Reproductive systems are fundamental attributes for understanding life cycle and regeneration processes and provide information about seed production and genetic diversity. Analyses of reproductive strategies within c...Reproductive systems are fundamental attributes for understanding life cycle and regeneration processes and provide information about seed production and genetic diversity. Analyses of reproductive strategies within communities and their associations with functional groups can indicate how physical and biological characteristics may influence the reproductive ecology of such communities. The main goal was to determine if the reproductive systems and their associated functional groups have particular characteristics related to extreme conditions and disturbance within xerophytic shrubland. Floral morphology analysis and four experimental tests were conducted to determine the reproductive systems of species and their associations with the life form, succulence, carbon metabolism, dispersal syndrome, pollination, and disturbance. Of the 144 plant species studied, 72.9% were hermaphrodite, 22.9% were monoecious, and 4.2% were dioecious. Dioecy was associated with woodiness, frugivory and undisturbed areas, while monoecy was more common in herbs. Adichogamy, protandry and herkogamy were more frequent than dichogamy, protogyny and no herkogamy, respectively. Xenogamous species tend to be woody and grow in undisturbed areas, while partially xenogamous species were mainly herbs occurring in disturbed areas. The majority of species were partially self-incompatible. High levels of outbreeding strategies tended to occur mainly in woody K-strategy species from undisturbed areas, mixed breeding strategies occurred in disturbed areas and overall community, and inbreeding strategies were associated with mostly herbaceous r-strategy primarily in disturbed areas.展开更多
Aims Distyly has been regarded as an adaptation to improve compatible pollination between two floral morphs with reciprocal herkogamy.The hypothesis that the different positions of anthers and stigmas within flowers a...Aims Distyly has been regarded as an adaptation to improve compatible pollination between two floral morphs with reciprocal herkogamy.The hypothesis that the different positions of anthers and stigmas within flowers as well as their reciprocal position between morphs,reduce the probability of self pollination raised by Darwin has been rarely tested.in this study,we measured stigmatic pollen loads in response to reduced reciprocal herkogamy in two Primula species.Methods To see whether reciprocal herkogamy can increase compatible and/or reduce incompatible pollen deposition,thus promoting compat-ible pollination,we shortened the distance between anthers and stigmas within the flowers by changing the position of the corolla tube,to which the anthers were fused,i.e.reduced herkogamy in natural populations of Primula secundiflora and P.poissonii and quantified stigmatic pollen loads in the field over 2 years.Important Findingsin both species,stigmatic pollen loads were significantly higher in the long-styled(l-morph)than in the short-styled morph(s-morph)in both control and manipulated flowers,but percentage of compatible pollen in s-morph were higher.Flowers manipulated to halve the anther-stigma distance showed a similar pattern for 2 years:total pollen grain counts on stigmas did not differ significantly but compatible pollen grains in l-and s-morphs were significantly decreased in both species.The percentage of compatible pollen loads was decreased by 68.7%in P.secundiflora and 65.3%in P.poissonii in l-morphs,while it decreased by 30.6%and 2.9%in s-morphs,respectively.our manipulation of the relative position of anthers and stigmas in the two distylous species indicated that a lower degree of herkogamy reduced compatible but incompatible pollen transfer was likely to increase.The higher proportion of compatible pollen in the s-morph than in the l-morph in the two Primula species could be attributed to the accessibility of two-level sexual organs,floral orientations and pollinator behaviors.This is a first attempt to manipulate intraflower herkogamy for understanding adaptation of heterostyly,shedding insights into how the reciprocal herkogamy promotes compatible pollination.展开更多
