Mating system of Pachycereus pringlei: an autotetraploid cactus (original) (raw)
Related papers
We studied seed germination and the growth and survivorship of seedlings of females and hermaphrodites of Pachycereus pringlei (cardon), a Mexican columnar cactus whose geographically variable breeding system includes trioecy and gynodioecy. Results of a two-year field experiment conducted near Bahia Kino, Sonora, Mexico and a ten-month laboratory experiment were similar and did not support the hypothesis that seedlings of females outperform those of hermaphrodites. In the field, percent seed germination and 2-yr seedling survivorship averaged 66% and 95%, respectively and did not differ among six treatment classes. Seedlings of hermaphrodites generally were larger than those of females at the end of both experiments. Selfed seedlings of hermaphrodites did not grow more slowly than outcrossed seedlings of hermaphrodites or females. Hermaphrodite seedlings performed best when pollinated with hermaphrodite pollen; female seedlings performed best with male pollen. We conclude that superior seedling performance cannot explain why females are able to coexist with hermaphrodites in populations of this cactus. Instead, we postulate that greater annual seed production, which averaged 1.6 times higher in females than in hermaphrodites in two years, may be sufficient to allow females to co-occur with hermaphrodites in this large, longlived plant, especially if sex determination involves cytoplasmic-nuclear inheritance.
Seedling performance in a trioecious cactus,Pachycereus pringlei: Effects of maternity and paternity
Plant Systematics and Evolution, 1999
We studied seed germination and the growth and survivorship of seedlings of females and hermaphrodites of Pachycereus pringlei (cardon), a Mexican columnar cactus whose geographically variable breeding system includes trioecy and gynodioecy. Results of a two-year field experiment conducted near Bahia Kino, Sonora, Mexico and a ten-month laboratory experiment were similar and did not support the hypothesis that seedlings of females outperform those of hermaphrodites. In the field, percent seed germination and 2-yr seedling survivorship averaged 66% and 95%, respectively and did not differ among six treatment classes. Seedlings of hermaphrodites generally were larger than those of females at the end of both experiments. Selfed seedlings of hermaphrodites did not grow more slowly than outcrossed seedlings of hermaphrodites or females. Hermaphrodite seedlings performed best when pollinated with hermaphrodite pollen; female seedlings performed best with male pollen. We conclude that superior seedling performance cannot explain why females are able to coexist with hermaphrodites in populations of this cactus. Instead, we postulate that greater annual seed production, which averaged 1.6 times higher in females than in hermaphrodites in two years, may be sufficient to allow females to co-occur with hermaphrodites in this large, longlived plant, especially if sex determination involves cytoplasmic-nuclear inheritance.
Perspectives in Plant Ecology, Evolution and Systematics, 2016
Mating systems and long-term climatic fluctuations have large impact on genetic diversity and population structure of plants; however, the genetic consequences have been poorly documented in species with geographic variation in mating systems. Here we used genetic variation from microsatellite markers to investigate the biogeographic pattern of Pachycereus pringlei, a columnar cactus with exceptional assortment of mating systems and wide range of distribution in the Sonoran Desert. Bayesian and multivariate analyses distinguished five genetic populations associated with differences in mating systems. Two hermaphroditic populations restricted to Cerralvo and Catalana islands were highly differentiated (Φ PT = 0.26 and 0.21, respectively). Cerralvo Island showed the lowest genetic diversity (H O = 0.26). Two other populations showed wide geographical distribution: a mostly gynodioecious population in the North comprising mostly hermaphrodite and female individuals, and a trioecious population in the South comprising unisexual and hermaphrodite individuals. The latter population exhibited the lowest level of genetic differentiation (Φ PT = 0.14) and highest genetic diversity (H O = 0.45). Cabo San Lucas, another trioecious population restricted to the southern end of the Baja California Peninsula, exhibits prevalence of unisexual individuals (0.76) but highly differentiated (Φ PT = 0.19) and relatively moderate genetic diversity (H O = 0.38). Latitudinal decrease of genetic diversity and isolation by distance supports northwards range expansion and southern BCP refugia, while Ecological Niche Models supported suitable climatic conditions during the Last Glacial Maximum in this region. These results suggest that the current biogeographic pattern of P. pringlei has been driven by longstanding climatic fluctuations associated with differential colonization abilities of genders and geographic variation of selfing and outcrossing rates. In conclusion, P. pringlei is not a 5 5 panmictic assemblage and the interaction of historical vicariance and dispersal processes with mating systems may well explain present-day patterns of genetic variation.
