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  4. EXPERIMENTAL STUDIES OF ADAPTATION IN CLARKIA XANTIANA. I. SOURCES OF TRAIT VARIATION ACROSS A SUBSPECIES BORDER

EXPERIMENTAL STUDIES OF ADAPTATION IN CLARKIA XANTIANA. I. SOURCES OF TRAIT VARIATION ACROSS A SUBSPECIES BORDER

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We report fndings of reciprocal transplant experiments intended to tease apart the roles of differentiation and plasticity in producing phenotypic variation across a geographic border between two plant subspecies. Clarkia xantiana ssp. xantiana and C. xantiana ssp. parvifora are California-endemic annuals that replace each other along a westG??east gradient of declining precipitation.
creator Eckhart, V. M. (Faculty/Staff)
creator Geber, Monica A.
creator McGuire, Christopher M.
Title Experimental Studies of Adaptation in Clarkia Xantiana. I. Sources of Trait Variation Across a Subspecies Border
supporting host Grinnell College. Biology
Index Date 2004
Publisher Grinnell College
Genre Essays
Digital Origin reformatted digital
Extent 12 pages
Media Type application/pdf
note Both genetic differentiation and phenotypic plasticity might be expected to affect the location of geographic range limits. Co-gradient variation (CoGV), plasticity that is congruent with genetic differentiation, may enhance performance at range margins, whereas its opposite, counter-gradient variation (CnGV) may hinder performance. Here we report fndings of reciprocal transplant experiments intended to tease apart the roles of differentiation and plasticity in producing phenotypic variation across a geographic border between two plant subspecies. Clarkia xantiana ssp. xantiana and C. xantiana ssp. parvifora are California-endemic annuals that replace each other along a westG??east gradient of declining precipitation. We analyzed variation in foral traits, phenological traits, and vegetative morphological and developmental traits by sowing seeds of 18 populations (six of ssp. xantiana and 12 of ssp. parvifora)at three sites (one in each subspeciesG?? exclusive range and one in the subspeciesG?? contact zone), in two growing seasons (an exceptionally wet El Nin??o winter and a much drier La Nin??a winter). Signifcant genetic differences between subspecies appeared in 11 of 12 traits, and differences were of the same sign as in nature. These fndings are consistent with the hypothesis that selection is responsible for subspecies differences. Geographic variation within subspecies over part of the spatial gradient mirrored between-subspecies differences present at a larger scale. All traits showed signifcant plasticity in response to spatial and temporal environmental variation. Plasticity patterns ranged from spatial and temporal CoGV (e.g., in node of frst fower), to spatial CnGV (e.g., in fowering time), to patterns that were neither CoGV nor CnGV (the majority of traits). Instances of CoGV may refect adaptive plasticity and may serve to increase performance under year-to-year environmental variation and at sites near the subspecies border. However, the presence of spatial CnGV in some critical traits suggests that subspecies ranges may also be constrained by patterns of plasticity.
citation/reference Eckhart, V. M., Geber, M. A., & McGuire, C. M. (2004). Experimental studies of adaptation in Clarkia xantiana. I. Sources of trait variation across a subspecies border. Evolution, 58(1), 59-70.
Language English
Topic Habitat
Topic Phenotypic plasticity
Topic Plants
Topic Adaptation
Geographic California
Keyword species borders
Keyword co-gradient variation
Keyword counter-gradient variation
Keyword geographic range limits
Keyword geographic variation
Keyword reciprocal transplant
Classification QK
Related Item Faculty Scholarship
Related Item Scholarship at Grinnell
Related Item Digital Grinnell
Identifier (hdl) http://hdl.handle.net/11084/26666
Identifier (u1) eckhart
Identifier (u2) BIO
Identifier (local) grinnell:26666
Access Condition Copyright to this work is held by the author(s), in accordance with United States copyright law (USC 17). Readers of this work have certain rights as defined by the law, including but not limited to fair use (17 USC 107 et seq.).
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