Island biogeography theory and the habitat heterogeneity jointly explain global patterns of Rhododendron diversity

Mountain biodiversity is of great importance to biogeography and ecology.However,it is unclear what ecological and evolutionary processes best explain the generation and maintenance of its high levels of species diversity.In this study,we determined which of six common hypotheses(e.g.,climate hypotheses,habitat heterogeneity hypothesis and island biogeography theory)best explain global patterns of species diversity in Rhododendron.We found that Rhododendron diversity patterns were most strongly explained by proxies of island biogeography theory(i.e.,mountain area)and habitat heterogeneity(i.e.,elevation range).When we examined other relationships important to island biogeography theory,we found that the planimetric area and the volume of mountains were positively correlated with the Rhododendron diversity,whereas the‘mountains-to-mainland’distance was negatively correlated with Rhododendron diversity and shared species.Our findings demonstrate that Rhododendron diversity can be explained by island biogeography theory and habitat heterogeneity,and mountains can be regarded as islands which supported island biogeography theory.

A generalized model of island biogeography

MacArthur and Wilson's equilibrium theory is one of the most influential theories in ecology.Although evolution on islands is to be important to island biodiversity,speciation has not been well integrated into island biogeography models.By incorporating speciation and factors influencing it into the MacArthur-Wilson model,we propose a generalized model unifying ecological and evolutionary processes and island features.Intra-island speciation may play an important role in both island species richness and endemism,and the contribution of speciation to local species diversity may eventually be greater than that of immigration under certain conditions.Those conditions are related to the per species speciation rate,per species extinction rate,and island features,and they are independent of immigration rate.The model predicts that large islands will have a high,though not the highest,proportional endemism when other parameters are fixed.Based on the generalized model,changes in species richness and endemism on an oceanic island over time were predicted to be similar to empirical observations.Our model provides an ideal starting point for re-evaluating the role of speciation and re-analyzing available data on island species diversity,especially those biased by the MacArthur-Wilson model.

Plumage assisted divergence in a vocally complex island endemic:The Dicrurus paradiseus species complex in Sri Lanka

Models of allopatric speciation within an island biogeographic framework suggest that the division of ancestral mainland populations leads to one or more allopatric island species predominantly through natural and sexual selection or genetic drift.Here we studied phenotypic divergence in a phylogenetic framework in the Dicrurus paradiseus allospecies complex in Sri Lanka,a continental island located in the Indian plate,to understand the complexity of phenotypic divergence on an island.Members of the genus Dicrurus are known as drongos and are conserved in morphology and plumage,but highly variable in vocalization due to vocal learning and mimicry.Two closely related drongos are found in Sri Lanka:the endemic D.lophorinus(or D.paradiseus lophorinus to many authors)found in the wet zone of the island and the widespread continental species D.paradiseus,which inhabits the dry zone.Sampling from all major populations,and voucher specimens from museums across their range in Sri Lanka,we examined phenotypic and genetic variation in this group.The phenotype showed two clusters:birds with a fish-like tail and erect crest(D.lophorinus),and birds with elongated tail streamers with backwardly curved crest(D.paradiseus).There was no significant difference in the vocal traits compared.The genetic variation was examined using two nuclear(Myo 2 and c-mos)and two mitochondrial(ND2 and Cytb)loci and the phylogenetic relationship was analyzed using the Bayesian inference coalescent-based species tree estimation method.The quantitative criteria for species delimitation provided a score sufficient to consider these two taxa as distinct species by considering measurements of body and plumage,acoustics,behaviour and distribution.The phylogeny supports distinct species status for the Sri Lanka Drongo(Dicrurus lophorinus)and that the D.lophorinus and D.paradiseus sister pair diverged since 1.35 mya.The variation in the crest and the tail plumage(components of phenotype)were the main contributors of the divergence,despite the similarity in general appearance and vocalization of the allopatric species.

