Research Article
Does leaf anatomy aid in species identification of Butia
(Arecaceae)?
Laboratório de Anatomia e Biomecânica Vegetal, Departamento de Botânica, Setor de Ciências Biológicas, Universidade Federal do
Paraná (UFPR), PO Box 19031, 81531-980 Curitiba, PR, Brazil
2
Laboratório de Anatomia e Dendrologia, Universidade Federal de Minas Gerais (UFMG), Avenida Universitária, 1000, Bairro
Universitário, 39404-547 Montes Claros, MG, Brazil
3
Departamento de Ciências Biológicas, Universidade Federal dos Vales do Jequitinhonha e Mucuri (UFVJM), Rodovia BR 367, Km 583,
5.000, CEP 39.100-000, Diamantina, MG, Brazil
1
Received: 21 May 2018
Editorial decision: 21 July 2018
Accepted: 26 July 2018
Published: 28 July 2018
Associate Editor: Renata Meira
Citation: Sant’Anna-Santos BF, Santos, SA, Nunes, ELP, Francino, DMT, Carvalho Júnior, WGO. 2018. Does leaf anatomy aid in species
identification of Butia (Arecaceae)? AoB PLANTS 10: ply046; doi: 10.1093/aobpla/ply046
Abstract. Butia is a neotropical genus whose identification is based mostly on characters from external morphology, which are sometimes variable or inadequate for species differentiation. We aimed to verify if leaf anatomy of
18 Butia species brings new characters suitable for species identification and if it corroborates the phylogenetic relationship within the genus. Moreover, we propose an anatomical key to assist in species identification. Pinnae were
collected and subjected to the usual techniques for light and scanning electron microscopies. The anatomical key
was created with the aid of Xper2 software, based on the importance of characters to distinguish species according
to the Jaccard index. All species have isobilateral mirrored mesophyll, amphistomatic leaves and secondary vascular bundles with sclerenchymatic sheath reinforcement connected to the hypodermis. Among the species studied,
B. marmorii and B. matogrossensis showed exclusive characters. For the other species, up to five characters are
sufficient for delimitation. Our anatomical key presents relevant characters that allow the identification of the recognized species of Butia. Reliable anatomical characters of easy observation, especially the raphides, are valuable in
species distinction. Leaf anatomy, already used to support new taxa in related genera like Allagoptera and Syagrus,
can also be useful to validate questionable Butia species and differentiate between similar species but do not reflect
the proposed relationship between Butia species.
Keywords: Attaleineae; leaf anatomy; Palmae.
Introduction
In spite of its monophyly (Merrow et al. 2009, 2015),
Butia is morphologically highly diverse (Glassman 1970;
Dransfield et al. 2008; Noblick 2010, 2014), causing difficulties in species delimitation (Soares et al. 2014) and
considerable changes on the taxonomy of the genus.
According to Noblick (2014), between 2004 and 2014,
the number of accepted species included in the genus
has risen from 9 to 24, and more species are expected
to be described.
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Bruno Francisco Sant’Anna-Santos1, Samuel Alves dos Santos2, Elaine L. P. Nunes1*, Dayana Maria
Teodoro Francino3 and Wellington Geraldo Oliveira Carvalho Júnior2
*Corresponding author’s e-mail address: elaine.lopes@gmail.com
© The Author(s) 2018. Published by Oxford University Press on behalf of the Annals of Botany Company.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/
licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
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identification or even induce error. Thus, it is imperative to find new characters suitable for improving Butia
identification.
Because of this, taxonomy of Arecaceae traditionally has also been based on anatomical aspects of the
organs, mainly of the leaf blade (Tomnlinson 1961;
Tomnlinson et al. 2011; Noblick 2013, 2014; Martins et al.
2015; Sant’Anna-Santos et al. 2015; Pinedo et al. 2016;
Vianna et al. 2017). The leaf blade has provided useful
characters to discriminate between species in some genera of the family, such as Oenocarpus (Silva and Potiguara
2008; Tomnlinson et al. 2011), Syagrus (Glassman 1970;
Tomnlinson et al. 2011; Noblick 2013; Noblick et al. 2014),
Allagoptera (Tomnlinson et al. 2011; Martins et al. 2015;
Pinedo et al. 2016), Parajubaea (Meerow et al. 2009;
Tomnlinson et al. 2011), Acrocomia (Vianna et al. 2017)
and even Butia (Noblick 2014; Sant’Anna-Santos et al.
2015). A detailed comparative study of the leaf anatomy
of Butia provided useful characters that corroborated the
split of B. odorata from B. capitata and aid in their distinction (Sant’Anna-Santos et al. 2015).
However, there are more comprehensive anatomical treatments for other genera of Attalaineae subtribe. Noblick (2013) proposed an identification key for
26 acaulous species of Syagrus, based exclusively on
anatomical characters of the leaf and verified that leaf
anatomy corroborates their phylogenetic relationship.
Therefore, this study aimed to verify if leaf anatomy of
Butia species brings new characters suitable for species
identification and propose an anatomical key. Moreover,
we aimed to verify if, as for other Attaleinae genera, leaf
anatomy can corroborate the phylogenetic relationship within Butia too. We analysed all the accepted by
Noblick (2014) plus one specimen of B. leiospatha currently synonymized under B. capitata.
