Delayed differentiation of epidermal cells walls can underlie pedomorphosis in plants: the case of pedomorphic petals in the hummingbird-pollinated Caiophora hibiscifolia (Loasaceae, subfam. Loasoideae) species

Background Understanding the relationship between macroevolutionary diversity and variation in organism development is an important goal of evolutionary biology. Variation in the morphology of several plant and animal lineages is attributed to pedomorphosis, a case of heterochrony, where an ancestral juvenile shape is retained in an adult descendant. Pedomorphosis facilitated morphological adaptation in different plant lineages, but its cellular and molecular basis needs further exploration. Plant development differs from animal development in that cells are enclosed by cell walls and do not migrate. Moreover, in many plant lineages, the differentiated epidermis of leaves, and leaf-derived structures, such as petals, limits organ growth. We, therefore, proposed that pedomorphosis in leaves, and in leaf-derived structures, results from delayed differentiation of epidermal cells with respect to reproductive maturity. This idea was explored for petal evolution, given the importance of corolla morphology for angiosperm reproductive success. Results By comparing cell morphology and transcriptional profiles between 5 mm flower buds and mature flowers of an entomophile and an ornitophile Loasoideae species (a lineage that experienced transitions from bee- to hummingbird-pollination), we show that evolution of pedomorphic petals of the ornithophile species likely involved delayed differentiation of epidermal cells with respect to flower maturity. We also found that developmental mechanisms other than pedomorphosis might have contributed to evolution of corolla morphology. Conclusions Our results highlight a need for considering alternatives to the flower-centric perspective when studying the origin of variation in flower morphology, as this can be generated by developmental processes that are also shared with leaves. Graphical Abstract

Impatiens wuyiensis (Balsaminaceae), a new species from Fujian of Southeast China, based on morphological and molecular evidences

Background Southeast Asia, together with tropical Africa, Madagascar, South India and Sri Lanka, and the eastern Himalayas, are the five primary hotspots of species diversity of Impatiens (Balsaminaceae). China is also rich in Impatiens species, especially in the limestone karsts or ‘Danxia’ landforms. With zygomorphic flowers and diverse corolla morphology and color, the species in Impatiens are well-known for their ornamental use, but they are also notorious in taxonomy. During the preparation of revision of Impatiens in Zhejiang and adjacent regions, an unknown species was collected from Mt. Wuyi in Fujian Province, Southeast China. Results Phylogenetic analyses based on nuclear ITS, chloroplast atpB-rbcL and trnL-F sequences, together with micromorphology of pollen grains and seed coats, strongly supported the close relationship of the new species with Impatiens platysepala Y.L.Chen and I. chloroxantha Y.L.Chen. In turn, both molecular data and morphological characters also were sufficient to distinguish the new species from the other two counterparts. Conclusions Our detailed morphological observations and molecular phylogenetic analyses support the recognition of Impatiens wuyiensis as a species new to science.

Geometric morphometrics of corolla shape in Campanula (Campanulaceae) from Cabo Verde archipelago

In the Cabo Verde archipelago, Campanula spp. (bellflowers) are currently represented by four endemic species restricted to mountainous islands (C. bravensis, C. feijoana, C. hortelensis and C. jacobaea), all of which are known for high floral polymorphism. Diagnostic features of the corolla often differ from original descriptions, bringing into question their taxonomic delimitation. Based on the variations in the corolla shape observed during fieldwork, eight morphogeographical entities were distinguished among the taxa in the archipelago. Geometric morphometrics was used to quantify and examine these floral variations. Corolla morphology of 221 photographed flowers was captured by 2D landmarks and semi-landmarks configurations and analysed with canonical variate analysis. The results show agreement between morphological groupings and their geographical ranges. For most entities, the geographical origin may be determined with accurate morphological examination of the flower. In this case, the corolla shape proves to be a taxonomically discriminant trait. Furthermore, the terminology used until now to characterize these different floral forms is discussed. The present study contributes significantly to clarifying the floral polymorphism in Cabo Verdean Campanula and suggests that taxonomic revision of this group is necessary.

Two new species of Adenocalymma (Bignonieae, Bignoniaceae) from the Atlantic Forest of Brazil

Adenocalymma, with approximately 75 species, is one of the largest genera from tribe Bignonieae (Bignoniaceae). The genus mostly includes yellow-flowered lianas and shrubs that are conspicuous components of the dry and wet Neotropical forests. As part of an ongoing taxonomic and phylogenetic study of this group, we found unusual materials that do not match any of the currently recognized taxa. These materials formed the basis of two new species described here, which are endemic from the Brazilian Atlantic forest: Adenocalymma lineare, and Adenocalymma apetiolatum. Adenocalymma lineare resembles Adenocalymma nervosum on the linear leaflets, but differs in the habit, prophyll morphology, leaflet venation, floral bracts, bracteole morphology and dimensions, corolla color and morphology, anther and stigma position. While Adenocalymma apetiolatum closely resembles Adenocalymma sessile and Adenocalymma subsessilifolium on the sessile leaf insertion and shrubby habit, it differs from both species by the corolla color, indument type and color. Apart from that, Adenocalymma apetiolatum differs from the former by the prophyll morphology, floral bract and bracteole morphology, and the latter by the corolla morphology. These two new taxa are illustrated, and distribution maps are provided here. Notes on the taxonomy, geographic distribution, habitat, and conservation status are also included.

CAN THE SECTIONAL POSITION OF GENTIANA CACHEMIRICA BE CLARIFIED BY A DETAILED ANALYSIS OF ITS MORPHOLOGY?

Gentiana cachemirica is a rare plant from northern Pakistan and northwestern India. The sectional position of this species has been a matter of considerable debate. Various authors have placed Gentiana cachemirica in one of three different sections – Gentiana sect. Isomeria, Gentiana sect. Kudoa or Gentiana sect. Pneumonanthe. The present paper assesses the taxonomic affinities of this species using a detailed study of its morphology accompanied by morphological phylogenetic and cluster analyses. Characters of the seed testa, corolla morphology and growth architecture were studied for selected species from the above-mentioned sections and closely related Gentiana sect. Cruciata. Representatives of Gentiana sect. Ciminalis were used as outgroups. Our results suggest that G. cachemirica belongs to Gentiana sect. Pneumonanthe and that its affinities are closer to the Western Asiatic group of this section.

FLORAL MORPHOLOGY AND RECOGNITION OF VARIETIES IN CONANDRON RAMONDIOIDES (GESNERIACEAE) FROM JAPAN AND TAIWAN

Comparisons of corolla morphology were made between plants of Conandron ramondioides (Gesneriaceae) from 23 localities in Japan and Taiwan. Lobe-length to tube-length ratios were found to correlate with geographical distribution and support the recognition of two previously described varieties: var. ramondioides in mainland Japan (lobe length less than twice tube length) and var. taiwanensis from Iriomote Island (Japan) and Taiwan (lobe length more than three times tube length). Mitotic chromosomes were also observed but no differences were seen between accessions, all of which had 2n=32.

A NEW SPECIES OF STREPTOCARPUS (GESNERIACEAE) FROM THE PONDOLAND COAST, SOUTH AFRICA

The new species Streptocarpus lilliputana (Gesneriaceae), collected on the Pondoland coast, South Africa, is described. Although its alliances are not obvious in terms of corolla morphology and rosulate habit, it approaches S. gardenii and its allies. The pollen and stigma of S. lilliputana differ markedly from the stenopalynous grains and bilobed stigmas of the other South African rosulate species. Streptocarpus lilliputana is exceedingly rare and is a further endemic from the Pondoland centre.