An island biogeography model for beta diversity and endemism： The roles of speciation, extinction and dispersal

A community composition island biogeography model was developed to explain and predict two community patterns （beta diversity and endemism） with the consideration of speciation, extinction and dispersal processes. Results showed that rate of speciation is positively and linearly associated with beta diversity and endemism, that is, increasing species rates typically could increase the percentage of both endemism and beta diversity. The influences of immigration and extinction rates on beta diversity and endemism are nonlinear, but with numerical simulation, I could observe that increasing extinction rates would lead to decreasing percentage of endemism and beta diversity. The role of immigration rate is very similar to that of speciation rate, having a positive relationship with beta diversity and endemism. Finally, I found that beta diversity is closely related to the percentage of endemism. The slope of this positive relationship is determined jointly by different combinations of speciation, extinction and immigration rates.

Synergistic effects of Pleistocene geological and climatic events on complex phylogeographic history of widespread sympatric species of Megaloptera in East Asia

Unraveling the phylogeographic histories of species remains a key endeavor for comprehending the evolutionary processes contributing to the rich biodiversity and high endemism found in East Asia.In this study,we explored the phylogeographic patterns and demographic histories of three endemic fishfly and dobsonfly species(Neochauliodes formosanus,Protohermes costalis,and Neoneuromus orientalis)belonging to the holometabolan order Megaloptera.These species,which share a broad and largely overlapping distribution,were analyzed using comprehensive mitogenomic data.Our findings revealed a consistent influence of vicariance on the population isolation of Neoc.formosanus and P.costalis between Hainan,Taiwan,and the East Asian mainland during the early Pleistocene,potentially hindering subsequent colonization of the later diverged Neon.orientalis to these islands.Additionally,we unveiled the dual function of the major mountain ranges in East Asia,serving both as barriers and conduits,in shaping the population structure of all three species.Notably,we demonstrated that these co-distributed species originated from Southwest,Southern,and eastern Central China,respectively,then subsequently migrated along multi-directional routes,leading to their sympatric distribution on the East Asian mainland.Furthermore,our results highlighted the significance of Pleistocene land bridges along the eastern coast of East Asia in facilitating the dispersal of mountain-dwelling insects with low dispersal ability.Overall,this study provides novel insight into the synergistic impact of Pleistocene geological and climatic events in shaping the diversity and distribution of aquatic insects in East Asia.

Research Progress on the Theory of Delineation and Zoning of Nature Reserves in China and Discussion of Strategies

The construction of nature reserves plays an essential role in protecting natural resources and the ecological environment,especially the conservation of rare and endangered species,which also has a vital function in maintaining the ecological security of the national territory.China has built up a comprehensive network of nature reserves after waves of development,but there are still many problems with the management of nature reserves,such as the definition of boundaries,zoning theory,zoning methods,and legal protection.The definition of boundaries is a tool for effective management of nature reserves,but achieving scientific and effective boundary definition is a difficult problem for the construction and management of reserves.It is also a problem that must be solved to achieve sustainable development.This paper compared three fundamental theories of the conservation of species in nature reserves,namely island biogeography,metapopulation,and landscape ecology,from connotations,applications and advantages,and disadvantages,and discussed the progress of theoretical research to provide valuable references for the definition and planning of effective boundaries of nature reserves.

Prickly pairs: the proportion of spinescent species does not differ between islands and mainlands

Aims Organisms on islands are thought to escape biotic pressure and lose defensive capabilities.However,broadscale,evidence-based tests of this idea are rare.In this study,we asked:(i)whether the proportion of spinescent plant species differed between islands and mainlands and(ii)whether the proportion of spinescent species increased with increasing island area and with decreasing island distance to mainland.Methods We compiled species lists for 18 island–mainland pairs around Australia.We classified 1129 plant species as spinescent or nonspinescent using published species descriptions.Important Findings There was no significant difference between the proportion of spinescent species found on islands and on mainlands.Proportions of spinescent species were not significantly related to island area or distance to mainland.Our results suggest that spinescence is just as important to island plants as it is to mainland plants,even for plants inhabiting small or distal islands.This is unexpected,given prevailing thought and previous work on island–mainland comparisons.Our study demonstrates the importance of testing well-accepted yet untested ideas.