Seasonal and spatial dynamics of phylogenetic structure of fish communities in coastal waters

Abstract

Understanding community assembly has long attracted the attention of ecologists. There are a lot of studies on how community assembly mechanisms work through phylogenetic analysis. Nevertheless, phylogenetic structures have generally been assumed to be stable over time in most studies, and little attention has been paid to seasonal shifts in phylogenetic structure, which is important to mobile animals. In this study, phylogenetic distance was measured as the mean pairwise distance (MPD) and as mean nearest taxon distance (MNTD). The phylogenetic structures of fish communities in different regions, subregions and at sampling stations were examined using the standardized effect sizes of MPD and MNTD (SES.MPD and SES.MNTD) under null model independent swap over four seasons in the coastal waters of Shandong Province, China. Generalized additive model (GAM) was used to detect which environmental factors have an important impact on phylogenetic structure indices at each sampling station. The fish communities were phylogenetically clustered in most seasons in the whole survey waters, indicating environmental filtering tended to shape the whole fish assemblage. Two phylogenetic indices indicated that the phylogenetic structure (phylogenetic over-dispersion or phylogenetic clustering) was inconsistent on the different regions and subregions. For fish assemblages at each sampling station, the phylogenetic structure of fish communities presented patchy distribution patterns in different seasons. GAM analysis showed that phylogenetic structure responded differently to different environmental factors over four seasons, and the change in phylogenetic structure indices was significantly associated with environmental factors, especially in autumn and winter. SES.MPD can better respond to environmental changes than SES.MNTD. Spatial factors (longitude and latitude) were important factors influencing fish community assembly, indicating that fish communities at offshore stations with low latitude exhibit a relatively high degree of phylogenetic overdispersion. It was difficult to draw consistent conclusions about seasonal changes in phylogenetic structure of fish communities on different temporal and spatial scales. It is possible that seasonal variations and spatial scales in assembly mechanisms contribute to maintaining marine fish diversity in temperate waters, resulting in different phylogenetic structures in fish community.