DOI: 10.5061/dryad.7pvmcvdqq
title: Geographic patterns in pollen production in Euphorbia tithymaloides

description: In this study We examine investment in male function in the context of
 geography and floral morphology in the plant ring species Euphorbia
 tithymaloides, which colonized the Caribbean from Mexico/Guatemala along
 two fronts that roughly correspond to the Greater and the Lesser Antilles
 and that meet in the vicinity of the Anegada Passage. Our results on
 investment in pollen relative to ovule production are consistent with E.
 tithymaloides relying on pollinators for reproduction across its range in
 the Caribbean. We document a geographic pattern of reduction in anther
 number and pollen:ovule ratios in populations of E. tithymaloides towards
 the Anegada Passage, which is consistent with a possible geographic
 transition towards a mixed breeding system where selfing has increased
 importance in this area where its two expansion fronts meet. The reduction
 in pollen production is correlated with inflorescence morphology, which
 converges to relatively shorter cyathia towards the Anegada Passage along
 both fronts. We discuss alternative scenarios and potential drivers of the
 patterns we document. The linked datasets consist of: 1. Georeferenced
 pollen counts of Euphorbia tithymaloides. 2. Georeferenced measurements of
 cyathia of Euphorbia tithymaloides. 3. Images from where cyathial
 measurements were derived.
description: The cyathia used for this study were collected in the field
 (fixed in ethanol 70% or FAA) or sampled from herbarium
 specimens. POLLEN COUNTS 
 Individual cyathia were dissected to visualize the anthers. The
 number and state of anthers was recorded. One undehisced anther per
 cyathium was selected at random and transferred to an Eppendorf tube
 containing 10mL of distilled water, where it was kept at 4°C until further
 processing. Anthers were macerated within the tube using a micro pestle,
 and the contents transferred to a Marienfeld Neubauer counting chamber
 (Paul Marienfeld GmbH & Co. KG, Lauda-Ko ̈nigshofen, Germany) to
 be examined under the microscope (Velab Prime VE-T50). The number of
 pollen grains in each quadrant was recorded separately and then added
 together to get the number of pollen grains per anther for a given sample.
 To ensure repro- ducibility, the counting exercise was repeated three
 times for each anther and averaged. The number of
 pollen grains per cyathium was obtained by multiplying the number of
 pollen grains per anther by the number of anthers per cyathium.
 Ovule production in E. tithymaloides is fixed to three per
 cyathium, so that P:O ratios are a direct reflection of pollen production
 per cyathium. CYATHIUM
 MEASUREMENTS We contribute new cyathial
 measurements (length, height) for 56 cyathia representing nine populations
 (min 5 1; mean 5 6.22; max 5 12 cyathia per population). Images of cyathia
 were taken in the field with a scale, and measured in Geogebra v. 5
 (http:// www.geogebra.org). These new data were added to data from a
 previous study (Cacho et al. 2019) and together are part of an ongoing
 morphometric data collection for this system. 
 OCURRENCE DATA Our own collections
 and images were geo-referenced using GPS; for herbarium samples and images
 where GPS coordinates not available, georeferencing was performed using
 Google Earth tools.
description: FILE: cyathia_measurements_20191221.csv 
 Variable
 Definition 
 pop population identifier
 image image
 identifier length
 cyathium length 
 height cyathium height
 scale scale
 used mm
 scale in mm 
 cyathium_LvsH cyathium L / H
 cyLength.mm cyathium
 length in mm 
 cyHeight.mm cyathium height in
 mm 
   FILE:
 DAT_polenWcyathiaNcoordsPOP_STDvals_20200104_english.csv
 
 Variable Definition 
 population_ID
 population identifier 
 pop.country population.country
 decimal_latitude
 latitude in decimal degrees 
 decimal_longitude longitude in decimal
 degrees dist2AP
 distance to Anegada Passage (km) 
 front.code biogeographic front
 of Euphorbia tithymaloides: Greater Antilles (GA), Lesser Antilles (GA),
 origin (OR) 
 geog.place geography: Greater Antilles
 (GA), Lesser Antilles (GA), Mainland (OR) 
 front.order populations ranked
 by order within front 
 country country 
 region insular,
 continental kind
 wild, cultivated 
 N.pollenXanther.pop n for pollen per
 anthers by population 
 mean.pollenXanther.pop mean of pollen
 grains per anther by population 
 mean.anthersXcyathium.pop mean of anthers
 per cyathium by population 
 mean.pollenXccyathium.pop mean of pollen
 grains per cyathium by population 
 POratio.pop mean pollen:ovule ratio by
 population 
 sd.pollenXanther.pop standard deviation of
 pollen grains per anther by population 
 sd.anthersXcythium.pop standard deviation
 of anthers per cyathium by population 
 sd.pollenXcythium.pop standard deviation of
 pollen grains per cyathium by population 
 sd.POratio.pop standard deviation
 pollen:ovule ratio by population 
 log.pollenXanther.pop log transformed mean
 of pollen grains per anther by population 
 log.anthersXcythium.pop log
 transformed mean of anthers per cyathium by population
 log.pollenXcythium.pop
 log transformed mean of pollen grains per cyathium by
 population 
 log.POratio.pop log transformed mean
 pollen:ovule ratio by population 
 sd.log.pollenXanther.pop log transformed
 standard deviation of pollen grains per anther by population
 sd.log.anthersXcythium.pop
 log transformed standard deviation of anthers per cyathium by
 population 
 sd.log.pollenXcythium.pop log transformed
 standard deviation of pollen grains per cyathium by population
 sd.log.POratio.pop
 log transformed standard deviation pollen:ovule ratio by
 population 
 N.cyLength n of cyathium length
 measurements 
 N.cyHeight n of cyathium height
 measurements 
 N.cyRatio n of cyathium ratio
 measurements 
 mean.cyLength population mean of cyathium
 length 
 mean.cyHeight population mean of
 height mean.cyRatio
 population mean of cyathium ratio 
 stdev.cyLength standard
 deviation of cyathium length by population 
 stdev.cyHeight standard
 deviation of cyathium height by population 
 pollenXanther.popSTD
 standardized mean of pollen grains per anther by population
 (mean.pollenXcyathium.pop -
 mean(mean.pollenXcythium.pop))/(sd(mean.pollenXcythium.pop))
 anthersXcythium.popSTD standardized mean of anthers per cyathium by population  (mean.anthersXcythium.pop - mean(mean.anthersXcythium.pop))/(sd(mean.anthersXcythium.pop)) pollenXcythium.popSTD standardized mean of pollen grains per cyathium by population (mean.pollenXcythium.pop - mean(mean.pollenXcythium.pop))/(sd(mean.pollenXcythium.pop)) colramp color ramp used for map