New trends in evolutionary biology: biological, philosophical and social science perspectives

Evolutionary changes in the capacity for organismic autonomy

Studies of macroevolution have revealed various trends in evolution - which have been documented and discussed. There is, however, no consensus on this topic. Since Darwin's time one presumption has persisted: that throughout evolution organisms increase their independence from and stability towards environmental influences. Although this principle has often been stated in the literature, it played no role in mainstream theory. In a closer examination, we studied this particular feature and described that many of the major transitions in animal evolution have been characterized by changes in the capacity for physiological regulation. Organisms gained in robustness, self-regulation, homeostasis and stabilized self-referential, intrinsic functions within their respective systems. This is associated with expanded environmental flexibility, such as new opportunities for movement and behaviour. Together, these aspects can be described as changes in the capacity for autonomy. There seems to be a large-scale trajectory in evolution during which some organisms gained in autonomy and flexibility. At the same time, adaptations to the environment emerged that were a prerequisite for survival. Apparently, evolution produced differential combinations of autonomy traits and adaptations. These processes are described as modifications in relative autonomy because numerous interconnections with the environment and dependencies upon it were retained. Also, it is not a linear trend, but rather an outcome of all the diverse processes which have been involved during evolutionary changes. Since the principle of regulation is a core element of physiology, the concept of autonomy is suitable to build a bridge from physiology to evolutionary research.

Two independent sulfation processes regulate mouth-form plasticity in the nematode Pristionchus pacificus

Sulfation of biomolecules, like phosphorylation, is one of the most fundamental and ubiquitous biochemical modifications with important functions during detoxification. This process is reversible, involving two enzyme classes: a sulfotransferase, which adds a sulfo group to a substrate; and a sulfatase that removes the sulfo group. However, unlike phosphorylation, the role of sulfation in organismal development is poorly understood. In this study, we find that two independent sulfation events regulate the development of mouth morphology in the nematode Pristionchus pacificus. This nematode has the ability to form two alternative mouth morphologies depending on environmental cues, an example of phenotypic plasticity. We found that, in addition to a previously described sulfatase, a sulfotransferase is involved in regulating the mouth-form dimorphism in P. pacificus However, it is unlikely that both of these sulfation-associated enzymes act upon the same substrates, as they are expressed in different cell types. Furthermore, animals mutant in genes encoding both enzymes show condition-dependent epistatic interactions. Thus, our study highlights the role of sulfation-associated enzymes in phenotypic plasticity of mouth structures in Pristionchus.