Comparative Cytogenetics, 2018
Polyploidy, the possession of more than two sets of chromosomes, is a major biological process affecting plant evolution and diversification. In the Cactaceae, genome doubling has also been associated with reproductive isolation, changes in breeding systems, colonization ability, and speciation. Pachycereus pringlei (S. Watson, 1885) Britton & Rose, 1909, is a columnar cactus that has long drawn the attention of ecologists, geneticists, and systematists due to its wide distribution range and remarkable assortment of breeding systems in the Mexican Sonoran Desert and the Baja California Peninsula (BCP). However, several important evolutionary questions, such as the distribution of chromosome numbers and whether the diploid condition is dominant over a potential polyploid condition driving the evolution and diversity in floral morphology and breeding systems in this cactus, are still unclear. In this study, we determined chromosome numbers in 11 localities encompassing virtually the entire geographic range of distribution of P. pringlei. Our data revealed the first diploid (2n = 22) count in this species restricted to the hermaphroditic populations of Catalana (ICA) and Cerralvo (ICE) Islands, whereas the tetraploid (2n = 44
Heredity, 2001
Genetic diversity was measured in the mixed-mating cactus, Melocactus curvispinus, in Venezuela. Allozyme diversity was surveyed in 19 putative loci over 18 populations. Compared to other plant taxa, this cactus is rich in polymorphic loci (P s 89.5%), with high numbers of alleles per polymorphic locus (AP s 3.82), but moderate levels of heterozygosity (H es 0.145). Substantial levels of inbreeding were detected across loci and populations at macrogeographic (F IS 0.348) and regional levels (F IS 0.194±0.402). Moderate levels of genetic dierentiation among populations were detected at macrogeographical (F ST 0.193) and regional (F ST 0.084±0.187) scales, suggesting that gene¯ow is relatively restricted, but increases within regions without topographic barriers. The population genetic structure observed for this cactus was attributed to, at least, three factors: shortdistance pollination and seed dispersal, the mixed-mating condition of the species, and genetic drift. High genetic identities between populations (I 0.942) supported the conspeci®c nature of all populations surveyed. The levels and patterns of genetic structure observed for M. curvispinus were consistent with its mating system and gene dispersal mechanisms.
Comparative cytogenetics, 2018
Polyploidy, the possession of more than two sets of chromosomes, is a major biological process affecting plant evolution and diversification. In the Cactaceae, genome doubling has also been associated with reproductive isolation, changes in breeding systems, colonization ability, and speciation. (S. Watson, 1885) Britton & Rose, 1909, is a columnar cactus that has long drawn the attention of ecologists, geneticists, and systematists due to its wide distribution range and remarkable assortment of breeding systems in the Mexican Sonoran Desert and the Baja California Peninsula (BCP). However, several important evolutionary questions, such as the distribution of chromosome numbers and whether the diploid condition is dominant over a potential polyploid condition driving the evolution and diversity in floral morphology and breeding systems in this cactus, are still unclear. In this study, we determined chromosome numbers in 11 localities encompassing virtually the entire geographic rang...
