Strengthening the taxonomic backbone of Thai orchid conservation: genetic fingerprinting and morphometry applied to a species complex in Geodorum

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Background and Aims A well-supported classification is crucial for conservation planning, but intricate species complexes constitute a serious challenge to the preparation of flora accounts. In preparation of the Flora of Thailand account on Geodorum (Orchidaceae), it was decided to use multivariate morphometric analysis and genetic fingerprinting to resolve the intricate G. pulchellum sensu Seidenfaden/G. siamense species complex, with the specific aim of testing the taxonomic soundness of the apparently rare and conservation-requiring G. pulchellum sensu Seidenfaden. Geodorum densiflorum, universally considered distinct from the above species complex, was included as reference.

Methods Morphometric data and tissue samples for amplified fragment length polymorphism (AFLP) analysis were collected from 17 Geodorum populations in northern and north-eastern Thailand. Principal components analysis was employed to summarize the patterns of phenetic variation. Hierarchical genetic differentiation between populations was explored using Bayesian inference followed by cluster analysis.

Key Results The taxonomic distinction of G. densiflorum was generally supported. In contrast, G. siamense and G. pulchellum sensu Seidenfaden were poorly separated, especially according to the estimated patterns of inter-population genetic differentiation.

Conclusions The G. pulchellum sensu Seidenfaden/G. siamense complex should be treated as one variable species (under the name G. siamense), meaning that G. pulchellum sensu Seidenfaden should not be given high independent conservation priority. This study demonstrates that flora accounts can benefit from prior employment of multivariate and Bayesian methods for exploring intricate species complexes, in turn leading to more solid decisions and priorities in a conservation context.

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