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Text-fig. 27. Scanning electron microscope (SEM) images of stamens and pollen of Valvidistemon globiferus gen. et sp. nov.; Catefica locality, Portugal. a) Stamen in oblique lateral view showing laterally hinged valves, massive connective between the thecae and prominent, globular, apical extension of the connective; b) Stamen in oblique lateral view on the opposite side from (a) showing broken laterally hinged valves and distinct endothecium cells; c) Detail of stamen showing the large, longitudinally aligned cells of the massive connective, broad, poorly defined stamen base, and the laterally hinged valves of one of the thecae; d) Reticulate pollen attached to the inside of the anther wall. Specimen, Catefica 49-S107779 (holotype, a–d). Scale bars = 600 Μm (a, b), 100 Μm (c), 20 Μm (d). in The Early Cretaceous Mesofossil Flora Of Catefica, Portugal: Angiosperms
Text-fig. 27. Scanning electron microscope (SEM) images of stamens and pollen of Valvidistemon globiferus gen. et sp. nov.; Catefica locality, Portugal. a) Stamen in oblique lateral view showing laterally hinged valves, massive connective between the thecae and prominent, globular, apical extension of the connective; b) Stamen in oblique lateral view on the opposite side from (a) showing broken laterally hinged valves and distinct endothecium cells; c) Detail of stamen showing the large, longitudinally aligned cells of the massive connective, broad, poorly defined stamen base, and the laterally hinged valves of one of the thecae; d) Reticulate pollen attached to the inside of the anther wall. Specimen, Catefica 49-S107779 (holotype, a–d). Scale bars = 600 Μm (a, b), 100 Μm (c), 20 Μm (d).
Text-fig. 26. Scanning electron microscope (SEM) images of stamens and pollen grains of Elasmostemon paisii gen. et sp. nov. (a–c) and laminar stamens with monocolpate reticulate pollen sp. (d–g); Catefica locality, Portugal. a) Stamen fragment with basal portion missing showing two pairs of pollen sacs on one surface of the stamen close to the margin and separated by a broad connective, except near the apex where the thecae meet; note that the thecae are dehisced with the walls of the pollen sacs curled back; b) Pollen grains inside a dehisced pollen sac; note variation in size and development of the reticulum; c) Detail of (b) showing monocolpate, reticulate pollen with lumen of reticulum varying markedly in size but partly obscured by residual organic material; d) Stamen with apical and basal part of anther preserved showing two pairs of pollen sacs (asterisks) on the curved, perhaps ventral, surface close to the stamen margin; e) Detail of crack in the anther showing the inner anther wall with densely spaced spherical orbicules that vary greatly in size; f) Pollen exposed in the crack in the anther; note coarsely foveolate to coarsely reticulate pollen wall and densely spaced orbicules; g) Folded pollen grains with reticulate pollen wall and also showing the inner anther wall with densely spaced spherical orbicules that vary greatly in size. Specimens, Catefica 49-S172560 (a–c), Catefica 50- S170384 (d–g). Scale bars = 600 Μm (a, d), 20 Μm (b, e), 6 Μm (c, f, g). in The Early Cretaceous Mesofossil Flora Of Catefica, Portugal: Angiosperms
Text-fig. 26. Scanning electron microscope (SEM) images of stamens and pollen grains of Elasmostemon paisii gen. et sp. nov. (a–c) and laminar stamens with monocolpate reticulate pollen sp. (d–g); Catefica locality, Portugal. a) Stamen fragment with basal portion missing showing two pairs of pollen sacs on one surface of the stamen close to the margin and separated by a broad connective, except near the apex where the thecae meet; note that the thecae are dehisced with the walls of the pollen sacs curled back; b) Pollen grains inside a dehisced pollen sac; note variation in size and development of the reticulum; c) Detail of (b) showing monocolpate, reticulate pollen with lumen of reticulum varying markedly in size but partly obscured by residual organic material; d) Stamen with apical and basal part of anther preserved showing two pairs of pollen sacs (asterisks) on the curved, perhaps ventral, surface close to the stamen margin; e) Detail of crack in the anther showing the inner anther wall with densely spaced spherical orbicules that vary greatly in size; f) Pollen exposed in the crack in the anther; note coarsely foveolate to coarsely reticulate pollen wall and densely spaced orbicules; g) Folded pollen grains with reticulate pollen wall and also showing the inner anther wall with densely spaced spherical orbicules that vary greatly in size. Specimens, Catefica 49-S172560 (a–c), Catefica 50- S170384 (d–g). Scale bars = 600 Μm (a, d), 20 Μm (b, e), 6 Μm (c, f, g).
