Heliotropium (Boraginaceae) in the Marquesas Islands (French Polynesia) with description of a new species

Abstract During the preparation of the Vascular Flora of the Marquesas Islands a new endemic species of Heliotropium L. (Boraginaceae) has come to light and is described herein: Heliotropium perlmanii Lorence & W. L. Wagner. It is known only from the island of Eiao and appears most closely related to Heliotropium marchionicum Decne., also endemic to the Marquesas and known from Nuku Hiva. An amended description of Heliotropium marchionicum and key to separate the Marquesan species are given and their differences discussed.


Introduction
Th e Flora of the Marquesas Islands project is a collaborative program primarily between the Smithsonian Institution and the National Tropical Botanical Garden intended to further knowledge of the fl ora of this remote archipelago. In 1997 the fi rst publications of new species and revisions of genera with at least one endemic species were initiated (Florence and Lorence 1997;Wagner and Lorence 1997). Since that time a series of publications has enumerated and revised a number of genera (for summary see Lorence and Wagner 2011). Th is treatment of the Marquesas species of Heliotropium L. is one of the last precursor publications before fi nalizing the data in the online Flora of the Marquesas Islands website (Wagner and Lorence 2002-).
A number of recent studies utilizing both molecular and morphological analyses suggest that the traditional Boraginaceae s.l. should be split into a number of families (see Refulio-Rodriguez and Olmstead 2014 and other papers cited therein). One of the primary reasons for this is that the overall clade is comparable to other nearby clades in the phylogeny that are treated as orders in the classifi cation (Gentianales, Lamiales, and Solanales). Th erefore, the group is being restructured to be a series of families within an order Boraginales. Th is classifi cation would elevate former subfamilies of Boraginaceae to the rank of family (i.e., Boraginaceae, Cordiaceae, Ehretiaceae, and Heliotropiaceae); keep Hydrophyllaceae at the rank of family, but it may need to be split into two families); and recognize two small families, Wellstediaceae (formerly Boraginaceae) and Codonaceae (formerly Hydrophyllaceae). Refulio-Rodriguez and Olmstead (2014) point out that there are still a number of issues to resolve in the phylogeny of Boraginales that will aff ect the fi nal classifi cation of the clade. One issue is that one of the monophyletic groups, tribe Nameae of the Hydrophyllaceae, has no currently available family name. Since the overall new classifi cation of the Boraginales requires further study to fully resolve, including proposal of at least one additional family, it seems premature to adopt it yet. For this reason we here use Boraginaceae in the broad sense for purposes of this contribution to the Flora of the Marquesas Islands project.
Heliotropium (Boraginaceae subfam. Heliotropoideae, or Heliotropiaceae of many authors) consists of 280 to 350 species of herbs, shrubs, lianas and small trees from the temperate and warm regions of the world, mostly in arid zones, with the greatest diversity in the New World (Diane et al. 2002;Luebert et al. 2011;Mabberley 2008;Wagner and Lorence 2002-). Molecular results using ITS1 demonstrated strong support for the Old World species of Heliotropium s. str., but there are no clear morphological characters separating them from their New World sister clade (Diane et al. 2002). Th e systematics of this group remains highly controversial due to the scarcity of informative reproductive characters, i.e. fl oral and fruit morphology, and variability in leaf morphology. Since Pacifi c species were not included in analyses by either Diane et al. (2002) or Luebert et al. (2011), putative origin and affi nities of the Marquesan species are unclear and further investigations are necessary to demonstrate their precise relationships.
In the Marquesas Islands (SE Polynesia) only a single native species, Heliotropium marchionicum Decne. has been previously recorded (Brown 1935, Drake del Castillo 1893), the type of which was collected at an unknown locality on Nuku Hiva island by Le Bastard. Study of Heliotropium collections for preparation of the Vascular Flora of the Marquesas Islands has revealed that the collections from Eiao diff er from H. marchionicum in a number of signifi cant, non-overlapping morphological features including branching of the stems, indument, phyllotaxis, characters of the fl owers, including the annular stigma overtopped by a sterile, conically elongated stigmatic column, and fruits (see key below). For this reason we recognize the collections from Eiao as a new species, Heliotropium perlmanii. Risk evaluation for determination of conservation sta-tus was inferred using IUCN criteria for endangerment (IUCN 2001) based on best available information on suitable habitat and threats, primarily from personal observations by Jean-François Butaud (pers. comm. 2014).
Distribution. Marquesas Islands, known only from three collections made on Eiao.
Etymology. We are pleased to name this new species in recognition of roughterrain botanist Steven P. Perlman (National Tropical Botanical Garden) in recognition of his contributions to our knowledge of the fl ora of the Pacifi c region. Steve collected the type specimen and in his label data noted several diff erences from H. marchionicum.
Distribution. Marquesas Islands, known only from Nuku Hiva.
Habitat. Th is species usually occurs inland on basaltic cliff s and dry ridges, sometimes near waterfalls, in dry land forest with Sapindus saponaria L., Cerbera manghas L., and introduced invasive species including Tecoma stans (L.) Kunth and Leucaena leucocephala (Lam.) De Wit. Th e label on one collection notes it is a low elevation littoral plant (Brown 542,BISH).
Discussion. Heliotropium marchionicum is apparently closely related to H. permanii but diff ers by the characters noted above. A single collection from Taiohae, Nuku Hiva (Florence 8394, BISH, CHR, K, NY, P, US) resembles H. marchionicum superfi cially but diff ers in having stems and petioles pilose with hairs to 1 mm long, infl orescence axis pilose, very small fl owers (calyx lobes 1-1.1 mm long, corolla 1.1-1.3 mm long) and ribbed fruits 1.1-1.2 × 1.8 mm, covered with bulbous-tuberculate scales, splitting into 4 nutlets. Further collections are needed to determine whether it represents an undescribed taxon or alternatively a naturalized species. It closely resembles H. angiospermum Murr., native to North America and the Caribbean and was identifi ed