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Differential selection on floral traits of Ipomopsis aggregata growing in contrasting environments
Author(s) -
Caruso Christina M.
Publication year - 2001
Publication title -
oikos
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.672
H-Index - 179
eISSN - 1600-0706
pISSN - 0030-1299
DOI - 10.1034/j.1600-0706.2001.940210.x
Subject(s) - biology , pollination , pollinator , pollen , botany , selection (genetic algorithm) , artificial intelligence , computer science
Interactions for pollination between co‐flowering plant species have been hypothesized to shape the evolution of their floral traits, but this hypothesis has rarely been tested. I tested the prediction that the presence of a co‐flowering plant species influences the strength and/or direction of pollinator‐mediated selection on floral traits. I measured phenotypic selection via female fitness on four floral traits of Ipomopsis aggregata in five populations. Three contained only conspecifics ( I only ) and two also contained the co‐flowering species Penstemon barbatus ( P + I ). Directional selection via fruits/plant on corolla length and width differed in both strength and direction between P + I and I only populations. On average, selection on corolla length and width (1) was stronger in P + I than I only populations and (2) was consistently negative in P + I populations, but consistently positive in I only populations. However, these differences in selection on I . aggregata between P + I and I only populations were not caused by interactions for pollination with P . barbatus . Although plants in P + I populations received approximately 31% less conspecific pollen/flower than plants in I only populations, this difference in pollination did not translate into differences in reproductive success, which indicates that P . barbatus and I . aggregata do not strongly compete for pollination. In addition, selection via fruits/plant and conspecific pollen deposited/flower was not congruent. For example, selection on corolla length via pollen/flower was uniformly positive and did not differ between P + I and I only populations. These data suggest that the presence of P . barbatus does influence selection on floral traits of I . aggregata , but not by influencing pollination. Instead, differences in selection between P + I and I only populations appear to be the result of post‐pollination modification of selection by a factor correlated with the presence of P . barbatus .