Target Enrichment and Extensive Population Sampling Help Untangle the Recent, Rapid Radiation of Oenothera Sect. Calylophus.

Oenothera sect. Calylophus is a North American group of 13 recognized taxa in the evening primrose family (Onagraceae) with an evolutionary history that may include independent origins of bee pollination, edaphic endemism, and permanent translocation heterozygosity. Like other groups that radiated relatively recently and rapidly, taxon boundaries within Oenothera sect. Calylophus have remained challenging to circumscribe. In this study, we used target enrichment, flanking noncoding regions, gene tree/species tree methods, tests for gene flow modified for target-enrichment data, and morphometric analysis to reconstruct phylogenetic hypotheses, evaluate current taxon circumscriptions, and examine character evolution in Oenothera sect. Calylophus. Because sect. Calylophus comprises a clade with a relatively restricted geographic range, we were able to extensively sample across the range of geographic, edaphic, and morphological diversity in the group. We found that the combination of exons and flanking noncoding regions led to improved support for species relationships. We reconstructed potential hybrid origins of some accessions and note that if processes such as hybridization are not taken into account, the number of inferred evolutionary transitions may be artificially inflated. We recovered strong evidence for multiple evolutionary origins of bee pollination from ancestral hawkmoth pollination, edaphic specialization on gypsum, and permanent translocation heterozygosity. This study applies newly emerging techniques alongside dense infraspecific sampling and morphological analyses to effectively reconstruct the recalcitrant history of a rapid radiation. [Gypsum endemism; Oenothera sect. Calylophus; Onagraceae; phylogenomics; pollinator shift; recent radiation; target enrichment.].

A molecular phylogeny of the Pacific clade of Cyrtandra (Gesneriaceae) reveals a Fijian origin, recent diversification, and the importance of founder events.

Cyrtandra (Gesneriaceae) is among the largest genera of flowering plants in the remote oceanic islands of the Pacific, with an estimated 175 species distributed across an area that extends from the Solomon Islands, east to the Marquesas Islands, and north to the Hawaiian Islands. The vast majority of species are single-island endemics that inhabit upland rainforests. Although previous molecular phylogenetic studies greatly advanced our understanding of the diversification of Pacific Cyrtandra, a number of uncertainties remain regarding phylogenetic relationships, divergence times, and biogeographic patterns within this large and widely dispersed group. In the present study, five loci (ITS, ETS, Cyrt1, psbA-trnH, and rpl32-trnL) were amplified and sequenced for phylogenetic reconstruction of 121 Cyrtandra taxa. Maximum likelihood and Bayesian inference confirmed that C. taviunensis from Fiji is sister to the remaining members of the Pacific clade. Dating analyses and ancestral area estimation indicates that the Pacific clade of Cyrtandra originated in Fiji during the Miocene ca. 9mya. All major crown lineages within the Pacific clade appeared < 5mya, coincident with the emergence of numerous Pacific islands and a subsequent increase in available habitat. The biogeographic history of Cyrtandra in the Pacific has been shaped by extinction, dispersal distance, and founder events. Biogeographic stochastic mapping analyses suggest that cladogenesis within Pacific Cyrtandra involved a combination of narrow (within-area) sympatry and founder events. A mean of 24 founder events was recovered between Pacific archipelagos, while a mean of 10 founder events was recovered within the Hawaiian archipelago.

A molecular phylogeny of Acronychia, Euodia, Melicope and relatives (Rutaceae) reveals polyphyletic genera and key innovations for species richness.

We present the first detailed phylogenetic study of the genus Melicope, the largest genus of the Citrus family (Rutaceae). The phylogenetic analysis sampled about 50% of the 235 accepted species of Melicope as well as representatives of 26 related genera, most notably Acronychia and Euodia. The results based on five plastid and nuclear markers have revealed that Acronychia, Euodia and Melicope are each not monophyletic in their current circumscriptions and that several small genera mainly from Australia and New Caledonia need to be merged with one of the three genera to ensure monophyly at the generic level. The phylogenetic position of the drupaceous Acronychia in relation to Melicope, which has capsular or follicular fruits, remains unclear and Acronychia might be a separate genus or a part of Melicope. The seed coats of Melicope, Acronychia and related genera show adaptations to bird-dispersal, which might be regarded as key innovations for species radiations. Euodia and its relatives, which lack these adaptations, include only about 20 species while the Melicope-Acronychia group consists of about 340 species. The drupaceous genera Comptonella, Dutaillyea, Picrella and Sarcomelicope are nested within Melicope and need to be merged with Melicope. The expanded genus is a prime example of the artificial classification system of Engler, who defined Rutaceous subfamilies mainly based on gynoecial and fruit characters.

