Molecular phylogenetics and its role for evaluating biodiversity and classification of the orchid subtribe Aeridinae
Topik Hidayat, Universitas Pendidikan Indonesia (UPI)
Phylogenetic analyses to examine relationships among genera of orchid subtribe Aeridinae were carried out using two DNA sequence data sets derived from matK, the maturase coding gene located in an intron of the plastid gene trnK, and the internal transcribed spacer region of 18S–26S nuclear ribosomal DNA. These analyses, specifically, investigated phylogenetic relationships among genera in the subtribe, the congruence between previous classifications of the subtribe and the phylogenetic relationships inferred from the molecular data, and evolutionary trends of taxonomically important characters of orchid group, such as pollinia, a spurred lip, a column foot, stipe and viscidium, and length of stem. Parsimony analyses employing 111 species consisting of 79 genera of subtribe Aeridinae (sampled from Asia and Australia) and three genera of outgroup revealed several insights. The analyses showed that subtribe Aeridinae are monophyletic and four major clades with 11 subclades can be recognized. Repeated evolution of several characters such as pollinium number, presence or absence of column foot, spur length, and shape of stipe and viscidium is confirmed in this study. This indicates limited utility of these characters in determining major relationship within subtribe Aeridinae. Contrariwise, length of the stem appears to be a good character in determining major relationships of subtribe Aeridinae. Evolution of presence or absence of column foot, spur length, and shape of stipe and viscidium may correlate with shifts of pollinators. The results also support hypothesis that subtribe Aeridinae evolved in Asian region and subsequently spread out to Australasian region and other continents. In light of these findings, a tentative revised classification scheme of subtribe Aeridinae is discussed.
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