Abstract
Eleven of eighteen Society Island Partula species endemic to the Windward Island subgroup (Moorea and Tahiti) have been extirpated by an ill‐advised biological control program. The conservation status of this critically endangered tree snail radiation is of considerable import, but is clouded by taxonomic uncertainty due to the extensive lack of congruence among species designations, diagnostic morphologies, and molecular markers. Using a combination of museum, captive, and remnant wild snails, we obtained the first high‐resolution nuclear genomic perspective of the evolutionary relationships and survival of fourteen Windward Island Partula species, totaling 93 specimens. We analyzed ~1,607–28,194 nuclear genomic loci collected with the double digest restriction‐site associated sequencing method. Results from phylogenomic trees, species estimation, and population assignment tests yielded monophyly of the Windward Island subgroup. Within this group, two well‐supported clades encompassing five species complexes were recovered. Clade 1 was restricted to Tahiti and contained two species complexes: “P. affinis” (three species) and “P. otaheitana” (five species). Clade 2 occurred on Moorea and on Tahiti and consisted of three species complexes: one Tahitian, “P. clara/P. hyalina”; the other two, “P. taeniata” (three species) and “P. suturalis” (six species), Moorean. Our genomic results largely corroborated previous mitochondrial DNA survival estimates for Moorea and Tahiti, with all five species complexes having members surviving in captivity and/or as remnant wild populations, although the details vary in each case. Continued, proactive conservation and management may yet ensure a phylogenetically representative survival of the fabled Partula species of Moorea and Tahiti.
Highlights
Over the past hundred years, the partulid tree snails of the Society Islands attained scientific prominence as the subject of classic studies in zoology, population biology, and evolutionary genetics (Crampton, 1916, 1932; Johnson, Murray, & Clarke, 1993a; Murray & Clarke, 1980; Murray, Clarke, & Johnson, 1993)
The overall number of loci increased across the three similarity thresholds presumably due to homologous reads splitting into multiple loci at high stringency (90% and 95%) thresholds
We identified 1,607–28,194 nuclear genomic loci across the nine ddRADseq datasets for Society Island Partula species
Summary
Over the past hundred years, the partulid tree snails of the Society Islands attained scientific prominence as the subject of classic studies in zoology, population biology, and evolutionary genetics (Crampton, 1916, 1932; Johnson, Murray, & Clarke, 1993a; Murray & Clarke, 1980; Murray, Clarke, & Johnson, 1993). A subset of Partula tree snails collectively persists in captivity (N = 13 spp.; Figure 1a; Gerlach, 2016; Pearce‐Kelly, Clarke, Walker, & Atkin, 1997) and in the wild in cool, cloud forest montane refuges (N = 4, P. meyeri on Raiatea and P. compressa, P. laevigata, and P. otaheitana on Tahiti) where E. rosea may be less effective (Gerlach, 1994, 2016; Lee et al, 2009; Lee, Burch, Jung et al, 2007; Lee, Meyer, Burch, Pearce‐ Kelly, & Ó Foighil, 2008) or as scattered remnant surviving valley populations on Tahiti (N = 3, P. affinis, P. clara, and P. hyalina) and Moorea (P. taeniata; Coote, 2007; Lee et al, 2009; see Table 1 and Supporting Information Table S1). Given the taxonomic uncertainties and the limitations of the mt phylogenies, we still lack a robust understanding of what fraction of the original Windward Islands radiation has persisted These fundamental gaps in our knowledge significantly impair our ability to understand the evolutionary history of these critically endangered taxa and to design optimal conservation management programs and strategies to aid their survival. We analyzed ~1,607–28,194 nuclear genomic loci from a combination of museum, captive, and remnant wild specimens which allowed us to compare relationships
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