Text-fig. 30. Scanning electron microscope (SEM) images of anther and pollen of Kempia longicolpites; Catefica locality, Portugal. a) Transverse section through an anther showing the four pollen sacs with in situ pollen; b) Pollen in situ from anther in (a) showing very long colpus and loosely attached reticulum; c) Detail of reticulum showing smooth muri supported by short, scattered columellae; d) Pollen grain from anther in (a) enlarged showing colpus extended beyond the equator and loosely attached reticulum; e) Detail of pollen wall showing thick, homogeneous foot layer, columellae and reticulate tectum; note remains of granular endexine (arrows) in the apertural region of the grain; f) Internal view of reticulum showing the short columellae adhering to the muri detached from the foot layer. Specimen, Catefica 49-S101208 (a–f). Scale bars = 100 Μm (a), 20 Μm (b), 6 Μm (d), 3 Μm (c, e, f). in The Early Cretaceous Mesofossil Flora Of Catefica, Portugal: Angiosperms
Text-fig. 30. Scanning electron microscope (SEM) images of anther and pollen of Kempia longicolpites; Catefica locality, Portugal. a) Transverse section through an anther showing the four pollen sacs with in situ pollen; b) Pollen in situ from anther in (a) showing very long colpus and loosely attached reticulum; c) Detail of reticulum showing smooth muri supported by short, scattered columellae; d) Pollen grain from anther in (a) enlarged showing colpus extended beyond the equator and loosely attached reticulum; e) Detail of pollen wall showing thick, homogeneous foot layer, columellae and reticulate tectum; note remains of granular endexine (arrows) in the apertural region of the grain; f) Internal view of reticulum showing the short columellae adhering to the muri detached from the foot layer. Specimen, Catefica 49-S101208 (a–f). Scale bars = 100 Μm (a), 20 Μm (b), 6 Μm (d), 3 Μm (c, e, f).
Text-fig. 10. Scanning electron microscope (SEM) images of isolated "Stamen fragment with Clavatipollenites-type pollen sp. 1"; Catefica locality, Portugal. a) Fragment of tetrasporangiate stamen with pollen in situ; b) Detail from stamen fragment showing distal and proximal surfaces of in situ pollen grains and tiny orbicules on the inner surface of the anther wall (arrows); c) Pollen grains in distal view showing short colpi with irregular margins and aperture membrane with irregular verrucae; d) Detail of pollen wall showing the semitectate-reticulate tectum and long, scattered columellae supporting the narrow muri with finely verrucate supratectal ornamentation. Specimen, Catefica 50-S170387 (a–d). Scale bars = 600 Μm (a), 20 Μm (b), 6 Μm (c), 1.5 Μm (d). in The Early Cretaceous Mesofossil Flora Of Catefica, Portugal: Angiosperms
Text-fig. 10. Scanning electron microscope (SEM) images of isolated "Stamen fragment with Clavatipollenites-type pollen sp. 1"; Catefica locality, Portugal. a) Fragment of tetrasporangiate stamen with pollen in situ; b) Detail from stamen fragment showing distal and proximal surfaces of in situ pollen grains and tiny orbicules on the inner surface of the anther wall (arrows); c) Pollen grains in distal view showing short colpi with irregular margins and aperture membrane with irregular verrucae; d) Detail of pollen wall showing the semitectate-reticulate tectum and long, scattered columellae supporting the narrow muri with finely verrucate supratectal ornamentation. Specimen, Catefica 50-S170387 (a–d). Scale bars = 600 Μm (a), 20 Μm (b), 6 Μm (c), 1.5 Μm (d).
