Pedro Schwambach de Almeida

1 IntroductionBromeliaceae is an early diverging monocot family within the order Poales (Bouchenak-Khelladi et al., 2014). Traditionally, the family was divided into three subfamilies based mainly ...

Bromeliaceae exhibits significant pollen diversity. Within the family, pollen grains are dispersed either as monads or tetrads and may be monosulcate, bi-, tri-, tetra-, or pantoporate, or even inaperturate. Ornamentation includes reticulate, foveolate, microreticulate, perforate, or psilate patterns. Additional variations are observed in the margins of the apertures and in the exine deposition on the aperture membrane. In general, pollen grains are relatively well-documented in Bromeliaceae. However, there is a lack of systematization and organization to provide a comprehensive and integrated understanding of its pollen structure. This study aims to conduct a general review of pollen morphology in Bromeliaceae, analyze character diversity based on the current phylogeny of the family, and propose the ancestral states of pollen traits. The study sampled 127 species from 47 genera, supplemented by literature data of 220 species (from 14 additional genera). Together, this dataset encompasses over 70% of the genera in the family and includes species from all subfamilies. Ancestral character states were inferred through a maximum parsimony approach. The identified ancestral states include monads as the dispersal unit, heteropolarity, bilateral symmetry, medium size, a basic elliptical shape, monosulcate pollen, a simple sulcus type, margin type III (Puya type), and reticulate ornamentation. Bromelioideae is eurypalynous, with a predominance of biporate pollen grains in Core Bromelioideae. Tillandsioideae is considered stenopalynous, characterized by monosulcate pollen grains. However, the subfamily shows considerable variation in sulcus types. Pitcairnioideae is also stenopalynous and monosulcate but exhibits significant variation in the sulcus and ornamentation. The remaining subfamilies display less variation and are stenopalynous. This study provides a comprehensive overview of pollen diversity in Bromeliaceae and highlights its evolutionary patterns, offering a basis for further research on character evolution and systematics of the family.

Bromelioideae exhibits high variability in pollen characters and is therefore eurypalynous. Palynological studies have described numerous genera within the subfamily, contributing to a more precise circumscription at generic and infrageneric levels. However, most studies have focused on surface analyses or observations of the sporoderm in pollen grains lacking cytoplasmic content (lux obscuritas microscopy). As a result, characters describing internal structures that are not resistant to acetolysis, such as the intine, have been less frequently addressed. This study aimed to describe the pollen types found in Bromelioideae by analysing the sporoderm surface and stratification patterns using a combination of anatomical techniques, acetolytic treatment, and scanning electron microscopy. The results confirmed the palynological diversity of Bromelioideae, revealing variations in pollen size, shape, dispersal unit, aperture number, ornamentation, and infratectum types. Differences were also observed in sporoderm stratification, aperture type, and aperture margins. The intine exhibited remarkable diversity, being predominantly stratified into three layers, with distinct patterns observed in some species. A structurally unique feature was identified in diporate grains, here referred to as the pseudoannulus.

The authors describe and illustrate a new species of Cryptanthus, C. pataxoanus, found within the Monte Pascoal National and Historical Park, and present new data on its closest morphological relative, C. beuckeri, both endemic to the Atlantic Forest of the state of Bahia, Brazil, and assessed as Critically Endangered (CR). The new taxon represents one of the most ornamental discoveries in recent years due to its marbled foliage, with contrasting greenish-yellow and dark green colors, which is similar to C. beuckeri. The main differences between C. pataxoanus and its closest relative include leaf blades not petiolate or the basal ones sometimes subpetiolate, the much broader portion of the blades distinctly longer, the narrower sepals covered by brown-centered trichomes, and petals without glandulose trichomes. The discovery of the new species results from cooperative work with the Pataxó indigenous community living in Barra Velha and Barra Velha do Monte Pascoal Indigenous Lands, located within the boundaries of the Monte Pascoal National and Historical Park. It symbolizes the inexhaustible richness of the Brazilian biodiversity in general and the Atlantic Forest of southern Bahia in particular, despite its current coexistence with high levels of threat.

A new species of Hoplocryptanthus, a member of the bromelioid “Cryptanthoid complex”, is described based on plants discovered in a ferruginous rupestrian grassland located in the southern Iron Quadrangle region, Minas Gerais state, Brazil. Hoplocryptanthus serrapiresensis is endemic to the Pires Range, a region under strong threat by mining exploitation. The morphological characters of H. serrapiresensis are discussed in comparison with H. knegtianus and H. tiradentesensis. This microendemic species is assessed as Critically Endangered (CR), reinforcing the need for a strategy to protect the biodiversity of the region. Characters related to leaves proved useful in the taxonomic delimitation of this new species. Morphological analyses also validated and reinforced the diagnostic floral and inflorescence characters used in the circumscription of Hoplocryptanthus.

