Abstract
Persistent soil seed banks are characteristic of Arctostaphylos
(Ericaceae) species in the Mediterranean-climate California Floristic
Province. While most species are obligate seeders, regeneration of
stands of all Arctostaphylos species ultimately depends on
post-fire seedling recruitment. Arctostaphylos seed banks are
created, in large part, by scatter-hoarding rodents. Variation in fruit
morphology, therefore, is expected to impact the
Arctostaphylos-rodent interaction. Seeds produce sufficient
rewards (nutritious mature embryo) to entice rodents to disperse and
ultimately bury seeds in the soil. Hard seed coats increase the time
required to extract the embryo, encouraging rodents to choose storage
over immediate predation, and endocarps are frequently empty. We
assessed the variation of fruit endocarp fusion and seed viability among
species of Arctostaphylos. Factors such as latitude, elevation,
life history, ploidy, and phylogenetic position were also analyzed.
Generalized mixed effects models were used to determine the factors
contributing to variation in fruit endocarp fusion and viability. Our
results indicate that fruit volume and shape are the most important
variables affecting endocarp fusion and seed viability. Additionally,
other potential influences only show a weak correlation and are not
predicted to significantly impact fruit endocarp fusion or viability.
These findings provide insight into evolved strategies used by plants to
increase reproductive success via scatter-hoarding rodents. Our study
benefits the conservation and restoration of Arctostaphylos
stands by emphasizing the importance of animal-mediated dispersal and
providing estimates of seed viability for different species. With the
anticipated effects of climate change, such as departures from historic
fire regimes, the preservation of the relationship between plants and
animal foragers is crucial for the continued survival of
Arctostaphylos and California’s evergreen chaparral.