Cyrtandraobliquifolia (Gesneriaceae), a new species from Kaua'i, Hawaiian Islands.

Cyrtandraobliquifolia K.R. Wood & W.L. Wagner (Gesneriaceae), a new shrub species known only from Kaua'i, Hawaiian Islands, is described and illustrated with notes on its distribution, ecology, and conservation status. The new species is morphologically most similar to Cyrtandrawawrae C.B. Clarke but differs by its unique combination of oblique, non-peltate, auriculate leaf bases, more deeply divided calyx lobes, inflorescence with fewer flowers and lacking profusely umbellate cymes. Cyrtandraobliquifolia is known from only two localities which have undergone severe habitat degradation from landslides and invasive plants and animals and is determined to be Critically Endangered (CR) when evaluated under IUCN criteria.

 Myrsinecirrhosa (Primulaceae), a distinctive new shrub species from Kaua'i, Hawaiian Islands.

Myrsinecirrhosa Lorence & K.R.Wood (Primulaceae), a new single-island endemic shrub species from Kaua'i, Hawaiian Islands, is described and illustrated. Notes on its distribution, ecology and conservation status are included. The new species is known from an area with ca. 45 individuals, where it is restricted to the remote central windward region of Kaua'i in open bogs and along open windy ridges. Suggested IUCN Red List status is CR (Critically Endangered). It differs from its Kaua'i congeners by its longer petals and narrowly elliptic leaves with strongly undulate margins and tendril-like apex. Phylogenetic analysis using RADseq data supports the recognition of this new species.

Clermontiahanaulaensis (Campanulaceae, Lobelioideae), a new, critically endangered species from Maui, Hawaiian Islands.

Clermontiahanaulaensis H.Oppenheimer, Lorence & W.L.Wagner, sp. nov., a newly discovered, narrowly distributed endemic species, is herein described based on its morphological characteristics and illustrated with field photos and a line drawing. It is currently known only from the slopes of Hana'ula, in Pohakea Gulch, Mauna Kahalawai, west Maui, Hawaiian Islands. It differs from all other species of Clermontia Gaudich. by the combination of its (2)3-4(-5) flowered inflorescence, violet colored perianth often suffused with creamy white streaks or sometimes creamy white with violet-purple irregular veins, (30)35-45(-50) mm long, perianth tube 15-25(-27) mm long, 9-10 mm wide, the lobes 20-26 mm long, (2-)3-3.5 mm wide, with petaloid calyx lobes 1/2-4/5 as long as the petals. A key to the Clermontia species and subspecies occurring on Maui is provided. Its habitat is described. Its conservation status is proposed as critically endangered (CR), and conservation efforts are discussed.

A phylogeny of the evening primrose family (Onagraceae) using a target enrichment approach with 303 nuclear loci.

BACKGROUND: The evening primrose family (Onagraceae) includes 664 species (803 taxa) with a center of diversity in the Americas, especially western North America. Ongoing research in Onagraceae includes exploring striking variation in floral morphology, scent composition, and breeding system, as well as the role of these traits in driving diversity among plants and their interacting pollinators and herbivores. However, these efforts are limited by the lack of a comprehensive, well-resolved phylogeny. Previous phylogenetic studies based on a few loci strongly support the monophyly of the family and the sister relationship of the two largest tribes but fail to resolve several key relationships. RESULTS: We used a target enrichment approach to reconstruct the phylogeny of Onagraceae using 303 highly conserved, low-copy nuclear loci. We present a phylogeny for Onagraceae with 169 individuals representing 152 taxa sampled across the family, including extensive sampling within the largest tribe, Onagreae. Deep splits within the family are strongly supported, whereas relationships among closely related genera and species are characterized by extensive conflict among individual gene trees. CONCLUSIONS: This phylogenetic resource will augment current research projects focused throughout the family in genomics, ecology, coevolutionary dynamics, biogeography, and the evolution of characters driving diversification in the family.

Evaluating multiple criteria for species delimitation: an empirical example using Hawaiian palms (Arecaceae: Pritchardia).

