Lizards usually exhibit frequent turnovers and a much greater diversity of sex determination mechanisms compared to birds and mammals,with the conserved ZW sex chromosomes of anguimorph lizards originating over 115 mi...Lizards usually exhibit frequent turnovers and a much greater diversity of sex determination mechanisms compared to birds and mammals,with the conserved ZW sex chromosomes of anguimorph lizards originating over 115 million years ago a seeming exception.We previously discovered in an anguimorph lizard Varanus acanthurus(Vac)whose entire chrW,but not chrZ is homologous to part of the chr2 by cytogenetic mapping,suggesting its complex history of sex chromosome evolution yet to be elucidated.To address this,we assemble a chromosome-level genome,and provide evidence that the Vac sex chromosome pair has undergone at least two times of recombination loss,producing a pattern of evolutionary strata like that of birds and mammals.Comparison to other lizard genomes date the stepwise propagation of specific retrotransposon subfamilies enriched near the duplicated gene pairs on the chrW and chr2 to the varanid ancestor.These retrotransposons probably have mediated the recruitment and amplification of autosomal genes on the chrW,including members of a large vomeronasal chemosensory receptor gene family V2R.Our results suggest that the W or Y chromosome as a refugium of repetitive elements,may recurrently recruit short-lived functional genes responsible for sexual dimorphisms during its long-term course of degeneration.展开更多
Although Caribbean mixed-species herbivorous fish groups are an important component to the reef community by helping to crop algae that often overgrow and kill corals, little is known of how they organize their foragi...Although Caribbean mixed-species herbivorous fish groups are an important component to the reef community by helping to crop algae that often overgrow and kill corals, little is known of how they organize their foraging groups. In spite of a highly flexible membership, the basic structure of these groups consists of a “core species,” that leads the group and often is either the striped parrotfish (Scarus iserti) or the ocean surgeon (Acanthurus tractus). These species lead their groups to open areas where they feed largely on low profile turf algae. Other members prefer macro algae and are termed “associate species,” of which the two common species we studied were the stoplight parrotfish (Sparisoma viride) and the redband parrotfish (Sparisoma aurofrenatum). In spite of the large difference in group sizes between Jamaica and Grand Cayman Islands, the relationships between movement patterns and compositional changes were largely consistent. There was no support for the hypothesis that these dramatic and continuous group changes were related to foraging success. Instead, we speculated that these group changes perhaps were designed to maintain cohesion among a membership that was spread over a wide area. We also examined if associates species may be more than just passive followers of core species but rather instigated the attracting or the building of core groups. Both associate species do attract striped parrotfish in open areas and thus appear active in initiating mixed-species groups. Finally, given that associate species seem to derive little foraging benefit from following core species, we tested the hypothesis that associate species joined core groups to gain protection against predators. Associate species do not selectively join the larger groups of striped parrotfish but appear to join core species randomly and the groups they joined resembled the wide assortment of core groups available in the area. Thus, while associates may be joining core groups for protection, this protection was not based on sizes of core groups.展开更多
基金supported by the National Key Research and Development Program of China(2023YFA1800500,2024YFA1802500)the National Natural Science Foundation of China(32170415)+1 种基金supported by the Australian Government Research Training Program(RTP)stipend scholarship.supported by the Australian Research Council Discovery Project grant(ARC DP200101406).
文摘Lizards usually exhibit frequent turnovers and a much greater diversity of sex determination mechanisms compared to birds and mammals,with the conserved ZW sex chromosomes of anguimorph lizards originating over 115 million years ago a seeming exception.We previously discovered in an anguimorph lizard Varanus acanthurus(Vac)whose entire chrW,but not chrZ is homologous to part of the chr2 by cytogenetic mapping,suggesting its complex history of sex chromosome evolution yet to be elucidated.To address this,we assemble a chromosome-level genome,and provide evidence that the Vac sex chromosome pair has undergone at least two times of recombination loss,producing a pattern of evolutionary strata like that of birds and mammals.Comparison to other lizard genomes date the stepwise propagation of specific retrotransposon subfamilies enriched near the duplicated gene pairs on the chrW and chr2 to the varanid ancestor.These retrotransposons probably have mediated the recruitment and amplification of autosomal genes on the chrW,including members of a large vomeronasal chemosensory receptor gene family V2R.Our results suggest that the W or Y chromosome as a refugium of repetitive elements,may recurrently recruit short-lived functional genes responsible for sexual dimorphisms during its long-term course of degeneration.
文摘Although Caribbean mixed-species herbivorous fish groups are an important component to the reef community by helping to crop algae that often overgrow and kill corals, little is known of how they organize their foraging groups. In spite of a highly flexible membership, the basic structure of these groups consists of a “core species,” that leads the group and often is either the striped parrotfish (Scarus iserti) or the ocean surgeon (Acanthurus tractus). These species lead their groups to open areas where they feed largely on low profile turf algae. Other members prefer macro algae and are termed “associate species,” of which the two common species we studied were the stoplight parrotfish (Sparisoma viride) and the redband parrotfish (Sparisoma aurofrenatum). In spite of the large difference in group sizes between Jamaica and Grand Cayman Islands, the relationships between movement patterns and compositional changes were largely consistent. There was no support for the hypothesis that these dramatic and continuous group changes were related to foraging success. Instead, we speculated that these group changes perhaps were designed to maintain cohesion among a membership that was spread over a wide area. We also examined if associates species may be more than just passive followers of core species but rather instigated the attracting or the building of core groups. Both associate species do attract striped parrotfish in open areas and thus appear active in initiating mixed-species groups. Finally, given that associate species seem to derive little foraging benefit from following core species, we tested the hypothesis that associate species joined core groups to gain protection against predators. Associate species do not selectively join the larger groups of striped parrotfish but appear to join core species randomly and the groups they joined resembled the wide assortment of core groups available in the area. Thus, while associates may be joining core groups for protection, this protection was not based on sizes of core groups.
