Development and Evolutionary Constraints in Animals

We review the evolutionary importance of developmental mechanisms in constraining evolutionary changes in animals—in other words, developmental constraints. We focus on hard constraints that can act on macroevolutionary timescales. In particular, we discuss the causes and evolutionary consequences of the ancient metazoan constraint that differentiated cells cannot divide and constraints against changes of phylotypic stages in vertebrates and other higher taxa. We conclude that in all cases these constraints are caused by complex and highly controlled global interactivity of development, the disturbance of which has grave consequences. Mutations that affect such global interactivity almost unavoidably have many deleterious pleiotropic effects, which will be strongly selected against and will lead to long-term evolutionary stasis. The discussed developmental constraints have pervasive consequences for evolution and critically restrict regeneration capacity and body plan evolution.

Adaptations to different habitats in sexual and asexual populations of parasitoid wasps: a meta-analysis

BACKGROUND

Coexistence of sexual and asexual populations remains a key question in evolutionary ecology. We address the question how an asexual and a sexual form of the parasitoid Venturia canescens can coexist in southern Europe. We test the hypothesis that both forms are adapted to different habitats within their area of distribution. Sexuals inhabit natural environments that are highly unpredictable, and where density of wasps and their hosts is low and patchily distributed. Asexuals instead are common in anthropic environments (e.g., grain stores) where host outbreaks offer periods when egg-load is the main constraint on reproductive output.

METHODS

We present a meta-analysis of known adaptations to these habitats. Differences in behavior, physiology and life-history traits between sexual and asexual wasps were standardized in term of effect size (Cohen's d value; Cohen, 1988).

RESULTS

Seeking consilience from the differences between multiple traits, we found that sexuals invest more in longevity at the expense of egg-load, are more mobile, and display higher plasticity in response to thermal variability than asexual counterparts.

DISCUSSION

Thus, each form has consistent multiple adaptations to the ecological circumstances in the contrasting environments.

Paul Kammerer and the inheritance of acquired characteristics

The Austrian biologist Paul Kammerer (1880-1926) would by now be long forgotten if Arthur Koestler had not published ‘The case of the Midwife toad’, in which he depicted Kammerer as a victim of the paradigm battle between neo-Darwinists and Lamarckists. Kammerer is still on the scientific agenda, with at least 10 publications since 2005. The question is still out if Kammerer fabricated his scientific results or not. In this paper we provide the evidence that Kammerer consistently faked experimental results. We show (1) that the design of his experiments could never have produced the results that he claimed, (2) that the assumptions he made about the developmental biology of the species he studied are falsified by recent research, and (3) that the specimens he showed as proof for the success of his experiments came from nature.