BACKGROUND: Robust species delimitations are fundamental for conservation, evolutionary, and systematic studies, but they can be difficult to estimate, particularly in rapid and recent radiations. The consensus that species concepts aim to identify evolutionarily distinct lineages is clear, but the criteria used to distinguish evolutionary lineages differ based on the perceived importance of the various characteristics of evolving populations. We examined three different species-delimitation criteria (monophyly, absence of genetic intermediates, and diagnosability) to determine whether currently recognized species of Hawaiian Pritchardia are distinct lineages. RESULTS: Data from plastid and nuclear genes, microsatellite loci, and morphological characters resulted in various levels of lineage subdivision that were likely caused by differing evolutionary rates between data sources. Additionally, taxonomic entities may be confounded because of the effects of incomplete lineage sorting and/or gene flow. A coalescent species tree was largely congruent with the simultaneous analysis, consistent with the idea that incomplete lineage sorting did not mislead our results. Furthermore, gene flow among populations of sympatric lineages likely explains the admixture and lack of resolution between those groups. CONCLUSIONS: Delimiting Hawaiian Pritchardia species remains difficult but the ability to understand the influence of the evolutionary processes of incomplete lineage sorting and hybridization allow for mechanisms driving species diversity to be inferred. These processes likely extend to speciation in other Hawaiian angiosperm groups and the biota in general and must be explicitly accounted for in species delimitation.

Schiedeahaakoaensis, a new facultatively autogamous species of Schiedea sect. Mononeura (Caryophyllaceae) from the Hawaiian Islands.

In 2016 during a survey for potential fencing of the Ha'akoa unit on windward Mauna Kea, Hawai'i Island (Hawaiian Islands) a single plant of the genus Schiedea was discovered. No species of the genus had ever been known to occur in this area, and only three species of Schiedea were known previously from Hawai'i Island. Two are vining species and the third is a coastal subshrub. The single plant obviously represented an interesting find, and because the plant was vegetative another visit was scheduled to collect a flowering specimen, but by then the plant had died. Soil taken from the site with seeds in the soil produced two plants, one of which flowered in cultivation in 2021. A study of this individual indicated it was a member of Schiedeasect.Mononeura, characterized by erect to ascending habit, quadrangular stems, seeds not persistent on the placenta and readily dispersing from the dehisced capsule, and flowers facultatively autogamous. With the discovery of this new species there are 35 species in this Hawaiian endemic genus.

Estimating the species tree for Hawaiian Schiedea (Caryophyllaceae) from multiple loci in the presence of reticulate evolution.

Schiedea (Caryophyllaceae) is a monophyletic genus of 34 species, all endemic to the Hawaiian Islands, that arose from a single colonization, providing one of the best examples of adaptive radiation in Hawai'i. Species utilize a range of habitats and exhibit a variety of growth forms and transitions in breeding systems from hermaphroditism toward dimorphism or autogamy. Our study included the most thorough sampling to date: 2-5 individuals per species and 4 independent genetic partitions: eight plastid and three low-copy nuclear loci (9217bps), allowing a three-locus BEST species tree. Despite incomplete resolution at the tips, our results support monophyly for each extant species. Gene trees revealed several clear cases of cytonuclear incongruence, likely created by interspecific introgression. Conflict occurs at the divergence of section Alphaschiedea as well as at the tips. Ages inferred from a BEAST analysis allow an original colonization onto either Nihoa or Kauaì and inform some aspects of inter-island migrations. We suggest that several hard polytomies on the species tree are biologically realistic, signifying either nearly simultaneous speciation or historical introgressive hybridization. Based on inferred node ages that exceed expected coalescent times, we propose that undetected nuclear introgression may play a larger role than incomplete lineage sorting in sections Schiedea and Mononeura.

A phylogenetic basis for species-area relationships among three Pacific Island floras.

PREMISE OF THE STUDY: The angiosperm floras of the Hawaiian, Society, and Marquesas archipelagoes are remarkably comparable ecologically and evolutionarily, a result of similar geologic history, climate, and isolation. METHODS: We characterized variation in species richness among islands and whole archipelagoes by analyzing species-area relationships (SARs). By partitioning each flora into putative phylogenetic lineages each derived from a given colonization event, we explored several ways in which speciation contributes to SARs. KEY RESULTS: Specifically, these groups exhibit expected island SARs and a whole archipelago SAR characterized by a steep slope. The number of species added by net cladogenesis increases with area much more quickly than the number contributed by net colonization from outside. In each of the three archipelagoes, most colonists do not speciate, while many species occur in a few diverse colonist lineages. Colonization events that are unique to a given archipelago are in more prone to speciation than lineages with close relatives in the other archipelagoes. Most lineages with relatives in all three archipelagoes have one species in each, suggesting a similar tendency not to diversify. On the other hand, a correlation between lineage size in one archipelago and that of related lineages in other archipelagoes suggests a consistent tendency among diverse groups to speciate extensively. Lineages with multiple species in each archipelago also tend to have far more species in the largest archipelago, the Hawaiian Islands. CONCLUSIONS: The most diverse lineages exhibit a strong response to archipelago area. These diverse, area-sensitive lineages contribute substantially to the slope of the inter-archipelago SAR. Regional species pools elsewhere may exhibit similar steep-sloped SARs; thus, these findings may inform how the behavior of lineages with different responses to increasing shapes these patterns.

