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Federal Register / Vol. 86, No. 85 / Wednesday, May 5, 2021 / Proposed Rules range of soil types USFWS 1984, p. 50.
It is often associated with maritime cactus scrub vegetation on coastal flats at the southwestern end of the island Junak and Wilken 1998, p. 256.
SCI bush-mallow flowers in the spring and summer, typically from March to August Kearney 1951, p. 115; California Native Plant Society 2011. It is generally thought that SCI bush-mallow is pollinated by insects; potential pollinators incidentally observed in the wild include wasps and butterflies USFWS 2007, p. 9. Although no specific pollinator for this species is known, the shape of the flowers suggest that it is not limited to a specific pollinator and instead can be pollinated by different pollinators Muller and Junak 2011, p. 33.
While each plant is capable of making large numbers of seeds, recorded seed production in natural occurrences of SCI bush-mallow has been very low Helenurm 1997, p. 51; Helenurm 1999, p. 39; Junak and Wilken 1998, p. 291.
Germination rates in seed trials are also low, only 4 to 35 percent Evans and Bohn 1987, p. 538; Junak and Wilken 1998, p. 291. Hypotheses for low seed set and germination rates include low pollinator visitation rates, reduced pollinator diversity, partial selfincompatibility i.e., plants need to be pollinated by a non-closely related individual, limited survey efforts, and that seed germination may be stimulated by fire USFWS 2020b, pp. 2223.
However, it is difficult to determine the cause of the apparent low reproductive output noted, whether low reproductive output is still an issue currently, and whether fire assists germination.
SCI bush-mallow can reproduce vegetatively, or clonally, by sprouting from rhizomes Evans and Bohn 1987, p.
538, as well as sexually by seeds, although sexual recruitment is likely low. The ability to spread vegetatively by underground rhizomes results in patches of spatially separate but genetically identical individuals Evans and Bohn 1987, p. 538. Occurrences are likely a mix of both genetically unique individuals genets and clonal individuals ramets that are connected underground. Although difficult to discern between ramets and genets in the field, most groups of plants are comprised of ramets from an unknown
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number of genets, consistent with other plant species exhibiting strong clonal growth. Although growth and spread of the population has been thought to be mostly clonal Muller and Junak 2011, p. 50, seedlings have on occasion been identified in the field by the presence of cotyledons embryonic leaf in seedbearing plants Munson 2019, pers.
comm.. While the distribution of SCI
bush-mallow is much greater than was known at the time of listing, difficulty and confusion with discerning between ramets and genets and low reproductive output create uncertainty about whether it is reproducing sexually or only clonally.
Two different studies of population genetics have been conducted Helenurm 1997; Helenurm 1999.
These genetic assessments along with field observations indicate that overall genetic diversity is low, but there is some genetic diversity within and among patches of SCI bush-mallow i.e., based on these studies, not all individuals are clones in each area.
However, due to the limitations of techniques, neither study is conclusive.
Genetic diversity is presumed to have declined since the introduction of feral browsers and grazers, but we do not know historical or current levels of genetic diversity or normal rates of sexual versus asexual reproduction, so no comparisons can be made. Overall, genetic diversity within SCI bushmallow is still very low compared with other island endemic plant taxa Helenurm 1999, p. 40.
This species may be subject to drought stress to some extent from 25
to 89 percent of individuals sampled, which may reduce flowering Muller and Junak 2011, p. 58. This species may be drought deciduous as is a closely related species of bush-mallow, Malacothamnus fasciculatus, but there are no physiological studies to support this conjecture; the similar phenology of SCI bush-mallow and its habitat attributes support the suggestion Muller and Junak 2011, p. 32.
Although there is no information regarding the fire tolerance of SCI bushmallow, other species in the same genus are fire-tolerant and able to adapt Rundel 1982, p. 86. Seed germination in other species in the genus is stimulated by fire, and there is evidence
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that fire may also have a positive effect on SCI bush-mallow. Because of its ability to resprout from rhizomes and the adaptation of other species in the genus to fire, it is thought that SCI bushmallow is likely resistant to fire and that its seeds may even respond positively to fire USFWS 2008b, p. 77.
San Clemente Island Paintbrush A thorough review of the taxonomy, life history, and ecology of the San Clemente Island paintbrush is presented in the SSA report USFWS 2020e.
San Clemente Island paintbrush Castilleja grisea is a highly branched perennial subshrub in the broomrape family Orobanchaceae endemic to SCI
Chuang and Heckard 1993, p. 1021
and is the only representative of the genus Castilleja found on the island Helenurm et al. 2005, p. 1222. SCI
paintbrush is typically 11.5 to 31.5 in 29 to 80 cm in height and covered with dense white, wooly hairs. Most Castilleja species have bisexual flowers disposed in terminal spikes. The flowers of SCI paintbrush are yellow.
SCI paintbrush is thought to have been relatively common on SCI in the 1930s, and subsequently declined as a result of unchecked grazing by introduced feral herbivores Helenurm et al. 2005, p. 1222. The complete historical range of SCI paintbrush on SCI is unknown because botanical studies were not completed before the plants decline. Herbarium records documented the species on the south and east sides of the island before the time of listing California Consortium of Herbaria 2019, records for C. grisea. By 1963, SCI paintbrush was reported as rare or occasional Raven 1963, p. 337.
Since the complete removal of feral ungulates from SCI by 1992, SCI
paintbrush has been detected across the southern two-thirds of the island Keegan et al. 1994, p. 58; Junak and Wilken 1998, pp. 1416, GIS data; Junak 2006, pp. 1176, GIS data; Tierra Data Inc. 2008, pp. 124, appendices and GIS
data; SERG 2010a and 2010b, GIS data.
The current abundance and distribution of SCI paintbrush is estimated to be comprised of 601 locations totaling 48,181 individuals occupying 87
watersheds see Figure 3, below USFWS 2020e, pp. 2729.

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