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1. Global species delimitation and phylogeography of the circumtropical ‘sexy shrimp’ Thor amboinensis reveals a cryptic species complex and secondary contact in the Indo‐West Pacific

   https://doi.org/10.1111/jbi.13231  

   Titus, Benjamin M. ; Daly, Marymegan ; Hamilton, Natalie ; Berumen, Michael L. ; Baeza, J. Antonio ( April 2018 , Journal of Biogeography)

   The “sexy shrimp”Thor amboinensisis currently considered a single circumtropical species. However, the tropical oceans are partitioned by hard and soft barriers to dispersal, providing ample opportunity for allopatric speciation. Herein, we test the null hypothesis thatT. amboinensisis a single global species, reconstruct its global biogeographical history, and comment on population‐level patterns throughout the Tropical Western Atlantic.

   Coral reefs in all tropical oceans.

   Specimens ofThor amboinensiswere obtained through field collection and museum holdings. We used one mitochondrial (COI) and two nuclear (NaK, enolase) gene fragments for global species delimitation and phylogenetic analyses (n = 83 individuals, 30 sample localities), while phylogeographical reconstruction in theTWAwas based onCOIonly (n = 303 individuals, 10 sample localities).

   We found evidence for at least five cryptic lineages (9%–22%COIpairwise sequence divergence): four in the Indo‐West Pacific and one in the Tropical Western Atlantic. Phylogenetic reconstruction revealed that endemic lineages from Japan and the South Central Pacific are more closely related to the Tropical Western Atlantic lineage than to a co‐occurring lineage that is widespread throughout the Indo‐West Pacific. Concatenated and species tree phylogenetic analyses differ in the placement of an endemic Red Sea lineage and suggest alternate dispersal pathways into the Atlantic. Phylogeographical reconstruction throughout the Tropical Western Atlantic reveals little genetic structure over more than 3,000 km.

   Thor amboinensisis a species complex that has undergone a series of allopatric speciation events and whose members are in secondary contact in the Indo‐West Pacific. Nuclear‐ and mitochondrial‐ gene phylogenies show evidence of introgression between lineages inferred to have been separated more than 20 Ma. Phylogenetic discordance between multi‐locus analyses suggest thatT. amboinensisoriginated in the Tethys sea and dispersed into the Atlantic and Indo‐West Pacific through the Tethys seaway or, alternatively, originated in the Indo‐West Pacific and dispersed into the Atlantic around South Africa. Population‐level patterns in the Caribbean indicate extensive gene flow across the region.

    

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2. Extrinsically reinforced hybrid speciation within Holarctic ermine ( Mustela spp.) produces an insular endemic

   https://doi.org/10.1111/ddi.13234  

   Colella, Jocelyn P. ; Frederick, Lindsey M. ; Talbot, Sandra L. ; Cook, Joseph A. ; Brito, ed., José ( February 2021 , Diversity and Distributions)

   Refugial isolation during glaciation is an established driver of speciation; however, the opposing role of interglacial population expansion, secondary contact, and gene flow on the diversification process remains less understood. The consequences of glacial cycling on diversity are complex and especially so for archipelago species, which experience dramatic fluctuations in connectivity in response to both lower sea levels during glacial events and increased fragmentation during glacial recession. We test whether extended refugial isolation has led to the divergence of genetically and morphologically distinct species within Holarctic ermine (Mustela erminea), a small cosmopolitan carnivore species that harbours 34 extant subspecies, 14 of which are insular endemics.

   Holarctic.

   We use genetic sequences (complete mitochondrial genomes, four nuclear genes) from >100 ermine (stoats) and geometric morphometric data for >200 individuals (27 of the 34 extant subspecies) from across their Holarctic range to provide an integrative perspective on diversification and endemism across this complex landscape. Multiple species delimitation methods (iBPP,bPTP) assessed congruence between morphometric and genetic data.

   Our results support the recognition of at least three species within theM. ermineacomplex, coincident with three of four genetic clades, tied to diversification in separate glacial refugia. We found substantial geographic variation within each species, with geometric morphometric results largely consistent with historical infraspecific taxonomy.

   Phylogeographic structure mirrors patterns of diversification in other Holarctic species, with a major Nearctic‐Palearctic split, but with greater intraspecific morphological diversity. Recognition of insular endemic speciesM. haidarumis consistent with a deep history of refugial persistence and highlights the urgency of mindful management of island populations along North America's North Pacific Coast. Significant environmental modification (e.g. industrial‐scale logging, mining) has been proposed for a number of these islands, which may elevate the risk of extinction of insular palaeoendemics.