Text-fig. 20. Synchrotron radiation X-ray tomographic microscopy (SRXTM, a) and scanning electron microscope (SEM, b–h) images of fruits of Appomattoxia sp. (a–d) and anther and pollen of Goczania rugosa (e–h); Catefica locality, Portugal. a) Surface rendering of fruit in lateral view showing densely spaced hairs, some with delicate coiled tips; b) Fruit in lateral view showing short, densely spaced hairs and apical stigmatic region; c, d) Detail of fruit surface and hairs from fruit in (b); e) Fragmentary anther showing four pollen sacs; f) Proximal view of pollen grains from an abraded anther showing microechinate surface of pollen wall and clusters of small, spiny orbicules; g, h) Proximal (g) and distal (h) views of pollen grains from an isolated pollen sac, showing short colpus (h), tectate pollen wall and microechinate surface ornamentation. Specimens, Catefica 49-S174913 (a), Catefica 49-S107794 (b–d), Catefica 50-S170391 (e), Catefica 49-S170138 (f), Catefica 49-S170143 (g, h). Scale bars = 300 Μm (a, b, e), 100 Μm (c), 50 Μm (d), 6 Μm (f–h). in The Early Cretaceous Mesofossil Flora Of Catefica, Portugal: Angiosperms
Text-fig. 20. Synchrotron radiation X-ray tomographic microscopy (SRXTM, a) and scanning electron microscope (SEM, b–h) images of fruits of Appomattoxia sp. (a–d) and anther and pollen of Goczania rugosa (e–h); Catefica locality, Portugal. a) Surface rendering of fruit in lateral view showing densely spaced hairs, some with delicate coiled tips; b) Fruit in lateral view showing short, densely spaced hairs and apical stigmatic region; c, d) Detail of fruit surface and hairs from fruit in (b); e) Fragmentary anther showing four pollen sacs; f) Proximal view of pollen grains from an abraded anther showing microechinate surface of pollen wall and clusters of small, spiny orbicules; g, h) Proximal (g) and distal (h) views of pollen grains from an isolated pollen sac, showing short colpus (h), tectate pollen wall and microechinate surface ornamentation. Specimens, Catefica 49-S174913 (a), Catefica 49-S107794 (b–d), Catefica 50-S170391 (e), Catefica 49-S170138 (f), Catefica 49-S170143 (g, h). Scale bars = 300 Μm (a, b, e), 100 Μm (c), 50 Μm (d), 6 Μm (f–h).
Text-fig. 24. Scanning electron microscope (SEM) images of "Stamen with zona-aperturate pollen"; Catefica locality, Portugal. a) Dorsal view of elongated anther showing the broad connective and very narrow pollen sacs; b) Lateral view of elongated anther showing the broad dorsal and ventral surfaces of the connectives and very narrow pollen sacs; c) Apex of elongated anther showing dorsal and ventral surfaces and very narrow pollen sacs; d) Lateral view of narrow pollen sac showing in situ pollen; e) Detail of pollen grain showing the solid band of exine above the aperture (asterisk); f) Detail of pollen grain showing the solid band of exine above the aperture (asterisk); g) Detail of tectum showing heterobrochate reticulum with lumina of two different sizes supported by long columellae (arrows); h) Detail of pollen grain showing the aperture extending over the ends of the grain (asterisks); i) Detail of tectum showing heterobrochate reticulum with lumina of two different sizes supported by long columellae (arrows). Specimen, Catefica 49-S171527 (a–i). Scale bars = 600 Μm (a, b), 100 Μm (c), 20 Μm (d), 6 Μm (e, f, h), 3 Μm (g), 1.5 Μm (i). in The Early Cretaceous Mesofossil Flora Of Catefica, Portugal: Angiosperms
