Ruellieae is a highly diverse tribe of Acanthaceae in Brazil, and morphological studies of its seeds have revealed important information about the systematics of the tribe. We analyzed the seed morphology of Brazilian species of Ruellieae, using stereoscopic, light, and scanning electron microscopy. The best-sampled genus was Ruellia (53 species), followed by Dyschoriste (seven), and Hygrophila (three); including external groups, a total of 65 species of Ruellieae (68 of Acanthaceae) were sampled. We observed capsular fruits with explosive dehiscence, important for autochory, and discoid seeds covered by hygroscopic and mucilaginous trichomes. The characters most relevant to the taxonomy of the groups were fruit shape, number of ovules, and the distribution, shape, and number of rings on the seed trichomes, the latter two addressed here for the first time. Those characters proved useful for discriminating and characterizing the sampled genera within Ruellieae, and especially the infrageneric clades of Ruellia. Based on the morphological patterns observed, we provide a key for those taxa, and suggest the infrageneric placement of unclassified Ruellia species: R. hypericoides and Ruellia sp. 4 for the clade “Ebracteolati” s. l., Ruellia spp. 2 and 3 for “R. inflata”, Ruellia sp. 1 for “Euruellia” s. s., and R. anamariae for the clade “Blechum”. In a broader context, we corroborate the finding that partial loss of seed trichomes is exclusive to one of the two large lineages of Neotropical Ruellia (lineage II). The hygroscopic and mucilaginous trichomes of Ruellieae seeds play important roles in water retention, germination, protection, and secondary dispersal, and we discuss some aspects of secondary hydrochory and epizoochory on medium- and long-range dispersal of Ruellieae, including transatlantic distances.
Supplemental Figure 1
Fruits and seeds of Dyschoriste species. A–E. D. humilis (STM on A, SEM on B–E): A–B. Seed. C. Seed apex. D. Seed base. E. Seed trichomes with secondary annular thickenings. F–K. D. hygrophiloides (STM on F–G, SEM on H–K): F. Fruit. G–H. Seed. I. Seed apex. J. Seed base. K. Seed trichomes with secondary annular thickenings. L–R. D. lavandulacea (STM on L–M, SEM on N–R): L. Fruit. M–N. Seed. O. Seed apex. P. Seed base. Q. Seed trichomes with secondary annular thickenings. R. Hilar cells, some partially differentiated into trichomes. S–T. D. maranhonis (STM): S. Fruit. T. Seed. [STM=stereomicroscopy; SEM=scanning electron microscopy].
SFig.1.tif
Supplemental Figure 2
Fruits and seeds of Dyschoriste species. A–D. D. maranhonis (SEM): A. Seed. B. Seed apex. C. Seed base. D. Seed trichomes with secondary annular thickenings. E–J. D. serpyllum (STM on E–F, SEM on G–J): E. Fruit. F–G. Seed. H. Seed apex. I. Seed base. J. Seed trichomes with secondary annular thickenings. K–Q. D. trichanthera (STM on K–L, SEM on M–Q): K. Fruit. L–M. Seed. N. Seed apex. O. Seed base. P. Seed trichomes with secondary annular thickenings. Q. Hilar cells, some partially differentiated into trichomes. R–T. Dyschoriste sp. (STM on R–S, SEM on T): R. Fruit. S–T. Seed. [STM=stereomicroscopy; SEM=scanning electron microscopy].
SFig.2.tif
Supplemental Figure 3
Fruits and seeds of Dyschoriste (A–D) and Hygrophila (E–T) species. A–D. Dyschoriste sp. (SEM): A. Seed apex. B. Seed base. C. Seed trichomes with secondary annular thickenings. D. Hilar cells, some partially differentiated into trichomes. E–J. H. costata (STM on E–F, SEM on G–J): E. Fruit. F–G. Seed. H. Seed apex. I. Seed base. J. Seed trichomes with secondary annular thickenings. K–Q. H. guianensis (STM on K–L, SEM on M–Q): K. Fruit. L–M. Seed. N. Seed apex. O. Seed base. P. Seed trichomes with secondary annular thickenings. Q. Hilar cells, some partially differentiated into trichomes. R–T. H. oblongifolia (STM on R–S, SEM on T): R. Fruit. S–T. Seed. [STM=stereomicroscopy; SEM=scanning electron microscopy].