• Premise of the study: Microsatellite primers were developed for the cardon, a giant columnar cactus ( Pachycereus pringlei ) of the Sonoran Desert, to investigate intraspecifi c genetic patterns of diversity and population structure. • Methods and Results: Using 454 GS-FLX technology and bioinformatics tools, microsatellite primers were successfully identi- fi ed on 282 reads, including di-, tri-, tetra-, penta-, and hexanucleotides. A set of 10 primers were characterized on 80 individu- als collected in two areas of the Baja California peninsula, Mexico. All 10 loci were polymorphic, with a mean of 6.3 alleles per locus and overall levels of observed and expected heterozygosities ranging from 0.41 to 0.59 and from 0.40 to 0.57, respectively. Alleles per individual plant ranged from one to four, suggesting a polyploidal genome. • Conclusions: These loci should be useful for future investigations of population structure, genetic diversity, and gene fl ow in the cardon cactus. Key
Evolutionary Ecology, 2006
Stenocereus eruca is a prostrated, self-incompatible cactus endemic to the Sonoran Desert that regenerates primarily through clonal propagation. Clonal growth is expected to affect mate availability by influencing the number and spatial distribution of mating types. In this paper we examine the role of clonal growth on female fecundity through a series of pollination experiments in a population of S. eruca. We set up a pollen supplementation experiment using five distance treatments with pollen collected at 1, 10, 100, 1000 and 25000 m from receptor flowers during the years 2001 and 2002 and evaluated genetic sifmilarities between pairs of receptor-donor ramets through RAPD markers. Our data on fruit set, number of seeds/fruit, germination and overall fecundity revealed that S. eruca show a significant reduction in female fecundity when pollination occurs between ramets located at short distances (1 and 10 m), while genetic data showed high levels of similarity at those distances. The reduction in female fecundity is apparently a consequence of geitonogamy and inbreeding depression. Our data suggest that clonal growth and geitonogamy are likely to be partially responsible for the low levels of sexual reproduction and seedling recruitment observed in populations of S. eruca.
Influences of the genetic neighborhood on ramet reproductive success in a clonal desert cactus
Population Ecology, 2011
Clonal structure in clonal plants can affect sexual reproduction. Individual ramets can decrease reproduction if their neighbors are ramets of the same genet due to inbreeding depression or self-incompatibility. We assessed ramet reproductive success in the partial selfincompatible Ferocactus robustus (Cactaceae) as a function of floral display size in focal ramets and floral display size and clonal structure of their reproductive neighborhoods. Ramets were labeled, sized in number of stems, mapped and genetically identified through RAPD markers in one population. A pollen dispersal area of 15-m radius was established for each ramet to determine the clonal diversity in the neighborhoods. Flower production and fruit set were counted on a monthly basis during one reproductive season as a surrogate of ramet fitness. We expected a decrease in individual ramet reproductive success as a function of the number of reproductive ramets of the same genet in the neighborhood. A total of 272 sampled ramets revealed 116 multilocus genotypes, showing high clonal diversity in the population (G/N = 0.43, D = 0.98). Clonal diversity of neighborhoods ranged from 0.06 to 1 and fruit set varied from 0 to 76.9%. Individual ramet reproductive success was influenced by (1) mate availability, (2) floral display size of a genet within the reproductive neighborhood, and (3) the proportion of distinguishable genotypes. Floral display size of genets and ramets coupled with the genetic diversity within the reproductive neighborhood determines the low sexual reproduction in F. robustus.
2020
Grusonia bradtiana “viejito” (old man cactus) is an endemic species from Cuatro Cienegas Basin and nearby areas. Grusonia includes 17 clonal species distributed along North American deserts which grow in dense cushion or shrubs. Grusonia bradtiana reproduces sexually by flowering and fruiting, forming seeds with new genetic combinations (new genets). The species clones by fragmentation of stems of different sizes that root independently, producing genetically identical offspring (ramets). Clonal species develop complex reproductive interactions as pollination output depends on pollen transfer between genetically different genets or identical ramets. The hypothesis is that clonality negatively affects sexual reproduction as floral traits are adaptations to promote cross-pollination (among genets) and have evolved to reduce negative effects of inbreeding. We studied the reproductive biology of Grusonia bradtiana and assessed the effect of clonality upon its reproductive success with c...