Conservation Biology Of Three Phalaenopsis (Orchidaceae) Species In Hainan Island

Phalaenopsis cultivated species has a very high ornamental value and high status in the world orchid trade.However,because wild germplasm resources are seriously affected by human activities,piracy and climate change,the Phalaenopsis population is seriously degraded and extremely endangered.In this study,three Phalaenopsis species distributed in Hainan Island,P.deliciosa,P.hainanensis and P.pulcherrima,were used as research materials.I studied the community structure and epiphytic habits,endophytic microorganisms,and reproductive biology of P.deliciosa and P.hainanensis,the effects of flower colour and sympatric reward plants on the reproductive success,and population genetics and mating system of P.pulcherrima.These results provide basic data and theoretical support for the conservation for three Phalaenopsis species.The main research results are as follows:1 Phalaenopsis deliciosa(1)Community structure and epiphytic habits: The vascular plants in the community of P.deliciosa were showed the typical tropical attributes and mainly belonged to Trop.Asia:India-Malasia and Pantropic;there were 41 epiphytic hosts species for P.deliciosa,which had epigenetic preference for Streblus taxoides and S.ilicifolius.In the horizontal distribution,the individuals of three P.deliciosa populations were aggregative distribution at small scales.In vertical distribution,the individuals of three P.deliciosa populations were distributed below 5 m and concentrated on the height scale of 1–1.9 m.(2)Internal biological microorganisms: 38 strains of representative endophytic fungi were isolated from the roots of P.deliciosa;strains were identified as 5 OTUs and classified into 5genera,and the dominant genus were Lasiodiplodia and Aspergillus;To 54 representative strains of endophytic bacteria,17 OTUs were identified and classified into 12 genera,and the dominant genus were Bacillus and Enterobacter.(3)Flowering phenology:Emasculated(3.28 d)and hand-pollination(8.98 h)treatments of a single flowering duration were significantly lower than that of open-pollination(6.93 d).At the individual and population levels,the flowering phenology was affected by climatic factors.In 2015,the flowering period of P.deliciosa started earlier and ended later;the relative flowering intensity of the individual level was lower,and the main distribution frequency was10%–40%;the fruit setting rate had a significant positive correlation with flowering numbers and flowering duration(P < 0.01).(4)Pollination mechanism: P.deliciosa employed a generalized food-deceptive pollination system with Nomia sp.as pollinator.(5)Breeding system: Automatic pollination and apomixis did not occur in P.deliciosa.Fruitset of self-pollination treatment(60.00%)and the outcrossing treatment(65.00%)were not significant difference(P > 0.05),but they were significant higher than that of the natural treatment(7.14% in 2014 and 4.24% in 2015).(6)Pollinia migration: Pollinia migration rate(removal rate was 16.43%,deposition rate was 7.30%)in 2014 was higher than that in2015(removal rate was 8.48%,deposition rate was 4.24%),and the pollinia migration rate of the SD population was relatively low in two years than that of other two populations.2 Phalaenopsis hainanensisCommunity structure and epiphytic habits: The vascular plants in the community of P.hainanensis were showed the typical tropical attributes and mainly belonged to Trop.Asia:India-Malasia and Pantropic;There were 17 epiphytic hosts species for P.hainanensis,which had epigenetic preference for Streblus ilicifolius and Mallotus yunnanensis.In the horizontal distribution,the individuals in four representative sample plots of P.hainanensis were aggregation distribution at small scale.In vertical distribution,the individuals of P.hainanensis were distributed below 4 m.The distribution number of individuals was no significant in different height scales but concentrated on the height scales of 0–0.9 m and2–2.9 m.(2)Internal biological microorganisms: 56 strains of representative endophytic fungi were isolated from the roots of P.hainanensis;Strains were identified in 9 OTUs and classified into 6 genera,and the dominant genus were Xylaria and Fusarium;To 65 representative strains of endophytic bacteria,19 OTUs were identified and classified into14 genera,and the dominant genus were Bacillus and Enterobacter.(3)Flowering phenology: Emasculated(6.00 d)and hand-pollination(10.57 h)treatments of a single flowering duration were significantly lower than that of open-pollination(12.40 d).At the individual and population levels,the flowering phenology was affected by climatic factors.In 2015,the flowering period of P.hainanensis started earlier and ended later;the relative flowering intensity of the individual level was lower,and the main distribution frequency was 20%;the correlation analysis between individual level phenological index and reproductive success found that the fruit setting rate had a significant positive correlation with flowering numbers and flowering duration(P < 0.01).