Effects of Trawl Selectivity and Genetic Parameters on Fish Body Length Under Long-Term Trawling

Long-term fishing pressure affects the biological characteristics of exploited fish stocks. The biological characteristics of hairtail(Trichiurus lepturus) in the East China Sea are unable to recover because of long-term trawling. Fishing induces evolutionary effects on the fish's biological characteristics. Evidence of these changes includes small size at age, a shift to earlier age structure, and early maturation. Natural and artificial selection usually affect the fish's life history. Selection can induce different chances of reproduction, and individual fish can give a different genetic contribution to the next generation. In this study, analysis of time-dependent probability of significance and test of sensitivity were used to explore the effects of fish exploitation rate, mesh size, and heritability with long-term trawling. Results showed that fishing parameters were important drivers to exploited fish population. However, genetic traits altered by fishing were slow, and the changes in biological characteristics were weaker than those caused by fishing selection. Exploitation rate and mesh size exhibited similar evolutionary trend tendency under long-term fishing. The time-dependent probability of significance trend showed a gradual growth and tended to be stable. Therefore, the direction of fishing-induced evolution and successful management of fish species require considerable attention to contribute to sustainable fisheries in China.

Evolutionary history and climate conditions constrain the flower colours of woody plants in China

In this study,we investigated(i)the differences in flower colour composition among growth forms of woody plants in China and(ii)the influences of biogeographic regions,evolutionary age and climatic conditions on geographic variation in the proportions of different flower colours.Using distribution maps and flower colour information(white,red,yellow,yellow-green,green and blue-purple)of 7673 Chinese woody plant species and a dated genus-level phylogenetic tree,we compared flower colour composition among different growth forms(shrubs,trees and lianas).We further estimated the relationships of geographical patterns in the proportions of different flower colours with seven different biogeographic regions,evolutionary age and different contemporary climatic variables.Compared with trees or lianas,shrubs showed a higher proportion of species with anthocyanin-based red and blue-purple flowers.The geographic patterns of flower colour composition of woody plants in China were strongly influenced by regional effects and contemporary climate,especially precipitation and ultraviolet B irradiance.The proportion of species with presumably bee-pollinated yellow and blue-purple flowers and stress tolerant anthocyanin-based red and blue-purple flower colours tended to be high in the northwestern part of China.Green flowers tended to evolve earlier than others,but evolutionary age had quite weak influences on the geographic pattern of flower colours.Our results reflect both evolutionary and environmental constraints on the distribution of flower colours of woody plants in China.