Materials and Methods
Samples of Butia archeri, B. campicola, B. capitata,
B. catarinensis, B. eriospatha, B. exospadix, B. lallemantii,
B. leiospatha, B. leptospatha, B. lepidotispatha,
B. marmorii, B. matogrossensis, B. microspadix,
B. paraguayensis, B. pubispatha, B. purpurascens e
B. yatay were collected from specimens cultivated in
the Botanic Garden of the Plantarum Institute, in Nova
Odessa municipality, São Paulo State, Brazil. Vouchers
were deposited in the herbarium of the Botanic Garden
Plantarum under the numbers HPL-1531, HPL-11480,
HPL-10332, HPL-11412, HPL-13194, HPL-11513, HPL11477, HPL-3405, HPL-11479, HPL-11476, HPL-11494,
HPL-10265, HPL-11628, HPL-13195, HPL-11475, HPL13196, HPL-7659. For each species, at least three
specimens were analysed, except for B. leiospatha
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Indeed, there is no consensus regarding the present
total number of species, some of them being still questionable according to Noblick (2014). Noblick (2010)
reported that 18 species occur naturally, predominantly
in areas in southern Brazil, eastern Paraguay, north-eastern Argentina, and north-western and south-eastern
Uruguay. Brazil possesses the majority of the existing
species of Butia, at least 16. Noblick (2010) also recognized 18 species, while Soares (2015) recognized 20 valid
species and listed 11 names as synonyms or doubtful
species. Presently, the World Checklist of Selected Plant
Families—WCSP—(2018) lists 22 species, while the Flora
do Brasil 2020 (Heiden et al. 2018) recognizes 19 species
and two varieties occurring in Brazil.
As an example of the taxonomical instability of Butia,
we can cite B. leiospatha, which is considered a synonym
of B. capitata in WCSP (2018) and B. lallemantii in Flora
do Brasil 2020 (Heiden et al. 2018). Butia leiospatha was
originally described by Barbosa Rodrigues as Cocos leiospatha in 1877, but, according to Glassman (1970), he did
not indicate any specimen or type and the description did
not fit the illustration of it. On the B. leiospatha description, plants are usually acaulescent but, the illustration
depicts are relatively tall tree. Drude (1881) described
C. leiospatha var. angustifolia based on a specimen collected by Warming in 1845 in Lagoa Santa municipality,
Minas Gerais State, Brazil. Later, Beccari (1916) elevated
Butia to genus and considered C. leiospatha var. angustifolia as a synonym of Butia bonneti. Glassman (1970),
on the other hand, considered the specimen collected
by Warming unsuitable for a correct identification due to
the lack of data and poor vouchering; he suggested that
this specimen could represent a young state of B. capitata or belong to B. arenicola. Also, he considered B. bonnetii, B. poni and B. pungens as doubtful. Characters
derived from the external morphology such as the general aspect of the plant, size of inflorescences and fruit
colour may be highly variable intraspecifically (Noblick
2014). This variability put together with the relevance
attributed to a given character by each author when
circumscribing a taxon, perpetuate the taxonomic deadlocks regarding the genus.
Currently, there are two identification keys proposed
by Noblick (2010) and Soares et al. (2014)—modified by
Noblick (2014); both are based solely on external morphology. The most comprehensive key includes 17 species (Noblick 2014) is only effective, according to the
author, if used with mature plants. Immature specimens
of Butia are difficult to discriminate of due to the influence of their age upon plant and inflorescence sizes.
Since part of those characters are naturally variable
or may vary according to plant age (Noblick 2014) and
environment (Noblick 2010), using only them might limit
Sant’Anna-Santos et al. – Leaf anatomy of Butia species
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Observation and photo documentation were performed under a light microscope (Primo Star, Zeiss,
Berlin, Germany) with a coupled digital camera (AxioCam
ERc5s, Zeiss, Berlin, Germany). After the processing of
the samples, images were obtained in a scanning electron microscope (JSMT200, Jeol Co., Tokyo, Japan).
Thirty-two qualitative anatomical characters considered
reliable (without variation between specimens of the same
species) were selected to the analysis of the phenotypic
similarity between species. The resulting matrix scoring
presence and absence of characters was used to perform
a cluster analysis at PCCORD 5.0 software. The same characters were also used to elaborate a dichotomous key
(software Xper2, version 2.3.1) based on the importance
of characters to differentiate species according to Jaccard
index (Mueller-Dombois and Ellemberg 1974).
Results
Stomata are organized longitudinally and parallel in
rows (Fig. 1A), tetracytic and composed of elongated
lateral subsidiary cells (Fig. 1B)—transversely arciform
(Fig. 1C)—and hexagonal terminal (polar) subsidiary cells
(Fig. 1B). The guard cells show prominent outer and inner
stomatal ledge (Fig. 1C). Ordinary cells of the epidermis
possess anticlinal walls with a straight outline (Fig. 1B).
The epidermis is covered by a thick cuticle (Fig. 1C).
Pinnae are amphistomatic (Fig. 1D). The mesophyll
is isobilateral, compact and with one band of central
chlorenchyma of bulky elongate-spherical cells that lies
in between two bands of palisade parenchyma (Fig. 1D).
Adjacent to the epidermis, on both sides of the pinnae,
one or two rows of hypodermis are present (Fig. 1D),
whose cells are larger than the ordinary epidermal ones.
The secondary and tertiary vascular bundles of Butia
can mostly be classified into three types. Type 1 includes
bundles of larger calibre, with four poles of sieve elements
plus companion cells and a sclerenchymatic sheath
extension associated to adaxial and abaxial hypodermis
(Fig. 1D and E). Type 2 includes bundles similar to type
1, but with undivided phloem (Fig. 1D and F). Type 3, the
most frequent, includes bundles with smaller calibre and
with a sclerenchymatic sheath extension associated only
to the hypodermis of one side; they usually occur above
or below of a similar bundle or, less frequently, above or
below a fibre cap or a vascular tissue not surrounded by
a sclerenchymatic sheath (Fig. 1D). The stegmata cells,
with druse-like silica bodies, occur in association with the
fibres of the sclerenchymatic bundle sheath (Fig. 1G–I).
The midrib is more protruding on the adaxial than on the
abaxial surface (Fig. 1J) in all studied species.
In transverse sections, the margin can be either
deltoid (Fig. 2A) or quadrangular (Fig. 2B and C).