SFig.3.tif
Supplemental Figure 4
Fruits and seeds of Hygrophila (A–C) and Ruellia species from the clade “Ebracteolati” (D–T). A–C. H. oblongifolia (SEM): A. Seed apex. B. Seed base. C. Seed trichomes with secondary annular thickenings. D–J. R. adenocalyx (STM on D–E, SEM on F–J): D. Fruit. E–F. Seed. G. Seed apex. H. Seed base. I–J. Seed trichomes with secondary annular thickenings. K–Q. R. angustior (STM on K–L, SEM on M–Q): K. Fruit. L–M. Seed. N. Seed apex. O. Seed base. P–Q. Seed trichomes with secondary annular thickenings. R–T. R. bahiensis (STM on R–S, SEM on T): R. Fruit. S–T. Seed. [STM=stereomicroscopy; SEM=scanning electron microscopy].
SFig.4.tif
Supplemental Figure 5
Fruits and seeds of Ruellia species from the clade “Ebracteolati”. A–C. R. bahiensis (SEM): A. Seed apex. B. Seed base. C. Seed trichomes with secondary annular thickenings. D–I. R. beyrichiana (STM on D–E, SEM on F–I): D. Fruit. E–F. Seed. G. Seed apex. H. Seed base. I. Seed trichomes with secondary annular thickenings. J–O. R. bulbifera. (STM on J–K, SEM on L–O): J. Fruit. K–L. Seed. M. Seed apex. N. Seed base. O. Seed trichomes with secondary annular thickenings. P–T. R. densa (STM on P–Q, SEM on R–T): P. Fruit. Q–R. Seed. S. Seed apex. T. Seed base. [STM=stereomicroscopy; SEM=scanning electron microscopy].
SFig.5.tif
Supplemental Figure 6
Fruits and seeds of Ruellia species from the clade “Ebracteolati”. A. R. densa (SEM): Seed trichomes with secondary annular thickenings. B–G. R. erythropus (STM on B–C, SEM on D–G): B. Fruit. C–D. Seed. E. Seed apex. F. Seed base. G. Seed trichomes with secondary annular thickenings. H–M. R. foetida (STM on H–I, SEM on J–M): H. Fruit. I–J. Seed. K. Seed apex. L. Seed base. M. Seed trichomes with secondary annular thickenings. N–T. R. geminiflora (STM on N–O, SEM on P–T): N. Fruit. O–P. Seed. Q. Seed apex. R. Seed base. S–T. Seed trichomes with secondary annular thickenings. [STM=stereomicroscopy; SEM=scanning electron microscopy].
SFig.6.tif
Supplemental Figure 7
Fruits and seeds of Ruellia species from the clade “Ebracteolati”. A–G. R. hypericoides (STM on A–B, SEM on C–G): A. Fruit. B–C. Seed. D. Seed apex. E. Seed base. F–G. Seed trichomes with secondary annular thickenings. H–M. R. incomta (STM on H–I, SEM on J–M): H. Fruit. I–J. Seed. K. Seed apex. L. Seed base. M. Seed trichomes with secondary annular thickenings. N–T. R. multifolia (STM on N–O, SEM on P–T): N. Fruit. O–P. Seed. Q. Seed apex. R. Seed base. S–T. Seed trichomes with secondary annular thickenings. [STM=stereomicroscopy; SEM=scanning electron microscopy].
SFig.7.tif
Supplemental Figure 8
Fruits and seeds of Ruellia species from the clade “Ebracteolati”. A–F. R. nitens (STM on A–B, SEM on C–F): A. Fruit. B–C. Seed. D. Seed apex. E. Seed base. F. Seed trichomes with secondary annular thickenings. G–L. R. tubiflora (STM on G–H, SEM on I–L): G. Fruit. H–I. Seed. J. Seed apex. K. Seed base. L. Seed trichomes with secondary annular thickenings. M–R. R. verbasciformis (STM on M–N, SEM on O–R): M. Fruit. N–O. Seed. P. Seed apex. Q. Seed base. R. Seed trichomes with secondary annular thickenings. S–T. R. yurimaguensis (STM): S. Fruit. T. Seed. [STM=stereomicroscopy; SEM=scanning electron microscopy].
SFig.8.tif
Supplemental Figure 9
Fruits and seeds of Ruellia species from the clades “Ebracteolati” (A–K) and “R. inflata” (L–T). A–E. R. yurimaguensis (SEM): A. Seed. B. Seed apex. C. Seed base. D. Seed trichomes with secondary annular thickenings. E. Hilar cells, some partially differentiated into trichomes. F–K. Ruellia sp. 4 (STM on F–G, SEM on H–K): F. Fruit. G–H. Seed. I. Seed apex. J. Seed base. K. Seed trichomes with secondary annular thickenings. L–Q. R. brevicaulis (STM on L–M, SEM on N–Q): L. Fruit. M–N. Seed. O. Seed apex. P. Seed base. Q. Seed trichomes with secondary annular thickenings. R–T. R. elegans (STM on R–S, SEM on T): R. Fruit. S–T. Seed. [STM=stereomicroscopy; SEM=scanning electron microscopy].
