Olivier Lachenaud

Screening for leaf-associated endophytes in the genus Psychotria (Rubiaceae)

Burkholderia endophytes were identified within the leaves of non-nodulated members of the genus Psychotria. In contrast to leaf-nodulated Psychotria species, which are known to accommodate their endosymbionts into specialized endosymbiont-housing structures, non-nodulated species lack bacterial leaf nodules and harbor endosymbionts intercellularly between mesophyll cells. Based on molecular data (rps16, trnG, and trnLF), the phylogenetic reconstruction of the host plants revealed a separate origin of leaf-nodulated and non-nodulated Psychotria species. Despite a distinct phylogenetic position of the two host clades, the endophytes of the non-nodulated plants were not placed into a single monophyletic group but were found to be closely related to the leaf-nodulated endosymbionts. The observation of genetically similar endophytes in both nodulated and non-nodulated Psychotria lineages suggests that the host plant is playing a crucial role in the induction of leaf nodule formation. Moreover, the concentration of endosymbionts into specialized leaf nodules may be considered as a more derived evolutionary adaptation of the host plant, serving as an interface structure to facilitate metabolic exchange between plant and endosymbiont.

NOVITATES GABONENSES 80. ADDITIONS AND CORRECTIONS TO THE FLORA OF GABON

Since the publication of the Gabon Checklist in 2006, intensive fieldwork activity has led to the discovery of many novelties. We document here 61 new records for the flora of Gabon, including nine new generic records. Five taxa are also removed from the Gabon flora.

Peri-urban conservation in the Mondah forest of Libreville, Gabon: Red List assessments of endemic plant species, and avoiding protected area downsizing

Urban development is an increasing threat to the integrity of formerly remote protected areas, in some cases resulting in their downgrading, downsizing or degazetting. One-quarter of previously remote protected areas are now within 17 km of a city and thus face the threat of urbanization. Here we describe a case of avoided downgrading, downsizing and degazetting of a protected area in the Mondah forest of Gabon, north of Libreville. Since its creation in 1934 the Foret Classee de la Mondah has been downsized regularly, losing 40% of its area over 80 years. During this time the forest surrounding the Foret Classee was subject to usage for urban and peri-urban needs, including agriculture, sand extraction, collection of medicinal plants, ceremonies, and housing construction. In 2010 the area was threatened with further downsizing. The presence of narrowly endemic plant species in the area was suspected, and mapping and evaluation of these species was proposed in an effort to maintain the protected area boundaries. Botanical field work, including ex situ conservation measures and participant observation in nearby forest communities, was conducted; 24 endemic species, all threatened by urbanization, were evaluated using the criteria for the IUCN Red List of Threatened Species. The borders of the protected area were maintained because of its role in maintaining irreplaceable habitat for threatened species. The area was renamed Raponda Walker Arboretum in 2012.

THREE NEW SPECIES OF CHASSALIA AND PSYCHOTRIA (RUBIACEAE) FROM CENTRAL AFRICA

Three new species of Rubiaceae from Central Africa are described and illustrated. Chassalia lutescens O.Lachenaud & D.J.Harris (widespread from Cameroon to Democratic Republic of Congo) is recognised inter alia by the T-shaped ventral furrow of the seeds and the orange-yellow discoloration of inflorescences in herbarium specimens. Psychotria nodiflora O.Lachenaud & D.J.Harris (Central African Republic, Congo-Brazzaville and Democratic Republic of Congo), belonging to Psychotria subgen. Psychotria sect. Involucratae, is unique among African species of the genus in having paired axillary inflorescences. Psychotria pteropus O.Lachenaud & D.J.Harris (Central African Republic and Democratic Republic of Congo) belongs to Psychotria subgen. Tetramerae; it is closely related to P. leptophylla Hiern but differs in its narrow corolla tube and globose to ellipsoid fruits.© 2010 Trustees of the Royal Botanic Garden Edinburgh.

Nine polymorphic microsatellite loci from the psyllid Cacopsylla pruni (Scopoli), the vector of European stone fruit yellows

Cacopsylla pruni is the vector of European stone fruit yellows, a quarantine disease of Prunus trees. Nine polymorphic microsatellite markers were developed from enriched DNA libraries. Allelic variability was assessed in a collection of 149 females obtained from five localities covering a large geographical area in France. The number of detected alleles ranged from 8 to 37. Within the localities, observed and expected heterozygosities averaged across loci ranged from 0.39 to 0.55, and from 0.68 to 0.81, respectively. A heterozygote deficiency was detected for almost all loci, possibly due to a high null allele frequency. Other possible causes of the homozygote excess (mode of reproduction, inbreeding, assortative mating or Wahlund effect) are discussed. These variable microsatellite loci can provide tools to assess overall genetic variation in this important vector species. They will be used to search for population structure and migration patterns of C. pruni.

Five new species of Englerophytum K. Krause (Sapotaceae) from central Africa

Abstract Gautier, L., O. Lachenaud, X. Van der Burgt & D. Kenfack (2016). Five new species of Englerophytum K. Krause (Sapotaceae) from central Africa. Candollea 71 ≥ : 287–305. In English, English and French abstracts. Five new species of Englerophytum K. Krause (Sapotaceae) are described : Englerophytum paludosum L. Gaut., Burgt & O. Lachenaud, Englerophytum gigantifolium O. Lachenaud & L. Gaut., Englerophytum libenii O. Lachenaud & L. Gaut., Englerophytum sylverianum Kenfack & L. Gaut., and Englerophytum ferrugineum L. Gaut. & O. Lachenaud. All five species are illustrated with line drawings and three of them with field photos. Distribution maps are also provided, and a preliminary extinction risk assessment according to IUCN Categories and Criteria is carried out : Englerophytum paludosum is assessed as “Least Concern”, Englerophytum sylverianum as “Vulnerable”, Englerophytum libenii and Englerophytum ferrugineum as “Endangered”, and Englerophytum gigantifolium as “Critically Endangered”.

