This study aimed to delimit species boundaries within the Brazilian cactus genus Uebelmannia using ddRAD-seq data and coalescent-based approaches. Analysis of 5,386 loci from individuals representing the currently recognized 6 taxa recovered 12 operational taxonomic units using species tree methods but could not fully resolve species boundaries. Genealogical divergence index values supported two divergent lineages that correspond to geography and morphology, albeit with one taxon lumped into another. Integrating additional data sources may be needed to fully delimit species in this highly structured microendemic genus.

1. Species delimitation in Uebelmannia
(Cactaceae) using ddRAD-Seq data.
Milena C. Telhe¹, Manolo F. Perez¹, Gislaine A.R. Silva¹, Gulzar Khan¹, Juliana R.
Bombonato¹,2, Fernando F. Franco¹,2, Evandro M. Moraes¹
1.Universidade Federal de São Carlos (UFSCAR – Brazil)
2.Universidade de São Paulo (UFSCAR – Brazil)
1

2. Uebelmannia is a Brazilian cactus genus
● 3 species and 5 subspecies are recognized;
● High genetic differentiation within species (Silva
et al., 2020, Biodivers. Conserv. 29).
● Isolated populations with their own
morphological features.
● Genetic differences + morphological variations
may reflect the presence of species not yet
recognized or local adaptations.
Challenges in species delimitation of
highly structured microendemic species
● Rapid and recent diversification;
● Sky-island distributions;
● High population genetic structure;
● Past gene flow and population size
changes.
➔ To face those challenges, the
interspecific limits in
Uebelmannia were tested using
ddRADseq data in a multispecies
coalescent approach.
2
Figure. (A, ) U. gummifera
subsp. gummifera; (B, ) U.
gummifera subsp.
meninensis; (C, ) U.
buiningii; (D, ) U.
pectinifera subsp.
flavispina; (E, ) U.
pectinifera subsp. horrida;
(F, ) U. pectinifera subsp.
pectinifera. Source:
LaGEVol.
INTRODUCTION

3. METHODS
Trying to deal with those challenges
Species tree (Astral)
OTU discovery (Species
tree; FastStructure;
Taxonomy)
Species delimitation
Data Processing Species Delimitation
3
Filtering ddRADseq
data.
Assembly ddRADseq
data (5,386 loci)
FastQC MultiQC CutAdapt
Ipyrad CD-Hit
Gene trees (IQtree)
BPP + Genealogical
divergence index (gdi)

4. H0: Taxonomy - 6 OTU’s
H1: FastStructure - 4 OTU’s
H2: Species Tree - 12 OTU’s
BPP results:
Taxonomy: 6 species pp=1.0
FastStructure: 4 species pp=1.0
Species Tree: 12 species pp=1.0
gdi > 0.7
Taxonomy: 2 groups - U. gummifera
+ U. buiningii; U. pectinifera.
FastStructure: 2 groups – U.
gummifera + U. buiningii; U.
pectinifera.
Species Tree: still in progress
BPP
Species delimitation
RESULTS
 Testing species hypotheses:
* Others gdi values were between
0.2-0.7, a range of indecision.
gdi group 1:
gdi group 2:

5. ● Bayesian species delimitation based on MSC model tend to over-split species when high genetic
structure is present (Leaché et al., 2019, Syst. Biol 68; Sukumaran & Knowles, 2017, PNAS.114)
● gdi is useful to delimiting species with high population structure, once it estimate a general degree of
genetic divergence among taxa considering the combined effects of genetic isolation and gene flow,
although it has a large range of indecision (0.2–0.7) (Leaché et al., 2020, Evolution. 74; Jackson et al.,
2017, Syst. Biol. 66)
● In addition, other sources of information (ex. ecological, morphological) could help in species
delimitation (Sukumaran & Knowles 2017, PNAS.114)
→ The Bayesian species delimitation was not able to distinguish species boundaries within
Uebelmannia. However, gdi recovered two groups with genealogical divergence, indicating
separate evolutionary lineages. Those groups correspond to the geographic distribution, well
supported clades and partialy to taxonomy. Although U. Buininigii is lumped with U.
gummifera, both have a very distinct morphology.
→ Next steps: estimate gdi for the species tree hypothesis and incorporate morphological data.
5
DISCUSSION AND CONCLUSIONS