Functions of Invertebrate Hemoglobins with Special Reference to Adaptations to Environmental Hypoxia

The oxygen-binding properties and some associated structuralfeatures of invertebrate hemoglobins (Hb) are reviewed togetherwith the environmental conditions (particularly in stressfulhabitats) that influence oxygen-binding functions in nature.Compared to the vertebrates invertebrate Hbs display a spectacularvariation in functional properties, which is manifest withinthe major systematic groups of animals and within the differenthistological and molecular categories of the pigment. This variabilityis seen primarily to represent adaptations to the wide rangeof environmental conditions to which Hb-bearing invertebratesare subjected in nature but also to reflect certain organismicfunctions, which determine the internal conditions under whichthe Hbs work in life. These adaptations appear to be uniquelydirected towards optimizing the transfer of oxygen from theenvironmental source to the mitochondrial combustion sites.The immense structural and functional complexity of invertebrateHb systems may well compensate for a decreased organizationat the organ level compared to that in vertebrates shiftingmore of the regulatory burden to the molecular level.     

Divergence along a steep ecological gradient in lake whitefish (Coregonus sp.)

To understand mechanisms structuring diversity in young adaptive radiations, quantitative and unbiased information about genetic and phenotypic diversity is much needed. Here, we present the first in‐depth investigation of whitefish diversity in a Swiss lake, with continuous spawning habitat sampling in both time and space. Our results show a clear cline like pattern in genetics and morphology of populations sampled along an ecological depth gradient in Lake Neuchâtel. Divergent natural selection appears to be involved in shaping this cline given that trait specific P_ST‐values are significantly higher than F_ST‐values when comparing populations caught at different depths. These differences also tend to increase with increasing differences in depth, indicating adaptive divergence along a depth gradient, which persists despite considerable gene flow between adjacent demes. It however remains unclear, whether the observed pattern is a result of currently stable selection‐gene flow balance, incipient speciation, or reverse speciation due to anthropogenic habitat alteration causing two formerly divergent species to collapse into a single gene pool.