Tuesday, May 30, 2017

[Botany • 2017] Satyrium liltvedianum • A Newly Discovered Orchid Species from the Kogelberg Mountains of the Cape Floristic Region, South Africa


Satyrium liltvedianum Van der Niet


 Highlights
• A new orchid species was discovered in the well-botanised Kogelberg Mountains.
• The new species was not present among historical museum collections.
• The new species resembles other Satyrium species, but is phylogenetically distinct.
• The compound β-Linalool dominates the floral scent, indicative of moth pollination.

Abstract
Individuals of plant populations with traits which are inconsistent with any existing species description may represent intraspecific variants, products of hybridisation, or a novel species. To distinguish among these possibilities for a population of unusual Satyrium individuals from the Kogelberg Mountains in the Cape Floristic Region (CFR), morphological traits and floral scent were documented, and phylogenetic analyses implemented. Plants from the Kogelberg population were characterised by long-spurred white flowers and a bifid rostellum. Floral scent was dominated by the common floral monoterpene volatile β-linalool. Although these traits characterise several southern African members of the genus, DNA sequences from the nuclear and plastid genomes of an accession from the Kogelberg population were highly distinct from other Satyrium species. The Kogelberg accession occupied an isolated phylogenetic position within the ‘Satyrium clade’ and was not sister to any other species with similar traits. There was weak support for membership of a clade of species with which plants from the Kogelberg population share the possession of lateral sepals that project at a perpendicular angle to the median sepal, and cover the side of the labellum, and which also produce β-linalool as dominant scent compound. Given the congruence of phylogenetic relationships inferred from plastid and nuclear DNA sequences respectively, a hybrid status of the Kogelberg population was rejected. Based on these results, the new species, Satyrium liltvedianum, which is uniquely characterised by the size, shape and orientation of sepals and lateral petals, is described in this study. Other Satyrium species with similar floral traits are pollinated by crepuscular moths, which therefore can also be inferred for the new species. A dichotomous key to the white-flowered, long-spurred Satyrium species of South Africa is provided. The restricted distribution range, a typical phenomenon for many CFR plant species, in combination with the isolated phylogenetic position, suggests that S. liltvedianum represents a palaeoendemic species.

Keywords: β-Linalool; Moth pollination; Orchidaceae; Palaeoendemic; Floral scent

Fig. 1. Satyrium liltvedianum in situ on 10 November 2009 at the type locality in the Kogelberg Mountains after the veld fire, showing maroon coloration of the stem, sheathing leaves and abaxial side of the bracts.

Photograph by Herbert Stärker. 


Satyrium liltvedianum Van der Niet sp. nov. is morphologically similar to S. candidum, but differs from this species by having lateral sepals that overlap with the outside surface of the labellum and project at a ninety-degree angle from the median sepal instead of projecting from the same plane, and lateral sepals and petals that are approximately equal in size instead of smaller lateral petals than lateral sepals, and a median sepal that is narrower and longer than the lateral sepals instead of more or less similarly-sized.

TYPE.— Western Cape Province, 3418 (Somerset West): Steenbras Catchment area near Rockview Dam, Kogelberg Mountains (–BB), 18 Nov 2009, W.R. Liltved 120 (NBG, holo.).

Distribution: S. liltvedianum is known from a single population in the Steenbras Catchment area of the Kogelberg Mountains.

Etymology: This species is named in honour of William Rune Liltved (1960–) who, over the past two decades, has made an invaluable contribution to recording the orchids of the Cape Floristic Region. This work culminated in publication of the book, The Cape Orchids ( Liltved and Johnson, 2012).

Conservation status: Similar to several other orchids from the CFR, S. liltvedianum is known only from a single localised population of about 50 individuals (Linder and Kurzweil, 1999). The species is therefore considered highly vulnerable.


Conclusion: 
There are many reasons why efforts to discover and describe species should be ongoing. Only recognised taxa can be adequately conserved; the success of scientific research often depends on sound taxonomic classification; beneficial properties of species can only be communicated if a species has a formal name; and recently Dijkstra (2016) argued that because naming species is inherent to human nature, continued exploration for the vast majority of species that are still unknown will improve our consciousness of the natural world. Much of Earth's biotic diversity is currently highly threatened and many species are on the brink of extinction, or have recently gone extinct (Wake and Vredenburg, 2008; Barnosky et al., 2011;  McCallum, 2015), which provides a great sense of urgency to taxonomic enterprise. Several studies, including this study, have shown that new species are regularly still discovered in the field (e.g. Linder and Hitchcock, 2006 ;  Steiner, 2011). Therefore, taxonomy cannot solely rely on historical herbarium or museum collections, even from within relatively well-botanised areas such as the Kogelberg Biosphere Reserve of the CFR, only 70 km from the city of Cape Town.


T. Van der Niet. 2017. Satyrium liltvedianum: A Newly Discovered Orchid Species from the Kogelberg Mountains of the Cape Floristic Region (South Africa).  South African Journal of Botany. 111; 126-133. DOI:   10.1016/j.sajb.2017.03.018
New species named after the man who co-wrote the ultimate Cape orchid book http://scibraai.co.za/new-species-named-after-the-man-who-wrote-the-ultimate-cape-orchid-book/   @SciBraai


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