Floral morphometry, anthesis, and pollination success of Mammillaria pectinifera (Cactaceae), a rare and threatened endemic species of Central Mexico

• Flowers showed diurnal anthesis and almost all opened only a single day.
• Analyses of flower morphology revealed significant differences among populations.
• Herkogamy was positive and significantly different among populations.
• Field experiments revealed that open-pollinated flowers were highly successful.
• This study showed the dependency of M. pectinifera on insect pollinators to produce fruits and seeds.

Reproductive biology in the highly diverse Cactaceae family is described in only few species. Given that a large number of species are rare, threatened, or endangered, and the entire family is included in Appendix II of CITES, the limited knowledge about their reproductive biology is of major concern. Mammillaria pectinifera is an endangered, small, globose cactus endemic to the Tehuacán-Cuicatlán region in Central Mexico. We aimed to characterize some basic aspects of its reproductive biology in three populations. We described flower morphology and anthesis, identified floral visitors, and evaluated the occurrence of spontaneous self-fertilization and the success of open pollination. Diurnal anthesis in flowers lasted about 4 h/day and almost all flowers lasted only one day after opening. The analyses of variance revealed differences in flower morphology among populations. Herkogamy was positive and significantly different among populations. Field experiments revealed that open-pollinated flowers were highly successful in setting fruits and seeds. These results corroborate those reported in other Mammillaria species. Autonomous self-pollination was negligible and ineffective. Bees of the genus Ceratina were dominant among the captured flower visitors, and estimations of their maximum foraging distance indicated successful outcrossing in plants. This study indicates almost complete dependency of M. pectinifera on pollinators for fruits and seeds production. Our results serve as a basis for future research on reproductive biology of M. pectinifera and other rare and endangered cacti.