Background:

Floral and reproductive attributes influence the capacity of plants to produce gametes, the efficiency of pollen transfer, the development of viable seeds, and the recruitment of new individuals.

Question:

What morphological attributes characterize sexual whorls in E. strictiflora and E. subalpina? Do intra and interspecific mating systems impact on seed production and germinability?

Studied species:

Echeveria strictiflora and Echeveria subalpina.

Study site:

In ex situ conditions in Mexico City from 2018 to 2020.

Methods:

The spatial position and arrangement of the sexual whorls were described. The morphology of pollen grains and ovules were characterized by optical and scanning electron microscopy. The intra- and interspecific outbreeding and mating systems, as well as the production and germination of seeds were determined under controlled conditions.

Results:

Both E. strictiflora and E. subalpina are herkogamous, have a mixed breeding system, and produce seeds by reciprocal hybridization. Abundant viable pollen and ovules are produced. Species are self-compatible, however, the reduction in the production and viability of the seeds produced by selfing, suggests that there is a detrimental effect due to inbreeding depression.

Conclusions:

E. strictiflora and E. subalpina produce fruits and seeds by selfing and intra- and inter-specific outbreeding, but inbreeding depression limits recruitment, revealing the importance of conserving populations with sufficient individuals to retain diversity, as well the areas of natural distribution.