Thursday, June 4, 2015

Meeuwig et al. 2015 "When science places threatened species at risk "

This cake is for Meeuwig et al. 2015, entitled "When science places threatened species at risk".  The cake is presented by Rob Harcourt.

Short description:

The new information derived from telemetry combined with other biological knowledge suggests that shark-human interactions are largely random and rare events as sharks move through their habitats. Kill orders such as the one in WA are short-sighted, misdirected, target a political rather than an actual need, and block investment in knowledge generation. There is a serious need to ensure that science done through the tagging and tracking of animals is not used to generate contrary and morally questionable outcomes, particularly for threatened species. Ultimately, we improve ocean safety through enhanced knowledge rather than undermining the very basis of that knowledge by killing tagged research animals. 

Frère et al. 2015 "Polyandry in dragon lizards: inbred paternal genotypes sire fewer offspring"

This cake is to celebrate Frère et al. 2015, "Polyandry in dragon lizards: inbred paternal genotypes sire fewer offspring".  The cake (muffins) is presented by Martin Whiting.


Multiple mating in female animals is something of a paradox because it can either be risky (e.g., higher probability of disease transmission, social costs) or provide substantial fitness benefits (e.g., genetic bet hedging whereby the likelihood of reproductive failure is lowered). The genetic relatedness of parental units, particularly in lizards, has rarely been studied in the wild. Here, we examined levels of multiple paternity in Australia's largest agamid lizard, the eastern water dragon (Intellagama lesueurii), and determined whether male reproductive success is best explained by its heterozygosity coefficient or the extent to which it is related to the mother. Female polyandry was the norm: 2/22 clutches (9.2%) were sired by three or more fathers, 17/22 (77.2%) were sired by two fathers, and only 3/22 (13.6%) clutches were sired by one father. Moreover, we reconstructed the paternal genotypes for 18 known mother–offspring clutches and found no evidence that females were favoring less related males or that less related males had higher fitness. However, males with greater heterozygosity sired more offspring. While the postcopulatory mechanisms underlying this pattern are not understood, female water dragons likely represent another example of reproduction through cryptic means (sperm selection/sperm competition) in a lizard, and through which they may ameliorate the effects of male-driven precopulatory sexual selection.

Barneche and Allen 2015, Embracing general theory and taxon-level idiosyncrasies to explain nutrient recycling

This cake is to celebrate a paper by Barneche and Allen, entitled "Embracing general theory and taxon-level idiosyncrasies to explain nutrient recycling".  It is being presented by Diego Barneche.

Short description:

The value of mathematical theory in ecology is controversial; most ecologists are found in either side of a dichotomy: while some argue that general theory is the optimal way to advance mechanistic understanding in the discipline, others claim that general simple theory does not capture most of the variation in living systems. In our recent commentary piece (Barneche & Allen 2015), we argue that ecologists should embrace both views, and that this duality can be reconciled by using a combination of general mathematical theory and advanced statistical techniques, following a sequence of steps described below. These steps are exemplified using a recent study that uses a combination of predictions from the metabolic theory (MT) and ecological stoichiometry (ES) to explain body mass scaling of nutrient recycling rates in marine animals (Allgeier et al. 2015).

The first step entails recognising the scope of a given theory and explicitly declaring what assumptions are necessary to reach a given set of predictions. Allgeier et al. (2015) show that nutrient recycling rates follow 3/4-power body mass scaling, as should be predicted from MT-ES. Our study provides the theoretical rationale and the assumptions necessary to yield such prediction. In our view, this framework is essential to the understanding of ecological processes because false predictions serve as indications that one or more assumptions are violated/wrong – thus providing avenues on how to move forward on the understanding of ecological processes, either by modifying existing theory or by developing a new one. Although this assumption-prediction-testing-falsify cycle is the very core of the scientific method, it has been largely neglected in ecology.

The second step involves using statistical methods such as mixed effects models, which allow for the estimation of overall (i.e. mean) trends while accounting for deviations attributable to other variables not included in the theory. Many recent studies have made use of these mixed models to test for general theory while accounting for differences attributable to taxonomy (i.e. random effects) – there is to recognise that taxa might deviate from each other and from the overall trend. While taxonomy is not a true predictor in the sense that it characterises a process, it provides clues to what traits are responsible for differences among taxa, thus providing ideas on to how we should move forward.

The third and final step requires a careful exploration of how much variation is explained by different predictors, and what are the magnitudes of each one of them. For example, Allgeier et al. (2015) provides compelling evidence that despite substantial taxon-level idiosyncrasies (characterised as random effects in their LMM), body size is still the strongest predictor of nutrient recycling rates in marine animals. In our commentary, we notice that body size spans many orders of magnitude, while the other fixed-effect predictor (nutrient body content) spans less than one order of magnitude. However, the effect of body nutrient is stronger than that of body size, indicating that, for example, a doubling in body nutrient content has a greater effect in nutrient recycling rates than an equivalent increase in body mass.

We hope that with this roadmap, ecologists will increasingly embrace general theory and ecological idiosyncrasies in one single framework, which should help advance our understanding of ecological patterns and processes.