Aims Distyly is one of the most widespread floral polymorphisms pro-moting cross-fertilization.Evolutionary transition from obligate cross-fertilized distyly to predominantly self-fertilized homostyly is frequently do...Aims Distyly is one of the most widespread floral polymorphisms pro-moting cross-fertilization.Evolutionary transition from obligate cross-fertilized distyly to predominantly self-fertilized homostyly is frequently documented in various groups.However,empirical stud-ies concerning the ecological factors connected with this transition are still lacking.Primula chungensis,suggested to be evolving from distyly to homostyly,provides an ideal model for the study of the ecological factors concerned with this transition.We study P.chun-gensis to understand if autonomous self-fertilization would provide reproductive assurance for the self-fertilized homo-styled morph in the field.Methods the incompatibility features of P.chungensis were tested with hand-pollination experiments.We compared the capacity of autonomous self-fertilization between the distylous and homo-styled morph of P.chungensis in the field by excluding the pollinators with bags.In addition,the degrees of herkogamy of some P.chungensis plants were between the short-styled and homo-styled morphs.these plants were studied to understand whether they were able to obtain greater reproductive assurance when the herkogamy in the flowers was reduced.Important Findings All three morphs of P.chungensis were highly self-and intra-morph compatible.the degree of herkogamy positively correlated with the capacity for autonomous self-fertilization.A negative correlation between the degree of herkogamy and the magnitude of pollen limitation was found,but no significant correlation was found between the degree of herkogamy and the contribution of cross-fertilization to overall fertilization.this study suggests that reducing the degree of herkogamy can significantly increase the reproductive assurance for a self-compatible plant.Our results provided evidence that the homo-styled morph of P.chungensis had the highest capacity for autonomous self-fertilization and the highest seed production in the field,because autonomous self-fertilization provided reproduct-ive assurance for the homo-styled morph.this may cause selection towards the transition from distyly to homostyly.展开更多
Aims The evolution of the outstanding variation of reproductive systems in angiosperms has been considered an important driver of line-age diversification.Closely related hermaphroditic and dioecious species with biot...Aims The evolution of the outstanding variation of reproductive systems in angiosperms has been considered an important driver of line-age diversification.Closely related hermaphroditic and dioecious species with biotic pollination provide the opportunity to study and compare traits related to pollinator attraction and their con-sequences on reproductive components.A higher predictability of pollination syndromes is expected in dioecious species,which are dependent on pollinators,than in self-compatible hermaphroditic taxa.Dioecious species may suffer pollen limitation depending on the quality of floral rewards and the kind and abundance of pollina-tors,whereas no pollen limitation is expected in hermaphroditic spe-cies with autonomous self-pollination.Additionally,in the absence of pollen limitation,more or better seeds are expected in dioecious species,according to the sexual specialization hypothesis.Methods In natural populations of the hermaphroditic Fuchsia fulgens and Fuchsia arborescens and dioecious Fuchsia parviflora and Fuchsia obconica,all endemic to Mexico,we first described flower phenol-ogy,flower production and longevity and nectar volume and concen-tration.Then,we evaluated the correspondence between floral visitors and pollination syndromes.In hermaphrodite plants,we determined the level of herkogamy and the potential for autonomous self-pollina-tion.Finally,we evaluated the effect of pollen limitation on fruit set and seed number and assessed seed germination for all species.Important Findings In contrast to our prediction,dioecious species did not show a higher correspondence between pollination syndromes and floral visitors than did hermaphrodites;however,male flowers exhib-ited a higher correspondence than female flowers.No pollen limitation was detected in dioecious species,for which visitation rate did not differ between male and female flowers.The her-maphroditic F.fulgens showed pollen limitation for seed number,despite the presence of autonomous selfing.Fruit set from auton-omous pollination was higher in F.arborescens,which showed a lower level of herkogamy compared with F.fulgens.Finally,dioecious species produced fewer but heavier seeds compared with hermaphrodite species.Although Fuchsia is classified as an outcrossing genus,both hermaphroditic species showed autono-mous self-pollination.The heavier but lower number of seeds per fruit in dioecious species may be related to the more efficient resource allocation expected from sexual specialization.This could play an important role in the evolution of dioecy;however,a comparative phylogenetic approach is required to confirm this hypothesis.展开更多