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that was collected from a single specimen. Samples of
B. odorata, B. capitata and B. archeri were collected in the
field (in Tapes municipality, Rio Grande do Sul; in Lontra
municipality, Minas Gerais and Diamantina municipalityType locality, Minas Gerais, respectively). These vouchers
were deposited, respectively, in the Alarich Schultz
Herbarium of the Museum of Natural Sciences, Rio
Grande do Sul Zoobotanical Foundation (HAS-47695),
in the Herbarium of the Department of Botany, Federal
University of Minas Gerais (BHCB-144649) and in
Herbarium of Federal University of Jequitinhonha and
Mucuri Valleys (DIAM-3157). Herbarium acronyms are
according to Thiers (2018, continuously updated).
Samples for epidermic dissociations were fixed in
50 % ethanol, while those for semi-permanent slides
were fixed in FAA (solution of 47 % formaldehyde, acetic acid and 70 % ethanol, 1:1:18 by volume) (Johansen
1940), and those for scanning electron microscopy analysis were fixed in Karnovsky’s solution (Karnovsky 1965).
For the light microscopy studies, samples were previously softened for 12 h in a solution of 10 % ethylenediamine, as described by Sant’Anna-Santos et al.
(2015). Thus, samples were sectioned on a microtome
table (model LPC, Rolemberg e Bhering Comércio e
Importação LTDA., Belo Horizonte, Brazil) with a disposable razor blade. Both sections and epidermal fragments were stained with 1 % Safranin and 1 % Astra
blue, mounted between slide and coverslip with distilled
water for photo documentation and, subsequently, with
glycerin water (Bukatsch 1972, modified).
Pinnae fragments with ~1 cm2 were dissociated in a
solution of 10 % nitric acid and 10 % chromic acid 10 %
(v/v) (Jensen 1962) for analysis of the epidermis in frontal
view. The resulting epidermal fragments were stained with
1 % Safranin and 1 % Astra blue.
Fixed samples were dehydrated in an ethylic series (30,
50, 70, 90 and 100 %) and embedded in methacrylate
(Historesin, Leica Instruments, Heidelberg, Germany).
Sections with 5 μm were obtained through a manual
rotary microtome Reichert and stained with toluidine
blue O pH 4.0 (O’Brien and McCully 1981). The slides were
mounted using water for observation and documentation.
For morphological analysis of epicuticular waxes,
fragments of the median portion of pinnae (0.5 cm2)
were dehydrated in ethylic series and dried by critical
point drier (Balzers CPD 030) and covered with gold in
a Sputter Coater (Balzers SCD 050). For analysis of silica
bodies, part of the samples was transferred from the
fixative solution to a solution of 30 % glycerol for 3 h.
Then, they were transferred to liquid nitrogen for 30 s
and cryofractured. Afterwards, they were dehydrated in
a graded series of propanone, critical-point dried and
sputter-coated with gold.
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Figure 1. Epidermis and mesophyll of Butia pubispatha (A, E and J), B. campicola (B), B. microspadix (C and D), B. catarinensis (F), B. odorata (G) and
B. capitata (H and I). Front view (A and B) and transverse sections (C–G and J) under light microscopy and scanning electron microscopy (H and I).
(A) Stomata organized in rows (white circles). (B) Tetracytic stomata. (C) Inner (black arrow) and outer (grey arrow) stomatal ledge. (D) Isobilateral
mesophyll and type 3 vascular bundle (black arrows). (E and F) Vascular bundles: type 1 (E) and 2 (F). (G–I) Silica body (stars). (J) Midrib. TC, terminal
cell; LC, lateral cell; GC (white arrows), guard cell; Cu, cuticle; PH, phloem; PP, palisade parenchyma; CP, central parenchyma; Fi, fibres.
However, some species (B. capitata, B. microspadix,
B. lallemantii and B. pubispatha) showed some specimens with pinnae with deltoid margins and other
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with quadrangular margins, demonstrating that
this is not a reliable character to distinguish these
species.
© The Author(s) 2018
Sant’Anna-Santos et al. – Leaf anatomy of Butia species
Two patterns of sheath reinforcement were observed
in tertiary bundles of the margin. The first, and least
frequent, contains a single reinforced vascular bundle (Fig. 2B), the second, and more frequent, contains
two (Fig. 2C), being observed in 11 species. Crystal idioblasts containing raphides (Fig. 2D and E) occur within
the margins and intermediary region of pinnae in eight
species.
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Figure 2. Leaf anatomy of Butia leptospatha (A), B. matogrossensis (B and K), B. paraguayensis (C), B. exospadix (D and I), B. capitata (E), B.
catarinensis (F), B. purpurascens (G), B. marmorii (H), B. archeri (J), B. lallemantii (L) and B. yatay (M) under light (A–D and F–M) and scanning
electron microscopy (E). Transversal (A–C, E, F–M) and longitudinal sections (D). (A–C) Leaf margin with reinforced vascular bundles (black
arrows). (D–E) Raphides (stars). (F) Chlorenchyma (white circle). (G) Round midrib. (H) Slightly protruding midrib (black circle). (I–J) Expansion
tissue. (K) Discontinuous fibre ring (white arrow). (L–M) Vascular bundles (white circles). Ch, chlorenchyma; ET, expansion tissue; Fi, fibres.
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they are at the same level of ordinary epidermal cells
(Fig. 4B), except for B. eriospatha. In most species with
coated stomata (Fig. 4C–F), they are sunken within the
epidermis (Fig. 4D), as seen in B. catarinensis; an exception is B. campicola, where they are at the level of ordinary cells (Fig. 4F and G).
