation between the Fennoscandian and all other populations, indicating that Fennoscandia was recolonised from a refugium not accounted for in our sampling. High degrees of population genetic structure within the northern samples suggest that Fennoscandia was recolonised by more than one lineage. However, this structure was not apparent in previously published microsatellite data, consistent with secondary contact without sexual incompatibility or with sex‐biased dispersal. 5. Our demographic analyses indicate that (i) the separation of northern and Central European lineages occurred during the early Pleistocene; (ii) Central European populations have persisted independently throughout the Pleistocene and (iii) the species extended its range about 150 000 years ago.     

Competition between isoprene emission and pigment synthesis during leaf development in aspen

In growing leaves, lack of isoprene synthase (IspS) is considered responsible for delayed isoprene emission, but competition for dimethylallyl diphosphate (DMADP), the substrate for both isoprene synthesis and prenyltransferase reactions in photosynthetic pigment and phytohormone synthesis, can also play a role. We used a kinetic approach based on post‐illumination isoprene decay and modelling DMADP consumption to estimate in vivo kinetic characteristics of IspS and prenyltransferase reactions, and to determine the share of DMADP use by different processes through leaf development in Populus tremula. Pigment synthesis rate was also estimated from pigment accumulation data and distribution of DMADP use from isoprene emission changes due to alendronate, a selective inhibitor of prenyltransferases. Development of photosynthetic activity and pigment synthesis occurred with the greatest rate in 1‐ to 5‐day‐old leaves when isoprene emission was absent. Isoprene emission commenced on days 5 and 6 and increased simultaneously with slowing down of pigment synthesis. In vivo Michaelis–Menten constant (K_m) values obtained were 265 nmol m^?2 (20 μm ) for DMADP‐consuming prenyltransferase reactions and 2560 nmol m^?2 (190 μm ) for IspS. Thus, despite decelerating pigment synthesis reactions in maturing leaves, isoprene emission in young leaves was limited by both IspS activity and competition for DMADP by prenyltransferase reactions.     

GETTING MORAL ENHANCEMENT RIGHT: THE DESIRABILITY OF MORAL BIOENHANCEMENT

We respond to a number of objections raised by John Harris in this journal to our argument that we should pursue genetic and other biological means of morally enhancing human beings (moral bioenhancement). We claim that human beings now have at their disposal means of wiping out life on Earth and that traditional methods of moral education are probably insufficient to achieve the moral enhancement required to ensure that this will not happen. Hence, we argue, moral bioenhancement should be sought and applied. We argue that cognitive enhancement and technological progress raise acute problems because it is easier to harm than to benefit. We address objections to this argument. We also respond to objections that moral bioenhancement: (1) interferes with freedom; (2) cannot be made to target immoral dispositions precisely; (3) is redundant, since cognitive enhancement by itself suffices.     

The genus Luppovia and the phylogeny of Cretaceous heteromorphic ammonoids

The unique preservation of heteromorphic shells of Luppovia Kakabadze, Bogdanova & Mikhailova 1978 from the Aptian deposits of Bolshoj Balkhan (western Turkmenia) made it possible to study the microstructure, internal shell characteristics and suture ontogeny of this genus. Microstructural investigations revealed that the dorsal shell wall in Luppovia is composed of three layers in contrast to that of monomorphic ammonoids, which is single-layered. This ability of secreting different numbers of layers in monomorphs and heteromorphs demonstrates plasticity of secreting activity of the mantle epithelium. Data obtained from the study of internal shell structure and suture ontogeny have been compared. Both these methods of investigation lead to the conclusion that the genus Luppovia belongs to the order Ammonitida. The results obtained confirm the viewpoint that the Cretaceous heteromorphic superfamilies Turrilitaceae and Ancylocerataceae have independent origins and belong to two different orders, Lytoceratida and Ammonitida, respectively. □ Ammonoidea , Luppovia, shell structure, ontogeny, phylogeny, Cretaceous.     

Plastic resource polymorphism: effects of resource availability on Arctic char (Salvelinus alpinus) morphology

Resource polymorphism has been suggested to be a platform for speciation. In some cases resource polymorphism depends on phenotypic plasticity but in other cases on genetic differences between morphotypes, which in turn has been suggested to be the ongoing development of a species pair. Here we study environmentally induced morphological differences in two age classes of Arctic char ( Salvelinus alpinus ) influencing char performance and diet in relation to resource availability. We found that structurally complex habitats with relatively lower zooplankton densities gave rise to individuals with a deeper body, and a downward positioned tip of the snout compared with individuals from structurally simple habitats with relatively higher zooplankton densities for both age classes. Environment also had an effect on foraging efficiency on zooplankton, with fish from structurally simple habitats had a higher foraging rate than fish from structurally complex habitats. Diet analyses showed that resource use in char mainly depends on the relative abundance of different resources. Therefore, to gain further understanding of resource polymorphism we suggest that future studies must include population dynamic feedbacks by the resources on the consumers.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 85 , 341–351.     

The effect of water colour on lake hydrodynamics: a modelling study

1. The one‐dimensional equation solver, PROgram for Boundary layers in the Environment, was used to simulate the temperature structure of Lake Erken, a medium‐sized Swedish lake, assuming differing extinction coefficients for a series of modelled years driven by observed meteorological data and by a set of idealized meteorological data. 2. Results suggested that, as expected, larger extinction coefficients initially led to surface waters becoming warmer. The reverse was true late in the summer, however, as the warming induced by greater absorption of solar radiation was outweighed by the cooling effects of entrained colder hypolimnetic water. 3. There was between a two‐ and fourfold inter‐annual variation in the effects on key physical lake parameters, induced by changing extinction coefficient, such as maximum heat flux, heat content and Schmidt stability. 4. The change in surface heat flux induced by a change in extinction coefficient was up to almost 50 W m⁻². 5. In the summer, changes in extinction coefficient from 0.5 to 0.2 m⁻¹ led to a dramatic shift in the duration of the stratified period as well as to enormous changes in Schmidt stability and hypolimnetic temperature. 6. Future changes to extinction coefficients of small and medium‐sized lakes are likely to have wide‐ranging effects on lake thermal structure and ecology.