文摘Reproductive systems are fundamental attributes for understanding life cycle and regeneration processes and provide information about seed production and genetic diversity. Analyses of reproductive strategies within communities and their associations with functional groups can indicate how physical and biological characteristics may influence the reproductive ecology of such communities. The main goal was to determine if the reproductive systems and their associated functional groups have particular characteristics related to extreme conditions and disturbance within xerophytic shrubland. Floral morphology analysis and four experimental tests were conducted to determine the reproductive systems of species and their associations with the life form, succulence, carbon metabolism, dispersal syndrome, pollination, and disturbance. Of the 144 plant species studied, 72.9% were hermaphrodite, 22.9% were monoecious, and 4.2% were dioecious. Dioecy was associated with woodiness, frugivory and undisturbed areas, while monoecy was more common in herbs. Adichogamy, protandry and herkogamy were more frequent than dichogamy, protogyny and no herkogamy, respectively. Xenogamous species tend to be woody and grow in undisturbed areas, while partially xenogamous species were mainly herbs occurring in disturbed areas. The majority of species were partially self-incompatible. High levels of outbreeding strategies tended to occur mainly in woody K-strategy species from undisturbed areas, mixed breeding strategies occurred in disturbed areas and overall community, and inbreeding strategies were associated with mostly herbaceous r-strategy primarily in disturbed areas.
基金National Science Foundation of China(31030016,31270281)to S.Q.H.
文摘Aims Distyly has been regarded as an adaptation to improve compatible pollination between two floral morphs with reciprocal herkogamy.The hypothesis that the different positions of anthers and stigmas within flowers as well as their reciprocal position between morphs,reduce the probability of self pollination raised by Darwin has been rarely tested.in this study,we measured stigmatic pollen loads in response to reduced reciprocal herkogamy in two Primula species.Methods To see whether reciprocal herkogamy can increase compatible and/or reduce incompatible pollen deposition,thus promoting compat-ible pollination,we shortened the distance between anthers and stigmas within the flowers by changing the position of the corolla tube,to which the anthers were fused,i.e.reduced herkogamy in natural populations of Primula secundiflora and P.poissonii and quantified stigmatic pollen loads in the field over 2 years.Important Findingsin both species,stigmatic pollen loads were significantly higher in the long-styled(l-morph)than in the short-styled morph(s-morph)in both control and manipulated flowers,but percentage of compatible pollen in s-morph were higher.Flowers manipulated to halve the anther-stigma distance showed a similar pattern for 2 years:total pollen grain counts on stigmas did not differ significantly but compatible pollen grains in l-and s-morphs were significantly decreased in both species.The percentage of compatible pollen loads was decreased by 68.7%in P.secundiflora and 65.3%in P.poissonii in l-morphs,while it decreased by 30.6%and 2.9%in s-morphs,respectively.our manipulation of the relative position of anthers and stigmas in the two distylous species indicated that a lower degree of herkogamy reduced compatible but incompatible pollen transfer was likely to increase.The higher proportion of compatible pollen in the s-morph than in the l-morph in the two Primula species could be attributed to the accessibility of two-level sexual organs,floral orientations and pollinator behaviors.This is a first attempt to manipulate intraflower herkogamy for understanding adaptation of heterostyly,shedding insights into how the reciprocal herkogamy promotes compatible pollination.
基金This research was supported by the Joint Funds of the National Science Foundation of China and Yunnan Provincial Government(no.U1202261)the National Natural Science Foundation of China(no.31500194)and the CAS 135 program(XTBG-F01,T01).