SFig.9.tif
Supplemental Figure 10
Fruits and seeds of Ruellia species from the clade “R. inflata”. A–D. R. elegans (SEM): A. Seed apex. B. Seed base. C. Seed trichomes with secondary annular thickenings. D. Hilar cells, some partially differentiated into trichomes. E–J. R. exserta (STM on E–F, SEM on G–J): E. Fruit. F–G. Seed. H. Seed apex. I. Seed base. J. Seed trichomes with secondary thickenings. K–Q. R. inflata (STM on K–L, SEM on M–Q): K. Fruit. L–M. Seed. N. Seed apex. O. Seed base. P. Seed trichomes with secondary annular thickenings. Q. Hilar cells, some partially differentiated into trichomes. R–T. R. subsessilis (STM on R–S, SEM on T): R. Fruit. S–T. Seed. [STM=stereomicroscopy; SEM=scanning electron microscopy].
SFig.10.tif
Supplemental Figure 11
Fruits and seeds of Ruellia species from the clades “R. inflata” (A–Q) and “R. humilis” (R–T). A–C. R. subsessilis (SEM): A. Seed apex. B. Seed base. C. Seed trichomes with secondary annular thickenings. D–J. Ruellia sp. 2 (STM on D–E, SEM on F–J): D. Fruit. E–F. Seed. G. Seed apex. H. Seed base. I. Seed trichomes with secondary thickenings. J. Hilar cells, some partially differentiated into trichomes. K–Q. Ruellia sp. 3 (STM on K–L, SEM on M–Q): K. Fruit. L–M. Seed. N. Seed apex. O. Seed base. P. Seed trichomes with secondary annular thickenings. Q. Hilar cells, some partially differentiated into trichomes. R–T. R. humilis (STM on R–S, SEM on T): R. Fruit. S–T. Seed. [STM=stereomicroscopy; SEM=scanning electron microscopy].
SFig.11.tif
Supplemental Figure 12
Fruits and seeds of Ruellia species from the clades “R. humilis” (A–C) and “Euruellia” s. s. (D–T). A–C. R. humilis (SEM): A. Seed apex. B. Seed base. C. Seed trichomes with secondary annular thickenings. D–I. R. hygrophila. (STM on D–E, SEM on F–I): D. Fruit. E–F. Seed. G. Seed apex. H. Seed base. I. Seed trichomes with secondary annular thickenings. J–O. R. macrosolen (STM on J–K, SEM on L–O): J. Fruit. K–L. Seed. M. Seed apex. N. Seed base. O. Seed trichomes with secondary annular thickenings. P–T. R. morongii (STM on P–Q, SEM on R–T): P. Fruit. Q–R. Seed. S. Seed apex. T. Seed base. [STM=stereomicroscopy; SEM=scanning electron microscopy].
SFig.12.tif
Supplemental Figure 13
Fruits and seeds of Ruellia species from the clades “Euruellia” s. s. (A–R) and “R. devosiana” (S–T). A. R. morongii (SEM): A. Seed trichomes with secondary annular thickenings. B–F. R. nudiflora (STM on B–C, SEM on D–F): B. Fruit. C–D. Seed. E. Seed base. F. Seed trichomes with secondary annular thickenings. G–M. R. tuberosa (STM on G–H, SEM on I–M): G. Fruit. H–I. Seed. J. Seed apex. K. Seed base. L. Seed trichomes with secondary annular thickenings. M. Hilar cells, some partially differentiated into trichomes. N–R. Ruellia sp. 1 (STM on N–O, SEM on P–R): N. Fruit. O–P. Seed. Q. Seed base. R. Seed trichomes with secondary annular thickenings. S–T. R. affinis (STM): S. Fruit. T. Seed. [STM=stereomicroscopy; SEM=scanning electron microscopy].
