From ovule to new plant
In Lophophora diffusa, population recruitment proceeds through several successive stages. Pollen must reach the stigma, ovules must develop into seeds, and the seeds must reach conditions that allow germination. The young plant must then survive the period after the radicle emerges. Each stage changes the number of individuals that ultimately join the population. Seven years of observations of one population in the Mexican state of Querétaro allowed these processes to be combined into a single demographic picture. [Briseño-Sánchez et al. 2022, Materials and methods, Table 1–3]
The study ran from January 2015 to November 2021 over an area of approximately 20 × 30 m. Initially, 468 plants were marked, of which 340 were classified as reproductive based on a diameter exceeding 3 cm. Counts of buds, open and spent flowers, and fruits were supplemented by insect observations, assessments of flower damage and an experiment on seed fate. Searches for seedlings were conducted twice a year, with particular attention around adult cacti and beneath shrubs. [Briseño-Sánchez et al. 2022, Materials and methods]
Pollen and dependence on visiting insects
Controlled pollination described in the 2020 paper indicates a predominance of pollination with pollen from other plants and partial self-incompatibility. Hand application of self-pollen produced fruits less often than cross-pollination. Flowers isolated without pollen transfer did not produce fruits. Additional pollen supplied to flowers visited by insects increased seed production. The authors identified pollen limitation, a situation in which the natural supply of suitable pollen limits reproductive output. The degree of self-compatibility and the need for physical pollen transfer describe two different elements of this system. [Briseño-Sánchez et al. 2020, pp. 246, 248–249, 251–252]
In 2018, nectar secretion was assessed in 70 flowers on 62 plants. The flowers were protected from insects, and nectar accumulated between 9 and 14 hours was measured. It was detected in 78% of the flowers examined. Among flowers containing nectar, the mean volume was 0,054 ± 0,007 µl, with the standard error. The highest value reached 0,36 µl, and most measurements remained below 0,1 µl. The result applies to this part of the day. The authors considered the small nectar supply a possible factor limiting flower attractiveness. [Briseño-Sánchez et al. 2022, Materials and methods, Results]
A changing insect assemblage
In 2017, 2018 and 2021, groups of three to six plants with three to eleven flowers were observed. A fifteen-minute observation was conducted in each hour between 10 and 14 hours. Touching the anthers or stigma was considered meaningful contact. Solitary bees of the genera Macrotera, Lasioglossum and Ashmeadiella, and Acmaeodera beetles were recorded. Such contact indicates the possibility of pollen transfer. The effectiveness of individual insects, measured as seed formation after a single visit, was not compared. [Briseño-Sánchez et al. 2022, Materials and methods, Results, Fig. 1]
The composition of visitors changed between seasons. In 2017 and 2021, Macrotera accounted for 41% and 95% of visits, respectively, while in 2018 Acmaeodera predominated with a share of 70%. The mean visitation rate in the observed groups was 6,00 ± 1,62, 2,34 ± 0,96 and 5,88 ± 1,38 flowers visited per hour, with the standard error. The numbers describe the groups and observation intervals studied. Fluctuations in insect activity were a variable element of reproductive conditions in this population. [Briseño-Sánchez et al. 2022, Results, Fig. 1]
Feeding on flowers
Damage to the perianth, anthers and stigma provides a separate pathway limiting seed production. In 2021, 113 flowers on 92 plants were assessed. Evidence of flower parts being eaten was found in 26 flowers, approximately 23% of the sample. Damage most often involved the perianth and anthers. Flowers with a damaged stigma and flowers with simultaneous destruction of the perianth, anthers and stigma were less numerous. [Briseño-Sánchez et al. 2022, Table 2]
In the first two categories, fruits developed from 26% and 16% of damaged flowers, respectively. No fruits were recorded in the category involving both types of reproductive organ. The assessment was observational. It distinguished degrees of damage, and the direct loss of organs helped explain some failures. A possible reduction in the attractiveness of partly eaten flowers to insects remains an additional interpretation by the authors. [Briseño-Sánchez et al. 2022, Table 2, Discussion]
Numbers of flowers, fruits and seedlings
Flower production and the proportion of flowers forming fruits were uneven. The highest flower count, 835, was recorded in 2018. The highest proportion setting fruit occurred in 2019, when there were 115 flowers. A high percentage of fruiting flowers therefore coincided with low total flower production. The entire sequence from flower numbers to seedling numbers matters for recruitment. [Briseño-Sánchez et al. 2022, Table 1]
| Year | Number of flowers | Flowers forming fruits | New seedlings |
|---|---|---|---|
| 2015 | 462 | 44,3% | 21 |
| 2016 | 562 | 22,2% | 21 |
| 2017 | 783 | 26,3% | 31 |
| 2018 | 835 | 44,5% | 30 |
| 2019 | 115 | 62,6% | 5 |
| 2020 | 162 | 25,9% | 1 |
| 2021 | 423 | 32,8% | 18 |
A total of 127 new seedlings were recorded. Annual numbers ranged from one to 31. Some of the smallest plants may have been overlooked despite repeated intensive searches. The compilation documents actual recruitment over seven years of observation. Differences between years concern this population and do not establish a fixed rhythm of seedling emergence for the species as a whole. [Briseño-Sánchez et al. 2022, Table 1, Results]
Seed fate after leaving the fruit
In spring 2021, three seed-exposure treatments were compared. One was covered with mesh, another allowed access to ants and other small insects, and the third remained open. Each treatment comprised 20 units of five seeds, a total of 300 seeds obtained from fruits of 25 plants. Remaining seeds and evidence of feeding were checked for two weeks. In the open treatment, seeds were attached with a drop of silicone to mesh in contact with the ground. The result applies to this exposure arrangement. [Briseño-Sánchez et al. 2022, Materials and methods]
