Larval Life History of Coastal Tailed Frogs (Ascaphus truei) Across an Elevational Gradient in Northern California: Implications for a Changing Climate
Coastal Tailed Frogs (Ascaphus truei) range across the Pacific Northwest from northern California, USA, into British Columbia, Canada, and from sea level to >2,131 m. Previous work has shown a variable larval period but has not clearly separated elevational from latitudinal effects. Therefore, we examined size at beginning of metamorphosis, larval period, individual growth rates, and timing of metamorphosis of A. truei populations along an elevational gradient from 152 to 2,131 m across a small latitudinal range (29 km) to reduce potential latitudinal effects, all within the Klamath Mountains of northern California. We sampled larvae at 15 study sites, of which we used 6 sites as intensive capture–mark–recapture (CMR) locations, and the other 9 for supplemental data on larval period and size at metamorphosis. In CMR sites, we individually marked tadpoles to determine within-season growth rates. We found that the A. truei larval period in these populations ranges from 2 yr in low and middle elevations to ≥3 yr in high-elevation populations. We also found decreased size at beginning of metamorphosis and increased growth rates of tadpoles with increasing elevation. Our high-elevation populations had the longest larval period documented in California. The associations of growth and timing of metamorphosis to elevation in A. truei populations suggest that responses to changing climate may differ across elevations.Abstract
Capture–mark–recapture (CMR) and ancillary (non-CMR) study sites across low (152 to 610 m), mid (930 to 1,487 m), and high (1,969 to 2,131 m) elevations within the Trinity River watershed in northern California, USA.
Body length (mm) of Ascaphus truei tadpoles at developmental stage 40 (beginning of metamorphosis) across low (152 to 610 m; n = 441), mid (930 to 1,487 m; n = 660), and high (1,969 to 2,131 m; n = 510) elevations. Horizonal lines represent medians, and upper and lower hinges correspond to first and third quartiles (the 25th and 75th percentiles). Whiskers extend from hinges to the largest value (upper) and smallest value (lower) no further than 1.5 times the interquartile range, and points are outliers.
Density plots of total length (mm) in Ascaphus truei tadpoles sampled at different field sites across the elevational gradient (low: 152 to 610 m; mid: 930 to 1,487 m; and high: 1,969 to 2,131 m) through the survey season. Tadpoles in metamorphosis (stage ≥40) are omitted. * indicates when the first metamorphosing tadpole was found.
Density histogram of Ascaphus truei tadpole cohort-size variation using total length (mm) between two high-elevation sites: Siligo (2,076 m) and East van Matre (2,040 m) creeks.
Growth rates of Ascaphus truei tadpoles by month of the survey season at low (152 to 610 m), mid (930 to 1,487 m), and high (1,969 to 2,131 m) elevations. Numbers in boxplots indicate sample size. Horizonal lines represent medians, and lower and upper hinges correspond to first and third quartiles (the 25th and 75th percentiles). Whiskers extend from hinges to the largest value (upper) and smallest value (lower) no further than 1.5 times the interquartile range, and points are outliers.
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