With regard to suitable plants for comparatively deep water in ponds or lakes, lakewort and stonewort grow on the bottom, and do not, as a rule, attain any considerable height. ❋ Charles Edward Walker (N/A)
It is important to note that there is evidence that, at least in Lake Krankesjön, these phenotypic changes occurred after colonization of the stonewort, since when isopods were initially sampled shortly after the stonewort started to expand (in 1987) they were phenotypically similar to reed individuals ❋ Fabrice Eroukhmanoff Et Al. (2009)
By disrupting the ancestral modular structure and increasing the overall level of phenotypic integration, predator-mediated selection might have resulted in a hydrodynamically less favorable shape in the stonewort habitat as a correlated response to selection for higher phenotypic integration ❋ Fabrice Eroukhmanoff Et Al. (2009)
At equal speeds, the ratio between the forces of drag sustained by the reed individuals and the stonewort individuals is estimated to be 0.8522 ❋ Fabrice Eroukhmanoff Et Al. (2009)
Here we have shown that the stonewort isopods have a broader anterior head angle (Fig. 5) and a thinner tail than isopods in the reed habitat. ❋ Fabrice Eroukhmanoff Et Al. (2009)
Selection for lower foraging activity and lower speed in turn might presumably result from the fact that isopods in the stonewort cannot escape from fish predators by swimming away, but have to rely on combinations of cryptic behavior, morphology and pigmentation to avoid predation. ❋ Fabrice Eroukhmanoff Et Al. (2009)
In both Lake Tåkern and Lake Krankesjön, as in five other lakes, habitat-specific changes in pigmentation were observed following colonization: isopods became brighter in the stonewort stands compared to the darker ancestral populations in the reed, and these pigmentation differences are largely heritable ❋ Fabrice Eroukhmanoff Et Al. (2009)
Predation from visually hunting fish is thus likely to be much more intense in the stonewort habitat than in the reed, due to higher densities of perch in the novel habitat ❋ Fabrice Eroukhmanoff Et Al. (2009)
In a recent study, we have showed that in these lakes, stonewort ecotype isopods were smaller in body size and had lighter body pigmentation ❋ Fabrice Eroukhmanoff Et Al. (2009)
A simple biomechanical model has thus its limitations here, since to be able to swim at the same speed, the average stonewort isopod would have to produce a propulsion force 17. 3% higher than the reed isopods if one considers drag as the only factor affecting speed. ❋ Fabrice Eroukhmanoff Et Al. (2009)
Consequently, predator-mediated selection from fish in the stonewort habitat may have selected for novel trait combinations involving brighter pigmentation, prudent behaviors and lower speed to avoid the attention of predators. ❋ Fabrice Eroukhmanoff Et Al. (2009)
Since overall prey crypsis is likely be a result of both pigmentation and morphological traits such as size and shape, it might be an adaptive response to the visually hunting fish predators in the stonewort habitat. ❋ Fabrice Eroukhmanoff Et Al. (2009)
The latter mechanism may be selected for in the reed habitat, as reed isopods are faster at escaping and have higher endurance than stonewort isopods. ❋ Fabrice Eroukhmanoff Et Al. (2009)
Thus, the reed isopods perform better overall than the stonewort isopods, and are able to have both high speed and high endurance. ❋ Fabrice Eroukhmanoff Et Al. (2009)
These size classes were above or below .95 cm for the reed ecotypes, and above or bellow .75 cm for the stonewort ecotype. ❋ Fabrice Eroukhmanoff Et Al. (2009)
They are more stream-profiled and have higher escape speeds than isopods in the newly colonized stonewort habitat, which has higher density of fish predators. ❋ Fabrice Eroukhmanoff Et Al. (2009)
In contrast, the isopods from the recently colonized stonewort habitat have a higher level of phenotypic integration in morphology due to more strengthened correlations between pigmentation and body size. ❋ Fabrice Eroukhmanoff Et Al. (2009)
Linear regression between endurance and speed for individuals from the reed and the stonewort. ❋ Fabrice Eroukhmanoff Et Al. (2009)
Indeed, although our data on exploratory behaviors comes from only one lake, and thus precludes generalization, we have also found in a previous study that stonewort individuals from both lakes had a lower propensity to engage mating, which also independently suggests a tendency to avoid exposure ❋ Fabrice Eroukhmanoff Et Al. (2009)
Using the inverse of this ratio, we can estimate the extra amount of force (in%) that would be needed by an average stonewort isopod to swim at the same speed as an average reed isopod. ❋ Fabrice Eroukhmanoff Et Al. (2009)