Text-fig. 24. Scanning electron microscope (SEM) images of "Stamen with zona-aperturate pollen"; Catefica locality, Portugal. a) Dorsal view of elongated anther showing the broad connective and very narrow pollen sacs; b) Lateral view of elongated anther showing the broad dorsal and ventral surfaces of the connectives and very narrow pollen sacs; c) Apex of elongated anther showing dorsal and ventral surfaces and very narrow pollen sacs; d) Lateral view of narrow pollen sac showing in situ pollen; e) Detail of pollen grain showing the solid band of exine above the aperture (asterisk); f) Detail of pollen grain showing the solid band of exine above the aperture (asterisk); g) Detail of tectum showing heterobrochate reticulum with lumina of two different sizes supported by long columellae (arrows); h) Detail of pollen grain showing the aperture extending over the ends of the grain (asterisks); i) Detail of tectum showing heterobrochate reticulum with lumina of two different sizes supported by long columellae (arrows). Specimen, Catefica 49-S171527 (a–i). Scale bars = 600 Μm (a, b), 100 Μm (c), 20 Μm (d), 6 Μm (e, f, h), 3 Μm (g), 1.5 Μm (i).
Text-fig. 29. Scanning electron microscope (SEM) images of stamens and pollen grains of cf. Endressistemon sp. 1 (a, b), cf. Endressistemon sp. 2 (c, d) and cf. Endressistemon sp. 3 (e–g); Catefica locality, Portugal. a) Two adhering stamens, each with a long, pointed extension of the connective; b) Monocolpate, reticulate pollen in situ in stamen from stamen pair in (a); c) Fragment of stamen with prominent apical extension of the connective; d) Reticulate, apparently monocolpate, pollen in situ in stamen fragment in (c); e) Stamen with basifixed anther, perhaps sessile, and with prominent, wing-like apical extensions of the connective; note the dehisced thecae with the anther wall curved back; f, g) Monocolpate, reticulate pollen in situ in stamen in (e). Specimens, Catefica 49-S107780 (a, b), Catefica 49-S107784 (c, d), Catefica 49-S107781 (e–g). Scale bars = 600 Μm (a, c, e), 6 Μm (b, d, f, g). in The Early Cretaceous Mesofossil Flora Of Catefica, Portugal: Angiosperms
Text-fig. 29. Scanning electron microscope (SEM) images of stamens and pollen grains of cf. Endressistemon sp. 1 (a, b), cf. Endressistemon sp. 2 (c, d) and cf. Endressistemon sp. 3 (e–g); Catefica locality, Portugal. a) Two adhering stamens, each with a long, pointed extension of the connective; b) Monocolpate, reticulate pollen in situ in stamen from stamen pair in (a); c) Fragment of stamen with prominent apical extension of the connective; d) Reticulate, apparently monocolpate, pollen in situ in stamen fragment in (c); e) Stamen with basifixed anther, perhaps sessile, and with prominent, wing-like apical extensions of the connective; note the dehisced thecae with the anther wall curved back; f, g) Monocolpate, reticulate pollen in situ in stamen in (e). Specimens, Catefica 49-S107780 (a, b), Catefica 49-S107784 (c, d), Catefica 49-S107781 (e–g). Scale bars = 600 Μm (a, c, e), 6 Μm (b, d, f, g).