Development of microsatellites in the Hawaiian endemic palm Pritchardia martii (Arecaceae) and their utility in congeners.

PREMISE OF THE STUDY: Pritchardia (loulu palm) is the seventh largest flowering plant genus in the Hawaiian archipelago, and many species are of high conservation concern. The island radiation has produced many cryptic species complexes across fine ecological gradients. Microsatellite primers were optimized to investigate genetic diversity of Pritchardia martii (Gaudich.) H. Wendl. and species boundaries among the Hawaiian Pritchardia. METHODS AND RESULTS: Six new loci and three previously described loci for a closely related genus, Phoenix, were optimized and tested. Five loci were polymorphic, and 72 alleles were detected across loci within P. martii. The five loci were also polymorphic across the other 27 currently recognized Pritchardia species. • CONCLUSIONS: These results indicate the utility of these microsatellite markers for understanding the conservation genetics of P. martii and species delimitation and hybridization across the genus.

Hawaiian angiosperm radiations of North American origin.

BACKGROUND: Putative phytogeographical links between America (especially North America) and the Hawaiian Islands have figured prominently in disagreement and debate about the origin of Pacific floras and the efficacy of long-distance (oversea) plant dispersal, given the obstacles to explaining such major disjunctions by vicariance. SCOPE: Review of past efforts, and of progress over the last 20 years, toward understanding relationships of Hawaiian angiosperms allows for a historically informed re-evaluation of the American (New World) contribution to Hawaiian diversity and evolutionary activity of American lineages in an insular setting. CONCLUSIONS: Temperate and boreal North America is a much more important source of Hawaiian flora than suggested by most 20th century authorities on Pacific plant life, such as Fosberg and Skottsberg. Early views of evolution as too slow to account for divergence of highly distinctive endemics within the Hawaiian geological time frame evidently impeded biogeographical understanding, as did lack of appreciation for the importance of rare, often biotically mediated dispersal events and ecological opportunity in island ecosystems. Molecular phylogenetic evidence for North American ancestry of Hawaiian plant radiations, such as the silversword alliance, mints, sanicles, violets, schiedeas and spurges, underlines the potential of long-distance dispersal to shape floras, in accordance with hypotheses championed by Carlquist. Characteristics important to colonization of the islands, such as dispersibility by birds and ancestral hybridization or polyploidy, and ecological opportunities associated with 'sky islands' of temperate or boreal climate in the tropical Hawaiian archipelago may have been key to extensive diversification of endemic lineages of North American origin that are among the most species-rich clades of Hawaiian plants. Evident youth of flowering-plant lineages from North America is highly consistent with recent geological evidence for lack of high-elevation settings in the Hawaiian chain immediately prior to formation of the oldest, modern high-elevation island, Kaua'i.

Pogostemon guamensis Lorence & W.L.Wagner (Lamiaceae), a new species from Guam, Mariana Islands.

While undertaking a botanical survey of the Andersen Air Force Base on Guam (Mariana Islands) in 1994, botanists from the National Tropical Botanical Garden collected an unusual suffrutescent, non-aromatic member of the Lamiaceae family growing on limestone cliffs in the northeastern part of the island. Based on morphology and molecular data (trnLF, matK), it was determined to belong to the genus Pogostemon Desf., a genus previously unknown from the Micronesian, Melanesian, and Polynesian region. Moreover, the analysis also showed that it was not conspecific with P. cablin (patchouli), and of the species available to include in the phylogenetic analyses it is sister to P. hirsutus¸ a species from India and Sri Lanka. Differing from its congeners by its large, loose inflorescence 2.5-5 cm wide and up to 7 cm wide in fruit, it is here illustrated and described as a new species, Pogostemon guamensis Lorence & W.L. Wagner and its habitat and conservation status are discussed.

