Cladocera Diversity,Abundance and Habitat in a Western Thailand Stream

Longitudinal and temporal distribution was determined for 40 species of cladocerans at sites between the headwaters and mouth of Khayeng Stream, a relatively pristine waterway in western Thailand. Cladocerans were confined mostly to lentic areas and abundance between April and September was highest in September, largely a consequence of a floodplain that developed near the mouth. Species richness was related directly to cladoceran abundance. Cladocerans were dominated numerically by three species, Ceriodaphnia cornuta, Diaphanosoma excisum, and D. sarsi. Most species were accommodated within four assemblages. Conductivity, water velocity, pH and temperature were important to species distribution, particularly velocity and conductivity. The most common assemblage was also the most speciose and occurred in moderate total abundance. The second assemblage was also speciose but low in total abundance. Species abundance in groups 1 and 2 tended to be positively related to conductivity and negatively, but weakly, related to pH and temperature. The third assemblage consisted of a single species and occurred in water of low conductivity while the fourth assemblage contained few species and low in overall abundance.     

Habitat fragmentation and body‐shape variation of African hind Cephalopholis taeniops (Valenciennes) in an archipelago system (Cape Verde,eastern Atlantic Ocean)

Morphological variations of the serranid fish Cephalopholis taeniops were studied in relation to habitat fragmentation in the Cape Verde Archipelago. While a significant allometric effect existed (11·5% of total body‐shape variation), differences in morphology associated with sex and ontogeny were not significant. MANOVA followed by CVA showed that each island presented a particular allometric pattern. Average body shape for all islands was well discriminated with CVA models. Pair‐wise comparisons of the ontogeny of morphological change between islands revealed that northern islands (Santo Antão, São Vicente and Santa Luzia) along with Boavista Island showed a similar direction in shape ontogeny, while all other paired comparisons indicated different ontogenetic patterns. When comparing directions of inter‐population shape changes, individuals from Fogo Island, the southernmost locality, departed far from the orthogonal relation, suggesting that they were undergoing independent body‐shape trajectories. Physical isolation by geographic distance and depth was positively correlated with morphological divergence among populations from different islands. This finding supports the hypothesis that habitat fragmentation in the Cape Verde Archipelago can be interpreted in terms of marine population structure.