Text-fig. 28. Scanning electron microscope (SEM) images of stamens and pollen of Endressistemon cateficensis gen. et sp. nov.; Catefica locality, Portugal. a, b) Staminal structure with two lateral stamens and one median structure seen in ventral and dorsal view (orientation unknown) showing that each stamen has a prominent apical extension and two pairs of pollen sacs separated by a narrow connective; both stamens are borne on a common base together with the median structure and their anthers are sessile on the common stalk; note the apical projection of the median structure (asterisk) between the two stamens and the ribs over probable vascular bundles that extend from the common base into the apical projections of both stamens and the median structure (arrows); c) Staminal structure showing two stamens with prominent apical projections and median axis-like structure between the two stamens (arrow); d) Staminal structure showing two stamens with prominent apical projections borne on a common base; e) Staminal structure in (a) and (b), from the same orientation as (b), showing the ribs over probable vascular bundles (yellow) that extend into the apical projections; f) Detail of staminal structure in (a) and (b) showing the fused or strongly adhering apical projections of the two lateral stamens and the median structure (asterisk); g) Monocolpate, reticulate pollen grains from the pollen sacs of stamen in (d). Specimens, Catefica 49-S107778 (holotype, a, b, e, f), Catefica 49-S107769 (c), Catefica 49-S107751 (d, g). Scale bars = 600 Μm (a–d), 300 Μm (e), 100 Μm (f), 6 Μm (g). in The Early Cretaceous Mesofossil Flora Of Catefica, Portugal: Angiosperms
Text-fig. 28. Scanning electron microscope (SEM) images of stamens and pollen of Endressistemon cateficensis gen. et sp. nov.; Catefica locality, Portugal. a, b) Staminal structure with two lateral stamens and one median structure seen in ventral and dorsal view (orientation unknown) showing that each stamen has a prominent apical extension and two pairs of pollen sacs separated by a narrow connective; both stamens are borne on a common base together with the median structure and their anthers are sessile on the common stalk; note the apical projection of the median structure (asterisk) between the two stamens and the ribs over probable vascular bundles that extend from the common base into the apical projections of both stamens and the median structure (arrows); c) Staminal structure showing two stamens with prominent apical projections and median axis-like structure between the two stamens (arrow); d) Staminal structure showing two stamens with prominent apical projections borne on a common base; e) Staminal structure in (a) and (b), from the same orientation as (b), showing the ribs over probable vascular bundles (yellow) that extend into the apical projections; f) Detail of staminal structure in (a) and (b) showing the fused or strongly adhering apical projections of the two lateral stamens and the median structure (asterisk); g) Monocolpate, reticulate pollen grains from the pollen sacs of stamen in (d). Specimens, Catefica 49-S107778 (holotype, a, b, e, f), Catefica 49-S107769 (c), Catefica 49-S107751 (d, g). Scale bars = 600 Μm (a–d), 300 Μm (e), 100 Μm (f), 6 Μm (g).
Text-fig. 8. Scanning electron microscope (SEM) images of staminate inflorescences and pollen of Proencistemon portugallicus gen. et sp. nov.; Catefica locality, Portugal. a, b) Staminate inflorescences composed of numerous tetrasporangiate stamens; each stamen lacks a filament and there is no clear indication of other floral organs; note apparently paired arrangement of stamens in (b) (asterisks); c) Pollen in situ in anther from specimen in (a) showing poorly defined trichotomocolpate aperture and semitectate-reticulate tectum; d) Detail of pollen from specimen in (a) showing narrow muri with beaded surface ornamentation; e) Distal and proximal views of pollen in situ in an anther fragment; f) Orbicules attached to surface of in situ pollen from anther fragment. Specimens, Catefica M282-P0341 (holotype, a, c, d), Catefica 150-S174257 (b), Catefica 50-S170393 (e, f). Scale bars = 600 Μm (a, b), 6 Μm (c, e), 1.5 Μm (d, f). in The Early Cretaceous Mesofossil Flora Of Catefica, Portugal: Angiosperms
Text-fig. 8. Scanning electron microscope (SEM) images of staminate inflorescences and pollen of Proencistemon portugallicus gen. et sp. nov.; Catefica locality, Portugal. a, b) Staminate inflorescences composed of numerous tetrasporangiate stamens; each stamen lacks a filament and there is no clear indication of other floral organs; note apparently paired arrangement of stamens in (b) (asterisks); c) Pollen in situ in anther from specimen in (a) showing poorly defined trichotomocolpate aperture and semitectate-reticulate tectum; d) Detail of pollen from specimen in (a) showing narrow muri with beaded surface ornamentation; e) Distal and proximal views of pollen in situ in an anther fragment; f) Orbicules attached to surface of in situ pollen from anther fragment. Specimens, Catefica M282-P0341 (holotype, a, c, d), Catefica 150-S174257 (b), Catefica 50-S170393 (e, f). Scale bars = 600 Μm (a, b), 6 Μm (c, e), 1.5 Μm (d, f).