Two New Anisophyllous Species of Sabicea Aubl. (Rubiaceae) from Gabon

Abstract Lachenaud, O. & L. Zemagho (2015). Two new anisophyllous species of Sabicea Aubl. (Rubiaceae) from Gabon. Candollea 70: 219–229. In English, English and French abstracts. DOI: http://dx.doi.org/10.15553/c2015v702a7 Two new Rubiaceae species, Sabicea golgothae O. Lachenaud & Zemagho and Sabicea mabouniensis O. Lachenaud & Zemagho, are described and illustrated. These two species are very similar to each other, and differ from all their congeners by the combination of strong anisophylly and pedunculate inflorescences. Their position in the genus is discussed. Both species are apparently endemic to the Mabounié area in West-Central Gabon, currently under exploitation prospects for mining. They are both assessed as “Critically Endangered” according to IUCN Categories and Criteria.

Colletoecema gabonensis, a third species of an unusual African genus of Rubiaceae

As a result of ongoing studies of the Rubiaceae of Gabon, the new species Colletoecema gabonensis is here described and illustrated. It is endemic to Gabon, where it is the only species of the genus, and is so far only known from three collections from the Ogooué-Lolo and Ngounié provinces. The new species is morphologically intermediate between its two congeners, C. dewevrei (from Cameroon, Central African Republic, Republic of the Congo, DR Congo, and Angola) and C. magna (endemic to Cameroon). The new species agrees with C. dewevrei in having flowers with exserted anthers and style, but differs in its sessile flowers and fruits. In the latter characters, it resembles C. magna, from which it can be separated by its smaller fruits and leaves, and by its different floral morphology. An IUCN conservation assessment has been made and the species is provisionally assessed as Vulnerable, based on its restricted area of occupancy and the small number of known locations.

Conspectus of Palicourea section Potaroenses (Rubiaceae), with a new species from French Guiana and a new combination

The species of Psychotria subgen. Heteropsychotria have recently been transferred to Palicourea, following the results of molecular studies showing that they form a monophyletic group with the latter. This paper presents a conspectus of Palicourea sect. Potaroenses (formerly Psychotria subgen. Heteropsychotria sect. Potaroenses), discusses the characters of the section, and provides a key to the species. A new species recently collected in French Guiana is described and illustrated, and one new combination is included. Methods – This paper is based on direct study of herbarium material from BR, CAY, F, K, L, NY, U and US, and additional type specimens from F, K, MO, P, RB, and VEN were consulted online. Two of the species, including the new one, have also been studied in the field. Common practices of herbarium taxonomy have been applied. Results – Palicourea sect. Potaroenses is characterized by the capitate inflorescences surrounded by an involucre of 4–20 elliptic, yellow to red bracts, the leaves with lateral veins strongly ascending and almost reaching the margin, the long tubular calyx, the unusually long corolla tube for the genus, and the peculiar stipules, consisting of an internal sheath and two interpetiolar pieces connate to the sheath by their central part. The section includes eight species: Palicourea aetantha (Sandwith) Delprete & J.H.Kirkbr., P. fanshawei (Standl.) Delprete & J.H.Kirkbr., P. formosissima (Steyerm.) Delprete & O.Lachenaud, P. phaneroneura (Standl.) Borhidi, P. potaroensis (Sandwith) Delprete & J.H.Kirkbr., P. psittacina (Steyerm.) Delprete & J.H.Kirkbr., P. spectabilis (Steyerm.) Borhidi, and the new species P. aurantiosplendens O.Lachenaud & Delprete. The latter is most similar to P. psittacina, from which it can be separated by the dense patent indumentum of the stems, calyx lobes, and inner side of the bracts, and the smaller size of the latter; it also resembles P. spectabilis and P. formosissima, but differs in having the stipules with four lobes on each side (vs. two), the bracts nearly glabrous outside (vs. densely hirsute on both sides) and the calyx lobes much more pubescent than the tube (vs. the calyx uniformly hairy). It is only known from a small area on the upper Sinnamary River, north-central French Guiana, and is evaluated as Endangered (EN D1) according to IUCN criteria.

Two new species of Oxyanthus DC. (Rubiaceae) from Central Africa

Abstract Sonké, B. & O. Lachenaud (2016). Two new of Oxyanthus DC. (Rubiaceae) from Central Africa. Candollea 71: 173–180. In English, English and French abstracts. Two new Rubiaceae species from Central Africa, Oxyanthus doucetii Sonké & O. Lachenaud and Oxyanthus lewisii Sonké & O. Lachenaud, are described and illustrated. Oxyanthus doucetii is endemic to Cameroon and is closely related to Oxyanthus unilocularis Hiern, from which it differs in the minute calyx teeth, the stems with glabrous internodes, the dorsally glabrous stipules, the flower buds with a shorter head, and the corolla lobes not or hardly acute at apex. Oxyanthus lewisii is sparsely distributed from Cameroon to eastern Democratic Republic of Congo, and is characterised by narrow fusiform fruits, glabrous stems, and leaves lacking domatia but sparsely pubescent on the nerves beneath. Both new species are assessed as “Vulnerable” according to IUCN Red List Categories and Criteria.