Patterns of diversification and ancestral range reconstruction in the southeast Asian-Pacific angiosperm lineage Cyrtandra (Gesneriaceae).

The genus Cyrtandra is the largest in the Gesneriaceae family and is one of the most widely dispersed plant genera in southeast Asia and the Pacific. Species of Cyrtandra are morphologically diverse but characters are often homoplastic causing considerable difficulty in defining monophyletic classification units. In this study, we used molecular phylogenetic analysis of 88 taxa representing approximately 70 species to construct a well-resolved evolutionary hypothesis for Cyrtandra. Diversification rates analysis and ancestral range analysis were also conducted to infer timing of major lineage divergences and geographic origin of these lineages, principally among Pacific species. Using these data, we compared existing classification schemes to better understand the applicability of current taxonomy. Divergence time estimates support a diversification of the Pacific clade at approximately 20 MYBP. Although the origin of the Pacific lineage remains unresolved, ancestral range reconstruction analysis supports Fiji as the most likely "first-step" into the Pacific with subsequent dispersals to Hawai'i, and other archipelagos. A greater Fiji-Samoa region, corresponding with Takhtajan's Fijian Region, is implicated as a major Pacific region interface and possibly a center of origin for expansion of Cyrtandra throughout the Pacific. Among South Pacific taxa sampled, several supported clades in our evolutionary hypothesis are characterized by distinct morphological traits possibly warranting sectional rankings. Relationships among Hawaiian taxa are less resolved and the distributions of species within this clade do not consistently correspond to existing sectional rankings. More detailed, population-level research is needed to clarify these relationships. We argue that future sectional classifications should correspond with monophyletic lineages and that species-level relationships should be more closely studied within these lineages.

Molecular phylogeny, divergence time estimates, and historical biogeography of Circaea (Onagraceae) in the Northern Hemisphere.

Circaea (Onagraceae) consists of eight species and six subspecies distributed in Eurasia and North America. The sister group of Circaea was recently shown to be Fuchsia, which comprises 107 species primarily distributed in montane Central and South America, including four species occurring in the South Pacific islands. Three plastid markers (petB-petD, rpl16, and trnL-F) and nrITS sequences from 13 of the 14 taxa of Circaea were sequenced and used to reconstruct the phylogenetic and biogeographic history of the genus. Parsimony and Bayesian analyses support that (1) Circaea is monophyletic; (2) the bilocular group is a weakly supported clade nested within the unilocular grade; (3) neither the C. alpina complex nor the C. canadensis complex is monophyletic; and (4) the western North American C. alpina subsp. pacifica diverged first in the genus. Divergence time estimates based on the Bayesian "relaxed" clock methods suggest that the earliest Circaea divergence occurred minimally at 16.17 mya (95% HPD: 7.69-24.53 mya). Biogeographic analyses using divergence-vicariance analysis (DIVA) and a likelihood method support the New World origin of Circaea. Three independent dispersal events between Eurasia and North America via the Bering land bridge were inferred within Circaea. Higher taxon diversity of Circaea in eastern Asia was probably caused by geologic and ecological changes during the late Tertiary in the Northern Hemisphere.

A comparative study in ancestral range reconstruction methods: retracing the uncertain histories of insular lineages.

Island systems have long been useful models for understanding lineage diversification in a geographic context, especially pertaining to the importance of dispersal in the origin of new clades. Here we use a well-resolved phylogeny of the flowering plant genus Cyrtandra (Gesneriaceae) from the Pacific Islands to compare four methods of inferring ancestral geographic ranges in islands: two developed for character-state reconstruction that allow only single-island ranges and do not explicitly associate speciation with range evolution (Fitch parsimony [FP; parsimony-based] and stochastic mapping [SM; likelihood-based]) and two methods developed specifically for ancestral range reconstruction, in which widespread ranges (spanning islands) are integral to inferences about speciation scenarios (dispersal-vicariance analysis [DIVA; parsimony-based] and dispersal-extinction-cladogenesis [DEC; likelihood-based]). The methods yield conflicting results, which we interpret in light of their respective assumptions. FP exhibits the least power to unequivocally reconstruct ranges, likely due to a combination of having flat (uninformative) transition costs and not using branch length information. SM reconstructions generally agree with a prior hypothesis about dispersal-driven speciation across the Pacific, despite the conceptual mismatch between its character-based model and this mode of range evolution. In contrast with narrow extant ranges for species of Cyrtandra, DIVA reconstructs broad ancestral ranges at many nodes. DIVA results also conflict with geological information on island ages; we attribute these conflicts to the parsimony criterion not considering branch lengths or time, as well as vicariance being the sole means of divergence for widespread ancestors. DEC analyses incorporated geological information on island ages and allowed prior hypotheses about range size and dispersal rates to be evaluated in a likelihood framework and gave more nuanced inferences about range evolution and the geography of speciation than other methods tested. However, ancestral ranges at several nodes could not be conclusively resolved, due possibly to uncertainty in the phylogeny or the relative complexity of the underlying model. Of the methods tested, SM and DEC both converge on plausible hypotheses for area range histories in Cyrtandra, due in part to the consideration of branch lengths and/or timing of events. We suggest that DEC model-based methods for ancestral range inference could be improved by adopting a Bayesian SM approach, in which stochastic sampling of complete geographic histories could be integrated over alternative phylogenetic topologies. Likelihood-based estimates of ancestral ranges for Cyrtandra suggest a major dispersal route into the Pacific through the islands of Fiji and Samoa, motivating future biogeographic investigation of this poorly known region.

