Diversity Patterns Of Lauraceae And Their Environmental Driving Factors

The Lauraceae are one of the primitive families of angiosperms,belong to the order Laurales of the Magnoliids.The family contains over 3500 species that are classified in nine tribal clades.Many species of the family have high economic value,i.e.delicious fruits,excellent timber,important spices,and common garden trees.The family has a pantropical distribution,many species are dominating the tropical and subtropical forests,and ecologically important in maintaining the tropical and subtropical forest ecosystem.However,it remains poorly known about the species diversity pattern and its underlying environmental factors.This study: 1)surveyed the literatures(e.g.Floras,monographs,revisional works,published papers),authoritative species databases(e.g.POWO,WFO,Species 2000),and global herbarium databases(e.g.GBIF and CVH),and compiled a new species catalogue of the family;2)studied the species richness patterns of the family;and 3)investigated the contribution of environmental factors to the species richness pattern of the family at different levels(global,continental and representative islands).The main results are as follows:1.A new species catalogue of the Lauraceae(1)The new catalogue contains 59 genera and 3591 species,and 9809 unique distribution records.(2)At the tribal(major clades)level,the Hypodaphnideae contain 1 genus and 1 species,the Cryptocaryeae contain 12 genera and 858 species,the Cassytheae contain 1 genus and 29 species,the Caryodaphnopsideae contain 1 genus and 17 species,the Neocinnamomeae contain1 genus and 8 species,the Mezilaurus groupcontains 5 genera and 36 species,the Perseeae contain 8 genera and 481 species,the Cinnamomeae contain 22 genera and 1355 species,and the Laureae contains 8 genera and 806 species.(3)At the genus level,the large genera with more than 100 species(include Ocotea,Cryptocarya,Cinnamomum,Beilschmiedia,Litsea,and Machilus,etc.)contain 2742 species,accounting for 76.4% of all species of Lauraceae.The remaining genera are oligo-or monospecific,including Eusideroxylon,Hexapora,Hypodaphnis,Iteadaphne,Paraia,Parasassafras,Phyllostemonodaphne,Potoxylon and Sinopora,accounting for only 0.2% of all Lauraceae species.2.Species richness patterns of the Lauraceae(1)The family Lauraceae is mainly distributed in tropical Asia(32 genera and 1772species)and tropical America(33 genera and 1247 species).(2)Among the 9 tribal clades,four clades possess wide distribution ranges.The diversity center of the Cryptocaryeae is mainly located in tropical Asia and Madagascar in Africa;the diversity center of the Perseeae is in tropical Asia;the diversity center of the Cinnamomeae is in tropical America;and the diversity center of the Laureae is in tropical Asia.The rest of the clades are narrowly distributed.The Hypodaphnideae are only distributed in the central and western regions of Africa;the Caryodaphnopsideae are disjunctly distributed in South America and Southeast Asia;the Neocinnamomeae are distributed in southern China,Indo-China Peninsula,and Sumatra island of Indonesia;and the Mezilaurus Group is restricted to the Amazon basin of South America.Though widely distributed,the Cassytheae have the high species richness only in southwestern Australia.(3)Among the continents,the diversity of Lauraceaee in tropical Asia is relatively scattered,with a few centers having high species diversity,whereas in tropical America species of the family are mainly concentrated in the north-central Andes.Tropical Asia and Tropical America show marked differences in spatial distribution of species richness.(4)Among the representative islands,the species of Lauraceae in Madagascar are mainly distributed along the eastern coast,those in Borneo are mainly distributed in the northeastern region,and those in New Guinea are mainly distributed in the southeastern region.2.Driving environmental factors of species diversity of the Lauraceae(1)The global richness of Lauraceae species is negatively related to the topsoil p H(T＿PH)and the mean diurnal range(bio2),but positively related to the precipitation of warmest quarter(bio18)and the range of annual precipitation(MAPR).(2)In tropical Asia,the main drivers of species richness include the potential evapotraspiration(PET)and the mean annual temperature difference(MATR),while in tropical America,the main drivers include the temperature seasonality(bio4)and the bio18.(3)The two major factors impacting to species richness of the Lauraceae in Madagascar are the coldest seasonal mean temperature(bio11)and temperature annual range(bio7),while in Borneo they are the min temperature of the coldest month(bio6)and annual precipitation(bio12),and in New Guinea they are the bio12 and the mean temperature of warmest quarter(bio10).This study compiled a new catalogue of species of the family Lauraceae.For the first time,we investigated the diversity of the main clades(tribes)and genera of Lauraceae,explored the diversity patterns of Lauraceae species at different levels(viz.global,continental and representative islands),and studied the environmental factors driving the distribution patterns.It is concluded that species richness of Lauraceae(except the parasitic herbaceous Cassytha)basically shows latitudinal gradients,and the environmental heterogeneity is important in shaping the modern species diversity patterns of the Lauraceae.The result also indicates that the environmental factors impacting on the diversity patterns of the Lauraceae vary among scales and regions.This study lays an important foundation for further biogeographic studies and biological conservation of the family Lauraceae.