SFig.13.tif
Supplemental Figure 14
Fruits and seeds of Ruellia species from the clades “R. devosiana” (A–K) and “R. inundata” (L–T). A–D. R. affinis (SEM): A. Seed. B. Seed apex. C. Seed base. D. Seed trichomes with secondary annular thickenings and hilar cells. E–K. R. makoyana (STM on E–F, SEM on G–K): E. Fruit. F–G. Seed. H. Seed apex. I. Seed base. J. Seed trichomes with secondary annular thickenings. K. Mid-surface of the seed coat, lacking trichomes. L–R. R. asperula (STM on L–M, SEM on N–R): L. Fruit. M–N. Seed. O. Seed apex. P. Seed base. Q. Seed trichomes with secondary annular thickenings. R. Mid-surface of the seed coat, lacking trichomes. S–T. R. cearensis (STM): S. Fruit. T. Seed. [STM=stereomicroscopy; SEM=scanning electron microscopy].
SFig.14.tif
Supplemental Figure 15
Fruits and seeds of Ruellia species from the clade “R. inundata”. A–E. R. cearensis (SEM): A. Seed. B. Seed apex. C. Seed base. D. Seed trichomes with secondary annular thickenings. E. Mid-surface of the seed coat, lacking trichomes. F–L. R. ochroleuca (STM on F–G, SEM on H–L): F. Fruit. G–H. Seed. I. Seed apex. J. Seed base. K. Seed trichomes with secondary annular thickenings. L. Mid-surface of the seed coat, lacking trichomes. M–S. R. paniculata (STM on M–N, SEM on O–S): M. Fruit. N–O. Seed. P. Seed apex. Q. Seed base. R. Seed trichomes with secondary annular thickenings. S. Mid-surface of the seed coat, lacking trichomes. T. R. viscidula (STM): Fruit. [STM=stereomicroscopy; SEM=scanning electron microscopy].
SFig.15.tif
Supplemental Figure 16
Fruits and seeds of Ruellia species from the clades “R. inundata” (A–F) and “Physiruellia” (G–T). A–F. R. viscidula (STM on A, SEM on B–F): A–B. Seed. C Seed apex. D. Seed base. E. Seed trichomes with secondary annular thickenings. F. Mid-surface of the seed coat, lacking trichomes. G–M. R. amplexicaulis (STM on G–H, SEM on I–M): G. Fruit. H–I. Seed. J. Seed apex. K. Seed base. L. Seed trichomes with secondary annular thickenings. M. Mid-surface of the seed coat, lacking trichomes. N–T. R. angustiflora (STM on N–O, SEM on P–T): N. Fruit. O–P. Seed. Q. Seed apex. R. Seed base. S. Seed trichomes with secondary annular thickenings. T. Mid-surface of the seed coat, lacking trichomes. [STM=stereomicroscopy; SEM=scanning electron microscopy].
SFig.16.tif
Supplemental Figure 17
Fruits and seeds of Ruellia species from the clade “Physiruellia”. A–F. R. costata (STM on A–B, SEM on C–F): A. Fruit. B–C. Seed. D. Seed apex. E. Seed trichomes with secondary annular thickenings. F. Mid-surface of the seed coat, lacking trichomes. G–M. R. epallocaulos. (STM on G–H, SEM on I–M): G. Fruit. H–I. Seed. J. Seed apex. K. Seed base. L. Seed trichomes with secondary annular thickenings. M. Mid-surface of the seed coat, lacking trichomes. N–T. R. haenkeana (STM on N–O, SEM on P–T): N. Fruit. O–P. Seed. Q. Seed apex. R. Seed base. S. Seed trichomes with secondary annular thickenings. T. Mid-surface of the seed coat, lacking trichomes. [STM=stereomicroscopy; SEM=scanning electron microscopy].
SFig.17.tif
Supplemental Figure 18
Fruits and seeds of Ruellia from the clade “Physiruellia”. A–F. R. jussieuoides (STM on A–B, SEM on C–F): A. Fruit. B–C. Seed. D. Seed apex. E. Seed trichomes with secondary annular thickenings. F. Mid-surface of the seed coat, lacking trichomes. G–M. R. menthoides (STM on G–H, SEM on I–M): G. Fruit. H–I. Seed. J. Seed apex. K. Seed base. L. Seed trichomes with secondary annular thickenings. M. Mid-surface of the seed coat, lacking trichomes. N–T. R. nitida (STM on N–O, SEM on P–T): N. Fruit. O–P. Seed. Q. Seed apex. R. Seed base. S. Seed trichomes with secondary annular thickenings. T. Mid-surface of the seed coat, lacking trichomes. [STM=stereomicroscopy; SEM=scanning electron microscopy].
