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Federal Register / Vol. 86, No. 246 / Tuesday, December 28, 2021 / Proposed Rules
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TABLE 2RESILIENCY OF THE SEVEN FOOTHILL YELLOW-LEGGED FROG ANALYSIS UNITS
Analysis unit
Current condition
Lower change scenario
Mean change scenario
Higher change scenario
North Coast DPS Oregon.
North Coast DPS California.
North Feather DPS

Intact Resiliency

Slightly reduced from current

Slightly reduced from current

Markedly reduced from current.

Intact Resiliency

Slightly reduced from current

Markedly reduced from current
Reduced Resiliency

No change

Markedly reduced from current.
Risk of functional extirpation.

North Sierra DPS
South Sierra DPS

Intact Resiliency
Substantially Reduced Resiliency.

Slightly reduced from current
Slightly reduced from current

Central Coast DPS

Substantially iency.

Slightly reduced from current

South Coast DPS

Extensively Reduced Resiliency
Markedly reduced from current Markedly reduced from current.
Risk of functional extirpation or extirpation.
Markedly reduced from current.
Risk of functional extirpation or extirpation.
Markedly reduced from current.
Risk of extirpation.

Greatly reduced from current.
Risk of functional extirpation.
Greatly reduced from current.
Risk of functional extirpation or extirpation.
Greatly reduced from current.
Greatly reduced from current.
Risk of functional extirpation or extirpation.
Greatly reduced from current.
Risk of functional extirpation or extirpation.
Greatly reduced from current.
Risk of extirpation.

Reduced
Representation Representation describes the ability of a species to adapt to changing environmental conditions. This includes both near-term and long-term changes in its physical e.g., climate conditions, habitat conditions, habitat structure, etc. and biological e.g., pathogens, competitors, predators, etc.
environments. This ability of a species to adapt to these changes is often referred to as adaptive capacity. To assess the current condition of representation for the foothill yellowlegged frog, we considered the current diversity of ecological conditions and of genetic material throughout the range of the species.
There are considerable ranges of ecological conditions under which foothill yellow-legged frogs occur. As discussed in the SSA Report Service 2021, Section 2.7 and CHAPTER 3, there are substantial differences in latitude, elevation, precipitation, average temperature, and vegetative community across the species range.
Parts of the foothill yellow-legged frog range also differ in terms of species composition and in hydrology rain-fed versus snow-fed systems. Exemplary of these different ecological conditions, foothill yellow-legged frog tadpoles from snow-fed Sierra Nevada populations have higher intrinsic growth rates than tadpoles from rain-fed coastal populations, likely due to their constraint to a shorter rearing season in the Sierra Nevada Catenazzi and Kupferberg 2017, pp. 1255, 12601261.
As described in the SSA report Service 2021, Section 2.6, two rangewide assessments of foothill yellow-legged frog genomic datasets revealed that this taxon is extremely differentiated following biogeographical boundaries McCartney-Melstad et al.
2018, p. 112; Peek 2018, p. 76. The clades that are most genetically
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Resil-

Slightly reduced from current.
Risk of extirpation.

divergent i.e., South Sierra, Central Coast, and South Coast clades, and thus could contribute most to the overall adaptive capacity of this taxon McCartney-Melstad et al. 2018, p. 120;
Peek 2018, p. 77, are also the clades with the lowest levels of population resiliency. The South Sierra and Central Coast clades have substantially reduced resiliency and the South Coast clade has extensively reduced resiliency SSA
Report Service 2021, Section 8.5. The reduced resiliency in these clades, means that the foothill yellow-legged frog is especially vulnerable to loss of this genetic diversity. The Central Coast and South Coast clades are the most genetically divergent, indicating that a significant amount of the taxons overall genetic diversity would be lost if either clade were extirpated. The Central Coast and South Coast clades are also ecologically unique because they have lower annual precipitation and higher mean annual temperatures than elsewhere in the range of the species PRISM Climate Group 2012, 30-year climate dataset; Table 3 and the region hosts the highest freshwater endemism of anywhere in the species California range Howard et al. 2013, p. 5.
While not as at risk of extirpation, the northern Sierra clades i.e., North Feather and North Sierra clades might also have unique adaptive potential in the face of climate change because of their admixture history and intermediacy to the South Sierra and North Coast clades McCartney-Melstad et al. 2018, p. 121. The genetic clade that is comprised of the two North Coast units is also genetically valuable to the foothill yellow-legged frog because it contains the greatest genetic diversity and is the only part of the range that shows a trajectory of increasing genetic diversity McCartney-Melstad et al.
2018, pp. 120121; Peek 2018, p. 74.
The North Coast clade also potentially
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provides connectivity and a large latitudinal gradient for responding to the effects of climate change.
While the foothill yellow-legged frog clearly has a range of genetically divergent populations, it has likely already lost a lot of diversity due to large extirpations in the southern analysis units. The species is also at risk of further losses amidst trends toward decreasing occupancy and decreasing connectivity. The foothill yellow-legged frog is exhibiting an overall trend of decreasing genetic diversity in spite of the trend of increasing genetic diversity in the North Coast clade McCartneyMelstad et al. 2018, pp. 120121; Peek 2018, p. 74.
The trend of decreasing genetic diversity in the foothill yellow-legged frog may be leading to losses in adaptive capacity i.e., ability to adapt to change.
Loss of adaptive capacity lowers the species viability because the decrease in ability to adapt to change increases extinction risk in the face of future changes. For foothill yellow-legged frog conservation, McCartney-Melstad et al.
2018, p. 122 strongly recommended that each of the major genetic groups be managed as independent recovery units.
Peek 2018, p. 77 also recommended that conservation actions should prioritize protecting foothill yellowlegged frogs in the Central Coast, South Coast, and South Sierra clades because they are simultaneously the most distinct, divergent, and at-risk populations.
Redundancy Redundancy describes the ability of a species to withstand catastrophic events. To assess redundancy for each analysis unit, we considered the 1
quantity of occupied stream segments proxy for subpopulations SSA Report Service 2021,Table 10, 2 spatial distribution of occupied stream
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