03015nas a2200313   4500008004100000245011000041210006900151260001200220300001400232490000700246520215300253653001502406653002102421653001602442653001402458653001402472653001102486653001602497653002102513653001602534653001502550653001202565653001102577653001402588100001902602700001702621700001902638856004402657       2000                        eng d00aWhat governs protein content of pollen: Pollinator preferences, pollen-pistil interactions, or phylogeny?0 aWhat governs protein content of pollen Pollinator preferences po  c2000///  a617 - 6430 v703 aPollen ranges from 2.5% to 61% protein content. Most pollen proteins are likely to be enzymes that function during pollen tube growth and subsequent fertilization, but the vast range of protein quantity may not reflect only pollen-pistil interactions. Because numerous vertebrate and invertebrate floral visitors consume pollen for protein, protein content may influence floral host choice. Additionally, many floral visitors pollinate their host plants. If protein content influences pollinator visitation, then pollinators are hypothesized to select for increased protein content of host plants. We analyzed or gleaned from the literature crude pollen protein concentrations of 377 plant species from 93 plant families. Using this database, we compared pollen protein concentration with (1) pollination mode, (2) pollen collection by bees, and (3) distance from stigma to ovule, after accounting for phylogeny through paired phylogenetic comparisons and a nested ANOVA including taxonomic rank. We found that pollen protein concentrations were highly conserved within plant genera, families, and divisions. We found that bees did not collect pollen that was unusually rich in protein, whether they pollinated or merely robbed their host plant. Plant species with vibratile pollination systems, which require visitation by pollen-collecting bees in order to transfer pollen, tended to have very protein-rich pollen, but it was not clear whether this was due to plant enhancement of pollinator rewards or to the possession of very small pollen grains. We found that zoophilous species were not statistically richer in pollen protein than anemophilous species after accounting for phylogeny, although the three most species-rich anemophilous clades surveyed were generally poor in protein. Plant genera hosting specialist pollen-collecting bees did not have particularly protein-rich pollen. Both mass of protein per pollen grain and pollen grain volume were correlated with stigma-ovule distance. We suggest that the need for growing pollen tubes probably plays a more important role in determining pollen protein content than rewarding pollinators10aANEMOPHILY10aBUZZ POLLINATION10aCOEVOLUTION10aEVOLUTION10aPHYLOGENY10aPOLLEN10aPOLLEN TUBE10aPOLLEN-CHEMISTRY10aPOLLINATION10aPOLLINATOR10aPROTEIN10aSTIGMA10aVARIATION1 aRoulston, T.H.1 aCane, J., H.1 aBuchmann, S.L.  uhttps://apoidea.myspecies.info/node/13501921nas a2200301   4500008004100000245006100041210006100102260001200163300001400175490000800189520115600197653001201353653000901365653002201374653000901396653001401405653001601419653001401435653001101449653002101460653002101481653001501502653001201517653001001529100001901539700001701558856004401575       2000                        eng d00aPollen nutritional content and digestibility for animals0 aPollen nutritional content and digestibility for animals  c2000///  a187 - 2090 v2223 aThis paper reviews the literature concerning digestion and nutrient content of pollen. Four topics are addressed in detail: 1) The mechanism of pollen digestion by animals; 2) The efficiency of mechanical and digestive removal of pollen content by various animals: 3) Range and taxonomic distribution of pollen nutrients, and 4) Adaptive hypotheses proposed to associate pollen chemistry with pollinator reward. Studies on the mechanism(s) of pollen digestion remain inconclusive, but suggest that differences in digestibility among pollen types may reflect differences in pollen wall porosity, thickness, and composition. Although hummingbirds reportedly digest pollen very poorly, most animals studied, including those that do not regularly consume pollen, can digest 50-100% of ingested grains. Overlooked and recent research of pollen protein content shows that pollen grains may contain over 60% protein, double the amount cited in some studies of pollen-feeding animals. Adaptive hypotheses that associate pollen starch and pollen caloric content with pollinator reward remain unsubstantiated when critically viewed through the lens of phylogeny10aApoidea10aBATS10aBEHAVIOR-FORAGING10aBIRD10aDIGESTION10aHUMMINGBIRD10aPHYLOGENY10aPOLLEN10aPOLLEN- ANALYSIS10aPOLLEN-CHEMISTRY10aPOLLINATOR10aPROTEIN10aSUGAR1 aRoulston, T.H.1 aCane, J., H.  uhttps://apoidea.myspecies.info/node/132