A Diploids-First Approach to Species Delimitation and Interpreting Polyploid Evolution in the Fern Genus Astrolepis (Pteridaceae)
Polyploidy presents a challenge to those wishing to delimit the species within a group and reconstruct the phylogenetic relationships among these taxa. A clear understanding of the tree-like relationships among the diploid species can provide a framework upon which to reconstruct the
reticulate events that gave rise to the polyploid lineages. In this study we apply this “diploids-first” strategy to the fern genus Astrolepis (Pteridaceae). Diploids are identified using the number of spores per sporangium and spore size. Analyses of plastid and low-copy
nuclear sequence data provide well-supported estimates of phylogenetic relationships, including strong evidence for two morphologically distinctive diploid lineages not recognized in recent treatments. One of these corresponds to the type of Notholaena deltoidea, a species that has
not been recognized in any modern treatment of Astrolepis. This species is resurrected here as the new combination
Astrolepis deltoidea
. The second novel lineage is that of a diploid initially hypothesized to exist by molecular and morphological characteristics of several
established Astrolepis allopolyploids. This previously missing diploid species is described here as
Astrolepis obscura
.
Keywords: ASTROLEPIS; GAPCP; MISSING DIPLOID; POLYPLOIDY; TRNG-TRNR; “DIPLOIDS-FIRST”
Document Type: Regular Paper
Publication date: 01 April 2010
- Systematic Botany is the scientific journal of the American Society of Plant Taxonomists and publishes four issues per year.
2011 Impact Factor: 1.517
2011 ISI Journal Citation Reports® Rankings: 87/190 - Plant Sciences
34/45 - Evolutionary Biology - Editorial Board
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