Testing congruency of geographic and genetic population structure for a freshwater mussel (Bivalvia: Unionoida) and its host fish

The macrogeographic dispersal of unionoid mussels is largely dependent on movement by their host fish. The snuffbox mussel Epioblasma triquetra (Unionoida) and other congeners use a novel trapping behaviour to parasitize potential host fish with their larvae (glochidia). Common logperch (Percina caprodes) trapped by E. triquetra survive the trapping behaviour, whereas other darter species (Etheostoma and Percina) do not, thus, making the P. caprodes–E. triquetra relationship a good candidate system for a coevolutionary study. We hypothesized that the geographic genetic structure of E. triquetra should closely match that of its host, albeit with greater interpopulation divergences as a result of its dependency on the host for dispersal. Mantel tests of parallel pairwise matrices of population divergence (Jost's D) and genetic assignment tests based on microsatellite DNA data showed that the genetic population structures of both species were broadly, but not perfectly, congruent. Therefore, it appears that P. caprodes are not solely responsible for the genetic population structure observed for snuffbox and may not necessarily be the mussel's only host across its entire range. This suggests the potential for a geographic mosaic for coevolution in unionoids and darters. The findings of the present study reinforce the need for a joint study and conservation of unionoids and host fish aiming to protect these coevolved taxa. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 669–685.     

Nettle-feeding nymphalid butterflies: temperature, development and distribution

1. Four nymphalid butterflies, Aglais urticae L., Inachis io L., Polygonia c-album L. and Vanessa atalanta L., share the same primary host plant, Urtica dioica L., but have different margins to their U.K. and European ranges. Their developmental responses to a series of constant temperatures were measured.
2. Degree-day requirements were found broadly to explain the relative distributions and differences in voltinism of A. urticae , P. c-album and I. io . The migrant V. atalanta did not fit into the predicted pattern, and this species may be more limited by its ability to overwinter.
3. Although the most northerly distributed species, A. urticae , had the lowest degree-day requirement, it had the highest developmental threshold and performed best (for mortality, pupal weight and relative growth rate) at high experimental temperatures. It is suggested that this may be due to the gregarious nature of its larvae and their possible ability to thermoregulate.
4. At southern margins, different distributional limits may be explained partly by larval gregariousness (a more northern trait) and maximum temperatures at which development is possible.
5. Limits to the distributions of these mobile species are at least partially explicable by the interaction of climatic patterns and thermal biology. A rapid response to climate change is predicted, and has already been observed in two of the species.     

The effect of conspecific attraction on metapopulation dynamics

Random dispersal direction is assumed in all current metapopulation models. This assumption is called into question by recent experiments demonstrating that some species disperse preferentially to sites occupied by conspecifies. We incorporate conspecific attraction into two metapopulation models which differ in type of dispersal, the Levins model and a two-dimensional stepping-stone model. In both models, conspecific attraction lowers the proportion of occupied habitat patches within a metapopulation at equilibrium.     

Fitness of two sibling species of Asobara (Braconidae:Alysiinae), larval parasitoids of Drosophilidae in different microhabitats

Abstract. 1. Two sibling species of larval endoparasitoids of Drosophilidae: Asobara tabida (Nees) and A.rufescens (Foerster) occur in the same macrohabitat, but inhabit different microhabitats. Each species is most attracted by odours of its own microhabitat.
2. In order to assess the adaptive value of the microhabitat preference we studied the survival of both parasitoids in the major host species that occur in these microhabitats.
3. Survival in the major host in the preferred microhabitat was shown to be 40% higher for A.tabida and 30% higher for A.rufescens when compared to survival in the major host in the non-preferred microhabitat.
4. Measurements of developmental rates, specific mortalities and dry weights of the parasitoids suggest that the differential survival is due to differences in synchronization with the hosts.
5. The possible evolutionary consequences of some biological characteristics in Asobara are discussed. Microhabitat selection, differential survival, development and mating behaviour are attributes likely to have played a role in the reduction of gene flow between populations of the ancestral species, either in primary or in secondary sympatry.     

Salicylhydroxamic Acid Mimics Esterase-like Action

Salicylhydroxamic acid (SHAM), an inhibitor of the alternativerespiratory pathway, reacts with 2', 7'-dichlorofluorescin diacetate(DCFH-DA) and fluorescein diacetate to form 2', 7'-dichlorofluorescinand fluorescein, respectively. These reactions show that SHAMpossesses esterase-like activity. As SHAM may act on endogenousacetoxymethyl ester-type compounds, assessment of respirationpatterns of cells requires cautious interpretation, especiallyduring prolonged incubation. Key words: Salicylhydroxamic acid, respiration, alternative pathway, viability test     

TWO STALEMATES IN THE PHILOSOPHICAL DEBATE ABOUT ABORTION AND WHY THEY CANNOT BE RESOLVED USING ANALOGICAL ARGUMENTS

Philosophical debate about the ethics of abortion has reached stalemate on two key issues. First, the claim that foetuses have moral standing that entitles them to protections for their lives has been neither convincingly established nor refuted. Second, the question of a pregnant woman's obligation to allow the gestating foetus the use of her body has not been resolved. Both issues are deadlocked because philosophers addressing them invariably rely on intuitions and analogies, and such arguments have weaknesses that make them unfit for resolving the abortion issue. Analogical arguments work by building a kind of consensus, and such a consensus is virtually unimaginable because (1) intuitions are revisable, and in the abortion debate there is great motive to revise them, (2) one's position on abortion influences judgments about other issues, making it difficult to leverage intuitions about other ethical questions into changing peoples' minds about abortion, and (3) the extent of shared values in the abortion debate is overstated. Arguments by analogy rely on an assumption of the commensurability of moral worldviews. But the abortion debate is currently unfolding in a context of genuinely incommensurable moral worldviews. The article ends by arguing that the default position must be to permit abortion as a consequence of the freedom of conscience protected in liberal societies.     

Predicting development, metabolism and secondary production for the invertebrate predator Bythotrephes

1. Rates of embryonic and post-embryonic development for Bythotrephes cederstroemi from Lakes Erie, Huron and Michigan are represented almost equally well by three empirical models across water temperatures ranging from about 12–22 °C, but at lower temperatures two of the competing models fail and an exponential development rate model proves most robust.
2. Clutch masses of parthenogenic females can greatly exceed the tissue mass of the mother. Clutch size is strongly correlated with the mass of reproductive adults, accounting for over 90% of the variation among individuals. Hence, the mass gain from neonate to reproductive adult can be estimated directly from clutch size.
3. Tissue stoichiometries, respiration quotients and stoichiometries of C and N metabolism were determined experimentally, extending the predictions of existing respiration and growth models.
4. A predictive model for growth and production by the invertebrate predator has advantages over previous model formulations owing to our expanded calibration data base. The model is presented in a modular design that is easily upgraded as additional calibration data become available.