Text-fig. 9. Scanning electron microscope (SEM) images of stamens and pollen of Proencistemon portugallicus gen. et sp. nov. (a–g) and Proencistemon sp. (h–j); Catefica locality, Portugal. a) Fragment of stamen whorl from staminate inflorescence showing almost sessile anthers; note short bracts at the base of the stamen whorl (arrow) and apparent paired arrangement of the stamens; b) Fragment of stamen whorl showing almost sessile anthers and apparent paired arrangement of the stamens; c) Pollen in situ from stamen whorl in (b) showing poorly defined trichotomocolpate aperture and semitectate-reticulate tectum; d–g) Distal views of pollen in situ from pollen clump showing poorly defined trichotomocolpate aperture, semitectate-reticulate tectum (d–f), and fractured pollen wall with long, scattered columellae supporting narrow muri (g); h) Fragment of staminate inflorescence with narrow, almost sessile, stamens; i, j) Pollen from fragment of staminate inflorescence in (h) showing poorly defined trichotomocolpate aperture (i), semitectate-reticulate tectum (i, j) and long, scattered columellae supporting narrow muri (j). Specimens, Catefica 49-S266015 (a), Catefica 342-S122086 (b, c), Catefica 50-S170394 (d–g), Catefica 49-S107783 (h–j). Scale bars = 600 Μm (a, b, h), 6 Μm (c–f, i), 1.5 Μm (g, j). in The Early Cretaceous Mesofossil Flora Of Catefica, Portugal: Angiosperms
Text-fig. 9. Scanning electron microscope (SEM) images of stamens and pollen of Proencistemon portugallicus gen. et sp. nov. (a–g) and Proencistemon sp. (h–j); Catefica locality, Portugal. a) Fragment of stamen whorl from staminate inflorescence showing almost sessile anthers; note short bracts at the base of the stamen whorl (arrow) and apparent paired arrangement of the stamens; b) Fragment of stamen whorl showing almost sessile anthers and apparent paired arrangement of the stamens; c) Pollen in situ from stamen whorl in (b) showing poorly defined trichotomocolpate aperture and semitectate-reticulate tectum; d–g) Distal views of pollen in situ from pollen clump showing poorly defined trichotomocolpate aperture, semitectate-reticulate tectum (d–f), and fractured pollen wall with long, scattered columellae supporting narrow muri (g); h) Fragment of staminate inflorescence with narrow, almost sessile, stamens; i, j) Pollen from fragment of staminate inflorescence in (h) showing poorly defined trichotomocolpate aperture (i), semitectate-reticulate tectum (i, j) and long, scattered columellae supporting narrow muri (j). Specimens, Catefica 49-S266015 (a), Catefica 342-S122086 (b, c), Catefica 50-S170394 (d–g), Catefica 49-S107783 (h–j). Scale bars = 600 Μm (a, b, h), 6 Μm (c–f, i), 1.5 Μm (g, j).
