DEER MICE AND LOW PRECIPITATION LIMIT SEEDLING RECRUITMENT IN A RARE, ENDEMIC ISLAND SHRUB (MALVA ASSURGENTIFLORA SUBSP. ASSURGENTIFLORA)

Seedling recruitment is often a limiting factor for the reintroduction of rare species. An example of this is Malva assurgentiflora (Kellogg) M.F. Ray subsp. assurgentiflora, Malvaceae (Northern Island Mallow hereafter), a rare shrub endemic to two of the California Channel Islands (Anacapa and San Miguel Islands). It was presumed extirpated from Anacapa in the 1990's but was reintroduced starting in 2000. Unfortunately, almost no new recruits have been observed since reintroduction. To understand the local environmental factors limiting recruitment, we performed manipulative experiments that assessed 1) seed limitations during the pre- and post-dispersal seed life history stages, and 2) microsite and habitat limitations during the seedling life history stage, both in the presence and absence of the Gambel's Deer Mouse (Peromyscus gambelii)—a common seed predator of the Northern Island Mallow. We found that deer mice significantly reduce seed availability during the pre- and post-dispersal life history stages. Seeds successfully germinated in the absence of deer mice, suggesting seedling presence is likely more limited by deer mouse predation than by microsite availability. However, despite the limitations by deer mice at these stages, most seedlings died from desiccation regardless of treatment, suggesting that precipitation levels are more important to seedling survival, and ultimately recruitment, than deer mouse predation. Our results show that more extensive Northern Island Mallow recruitment likely requires the simultaneous alignment of favorable conditions, such as low deer mouse densities and sufficient precipitation. Land managers may be able to aid the recruitment process through timing seed collection and restoration activities to coincide with favorable environmental conditions.