Stephan W. Gale

Inter-specific relationships and hierarchical spatial genetic structuring in Nervilia nipponica, an endangered orchid in Japan.

An understanding of the extent to which reproductive strategy and seed dispersal lead to the structuring of genetic diversity in space is required when planning measures towards the conservation of endangered plant species. In this study, genetic structure in the endangered terrestrial orchid Nervilia nipponica was investigated using amplified fragment length polymorphisms following extensive sampling throughout the species’ range in Japan and intensive sampling at a single population. Limited diversity was found within the species as a whole, but significant structuring was detected between populations. One genotype was common to two widely separated sites, possibly indicative of long-range dispersal. Significant structure was also detected at the intensively sampled site, as a result of the presence of two distinct putative clones. These findings are consistent with observations of the species’ ability to set seed autogamously and propagate vegetatively. Given the strong colonising capability inferred for the species, attention should focus on identifying and securing habitat conditions conducive to seed germination and seedling establishment in the development of a conservation strategy. As presently circumscribed, N. nipponica is shown to comprise two polyphyletic taxa, both endemic to Japan, and both distinct from N. taiwaniana, a species that some authors have considered conspecific.

Preponderance of clonality triggers loss of sex in Bulbophyllum bicolor, an obligately outcrossing epiphytic orchid

Vegetative propagation (clonal growth) conveys several evolutionary advantages that positively affect life history fitness and is a widespread phenomenon among angiosperms that also reproduce sexually. However, a bias towards clonality can interfere with sexual reproduction and lead to sexual extinction, although a dearth of effective genetic tools and mathematical models for clonal plants has hampered assessment of these impacts. Using the endangered tropical epiphytic or lithophytic orchid Bulbophyllum bicolor as a model, we integrated an examination of breeding system with 12 microsatellite loci and models valid for clonal species to test for the “loss of sex” and infer likely consequences for long‐term reproductive dynamics. Bagging experiments and field observations revealed B. bicolor to be self‐incompatible and pollinator‐dependent, with an absence of fruit‐set over 4 years. Challenging the assumptions that clonal populations can be as genotypically diverse as sexually reproducing ones and that clonality does not greatly influence genetic structure, just 22 multilocus genotypes were confirmed among all 15 extant natural populations, 12 of the populations were found to be monoclonal, and all three multiclonal ones exhibited a distinct phalanx clonal architecture. Our results suggest that all B. bicolor populations depend overwhelmingly on clonal growth for persistence, with a concomitant loss of sex due to an absence of pollinators and a lack of mating opportunities at virtually all sites, both of which are further entrenched by habitat fragmentation. Such cryptic life history impacts, potentially contributing to extinction debt, could be widespread among similarly fragmented, outcrossing tropical epiphytes, demanding urgent conservation attention.

Cheirostylis pusilla (Orchidaceae), a new record for Hong Kong

SummaryThe jewel orchid Cheirostylis pusilla Lindl. is newly recorded from Hong Kong, a significant distance from Yunnan Province, the only other confirmed locality for the species in China. A full description, photos and line drawings are presented for this hitherto poorly known species, and its conservation status is assessed. Cheirostylis malleifera C. S. P. Parish & Rchb. f. is shown to be a later synonym.

Studies in Asian Nervilia (Orchidaceae) V: Nervilia futago, a Cryptic New Species from Southwest Japan Confirmed by Morphological, Cytological, and Molecular Analyses

Abstract Widespread and poorly studied species complexes confound phylogenetic understanding of the Old World terrestrial orchid genus Nervilia. Recent taxonomic studies have suggested greater species richness in Asia than previously envisaged.We used morphological, cytological, and molecular phylogenetic analyses to confirm the existence of a novel, cryptic species of the Nervilia adolphi-punctata species alliance in southwest Japan, supporting earlier findings from a genetic fingerprinting study. Nervilia futago is formally described and illustrated here. In the vegetative state, the new species is practically inseparable from the more widespread N. nipponica, with which it co-occurs at several sites, but it can be distinguished in flower by its glabrous petals, by the lack of tall clavate hairs on the lip, and by the placement of the pollinia on the stigma prior to anthesis. Chromosome numbers and DNA content also differ. Despite their wide geographic separation, sequence data indicate greater affinity of N. futago to Himalayan members of the alliance than to other species of East Asia. The utility of genetic approaches in resolving identities and relationships in this taxonomically intractable genus is emphasised.

Integrative analyses of Nervilia (Orchidaceae) section Linervia reveal further undescribed cryptic diversity in Thailand

The delimitation of cryptic species is necessary to accurately classify and appropriately conserve biodiversity. Integrative analyses can be incisive in detecting and circumscribing cryptic diversity, especially in species complexes whose members are delineated by minor or overlapping morphological variation. We adopt an integrative approach to assess species relationships and resolve species boundaries in the taxonomically difficult Nervilia adolphi/punctata species alliance of N. sect. Linervia, an Old World complex of reduced, one-flowered terrestrial orchids that is both species-rich and poorly known in tropical and warm temperate Asia. We sampled 12 of the 27 known species of the alliance in Asia, including all four species reported from Thailand and a further 20 plants collected in that country that could not be satisfactorily identified using morphology alone. Phylogenetic analyses using one nuclear (ITS) and two plastid (matK and trnL-F) markers confirmed both N. sect. Linervia and the alliance itself as monophyletic, and corroborated 11 of the 12 sampled species; N. punctata proved polyphyletic, with the Thai samples referred to this Indonesian species falling sister to the Himalayan N. mackinnonii. The 20 unidentified Thai samples formed three distinct, strongly supported clades. STACEY, a Bayesian coalescence approach to species delimitation, resolved the same three clusters, but provided evidence suggesting that one comprised two distinct sub-clades. Building on this genetic evidence, we identify subtle morphological differences and invoke a diagnosable species concept to circumscribe three previously unrecognized cryptic species from Thailand. This objective approach to species delimitation validates ostensibly minor morphological differences as a basis for differentiating species within the alliance, paving the way for a global analysis of species boundaries throughout the genus as a whole.

Taxonomic Notes on Didymoplexiella siamensis and Gastrodia peichatieniana, Two Fully Mycoheterotrophic Orchids New to the Flora of Hong Kong

The ephemeral, leafless orchids Didymoplexiella siamensis and Gastrodia peichatieniana are newly recorded from Hong Kong. A lectotype is selected for the former, and the recently described D. denticulata from southern Vietnam is reduced to its synonymy. Full descriptions and global conservation assessments are presented for these hitherto poorly known species.