Thirty-two characters were selected for the multivariate analysis (Table 1). Based on the selected anatomical
characters (Table 2), we elaborated this identification
key for Butia:
1 Presence of raphides.........................................................2
1′ Absence of raphides.........................................................9
2 Main vascular system of midrib composed of two
collateral bundles............................................................3
2′ Main vascular system of midrib composed of three or
more collateral bundles..................................................….5
3 Inconspicuous deposits of epicuticular wax....................
...................................................................... B. leptospatha
3′ Epicuticular wax deposited as horizontal plates..........4
4 Midrib round-shaped in transverse section…. B. capitata
4′ Midrib triangular-shaped in transverse section..................................................................... B. marmorii
5 Fibrous ring of the midrib connected to the hypodermis.................................................................................6
5′ Fibrous ring of the midrib not connected to the hypodermis.................................................................................7
6 Expansion tissue continuous......................... B. exospadix
6′ Expansion tissue discontinuous................. B. pubispatha
7 Fibrous ring projected on the midrib on the abaxial
surface............................................................. B. campicola
7′ Fibrous ring not projected on the midrib on the abaxial
surface..................................................................................8
8 Accessory bundles surround by the fibrous ring of the
midrib completely...................................... B. catarinensis
8′ Accessory bundles surround the fibrous ring of the midrib partially................................................. B. microspadix
9 Midrib protruding from the abaxial surface.................10
9′ Midrib not protruding from the abaxial surface..........13
10 Main vascular system of midrib composed of two collateral bundles.........................................................................11
10′ Main vascular system of midrib composed of three or
more collateral bundles…..............................................12
11 Fibrous ring continuous..................... B. lepidotispatha
11′ Fibrous ring discontinuous............. B. matogrossensis
12 Fibrous ring of the midrib connected to the hypodermis............................................................ B. paraguayensis
12′ Fibrous ring of the midrib not connected to the hypodermis............................................................ B. leiospatha
13 Fibrous ring projected on the midrib on the abaxial
surface…............................................................................. 14
13′ Fibrous ring not projected on the midrib on the abaxial surface........................................................................... 17
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In transverse sections, the midrib was truncate (Fig. 2F),
round (Fig. 2G) or triangular (Fig. 2H); the last one was
exclusive of B. marmorii. The expansion tissue was either
continuous (Fig. 2I)—the two caps are connected—or discontinuous (Fig. 2J)—the two caps are separated. The discontinuous expansion tissue was observed in 10 out of 18
species. Regardless of the continuity of the expansion tissue, in 12 species, it was three-layered (Fig. 2G), sometimes
with four or more layers (Fig. 2F) or two-layered (Fig. 2H).
The fibrous ring that surrounds the vascular system of
the midrib is connected to the abaxial hypodermis (Fig. 2H)
in four species. Nonetheless, most species possess at least
one layer of chlorenchyma between the fibrous ring and
the hypodermis (Fig. 2F and G). The midrib is slightly protruding from the abaxial surface of four species (Fig. 2H).
The fibrous ring is discontinuous only in B. matogrossensis
(Fig. 2K), while in the remaining species, it is continuous,
as observed in B. lallemantii and B. yatay (Fig. 2L and M,
respectively). In seven species, the fibrous ring is protruding in the abaxial side (Fig. 2J), a feature that is absent in
the remaining species, as seen in B. catarinensis (Fig. 2F)
for example. Six species possess the vascular system composed of two collateral bundles (Fig. 2L), while the remaining possess three or more collateral bundles (Fig. 2M).
The accessory vascular bundles surround the fibrous
central ring completely in B. catarinensis (Fig. 3A) and
B. odorata. These accessory bundles also showed variation in number and size of sclerenchymatic sheath reinforcement. Regarding their number, five classes (in series
of five bundles) are being proposed here. Class I (two to
seven bundles) occurs only in B. eriospatha, while Class II
(8 to 13 bundles) occurs in three species. class III (14 to
19 bundles) was observed in six species, while Class IV
(20 to 25 bundles) was observed in six species. class V (26
to 31 bundles) was observed in B. marmorii only (Fig. 3C).
Three types of sheath reinforcement were observed concerning its size. Species with type 1—five of them—contain a single huge vascular bundle in calibre compared to
the remainder (Fig. 3A). Most species showed the type 2,
in which two huge vascular bundles in calibre compared
to the remainder (Fig. 3B). Type 3, whose all accessory
bundles are minute and approximately with the same
size (without any huge vascular bundle), was observed
only in three species (Fig. 3C).
Regarding the epicuticular wax, two species showed
no conspicuous deposition (type 1) (Fig. 3D and E). The
other species showed conspicuous depositions of wax
either in horizontal plates (type 2) (Fig. 3F and G) or
associated with filaments hook-shaped (type 3) (Fig. 3H
and I). The latter was observed in 13 species.
Thirteen species have their stomata coated by epicuticular wax, and other four species do not—e.g. B. exospadix (Fig. 4A). In those species with uncoated stomata,
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Figure 3. (A) Accessory vascular bundles (A–C) and epicuticular waxes types (D–I) of Butia catarinensis (A), B. yatay (B), B. marmorii (C),
B. leptospatha (D and E), B. microspadix (F and G) and B. pubispatha (H and I). (A) Accessory vascular bundles surround the fibrous central ring
completely (grey arrow) and a single vascular bundle with sheath reinforcement (white circle). (B) Two bundles with a sheath reinforcement
(white circles). (C) Accessory bundles with the same size. (D and E) No conspicuous deposition of epicuticular waxes. (F and G) Horizontal
plates (HP) of epicuticular waxes. (H and I) Horizontal plates of epicuticular waxes associated with filaments hook-shaped (GF).