(4)Pollination mechanism: P.hainanensis employed a generalized food-deceptive pollination system with Megachile lanata as pollinator.(5)Breeding system: Automatic pollination and apomixes did not occur in P.hainanensis.Fruit set of self-pollination treatment(26.27%)was significant lower than that of outcrossing treatment(100.00%)(P < 0.01),indicated self-incompatibility or inbreeding depression in P.hainanensis.Hand-pollinated treatments were significantly higher than that of the natural treatment(6.52% in 2014 and 5.32% in2015).(6)Pollinia migration: Pollinia migration rate(removal rate was 16.00%,deposition rate was 6.67%)in 2014 was higher than that in 2015(removal rate was 15.96%,deposition rate was 5.32%),and the pollinia migration rate of the YZC population was relatively lower in two years than that of EXL population.3 Phalaenopsis pulcherrima(1)The various floral colours of P.pulcherrima were divided into two colour types,pink and purple,in the visual colour space of the insect;these two flower phenotypes were similar to the sympatric rewarding plant species,Helicteres angustifolia and Oldenlandia consanguinea,respectively,indicating a double-mimicry in flower colours.(2)The pink flower phenotype was the dominant phenotype in the population;However,the male and female reproductive success of the two phenotypes did not have significant difference among populations or between years,indicating that there was no negative frequency dependent selection between the flower phenotypes of P.pulcherrima.(3)H.angustifolia and O.consanguinea had significant positive effects on the male and female reproductive success of P.pulcherrima,indicating that the sympatric rewarding plants had a magnet species effect to P.pulcherrima.(4)P.pulcherrima had lating self-incompatibility in per-zygotic stage.Individuals in P.pulcherrima populations showed an aggregative distribution on small scales and fine-spatial genetic structure.Seed dispersal was more restricted than pollen dispersal.(6)P.pulcherrima populations had a high genetic diversity and low genetic differentiation among populations.The population of P.pulcherrima significantly deviated from the balance of Hardy-Weinberg and the heterozygote was excessive.(7)P.pulcherrima belonged to the outcrossing mating system,and the F1 seedlings from the eight capsules were all resulted from outcrossing mating,and each capsule had only one pollen donor.P.pulcherrima showed a long pollen-flow distance,with an average of 272.68 m.4 Comparative analysis of three Phalaenopsis species(1)Community structure: The vascular plants in the community were showed the typical tropical attributes.(2)Spatial distribution: Individuals aggregated at small scales,which might be influenced by the distribution of fungi at the local scale.(3)Endophytic microorganisms: The species of endophytic fungi were different,which may be affected by orchid’s living habits and habitat.Endophytic bacteria of three Phalaenopsis were dominated by Bacillus.(4)Flowering phenology: Pollination and emasculation treatment can significantly reduce the single flowering period,with the typical post-pollination development of orchids after pollination or emasculation.The flowering period of three Phalaenopsis overlaped in the range of May to November,and the peak of flowering occurred between July and August.The fruit set of P.deliciosa and P.hainanensis both had a significant positive correlation with the flowering duration and flowering number,indicating a possible type of Remove Habitat Effect;On the contrary,the fruit set of P.pulcherrima had a significant negative correlation with the duration of flowering and the flowering number,causing by Magnet Species Effect.(5)Pollination mechanism: The three Phalaenopsis all employed a generalized food-deception pollination system with bees as pollinators but different species,leading to the reproductive isolation in the wild.(6)Breeding system: The fruit set of hand-pollination treatments was significantly higher than that of open-pollination treatment,indicating that there were serious pollen restrictions.There was no automatic pollination and apomixes in three Phalaenopsis;P.hainanensis and P.pulcherrima had self incompatibility or inbreeding phenomenon.The three Phalanopsis had interspecific hybridization compatibility.(7)Pollen migration: Pollen migration rate was relatively low in the populations which affected by human disturbance and natural disasters.In summary,for the conservation of the three Phalaenopsis,the habitat plant communities should be strengthened especially for epiphytic preference tree or sympatric rewarding plant species,and the pollinators should be also considered.The populations with human disturbance should be protected strengthenly,for example,in situ conservation and population monitoring should be carried out in the SD population of P.deliciosa;and ex situ conservation should be carried out in the YZC population of P.hainanensis.At the same time,the reintroduction and population reestablishing conservation strategies should be implemented to prevent the reduction of population reproductive fitness and population decline caused by natural disasters.