The taxonomic circumscription of many bromeliad species is doubtful, and this is the case for Dyckia alba. We explore unusual characters from several data sources, such as macromorphological, floral micromorphological, floral anatomy, and palynological, to more accurately circumscribe D. alba. In light of these data, we concluded that the originally proposed circumscription for D. alba covers two independent lineages that should be treated as two species. As a result, we propose a less comprehensive circumscription for D. alba and the segregation of a new species, described here as Dyckia witeckii. Morphological descriptions of the vegetative and reproductive organs are presented for both species, as well as little-explored morphological features in Dyckia, such as the micromorphology of perianth trichomes and pollen, along with the floral anatomy. We also provide, for both species, data on geographic distribution and habitat. Comparative morphoanatomy proved to be an important tool in this study and has great potential for application in taxonomic studies of Bromeliaceae.

The genus Wittmackia has 44 species distributed in two centers of diversity: the Brazilian clade and the Caribbean clade. The Brazilian clade includes 29 species, with geographic distribution concentrated in the Northeast of Brazil. This study reports the morphology, ultrastructure, pollen viability and stigma receptivity by different microscopy techniques of 23 species of the genus Wittmackia endemic to Brazil and occurring in Atlantic Forest areas. Pollen morphology was evaluated by scanning electron microscopy and light microscopy by the weak lactic acetolysis method. Histochemical tests were performed with Alexander's solution and fluorescein diacetate. For in vitro germination of pollen grains, two culture media were evaluated. Stigma receptivity was evaluated with hydrogen peroxide and α‐naphthyl acetate. The Wittmackia genus presented biporate pollen grains, monads to tetrads, with oblate, suboblate or oblate‐spheroidal shape, circular or elliptical scope, and heteropolar or sub‐isopolar morphology. The stigmas are of the conduplicate‐spiral type, with differences in color and size. In both histochemical tests, high viability was observed, mainly at anthesis, coinciding with in vitro germination. The species presented high enzymatic activity during receptivity, with a very strong positive response, mainly at anthesis. Studies of pollen morphology and viability provide important information for the conservation and genetic improvement of Wittmackia species, also assisting in the taxonomy of the genus and the reproductive success of future controlled crosses.

Dyckia, belonging to the Bromeliaceae, consists of species that share several morphological similarities. Recently, a proposal has grouped 13 species of the genus into a “D. selloa complex” based on their limited geographical distribution and seed characteristics. However, further investigation is required to gain a better understanding of this grouping. This study aimed to analyze the pollen grain morphology of the grouped species. The analysis was conducted using scanning electron microscopy (SEM), as well as light microscopy equipped with bright field and fluorescence optics. Various structures were measured. The pollen grains are heteropolar, oblate, and range in size from small to medium. They possess a simple sulcus type and exhibit a sexine (composed of tectum and infratectum columellate) and a nexine 1. Different patterns of ornamentation were identified, including reticulate, microreticulate, reticulate with free granules, reticulate with a partially discontinuous reticulum, and reticulate with a discontinuous reticulum. The aperture margin of some species differs from the described characteristics for the genus (Puya type) and is referred to here as the “Other” type. The results align with existing data for the genus Dyckia and contribute to understanding the pollen morphology within the genus and the studied group. The data obtained in this study, along with the observed variations, could facilitate a better understanding of the “D. selloa complex”.

A new species of Krenakanthus, a member of the bromelioid “Cryptanthoid complex”, is described based on plants discovered through collaborative citizen science. Krenakanthus ribeiranus and its only congener K. roseolilacinus are endemic to the “João Pinto Center of Biodiversity”, a still poorly explored region with Campos Rupestres and associated vegetation in the Rio Doce Valley, in eastern Minas Gerais state, Brazil. The unusual combination of morphological characters of K. ribeiranus, highlighted by plant delicacy and almost all leaf and flower parts covered by uniseriate, hair-like trichomes, is illustrated and discussed in comparison with K. roseolilacinus, including leaf and seed anatomy, as well as pollen morphology. This micro-endemic species is assessed as Critically Endangered, reinforcing the need for strategy to protect the biodiversity of the region. The morphology of the new species validates and strengthens the diagnostic flower characters used in the circumscription of Krenakanthus, suggesting as secondary diagnostic characters the habit, stature, and leaf conformation.