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14 Expansion tissue four-layered...................................... 15
14′ Expansion tissue three-layered…...............................16
15 Accessory bundles surround the fibrous ring of the
midrib completely.............................................. B. odorata
15′ Accessory bundles surround the fibrous ring of the
midrib partially........................................................ B. yatay
16 All accessory bundles of the midrib without
a greater reinforcement of sclerenchymatic
sheath......................................................... B. purpurascens
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16′ One accessory bundle of the midrib with greater reinforcement of sclerenchymatic sheath..... B. archeri
17 Main vascular system of midrib composed of two collateral bundles.............................................. B. lallemantii
17′ Main vascular system of midrib composed of three or
more collateral bundles…............................ B. eriospatha
The resulting dendrogram identified two main groups,
here called A and B (Fig. 5). Group A includes B. odorata,
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Figure 4. Epicuticular waxes and stomatal position of Butia exospadix (A and B), B. catarinensis (C–E) and B. campicola (F and G) in frontal view
(A, C and F), transversal (B, D and G) and longitudinal section (E). (A) Uncoated stomata. (B) Stomata in the same level of ordinary epidermal
cells. (C–E) Coated stomata sunken within the epidermis. (F) Coated stomata. (G) Stomata at the level of ordinary cells. HP, horizontal plates;
GF, filaments hook-shaped; OC, ordinary cell; GC, guard cell.
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Table 1. Anatomical characters used for the multivariate analysis.
Characters
Species B. archeri B. campicola B. capitata B. catarinensis B. eriospatha B. exospadix B. lallemantii B. leiospatha B. leptospatha B. lepidotispatha B. marmorii B. matogrossensis B. microspadix B. odorata B. paraguayensis B. pubispatha B. purpuracens B. yatay
PR
1
1
1
0
1
0
0
1
0
1
0
1
0
0
1
0
0
0
1
1
1
1
1
1
0
1
0
0
0
0
0
0
0
0
0
I
1
0
0
0
0
0
0
1
0
1
1
1
1
1
1
1
1
1
Tru
1
1
0
0
1
1
1
1
1
0
0
1
1
1
1
0
0
1
Rou
0
0
1
1
0
0
0
0
0
1
0
0
0
0
0
1
1
0
Tri
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
Stomata
BL
1
0
1
1
1
0
1
1
0
1
1
1
0
1
1
0
1
1
position
SL
0
1
0
0
0
1
0
0
1
0
0
0
1
0
0
1
0
0
ABSCM
0
0
0
1
0
0
0
0
0
0
0
0
0
1
0
0
0
0
FRMH
0
0
0
0
0
1
0
0
0
0
1
0
0
0
1
1
0
0
PCFRH
1
0
1
1
1
0
1
1
1
1
1
1
1
0
1
1
1
1
T1
0
0
0
0
0
1
0
0
1
0
0
0
0
0
0
0
0
0
T2
0
0
0
0
1
0
0
0
0
0
0
0
1
1
0
0
0
0
T3
1
1
1
1
0
0
1
1
0
1
1
1
0
0
1
1
1
1
2–7
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
8–13
1
0
1
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
14–19
0
0
0
1
0
0
1
1
0
1
0
0
1
0
0
1
0
1
20–25
0
1
0
0
0
1
0
0
1
0
0
1
0
1
0
0
1
0
26–31
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
2
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
3
1
1
1
0
0
1
1
1
1
1
0
1
1
0
1
1
1
1
4
0
0
0
1
1
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
1
0
0
0
0
0
1
0
1
1
0
0
1
1
0
0
0
0
0
0
0
1
0
1
0
0
0
2
0
1
1
0
0
1
1
1
0
1
0
1
0
1
0
1
0
1
1
0
0
1
1
1
0
0
0
0
1
0
1
0
1
0
0
0
0
2
1
1
0
0
0
1
1
1
1
0
1
0
1
0
1
1
1
1
0
0
0
0
0
0
0
1
0
1
1
1
0
0
1
0
0
0
1
1
0
0
0
0
0
0
1
0
0
0
0
1
1
0
1
1
2
0
0
1
0
0
0
1
0
1
1
1
1
0
0
0
0
0
0
≥3
1
1
0
1
1
1
0
1
0
0
0
0
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
1
0
1
0
0
0
0
Midrib shape
EW
NABMMVS
ETE
NABGRESM
NABGRESLM
MPAb
FRSMVMAb
NCBMMVS
FRSMVM
PR, presence of raphides; ET, expansion tissue (C = continuous, I = interrupted); cross-sectional shape of the midrib (Tri = triangular, Rou = rounded, Tru = truncated); SL, stomata at the same
level of epidermis; BL, stomata below the level of the epidermis; ABSCM, accessory bundles surrounding completely the main vascular system of the midrib; FRMH, fibrous ring surrounding
the vascular system of the midrib reaching the hypodermis; PCFRH, presence of at least one chlorenchyme layer between the fibrous ring and the hypodermis; EW, epicuticular waxes
the midrib main vascular system; ETE, expansion tissue stratification (2, 3 or 4 cell layers); NABGRESM, number of accessory bundles with greater reinforcement of sclerenchymatic sheath
in midrib; NABGRESLM, number of accessory bundles with greater reinforcement of sclerenchymatic sheath in leaf margin; MPAb, midrib projected on the abaxial surface; FRSMVMAb,
fibrous ring surrounding the main vascular system of the midrib projected towards the abaxial surface; NCBMMVS, number of collateral bundles in the midrib main vascular system;
FRSMVM, fibrous ring wholly surrounding the main vascular cylinder in midrib.
9
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© The Author(s) 2018
(T1 = inconspicuous deposits, T2 = deposit of horizontal plates, T3 = deposits of horizontal plates associated with hook-shaped filaments); NABMMVS, number of accessory bundles around
Sant’Anna-Santos et al. – Leaf anatomy of Butia species
0
C
ET
Sant’Anna-Santos et al. – Leaf anatomy of Butia species
B. eriospatha and B. catarinensis, while group B includes
the remaining 15 studied species of Butia. The characters that differentiate each group are four-layered
expansion tissue (group A) and two- or three-layered
expansion tissue (group B).
Within group B, five subgroups can be recognized.
One of such subgroups is the group B1, composed
of B. exospadix, B. campicola and B. leptospatha and
share 10 characters, such as the presence of raphides and stomata at the same level of other epidermal
cells. We found greater similarity between B. exospadix
and B. campicola, corroborated by the presence of two
accessory bundles of greater calibre within the midrib.