SFig.18.tif
Supplemental Figure 19
Fruits and seeds of Ruellia from the clade “Physiruellia”. A–G. R. proxima (STM on A–B, SEM on C–G): A. Fruit. B–C. Seed. D. Seed apex. E. Seed base. F. Seed trichomes with secondary annular thickenings. G. Mid-surface of the seed coat, lacking trichomes. H–N. R. rubra (STM on H–I, SEM on J–N): H. Fruit. I–J. Seed. K. Seed apex. L. Seed base. M. Seed trichomes with secondary annular thickenings. N. Mid-surface of the seed coat, lacking trichomes. O–T. R. terminalis (STM on O–P, SEM on Q–T): O. Fruit. P–Q. Seed. R. Seed apex. S. Seed base. T. Seed trichomes with secondary annular thickenings. [STM=stereomicroscopy; SEM=scanning electron microscopy].
SFig.19.tif
Supplemental Figure 20
Fruits and seeds of Ruellia species from the clades “Physiruellia” (A) and “Blechum” (B–T). A. R. terminalis (SEM): Mid-surface of the seed coat, lacking trichomes. B–I. R. anamariae (STM on B–C, SEM on D–H): B. Fruit. C–D. Seed. E. Seed apex. F. Seed base. G. Seed trichomes with secondary annular thickenings. H. Mid-surface of the seed coat, lacking trichomes. I–O. R. blechum (STM on I–J, SEM on K–O): I. Fruit. J–K. Seed. L. Seed apex. M. Seed base. N. Seed trichomes lageniform, lacking secondary annular thickenings. O. Wart on the mid-surface of the seed coat. P–T. R. macrantha (STM on P–Q, SEM on R–T): P. Fruit. Q–R. Seed. S. Seed apex. T. Seed base. [STM=stereomicroscopy; SEM=scanning electron microscopy].
SFig.20.tif
Supplemental Figure 21
Fruits and seeds of Ruellia species from the clade “Blechum” (A–I) and of species from the external groups Brillantaisia (J–O) and Strobilanthes (P–T). A–B. R. macrantha (SEM): A. Seed trichomes with secondary annular thickenings. B. Mid-surface of the seed coat, lacking trichomes. C–I. Ruellia neesiana (STM on C–D, SEM on E–I): C. Fruit. D–E. Seed. F. Seed apex. G. Seed base. H. Seed trichomes with secondary annular thickenings. I. Mid-surface of the seed coat, lacking trichomes. J–O. B. lamium (STM on J–K, SEM on L–O): J. Fruit. K–L. Seed. M. Seed apex. N. Seed base. O. Seed trichomes with secondary annular thickenings. P–T. S. dyeriana (STM on P–Q, SEM on R–T): P. Fruit. Q–R. Seed. S. Seed apex. T. Seed base. [STM=stereomicroscopy; SEM=scanning electron microscopy].
SFig.21.tif
Supplemental Figure 22
Fruits and seeds of species from the external groups Strobilanthes (A–B), Barleria (C–I), Lepidagathis (J–O) and Odontonema (P–T). A–B. S. dyeriana (SEM): Seed trichomes with secondary annular thickenings. C–I. B. cristata (STM on C–D, SEM on E–I): C. Fruit. D–E. Seed. F. Seed apex. G. Seed base. H–I. Seed trichomes, lacking secondary thickenings. J–O. L. sessilifolia (STM on J–K, SEM on L–O): J. Fruit. K–L. Seed. M. Seed apex. N. Seed base. O. Seed trichomes, lacking secondary thickenings. P–T. O. barlerioides (STM on P–Q, SEM on R–T): P. Fruit. Q–R. Seed. S–T. Glabrous and rugulate seed coat surface. [STM=stereomicroscopy; SEM=scanning electron microscopy].
SFig.22.tif
Table 1
Fruit and seed morphological characters of the species studied. The species of Ruellia with the symbol “(N)” are those for which infrageneric placements are suggested here, based on the morphological patterns observed.
Table1.pdf
Table 2
Morphology of the seed trichomes of the species studied. The species of Ruellia with the symbol “(N)” are those whose infrageneric placement is suggested here, based on the morphological patterns observed.
Table2.pdf
Table 3
Morphological characters of the cells of the mid-region of the seed coat of the species studied that show at least part of the seed coat not covered by trichomes. The terminology follows Barthlott (1981).
Table3.pdf
Table4
Diameter measurements of the species studied (n = 10), where x ̅ ±s_x ̅ = average ± average standard deviation; C.I. = confidence interval. The following symbols indicate: “*” n < 10; “**” n < 5; “***” n = 1.