Perrottetiawichmaniorum (Dipentodontaceae), a new species from Kaua'i, Hawaiian Islands.

Perrottetiawichmaniorum Lorence & W. L. Wagner, sp. nov. is described as endemic to Kaua'i. It differs from its Hawaiian congener P.sandwicensis by its larger, thicker, more densely hirtellous-villosulous rugose leaves with a smaller length:width ratio [1.5-1.7:1], larger inflorescences with usually four degrees of branching with moderately to densely hirtellous axes, and flowers with glabrous petals. This new species falls into the Endangered (EN) category when evaluated using the IUCN Red List criteria for endangerment based on its small area of occupancy, a decline in the extent and quality of its habitat, and number of mature individuals.

Phylogeny of Hawaiian Melicope (Rutaceae): RAD-seq Resolves Species Relationships and Reveals Ancient Introgression.

Hawaiian Melicope are one of the major adaptive radiations of the Hawaiian Islands comprising 54 endemic species. The lineage is monophyletic with an estimated crown age predating the rise of the current high islands. Phylogenetic inference based on Sanger sequencing has not been sufficient to resolve species or deeper level relationships. Here, we apply restriction site-associated DNA sequencing (RAD-seq) to the lineage to infer phylogenetic relationships. We employ Quartet Sampling to assess information content and statistical support, and to quantify discordance as well as partitioned ABBA-BABA tests to uncover evidence of introgression. Our new results drastically improved resolution of relationships within Hawaiian Melicope. The lineage is divided into five fully supported main clades, two of which correspond to morphologically circumscribed infrageneric groups. We provide evidence for both ancestral and current hybridization events. We confirm the necessity for a taxonomic revision of the Melicope section Pelea, as well as a re-evaluation of several species complexes by combining genomic and morphological data.

Progressive island colonization and ancient origin of Hawaiian Metrosideros (Myrtaceae).

Knowledge of the evolutionary history of plants that are ecologically dominant in modern ecosystems is critical to understanding the historical development of those ecosystems. Metrosideros is a plant genus found in many ecological and altitudinal zones throughout the Pacific. In the Hawaiian Islands, Metrosideros polymorpha is an ecologically dominant species and is also highly polymorphic in both growth form and ecology. Using 10 non-coding chloroplast regions, we investigated haplotype diversity in the five currently recognized Hawaiian Metrosideros species and an established out-group, Metrosideros collina, from French Polynesia. Multiple haplotype groups were found, but these did not match morphological delimitations. Alternative morphologies sharing the same haplotype, as well as similar morphologies occurring within several distinct island clades, could be the result of developmental plasticity, parallel evolution or chloroplast capture. The geographical structure of the data is consistent with a pattern of age progressive island colonizations and suggests de novo intra-island diversification. If single colonization events resulted in a similar array of morphologies on each island, this would represent parallel radiations within a single, highly polymorphic species. However, we were unable to resolve whether the pattern is instead explained by ancient introgression and incomplete lineage sorting resulting in repeated chloroplast capture. Using several calibration methods, we estimate the colonization of the Hawaiian Islands to be potentially as old as 3.9 (-6.3) Myr with an ancestral position for Kaua'i in the colonization and evolution of Metrosideros in the Hawaiian Islands. This would represent a more ancient arrival of Metrosideros to this region than previous studies have suggested.