The genus Indigofera (Leguminosae) in New Caledonia: two new species and a key for the species

Abstract Indigoferamonieriana M.Pignal & L.P.Queiroz, sp. nov. and Indigoferadumbeana M.Pignal & L.P.Queiroz, sp. nov., two new species from New Caledonia, are described and illustrated. Both new species have been collected for a long time, but most herbarium specimens were named as the Australian species Indigoferaaustralis, even though they clearly stand apart from this species and the other New Caledonian species of the genus. Indigoferamonieriana can be diagnosed by the tall virgate shrubby habit, leaves with an articulate rachis and 7–11 widely obovate to orbiculate leaflets with greyish undersurface and almost invisible venation. Indigoferadumbeana can be recognized by the arborescent habit, leaves with 15–19 elliptical leaflets, small, c. 6 mm long flowers, and ellipsoid seeds. Preliminary IUCN assessments are provided for both species. A key is provided for all species of Indigofera recorded from New Caledonia.


Introduction
New Caledonia is a sui generis French collectivity located in the southwest Pacific Ocean, 1210 km east of Australia. It is an archipelago of about 18,600 km 2 in Melanesia subregion with a mostly subtropical climate. Most of New Caledonia's native vegetation can be classified into three major types: dense rainforests, savannas and maquis vegetation, the latter a kind of low, sclerophyllous, evergreen vegetation largely restricted to ultramafic substrates (Jaffré et al. 2012).
The New Caledonian native flora includes more than 3300 species of seed plants with an extraordinarily rich endemism, including several examples of relictual Gondwanan elements, such as gymnosperms, of which 42 out of 44 native species are endemic (de Laubenfels 1972, Gargominy et al. 2018. The flowering plant families Amborellaceae, Oncothecaceae and Phellinaceae are also restricted to New Caledonia. According to the French taxonomic repository (Gargominy et al. 2018), Leguminosae are represented by 39 genera (5% endemic to the island), 103 species (32% endemic), 6 subspecies and 13 varieties. General endemism in this collectivity is estimated at c. 76.4% (Jaffré 1993) and no doubt many taxa still remain to be described (Morat 2010, Gâteblé et al. 2018. New Caledonia also includes 2008 introduced species (Héquet et al. 2009).
Indigofera L. is a legume genus belonging to the tribe Indigofereae, subfamily Papilionoideae (Schrire 2005, LPWG 2017). The genus is characterized by a combination of the presence of medifixed T-shaped hair, pulvinate leaves, axillary simple racemes, anthers with appendiculate connective, and flowers with an explosive pollen display (Hutchinson 1964;de Kort and Thijsse 1984). Indigofera is the third largest genus in Leguminosae, embracing c. 750 species with a worldwide distribution, but with a major diversity center in Africa and Madagascar (Schrire 2005;Schrire et al. 2009). In Tropical Asia to Pacific region, the genus is represented by c. 100 species with several species endemic to each region (de Kort and Thijsse 1984;Wilson and Rowe 2004;Schrire 2005 Meyer et al. (2006).
The Australian I. australis is commonly cited as occurring in New Caledonia (Guillaumin 1936, Jaffré et al. 2002. However, during fieldwork in New Caledonia, one of us (MP) had the chance to survey plants that match specimens identified as I. australis. After a careful review of morphological variation of all New Caledonian specimens identified as I. australis and their comparison to the Australian ones, we concluded that they belong to the two new species described in this work and that I. australis does not occur in New Caledonia.

Plant material
We studied the material kept at the National Herbarium of Paris (P) and the IRD herbarium of New Caledonia in Nouméa (NOU).

Measurements, observations and abbreviations
We used the tool "collaboratoire" of the national French infrastructure e-ReColNat (ANR-11-INBS-0004) for specimen comparisons. All measurements were taken on adult structures. We took measurements using a stereomicroscope, based only on fully developed and mature organs from dried specimens except for rehydrated floral parts. Extremes of variation are presented in descriptions. Virtual herbarium can be consulted on the research infrastructure RECOLNAT (https://explore.recolnat.org/ search/botanique/type=index), P herbarium (https://science.mnhn.fr/institution/ mnhn/collection/p//list?lang=en_US) and NOU herbarium (http://herbier-noumea. plantnet-project.org/list.php).
We used the following abbreviations in examined material to indicate the phenological state of the specimen: bt. (with flower buds); fl. (flowering); fr. (fruiting).

