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Abstract Members of the genusChondrusare well-known from temperate and cold waters.Chondrus ocellatusHolmes was reported from Hawai‘i Island (19° N latitude) in 1999 as a new record based on vegetative and tetrasporangial characteristics. The first specimens were collected by Setchell in 1900 in Hilo, HI. The presence of aChondrusspecies in the subtropics has been a phycological enigma for over 100 years. We addressed the question of species identity and biogeographic affinities of the HawaiianChondruswith fresh cystocarpic material, DNA samples, and phylogenetic analyses. Analysis and comparison of five genes (nuclear: EF2; plastid:psbA,rbcL, and 23S/UPA; mitochondrial: COI) from HawaiianChondrusand holotype and topotype material of 10 of the 11 acceptedChondrusspecies indicate that Hawaiian specimens areC. retortusMatsumotoetShimada. However, unlike type material, the Hawaiian specimens are commonly pinnulate, vary significantly in secondary medullary filament density, and have mature cystocarps filling the entire medullary space. This study shows the value of using multi-gene loci and comparing multiple sequences of several species to confirm taxonomic conclusions. Our findings suggest thatC. retortusmay have immigrated via rafting on natural floating material or on ships’ hulls. Solving this old puzzle adds new insight into Hawaiian phytogeography.
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Allopolyploid origin and diversification of the Hawaiian endemic mints
Abstract Island systems provide important contexts for studying processes underlying lineage migration, species diversification, and organismal extinction. The Hawaiian endemic mints (Lamiaceae family) are the second largest plant radiation on the isolated Hawaiian Islands. We generated a chromosome-scale reference genome for one Hawaiian species,Stenogyne calaminthoides, and resequenced 45 relatives, representing 34 species, to uncover the continental origins of this group and their subsequent diversification. We further resequenced 109 individuals of twoStenogynespecies, and their purported hybrids, found high on the Mauna Kea volcano on the island of Hawai’i. The three distinct Hawaiian genera,Haplostachys,Phyllostegia, andStenogyne, are nested inside a fourth genus,Stachys. We uncovered four independent polyploidy events withinStachys, including one allopolyploidy event underlying the Hawaiian mints and their direct western North American ancestors. While the Hawaiian taxa may have principally diversified by parapatry and drift in small and fragmented populations, localized admixture may have played an important role early in lineage diversification. Our genomic analyses provide a view into how organisms may have radiated on isolated island chains, settings that provided one of the principal natural laboratories for Darwin’s thinking about the evolutionary process.
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- Award ID(s):
- 2139311
- PAR ID:
- 10511254
- Publisher / Repository:
- Nature Communications
- Date Published:
- Journal Name:
- Nature Communications
- Volume:
- 15
- Issue:
- 1
- ISSN:
- 2041-1723
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1038/s41467-024-47247-y