Darwin's vexing contrivance: A new hypothesis for why some flowers have two kinds of anther
<p>Heteranthery, the presence of two or more anther types in the same flower, is taxonomically widespread among bee-pollinated angiosperms, yet has puzzled botanists since Darwin. We test two competing hypotheses for its evolution: the longstanding "division of labour" hypothesis, which posits that some anthers are specialized as food rewards for bees whereas other are specialized for surreptitious pollination, and our new hypothesis that heteranthery is a way to gradually release pollen that maximizes pollen delivery. We examine the evolution of heteranthery and associated traits across the genus <i>Clarkia </i>(Onagraceae) and study plant-pollinator interactions in two heterantherous <i>Clarkia </i>species. Across species, heteranthery is associated with bee pollination, delayed dehiscence and colour crypsis of one anther whorl, and movement of that anther whorl upon dehiscence. Our mechanistic studies in heterantherous species show that bees notice, forage on, and export pollen from each anther whorl when it is dehiscing, and that heteranthery promotes pollen export. We find no support for division of labour, but multifarious evidence that heteranthery is a mechanism for gradual pollen presentation that likely evolved through indirect male-male competition for siring success.</p>
Data from: Transmission and temporal dynamics of anther-smut disease (Microbotryum) on alpine carnation (Dianthus pavonius)
1. Theory has shown that sterilizing diseases with frequency-dependent transmission (characteristics shared by many sexually transmitted diseases) can drive host populations to extinction. 2. Anther-smut disease (caused by Microbotryum sp.) has become a model plant pathogen system for studying the dynamics of vector and sexually transmitted diseases: infected individuals are sterilized, producing spores instead of pollen, and the disease is spread between reproductive individuals by insect pollinators. We investigated anther-smut disease in a heavily infected population of Dianthus pavonius (alpine carnation) over an eight-year period to determine disease impacts on host population dynamics. 3. Over the eight years, disease prevalence remained consistently high (>40%) while the host population numbers declined by over 50%. 4. The observed rate of vector transmission to reproductive, adult hosts was inadequate to explain the high disease prevalence. Additional density-dependent aerial transmission to highly susceptible juveniles, indicated from experimental field and greenhouse studies, is likely to play a key role in maintaining the high disease prevalence. 5. Epidemiological models that accounted for the mixed transmission mode predicted an eventual decline in disease. 6. Synthesis: Our results demonstrate that high prevalence of a sterilizing disease does not necessarily drive host populations towards extinction and also highlights the importance of demographic studies for establishing the presence of alternative transmission modes.
Data from: Is there a disease-free halo at species range limits? The co-distribution of anther-smut disease and its host species
1. While disease is widely recognized as affecting host population size, it has rarely been considered to play a role in determining host range limits. Many diseases may not be able to persist near the range limit if host population density falls below the critical threshold level for pathogen invasion. However, in vector- and sexually-transmitted diseases, pathogen transmission may be largely independent of host density and theory demonstrates that diseases with frequency-dependent transmission may persist in small populations near the range limit. 2. Empirical studies of disease at species range limits have lagged behind the theory, and to date, no previous study has tested the hypothesis that vector or sexually transmitted diseases can be maintained at host range limits. 3. We studied the distribution of anther-smut disease, a sterilizing pollinator-transmitted disease, on four alpine plant species to determine whether disease was present at the host range limits. 4. We found that host abundance declined towards the elevational range limits, and disease extended to the most extreme elevational range limits in three of the four host species. Maximum likelihood estimation of the magnitude of the disease-free halo showed that it was small or non-existent for all host species. Moreover, disease prevalence within populations was often higher nearer the host's range limit than in the range center and was independent of host density. 5. Synthesis: Our results show that diseases where transmission is frequency-dependent have the potential to affect host distributions not just in theory, but also in real world populations.