文摘Aims Distyly is one of the most widespread floral polymorphisms pro-moting cross-fertilization.Evolutionary transition from obligate cross-fertilized distyly to predominantly self-fertilized homostyly is frequently documented in various groups.However,empirical stud-ies concerning the ecological factors connected with this transition are still lacking.Primula chungensis,suggested to be evolving from distyly to homostyly,provides an ideal model for the study of the ecological factors concerned with this transition.We study P.chun-gensis to understand if autonomous self-fertilization would provide reproductive assurance for the self-fertilized homo-styled morph in the field.Methods the incompatibility features of P.chungensis were tested with hand-pollination experiments.We compared the capacity of autonomous self-fertilization between the distylous and homo-styled morph of P.chungensis in the field by excluding the pollinators with bags.In addition,the degrees of herkogamy of some P.chungensis plants were between the short-styled and homo-styled morphs.these plants were studied to understand whether they were able to obtain greater reproductive assurance when the herkogamy in the flowers was reduced.Important Findings All three morphs of P.chungensis were highly self-and intra-morph compatible.the degree of herkogamy positively correlated with the capacity for autonomous self-fertilization.A negative correlation between the degree of herkogamy and the magnitude of pollen limitation was found,but no significant correlation was found between the degree of herkogamy and the contribution of cross-fertilization to overall fertilization.this study suggests that reducing the degree of herkogamy can significantly increase the reproductive assurance for a self-compatible plant.Our results provided evidence that the homo-styled morph of P.chungensis had the highest capacity for autonomous self-fertilization and the highest seed production in the field,because autonomous self-fertilization provided reproduct-ive assurance for the homo-styled morph.this may cause selection towards the transition from distyly to homostyly.
基金This work was funded by a masters scholarship to A.A.-B.(no.270296)a research grant to E.C.from the Consejo Nacional de Ciencia y Tecnología(CONACyT grant no.105952)from the Universidad Michoacana de San Nicolás de Hidalgo.
文摘Aims The evolution of the outstanding variation of reproductive systems in angiosperms has been considered an important driver of line-age diversification.Closely related hermaphroditic and dioecious species with biotic pollination provide the opportunity to study and compare traits related to pollinator attraction and their con-sequences on reproductive components.A higher predictability of pollination syndromes is expected in dioecious species,which are dependent on pollinators,than in self-compatible hermaphroditic taxa.Dioecious species may suffer pollen limitation depending on the quality of floral rewards and the kind and abundance of pollina-tors,whereas no pollen limitation is expected in hermaphroditic spe-cies with autonomous self-pollination.Additionally,in the absence of pollen limitation,more or better seeds are expected in dioecious species,according to the sexual specialization hypothesis.Methods In natural populations of the hermaphroditic Fuchsia fulgens and Fuchsia arborescens and dioecious Fuchsia parviflora and Fuchsia obconica,all endemic to Mexico,we first described flower phenol-ogy,flower production and longevity and nectar volume and concen-tration.Then,we evaluated the correspondence between floral visitors and pollination syndromes.In hermaphrodite plants,we determined the level of herkogamy and the potential for autonomous self-pollina-tion.Finally,we evaluated the effect of pollen limitation on fruit set and seed number and assessed seed germination for all species.Important Findings In contrast to our prediction,dioecious species did not show a higher correspondence between pollination syndromes and floral visitors than did hermaphrodites;however,male flowers exhib-ited a higher correspondence than female flowers.No pollen limitation was detected in dioecious species,for which visitation rate did not differ between male and female flowers.The her-maphroditic F.fulgens showed pollen limitation for seed number,despite the presence of autonomous selfing.Fruit set from auton-omous pollination was higher in F.arborescens,which showed a lower level of herkogamy compared with F.fulgens.Finally,dioecious species produced fewer but heavier seeds compared with hermaphrodite species.Although Fuchsia is classified as an outcrossing genus,both hermaphroditic species showed autono-mous self-pollination.The heavier but lower number of seeds per fruit in dioecious species may be related to the more efficient resource allocation expected from sexual specialization.This could play an important role in the evolution of dioecy;however,a comparative phylogenetic approach is required to confirm this hypothesis.
