Title

Absence of cryptic variation in response to elevated temperatures in the sheepshead minnow

Poster Number

20

Lead Author Major

Biological Sciences, Geological and Environmental Sciences

Format

Poster Presentation

Faculty Mentor Name

Santiago Salinas

Faculty Mentor Department

Biological Sciences

Abstract/Artist Statement

It is widely believed that when individuals of a populations are exposed to novel or infrequent environments, variation in traits will be larger (i.e., when exposing fish to very warm temperature, the range of growth rates will be larger than that expressed under a common temperature). This cryptic variation may facilitate evolutionary adaptation, providing phenotypic variation on which selection can act. Expected climatic changes will likely expose some of this variation, and whether populations will adapt to new conditions will be determined by how much variation exists. Despite its relevance, there is a paucity of studies evaluating the extent of cryptic variation. We exposed 15 families of sheepshead minnows, Cyprinodon variegatus, to frequent and rare temperatures to evaluate hidden phenotypic variation in growth. Individuals were grown at 29, 33, 37, and 41°C after hatch and measured at 30 days old. These temperatures were chosen based on in situ measurements of water temperature from the site the fish were collected (Charleston, South Carolina). Unexpectedly, no increase in phenotypic variation was found at rare temperatures. Ranges of growth were 0.28-0.56 mm d-1 (29°C), 0.48-0.74 mm d-1 (33°C), and 0.36-0.52 mm d-1 (37°C). Fish at 41°C suffered heavy mortality, with only 5 individuals surviving to the end of the experiment. These results appear to contradict the expectation that more phenotypic variation will emerge when a population is exposed to rare environments. We discuss how this finding could impact evolution under novel conditions.

Location

DeRosa University Center, Ballroom

Start Date

25-4-2015 10:00 AM

End Date

25-4-2015 12:00 PM

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Apr 25th, 10:00 AM Apr 25th, 12:00 PM

Absence of cryptic variation in response to elevated temperatures in the sheepshead minnow

DeRosa University Center, Ballroom

It is widely believed that when individuals of a populations are exposed to novel or infrequent environments, variation in traits will be larger (i.e., when exposing fish to very warm temperature, the range of growth rates will be larger than that expressed under a common temperature). This cryptic variation may facilitate evolutionary adaptation, providing phenotypic variation on which selection can act. Expected climatic changes will likely expose some of this variation, and whether populations will adapt to new conditions will be determined by how much variation exists. Despite its relevance, there is a paucity of studies evaluating the extent of cryptic variation. We exposed 15 families of sheepshead minnows, Cyprinodon variegatus, to frequent and rare temperatures to evaluate hidden phenotypic variation in growth. Individuals were grown at 29, 33, 37, and 41°C after hatch and measured at 30 days old. These temperatures were chosen based on in situ measurements of water temperature from the site the fish were collected (Charleston, South Carolina). Unexpectedly, no increase in phenotypic variation was found at rare temperatures. Ranges of growth were 0.28-0.56 mm d-1 (29°C), 0.48-0.74 mm d-1 (33°C), and 0.36-0.52 mm d-1 (37°C). Fish at 41°C suffered heavy mortality, with only 5 individuals surviving to the end of the experiment. These results appear to contradict the expectation that more phenotypic variation will emerge when a population is exposed to rare environments. We discuss how this finding could impact evolution under novel conditions.