Butia marmorii alone composes group B2, which can be
characterized by a more or less triangular midrib, 16–31
vascular bundles surrounding the midrib and two-layered
expansion tissue. The group B3 is composed of B. matogrossensis, B. lallemantii, B. lepidotispatha and B. capitata
that share some relevant characteristics such as stomata below the remaining epidermal cells, the vascular
system of the midrib composed of two opposed bundles.
Nevertheless, there is no exclusive character for this group.
Species included within group B4 (B. pubispatha and
B. microspadix) share the highest number of anatomical
characters (12), such as stomata at the same level of
the remaining epidermal cells.
The group B5 is composed of five species lacking
raphides (B. paraguayensis, B. archeri, B. purpurascens,
B. yatay and B. leiospatha). Regarding species within
group B5, our analysis could not discriminate between
B. paraguayensis and B. archeri based on pinnae anatomy. This similarity is mainly due to the presence of 8 to
13 vascular bundles around the vascular system of the
midrib and the presence of only one accessory bundle
10
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of greater calibre within the midrib, characteristics not
shared with the other species of the group.
Discussion
The broader sampling of Butia in the present study
confirms the presence of many characters common
to the genus, such as isobilateral mirrored mesophyll,
amphistomatic leaves and vascular bundles with a sclerenchymatic sheath reinforcement connected to the
hypodermis, as previously described (Tomlinson 1961;
Tomlinson et al. 2011). Those authors also pointed out
the structural divergence between the mesophyll of
Butia and its sister group, Jubaea (sensu Meerow et al.
2009, 2015). Now that more species of Butia have been
analysed both by molecular phylogenetic (Meerow et al.
2015) and structural analyses (this study), it is possible
to propose the mirrored isolateral mesophyll of Butia
not only as diagnostic of the genus but as well as a
synapomorphy.
The species groups in the dendrogram reflect some of
the already established taxonomic issues for the genus,
morphological similarities or geographical proximity.
Group A, represented by B. catarinensis, B. odorata and
B. eriospatha, were never reported as problematic in distinction. Notwithstanding, these species naturally occur
in relatively close areas, but the presence of raphides is
restricted to B. catarinensis. Thus, anatomically, it is possible to distinguish them using a reliable character that
is easy to obtain and recognize.
Butia catarinensis and B. odorata stand out for presenting accessory bundles surrounding the vascular
system of the midrib, which do not occur in B. eriospatha. This character has been previously observed in
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Figure 5. Dendrogram of similarity between Butia species based on leaf anatomy.
Sant’Anna-Santos et al. – Leaf anatomy of Butia species
Table 2. Useful anatomical characters for Butia taxonomy.
Characters
Jaccard index
Number of accessory bundles around the main vascular system of the midrib
0.71
0.62
Presence/absence of raphides
0.52
Shape of the midrib in transverse section
0.50
Characteristic of expansion tissue (continuous or interrupted)
0.50
Fibrous ring surrounding the main vascular system of the midrib projected towards the abaxial surface
0.50
Number of collateral bundles in the main vascular system of the midrib
0.47
Number of accessory bundles with greater reinforcement of sclerenchyma sheath at the leaf margin
0.47
Expansion tissue stratification
0.45
Midrib projected on the abaxial surface
0.42
Position of stomata in relation to ordinary epidermal cells
0.42
Distribution pattern of epicuticular waxes
0.39
Fibrous ring of the vascular system of the midrib reaching the hypodermis
0.37
Accessory bundles surrounding the main vascular system of the midrib completely
0.21
Fibrous ring surrounding the main vascular cylinder in the midrib completely
0.11
B. odorata (Sant’Anna-Santos et al. 2015). Butia odorata
has natural populations occurring near to B. catarinensis
and disjunct by a narrow strip of seacoast (Noblick 2010).
Although there are no reported difficulties to distinguish
both species, the size of specimens and the shape and
size of reproductive organs, the most commonly used
characters to separate them, are known to be variable
within the genus (Glassman 1970; Noblick 2010, 2014;
Soares et al. 2014). Thus, for a reliable identification, the
presence of raphides in B. catarinensis can be used to
distinguish it from B. odorata and B. eriospatha.
Within group B, the first group of species is B1, which
includes B. exospadix, B. campicola and B. leptospatha
and belong to the same complex of species: the ‘grassy
Butia’ (Noblick 2006). Morphologically, this group share
many similarities, including the notorious graminoid
size (Noblick 2006). However, the papyraceous minute
peduncular bract of B. leptospatha (also observed in
B. marmorii) notoriously distinguishes it from the other
two species of group B1. Anatomically, B. leptospatha
differs from B. campicola and B. exospadix by the number
of vascular bundles within the midrib. Although B. leptospatha can be easily distinguished by its morphology,
when devoid of inflorescences, the characters observed
here assume great relevance. Butia leptospatha occurs
remarkably near to the natural areas of occurrence of
the other species within group B1. Butia campicola and
B. exospadix morphologically also share many similarities and, according to Noblick (2010), ‘grassy Butia’
whose inflorescence is greater than the bract. The most
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obvious morphological difference lies in the size of the
leaf rachis, much longer in B. campicola (Noblick 2010).
Anatomically, the hook-shaped filaments, within this
group, are unique to B. campicola, which may be useful
to differentiate the latter from B. exospadix and B. leptospatha. This is especially relevant when there are doubts
about the juvenility of the specimen, a factor that influences the size of the vegetative parts, as reported by
Glassman (1970).
Group B2 is composed of B. marmorii only,
differentiated from the other species by a peculiar leaf
anatomy represented by three exclusive anatomical
characters (EAC) (stratified two-layered expansion
tissue, triangular midrib and 26–32 accessory bundles
in the midrib). Those characters distinguish it from the
other 17 species studied here. Butia marmorii is only
known from a small area in Paraguay (Noblick 2010) and
is one of the representatives of the grassy complex of
Butia; Noblick (2010) pointed out a great morphological
similarity between B. marmorii and B. leptospatha.
