Biology subjects

Mann, R. P.

Publications and source records attributed to Mann, R. P..

3 recordsLinked to original sources

bioRxiv2018

Modelling predation and mortality rates from the fossil record of gastropods

Gastropods often show signs of unsuccessful attacks by predators in the form of healed scars in their shells. As such, fossil gastropods can be taken as providing a record of predation through ge-ological time. However, interpreting the number of such scars has proved to be problematic - would a low number of scars mean a low rate of attack, or a high rate of success, for example? Here we develop a model of scar formation, and formally show that in general these two variables cannot be disambiguated without further information about population structure. Nevertheless, by making the probably reasonable assumptions that the non-predatory death rate is both constant and low, we show that it is possible to use relatively small assemblages of gastropods to produce accurate estimates of both attack and success rates, if the overall death rate can be estimated. We show in addition what sort of information would be required to solve this problem in more general cases. However, it is unlikely that it will be possible to extract the relevant information easily from the fossil record: a variety of important collection and taphonomic biases are likely to intervene to obscure the data that gastropod assemblages may yield.

paleontology↗

bioRxiv2018

Collective decision-making by rational individuals

The patterns and mechanisms of collective decision making in humans and animals have attracted both empirical and theoretical attention. Of particular interest has been the variety of social feedback rules, and the extent to which these behavioural rules can be explained and predicted from theories of rational estimation and decision making. However, models that aim to model the full range of social information use have incorporated ad hoc departures from rational decision-making theory to explain the apparent stochasticity and variability of behaviour. In this paper I develop a model of social information use and collective decision making by fully rational agents that reveals how a wide range of apparently stochastic social decision rules emerge from fundamental information asymmetries both between individuals, and between the decision-makers and the observer of those decisions. As well as showing that rational decision making is consistent with empirical observations of collective behaviour, this model makes several testable predictions about how individuals make decisions in groups, and offers a valuable perspective on how we view sources of variability in animal, and human, behaviour.

animal behavior and cognition↗

bioRxiv2017

History is written by the victors: the effect of the push of the past on the fossil record

Phylogenies may be modelled using \"birth-death\" models for speciation and extinction, but even when a homogeneous rate of diversification is used, survivorship biases can generate remarkable rate heterogeneities through time. One such bias has been termed the \"push of the past\", by which the length of time a clade has survived is conditioned on the rate of diversification that happened to pertain at its origin. This creates the illusion of a secular rate slow-down through time that is, rather, a reversion to the mean. Here we model the controls on the push of the past, and the effect it has on clade origination times, and show that it largely depends on underlying extinction rates. An extra effect increasing early rates of lineage generation is also seen in large clades. These biases are important but relatively neglected influences on many aspects of diversification patterns, such as diversification spikes after mass extinctions and at the origins of clades; they also influence rates of fossilisation, changes in rates of phenotypic evolution and even molecular clocks. These inevitable features of surviving and/or large clades should thus not be generalised to the diversification process as a whole without additional study of small and extinct clades.

paleontology↗