Anther cones increase pollen release in buzz-pollinated Solanum flowers
<p>The widespread evolution of tube-like anthers releasing pollen from apical pores is associated with buzz pollination, in which bees vibrate flowers to remove pollen. The mechanical connection among anthers in buzz-pollinated species varies from loosely held conformations, to anthers tightly held together with trichomes or bio-adhesives forming a functionally joined conical structure (anther cone). Joined anther cones in buzz-pollinated species have evolved independently across plant families and via different genetic mechanisms, yet their functional significance remains mostly untested. We used experimental manipulations to compare vibrational and functional (pollen release) consequences of joined anther cones in three buzz-pollinated species of Solanum (Solanaceae). We applied bee-like vibrations to focal anthers in flowers with ("joined") and without ("free") experimentally created joined anther cones, and characterised vibrations transmitted to other anthers and the amount of pollen released. We found that joined anther architectures cause non-focal anthers to vibrate at higher amplitudes than free architectures. Moreover, in the two species with naturally loosely held anthers, anther fusion increases pollen release, while in the species with a free but naturally compact architecture it does not. We discuss hypotheses for the adaptive significance of the convergent evolution of joined anther cones.</p>
Structural anther mimics improve reproductive success through dishonest signalling that enhances both attraction and the morphological fit of pollinators with flowers
<p><span>Numerous studies have identified traits associated with anther mimicry, however, the processes underlying floral deception remains poorly documented for these structures. We studied the importance of pollinator attraction and mechanical fit of anther mimics in <em>Tritonia laxifolia</em> (Iridaceae) and their relative contributions to reproductive success. To determine anther mimics role in pollinator attraction, we offered bees' binary choices to flowers painted with UV absorbent and reflecting paint. We also conducted preference experiments between flowers with excised anther mimics and unmanipulated controls, from which mechanical fit was assessed by allowing single visits. Anther mimics effects on female reproductive success was determined using similar treatments, but on rooted plants. Bees preferred UV absorbent over UV reflecting anther mimics. Bees did not discriminate between flowers with and without three-dimensional anther mimics. Single visits resulted in more pollen deposition on unmanipulated controls over flowers with their anther mimics excised, which was directly linked to pollen-collecting behaviour. Controls with unmanipulated anther mimics had higher seed set than those with their anther mimics excised. This study provides insights into pollinator-mediated selection on deceptive floral signals and shows that three-dimensional anther mimics increases reproductive success through both attraction and pollen-collecting behaviours.</span></p>
Weak response to selection on stigma-anther distance in a primarily selfing population of yellow monkeyflower
<p>Stebbins hypothesized that selfing lineages are evolutionary dead ends because they lack adaptive potential. While selfing populations often harbor limited nucleotide variability compared to closely related outcrossers, reductions in the genetic variability of quantitative characters remain unclear, especially for key traits determining selfing rates. Yellow monkeyflower (<em>Mimulus guttatus</em>) populations generally outcross and maintain extensive quantitative genetic variation in floral traits. Here, we study the Joy Road population (Bodega Bay, California, USA) of <em>M. guttatus</em>, where individuals exhibit stigma-anther distances typical of primarily selfing monkeyflowers. We show that this population is closely related to nearby conspecifics on the Pacific coast with a modest 33% reduction in genome-wide variation compared to a more highly outcrossing population. A five-generation artificial selection experiment challenged the hypothesis that the Joy Road population harbors comparatively low evolutionary potential in the stigma-anther distance, a critical determinant of selfing rate in <em>Mimulus</em>. Artificial selection generated a weak phenotypic response, with low realized heritabilities (0.020-0.028) falling 84% below those measured for floral characters in more highly outcrossing <em>M. guttatus</em>. These results demonstrate substantial declines in evolutionary potential with a transition toward selfing. Whether these findings explain infrequent reversals to outcrossing or general limits on adaptation in selfers requires further investigation.</p>
Data and models to accompany "Turgor pressure affects transverse stiffness and resonant frequencies of buzz-pollinated poricidal anthers"
<p>Data sets and models to accompany the paper "Turgor pressure affects transverse stiffness and resonant frequencies of buzz-pollinated poricidal anthers". </p>
Fig. 1 in Effectiveness Of Doubled Haploids Production By Anther Culture From Selected Winter Wheat Hybrids
Fig. 1. Efficiency of formation of embryos and plants-regenerants.
Data from: Repeated loss of function at HD mating-type genes and of recombination suppression without mating-type locus linkage in anther-smut fungi
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Data from: Effect of the anther-smut fungus Microbotryum on the juvenile growth of its host Silene latifolia
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Allen Brain Atlas
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Annotated Behaviour and Observability Dataset (ABODe)
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