Premium
Divergence in pollen performance between Clarkia sister species with contrasting mating systems supports predictions of sexual selection
Author(s) -
Mazer Susan J.,
Hendrickson Brandon T.,
Chellew Joseph P.,
Kim Lynn J.,
Liu Jasen W.,
Shu Jasper,
Sharma Manju V.
Publication year - 2018
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/evo.13429
Subject(s) - biology , outcrossing , pollen , sexual selection , pollination , mating system , selfing , pollen tube , zoology , population , botany , mating , ecology , demography , sociology
Animal taxa that differ in the intensity of sperm competition often differ in sperm production or swimming speed, arguably due to sexual selection on postcopulatory male traits affecting siring success. In plants, closely related self‐ and cross‐pollinated taxa similarly differ in the opportunity for sexual selection among male gametophytes after pollination, so traits such as the proportion of pollen on the stigma that rapidly enters the style and mean pollen tube growth rate (PTGR) are predicted to diverge between them. To date, no studies have tested this prediction in multiple plant populations under uniform conditions. We tested for differences in pollen performance in greenhouse‐raised populations of two Clarkia sister species: the predominantly outcrossing C. unguiculata and the facultatively self‐pollinating C. exilis . Within populations of each taxon, groups of individuals were reciprocally pollinated ( n = 1153 pollinations) and their styles examined four hours later. We tested for the effects of species, population, pollen type (self vs. outcross), the number of competing pollen grains, and temperature on pollen performance. Clarkia unguiculata exhibited higher mean PTGR than C. exilis ; pollen type had no effect on performance in either taxon. The difference between these species in PTGR is consistent with predictions of sexual selection theory.