Ecogeographic Variation in the Morphology of Two Asian Wild Rice Species, Oryza nivara and Oryza rufipogon

Abstract

To search for variation patterns and diagnostic features between Asian wild rice species, several numerical methods were applied to phenotypic data obtained from 116 accessions representing sympatric populations of Oryza nivara and Oryza rufipogon from tropical continental Asia and O. rufipogon populations from insular Southeast Asia and Australasia. Ordination and cluster analyses separate O. rufipogon from O. nivara, indicating the presence of two sympatric morphological species occupying different ecological niches. Oryza nivara and O. rufipogon are morphologically more differentiated in South Asia than in mainland Southeast Asia, implying more recent divergence and/or more interspecific gene flow among sympatric populations in the latter region. Oryza nivara exhibits South and Southeast Asian phenotypes while the Australasian populations of O. rufipogon appear as distinct from the rest of the species. Seedling height, culm number, and diameter; leaf length and width; and anther length were significantly correlated to certain geoclimatic factors and displayed contrasting correlation directions for O. nivara and O. rufipogon, implying that the two species respond differently to geographic and climatic gradients. Diagnostic characters are provided to delineate the species morphologically. The results suggest the strong influence of ecology on species morphology, existence of geographic races within species and morphological divergence between O. nivara and O. rufipogon.

Population genetic structure of Oryza rufipogon and Oryza nivara: implications for the origin of O. nivara

“…; Zheng & Ge ; Banaticla‐Hilario et al . ). However, a few questions regarding habitat preference, the origin of O. nivara and the determining climate variables remain unclear.…”

“…,b; Banaticla‐Hilario et al . ,c). Zheng & Ge () was the first study that collected specieswide population samples for both O. rufipogon and Oryza nivara .…”

“…; Banaticla‐Hilario et al . ). In our previous study (Zheng & Ge ), we sequenced fragments of five nuclear and two chloroplast loci for these populations.…”

“…; Zheng & Ge ; Banaticla‐Hilario et al . ,b). Despite the distinctions between the two species in terms of morphology, habitat preferences, mating systems and life history traits, most studies have detected little genetic differentiation or substantial allele sharing between species relative to the high degree of polymorphism within the species (Second ; Barbier ; Cai et al .…”

“…Oryza rufipogon Griff. and Oryza nivara Sharma et Shastry are two sister species or ecotypes that are most closely related to Asian cultivated rice; these species represent a unique model for the study of ecological speciation (Grillo et al 2009;Zheng & Ge 2010;Banaticla-Hilario et al 2013b;Huang et al 2013). The perennial O. rufipogon is widely distributed throughout southern China, South and South-East Asia, Papua New Guinea and northern Australia and is characterized by photoperiod sensitivity, predominate cross-fertilization and a preference for habitats with year-round water.…”