    

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3. Cladocopium community divergence in two Acropora coral hosts across multiple spatial scales

   https://doi.org/10.1111/mec.15668  

   Davies, Sarah W. ; Moreland, Kelsey N. ; Wham, Drew C. ; Kanke, Matt R. ; Matz, Mikhail V. ( October 2020 , Molecular Ecology)

   Many broadly‐dispersing corals acquire their algal symbionts (Symbiodiniaceae) “horizontally” from their environment upon recruitment. Horizontal transmission could promote coral fitness across diverse environments provided that corals can associate with divergent algae across their range and that these symbionts exhibit reduced dispersal potential. Here we quantified community divergence ofCladocopiumalgal symbionts in two coral host species (Acropora hyacinthus, Acropora digitifera) across two spatial scales (reefs on the same island, and between islands) across the Micronesian archipelago using microsatellites. We find that both hosts associated with a variety of multilocus genotypes (MLG) within two genetically distinctCladocopiumlineages (C40, C21), confirming thatAcroporacoral hosts associate with a range ofCladocopiumsymbionts across this region. Both C40 and C21 included multiple asexual lineages bearing identical MLGs, many of which spanned host species, reef sites within islands, and even different islands. Both C40 and C21 exhibited moderate host specialization and divergence across islands. In addition, within every island, algal symbiont communities were significantly clustered by both host species and reef site, highlighting that coral‐associatedCladocopiumcommunities are structured across small spatial scales and within hosts on the same reef. This is in stark contrast to their coral hosts, which never exhibited significant genetic divergence between reefs on the same island. These results support the view that horizontal transmission could improve local fitness for broadly dispersingAcroporacoral species.

    

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4. Life on the edge: Hawaiian model for coral evolution

   https://doi.org/10.1002/lno.12181  

   Bhattacharya, Debashish ; Stephens, Timothy G. ; Tinoco, Amanda I. ; Richmond, Robert H. ; Cleves, Phillip A. ( July 2022 , Limnology and Oceanography)

   Degradation and loss of coral reefs due to climate change and other anthropogenic stressors has fueled genomics, proteomics, and genetics research to investigate coral stress response pathways and to identify resilient species, genotypes, and populations to restore these biodiverse ecosystems. Much of the research and conservation effort has understandably focused on the most taxonomically rich regions, such as the Great Barrier Reef in Australia and the Coral Triangle in the western Pacific. These ecosystems are analogous to tropical rainforests that also house enormous biodiversity and complex biotic interactions among different trophic levels. An alternative model ecosystem for studying coral reef biology is the relatively species poor but abundant coral reefs in the Hawaiian Archipelago that exist at the northern edge of the Indo‐Pacific coral distribution. The Hawaiian Islands are the world's most isolated archipelago, geographically isolated from other Pacific reef systems. This region houses about 80 species of scleractinian corals in three dominant genera (Porites,Montipora, andPocillopora). Here we briefly review knowledge about the Hawaiian coral fauna with a focus on our model species, the rice coralMontipora capitata. We suggest that this simpler, relatively isolated reef system provides an ideal platform for advancing coral biology and conservation using multi‐omics and genetic tools.

    

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5. New approaches to species delimitation and population structure of anthozoans: Two case studies of octocorals using ultraconserved elements and exons

   https://doi.org/10.1111/1755-0998.13241  

   Erickson, Katie L. ; Pentico, Alicia ; Quattrini, Andrea M. ; McFadden, Catherine S. ( September 2020 , Molecular Ecology Resources)

   As coral populations decline worldwide in the face of ongoing environmental change, documenting their distribution, diversity and conservation status is now more imperative than ever. Accurate delimitation and identification of species is a critical first step. This task, however, is not trivial as morphological variation and slowly evolving molecular markers confound species identification. New approaches to species delimitation in corals are needed to overcome these challenges. Here, we test whether target enrichment of ultraconserved elements (UCEs) and exons can be used for delimiting species boundaries and population structure within species of corals by focusing on two octocoral genera,AlcyoniumandSinularia, as exemplary case studies. We designed an updated bait set (29,181 baits) to target‐capture 3,023 UCE and exon loci, recovering a mean of 1,910 ± 168SDper sample with a mean length of 1,055 ± 208 bp. Similar numbers of loci were recovered fromSinularia(1,946 ± 227SD) andAlcyonium(1,863 ± 177SD). Species‐level phylogenies were highly supported for both genera. Clustering methods based on filtered single nucleotide polymorphisms delimited species and populations that are congruent with previous allozyme, DNA barcoding, reproductive and ecological data forAlcyonium, and offered further evidence of hybridization among species. ForSinularia, results were congruent with those obtained from a previous study using restriction site associated DNA sequencing. Both case studies demonstrate the utility of target‐enrichment of UCEs and exons to address a wide range of evolutionary and taxonomic questions across deep to shallow timescales in corals.

    

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