Morpho-anatomical characterization of stilt mangroves (Rhizophora spp.) in Pagaspas Bay, Calatagan, Batangas, Philippines
2010
Endonela, L.E., Philippines Univ. Los Baños, College, Laguna (Philippines)
The study aims to develop a descriptor list for Rhizophora and to asses phenotypic diversity and elucidate the taxonomic interrelationships among Rhizophora species. The characterization descriptors for Rhizophora spp. was composed of 63 vegetative (25) and reproductive (38) morpho-anatomical characters. The presence of all Philippine Rhizophora spp. in Pagaspas Bay, Calatagan, Batangas, namely: R. apiculata, R. mucronata, R. stylosa and putative hybrid R. x lamarckii was first reported in this study. The Rhizophora species differ greatly in stipule, leaf, stomata, bracheole, sepal, petal, stigma, style, fruit and hypocotyl morpho-anatomical traits. R. apiculata was extremely different in terms of overall appearance showing wide phenotypic variation. The average standardized Shannon-Weaver diversity index (H'= 0.77) indicated that there is a significant genetic base present in Rhizophora species. Clustering of the distance matrix obtained from morpho-anatomical characterization data using Unweighted Pair Group Method Arithmetic Average(UPGMA) revealed a close similarity among R. mucronata, R. stylosa and R. x lamarckii. This showed that R. mucronata and R. stylosa are the possible parents of the putative hybrid R. x lamarckii, while R. apiculata formed a separate distinct group. Pollen fertility determined using staining and in vitro germination techniques showed high percent pollen viability in R. apiculata, R. mucronata and R. stylosa but zero in putative hybrid. Very low percent normal tetrad information contributed to a very high percentage of non-viable pollen resulting to complete sterility in the putative hybrid R. x lamarckii.
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