DOI: 10.5061/dryad.0k6djh9xx
title: Using ecological context to interpret spatiotemporal variation in natural selection

description: Spatiotemporal variation in natural selection is expected, but difficult
 to estimate. Pollinator-mediated selection on floral traits provides a
 good system for understanding and linking variation in selection to
 differences in ecological context. We studied pollinator-mediated
 selection in five populations of Dalechampia scandens (Euphorbiaceae) in
 Costa Rica and Mexico. Using a nonlinear path-analytical approach, we
 assessed several functional components of selection, and linked variation
 in pollinator-mediated selection across time and space to variation in
 pollinator assemblages. After correcting for estimation error, we detected
 moderate variation in net selection on two of four blossom traits. Both
 the opportunity for selection and the mean strength of selection decreased
 with increasing reliability of cross-pollination. Selection for pollinator
 attraction was consistently positive and stronger on advertisement than
 reward traits. Selection on traits affecting pollen transfer from the
 pollinator to the stigmas was strong only when there was a mismatch
 between pollinator and blossom size under unreliable cross-pollination.
 These results illustrate how consideration of trait function and
 ecological context can facilitate both the detection and the causal
 understanding of spatiotemporal variation in natural selection.
description: We studied phenotypic
 selection on the blossom traits in five populations, three in Costa Rica
 (Palo Verde, Puente la Amistad and Horizontes) and two in Mexico (La
 Mancha and Puerto Morelos). Both Mexican populations and one Costa Rican
 population were studied in two consecutive years. The data from the La
 Mancha population in 2007 were analyzed by Pérez-Barrales et al. (2013).
 In each population, we marked distinct patches of one to several
 intertwined individuals. Plants flower for an extended period, and we
 selected multiple blossoms per patch as they came into flower.
 We followed
 each focal blossom throughout the female phase and for the first day of
 the bisexual phase. Each day, we recorded the number of pollen grains on
 the three stigmas with the aid of a LED light and a 10× hand lens, and
 whether resin had been collected. On the first day of the bisexual phase,
 when the first male flower was open, we counted pollen on the stigmas one
 last time, and measured gland-stigma distance (GSD), anther-stigma
 distance (ASD), gland area (GA), and upper bract area (UBA). All distance
 traits were measured in <i>mm</i> using digital calipers. For
 the Costa Rican populations, we also measured the height of the blossom
 above the ground. After completing the measurements, we marked the
 blossoms with a small tag tied around the peduncle. We collected the
 marked blossoms 3-4 weeks later and recorded the number of seeds set (seed
 set).  
description: Description of the column
 names in the datafile: UBA = upper-bract area, units in
 <i>mm</i> GA = gland area, units in
 <i>mm</i> GSD = gland-stigma distance,
 units in <i>mm</i> GAD = gland-anther distance,
 units in <i>mm</i> ASD = anther-stigma distance,
 units in <i>mm</i> GW = gland width, units in
 <i>mm</i> GHl = gland height measured on
 the left side of the gland, units in <i>mm</i> GHr = gland height measured on
 the right side of the gland, units in <i>mm</i>
 UBL = upper bract length,
 units in <i>mm</i> UBW = upper bract width, units in
 <i>mm</i> pop = population year = year of sampling
 ID = order in which
 measurements were made date = date of measurement
 (yr-mth-day) patch = patch ID Blossom = blossom number within
 the patch stage =
 how many male flowers were open during measurement (M1 = one male flower
 open) pollenfem =
 pollen load counted on the stigma during the female phase polltotal/pollen = pollen load
 counted on the stigma during the first day of the bisexual phase
 pollenmale = pollentot –
 pollenfem resin =
 whether or not (0 or 1) resin has been removed from the gland
 seeds_GH = seeds that can
 be sown seeds_undeveloped = smaller pale
 seeds that were collected before fully developed seeds_pred = seeds with signs of
 predation total_seeds = seeds_GH +
 seeds_undeveloped + seeds_pred   Comments: Not all variables mentioned above
 appear in all datafiles. For logistical
 reasons we could not collect seeds at the Puerto Morelos
 site.