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Aim: Rare species make substantial contributions to coastal ecosystem functions. Functional rarity (FR) and phylogenetic rarity (PR) are important features for biodiversity conservation. This work aimed to discuss the necessity and reasonableness of conserving fish FR and PR in coastal seas. Location: China. Methods: By compiling historical fish investigation data, joint species distribution modelling (JSDM) was applied to model fish communities in coastal China Seas. Biogeographic patterns of FR and PR were explored, and the effectiveness of current MPA networks in terms of match/mismatch with the hotspots of rarity was assessed. Results: A total of 44 functionally rare species and 22 phylogenetically rare species were identified. Six of these species were both functionally and phylogenetically rare, and only one was listed as endangered on the Red List of the International Union for Conservation of Nature (IUCN). Functional rarity hotspots covered 10.27% of the coastal areas, which geographically converged in the southern and eastern coast of Taiwan, the Yangtze River Estuary and the Yellow River Estuary. Phylogenetic rarity hotspots only covered 3.06% of the coastal areas, which were sporadically distributed in the coastal East China Sea, the Bohai Sea and the northern Yellow Sea. Current marine‐protected areas (MPAs) only represented 16.16% of the FR hotspots and 20.48% of the PR hotspots, indicating substantial mismatched areas between the MPAs and the hotspots of FR and PR. Main Conclusions: Only considering threatened species in conservation practices will omit functionally and phylogenetically rare species because FR and PR are not necessarily correlated with species threat status on the IUCN Red List. Functional rarity hotspots do not necessarily overlap with PR hotspots, and current MPAs mismatch the majority of these areas. We therefore advocate that conservation prioritization and expansion of MPA networks should account for FR and PR both at the species and site levels. [ABSTRACT FROM AUTHOR]

Rhinogobius candidianus is a freshwater goby distributed in north, northwest, west, and south Taiwan, but this species has been introduced to east Taiwan and became dominant. To investigate its native population genetic diversity and structure and evaluate the sources and diversity of translocated populations, the mitochondrial DNA control region and cytochrome b gene (1981 bp) from 220 specimens were analyzed. These results indicated that (1) the east populations originated from two sources in west Taiwan; (2) translocated populations exist in east Taiwan and south Taiwan; (3) many populations have likely been moved secondarily by human intervention; (4) the effective size of the populations had declined greatly; (5) within the native populations, the ancestral populations colonized Taiwan during the land bridge phase in the Pleistocene through north Taiwan; (6) the landform changes in Taiwan shaped the population structure; and (7) the landforms of the coastline during glaciation also shaped the native range. The low‐level genetic diversity, high population differentiation, and population decline greatly suggest the need for resource management and conservation interventions. Four clades (α–δ) should be managed as four distinct evolutionarily significant units, while the translocated populations should be managed as separate management units. Moreover, the translocated populations in east Taiwan should be evaluated and monitored carefully. [ABSTRACT FROM AUTHOR]