Although there is no history of problems in distinguishing
these species, the proximity of their areas of occurrence
and make the EACs observed here are valuable. The
remaining grassy complex, formed by B. pubispatha and
B. microspadix (Noblick 2010), was included within group
B4. Butia pubispatha was first collected and erroneously
identified as B. microspadix, as reported by Noblick
(2010). Morphologically, they can be distinguished by
the indument; size of bract and number of rachillae.
These characters can be influenced by environmental
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Number of accessory bundles with greater reinforcement of sclerenchyma sheath in the midrib
11
Sant’Anna-Santos et al. – Leaf anatomy of Butia species
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although very similar, they also have a remarkable
character that differentiates them: the presence of
discontinuity points within the fibrous ring of the midrib
of B. matogrossensis, an EAC of this species.
Within group B5, B. paraguayensis appears together
with B. archeri, with only two different characters,
which, in our analyses, were not enough to discriminate
between these species. Nevertheless, B. archeri and
B. paraguayensis are morphologically highly distinct
and, to the best of our knowledge, do not occur
sympatrically (although the southern limit of the
populations of B. archeri being close to the northern limit
of B. paraguayensis). There are no reports that these two
are related species or even difficulty in their separation.
As B. paraguayensis form a highly variable group, difficult
to understand and probably form a complex and not
a single species (Noblick 2014), a broader systematic
study, using molecular tools and analysing several
populations, is fundamental to elucidate better any
questions relating to this group. We analysed samples
from other populations of B. archeri too, indicating
reliability in the use of these data presented here.
Within the other terminal of group B5, B. yatay
and B. leiospatha are very similar. However, there
are no reports of taxonomic problems and sympatric
occurrence between them. Butia leiospatha has
been anecdotally cited as a dwarf form of B. archeri
(Plantarum Botanical Garden website, 2018), species
also belonging to group B5. Presently, B. leiospatha
is considered as a synonym of B. capitata. However,
there are many anatomical differences between these
species, including four characters with the highest value
of Jaccard index. Butia leiospatha does not appear on
the list of species of Noblick (2014), which shows that
its status as a questionable species is still a consensus.
Although it does not present any EAC, the anatomical
data presented here support its segregation both from
B. archeri and B. capitata. Due to the lack of a reliable
type of B. leiospatha, it is premature to suggest its
reinstatement as a valid species, especially because
the specimen here analysed and previously identified
as B. leiospatha could as well represent a new species.
Thus, it is urgent to analyse this issue more thoroughly
and review the status of this taxa.
Butia paraguayensis and B. yatay are difficult to
understand due to the high morphological variability of
their populations (Noblick 2014). Butia yatay is the only
group B species that possesses a group A character (fourlayered expansion tissue). Nonetheless, this exception
can be explained by the close relationship between
B. odorata and B. yatay, demonstrated by molecular
phylogenetic analyses by Meerow et al. (2015). Butia
paraguayensis has already been considered as a variety
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conditions (Metcalfe and Chalk 1979; Fahn and Cutler
1992), besides occasionally appear in certain species of
the genus (Soares et al. 2014) and only become available
during the reproductive period. Thus, it is expected
that only experienced taxonomists have no difficulty
in distinguishing between related species that occur in
the same area, as already reported for these species
(Noblick 2010). It thus becomes clear that data on the
leaf anatomy, organ available throughout the year,
contribute to distinguishing these two species. Therefore,
anatomically these species can be distinguished by four
characters, with an emphasis on the type of epicuticular
wax (horizontal plates in B. microspadix and hookshaped filaments in B. pubispatha), which, according to
Barthlott (1981), is reliable for taxonomic purposes.
Group B3 includes B. capitata, B. lepidotispatha,
B. lallemantii and B. matogrossensis. The last one can be
easily confused with B. capitata when juvenile (Noblick
2010). However, anatomically, they can be discriminated
based on nine characters, including the presence of
raphides, which is restricted to B. capitata. Butia capitata
is anatomically similar to B. lallemantii, but the latter
is known from cespitose endemic specimens from the
Rio Grande do Sul State, while B. capitata, in general, is
represented by solitary individuals with apparent stipe
from the Brazilian Central Plateau. There is, therefore,
between these two species, not only a wide range
of geographical but also morphological disjunction.
Similar to B. paraguayensis, B. capitata seems to be a
highly variable species (Glasmann 1970), and a broader
taxonomic study is fundamental to better elucidate any
questions regarding this group. It is worth mentioning
that the anatomical characteristics observed in the
present study in B. capitata (presence of raphides,
midrib format, expansion tissue, accessory bundles
and others) were similar to those of B. odorata and
previously reported by Sant’Anna-Santos et al. (2015).
Moreover, we analysed samples from other populations
of B. capitata, indicating reliability in the use of these
data presented here.
Butia lepidotispatha and B. matogrossensis consist of
species that occur in different areas from Mato Grosso
do Sul State (Noblick 2010). However, both were recently
described, and it is likely that future collections will
indicate a closer relationship between their populations.
Morphologically, we find it difficult to distinguish
B. lepidotispatha from B. matogrossensis. However, the
lepidote indument of the stalk is indeed noticeable
in B. lepidotispatha, and Noblick (2010) considers as a
consistent and remarkable character for the species.
Notwithstanding, according to Soares et al. (2014), this
feature seems to be very variable, as it may occasionally
appear in other species of the genus. Anatomically,
Sant’Anna-Santos et al. – Leaf anatomy of Butia species
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even species that have been described for decades and
are still questionable.
Based on the external morphology, Noblick (2014)
mentioned in his recent work: ‘I am not even going to
pretend that I could really write a decent key to all of the
Butia’. We believe that the key proposed here will, then,
besides the two keys already proposed by Noblick (2010)
and Soares et al. (2014), help expand our understanding
of the genus and facilitate the identification of species.
