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Background: The breeding system of Mammillaria magnimamma was initially described as hermaphroditic. However, some individuals in a natural population at Valle del Mezquital exhibited a seemingly non-functional androecium. Objectives: To determine the breeding system of M. magnimamma through morphological characterization of floral types. Study site and years: The study was conducted at Valle del Mezquital, Mexico, during the 2019 reproductive season. Methods: We characterized floral polymorphism by means of scanning electron microscopy and morphometric analysis of 18 floral traits. Pollinator frequency, size and number of seeds, and germination rate were compared between flower types. Results: 87.85 % of the plants were hermaphrodites, and 12.15 % were females with non-functional androecium, with significantly smaller stamens, indehiscent anthers, and malformed pollen. Female flowers were shorter (14.007 ± 0.742 mm) and had smaller (1.856 ± 0.151 mm) nectar chambers than hermaphroditic flowers (15.821 ± 0.450 and 2.194 ± 0.090 mm, respectively). Although pollinators visited hermaphrodites (124 visits) about twice as often as pistillate flowers (60 visits), the latter produced more numerous (F1,26 = 8.320, P = 0.003) and larger  (Hc = 4.637, P = 0.031) seeds that also germinated faster (Hc = 70.59, P < 0.0001). Conclusions: This M. magnimamma population exhibits a gynodioecious breeding system with both hermaphroditic and male sterile female plants. Females produce more, higher quality seeds, which favour their maintenance in the population.

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Soil fauna is essential for ecosystem dynamics as it is involved in biogeochemical processes, promotes nutrient availability, and affects the animal communities associated with plants. In this study, we examine the possible relationship between the soil microarthropod community on foliage production and quality of the shrub Pittocaulon praecox. We also examine the arthropods associated to its foliage, particularly the size of the main herbivores and of their natural enemies, at two sites with contrasting vegetation cover and productivity. The diversity of soil microarthropods was assessed from soil samples collected monthly under P. praecox individuals over 13 mo. Specimens collected were identified to species or morphospecies. Shrub foliage productivity was evaluated through the amount of litter produced. Resource quality was assessed by the mean content (percentage by weight) of N, C, S, and P of 30 leaves from each shrub. The mean size of herbivores and their natural enemies were determined by measuring 20 adult specimens of each of the most abundant species. We found a higher species richness of soil microarthropods and foliar arthropods in the open site, although the diversity of foliage arthropods was lower in the closed site. Shrubs growing in the closed site tend to produce more, larger, and nutritionally poorer (lower nitrogen content) leaves than open site. Herbivores and their natural enemies were also larger in the closed site. We found a significant positive relationship between the diversity and species richness of foliar arthropods and the nitrogen content of leaves. In general, species richness and diversity of both the foliar and soil fauna, as well as the size of organisms belonging to higher trophic levels, were affected by vegetation cover and primary productivity at each site. These findings highlight the need to simultaneously consider at least four trophic levels (soil organisms, plants, herbivores, and natural enemies) to better understand the functioning of these systems and their responses to environmental changes.

Domestication promotes divergence between wild and cultivated plants. The “plant domestication-reduced defense” hypothesis proposes that cultivated plants have lower chemical defenses and resistance against herbivores than their wild counterparts. Yet, the effects of domestication on the interactions between perennial crops and insect herbivores have not been well-documented. In this study, we hypothesized that domesticated avocado (Persea americana) has lowered resistance against insect herbivores. To test this hypothesis, we measured variation in plant traits (fruit and seed size, seed germination, and plant growth), chemical defenses (total phenolics), and resistance against two leaf-chewing insect herbivores—a specialist (Copaxa multifenestrata) and a generalist (Spodoptera frugiperda)—among seven avocado genotypes across a domestication gradient: wild (ancestral) genotypes, five (intermediate) landraces (“Blanco,” “Lonjas,” “Vargas,” “Zarcoli,” and “Rodolfo”), and the cultivated (modern) “Hass.” Our results showed that seeds from “Hass” have a lower germination rate and slower growth and have shorter fruits and seeds than the landraces and wild genotypes. “Hass” leaves also had lower amounts of total phenolics than the landraces; however, no differences were found between “Hass” and the wild genotypes. There was no effect of genotype on larval mass gained for both herbivores. However, C. multifenestrata had longer larval longevity on “Hass” and the wild genotypes, whereas S. frugiperda larval longevity showed no differences among genotypes. Moreover, C. multifenestrata inflicted more damage on “Hass,” whereas S. frugiperda inflicted more damage on “Lonjas” than on the other genotypes. In general, bigger fruit and seeds were positively correlated with plant size and phenolic content, and total phenolics were positively correlated with S. frugiperda and negatively correlated with C. multifenestrata larval performance. However, despite the genotypic variation in plant traits, phenolic content, and resistance against two herbivores with different levels of specialization, there was no clear support for the “plant domestication-reduced defense” hypothesis in avocado.