Exploring local adaptation to salinity and temperature variability in the copepod Tigriopus californicus

Meeting Abstract

48-3  Sunday, Jan. 5 10:30 – 10:45  Exploring local adaptation to salinity and temperature variability in the copepod Tigriopus californicus LIGUORI, AL; Stony Brook University alyssa.liguori@stonybrook.edu https://alyssaliguori.com/

Local adaptation has been studied in a broad range of taxa for decades. However, we have limited understanding of how often local adaptation occurs in variable environments. Whether phenotypic plasticity can evolve in distinct ways among populations experiencing different patterns of abiotic variability is unclear. Abiotic conditions in coastal marine habitats can be highly heterogeneous, which might promote local adaptation. Tigriopus californicus (tidepool copepod) populations on San Juan Island, WA have distinct morphology and life history. The goal here was to test whether these differences are a result of local adaptation, and to quantify responses to different magnitudes of temperature variation. To identify potential selective pressures in the field, temperature and salinity were measured in high shore pools for 6 months. A common garden experiment with factorial combinations of 7 temperature and 2 salinity (32, 55 ppt) treatments was conducted on 3 populations. Two temperature treatments varied daily, both with an average of 20°C, but different ranges (low amplitude: 15-25°C, high amplitude: 10-30°C, 12:12 hour exposure). The other 5 treatments were the average, maximum, and minimum temperatures held stable. Fecundity, survivorship, and development were characterized across two generations. Preliminary results show differences in abiotic variability among sites, despite their geographic proximity. The experiment revealed strong effects of temperature on fecundity and survival, but these effects were not the same among populations. Abiotic patterns in the field did not seem to explain the observed population differences, thus limited evidence for local adaptation was found. For these populations, differences in selective pressures among sites might not be strong enough to overcome the influence of genetic drift.

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