Keys including anatomical data are already being used
in genus related to Butia, Syagrus for instance (Noblick
2013), and have shown great taxonomic potential and
grounded the description of new species, as in Allagoptera
(Martins et al. 2015; Pinedo et al. 2016). New anatomical data are especially valuable for extremely variable
groups, like genera with species complex and many
taxonomic issues. Also, such data have been used as an
argument to raise or not a certain taxon, as observed in
Noblick (2013, 2014) and Martins et al. (2015).
Conclusion
The anatomical data proposed here enabled us to
develop a purely anatomical key, in which specific identification is performed by a set of characters up to five.
Also, two species can be identified by exclusive characters. The key proposed here has new and relevant
characters for identification and can assist in solving
taxonomic problems in Butia.
Previous studies on other groups of Arecaceae have
successfully applied leaf characters to aid in species
identification and to help to explain their evolutionary
history (e.g. Noblick 2013). Thus, it is somewhat surprising the incongruence between the groups of species
recovered by our analyses of the leaf anatomy and those
depicted in the most recent molecular phylogenetic
tree that included Butia (Meerow et al. 2015). These
authors analysed seven species belonging to Butia and
confirmed its monophyly and Jubaea as its sister clade.
Notwithstanding, their analyses could not resolve the
relationship between Butia species. In spite of being
the first branch to diversificate within South America,
Jubaea and Butia have diverged more recently than
other genera belonging to Attaleinae (Meerow et al.
2015) and it is possible that the leaf diversity found in
the present study is a reflex of this recent divergence.
Given the dates of divergence estimated by the analyses of Meerow et al. (2015), fluctuations in the distribution of rainforest and seasonally dry climates in South
America after the Andean uplift are likely responsible
for many speciation events within Butia, prompting the
extant leaf diversified anatomy, adapted to the different climatic conditions. Due to the limited sampling in
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of B. yatay (Beccari 1916), but nowadays, instead, is a
recognized taxon. Our data allow the differentiation
between the former and the latter by eight characters,
four of them with the highest values of Jaccard index.
In Brazil, the geographical distribution of these species
has a disjunction in the Rio Grande do Sul State:
B. paraguayensis occurs more to the northwest of the
state, while the natural populations of B. yatay are
restricted to the southwest (Noblick 2010). However,
in Argentina, B. paraguayensis specimens have been
identified in areas of occurrence of B. yatay, which,
according to Noblick (2014), might be a mistake. In
Uruguay, the only existing population of B. paraguayensis
was called by Noblick (2014) as an ‘odd disjunct
population’, reaffirming the difficulty of identifying this
species only by characters of the external morphology.
Thus, the anatomical features identified here shall be
considered for correct identification.
Still, regarding group B5, B. purpurascens appears
on the base of the group within the dendrogram and,
accordingly, is anatomically distinct from the remaining
species. In the literature, there are no reports of difficulties in its identification, but its anatomical similarity to
B. paraguayensis, B. archeri and B. leiospatha coincides
with the type of environment in which they occur: sandy
soil savannas (Noblick 2010).
Raphides were observed in seven of the studied species, not being a unifying character to Butia. However,
this character is helpful to differentiate species that
sometimes are confused. Among all the evaluated traits,
raphides may show a few major advantages: convenience and low cost for obtaining the data, easy visualization and reliability for species distinction, having already
been used successfully to discriminate between other
morphologically similar Butia (Sant’Anna-Santos et al.
2015).
Even though it has been useful in distinguishing species from other genera, such as Allagoptera (Pinedo et al.
2016), Oenocarpus (Silva and Potiguara 2008; Tomlinson
et al. 2011) and Syagrus (Noblick 2013), the leaf margin format showed intraspecific variation in part of the
Butia species analysed here, reason that justified the
exclusion of this character in the proposed key. Even
when not variable within the same species, data such as
epicuticular wax (Barthlott 1981) require more refined
and costly methodologies. In this case, it is expected
that the use of costly equipment may be an obstacle
and limit the use of such data in taxonomic routine.
As pointed out by Noblick (2014), considering the total
number of Butia species described, solving taxonomic
problems should be a priority in genus like Butia, morphologically very variable, with doubtful circumscription
and composed of species complexes, new species and
13
Sant’Anna-Santos et al. – Leaf anatomy of Butia species
previous analyses and the possibility of a recent diversification in Butia, it is necessary to carry out a new
molecular phylogenetic analysis, including more species
and using other molecular markers, more adequate to
account for a higher diversification rate.
Sources of Funding
Contributions by the Authors
B.F.S.-S. and W.G.O.C.J. posed the central questions;
S.A.S., B.F.S.-S. and D.M.T.F. performed the microscopic
analysis; the authors analysed the data together;
B.F.S.-S., S.A.S. and E.L.P.N. wrote the original manuscript; E.L.P.N. and B.F.S.-S. edited for content and provided guidance on structure and style.
Conflict of Interest
None declared.
Acknowledgements
We thank the Jardim Botânico Plantarum (Agreement
nº48/12-00) for the collection permit and their
logistic support. We acknowledge the assistance of Dr
Claudinei S. Fior and Dra Érica D. Silva (Universidade
Federal do Rio Grande do Sul—UFRGS) with the collection
of B. odorata’s samples, Juan S. V. Chamba, Marcony N.
Coutinho and Larisse de F. Silva with light microscopy
processing. We are thankful for the valuable comments
on this manuscript by two anonymous reviewers and
the Associate Editor. This work received the support of
the Laboratório de Anatomia e Biomecânica Vegetal
from the Universidade Federal do Paraná (LABV–UFPR)
and the Núcleo of Microscopia e Microanálise from the
Universidade Federal de Viçosa (NMM–UFV) for light and
electron microscopy analyses.
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