Geographical tools
The distribution map was generated in ArcGis 9.3 software (ESRI 2008), based on data from specimen labels. For old material where the coordinates do not appear, data points were calculated from the data on the specimen labels with the help of the site https://www.geoportail.gouv.fr/carte. The extent of occurrence (EOO) and area of occupancy (AOO) were assessed using GeoCat (Geospatial Conservation Assessment Tool; Bachman et al. 2011) and the preliminary conservation status was assessed using IUCN (2017) criteria. Status will be submitted to IUCN New Caledonian Red List Authority to validate it and make an official IUCN assessment.
Conservation status. Indigofera monieriana was provisionally assessed as vulnerable based on IUCN (2017) criterium B as it presents a restricted EOO (7070 km 2 ) and AOO (32 km 2 ), and its estimated range covers about half of New Caledonia's main island.
Discussion. Guillaumin (1936) noted that several virgate specimens from New Caledonia could not be reported to the typical Indigofera australis and he preferred to determine them as I. australis var. gracilis DC. However, a careful examination of the type collection of this variety (Sieber Fl. Novae. Holl. 380, G, K, P) shows that the New Caledonian material is clearly distinguished from I. australis by the less numerous leaflets (5-9 vs. 17-25 in I. australis), mostly obovate with an emarginate apex, lower surface whitish or greyish green and inconspicuous venation (vs. leaflets mostly elliptical with acute to rounded apex, green lower surface and raised venation; see Table 1 for further distinctive characters). Besides, I. australis is restricted to Australia and, although presenting a broad morphological variation (Wilson and Rowe 2010), Calyx 5-lobate, the two upper lobes very short; petals white; standard petal patent, keel petals obovate.
Calyx 5-lobate, the lower lobe as long as or longer than the tube standard petal straight keel petals narrowly obovate.
Calyx 5-lobed, the lower lobe much shorter than the tube; petals pink to red; standard petal straight, keel petals oblong with a 90° upcurved apex.

Pod
Pod straight; endocarp forming translucent envelopes around the seeds; seeds rectangular and arranged linearly.
Pod slightly sinuous; endocarp forming translucent envelopes around the seeds; seeds ellipsoid and arranged linearly.
Pod straight; endocarp forming translucent envelopes around the seeds; seeds rectangular and arranged linearly.

Indigofera dumbeana
Distribution and habitat. Indigofera dumbeana grows in lowland forests, mostly in wood edges areas (fide Veillon 7138, P and Veillon 7482, P). Phenology. Flowering in March and April, fruiting in May to November. Etymology. The specific epithet refers to the Dumbéa River in the mouth of which B. Balansa collected the type material.
Conservation status. We assessed I. dumbeana as endangered both because it presents small EOO (2358 km 2 ) and AOO (20 km 2 ), and it is located rather in sclerophyllous forests that are perhaps the most endangered formations in New Caledonia, especially at low elevation (Bouchet et al. 1995). Additionally, this species is known by few and rather old collections which could indicate its rarity in the island.
Discussion. We agree with B. Schrire who annotated in 2004 the P00379654 specimen (M. Debray 2296) as a new species allied to I. australis Willd. Specimens of Indigofera dumbeana were previously referred to I. australis by Guillaumin (1936). These species are clearly rendered distinct by the habit as I. dumbeana presents plagiotropical, almost horizontal branches, stipules triangular or asymmetrical and falciform (vs. linear), and flowers with a five lobate calyx and white petals (vs. flowers with a truncate calyx and pink to purple petals). Indigofera dumbeana is more similar to I. zollingeriana, both occurring as a tall shrub or small tree habit with plagiotropical branches, but they are clearly distinct by the fruit straight with rectangular seeds linearly arranged (vs. fruit sinuous with transversely compressed seeds arranged like a stack of coins in I. zollingeriana). Additionally, they present important differences in leaf and flower traits as presented in Table 1