Approximately 86% of the seeds remained at the end. Recognisable evidence of consumption was found in less than 1% of the entire sample. Some disappearing seeds may have been eaten, and others moved. No statistically significant differences between the three treatments were demonstrated. The experiment therefore describes a short period of seed fate in one season. In reconstructing recruitment, the authors used the same estimate for the other years and considered two scenarios for missing seeds. [Briseño-Sánchez et al. 2022, Results, Materials and methods]
Seeds stored for four years
Seed tolerance of storage was examined separately. In an experiment conducted in 2018 and published in 2024, seeds collected in 2014 and 2018 were compared. In both years, fruits were collected from 20 plants, and seeds were pooled from successive months of collection. Seeds were stored in paper bags at 20 ± 2°C. 50 seeds from each batch were sown, five per dish, on 1% bacteriological agar. The chamber maintained 25°C and a twelve-hour photoperiod. [Briseño-Sánchez et al. 2024, pp. 4–5]
Germination was 62% in the batch from the year of the experiment and 52% in the four-year-old batch. The authors' analysis found no significant difference in the final level of germination. Survival of the resulting seedlings also did not differ significantly and reached 61% and 58%, respectively, by the end of observation. The older seeds therefore retained the ability to germinate, and some of their seedlings survived the initial period studied. The germination percentages presented are observed results, separate from the asymptotes of the fitted model. [Briseño-Sánchez et al. 2024, pp. 5–7, Fig. 3–4]
| Collection year and storage | Seeds in the sample | Observed germination | Seedling survival |
|---|---|---|---|
| 2018, from the year of the experiment | 50 | 62% | 61 ± 5,92% |
| 2014, approximately four years | 50 | 52% | 58 ± 4,81% |
Seed longevity and recruitment in the habitat
The ability to germinate after four years of storage indicates the longevity of the tested batches under specific laboratory conditions. The authors combined this with earlier information about the light requirement for germination and proposed the hypothesis of a short-term persistent seed bank. Such a bank consists of seeds that remain alive in the soil for more than one year, but no more than five years. Confirming its existence in L. diffusa requires measurements of seeds present in the habitat and their survival under natural conditions. [Briseño-Sánchez et al. 2024, pp. 7–9]
The experiment included two different collection batches, so the effect of storage duration itself coexists with possible differences between years and maternal plants. In cultivation, information about the collection year and storage conditions helps assess sowing results. Documented germination of four-year-old seeds allows an older batch to be included in a sowing trial. Subsequent development is assessed separately, because survival measured here over a short laboratory period describes the beginning of a seedling's life. [Briseño-Sánchez et al. 2024, pp. 4–9]
Full texts of the 2022 and 2024 studies, and the abstract and selected parts of the methods and results of the 2020 paper. Table data checked in rendered PDF pages. Laboratory conditions, two collection years and natural recruitment are described separately.
Biotic interactions prior to seed dispersal determine recruitment probability of peyote (Lophophora diffusa, Cactaceae), a threatened species pollinator-dependent
Briseño-Sánchez M. I., Martorell C., Valverde P. L., Mandujano M. C., Biotic interactions prior to seed dispersal determine recruitment probability of peyote (Lophophora diffusa, Cactaceae), a threatened species pollinator-dependent, Plant Ecology, 2022, 223(10–12):1193-1206, doi: 10.1007/s11258-022-01267-0
The seven-year study of recruitment in one Lophophora diffusa population in Querétaro includes flower, fruit and seedling counts, nectar measurements, insect observations, flower damage assessment and a seed removal experiment. The authors compare probabilities of successive transitions from ovule to seedling. They analyse the importance of limited pollination and florivory before seed dispersal, and conditions for early development. The seed removal experiment was conducted in 2021, and its estimates were applied to all years.
Efecto de la edad de las semillas en la germinación y la supervivencia de plántulas de Lophophora diffusa (Cactaceae)
Briseño-Sánchez M. I., Nava-Osorio J., Rojas-Aréchiga M., Mandujano M. C., Efecto de la edad de las semillas en la germinación y la supervivencia de plántulas de Lophophora diffusa (Cactaceae), Acta Botanica Mexicana, 2024, 131:e2146, doi: 10.21829/abm131.2024.2146
The experiment conducted in 2018 compares germination and early seedling survival in two Lophophora diffusa seed lots collected in 2014 and 2018. Seeds were stored in paper bags at 20 ± 2°C and sown on agar at 25°C with a 12-hour photoperiod. The results indicate retained germination capacity after about four years. The authors consider the potential to form a seed bank, whose presence in the soil requires further field verification.
Population structure and reproductive biology of peyote (Lophophora diffusa, Cactaceae), a threatened species with pollen limitation
Briseño-Sánchez M. I., Martínez-Peralta C., Mandujano M. C., Population structure and reproductive biology of peyote (Lophophora diffusa, Cactaceae), a threatened species with pollen limitation, Journal of the Torrey Botanical Society, 2020, 147(3):243-257, doi: 10.3159/TORREY-D-18-00055.1
Population structure and controlled pollination indicate predominantly cross-pollination, partial self-incompatibility and pollen limitation. The abstract and selected methods and results passages in the text supplied by the author were checked.
