Urbanization affects plant flowering phenology and pollinator community:effects of water availability and land cover

Introduction:Climate change and urbanization have been shown to alter plant phenology.However,a mechanistic understanding of these changes in flowering phenology and associated pollinator communities is lacking.Thus,this study was designed to examine finer scale flowering phenological patterns and driving processes in an arid urban ecosystem.Specifically,we tested the effect of water availability and land cover type on the flowering phenology of brittlebush(Encelia farinosa)and investigated the arthropod pollinator community associated with brittlebush.Methods:The fieldwork was carried out as part of a larger community ecology experiment following a factorial nested design.We chose three land cover types,each of which had three replicates,resulting in a total of nine sites.For water availability manipulations,60 genetically different 5-gallon potted plants were placed on the ground within each site.Pan-trapping was used to collect potential pollinators.Results:Our results showed that water availability did not produce significant differences in flowering phenology.However,brittlebush planted in mesiscaped urban sites bloomed later,longer,and at a higher percentage than those planted in desert remnant sites and desert fringe sites.Furthermore,desert remnant sites were significantly lower in pollinator abundance than desert fringe sites.Pollinator richness varied over time in all land cover types.Conclusions:This study provides empirical evidence that land cover type,which is strongly correlated to temperature,is the primary cause for altered flowering phenology of brittlebush in the Phoenix area,although water availability may also be important.Moreover,land cover affects total abundance of bee pollinators.

Multiple lines of evidence supports the two varieties of Halenia elliptica(Gentianaceae)as two species

Delimiting species requires multiple sources of evidence.Here,we delimited two varieties of Halenia elliptica(Gentianaceae)using several lines of evidence,including morphological traits and mating system in a sympatric population,phylogenetic relationships based on nrITS and cpDNA(rpl16)data,and complete chloroplast genome sequences.Comparative analysis of 21 morphological traits clearly separates the two varieties of H.elliptica.Examination of the flowering process and pollination treatments indicate that H.elliptica var.grandiflora produces seeds via outcrossing,whereas H.elliptica var.elliptica produces seeds via mixed mating.Furthermore,hand-pollinated hybridization of the two varieties produced no seeds.Observations of pollinators showed that when bees began a pollination bout on H.elliptica var.grandiflora they preferred to continue pollinating this variety;however,when they began a pollination bout on H.elliptica var.elliptica,they showed no preference for either variety.Phylogenetic analysis confirmed the monophyly of H.elliptica,which was further divided into two monophyletic clades corresponding to the two varieties.A large number of variants from the chloroplast genomes reflected remarkable genetic dissimilarities between the two varieties of H.elliptica.We recommend that the two varieties of H.elliptica should be revised as two species(H.elliptica and H.grandiflora).Our findings indicate that H.elliptica varieties may have split into two separate species due to a shift in mating system,changes in flowering phenology and/or post-pollination reproductive isolation.

Phylogenetic and climatic constraints drive flowering phenological patterns in a subtropical nature reserve

Aims Exploring flowering patterns and detecting processes are essential when probing into the nature of reproductive traits during the life history and the interactions among different evolutionary clades.such patterns are believed to be influenced by many factors,but quantifying these impacts at the community-level remains poorly understood.Methods We investigated the flowering patterns based on long-term her-barium records in a given area from subtropical forest regions in southern China.We obtained 5258 herbarium voucher specimens collected from the Dinghushan National Nature reserve(DNNr)belonging to 166 families,943 genera and 2059 species and exam-ined the month when each species was flowering during the period 1920-2007.Important Findings The results showed that plants flowered sequentially almost through-out the whole year,showing the characteristics of subtropical evergreen broad-leaved forests.Flowering spectrums of the entire flora and the four life forms exhibited a clear unimodality that is probably typical of subtropical forest communities.Flowering pat-terns of the DNNr were positively correlated with mean rainfall,mean air temperature and mean sunshine duration.median flowering dates of the 38 large species-rich families ranged from early april to late august;25 families exhibited significant unimodal distribution patterns,whereas the remaining families were unclear or bimodal.median flowering dates of the 10 most species-rich genera ranged from middle may to later July.While the results are consist-ent with climatic factors playing a general role in flowering patterns,median flowering dates varied significantly among species-rich families and genera,suggesting that phylogenies could provide spe-cific constraints in subtropical forests.

Arbuscular mycorrhizal fungi differ in affecting the flowering of a host plant under two soil phosphorus conditions

Aims Studies have showed that arbuscular mycorrhizal fungi(AMF)can greatly promote the growth of host plants,but how AMF affect flow-ering phenology of host plants is not well known.Here,we con-ducted a pot experiment to test whether life cycle and flowering phenology traits of host plant Medicago truncatula Gaertn can be altered by AMF under low and high soil phosphorus(P)levels.Methods the experiment was conducted in a greenhouse at Zhejiang University in China(120°19′E,30°26′N)and had a completely ran-domized design with two factors:AMF treatments and soil P levels.Six AMF species(Acaulospora scrobiculata,As;Gigaspora marga-rita,Gma;Funneliformis geosporum,Fg;Rhizophagus intraradices,Ri;Funneliformis mosseae,Fmo and Glomus tortuosum,Gt.)were used,and two soil P levels(24.0 and 5.7 mg kg−1 Olsen-soluble P)were designed.the six AMF species were separately inoculated or in a mixture(Mix),and a non-AMF control(NAMF)was included.When plants began to flower,the number of flowers in each pot was recorded daily.During fruit ripening,the number of mature fruits was also recorded daily.After~4 months,the biomass,bio-mass P content and AMF colonization of host plant were measured.Correlation between root colonization and first flowering time,or P content and first flowering time was analyzed.Important Findings Under the low P level,first flowering time negatively correlated with root colonization and biomass P.Only host plants with AMF spe-cies As,Fg,Ri,or Mix were able to complete their life cycle within 112 days after sowing.And treatment with AMF species Fg,Gt,or As resulted in two periods of rapid flower production while other fungi treatments resulted in only one within 112 days after sowing.the cumulative number of flowers produced and biomass P content were highest with species Fg.Host biomass allocation significantly differed depending on the species of AMF.Under both soil P levels,the host plant tended to allocate more biomass to fruits in the Mix treatment than in the other treatments.these results indicated that the effects of AMF on host flowering phenology and biomass allocation differed depending on AMF species and soil P levels.