Morphological investigations were conducted on four taxa of the Stipa tianschanica complex occurring in Central Asia. The main objective of the study was to survey the micromorphological characters of the lemma in the complex by means of scanning electron microscopy (SEM) in order to assess their taxonomic value and to compare the variation with the recent treatment based on macromorphological traits. The main lemma epidermal characters studied included the frequency, shape and distribution of long cells, hooks, prickles and macrohairs. A principal component analysis of macromorphological traits revealed correlations with micromorphological characters and with the geographical distribution of the specimens examined. On this basis, three species, namely S. tianschanica, S. klemenzii and S. austromongolica, and one additional subspecies, S. tianschanica subsp. gobica, are recognized in Central Asia. Stipa austromongolica is described here as a species new to science. The lectotype for S. tianschanica is designated here as well. Morphological descriptions, synonyms, distribution maps, citations of representative specimens and an identification key are provided.
