Data from: Reassessment of morphological species delimitations in the Cyperus margaritaceus-niveus complex using morphometrics

Background and aims – The Cyperus margaritaceus-niveus complex is a group
of ten tropical species from sub-Saharan Africa and Madagascar: C.
karlschumanii, C. kibweanus, C. ledermannii, C. margaritaceus, C. niveus,
C. nduru, C. obtusiflorus, C. somaliensis, C. sphaerocephalus, and C.
tisserantii. They are characterised by a capitate head of white-yellow
spikelets and modified culm bases and recent molecular analysis puts them
in as a distinct clade. The group lacks a modern taxonomic revision, and
the taxa described in the Flora treatments of the past 50 years differ
considerably in their circumscription. In this study, morphometric
analyses are used to test species limits to establish more stable
morphological delimitations of the taxa. Material and methods – An
examination of 15 morphological characters on 489 herbarium specimens was
carried out and the data was analysed using Principal Component Analysis
(PCA), Linear Discriminant Analysis (LDA) with cross-validation, and
Classification and Regression Tree (CART) analysis. Cyperus kibweanus was
not further considered due to lack of material. Key results – Both PCA and
LDA showed varying degrees of overlap in the nine remaining taxa, with no
single group clearly separating in multivariate space. However,
cross-validation clearly showed C. margaritaceus as a distinct entity
despite its overwhelming presence in the PCA. Both LDA and CART failed to
separate C. niveus as a distinct group as its specimens were dispersed
among the other groups. Differing results were obtained for other taxa
depending on the type of analysis. C. margaritaceus, C. nduru, and C.
sphaerocephalus were divided into two groups by CART but re-examination of
the specimens does not definitively support the idea that these
infraspecific groups represent separate taxa. Conclusions – The results
show that eight morphospecies are recognised by LDA and six morphospecies
by CART. Characters used to separate the taxa in Flora treatments scored
high loadings in the analysis showing their high taxonomic utility value.
The methods used can be applied to resolving other complexes in the
Cyperaceae.