The Biological Characteristics And Relationship Analysis Of Rhizophora×lamarckii And Its Putative Parent Tree

Rhizophora×lamarckii is the putative hybrid of Rhizophora stylosa and Rhizophora apiculata Blume,Some characters are between its putative parent tree.In order to further clarify the biological characteristics and relationship of three mangrove plants,we choice the three magrove plants in Xinying Nature Reserve,Danzhou and Dadun Village in Lingshui.Analyze and compare biological characteristics(include flower morphological parameters?part organs of three mangrove plants ? stigma and pollen under electron microscope ?pollinators and flower visiting frequency ? breeding system).The relationship of three mangrove plants was further clarified by use two nuclear gene sequences(PAL1?DLDH)and a chloroplast gene sequence(atp B-rbc L spacer).The main results are as follows:1.Distribution of R.×lamarckii in Hainan islandThere are only 3 R.×lamarckii in Lingshui,1 new discovered in Wenchang,1 tree in qingmei harbor of Sanya(cut down),and a stable living group in Xinying Nature Reserve of Danzhou,about 20 trees.R.stylosa and R.apiculata are distributed in the above locations.2.Comparitionof biological characteristics of three spicies mangrove plants(1)Comparison of morphological features of three mangrove plantsR.×lamarckii is more like R.apiculata Blume in flower fruit features,while in other aspects such as morphological characteristics more inclined to R.stylosa.But its overall tree is larger than R.stylosa and R.apiculata.The leaves are relatively broad and squid are thick and strong.This is related to hybrid produces good traits.(2)Breeding systemPollenovule ratio(P/O): The total pollen amount of three species mangrove plants was larger,and the variation range was also large.Compare the amount of pollen of three species magrove trees in single flower: R.apiculata(7476,667 ±686,971.76)>R.×lamarckii(1461,667 ±86,784.84)> R.stylosa(555,000 ±87,444.56).There are 4 ovules in all three mangrove plants,Then the pollenovule ratio(P/O)was: R.apiculata(1869,167±171,742.75)>R.×lamarckii(365,417 ±21,696.21)> R.stylosa(138,750±21,861.14).According to breeding system criteria,the breeding system of R.apiculata?R.×lamarckii and R.stylosa are obligate heterosex.Stigma receptivity: The three magrove plants have the same Stigma receptivity period.The stigma of flower show is the most powerful,followed by the open period,and flower bud is almost nontransferable.Pollen vigor: Three mangrove plants have a long flowering period,pollen viability is lower in the bud period.We selected bud micro exhibition period to examinate pollen vitality,R.×lamarckii has the lowest pollen viability only 10.24%,R.stylosa and R.apiculata were33.85% and 10.30% respectively.(3)Major pollinators and visiting freqencyThe main flower visitors of R.×lamarckii are Trigona?Vespidae?Pheidole megacephala(Fabricius)?Coleoptera and Acaridae,Trigona?Vespidae?Pheidole megacephala(Fabricius)are effective pollinators,they are participate in the pollination process,Coleoptera eat and suck the mesophyll and does not see them participate pollination process;The main flower visitors of R.stylosa are Trigona?Vespidae?Pheidole megacephala(Fabricius)?Coleoptera and Acaridae,all these insects participate in the pollination process;The main flower visitors of R.apiculata are Trigona?Vespidae ?Araneae ?Stinkbug and Mantodea,Trigona and Vespidae participate pollination process,are effective pollinators,Araneae ? Stinkbug and Mantodea eat and suck the mesophyll does not see them participate pollination process.Trigona may be the public pollinators of three species mangrove plants.In addition,a large number of mites were found in all three species of mangrove plants.The effects of mites on the pollination process and biological functions of three mangrove plants need to be further studied.Annual visit frequency of three magrove trees was lossom period was the highest,next is the early exhibition period,the lowest is the late flowering season.The peak of daily visit of R.stylosa and R.×lamarckii mainly on 12:00-14:00 and 16:00-18:00,R.apiculata mainly on12:00-16:00.3.The relationship of three mangrove plants(1)Analyze two nuclear genes to explicit the relationship of three species mangrove plantsSix out of eight R.×lamarckii samples PAL1 gene completely consistent with R.stylosa PAL1 gene,the length was 940 bp,the rest of two samples PAL1 gene quite the same as R.Apiculata samples PAL1 gene,the length was 939bp;Three out of eight R.×lamarckii samples DLDH gene completely consistent with R.stylosa DLDH gene,the length was 1208 bp,the rest of five samples DLDH gene quite the same as R.apiculata samples DLDH gene,the length was 1205 bp.The two nuclear gene sequences were either consistent with R.stylosa or R.apiculata,We suggest that R.stylosa and R.apiculata might be the parent trees of R.×lamarckii.(2)Analysis chloroplast gene of three mangrove plants to find who is the mother parent of R.×lamarckiiThe sequence length of chloroplast gene(atp B-rbc L spacer)of R.stylosa and R.×lamarckii was 827 bp,this sequences is exactly the same,no sequence variation.The length of chloroplast atp B-rbc L spacer sequence of R.apiculata was 811 bp,compared with R.stylosa and R.×lamarckii,there were 6 base mutations,a 30 bp and 1bp insertion and a 13 bp deletion.The R.apiculata overall sequence similarity with R.stylosa and R.×lamarckii was94.1%,which can be inferred that R.stylosa is the mother parent tree of R.×lamarckii.In conclusion,the three magrove plants are intertwined in distribution,public flower visitors and peak period of visiting flowers overlaps,which provide the possibility for the formation of R.×lamarckii.In addition,through morphological and molecular analysis,It was verified that the discovered species in Xinying Nature Reserve,Danzhou was the natural hybrid progeny of R.stylosa and R.apiculata,its mother parent tree was R.stylosa and male parent tree was R.apiculata.